Article

Phenology and wood density of plants growing in the semi-arid region of Northeastern Brazil

November 2010
Journal of Arid Environments 74(11):1363–1373

November 2010
74(11):1363–1373

DOI:10.1016/j.jaridenv.2010.05.009

Authors:

André Luiz Alves de Lima

Universidade Federal Rural de Pernambuco

Maria Rodal

Universidade Federal Rural de Pernambuco

Nineteen woody species growing in the semi-arid region of northeastern Brazil were examined to evaluate the relationship between wood density and their vegetative and reproductive phenophases. Wood density varied between 0.29 g/cm3 and 0.83 g/cm3, and these values were inversely related to the quantity of water stored at saturation. The six species that initiated vegetative and/or reproductive phenophases during the dry season had low wood densities (<0.55 g/cm3) and were able to store large quantities of water (110–271% of the dry weight of the wood). Leaf fall in these species occurred during the transition period between the rainy and the dry season, and it occurred earlier than in species with denser wood. Leaf flush among low wood density species was positively related to the photoperiod. Species with high wood densities, on the other hand, were strongly dependent on rainfall for leaf flush, flowering, and fruiting, as they are able to store only limited quantities of water in their trunks; leaf fall in these species occurred during the dry season. These results point to a strong correlation between wood density and phenology among the species studied.

Divergent hydraulic strategies of two deciduous tree species to deal with drought in the Brazilian semi-arid region

Article

Full-text available

Mar 2024
TREES-STRUCT FUNCT

Key message The high-wood-density species displays greater water limitation tolerance, as it maintains leaf transpiration under drought conditions. Abstract The relationship between environmental conditions and plant hydraulic safety is essential to understand species’ strategies to minimize damage to their hydraulic structure yet maintain function. In the Brazilian semi-arid, the relationships between rainfall seasonality, hydraulic conductivity, wood density, stomatal conductance, and phenology in different species still needs to be clarified. To better understand these relationships, we selected two deciduous trees species with contrasting wood density: (1) Commiphora leptophloeos (Mart.) J.B. Gillett (low wood density) and (2) Cenostigma pyramidale (Tul.) E. Gagnon & G. P. Lewis (high wood density) from the Caatinga dry forest of northeast Brazil. We tracked monthly measurements of whole-tree hydraulic conductivity, leaf stomatal conductance, leaf transpiration rate, xylem water potential, and phenology. We found that the low-wood-density species had a higher whole-tree hydraulic conductivity and an early leaf flush and fall. In addition, lower leaf transpiration rate and higher water storage capacity maintained high xylem water potential and stomatal conductance values, especially in the rainy season. On the other hand, the high-wood-density species had a lower whole-tree hydraulic conductivity and higher leaf transpiration rate, even during the dry season. These results point to the divergent hydraulic strategies employed by each species, further suggesting opposing hydraulic safety pathways during drought.

Functional traits determine the vegetative phenology of woody species in riparian forest in semi-arid Brazil

Article

Full-text available

Aug 2022
PLANT ECOL

Relationships between phenological and morphophysiological traits of functional groups of woody species in riparian forests of semi-arid environments are little understood, especially regarding the representativeness of these groups in the community. This study aimed to evaluate the influence of the leaf and wood morphofunctional characteristics on the vegetative phenology of woody species in a riparian forest in the Brazilian semi-arid region and how these traits act in the distribution of species in functional groups. Vegetative phenology and leaf traits (specific leaf area, leaf area, leaf thickness, and leaf dry matter content), wood density, and amount of saturated water in the stem and their association with soil water availability, relative air humidity, precipitation, temperature, photoperiod, and vapor pressure deficit were evaluated. Cluster analysis showed three functional groups (n = 23): deciduous low wood density species (9%), deciduous high wood density species (48%), and non-deciduous species, which included semideciduous (17%) and evergreen species (26%). Deciduousness was positively related to specific leaf area and negatively related to leaf dry matter and leaf area. Deciduous and semideciduous species (55.1% and 7.5% of the individuals in the community, respectively) showed a strong dependence on abiotic factors linked to precipitation and temperature, while the evergreen species showed a strong dependence on the vapor pressure deficit to trigger their phenophases. We concluded that the studied functional traits act on the leaf habit, which is essential to understand how the phenology is projected within functional groups.

Functional groups of woody species in riparian forest in the Brazilian semi-arid region: phenological and morphophysiological evidence

Preprint

Full-text available

Dec 2021

Relationships between morphophysiological and phenological traits of functional groups of tree species from seasonally dry tropical environments are reasonably known. However, such information is scarce for riparian forests in semi-arid environments, especially regarding the representativeness of these groups in the community. This study aimed to evaluate the relationship of the morphofunctional characteristics of leaves and stem in the identification of functional groups and how these traits vary in these groups in a riparian forest in the Brazilian semi-arid region. Traits of leaf phenology (specific leaf area, leaf area, leaf thickness, and leaf dry matter content), wood density, and amount of saturated water in the stem and their association with soil water availability, relative air humidity, precipitation, temperature, photoperiod, and vapor pressure deficit were evaluated in 23 species. Cluster analysis showed three functional groups: deciduous low wood density species (9%), deciduous high wood density species (48%), and non-deciduous species, which included semideciduous (17%) and evergreen species (26%). Deciduousness was positively related to specific leaf area and negatively related to leaf dry matter and leaf area. Deciduous and semideciduous species (55.1% and 7.5% of the individuals in the community, respectively) showed a strong dependence on abiotic factors linked to precipitation and temperature, while the evergreen species showed a strong dependence on the vapor pressure deficit to trigger their phenophases. It was evident that the studied functional traits influenced the leaf habit, which is essential to determine the abundance of functional groups of woody species from riparian forests in the semi-arid region.

Simulating Rainfall Interception by Caatinga Vegetation Using the Gash Model Parametrized on Daily and Seasonal Bases

Article

Full-text available

Sep 2021

Rainfall partitioning by trees is an important hydrological process in the contexts of water resource management and climate change. It becomes even more complex where vegetation is sparse and in vulnerable natural systems, such as the Caatinga domain. Rainfall interception modelling allows extrapolating experimental results both in time and space, helping to better understand this hydrological process and contributing as a prediction tool for forest managers. In this work, the Gash model was applied in two ways of parameterization. One was the parameterization on a daily basis and another on a seasonal basis. They were validated, improving the description of rainfall partitioning by tree species of Caatinga dry tropical forest already reported in the scientific literature and allowing a detailed evaluation of the influence of rainfall depth and event intensity on rainfall partitioning associated with these species. Very small (0.0–5.0 mm) and low-intensity (0–2.5 mm h−1) events were significantly more frequent during the dry season. Both model approaches resulted in good predictions, with absence of constant and systematic errors during simulations. The sparse Gash model parametrized on a daily basis performed slightly better, reaching maximum cumulative mean error of 9.8%, while, for the seasonal parametrization, this value was 11.5%. Seasonal model predictions were also the most sensitive to canopy and climatic parameters.

Environmental Drivers of Water Use for Caatinga Woody Plant Species: Combining Remote Sensing Phenology and Sap Flow Measurements

Article

Full-text available

Dec 2020

We investigated the water use of Caatinga vegetation, the largest seasonally dry forest in South America. We identified and analysed the environmental phenological drivers in woody species and their relationship with transpiration. To monitor the phenological evolution, we used remote sensing indices at different spatial and temporal scales: normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI), and green chromatic coordinate (GCC). To represent the phenology, we used the GCC extracted from in-situ automated digital camera images; indices calculated based on sensors included NDVI, SAVI and GCC from Sentinel-2A and B satellites images, and NDVI products MYD13Q1 and MOD13Q1 from a moderate-resolution imaging spectroradiometer (MODIS). Environmental drivers included continuously monitored rainfall, air temperature, soil moisture, net radiation, and vapour pressure deficit. To monitor soil water status and vegetation water use, we installed soil moisture sensors along three soil profiles and sap flow sensors for five plant species. Our study demonstrated that the near-surface GCC data played an important role in permitting individual monitoring of species, whereas the species’ sap flow data correlated better with NDVI, SAVI, and GCC than with species’ near-surface GCC. The wood density appeared to affect the transpiration cessation times in the dry season, given that species with the lowest wood density reach negligible values of transpiration earlier in the season than those with high woody density. Our results show that soil water availability was the main limiting factor for transpiration during more than 80% of the year, and that both the phenological response and water use are directly related to water availability when relative saturation of the soil profile fell below 0.25.

Does leaf flushing in the dry season affect leaf traits and herbivory in a tropical dry forest?

Article

Full-text available

Dec 2020
NATURWISSENSCHAFTEN

In tropical dry forests (TDFs), stem-succulent deciduous species produce leaves during the dry season which coincides with the period of lower herbivore abundance. In this study, we evaluated the effects of abiotic factors (precipitation and day length) on the vegetative phenology of three stem-succulent deciduous species (Cochlospermum vitifolium, Commiphora leptophloeos, and Manihot anomala) during 2 years. In addition, we compared leaf damage by herbivores and leaf defensive traits (specific leaf area, thickness, and content of phenolic compounds) on leaf cohorts produced before and during the rainy season by these stem-succulent deciduous species. We also evaluated herbivory and defensive traits on leaves produced during the rainy season by 14 non-succulent deciduous species. There was a positive effect of precipitation and day length on the amount of green leaves exhibited by the three stem-succulent species. The leaf cohort produced during the dry season by stem-succulent species showed lower leaf damage and content of phenolic compounds than the cohort produced during the rainy season by the same species and by non-succulent deciduous species. Leaf damage was only affected (positively) by the content of phenolic compounds, suggesting the production of induced defenses during leaf expansion. In general, herbivory levels were low in this study (0.57–6.37%) when compared with other TDFs, suggesting that a scape from herbivores due to anticipated leaf production is a weak selective force affecting plant fitness. These variations in leaf traits are mostly related to contrasting water conservation strategies among phenological groups. Further studies should evaluate other defensive and nutritional traits, as well as their variations along the leaf lifespan, to unravel herbivory patterns in TDFs.

Leaf deciduousness and flowering of woody caatinga species

Article

Full-text available

Dec 2020

We determined the distribution (FDI), duration (FDU), and peak (FPE) of flowering in woody deciduous (DE) and evergreen (EV) species of the Caatinga with available data in the literature. Possible relations were established between leaf persistence and reproductive phenology throughout the year. The FDI indicated the relative number of species bearing flowers in each month, and the FDU denoted the number of months each species showed flowers. We defined the FPE as the four consecutive months with the highest number of species in flower. DE and EV did not show significant differences in FDI and FDU, probably due to the inability to sustain reproductive and vegetative annexes of woody axes simultaneously during the dry period. Some DE species showed flowering during the dry period in a crown free of leaves. EV flowering occurred outside the dry period. Flowering during the dry season in DE may happen due to water accumulated inside the plant body. FPE in EV during the transition between dry-rainy periods may indicate the ability to capture the first rain from all the plant body surface, covering the hydric demand of full foliage and folded reproductive buds anticipating the flowering in DE. This resulted in different values of FPE between DE and EV.

Vegetative and reproductive phenology in seasonal climate vegetation: phenological complementarity between woody and herbaceous plants in the Brazilian Chaco

Article

May 2024
FLORA

Plant growth and reproduction patterns may be closely associated with environmental seasonality, but the high diversity of plant strategies has revealed complex phenological patterns. Here, we evaluate the occurrence, duration, and seasonality of vegetative and reproductive phenophases of the Brazilian Chaco vegetation. In addition, we summarize the results of a systematic literature review about the phenology of herbaceous and woody plants in different types of seasonal vegetation in the South American Dry Diagonal. Woody plants have a high intense leaf fall and low leaf flush during the dry season in the Brazilian Chaco, whereas in herbaceous plants these phenophases have more fluctuations. In both types, flowering and fruiting are continuous, not uniform, and mainly concentrate during the rainy season. However, woody species present two intensity peaks independent of rainfall, mean temperature, photoperiod, or soil water availability. In turn, in herbaceous species, flowering and fruiting responded to local climatic variables and photoperiod, presenting a peak of intensity during the rainy season. The rainy season plays an important role in plant growth and reproduction in seasonal climates around the world, mainly due to the energetic demand for plants. Like other vegetation types with seasonal climates, particularly in the South American Dry Diagonal, the Brazilian Chaco presents a wide range of phenological patterns, with generally different patterns between woody and herbaceous species. Community-level phenological studies conducted in areas with a seasonal climate have globally focused only on reproduction in relation to vegetative phenology, mostly ignoring herbaceous flora. Here, we emphasize that the phenological complementarity between the woody and herbaceous components is of great importance in maintaining the availability of resources.

Contrasting water use strategies revealed by species-specific transpiration dynamics in the Caatinga dry forest

Article

Full-text available

Nov 2023
TREE PHYSIOL

In forest ecosystems, transpiration (T) patterns are important for quantifying water and carbon fluxes and are major factors in predicting ecosystem change. Seasonal changes in rainfall and soil water content can alter the sensitivity of sap flux density to daily variations in vapor pressure deficit (VPD). This sensitivity is species-specific and is thought to be related to hydraulic strategies. The aim of this work is to better understand how the sap flux density of species with low versus high wood density differ in their sensitivity to VPD and soil water content and how potentially opposing water-use strategies influence T dynamics, and ultimately, correlations to evapotranspiration (ET). We use hysteresis area analysis to quantify the sensitivity of species-specific sap flux density to changes in the VPD, breakpoint-based models to determine the soil water content threshold instigating a T response and multiscalar wavelet coherency to correlate T to ET. We found that low wood density Commiphora leptophloeos (Mart.) Gillett had a more dynamic T pattern, a greater sensitivity to VPD at high soil water content, required a higher soil water content threshold for this sensitivity to be apparent, and had a significant coherency correlation with ET at daily to monthly timescales. This behavior is consistent with a drought avoidance strategy. High wood density Cenostigma pyramidale (Tul.) E. Gagnon & G. P. Lewis, conversely, had a more stable T pattern, responded to VPD across a range of soil water content, tolerated a lower soil water content threshold to T, and had a significant coherency correlation with ET at weekly timescales. This behavior is consistent with a drought-tolerant strategy. We build on previous research to show that these species have contrasting water-use strategies that should be considered in large-scale modeling efforts.

Nurse-target functional match explains plant facilitation strength

Article

Apr 2022
FLORA

Functional trait combinations underlie assembly rules of plant communities. In harsh environments, facilitation is widespread but its strength varies greatly between pairs of interacting nurse-target plants. Here, we investigated whether functional traits of potential nurse and target species can jointly predict the sign and strength of their interactions. In order to estimate the facilitation strength for 60 nurse-target species combinations, we conducted field experiments in a seasonally dry tropical forest. We estimated eight key functional traits (canopy diameter, leaf C:N, leaf ∂C13, specific leaf area, number of months without leaves, wood density, hydraulic diameter and root volume) for 20 potential mature nurse species established under field conditions. For three target species, four key functional traits were estimated for seedlings grown in greenhouse conditions (total dry biomass, plant water content, root:shoot ratio, and apical growth rate). Our results showed that facilitation strength can be explained by the interaction between nurse and target traits. Facilitation increased when low SLA nurses interacted with targets investing in apical growth, thus acquisitive targets are benefited by the greater availability of resources left by conservative nurses. Facilitation also increased when nurses with lower values of leaf ∂C13 interacted with high root:shoot ratio targets, so early release of light and soil resources due to nurse earlier leaf loss benefits drought resistant targets. Besides, root volume of the nurse promoted facilitation, probably due to improvements on soil conditions. Functional trait match can shed light on plant community assembly rules and help promote ecosystem restoration and management.

Interplay of environmental cues and wood density in the vegetative and reproductive phenology of seasonally dry tropical forest trees

Article

Feb 2022
BIOTROPICA

The great phenological diversification characteristic of seasonally dry tropical forests (SDTF) suggests that these patterns result from a complex interplay between exogenous (e.g., climatic) and endogenous (e.g., morphological, physiological, anatomical) factors. Based on the well‐established relationships of wood density with water‐storing capacity and cavitation vulnerability in woody plants, we hypothesized differential vegetative and reproductive phenological responses to environmental cues for hardwood and softwood species. To test this hypothesis, we compared phenological patterns of pairs of conspecific populations of 10 species differing in wood density, occurring in two localities with slightly different climatic regimes, and evaluated the influence of three environmental variables (rainfall, photoperiod, and temperature) on them. Our results, based on the assessment of the overlap of the phenological curves of conspecific populations occurring in different sites and on linear modeling, showed different effects of the environmental factors on phenophase attributes, depending on wood density of the study species, thus supporting our hypothesis. Leaf out in softwood species took place in the dry season, they shed the foliage at the first signs of drought, and once leafless, they flowered and fruited shortly after. By contrast, hardwood species bore leaves and flowers in the rainy season, shed their leaves several months after the rain ceased, and produced fruits during the dry season. We conclude that the role of environmental variables in cueing growth and reproduction cycles in SDTF tree species is interrelated with their wood density, a key endogenous factor crucially linked to plant hydraulics in these water‐limited ecosystems. Abstract in Spanish is available with online material.

Phenological dynamics of Croton heliotropiifolius populations in a savanna/caatinga gradient, Chapada Diamantina, Brazil

Article

Full-text available

Jan 2021

The relationship between phenology and environmental factors is critical to understanding population dynamics in environmental gradients. We evaluated phenological variations in Croton heliotropiifolius Kunth in sites with contrasting water resource availability in caatinga, cerrado/caatinga transition, and cerrado in the Chapada Diamantina, Brazil. The phenophases of 81 individuals (n = 27 individuals/area) were recorded monthly for 12 months. Multiple regression, Spearman correlation, circular statistics, Shannon-Wiener diversity, and Morisita-Horn indices were used to test relationships between phenophases and abiotic factors, phenological seasonality, diversity, and similarities between the three populations. The vegetative behaviors in the study sites were distinct in terms of their intensity, seasonality, and synchrony; but reproductive phenophases maintained similar characteristics. Phenological events were positively related to rainfall and soil water availability. C. heliotropiifolius populations exhibited high levels of vegetative phenological diversity, except in the caatinga during the dry season. Reproductive phenological diversity varied along the studied period in the three sites, with higher reproductive than vegetative similarities among populations. Differences in soil types and rainfall volumes in the dry season, even at small distances, therefore make the savanna/caatinga gradient a suitable model for investigating phenological responses related to plant eco-hydrological strategies in seasonally tropical dry ecosystems.

Spring phenological variability promoted by topography and vegetation assembly processes in a temperate forest landscape

Article

Oct 2021
AGR FOREST METEOROL

Plant phenological processes significantly impact ecosystem function and services across multiple ecological scales and are widely viewed to be among the most sensitive indicators of global environmental change. Remote sensing has crucially expanded our understanding of phenological variability. Yet, we continue to lack a complete mechanistic understanding of phenology and its variability and drivers, which is important to the development of predictive models, especially under continued environmental change. We combined field inventories and Land Surface Phenology (LSP) approaches, using 36 years of Landsat phenological observations, to characterize the degree to which long-term spring greenup patterns are shaped by topography, vegetation, and topographically structured vegetation assembly processes within a dissected forest landscape in southeastern Ohio. We found temporal and spatial variability among the field samples where greenup patterns displayed rapid change (18 total days) over relatively short distances (<1 km). Slope position explained the most variation (35%), where the bases of hills displayed the latest timing in spring greenup. However, we found that differences in terrain aspect and slope influenced canopy diversity, height, and composition of forest stands, influencing plant community processes that support heterogeneity in spring leaf-out timing. Understanding how forest phenology is shaped by direct and often complex interacting processes that influence the distribution of species assemblages supports new insight into phenological variability and, importantly, the management of forest ecosystems facing continued environmental change.

Plant functional types broadly describe water use strategies in the Caatinga, a seasonally dry tropical forest in northeast Brazil

Article

Full-text available

Aug 2021

• In seasonally dry tropical forests, plant functional type can be classified as deciduous low wood density, deciduous high wood density, or evergreen high wood density species. While deciduousness is often associated with drought-avoidance and low wood density is often associated with tissue water storage, the degree to which these functional types may correspond to diverging and unique water use strategies has not been extensively tested. • We examined (a) tolerance to water stress, measured by predawn and mid-day leaf water potential; (b) water use efficiency, measured via foliar δ¹³C; and (c) access to soil water, measured via stem water δ¹⁸O. • We found that deciduous low wood density species maintain high leaf water potential and low water use efficiency. Deciduous high wood density species have lower leaf water potential and variable water use efficiency. Both groups rely on shallow soil water. Evergreen high wood density species have low leaf water potential, higher water use efficiency, and access alternative water sources. These findings indicate that deciduous low wood density species are drought avoiders, with a specialized strategy for storing root and stem water. Deciduous high wood density species are moderately drought tolerant, and evergreen high wood density species are the most drought tolerant group. • Synthesis. Our results broadly support the plant functional type framework as a way to understand water use strategies, but also highlight species-level differences.

The importance of wood density in determining the phenology of tree species in a coastal rain forest

Article

Apr 2021

The phenology of tree species in tropical dry forests is related to a well‐characterized interaction between functional traits (e.g., wood density) and climatic seasonality (e.g., drought stress), but the existence of these relationships in tropical wet forests is largely unknown. For 12 months, we monitored the vegetative and reproductive phases of 281 individuals of 46 tree species in a coastal rain forest in Northeastern Brazil. We hypothesized that wood density and related tissue water storage would reliably distinguish phenological groups of trees, and that leaf shedding, flushing, and flowering in high wood density species would be closely related to rainfall, due to low tissue water storage capacity in these species. By contrast, we predicted leaf unfolding and flowering of low wood density species would depend exclusively on photoperiod. As predicted, wood density and saturated water content were inversely correlated, and species with either high or low wood density had distinct phenological patterns and levels of synchrony within species. Abiotic variables were not strongly associated with phenological events. Phenophases of leaf unfolding, flowering, and fruiting occurred earlier in low wood density species than in high wood density species, possibly indicating an adaptive strategy for preemptive resource capture. Abstract in Portuguese is available with online material.

Relationship between shoot and root of woody species of phenological functional groups of dry forest

Article

Full-text available

Dec 2020

Water availability in arid and semi-arid environments is the most limiting environmental factor for the development of plants, which use different mechanisms to capture the water from the soil. The objective of this work was to evaluate if there is differential allocation of resources between root and shoot of woody species of Brazilian dry forest and its relationship with the phenological functional groups of known adult woody: evergreen (EG), deciduous high density woody species (DHDW) and deciduous low density woody species (DLDW). The experiment was carried out in a greenhouse with a duration of six months, with plans submitted to two treatments: controlled irrigation (CI) and abundant irrigation (AI). Results showed that there was no interaction between phenological groups and applied treatments. However, the treatment with AI presented values of total biomass higher than those presented by CI. Fine root biomass was the only variable that did not differ between abundant irrigation and controlled irrigation. DLDW plants had higher root: shoot ratio compared to DHDW and EG. DLDW presented a differentiated strategy, being an indicative factor of these groups high thick root biomass, followed by low fine root biomass, with lower proportion of leaf biomass, and higher total biomass. These results show that CI reduces the development of seedlings in the groups and hence they invest in fine-root biomass. DLDW species presented higher investment in root biomass than in shoot, in addition to higher values of total biomass and specific leaf area. Key words: water availability, Brazilian dry forest, phenological functional groups, aerial part, root of seedlings.

Linkage between species traits and plant phenology in an alpine meadow

Article

Full-text available

Feb 2021
OECOLOGIA

Plant phenology differs largely among coexisting species within communities that share similar habitat conditions. However, the factors explaining such phenological diversity of plants have not been fully investigated. We hypothesize that species traits, including leaf mass per area (LMA), seed mass, stem tissue mass density (STD), maximum plant height (Hmax), and relative growth rate in height (RGRH), explain variation in plant phenology, and tested this hypothesis in an alpine meadow. Results showed that both LMA and STD were positively correlated with the onset (i.e., beginning) and offset (i.e., ending) times of the four life history events including two reproductive events (flowering and fruiting) and two vegetative events (leafing and senescing). In contrast, RGRH was negatively correlated with the four life phenological events. Moreover, Hmax was positively correlated with reproductive events but not with vegetative events. However, none of the eight phenological events was associated with seed size. In addition, the combination of LMA and STD accounted for 50% of the variation in plant phenologies. Phylogenetic generalized least squares analysis showed plant phylogeny weakened the relationships between species traits vs. phenologies. Phylogeny significantly regulated the variation in the ending but not the beginning of phenologies. Our results indicate that species traits are robust indicators for plant phenologies and can be used to explain the diversity of plant phenologies among co-occurring herbaceous species in grasslands. The findings highlight the important role of the combination of and trade-offs between functional traits in determing plant phenology diversity in the alpine meadow.

Deterioro y preservación de maderas mediante el uso de preservadores naturales de potencial interés en Brasil

Article

Full-text available

Dec 2020

In this review article, the main deterioration processes and uses of natural preservatives in wood are discussed, in particular in Brazil, taking into account its economic relevance in Latin America. It contextualizes the problem of protection and chemical degradation of wood, topics of interest not only in Brazil but also in other countries. In addition, the use of novel products is discussed, such as neem oil, castor oil, pepper extracts, tannins, tall oil, linseed oil, oils extracted from native timbers, chitosan and others. In terms of solutions, more studies are necessary in the field and modification of formulations with fixation agents, biocides, antioxidants, additives and others. In addition, the legal aspects of commercialization for new formulations in countries rich in natural resources, though underdeveloped, must be taken into account.

Fenologia da vegetação arbórea em remanescente de Mata Atlântica no estado da Paraíba

Article

Full-text available

Nov 2023

Esse estudo foi desenvolvido visando o acompanhamento fenológico dos padrões vegetativos e reprodutivos de espécies arbóreas em um fragmento de Mata Atlântica na RPPN Gargaú, Santa Rita-PB. As observações fenológicas foram realizadas mensalmente de outubro de 2010 a setembro de 2011. Para a seleção dos indivíduos foi montado uma parcela de 100m2 e selecionado os indivíduos com Circunferência à Altura do Peito (CAP) ≥ 63 cm. O número total de indivíduos amostrados foi de 151, distribuídos em 16 espécies de 14 famílias. Foi observado picos de 76% dos indivíduos em brotamento e 100% com queda foliar, para as fenofases reprodutivas 56% dos indivíduos foram observados em floração; 44% em frutificação. A espécie que apresentou maior período de frutificação foi Protium heptaphyllum, com duração de cinco meses, de dezembro a abril, correspondendo ao final do período seco a início do chuvoso. Padrão encontrado para todas as espécies zoocóricas. As espécies foram caracterizadas quanto a sua dispersão, 11 são zoocóricas (68%), duas são anemocóricas (12%) e uma é autocórica (6%). A floresta tropical se mostra muito sazonal e bastante influenciada pelo clima e precipitação local, principalmente pelas fenofases de brotamento e floração.

Phenological dynamics of four populations of Handroanthus spongiosus in seasonally dry tropical forest in Brazil

Article

Aug 2023
FLORA

The scarcity of phenological studies based on different populations of tropical forest trees limits seed management and collection for reforestation efforts. Precipitation is the primary factor driving tropical plant phenology in seasonal environments, although other environmental variables and plant traits may be associated. We examined the seasonality, synchrony, and intensities of the vegetative and reproductive phenophases of four populations of Handroanthus spongiosus, an endangered species, under similar climate regimes in a seasonally dry tropical forest, in northeastern Brazil. We expected to observe some divergence in the phenologies of the populations related to distinct functional traits selected for by differences in rainfall and soil properties. Mature trees (n = 87) were monitored during a three-year period. Seasonality was examined using circular statistics, and the influences of environmental variables on phenophases were investigated using generalized additive models. Variations in intensities and activity indices were identified among the different populations. Vegetative phenophases were seasonal, driven by precipitation and photoperiod, with leaf longevity of up to 7 months; budding peaked in February-March, while leaf fall peaked in April and October. The reproductive phenophases were found to be seasonal, during the rainy season (November to April), influenced by temperature and photoperiod. The slight divergences noted among the phenological behaviors of the populations were related to distinct functional traits (e.g., tree height, stem diameter) selected for by differences in certain environmental variables (rainfall volumes and soil properties). Given ongoing global climate changes, increases in leaf fall and reductions of flowering intensity, as verified here, will likely be observed.

Rates of Stemwood Carbon Accumulation Are Linked to Hydroclimate Variability in Mexican Conifers

Article

Full-text available

Jul 2023

Evapotranspiration demand has increased rapidly as temperatures have risen, affecting forest productivity. Consequently, carbon (C) uptake by forests is being modified; therefore, a more refined knowledge of the relationships between C capture and hydroclimate variability is required, particularly in drought-prone regions. In this study, we analyzed the relationships between climate and C capture as stemwood through the dendroecological analyses of radial growth in 15 conifer species distributed along a broad bioclimatic gradient in Mexico. The C content was calculated using densitometry data; correlations and mixed models were then used to determine the influence of climatic variables (precipitation, mean maximum and minimum temperatures, SPEI drought index) on tree growth. Each species showed specific responses to the climate with Taxodium mucronatum being the most responsive species. Both precipitation and maximum temperature best explained changes in C capture, with minimum temperature and SPEI playing secondary roles. The winter before the growth period was the most important season for C capture, particularly through positive responses to wet-cool conditions. However, the climatic influences of the current fall and summer were also notable. Seasonal climatic influences have implications for C uptake and forest productivity in the face of the severe droughts that repeatedly affect the study region.

STEEP: A remotely-sensed energy balance model for evapotranspiration estimation in seasonally dry tropical forests

Article

Apr 2023
AGR FOREST METEOROL

The dynamics of cambial activity related to photoperiod, temperature, and precipitation in two Cordia species of the Brazilian semiarid

Article

Full-text available

Feb 2023
FLORA

Highlights • Small variation on photoperiod has an effect on cambial activity • Water availability drives cambial activity and temperature is a limiting factor • High temperatures do not favour increased growth of tropical semiarid plants Abstract In the seasonally dry tropical regions around the globe, water availability is the most limiting factor for plant growth and affects cambial activity. However, identification of the other climatic factors that regulate cambial activity is necessary to understand the growth of tropical semiarid species. Here we studied two congeneric species, Cordia oncocalyx and C. bicolor, to investigate the cambial activity response to environmental factors. These species occur in the Brazilian semiarid region, in areas that contrast in humidity. Cambial activity was quantified in both species by counting the number of cambial cell layers and the relationships between cambial activity and abiotic factors were investigated using a generalized linear mixed model (GLMM). Despite the modest variation in photoperiod in seasonally dry tropical regions, cambial activity significantly increased in response to longer days. We found that cambial activation depended on the milder average temperature of the wet season, and the cambial cell division rate was driven by pulse water availability. Also, the increase of temperature is a limiting factor for the cambial activity, which may represent limitation of plant growth due to climate change.

Functional traits above and below ground allow species with distinct ecological strategies to coexist in the largest seasonally dry tropical forest in the Americas

Article

Full-text available

Oct 2022

Plant functional strategies are well-established for low- and high-stress environments, such as rainforests and deserts. However, in environments with low- and high-stress level fluctuation within years, the relationship between plant functional strategies and their spatial distribution is still poorly understood. We aimed to answer: what are the relationships between above- and below-ground traits in the largest seasonally dry tropical forest in the Americas? Do the studied species form detectable groups from the functional perspective? If detectable, do functional groups present distinct spatial distributions across the domain, mediated by spatial heterogeneity of aridity? We sampled a range of 16 above- and below-ground traits from the 20 most common native tree species. We performed a PCA to understand the species' main coordinated trade-offs, a k-mean analysis to test for functional groups, and a Ripley's-K analysis followed by a GLS model to test spatial functional groups distribution through the aridity gradient. We found five coordinated trade-offs representing different aspects of the conservative-acquisitive strategy continuum. Drought-tolerance and avoidance mechanisms seem linked to the conservative-acquisitive gradient, where water storage is positively correlated with acquisitive strategies. Different from other seasonally dry regions, acquisitive strategies are not limited by aridity. The presence of short-term water storage traits might buffer rainfall fluctuations, allowing acquisitive species to occupy more arid regions. This study sheds new light on the functional complexity of species from Americas seasonally dry tropical forests, for the first time including the relationship of its below- and above-ground traits.

Steep: A Remotely-Sensed Energy Balance Model for Evapotranspiration Estimation in Seasonally Dry Tropical Forests

Article

Jan 2022

Wood Nutrient-Water-Density Linkages Are Influenced by Both Species and Environment

Article

Full-text available

Apr 2022

Tropical trees store a large amount of nutrients in their woody tissues, thus triggering the question of what the functional association of these elements with other wood traits is. Given the osmotic activity of mineral elements such as potassium, sodium, and calcium, these elements should be strong candidates in mediating the water storing capacity in tropical trees. We investigated the role of wood nutrients in facilitating wood water storage in trees by using branch samples from 48 tropical tree species in South America and examined their associations with wood density (ρ). Wood density varied from 316 kg/m³ in Peru plots, where the soil nutrient status is relatively higher, to 908 kg/m³ in Brazil plots, where the nutrient availability is lower. Phosphorus content in wood varied significantly between plots with lowest values found in French Guiana (1.2 mol/m³) and plots with highest values found in Peru (43.6 mol/m³). Conversely, potassium in woody tissues showed a significant cross-species variation with Minquartia guianensis in Brazil showing the lowest values (8.8 mol/m³) and with Neea divaricata in Peru having the highest values (114 mol/m³). We found that lower wood density trees store more water in their woody tissues with cations, especially potassium, having a positive association with water storage. Specific relationships between wood cation concentrations and stem water storage potential nevertheless depend on both species’ identity and growing location. Tropical trees with increased water storage capacity show lower wood density and have an increased reliance on cations to regulate this reservoir. Our study highlights that cations play a more important role in tropical tree water relations than has previously been thought, with potassium being particularly important.

Drought response strategies for deciduous species in the semiarid Caatinga derived from the interdependence of anatomical, phenological, and bio-hydraulic attributes

Article

Jan 2022
FLORA

Deciduous species from semiarid environments have different strategies for overcoming seasonal drought. However, these strategies are little explored for semiarid regions, particularly due to the lack of studies that integrate morpho-physiological mechanisms, including the vulnerability of the hydraulic system. In this work, we seek to integratively analyze the physiological, anatomical, hydraulic, phenological and wood density aspects of four deciduous species, representing opposite functional groups: 1) high wood density (HWD), 2) low wood density (LWD), from the Caatinga, a Brazilian semiarid region. The analyses covered leaf phenology, stomatal conductance, water potential, and chlorophyll content, as well as the anatomy and hydraulic architecture of branches and leaves. As predicted, the interrelationship between anatomy, physiology, and phenology was crucial to enhance the understanding of drought resistance strategies. LWD species tend to avoid drought, while HWD species tend to be more tolerant to it. LWD species showed an anticipated leaf fall to the dry season, in addition to a potential hydraulic conductivity 66.8% higher than HWD species, as well as a higher stomatal density (24.8%). However, LWD species were approximately 50% potentially more vulnerable than HWD species. The leaves of HWD species had gelatinous fibers surrounding the central rib, indicating traits of mechanical tolerance to dehydration. On the other hand, LWD species use preventive strategies to keep their water potential high during the dry period. These results highlight the importance of hydraulic architecture in the interrelationship of biological factors that determine the plant's drought stress performance as a function of the functional group.

Assessing the effects of urban green landscape on urban thermal environment dynamic in a semiarid city by integrated use of airborne data, satellite imagery and land surface model

Article

Mar 2022
INT J APPL EARTH OBS

The response of the urban thermal environment to green space landscapes has been studied previously, while its detailed pattern is insufficiently explored owing to the constraints of spatial and temporal resolution of available datasets. This study uses integrated Thermal Airborne Spectrographic Imager (TASI) data, Landsat TM/ETM and MODIS satellite imagery, and Noah land surface model output to investigate the effects of landscape pattern on the urban thermal environment across Shijiazhuang, China. The present study not merely proposes a generalized framework for the spatiotemporal analysis of urban thermal environment, but also affords several insights into the cooling effects related to urban green space landscapes in semiarid cities. Firstly, trees and lawns show a noticeable disparity in land surface temperature (LST) response to urban green landscape metrics, primarily due to the difference in cooling efficiency via evapotranspiration. This disparity can be explained further by the radiation-shading effect of trees. Secondly, analysis confirms that the composition of urban green space has a substantial impact on LST throughout summer. This pattern is largely stable for trees owing to the constant Bowen ratio, but they are altered for lawns. Conversely, the configurations of urban green space exhibit less impact on LST. These effects vary temporally in magnitude and can be enhanced notably in humid conditions. The lower correlation between the configuration metrics of urban green and LST has to do with the surface resistance alterations and additional cooling effects. Finally, consistent patterns of the impact of urban green space landscape metrics on LST are illustrated at different spatial scales and region sizes but greater effects are revealed for smaller analytical units, further confirming the impacts of urban green landscape on urban thermal environment.

Brazilian biomes distribution: Past and future

Article

Oct 2021
PALAEOGEOGR PALAEOCL

The Last Glacial Maximum (LGM, 26.5–19 ka) was marked by atmospheric cooling, in contrast to the current warming climate, which will probably continue in the coming decades, according to climate models projections. The LGM to pre-industrial transition provides an opportunity to test the vegetation response to a very large temperature change that can then be applied to project pre-industrial to end-of-century changes. In order to explore the changes in Brazilian biomes due to temperature change, we projected potential vegetation for both past and future scenarios. We compared biome projections with a compilation of 149 published LGM reconstructions of climate and vegetation within Brazil and adjacent areas. In addition, we evaluated the particular effects that changes in precipitation, temperature and CO2 had on vegetation by performing sensitivity experiments. Our results suggest that biomes in the western and central portions of the Amazon forest remained largely unchanged during the LGM mainly due to negative temperature anomalies, while a decrease in past precipitation was responsible for the shift from tropical evergreen forest to tropical seasonal forest in the eastern portion of the Amazon. These results are consistent with proxy reconstructions. LGM model projections and proxy reconstructions suggest expansion of grassland in the southern Brazilian highlands. Under future warming scenarios, biome changes are mostly forced by decreasing precipitation and increasing temperatures, which counteract potential biomass gain from the positive CO2 fertilization effect. Under future warming, our simulations show an expansion of Savanna/Cerrado and a reduction of tropical seasonal forest and Caatinga, with potential large impacts over biodiversity and regional climate.

Phenology of high-and low-density wood deciduous species responds differently to water supply in tropical semiarid regions

Article

Jul 2021

Although seasonal rainfall is the main factor regulating plant phenology in the dry tropics, some species flush and flower during the dry season. This apparent paradox was investigated in woody species in semiarid Brazil. A total of 500 mm of water was supplied to three 100 m 2 plots along 12 weeks from the beginning of the dry season, when the photoperiod was the shortest. Six deciduous high wood density species (HWD; ≥ 0.5 g cm − 3) that had flushed and flowered during the rainy season, had low water potentials (<− 3.5 MPa) and shed their leaves in the control plots during the dry season, while in the irrigated plots their water potential was higher (− 1.0 MPa), leaves were retained longer, and they flushed and/or flowered again. In both irrigated and control areas, four deciduous low wood density species (LWD) behaved similarly: they shed their leaves at the end of the wet season, maintained a relatively high-water potential (>− 0.3 MPa) throughout the dry season and flushed and flowered at the end of this season, when the photoperiod was greater than 12 h. We conclude that the phenophases of HWD species are regulated by water availability and those of LWD species by the photoperiod.

Evaluating single and multi-date Landsat classifications of land-cover in a seasonally dry tropical forest

Article

Apr 2021

Accurate information on the land cover is crucial for efficient monitoring and development of environmental studies in the Brazilian Caatinga forest. It is one of the largest and most biodiverse dry forests on the planet. Distinguishing different patterns of land cover through medium spatial-resolution remote sensing, such as the Landsat image series, is challenging to Caatinga due to heterogeneous land cover, complex climate-soil - vegetation interactions, and anthropogenic disturbance. Two remote sensing approaches have a high potential for accurate and efficient land-cover mapping in Caatinga: single and multi-date imagery. The heterogeneity of the land cover of this environment can contribute to a better performance of multispectral approaches, although it is usually applied for single-date images. In a land-cover mapping effort in Caatinga, the temporal factor gains relevance, and the use of time series can bring advantages, but, in general, this approach uses vegetation index, losing multispectral information. This manuscript assesses the accuracies and advantages of single-date multispectral and multi-date Normalized Difference Vegetation Index (NDVI) approaches in land-cover classification. Both approaches use the Random Forest method, and the results are evaluated based on samples collected during field surveys. Results indicate that land-cover classification obtained from multi-date NDVI performs better (overall accuracy of 88.8% and kappa of 0.86) than single-date multispectral data (overall accuracy of 81.4% and kappa coefficient of 0.78). The Z-test indicated that the difference in performance between the two approaches was statistically significant. The lower performance observed for single-date multispectral classification is due to similarities in spectral responses for targets of deciduous vegetation that lose their foliage and can be misread as non-vegetated areas. Meanwhile, an accurate classification by time series of plant clusters in seasonal forests allows incorporating seasonal variability of land-cover classes during the rainy and dry seasons, as well as transitions between seasons. The most important variables that contributed to the accuracy were the red, Near Infrared (NIR) and Short-Wave Infrared (SWIR) bands in single-date multispectral classification and the months in the dry season were the most relevant in multi-date NDVI classification.

Leaf water relations reflect canopy phenology rather than leaf life span in Sonoran Desert trees

Article

Feb 2021
TREE PHYSIOL

Plants from arid environments display covarying traits to survive or resist drought. Plant drought resistance and ability to survive long periods of low soil water availability should involve leaf phenology coordination with leaf and stem functional traits related to water status. This study tested correlations between phenology and functional traits involved in plant water status regulation in 10 Sonoran Desert tree species with contrasting phenology. Species seasonal variation in plant water status was defined by calculating their relative positions along the iso/anisohydric regulation continuum based on their hydroscape areas (HA)—a metric derived from the relationship between predawn and midday water potentials—and stomatal and hydraulic traits. Additionally, functional traits associated with plant water status regulation, including lamina vessel hydraulic diameter (DHL), stem-specific density (SSD), and leaf mass per area (LMA) were quantified per species. To characterize leaf phenology, leaf longevity (LL) and canopy foliage duration (FD) were determined. HA was strongly correlated with FD but not with LL; HA was significantly associated with SSD and leaf hydraulic traits (DHL, LMA) but not with stem hydraulic traits (vulnerability index, relative conductivity); and FD was strongly correlated with LMA and SSD. Leaf physiological characteristics affected leaf phenology when it was described as canopy foliage duration, better than when described as leaf longevity. Stem and leaf structure and hydraulic functions were not only relevant for categorizing species along the iso/anisohydric continuum but also allowed identifying different strategies of desert trees within the ‘fast–slow’ plant economics spectrum. The results in this study pinpoint the set of evolutionary pressures that shape the Sonoran Desert Scrub physiognomy.

Aspectos fitossociológicos e de crescimento de Commiphora leptophloeos no semiárido brasileiro

Article

Full-text available

Mar 2017

Objetivou-se analisar aspectos fitossociológicos e de crescimento de Commiphora leptophloeos (Mart.) J. B. Gillett. no semiárido brasileiro. A espécie foi estudada por meio de pesquisa bibliográfica e dados de 40 parcelas permanentes em área de caatinga, instaladas em 2008 e remensuradas em 2013, estimando-se densidade relativa (DR), frequência relativa (FR), dominância relativa (DoR), valor de importância (VI), regeneração natural (RN), crescimento em área basal (CB) e incremento periódico anual (IPA). A espécie apresentou DR de 0,04 a 12,82%, FR de 0,10 a 9,53 %, DoR de 0,01 a 19,58 %, VI de 0,14 a 10,87% e RN de 0,83 a 2,34 %. O CB foi negativo, quando considerada a mortalidade. O IPA foi de 0,00 a 0,25 cm ano-1. A espécie se destaca por sua DoR, no entanto, apresenta baixas DR, FR e RN. Apresenta crescimento lento, que aliado a problemas de RN e sua extração sem manejo pode restringir a sua continuidade na vegetação.

Variação sazonal das redes de interações planta-artrópodes em Floresta Tropical Sazonalmente Seca

Article

Full-text available

Aug 2020

This article presents a broad view of the interactions between plants and arthropods in the Caatinga ecosystem, highlighting the role of climatic seasonality in the availability and quality of plant resources, as well as the effects of these factors in the production of plant chemical defenses, mutualistic interactions, and antagonistic interactions as herbivory. The indirect effects of one trophic level on another in the Caatinga ecosystem are also reported.The Caatinga and other dry forests share several characteristics, such as the prevalence of the biotic pollination system and the abiotic dispersion of seeds. The high frequency of plants with extrafloral Nectaries allows a wide range of interactions between plants and arthropods, but especially with ants. However, all these interactions present their costs and benefits in a variable way, with the main justification for the seasonality of abiotic factors. The Caatinga has been undergoing fragmentation due to anthropic actions and climate change is already showing criticism about various aspects of the ecology of this ecosystem. Thus, the breakdown or changes in the interactions cause multiple effects at several different biological levels that will have repercussions from the population level to the level of ecosystems, being essential the understanding of the ecological interactions in terms of forest dynamics so that only this way occurs properly. planning for restoration and best conservation practices in the Caatinga.

Phenology of Aloysia hatschbachii cultivated in a subtropical region

Article

Full-text available

Jun 2020

Aloysia hatschbachii is an endangered species that occurs endemically in Paraná and has potential for essential oil production. Expanding research on threatened species could serve as a tool to ensure their conservation, management and reproduction. In this study, we sought to evaluate phenological phases (phenophases) for species Aloysia hatschbachii in the years 2018 and 2019 by conducting monthly checks of a plant population consisting of 5 individuals, identifying the phenological events of budding, mature leaves, flowering, fruiting, leaf senescence and leaf fall, using the percent index of intensity as well as the index of activity in the sampled individuals regarding the occurrence of such phenomena, and then correlating phenological data with meteorological variables. The phenological phases showed synchrony in activity throughout most of the assessed period, but were not always synchronous in intensity. Budding occurred between July and April, and mature leaves were present all year round. The patterns of leaf senescence and leaf fall revealed that the species has nondeciduous characteristics. These phenophases were influenced by relative air humidity. Flowering occurred between November and April, while fruiting lasted from December to May, with the reproductive stage being influenced by air temperature and by incident solar radiation.

Water storage of a typical tree species in the Caatinga biome ( Caesalpinia pyramidalis Tul.)

Article

Aug 2023

Our understanding of the movement and storage of water in typical Caatinga plants is still limited and often disregarded in water balance calculations. This is why the objective of this work was to evaluate the water storage dynamic in typical trees of the Caatinga biome during the dry, rainy and transition period by gauging the water content levels that cause the onset of leaf emergence. In a preserved Caatinga forest, soil and stem water content of six trees of the representative species catingueira ( Caesalpinia pyramidalis Tul.) were monitored with low‐cost capacitive sensors. Leaf moisture, leaf area index, leaf and stem water volume, and sap flow density were measured. The emergence of leaves occurred with a stem moisture of 0.32 m ³ m ⁻³ , and the leaf area index was maximum with a stem moisture of 0.34 m ³ m ⁻³ . Catingueira plants are able to absorb water below the soil water potential commonly determined as the permanent wilting point (−1.5 MPa). The volume of water stored in the plants represents 108% of the average volume stored in the Boqueirão reservoir during the study period.

ESTUDOS FENOLÓGICOS DE LEGUMINOSAS ARBÓREAS DAS FLORESTAS TROPICAIS SECAS DO NORDESTE BRASILEIRO NOS ÚLTIMOS 10 ANOS

Chapter

Full-text available

Apr 2023

Os estudos fenológicos são ferramentas que visam compreender o ciclo de vida das espécies vegetais e investigam possíveis alterações na ecologia destas em resposta às interferências antrópicas e às mudanças climáticas. Através desses estudos, estratégias de conservação e restauração de habitats perturbados podem ser delineadas. Neste trabalho, buscamos fornecer um panorama sobre a situação dos estudos fenológicos de leguminosas arbóreas nativas das florestas tropicais secas do Nordeste brasileiro nos últimos 10 anos (2010-2020), componente este, bastante representativo nas florestas de Caatinga e Cerrado. Além disso, traçamos tendências nas respostas fenológicas vegetativas e reprodutivas da comunidade arbórea destes estudos utilizando estatísticas circulares. As florestas de Caatinga lideram com a maioria dos estudos fenológicos de leguminosas arbóreas (73%), quando comparadas ao bioma Cerrado e áreas ecotonais do Nordeste do Brasil, o que pode ser atribuído à localização geográfica e as maiores extensões dos fragmentos desse bioma na região. Há uma predominância dos estudos fenológicos a nível de comunidade do componente arbóreo de Leguminosas em comparação aos de populações. No entanto, tais estudos fornecem uma visão de curto prazo das respostas fenológicas, e ainda são insignificantes, devido à grande diversidade arbórea de leguminosas que predominam nessas regiões. Observando o comportamento de toda a comunidade arbórea estudada nos últimos 10 anos, os eventos fenológicos vegetativos e reprodutivos são contínuos, mas com algumas tendências nos percentuais de atividade e particularidades de determinadas espécies. Este comportamento demostra diferentes estratégias das espécies no tempo da expressão das fenofases vegetativas e reprodutivas distribuídos do decorrer do ano, podendo ocorrer na estação seca, chuvosa ou nas transições, no qual evolutivamente levou ao estabelecimento e sobrevivência deste componente em um ambiente bastante estocástico como as florestas tropicais secas

Xylem anatomical traits determine the variation in wood density and water storage of plants in tropical semiarid climate

Article

Nov 2022
FLORA

Wood density (WD) is a functional trait that integrates hydraulic safety and efficiency, water and carbohydrate storage, and biomechanical properties of plants. The global economic spectrum of wood shows that average WD tends to be higher in dry regions than in humid regions. In this study, we investigated the factors determining WD variation, the maximum water content in wood (WCmax), and their possibly consequences to hydraulic functioning of plants under tropical semiarid climate. Fourteen xylem anatomical traits related to mechanical support, water storage, and hydraulic efficiency and safety were measured in 39 woody species commonly found in a seasonally dry tropical forest in the Brazilian semiarid region. We tested the phylogenetic signal of all traits. The range of WD was 0.24–0.85 g cm⁻³ (average WD = 0.62 g cm⁻³). Fractions of vessel wall, fiber wall, fiber lumen, and fiber type highly influenced WD. Septate and gelatinous fibers decreased WD, whereas libriform fibers contributed to the increase in WD. Axial and radial parenchyma, fiber lumen fractions, and septate fibers presence determined WCmax variation. Xylem anatomical traits showed a weak phylogenetic signal. Wood density had a phylogenetic antisignal, indicating a functional convergence independent of phylogenetic proximity, despite species varying in their anatomical patterns. We conclude that the increase in the average WD in the analyzed species was associated with the investment in vessel wall, fiber wall fraction, and libriform fibers (mechanical support structures), which possibly increase hydraulic safety. Thus, we suggest that fiber types are important determinants of WD and WCmax and should receive more attention.

STEEP: a remotely-sensed energy balance model for evapotranspiration estimation in seasonally dry tropical forests

Preprint

Full-text available

Sep 2022

Improvement of evapotranspiration (ET) estimates using remote sensing (RS) products based on multispectral and thermal sensors has been a breakthrough in hydrological research. In large-scale applications, methods that use the approach of RS-based surface energy balance (SEB) models often rely on oversimplifications of the aerodynamic resistances. The use of these SEB models for Seasonally Dry Tropical Forests (SDTF) has been challenging due to incompatibilities between the assumptions underlying those models and the specificities of this environment, such as the highly contrasting phenological phases or ET is mainly controlled by soil–water availability. We developed a RS-based SEB model from a one-source bulk transfer equation, called STEEP. Our model uses the Plant Area Index to represent the woody structure of the plants in calculating the moment roughness length. In the aerodynamic resistance for heat transfer, the parameter kB-1 was included, correcting it with RS soil moisture. Besides, the remaining λET in endmembers pixels was quantified using the Priestley-Taylor equation. We implemented the STEEP algorithm on the Google Earth Engine platform, using worldwide free data. Four sites with eddy covariance data located in the Caatinga, the largest SDTF in South America, in the Brazilian semiarid region, were used to evaluate the STEEP model. Our results show that STEEP based on the specific characteristics of the SDTF increased the accuracy of ET estimates without requiring any additional climatological information. This improvement is more pronounced during the dry season, which in general, ET for these SDTF is overestimated by traditional SEB models, as happened in our research with the SEBAL. The STEEP model had similar or superior behaviour and performance statistics relative to global ET products (MOD16 and PMLv2). This work contributes to an improved understanding of the drivers and modulators of the energy and water balances at local and regional scales in SDTF.

Quantification of Wood Biomass in an Area of Sustainable Annual Production in the Brazilian Semiarid Region Aiming at Generating Renewable Energy

Article

Aug 2022

The aim of this study was to quantify the production and determine the energy potential of forest wood biomass resulting from the exploitation of species in the Caatinga Biome. The study was carried out in an “Annual Production Unit,” with seven temporary plots allocated. Forest inventories were carried out of individuals with bole diameter at breast height of at least 2 cm. Based on the result of the importance value index, a sample of tree species was selected and felled in each plot to determine the moisture content, basic density, and higher heating value of the wood. After wood extraction, the resulting biomass was weighed in kg and divided into strata according to the parameters arboreal stratum (live trees) and necromass (dead trees), with subdivision of each into wood (Ø > = 2 cm DBH) and co-product (Ø < 2 cm DBH). The following values volumetric production were verified: arboreal stratum: wood – 38.0 m3 ha−1 (60.63%) and co-product – 16.27 m3 ha−1 (25.90%); necromass stratum: wood – 6.33 m3 ha−1 (10%) and co-product – 2.09 m3 ha−1 (34%). There were significant differences between the vegetation strata, suggesting the existence of mosaics suitable for energy exploitation of wood from the Caatinga Biome, since the co-products of living biomass and necromass amounted to 29.2% of the total biomass per hectare and represented potential energy generation of 30.30 kWh ha−1, 14% of the total estimated energy potential of the area.

Exotic Goats Do Not Affect the Seed Bank But Reduce Seedling Survival in a Human-Modified Landscape of Caatinga Dry Forest

Article

Jan 2022

Coordinación de estrategias de uso de los recursos de especies leñosas del matorral de Chile: Relaciones entre rasgos funcionales de copa, hoja, tallo, raíz y fenología

Article

Full-text available

Dec 2021

Resource-use strategy coordination across woody species of the Chilean matorral: Relationships among functional traits of crown, leaf, stem, root and phenology SUMMARY Variation of functional traits among species allows evaluating their life strategies. The whole-plant economic spectrum proposes coordination of the form and function across different plant organs to optimize a resource-use strategy. However, few studies have evaluated the coordination among woody species through functional traits from different plant organs. We evaluated variation and coordination of crown, leaf, stem, root and phenology trait values across woody species of the semi-arid Mediterranean matorral of Chile. We hypothesize that sclerophyllous and malacophyllous woody species vary and coordinate their trait values along an ecological dimension that separates their resource-use strategies from conservative to acquisitive, respectively. We analyzed the variation and correlation of 14 functional traits for 12-16 species. The functional trait values between sclerophyllous and malacophyllous species did not differ across the whole-plant economic spectrum. Traits were coordinated along multiple ecological dimensions. The first dimension was associated with the leaf economic spectrum and plant morphology, yet differed between sclerophyllous and malacophyllous species. Sclerophyllous species combined mostly conservative foliar trait values (longer leaf life span) with acquisitive morphological trait values (larger maximum plant height and longer lateral extension of roots), while malacophyllous species exhibited opposite combinations. The second dimension was associated with variation in phenology and root traits. This dimension separated species with conservative phenological and root trait values (delayed growth onset and deeper rooting depth) from opportunistic species with opposite trait values. The third dimension was coordinated by wood density and the leaf 13 C-isotopic composition. This dimension separated the drought-tolerant species with high stem densities and higher leaf water use efficiency from opportunistic water-use species with opposite attributes. In contrast with our hypothesis, in the Chilean matorral the species can combine conservative and acquisitive trait values to use resources and coordinate their resource use strategies across multiple dimensions. This decoupling of plant strategies could occur because different organs and phenology are exposed to different environmental filters. RESUMEN La variación de rasgos funcionales entre especies permite evaluar sus estrategias de vida. El espectro de la economía de la planta propone una coordinación de la forma y función de diferentes órganos de la planta para maximizar el uso de recursos. Sin embargo, existen pocos estudios evaluando la coordinación de estrategias de uso de recursos de las especies a través de rasgos funcionales que se encuentran en diferentes órganos de la planta. En este estudio se evalúa la variación y coordinación de valores de rasgos funcionales de copa, hoja, tallo, raíz y fenología relacionados con el uso de los recursos a través de especies leñosas del matorral de Chile. La hipótesis es que las especies leñosas esclerófilas y malacófilas varían y coordinan sus valores de rasgos funcionales a lo largo de una dimensión ecológica que separa sus estrategias de uso de recursos de conservativa a adquisitiva, respectivamente. Las diferencias y correlaciones de 14 rasgos funcionales fueron analizadas a través de 12-16 especies leñosas. Los valores de rasgos funcionales entre especies esclerófilas y malacófilas no difirieron significativamente para ocho de los 15 rasgos funcionales evaluados. La coordinación de valores rasgos funcionales fue a través de múltiples dimensiones ecológicas. En la primera dimensión coordinaron el espectro de la economía de la hoja y la morfología de la planta y fue la única dimensión que separó a las especies esclerófilas de las malacófilas. Las especies esclerófilas combinaron atributos foliares conservativos (mayor longevidad de hoja) y atributos morfológicos adquisitivos (mayor altura máxima de planta y mayor extensión lateral de raíces), mientras las especies malacófilas combinaron atributos opuestos. La segunda dimensión

ÍNDICE DE VEGETAÇÃO POR DIFERENÇA NORMALIZADA ASSOCIADO ÀS VARIÁVEIS PLUVIOMÉTRICAS PARA A SUB-BACIA DO RIO ESPINHARAS – PB/RN

Article

Full-text available

Feb 2021

No semiárido brasileiro, onde se insere o bioma caatinga, a precipitaçãos é um dos fator limitante para seu desenvolvimento sócioeconômico e ambiental, este estudo avaliou a correlação existente entre o nível de cobertura vegetal e as variáveis pluviométricas locais, considerando a climatologia de 2005 e 2015, utilizando-se imagens dos sensores TM e OLI dos satélites Landsat 5 e Landsat 8, respectivamente. O ano de 2005 apresentou maiores valores de NDVI em relação a 2015, com valores máximos de 0,71 e 0,78 no período seco e úmido, respectivamente. No ano de 2015, os valores máximos são de 0,64 e 0,61, para o período seco e úmido, respectivamente. Os maiores valores foram observados no período chuvoso de 2005, nas áreas de influência das estações meteorológicas de Matureia, Salgadinho e Areia de Baraúnas. No período seco, nota-se a baixa variabilidade dos valores de NDVI, sendo as maiores leituras observadas nas estações de Matureia, Salgadinho e Teixeira. As estações que apresentaram as maiores reduções nos valores de NDVI de 2005 para 2015, no período chuvoso, foram Matureia, Santa Teresinha e Salgadinho, com reduções de 41,9%, 38,2% e 32,7%, respectivamente. As correlações mais significativas foram estabelecidas para os períodos secos. As menores correlações foram verificadas no período chuvoso. A elevação dos níveis pluviométricos na região não implicou o aumento progressivo nos valores de NDVI. Palavras-chave: semiárido; geoprocessamento; índice de vegetação normalizada. Normalized difference vegetation index associated with pluviometric variables for Espinharas River sub-basin - PB/RN States ABSTRACT: In the Brazilian semiarid, where the caatinga biome is inserted, precipitation is a limiting factor for its socioeconomic and environmental development, This study evaluated the correlation between the level of vegetation cover and the local rainfall variables, considering the climatology of 2005 and 2015, using images from the TM and OLI sensors of the Landsat 5 and Landsat 8 satellites, respectively. The year 2005 presented higher NDVI values compared to 2015, with maximum values of 0.71 and 0.78 in the dry and wet periods, respectively. In 2015, the maximum values are 0.64 and 0.61, for the dry and wet periods, respectively. The highest values were observed in the rainy period of 2005, in the weather stations of Matureia, Salgadinho and Areia de Baraúnas. In the dry period, the low variability of NDVI values is noted, with the highest readings observed in the Matureia, Salgadinho and Teixeira platforms. The platforms that showed the greatest reductions in NDVI values from 2005 to 2015, in the rainy season, were Matureia, Santa Teresinha and Salgadinho, with reductions of 41.9%, 38.2% and 32.7%, respectively. The most significant correlations were established for the dry periods. The smallest correlations were found in the rainy season. The increase in rainfall levels in the region did not imply a progressive increase in NDVI values. Keywords: semiarid; geoprocessing; normalized difference vegetation index.

Glyphosate effects on tree species natives from Cerrado and Caatinga Brazilian biome: Assessing sensitivity to two ways of contamination

Article

May 2021
SCI TOTAL ENVIRON

Glyphosate is applied for dissection in no-till and post-emergence management in transgenic crops in agricultural fields near the Cerrado and Caatinga biomes. These biomes together represent 33.8% of the Brazilian territory, contributing to the maintenance of great world diversity in flora and fauna. Despite actions to protect them, the proximity with agricultural areas and intense use of glyphosate puts at risk the preservation of native vegetation due to the contamination via herbicide transport processes. Our objectives were: i) to determine the sensitivity of native species from the Cerrado and Caatinga to glyphosate contamination via drift and groundwater; ii) evaluate the level of sensitivity to glyphosate among the different organs of plants. The highest intoxications (upper 80%) were observed for Bauhinia cheilantha, Mimosa caesalpiniaefolia, Mimosa tenuiflora and Amburana cearensis due to drift simullation. The species with 90% of total dry matter reduction were Bauhinia cheilantha, Enterolobium contortisiliquum, Mimosa caesalpiniaefolia, Mimosa tenuiflora, Tabebuia aurea. B. cheilantha and M. tenuiflora are most affected by exposure to glyphosate drift, with 50% of total dry matter reduction when exposed to doses below 444,0 g ha⁻¹. Leaf growth is more sensitive to glyphosate for drift exposure for most species. Hymenaea courbaril is an exception, with greater sensitivity to root growth (50% dry matter reduction at doses below 666,0 g ha⁻¹). B. cheilantha is the species most sensitive to drift exposure; however, it showed complete tolerance to contamination in subsurface waters. Other species such as Anadenanthera macrocarpa and M. caesalpiniifolia are also sensitive to drift, but without reach 90% of total dry matter reduction. A. macrocarpa, M. caesalpiniifolia and T. aurea were tolerant to contamination by subsurface water. The differential tolerance of trees confirms glyphosate's potential as a species selection agent in the Cerrado and Caatinga biomes.

Uso, conhecimento e conservação de Myracrodruon urundeuva: uma revisão sistemática

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Nov 2020

Myracrodruon urundeuva, conhecida popularmente como aroeira, é amplamente distribuída no território brasileiro e considerada espécie polivalente por sua diversidade de usos, que incluem aplicações como combustível, madeira, forragem, apicultura, recuperação de áreas e o uso medicinal, muito praticado por populações rurais. Essa diversidade de aplicações pode ameaçar a conservação da espécie devido à exploração excessiva e o uso de técnicas inadequadas que podem resultar em declínio das populações naturais. Com este trabalho, o objetivo foi verificar o conhecimento atual sobre M. urundeuva e seu estado de conservação. Para tanto, foi realizada uma revisão sistemática seguindo o modelo PRISMA, com busca de artigos publicados entre 2010 e 2020. Foram identificados inicialmente 333 artigos, dos quais 165 foram incluídos na revisão. Os artigos se distribuem nas categorias atividade biológica, biologia vegetal e ecologia, composição química, etnobotânica e produção. A maior parte dos estudos diz respeito à avaliação das atividades biológicas da espécie com evidências de efeitos anti-inflamatório, antimicrobiano, antioxidante, antifúngico, antiviral, inseticida e neuroprotetor entre outros, corroborando aplicações terapêuticas da espécie descritas em estudos etnobotânicos. A aroeira não é considerada oficialmente ameaçada de extinção. Embora muitos autores asseverem que a exploração excessiva da espécie seja uma ameaça a sua conservação, não foram encontrados dados que suportem tal suposição. São necessários estudos que avaliem o estado populacional da espécie, a condição ambiental de sua área de distribuição e seu volume de exploração, para que se possa avaliar adequadamente o estado de conservação da espécie e proposição de medidas para seu uso sustentável.

Leaf Phenology of Tree Species in Response to the Seasonality of Water Availabilityin Caatinga, Northeast Brazilブラジル北東部における水分条件の季節変化に対するカーチンガ構成樹木の葉フェノロジーの応答

Article

Jan 2020

The Caatinga, which is the largest tropical dry forest in the neotropics, is distributed in the semi-arid region of northeast Brazil. We investigated the relationship between tree phenology and hydroclimatic conditions in Petrolina-Perunambuco, Brazil. The leaf phenology of Caatinga trees was strongly related to the seasonality of water availability. Leaf flushing was triggered by the slightly increased soil water content immediately after the start of the rainy season in the year of observation, and then the canopies of Caatinga tree species formed synchronously in about 2 weeks. Progressive leaf abscission occurred through the first 3 to 4 months of the dry season, suggesting that the production of Caatinga trees can continue for a time under high water deficits by regulating water status. These results demonstrated that the leaf phenology of Caatinga tree species effectively adaptated to limited water availability in a semi-arid region.

Sparse Gash model applied to seasonal dry tropical forest

Article

Nov 2020
J HYDROL

Rainfall interception represents a significant component of the water balance and its modelling and simulation are essential to understanding the hydrologic cycles in different ecosystems. Caatinga is a seasonal dry tropical forest, characterized by a deciduous and xerophilous vegetation that covers large areas in Brazil. This domain appears as a highly vulnerable natural water resource system, and is important for studies about droughts, impacts on soil erosion, as well as the adaptation to altered rainfall patterns and intensities. Specifically, knowledge about rainfall partitioning in such ecosystem can improve hydrologic modelling and efficiency. This work was carried out for parametrizing and validating the sparse Gash model, simulating the rainfall interception from five Caatinga species individually as well as aggregated together as a mixed-species forest. Proportions of gross rainfall into throughfall varied from 59.8 to 78.9%, and into interception were between 20.4 and 39.5%. Results also showed low scattering of predictions, as well as absence of constant and systematic errors during simulations. Rainfall interceptions predicted by the sparse Gash model resulted in mean absolute errors (MAE) ranging from 0.23 to 0.41 mm, while agreement indices (d) varied between 0.94 and 0.97 for the studied Caatinga species and the mixed vegetation. The sparse Gash model was reliable enough to apply to Caatinga ecosystem, appearing as a valuable tool for studying rainfall interception in this domain.

Guia de Propágulos e Plântulas da Caatinga

Book

Full-text available

Nov 2019

Guia com fotos e informações técnicas para identificação de espécies 19 espécies da Caatinga nas fases iniciais de desenvolvimento. As espécies são identificadas por meio de dados técnicos sobre fruto, semente, germinação, plântula e muda. O livro tem distribuição gratuita e pode ser feito download, após cadastro, no site: http://www.nema.univasf.edu.br/site/index.php?page=download

Drought response strategies of deciduous and evergreen woody species in a seasonally dry neotropical forest

Article

Full-text available

Oct 2020
OECOLOGIA

Deciduous and evergreen trees are usually considered the main coexisting functional groups in seasonally dry tropical forests (SDTF). We compared leaf and stem traits of 22 woody species in the Brazilian Caatinga to investigate whether deciduous (DC) and evergreen (EV) species have divergent water-use strategies. Our hypothesis was that DC trees compensate for their short leaf longevity by being less conservative in water use and showing higher variation in the seasonal water potential after leaf shedding. Evergreen species should exhibit a highly conservative water use strategy, which reduces variations in seasonal water potential and the negative effects of desiccation. Our leaf dynamics results indicate that the crown area of DC trees is more sensitive to air and soil drought, whereas EV trees are only sensitive to soil drought. Deciduous species exhibit differences in a set of leaf traits confirming their acquisitive strategy, which contrasts with evergreen species. However, when stomatal traits are considered, we found that DC and EV have similar stomatal regulation strategies (partially isohydric). We also found divergent physiological strategies within DC. For high wood density DC, the xylem water potential (Ψ xylem) continued to drop during the dry season. We also found a negative linear relationship between leaf life span (LL) and the transpiration rate per unit of hydraulic conductivity (Λ), indicating that species with high LL are less vulnerable to hydraulic conductivity loss than early-deciduous species. Collectively, our results indicate divergence in the physiology of deciduous species, which suggests that categorizing species based solely on their leaf phenology may be an oversimplification.

GEOGRAPHICAL DISTRIBUTION OF GALL-INDUCING INSECTS ASSOCIATED WITH COUEPIA OVALIFOLIA (CHRYSOBALANACEAE), AN ENDEMIC PLANT TO BRAZIL

Chapter

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Aug 2020

Valéria Cid Maia

Densidade básica da madeira de um ecossistema de "campina" em Roraima, Amazônia brasileira

Article

Full-text available

Jan 2004

Estudo comparativo da fenologia de espécies arbóreas de floresta de altitude e floresta mesófila semidecídua na Serra do Japi, Jundiaí, São Paulo

Article

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Jan 1989

A hectare of cerrado. II. Flowering and fruiting of thick-stemmed woody species

Article

Full-text available

Jan 2001
PHYTON-ANN REI BOT A

Ilse Silberbauer-Gottsberger

In a hectare of cerrado in the municipality of Botucatu, State of São Paulo, Brazil, individuals in flower and/or fruit were counted for 26 thick-stemmed woody species (stem-circumference of 10 cm or more at the height of 30 cm above ground) during 12 months, at intervals of 14 days, from April 1973 to March 1974. Although rainfall of the cerrado region is seasonal, the phenological events seem to be not well correlated with this seasonality, whether examined on the species level nor on the individual level. No doubt, the main flowering period was October and the first half of November, which is at the end of the dry season and the beginning of the rainy season, whereas during February, March, and April less flowering occurred. But across the year of the study, at least some individuals were on every census date in flower. The main fruiting period was during the rainy season, in the second half of December and first half of January. In total 53% of the individuals flowered, and of these, 72% produced ripe fruits. The majority of species have an annual flowering pattern. Duration of flowering, which was defined as the timespan between the flowering of the first individual of a species and the end of flowering of the last individual, was different for the species. Also the flower duration of the single individuals within one species was different. Extremely long-flowering seems to be characteristic of many thick-stemmed woody cerrado species. The long flower duration of a species may be achieved by long-flowering of the single individuals and also by low synchrony of flowering within the individuals of a species. Referring to the total of the species, duration of flowering of a species is not correlated with total number of its individuals, but the two species with the highest number of individuals also had the most of individuals with flowers and fruits. Within a species tall individuals flowered more frequently. The number of species and the number of individuals in flower (for each observation date) show also only moderate correlation. On a few observation dates the relationship was even reversed. During the dry season the few flowering species had the same number of individuals in flower as the many species at the beginning of the rainy season. Throughout the year, at all survey dates, one species dominated in terms of number of individuals flowering and the same was true for fruiting. In several species flowering stage and ripe fruiting stage overlapped, and the same was true for individual plants of Styrax ferruginea. The study also shows that phenological surveys of a complete census of a representative area give different insights into the phenological behavior of a community and its species than surveys based on selected individuals of selected species.

Variações fenológicas das espécies do cerrado da Reserva Biológica de Moji Guaçu, Estado de São Paulo

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Jan 1988

Estrutura da vegetação caducifólia espinhosa (Caatinga) de uma área do sertão central de Pernambuco

Article

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Jun 2008

Vegetation structure of a "Caatinga" sensu stricto (thorny deciduous woodland) was studied in a lowland area at the municipalities of Floresta and Betânia, State of Pernambuco, Brazil. Height and perimeter of all woody plants to be found in 1 hectare were censured when stem perimeter at soil level was > 3 cm and the height > 1 m. A total of 3,140 individuals belonging to 28 plant species were registered with a basal area of 18.5 m². In general, results from surveys at lowlands on plain areas presented smaller individual stem diameters than those located near streams or mountain range sites. Physiognomic differences in the caatinga sensu stricto on lowlands are related to differences on the density of plants with greater diameters. The diameter distribution of Caesalpinia gardneriana Benth. (Caesalpiniaceae) and Croton rhamnifolioides Pax & K. Hoffm. (Euphorbiaceae), the two most important tree species, indicate that these plant populations may be regenerating from former disturbance.

Comparação de métodos de determinação da densidade básica em Madeira

Article

Full-text available

Jan 1990

O presente trabalho visou o estudo comparativo de 6 métodos propostos para a determinação da densidade básica em madeira e ainda, o efeito de 3 dimensões dos corpos de prova nos métodos. Para tal empregou-se distintamente cerne e alburno da espécie Hymenaea cobaril L. (jatobá) em corpos de provas nas dimensões 2 x 2 x 1 com (D1), 2 x 2 x 3 com (D2) e 2 x 2 x 5 cm (D3). Os métodos analisados foram: a) método de imersão-baseado na variação do peso do líquido (M1); b) o método de medição direta do volume por paquímetro (M2); c) método de imersão-baseado na variação do peso da amostra (M3); d) método de medição direta do volume por cilindro graduado-corpo de prova imerso em areia (M4); e) método de máximo teor de umidade (M5) e f) método de medição direta do volume for cilindro graduado-corpo de prova imperso em água (M6). Os métodos M1, M3 e M5 foram os mais precisos, de melhores repetibilidades, iguais estatisticamente e que não sofreram influência das dimensões influenciaram significativamente os métodos M2, M4 e M6, que foram os menos precisos.

Phenology and Ecophysiology of the Tropical Tree, Tabebuia Neochrysantha (Bignoniaceae)

Article

Full-text available

Apr 1982

Phenology and seasonal variations in water stress, as reflected in variations in stem circumference, were monitored throughout 1978 in numerous Tabebuia neochrysantha growing at several dry and wet sites in a lowland deciduous forest in Guanacaste, Costa Rica. The rate of leaf fall during the early dry season was strongly correlated with the decline in soil moisture and increasing water stress of the trees. Without exception, recovery from water stress was required for flowering and shoot emergence. At dry sites rehydration ocurred only after isolated rain showers or irrigation; at wet sites it took place during continued drought, probably as a consequence of the decrease in transpiration during leaf fall. Flowering has been observed to occur at any time between the beginning (December) and end (May) of the dry season. Differences in the timing and intensity of flowering as well as in the timing of leaf fall and shoot emergence can be accounted for by site-dependent differences in the rates of desiccation and rehydration of trees in conjunction with year-to-year variation in the timing and intensity of rainfall. No evidence for the control of seasonal development by other environmental factors, such as variations in temperature of photoperiod, was obtained.

Dados fenológicos de 10 espécies arbóreas de uma área de Caatinga (Alagoinha - PE)

Article

Full-text available

Dec 1988

Phenological studies were carried out on 10 tree species of economical value occurring in a caatinga area (Alagoinha-PE). The observations were made over a period of 6 years (1982 to 1988), but 1986 was considered as the reference point for the analysis, when monthly phenological records were made. The phenophases of leaf fall, new leaf formation, flowering and fruiting were analyzed using 3 individuals per selected species. The species studied were divided into two groups in terms of phenological behavior: evergreens with leaf replacement from the begirining to the end of the dry season and flowering only during the rainy season, except for Ziziphus joazeiro Mart, which flowered at the end of the dry season (December). Deciduos trees casting leaves over a period of 1 to 3 months ot the end of the dry season; 2 species flowered during the dry season (new leaves and flowering occurring almost simultaneously); 2 species flowered during the rainy season (new leaves and flowering occurring at different times), and 2 species (Aspidosperma pyrifolium Mart, and Caesalpinia pyramidalis Tul.) showed two flowering peaks during each season, with immediate formation of new leaves. Seven of the 10 species studied produced fruits from the end of the dry season to the beginning of the rainy season, and the remaining ones produced fruit during the rainy season.

Emerging paradigms of tree phenology in dry tropics

Article

Full-text available

Sep 2005
CURR SCI INDIA

The tropical dry forests constitute a mosaic composed of several phenological functional types adapted to seasonal drought in different ways. Various functional types differ with respect to phenological timing and triggering factors, water relations, extent of deciduousness (∼leaflessness), etc. Duration of deciduousness in tropical trees (reflecting integrated effect of seasonal drought, tree characteristics and soil moisture conditions) is related to leafing patterns and resource use rates. Vegetative and flowering phenology of trees in dry tropics is primarily affected by the periodicity of rainfall and soil water availability. Occurrence of leaf-flushing as well as flowering during summer in majority of Indian tropical trees, when drought is severe, seems to be a unique adaptation to survive under strongly seasonal climate having a short growth promoting wet period and a long growth constraining dry period. The key phenological themes that need research focus in the dry tropics are: duration of deciduousness, timing of vegetative bud break, leaf strategy, water relations, seasonal flowering types and asynchrony. Analysis of functional types based on the duration of deciduousness and timing of bud break may enable better assessment of future climate change impact. There is a need for long-term quantitative documentation of tree phenological patterns in India through a phenological station network in diverse climatic/vegetational zones.

Phenology of tropical forests: patterns, causes, and consequences

Article

Full-text available

Feb 1995

Peter B Reich

Unlike the marked temperature-related periodicity of temperate forests, development tends to be continuous in aseasonal lowland tropical rain forests and becomes more episodic in response to increasing annual drought in tropical dry forests. Hence, in tropical rain forests, foliar development (production, senescence, and longevity) is largely under internal rather than environmental control. Tropical forests with marked annual dry seasons display associated seasonality of leaf production and shedding. This developmental seasonality can be explained by overlaying the influence of seasonality on trees' internally regulated development and appears to be controlled by acclimative physiological processes and not by sensitivity to photo-, thermo-periodic, or direct environmental cues. Consequences of tropical phenology stem from both the variety of leaf and species ecophysiological types common to a given moisture regime and their relative synchrony of development, and include larger diversity of ecophysiological species types in rain than dry forests; differential rates of herbivory in dry than wet seasons and for synchronous versus asynchronous leaf flushes; ecosystems with greater canopy foliar mass per hectare in rain than dry forests; and several leaf adaptations perhaps unique to tropical forests, such as delayed greening and seasonal leaf phenotypes. Phenology of rain forests should change little unless water balance changes markedly, and developmental events in rain forests may be relatively insensitive to moderate changes in CO2 or temperature. Phenology of dry forests could be more sensitive, and in opposite directions, to elevated CO2 and temperatures. Elevated CO2 might delay onset of leaf shedding and stimulate longer life span if stand level transpiration is reduced, whereas higher temperatures could lead to more rapid water depletion, longer leafless periods, and more strongly synchronized phenology. -from Author

Response of Cassava to Water Deficit

Article

Full-text available

Jan 2000
CROP SCI

Cassava (Manihot esculenta Crantz) responds to decreases in water status by pronounced stomatal closure and decreased leaf area growth. Many water deficit responses are thought to be regulated by abscisic acid (ABA). To evaluate the extent to which ABA accumulated in a temporal pattern related to water deficit and leaf area growth, five cassava genotypes were grown in greenhouse conditions and subjected to water deficit and recovery treatments during the vegetative-growth stage. Young and mature leaves were sampled for analysis of area growth and ABA. Under water deficit, leaves from all genotypes rapidly accumulated large amounts of ABA in both mature and young leaves. Correspondingly, young leaves halted leaf expansion growth and transpiration rate decreased. Young leaves accumulated more ABA than mature leaves in both the control and stressed treatments. The high ABA levels under water deficit were completely reversed to control levels after 1 d of rewatering. This rapid return to control ABA levels corresponded with a rapid recovery of leaf area growth rates. We postulate that the rapid reduction in leaf area growth and stomatal closure observed in our study may be due to cassava's ability to rapidly synthesize and accumulate ABA at an early phase of a water deficit episode.

The world-wide leaf economics spectrum

Article

Full-text available

May 2004

Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.

Seasonal Flowering and Fruiting Patterns in Tropical Semi-Arid Vegetation of Northeastern Venezuela

Article

Full-text available

Mar 1992
BIOTROPICA

Flowering and fruiting phenology were studied for thorn woodland (annual precipitation of 1179 mm) and thorn scrub (annual precipitation of 578 mm) stands in northeastern Venezuela. The global phenology of each vegetation type was assessed using multivariate techniques (ordination and chronological clustering). All species and their respective phenophases were analyzed simultaneously. The flowering of trees and tall shrubs occurred in both vegetation types at the end of the dry season and lasted throughout the entire rainy season. Short-duration rains late in the dry season may have triggered and synchronized flowering. Fruiting activities of trees and tall shrubs occurred in all months, whereas fruiting maturation was limited to the dry season and the beginning of the rainy season. The fluctuation in the abundance of fruits was related principally to the production of a large amount of dry, lightweight seeds during the dry season, whereas fleshy and dry, heavyweight fruits were more or less steadily produced throughout the year. This suggests an adaptation to favor wind dispersion of seeds during the dry season when the vegetation is leafless, as well as the maintenance of animal populations as dispersal agents throughout the year. Periods of similar phenological characteristics were statistically defined and compared to annual rainfall and soil moisture. Annual reproductive phenology was more synchronized for thorn scrub than for thorn woodland. This may be due to the fact that thorn scrub vegetation is subjected to more severe drought conditions and consequently responds more punctually to the reappearance of rain or soil moisture.

The Phenology of Tropical Forests: Adaptive Significance and Consequences for Primary Consumers

Article

Full-text available

Nov 2003
Annu Rev Ecol Systemat

Most tropical woody plants produce new leaves and flowers in bursts rather than continuously, and most tropical forest communities display seasonal variation in the presence of new leaves, flowers, and fruits. This patterning suggests that phenological changes represent adaptations to either biotic or abiotic factors. Biotic factors may select for either a staggering or a clustering of the phenological activity of individual plant species. We review the evidence for several hypotheses. The idea that plant species can reduce predation by synchronizing their phenological activity has the best support. However, because biotic factors are often arbitrary with respect to the timing of these peaks, it is essential also to consider abiotic influences. A review of published studies demonstrates a major role for climate. Peaks in irradiance are accompanied by peaks in flushing and flowering except where water stress makes this impossible. Thus, in seasonally dry forests, many plants concentrate leafing and flowering around the start of the rainy season; they also tend to fruit at the same time, probably to minimize seedling mortality during the subsequent dry season. Phenological variation at the level of the forest community affects primary consumers who respond by dietary switching, seasonal breeding, changes in range use, or migration. During periods of scarcity, certain plant products, keystone resources, act as mainstays of the primary consumer community.

Diversity of leaf phenology in a tropical deciduous forest in India

Article

Full-text available

Jan 2005
J TROP ECOL

Chandra Prakash Kushwaha

Patterns of leaf phenological diversity were documented in nine key tree species of a tropical deciduous forest in the Vindhyan region of India. Monthly leaf counts on 160 tagged twigs on ten individuals of each species were made through two annual cycles. Tree species exhibited a gradient of deciduousness ([similar]leafless duration), ranging from semi-evergreen species (entire population never becoming leafless) to 7-mo-deciduous species. The semi-evergreen species initiated leaf flush (bud break of vegetative bud) earlier around the spring equinox. In all deciduous tree species synchronous leaf-flush initiation, with low inter-annual variability, occurred during the hot dry summer (May7 mo and leaf strategy index 0.54-mo-deciduous, summer flushing, leafless period 25 mo, and leaf strategy index >0.87 mo, leaf-flush duration 3–4 mo, and leaf strategy index 1.0 (Boswelliaserrata and Lanneacoromandelica). Conspecific trees showed asynchrony with respect to leaf-flush completion, initiation and completion of leaf-fall, and extent of leafless period. Leaf strategy index (indicating rate of resource use and conservation) was strongly related with the leafless period in different species (r=0.82) and can serve as a useful index in leaf phenological studies and classification of plant functional types.

Wood density of trees in a “campina” ecosystem in Roraima, Brazilian Amazonia

Article

Full-text available

Dec 2004

Wood density (g.cm-3: oven-dry weight / wet volume) was determined for 13 of the main tree species of a “campina” ecosystem (Amazon caatinga) located in Roraima, north portion of Brazilian Amazonia. The wood samples for calculation of the density of each species were “sample disks” (bark, sapwood and heartwood) of different diameter classes. In total, 98 individuals were sampled in 150 wood pieces (52 with diameter < 1.6cm; 63 to 1.6-3.2cm, 27 to 3.2-4.8cm and 8 > 4.8cm). The species with the highest wood density was Matayba arborescens (Aubl.) Radlk. (0.68 g.cm-3), followed by Humiria balsamifera (Aubl.) St. Hill. (0.67 g.cm-3) and Pera schomburgkiana Müel. Arg. (0.64 g.cm-3). The smaller diameter classes were also those with lower density: 0.59 ± 0.06 (SD) g.cm-3 (< 1.6cm), 0.64 ± 0.08 g.cm-3 (1.6-3.2cm), 0.67 ± 0.06 g.cm-3 (3.2-4.8cm) and 0.69 ± 0.10 g.cm-3 (> 4.8cm). The weighted mean by biomass of the ecosystem was 0.64 ± 0.08 g.cm-3. This result is lower by 15.2% than that presently used for transformation of wood volume in biomass for “campina” ecosystems in Amazonia, influencing directly in the calculations of greenhouse gas emissions.

Seedling root morphology and biomass allocation of 62 tropical tree species in relation to drought- and shade-tolerance

Article

Full-text available

Jan 2009
J ECOL

Water availability is the main determinant of species’ distribution in lowland tropical forests. Species’ occurrence along water availability gradients depends on their ability to tolerate drought. To identify species’ traits underlying drought‐tolerance we excavated first year seedlings of 62 dry and moist forest tree species at the onset of the dry season. We evaluate how morphological seedling traits differ between forests, and whether functional groups of species can be identified based on trait relations. We also compare seedling traits along independent axes of drought and shade‐tolerance to assess a hypothesized trade‐off. Seedlings of dry forest species improve water foraging capacity in deep soil layers by an increased below‐ground biomass allocation and by having deep roots. They minimize the risk of cavitation by making dense stems, and reduce transpiration by producing less leaf tissue. Moist forest seedlings have large leaf areas and a greater above‐ground biomass, to maximize light interception, and long, cheap, branched root systems, to increase water and nutrient capture. Associations among seedling traits reveal three major drought strategies: (i) evergreen drought‐tolerant species have high biomass investment in enduring organs, minimize cavitation and minimize transpiration to persist under dry conditions; (ii) drought‐avoiding species maximize resource capture during a limited growing season and then avoid stress with a deciduous leaf habit in the dry season; (iii) drought‐intolerant species maximize both below‐ and above‐ground resource capture to increase competitiveness for light, but are consequently precluded from dry habitats. We found no direct trade‐off between drought‐ and shade‐tolerance, because they depend largely on different morphological adaptations. Drought‐tolerance is supported by a high biomass investment to the root system, whereas shade‐tolerance is mainly promoted by a low growth rate and low SLA. Synthesis . We conclude that there are three general adaptation strategies of drought‐tolerance, which seemingly hold true across biomes and for different life forms. Drought‐ and shade‐tolerance are largely independent from one another, suggesting a high potential for niche differentiation, as species’ specialization can occur at different combinations of water and light availability.

Increasing day-length induces flushing of tropical dry forest trees in the absence of rain

Article

Full-text available

Sep 2002

In many conspecific trees of >50 species highly synchronous bud break with low inter-annual variation was observed during the late dry season, around the spring equinox, in semideciduous tropical forests of Argentina, Costa Rica, Java and Thailand and in tropical savannas of Central Brazil. Bud break was 6 months out of phase between the northern and southern hemispheres and started about 1 month earlier in the subtropics than at lower latitudes. These observations indicate that "spring flushing", i.e., synchronous bud break around the spring equinox and weeks before the first rains of the wet season, is induced by an increase in photoperiod of 30 min or less. Spring flushing is common in semideciduous forests characterized by a 4-6 month dry season and annual rainfall of 800-1,500 mm, but rare in neotropical forests with a shorter dry season or lower annual precipitation. Establishment of new foliage shortly before the wet growing season is likely to optimize photosynthetic gain in tropical forests with a relatively short growing season.

LEAF PHENOLOGY OF WOODY SPECIES IN A NORTH AUSTRALIAN TROPICAL SAVANNA

Article

Dec 1997

Overview of the Brazilian caatinga

Chapter

Nov 1995

Everardo Valadares De Sá Sampaio

Prolonged seasonal drought affects most of the tropics, including vast areas presently or recently dominated by 'dry forests'. These forests have received scant attention, despite the fact that humans have used and changed them more than rain forests. This volume reviews the available information, often making contrasts with wetter forests. The world's dry forest heterogeneity of structure and function is shown regionally. In the neotropics, biogeographic patterns differ from those of wet forests, as does the spectrum of plant life-forms in terms of structure, physiology, phenology and reproduction. Biomass distribution, nutrient cycling, below-ground dynamics and nitrogen gas emission are also reviewed. Exploitation schemes are surveyed, and examples are given of non-timber product economies. It is hoped that this review will stimulate research leading to more conservative and productive management of dry forests.

Drought responses of neotropical dry forest trees

Chapter

Nov 1995

Structure and Function of Root Systems

Chapter

Jun 2007

Estudos fenológicos de algumas espécies lenhosas e herbáceas da caatinga

Article

Jan 1989

Comparative phenological studies of trees in tropical lowland wet and dry forest sites of Costa Rica

Article

Jan 1974

Fenologia de espécies lenhosas da caatinga

Article

Jan 2003

The effect of dry season irrigation on leaf phenology and the implications for herbivory in a tropical understory community

Article

Dec 1997

Leaf production during the dry season, a period of low herbivore abundance, may reduce levels of herbivore damage. To test this hypothesis, leaf phenology and herbivory on young leaves of ten species were compared between plants growing in control plots and plants in plots that were irrigated during the dry season in Barro Colorado Island, Panama. The irrigation treatment did not affect the leaf phenology of nonsynchronously flushing species, but changed the pattern in synchronous species. For synchronous species, the peak of leaf production at the beginning of the wet season was reduced and leaf production increased during the dry season. Levels of herbivory during the dry season tended to be lower in the irrigation plots, but the difference was significant in only two of six synchronous species. Water availability appeared to be the major factor regulating the timing of leaf production of synchronous species, but the shift in leaf production to the dry season reduced levels of herbivory in only some of the species.

El tamaño de la muestra y la frequencia de las observaciones en el estudio de las caracteristicas fenológicas de los arbores tropicales

Article

Jan 1975

The caatingas dominium

Article

Jan 1981

D. Andrade-Lima

Modification of Vegetative Phenology in a Tropical Semi-deciduous Forest by Abnormal Drought and Rain

Article

Mar 2002
BIOTROPICA

The control of vegetative phenology in tropical trees is not well understood. In dry forest trees, leaf abscission may be enhanced by advanced leaf age, increasing water stress, or declining photoperiod. Normally, it is impossible to dissect the effects of each of these variables because most leaves are shed during the early dry season when day length is near its minimum and leaves are relatively old. The 1997 El-Niño Southern Oscillation caused a ten-week long, severe abnormal drought from June to August in the semi-deciduous forests of Guanacaste, Costa Rica. We monitored the effect of this drought on phenology and water status of trees with young leaves and compared modifications of phenology in trees of different functional types with the pattern observed during the regular dry season. Although deciduous trees at dry sites were severely water stressed (ΨSTEM < −7MPa) and their mesic leaves remained wilted for more than two months, these and all other trees retained all leaves during the abnormal drought. Many trees exchanged leaves three to four months earlier than normal during the wet period after the abnormal drought and shed leaves again during the regular dry season. Irrigation and an exceptional 70 mm rainfall during the mid-dry season 1998/1999 caused bud break and flushing in all leafless trees except dormant stem succulents. The complex interactions between leaf age and water stress, the principal determinants of leaf abscission, were found to vary widely among trees of different functional types.

Water Stress and Tree Phenology in a Tropical Dry Forest in the Lowlands of Costa Rica

Article

Mar 1984

At dry sites, trees experienced water stress and shed their leaves early in the dry season. In most species, rehydration, followed by bud break, took place only after heavy rainfalls. In some species, leaf shedding was followed by rehydration and bud break during continuing drought. During shoot extension, which rarely lasted longer than a few weeks, trees experienced water stress in spite of growing in wet soils. At wet sites, trees experienced little or no apparent water stress; they remained evergreen or rapidly exchanged leaves during the dry season. In general, the timing of leaf fall and bud break and, in many species, anthesis was determined to a large extent by changes in tree water status. These phenomena, in turn, were a function of the interaction between the water status of the environment and the structural and functional state of the tree. At times the functional state of the tree would counteract the environmental influences; trees with growing shoots experienced temporary water deficits during the wet season, and bare trees rehydrated during drought. -from Authors

Principles of Dispersal in Higher Plants.

Article

Dec 1983

Mecanismos de Dispersion de Diasporas de una Selva Decidua en Venezuela

Article

Dec 1984

Tatiana Wikander

The predommant life-forms in a deciduous forest of northem Venezuela are found to be phanerophytes, lianas and chamaephytes. The dispersal mechanisms in this forest are anemochory (42%), zoochory (30%), barochory (19%), and autochory (9%). The distribution of dispersal mechanisms is a function of topography and the stratification of vegetation; anemochory dominates at higher elevations and in the upper strata of vegetation, whereas zoochory is most common at lower elevations and in lower levels of the forest.

Phenology and Other Characteristics of Tropical Semi-Deciduous Forest in North-Western Costa Rica

Article

Mar 1972

Rexford Daubenmire

In tropical deciduous trees in north-western Costa Rica leaf flushing is initiated during a period when drought stress, to which it appears an adaptation, is reaching its peak of severity. In contrast with temperate zone trees, flushing is spread over about 11 months. Leaf senescence in the tropical forest seems more clearly triggered by drought stress than by daylength. For the forest as a whole there are two flowering seasons, a major and a minor, that correlate with major and minor seasons of drought. Tropical deciduous trees combine entomophily with deciduousness, this showing clearly that both characters did not evolve in response to the same aspect of environment. In the tropical trees dissemination is usually by wind and occurs at the end of the season of lowest vegetative activity, whereas in temperate zone trees dissemination is typically at the end of the vegetative season. In both the tropical and temperate trees, temporary dry-season shrinkage of the trunk varies from negligible in some species to shrinkage that exceeds the net annual increment in others. Dry-season shrinkage seems a genetic character of those tropical trees that have been compared in both upland and riparian habitats. Divestment of leaves gave no special insurance against trunk shrinkage during the dry season in the tropics. In the same trees both flowering and flushing occurred at times when trunk shrinkage indicated high moisture stress. In comparison with the tropical trees, radial growth of those in temperate latitudes is much more rapid and is confined to a shorter segment of the year. Despite pronounced seasonality of cambial activity in the tropical trees, the xylem of only one species showed fairly distinct annual layers.

Phenology of Canopy Trees of a Tropical Deciduous Forest in Mexico

Article

Mar 1990

Phenology of 108 species (1094 trees) was monitored for 42 months in a tropical deciduous forest in the Pacific lowlands of Mexico. Leaf expansion was highly concentrated in June-July; the forest canopy was at least 75 percent full in only 30 percent of the study period. With few exceptions, the species were leafless for several months each year. Gradual leaf loss in most species suggested there were large inter- and intraspecific differences in length of the growing season. Peak flowering was in June-July. Flowering lasted less than two months in most cases. Closely related species typically flowered concurrently. The delay from flowering to dispersal showed no prominent mode. Peaks of seed dispersal showed no community mean, but endozoochores differed from other species in seasonality. Reproduction was annual for most populations, and sub-annual intervals were related to rainfall anomalies. The response of many species to rains in December or January indicated their phenology was driven by water availability, but other species were probably limited by photoperiod. Intensive use of stored resources was indicated by simultaneous flushing and flowering in many species.

A New Classification for Plant Phenology Based on Flowering Patterns in Lowland Tropical Rain Forest Trees at La Selva, Costa Rica

Article

Jun 1994

A new classification and conceptual framework for plant phenology are proposed to resolve problems in describing tropical patterns. A long-term (12 yr) survey of flowering in 254 lowland tropical rain forest trees of 173 species from the La Selva Biological Station in Costa Rica showed highly diverse, irregular, and complex patterns. Analysis of this survey data relied primarily on graphical analyses that provide data representation methods rather than numerical summaries that provide data reduction methods. The classification differs from previous ones in three ways. It uses, as the primary criterion, frequency of the time series, based on explicit time and amplitude scales, so that irregular temporal sequences are revealed. It features a system of subsidiary classes based on other quantitative descriptors: regularity, duration, amplitude, date, and synchrony Finally, the conceptual framework separates patterns at each level of analysis so that adding the time series at one level produces a time series for the next higher level. Levels are hierarchical from the flower to the individual, population, and community with additional non-nested levels such as the guild. The four basic classes-continual, subannual, annual, and supra-annual-are applied to patterns at any level of analysis. The classification system provides a logical framework for quantitative description of phenological behavior leading to more standardized comparisons. Thus we can see that tropical phenology differs from temperate phenology in two major ways. In tropical species, the nature of the pattern may change from one level of analysis to the next, which is not typical of temperate species. In many tropical species, phenological patterns vary more widely over the geographic range of a species than they do in temperate species.

Comparative Phenological Studies of Trees in Tropical Wet and Dry Forests in the Lowlands of Costa Rica

Article

Nov 1974

During 1969-70, 185 tree species at a Wet forest site and 113 species at a Dry forest site in Costa Rica were systematically observed for changes in leafing, flowering and fruiting. (1) At the Wet forest site, the greatest amount of leaf fall in the overstorey and understorey trees occurred primarily during the first (more severe) dry season. At that time, 17% of the tree species from both storeys lost leaves. (2) At the Dry forest site, the period of greatest leaf fall coincided with the long dry period; at that time 75% of the species lost leaves. (3) Most Wet forest species flushed large quantities of new leaves during the first dry season. This was in contrast to the Dry forest site where most species flushed leaves at the onset of the first rainy season. (4) Two apparent flowering peaks in the overstorey tree species and three apparent flowering peaks in the understorey tree species were recorded during the year at the Wet forest site. These major flowering periods in both layers occurred during wet as well as dry seasons, and two of the peak periods of the overstorey appeared to be out of phase with two of the understorey. The species at the Wet forest site were well represented by both `seasonal' and `extended' flowering species. (5) At the Dry forest site, two peak periods of flowering activity were recognized. One extensive period occurred during the long dry season and a second peak period was recorded at the onset of the rainy season. Most species were of a `seasonal' rather than `extended' flowering nature. (6) With regard to Wet forest fruiting, substantial numbers of species (at least 37) from both storeys were in mature fruit during each month, but a peak in fruiting occurred in both layers during the second dry season (August-October); the fruiting peaks of the two storeys were separated by one month. The disseminules of most Wet forest species were not adapted for wind dispersal. (7) A peak period in the production of mature fruit occurred during the latter part of the long dry season at the Dry forest site. A significant proportion (31%) of the Dry forest species had disseminules adapted for wind dispersal. (8) When phenological patterns of vicarious species of the two forests were compared, only flowering patterns showed similarity (11/27 species). Leafing and fruiting patterns of vicarious species tended to follow the general trends of the respective forest ecosystems. (9) Periodicity patterns of most species in common between the two forest sites were similar. (10) The phenological patterns recorded are discussed in relation to climatic `triggers' (proximate factors) and plant-animal interactions (ultimate factors).

Soil and Stem Water Storage Determine Phenology and Distribution of Tropical Dry Forest Trees

Article

Jul 1994

Rolf Borchert

Many trees of tropical dry forests flower or form new shoots soon after leaf shedding during the dry season, i.e., during a period when trees are likely to be severely water stressed. To resolve this apparent paradox, phenology and seasonal changes in tree water status was monitored during two consecutive dry seasons in >150 trees of 37 species growing at different sites in the tropical dry lowland forest of Guanascaste, Costa Rica. Tree development during the dry season varied considerably between species and between sites of different moisture availability. Leaf shedding, flowering, and shoot growth (flushing) were strongly correlated with seasonal changes in tree water status, measured by conventional and newly developed techniques. Tree water status varied with the availability of subsoil water and a variety of biotic factors such as structure and life-span of leaves, time of leaf shedding, wood density and capacity for stem water storage, and depth and density of root systems. Observed tree species differed widely in wood density (from 0.19 to 1.1. g/cm^3) and stem water storage capacity (400-20% of dry mass), which was highly correlated with the degree of desiccation during drought. Only hardwood trees at dry upland sites, lacking stem water storage and access to subsoil water, desiccated strongly (stem water potential

Direct foliar absorption of rainfall water and its biological significance in dryland ecosystems

Article

Mar 2010

Sergi Munné-Bosch

Climatic Periodicity, Phenology, and Cambium Activity in Tropical Dry Forest Trees

Article

Jan 1999

Rolf Borchert

The seasonal time course of vegetative phenology and cambium growth is compared for tree species from Central America and Asia growing in tropical climates with a long, severe dry season. Although the inhibition of plant growth by water stress is well established, responses to seasonal drought vary widely among such trees, and their annual development is not well synchronized by climatic seasonality. In deciduous trees growing at microsites with low soil moisture storage, phenology and cambium growth are well correlated with each other and with seasonal rainfall, and most trees have distinct annual rings. Phenology and cambium growth are progressively uncoupled from climatic seasonality in brevideciduous and evergreen trees growing at microsites with large soil water reserves which buffer trees against seasonal drought and thus may prevent the formation of distinct annual rings. There is some experimental evidence concerning the control of growth initiation in apical meristems and the cambium, but little is known about the mechanisms which arrest growth and determine qualitative changes in organ development and cambium cell differentiation.

Leaf Phenology of Woody Species in a North Australian Tropical Savanna

Article

Dec 1997

Leaf phenology was monitored for 49 woody species (trees and tall shrubs) each month over a 2.5-year period in a humid, wet-dry tropical eucalypt savanna at Solar Village, near Darwin, Australia. In the 10 most common species, which spanned the range of phonological types, phenology was monitored every two weeks. To investigate the re- lationships between leaf phonology and plant water status, pre-dawn leaf water potential was monitored in eight common species every 4-6 weeks. Four main phonological types were described: (1) evergreen species, which retained full canopy throughout the year; (2) brevi- or partly deciduous species, in which the amount of canopy fell significantly, but briefly, during at least one dry season during the study period, but to levels not below 50% of full canopy; (3) semideciduous species in which canopy fell to below 50% of full canopy in each of the dry seasons; and (4) fully deciduous species, which lost all leaves during the early-mid dry season, and remained leafless for at least one month. Of these 49 species, 24% were evergreen, 20% were brevideciduous, 29% were semideciduous, and 27% were fully deciduous. Leaf fall occurred 1-2 months earlier in the dry season for the fully deciduous species than for the semideciduous species. Leaf fall in all species was coincident with the attainment of seasonal minima in leaf water potential, which were, on average, about -1.5 to -2.0 MPa in the evergreen and semideciduous species, compared with about -0.5 to -1.0 MPa in the fully deciduous species. Leaf flushing occurred throughout the dry season in the two evergreen species, with a major peak in the late dry season. In five semideciduous species and one of the fully deciduous species, leaf flushing commenced in the late dry season prior to the occurrence of any rain. In two fully deciduous species, leaf flushing occurred only after the first storms of the early wet season. There was variation in the timing of flushing, both between species within years and between years for some species. However, all species commenced leaf flushing after water potentials rose, following the attainment of seasonal minima in pre-dawn leaf water potential. Soil moisture at 1 m did not fall below permanent wilting point during the dry season; hence, reserves of soil water at the end of the dry season were sufficient to support the whole-plant rehydration that preceded leaf flushing in the absence of rain. These results are consistent with hypotheses, developed in the neotropics, that leaf phenology in trees from the wet-dry tropics is largely controlled by endogenous mechanisms.

Fruiting phenology and seed dispersal syndromes in Caatinga, a tropical dry forest in the northeast of Brazil

Article

Mar 2001
J TROP ECOL

This study describes the fruiting phenology of woody plants and their dispersal syndromes in caatinga (semi-arid region in the northeast of Brazil). The fruiting phenology of 42 species with different dispersal modes and life-forms was followed over a period of 1 y. Animal dispersal was the most commonly observed dispersal mode (36%), followed by anemochory (33%), ballistic dispersal (19%) and barochory (12%). Overall, a greater number of species fruited during the rainy season. Zoochorous species were the most representative in the rainy season, whereas anemochorous species predominated during the dry season. Five different life-forms were observed, and the occurrence of dispersal modes was discussed for each of them. In the caatinga plant community studied the patterns of life-forms, fruiting phenology and seed dispersal syndromes were similar to other tropical seasonal ecosystems.

Modification of Vegetative Phenology in a Tropical Semi‐deciduous Forest by Abnormal Drought and Rain1

Article

Mar 2006
BIOTROPICA

The control of vegetative phenology in tropical trees is not well understood. In dry forest trees, leaf abscission may be enhanced by advanced leaf age, increasing water stress, or declining photoperiod. Normally, it is impossible to dissect the effects of each of these variables because most leaves are shed during the early dry season when day length is near its minimum and leaves are relatively old. The 1997 El-Niño Southern Oscillation caused a ten-week long, severe abnormal drought from June to August in the semi-deciduous forests of Guanacaste, Costa Rica. We monitored the effect of this drought on phenology and water status of trees with young leaves and compared modifications of phenology in trees of different functional types with the pattern observed during the regular dry season. Although deciduous trees at dry sites were severely water stressed (Ψstem < -7MPa) and their mesic leaves remained wilted for more than two months, these and all other trees retained all leaves during the abnormal drought. Many trees exchanged leaves three to four months earlier than normal during the wet period after the abnormal drought and shed leaves again during the regular dry season. Irrigation and an exceptional 70 mm rainfall during the mid-dry season 1998/1999 caused bud break and flushing in all leafless trees except dormant stem succulents. The complex interactions between leaf age and water stress, the principal determinants of leaf abscission, were found to vary widely among trees of different functional types.

Phenological patterns in monsoon rainforests in the Northern Territory, Australia

Article

Sep 2002
AUSTRAL ECOL

Christine Susanne Bach

Abstract Monsoon rainforests occur as scattered patches within a landscape dominated by eucalypt savannas across the wet–dry tropics of northern Australia. This study formed part of a larger project that investigated the interactions between frugivores and monsoon rainforest patches in the Top End of the Northern Territory. Phenological patterns in a set of 12 wet monsoon forests (WMF) and four dry monsoon forests (DMF) were examined by monitoring individuals of more than 100 species over 30 months. Phenological patterns of both WMF and DMF were closely related to the strongly seasonal climate. Leaf flush occurred before the onset of the wet season in WMF, and coincided with the onset of the wet in DMF. Major flowering peaks coincided with leaf flush in both forest types. Fruiting was concentrated in the wet season in both forest types, but fruiting peaks of WMF and DMF were separated by 3–4 months. Variations in fruiting patterns among forest types, patches, seasons and groupings of plant species (based on life form and ecological positioning) provide a mosaic of food resources for frugivores. This has important implications for the conservation and maintenance of the frugivore–rainforest system in northern Australia.

The contribution of fog to the water relations of Sequoia sempervirens (D. Don): Foliar uptake and prevention of dehydration

Article

Jun 2004
PLANT CELL ENVIRON

Fog is a defining feature of the coastal California redwood forest and fog inputs via canopy drip in summer can constitute 30% or more of the total water input each year. A great deal of occult precipitation (fog and light rain) is retained in redwood canopies, which have some of the largest leaf area indices known (Westman & Whittaker, Journal of Ecology 63, 493–520, 1975). An investigation was carried out to determine whether some fraction of intercepted fog water might be directly absorbed through leaf surfaces and if so, the importance of this to the water relations physiology of coast redwood, Sequoia sempervirens. An array of complimentary techniques were adopted to demonstrate that fog is absorbed directly by S. sempervirens foliage. Xylem sap transport reversed direction during heavy fog, with instantaneous flow rates in the direction of the soil peaking at approximately 5–7% of maximum transpiration rate. Isotopic analyses showed that up to 6% of a leaf's water content could be traced to a previous night's fog deposition, but this amount varied considerably depending on the age and water status of the leaves. Old leaves, which appear most able to absorb fog water were able to absorb distilled water when fully submersed at an average rate of 0.90 mmol m2 s−1, or about 80% of transpiration rates measured at the leaf level in the field. Sequoia sempervirens has poor stomatal control in response to a drying atmosphere, with rates of water loss on very dry nights up to 40% of midday summer values and rates above 10% being extremely common. Owing to this profligate water use behaviour of S. sempervirens, it appears that fog has a greater role in suppressing water loss from leaves, and thereby ameliorating daily water stress, than in providing supplemental water to foliar tissues per se. Although direct foliar absorption from fog inputs represents only a small fraction of the water used each day, fog's in reducing transpiration and rehydrating leaf tissues during the most active growth periods in summer may allow for greater seasonal carbon fixation and thus contribute to the very fast growth rates and great size of this species.

Environmental control of flowering periodicity in Costa Rican and Mexican tropical dry forests

Article

Sep 2004
GLOBAL ECOL BIOGEOGR

Aim We analyse the proximate causes of the large variation in flowering periodicity among four tropical dry forests (TDF) and ask whether climatic periodicity or biotic interactions are the ultimate causes of flowering periodicity. Location The four TDFs in Guanacaste (Costa Rica), Yucatan, Jalisco and Sonora (Mexico) are characterized by a 5–7 month long dry season and are located along a gradient of increasing latitude (10–30°N). Methods To dissect the differences in flowering periodicity observed at the community level, individual tree species were assigned to ‘flowering types’, i.e. groups of species with characteristic flowering periods determined by similar combinations of environmental flowering cues and vegetative phenology. Results Large variation in the fraction of species and flowering types blooming during the dry and wet season, respectively, indicates large differences in the severity of seasonal drought among the four forests. In the dry upland forests of Jalisco, flowering of leafless trees remains suppressed during severe seasonal drought and is triggered by the first rains of the wet season. In the other forests, leaf shedding, exceptional rainfall or increasing daylength cause flowering of many deciduous species at various times during the dry season, well before the summer rains. The fraction of deciduous species leafing out during the summer rains and flowering when leafless during the dry season is largest in the Sonoran TDF. Main conclusions In many wide-ranging species the phenotypic plasticity of flowering periodicity is large. The distinct temporal separation of spring flowering on leafless shoots and subsequent summer flushing represents a unique adaptation of tree development to climates with a relatively short rainy season and a long dry season. Seasonal variation in rainfall and soil water availability apparently constitutes not only the proximate, but also the ultimate cause of flowering periodicity, which is unlikely to have evolved in response to biotic adaptive pressures.

Strategy shifts in leaf physiology, structure and nutrient content between species of high- and low-rainfall and high- and low-nutrient habitats

Article

Dec 2001
FUNCT ECOL

1. Relationships were examined among photosynthetic capacity (Amass and Aarea), foliar dark respiration rate (Rd-mass and Rd-area), stomatal conductance to water (Gs), specific leaf area (SLA), and leaf nitrogen (N) and phosphorus (P) across 79 perennial species occurring at four sites with contrasting rainfall levels and soil nutrients in eastern Australia. We hypothesized that the slope of log-log 'scaling' relationships between these traits would be positive and would not differ between sites, although slope elevations might shift between habitat types. 2. Amass, Rd-mass, SLA, Nmass and Pmass were positively associated in common slopes fitted across sites or rainfall zones, although rather weakly within individual sites in some cases. The relationships between Amass (and Rdmass) with each of Nmass and SLA were partially independent of each other, with Amass (or Rd-mass) increasing with SLA at a given Nmass, or with Nmass at a given SLA (only weakly in the case of Amass). These results improve the quantification and extend the generalization of reported patterns to floras largely unlike those studied previously, with the additional contribution of including phosphorus data. 3. Species from drier sites differed in several important respects. They had (i) higher leaf N and P (per dry mass or area); (ii) lower photosynthetic capacity at a given leaf N or P; (iii) higher Rd-mass at a given SLA or Amass; and (iv) lower Gs at a given Aarea(implying lower internal CO2concentration). 4. These trends can be interpreted as part of a previously undocumented water conservation strategy in species from dry habitats. By investing heavily in photosynthetic enzymes, a larger drawdown of internal CO2 concentration is achieved, and a given photosynthetic rate is possible at a lower stomatal conductance. Transpirational water use is similar, however, due to the lower-humidity air in dry sites. The benefit of the strategy is that dry-site species reduce water loss at a given Aarea, down to levels similar to wet-site species, despite occurring in lower-humidity environments. The cost of high leaf N is reflected in higher dark respiration rates and, presumably, additional costs incurred by N acquisition and increased herbivory risk.

Convergence towards higher leaf mass per area in dry and nutrient-poor habitats has different consequences for leaf life span

Article

May 2002
J ECOL

1. Leaf life span (LL) and leaf mass per area (LMA) are fundamental traits in the carbon economy of plants, representing the investment required per unit leaf area (LMA) and the duration of the resulting benefit (LL). Species on dry and infertile soils converge towards higher LMA. It has been generally assumed that this allows species from low-resource habitats to achieve longer average leaf life spans, as LMA and LL are often correlated. 2. Leaf life span and LMA were measured for 75 perennial species from eastern Australia. Species were sampled from nutrient-rich and nutrient-poor sites within high and low rainfall regions. LL and LMA were positively correlated across species within each site. In addition, evolutionary divergences in LL and LMA were correlated within each site, indicating that cross-species relationships were not simply driven by differences between higher taxonomic groups. 3. Within a rainfall zone, LL-LMA combinations shifted as expected along common axes of variation such that species on poorer soils had higher LMA and longer LL, but significantly so only at high rainfall. 4. Low rainfall species were expected to have shorter LL at a given LMA or, equally, require higher LMA to achieve a given LL, i.e. shift to a parallel axis of variation, and this was observed on both nutrient-rich and nutrient-poor soils. On average, 30% higher LMA was seemingly required at dry sites to achieve a given LL. Thus, convergence towards higher LMA has different consequences for leaf life span in dry and nutrient-poor habitats. 5. The broad shifts in LL-LMA combinations between site types were also seen when comparing closely related species-pairs (phylogenetically independent contrasts) occurring on nutrient-rich and nutrient-poor soils (within each rainfall zone), and at high- and low-rainfall sites (at each soil nutrient level).

Phenology of Caatinga Species at Serra Talhada, PE, Northeastern Brazil

Article

Mar 1997
BIOTROPICA

The phenology of 19 species of plants was followed for two years at Serra Talhada, Pernambuco State, Northeastern Brazil. Ten plants of each species were monitored biweekly. All plants had a complete canopy cover from February (well established rainy season) until May‐June (just after rains ceased), and all but a few individuals, belonging to six species, were leafless in October‐November (peak of the dry season). Leaf fall and flush, flowering, and fruiting were almost continuous in the community throughout both the years, but they peaked at different periods. The peak of leaf flush preceded the rainy season, spurred by occasional rains, followed by flowering early in the rainy season, and then fruiting. Leaf fall became more pronounced after the rainy season. The species covered a whole range of deciduousness, from those which retained their leaves throughout both years to those which were leafless during 6–7 months each year. This was mostly due to the capacity of leaf retention after the onset of the dry season. Autochoric and zoochoric species produced fruits mostly during the rainy season and anemochoric species during the dry period. The patterns of flowering and fruiting were complex. One species did not produce flowers or fruits in either year; five produced flowers and fruits in one year only and two others produced flowers in both years but fruits in only one. Most of the other species had high intraspecific synchrony and produced flowers for a shorter period than fruits. RESUMEN A fenologia de 19 espécies de plantas foi acompanhada por dois anos, em Serra Talhada, PE. Dez plantas de cada espécie foram observadas a intervalos de duas semanas. Todas as plantas tinham a copa completa de fevereiro (estação chuvosa bem estabelecida) a maio—junho (logo após o término das chuvas) e todas, com exceção de poucos individuos pertencentes a seis especies, estavam sem foihas em outubro–novembro (auge da estação seca). Queda e formação de folhas novas, floração e frutificação foram quase continuas na comunidade, durante 0s dois anos, mas com picos em períodos diferentes. 0 pic0 de formação de folhas precedeu a estação chuvosa, impulsionado por chuvas esporádicas, seguido do de floração, no início da estação de chuvas, e depois pelo de frutificação. Queda de folhas foi mais pronunciada depois do período chuvoso. As espécies cobriram toda ma gama de caducifolia, desde as que mantiveram as folhas durante 0s dois anos ás que ficaram defoliadas durante 6–7 meses cada ano. Isto deveuse, principalmente, ás suas capacidades de reter folhas ao longo da estação sea. Espécies autoóricas e zoocóricas produziram frutos principalmente no período chuvoso e as espécies anemocóricas no período seco. Os padrões de floração e frutificação foram complexos. Uma espécie não produziu flores ou frutos nos dois anos, cinco produziram flores e frutos apenas em um dos anos e duas outras, em urn dos anos, produziram flores que não se desenvolveram em frutos. A maioria das outras espécies teve alta sincronia intra‐específica e produziu flores por urn período mais curto que frutos.

Phenology of Tree Species in Bolivian Dry Forests

Article

Jun 2000
BIOTROPICA

Phenological characteristics of 453 individuals representing 39 tree species were investigated in two dry forests of the Lomerío region, Department of Santa Cruz, Bolivia. The leaf, flower, and fruit production of canopy and sub-canopy forest tree species were recorded monthly over a two-year period. Most canopy species lost their leaves during the dry season, whereas nearly all sub-canopy species retained their leaves. Peak leaf fall for canopy trees coincided with the peak of the dry season in July and August. Flushing of new leaves was complete by November in the early rainy season. Flowering and fruiting were bimodal, with a major peak occurring at the end of the dry season (August–October) and a minor peak during the rainy season (January). Fruit development was sufficiently long in this forest that fruiting peaks actually tended to precede flowering peaks by one month. A scarcity of fruit was observed in May, corresponding to the end of the rainy season. With the exception of figs (Ficus), most species had fairly synchronous fruit production. Most canopy trees had small, wind dispersed seeds or fruits that matured during the latter part of the dry season, whereas many sub-canopy tree species produced larger animal- or gravity-dispersed fruits that matured during the peak of the rainy season. Most species produced fruit annually. Lomerío received less rainfall than other tropical dry forests in which phenological studies have been conducted, but rainfall can be plentiful during the dry season in association with the passage of Antarctic cold fronts. Still, phenological patterns in Bolivian dry forests appear to be similar to those of other Neotropical dry forests.

Trends in wood density and structure are linked to prevention of xylem implosion by negative pressure

Article

Feb 2001

Wood density (D t), an excellent predictor of mechanical properties, is typically viewed in relation to support against gravity, wind, snow, and other environmental forces. In contrast, we show the surprising extent to which variation in D t and wood structure is linked to support against implosion by negative pressure in the xylem pipeline. The more drought-tolerant the plant, the more negative the xylem pressure can become without cavitation, and the greater the internal load on the xylem conduit walls. Accordingly, D t was correlated with cavitation resistance. This trend was consistent with the maintenance of a safety factor from implosion by negative pressure: conduit wall span (b) and thickness (t) scaled so that (t/b)2 was proportional to cavitation resistance as required to avoid wall collapse. Unexpectedly, trends in D t may be as much or more related to support of the xylem pipeline as to support of the plant.

Phenology and wood density of plants growing in the semi-arid region of Northeastern Brazil

Abstract

No full-text available

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