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Tropical forest recovery: Legacies of human impact and natural disturbances
Abstract
Land-use history interacts with natural forces to influence the severity of disturbance events and the rate and nature of recovery processes in tropical forests. Although we are far from an integrated view of forest recovery processes, some generalizations can be made. Recovery of forest structure and composition is relatively rapid following disturbances that primarily impact forest canopies, such as hurricanes. Recovery is considerably slower following disturbances that heavily impact soils as well as aboveground vegetation, such as bulldozing, heavy or long-term grazing, and severe fires, often with long-lasting effects on species composition. The landscape matrix plays a critical role in local recovery processes. Proximity of disturbed areas to remnant forest patches promotes more rapid recovery, which depends heavily on seed dispersal. Recovery of aboveground biomass is constrained by soil fertility and texture across regions as well as across soil types within a region. Restoration of soil fertility may be a prerequisite for forest recovery on sites with severely degraded soils. Despite evidence of rapid forest recovery following large-scale deforestation, many degraded areas of today's tropics will require human assistance to recover forest structure, species composition, and species interactions typical of mature tropical forests.
... Hurricanes are an important disturbance that reduce aboveground biomass (AGB) (Uriarte et al., 2019;Zhang et al., 2022aZhang et al., , 2022b, and in the long term affect the biodiversity, species interactions, spatiotemporal dynamics of populations and communities, and biogeochemical cycling of coastal tropical forests (Brokaw et al., 2012;Chazdon, 2003;Heartsill-Scalley, 2017;Walker, 2012;Zhang et al., 2022aZhang et al., , 2022bZimmerman et al., 2021). Heavy precipitation from hurricanes results in soil saturation, which makes uprooting happen more easily (Xi, 2015;Xi et al., 2008), and induces landslides (Arnone et al., 2011(Arnone et al., , 2015Lepore et al., 2012Lepore et al., , 2013. ...
... Although ELM-FATES-predicted posthurricane DBH increment and stem density do not match the observations, the result shows the sensitivity of forest structure and dynamics to canopy biomass changes (i.e., canopy openings) in ELM-FATES. During the posthurricane period, ELM-FATES-simulated DBH increment rates are within the observed DBH increment ranges in tropical forests (Brienen & Zuidema, 2006;Clark & McLachlan, 2003, 2003, 2003Lai et al., 2022), but are faster for both the light-demanding and shade-tolerant PFTs compared to the observations at Bisley. Note that the regeneration scheme in ELM-FATES suggests a weak limitation of recruitment and seeding processes (Hanbury-Brown et al., 2022), and these processes are more important to small trees (i.e., DBH < 20 cm) than to large trees (Zhang et al., 2022b). ...
... Although ELM-FATES-predicted posthurricane DBH increment and stem density do not match the observations, the result shows the sensitivity of forest structure and dynamics to canopy biomass changes (i.e., canopy openings) in ELM-FATES. During the posthurricane period, ELM-FATES-simulated DBH increment rates are within the observed DBH increment ranges in tropical forests (Brienen & Zuidema, 2006;Clark & McLachlan, 2003, 2003, 2003Lai et al., 2022), but are faster for both the light-demanding and shade-tolerant PFTs compared to the observations at Bisley. Note that the regeneration scheme in ELM-FATES suggests a weak limitation of recruitment and seeding processes (Hanbury-Brown et al., 2022), and these processes are more important to small trees (i.e., DBH < 20 cm) than to large trees (Zhang et al., 2022b). ...
In the past three decades, Puerto Rico (PR) experienced five hurricanes that met or exceeded category three, and they caused severe forest structural damage and elevated tree mortality. To improve our mechanistic understanding of hurricane impacts on tropical forests and assess hurricane‐affected forest dynamics in Earth system models, we use in situ forest measurements at the Bisley Experimental Watersheds in Northeast PR to evaluate the Functionally Assembled Terrestrial Ecosystem Simulator coupled with the Energy Exascale Earth System Model Land Model (ELM‐FATES). The observations show that before Hurricane Hugo, 77.3% of the aboveground biomass (AGB) is from the shade‐tolerant plant function type (PFT). The Hugo‐induced mortality rates are over ∼50%, and they induce a ∼39% AGB reduction, which recovers to a level like the pre‐Hugo condition in 2014, following a second, lower intensity hurricane, Georges. We perform numerical experiments that simulate damage from Hugo and Georges on the forests, including defoliation, sapwood and structural biomass damage, and hurricane‐induced mortality. ELM‐FATES can reasonably represent coexistence between the two PFTs–light‐demanding and shade‐tolerant–for both the pre‐Hugo and post‐Hugo conditions. The model represents a reasonable size distribution of mid‐and large‐sized trees although it underestimates AGB, likely due to the overestimated nonhurricane mortality. ELM‐FATES temporarily stimulated leaf biomass and diameter increment after Georges, an effect that should be tested with observations of future hurricane defoliation events. This research indicates that addressing model‐data mismatches in tree mortality and understory dynamics are essential to simulation of more extreme hurricane effects under climate change.
... The impact of mining on the soil influences the type of ecological succession (primary or secondary) and the time required for aboveground biomass (AB) recovery in the ecosystem (Chazdon, 2003). Specifically, the differences in AB recovery between miningaffected areas and those impacted by other disturbances are determined by the type of succession that follows the disturbance Guariguata & Ostertag, 2001). ...
... In addition to soil nutrients, sandy soil texture negatively influenced aboveground biomass. This result is similar to that reported by Johnson et al. (2000), who showed that aboveground biomass accumulation on nutrient-poor sandy soils is lower than on non-sandy soils in secondary forests, which evidences the joint influence of soil fertility, texture, and moisture retention on succession (Chazdon, 2003;Johnson et al., 2000). Possibly, in abandoned mines, the greater macroporosity of the sand facilitates the leaching of nutrients, which favors a lower accumulation of aboveground biomass, as denoted in this study. ...
... Then, they tend to decrease their edaphic concentration in the advanced successional stages. This is undoubtedly because plants with progress in succession tend to store nutrients (K, Mg, and Ca) in their aboveground biomass (Feldpausch et al., 2004) as a strategy to reduce their losses by edaphic leaching and thus a way to make nutrient recycling more efficient (Chazdon, 2003;Guariguata & Ostertag, 2001). ...
Introduction:
Mining is one of the main drivers of deforestation of tropical forests. This activity affects the storage of aboveground biomass of these ecosystems; therefore, their ability to contribute to the mitigation of global climate change.
Objective:
To assess the influence of soil properties on the aboveground biomass storage of post-mining forests in the Colombian Pacific.
Methods:
Plots were established in areas post-mining and with different successional ages (12-15 years, 30-35 years, and mature forest). The aboveground biomass and physicochemical parameters of the soil were measured.
Results:
An aboveground biomass of 15.58 t ha⁻¹, 35.17 t ha⁻¹, and 178.32 t ha⁻¹ was recorded at 12-15 years, 30-35 years, and mature forests, respectively. The species with the highest biomass content in post-mining forests were Cespedesia spathulata and Clidemia septuplinervia. The aboveground biomass was positively correlated with organic matter (OM), calcium (Ca), magnesium (Mg), CICE, total nitrogen (N), and silt. In contrast, the relationship was negative with sand, aluminum (Al), and potassium (K) content. It was evidenced that the relationship between aboveground biomass and soils differed in each successional age. When evaluating the changes of aboveground biomass and soils in the succession, it was observed that the aboveground biomass and total N increased with the recovery time. At the same time, the P and K decreased with succession. On the other hand, the contents of OM, Mg, Al, Ca, and CICE showed curvilinear tendencies since they increased in the first stages and then decreased in the advanced successional stages.
Conclusions:
Aboveground biomass increases with forest recovery time in the study area. This increase is influenced by the presence of two dominant species shared among the investigated ecosystems and by the soil’s N, P, and K content.
... They also play a significant role in global carbon cycles (Achard et al., 2014) and hold considerable conservation value. While tropical secondary forests can recover animal species diversity within 20-40 years (Dunn, 2004), they typically support fewer tree species than old-growth forests (Chazdon, 2003;Lugo & Helmer, 2004). The species composition of plant and animal communities often differs between secondary and old-growth forests (Dunn, 2004;Chazdon, 2003;Lugo & Helmer, 2004), with weedy species becoming more widespread and homogenizing species composition over large areas. ...
... While tropical secondary forests can recover animal species diversity within 20-40 years (Dunn, 2004), they typically support fewer tree species than old-growth forests (Chazdon, 2003;Lugo & Helmer, 2004). The species composition of plant and animal communities often differs between secondary and old-growth forests (Dunn, 2004;Chazdon, 2003;Lugo & Helmer, 2004), with weedy species becoming more widespread and homogenizing species composition over large areas. The long-term conservation value of secondary forests depends on the proportion of species restricted to old-growth habitats. ...
The study examines the comparative analysis of soil seed bank in two secondary forests; Unizik Conservation Forest and Orebe Village Forest in Amansea both located in Awka North and South Local Government Areas of Anambra State, Nigeria. These forests are crucial for biodiversity conservation and ecosystem restoration, particularly in the face of increasing deforestation and land-use changes. Through ecological surveys, soil sampling, and seed bank analysis, this research assesses soil properties, species composition, and seed bank diversity to evaluate their potential for regeneration and long-term sustainability. Results indicate that species composition analysis reveals a diverse assemblage of plant families, with Asteraceae, Euphorbiaceae, Fabaceae, and Rubiaceae being dominant in both forests. Seed bank analysis at varying soil depths highlights the resilience and regenerative capacity of the forests, with dominant species such as Ageratum conyzoides and Eleusineindica playing a significant role in forest recovery. The Sørensen Similarity Index (SSI) values indicate a moderate to high level of species similarity between the two forests, suggesting shared ecological conditions. The findings underscore the importance of maintaining soil health and seed bank diversity for sustainable forest management. This study provides essential data for conservation planning, emphasizing targeted interventions to enhance soil fertility, biodiversity, and ecosystem resilience in secondary tropical forests.
... Our focus on NDVI aimed to establish a foundation for future investigations that could utilize advanced remote-sensing technologies to explore specific vegetation characteristics, such as LiDAR or airborne laser scanning [36,105,106]. Recovery metrics based on remote sensing are particularly relevant for planning and managing conservation areas, as they inform adaptive management practices by identifying regions where post-disturbance recovery is slow or incomplete [107,108]. In our calculation of the recovery index, we chose to use the NDVI from year o instead of the immediate post-fire NDVI from year zero. ...
... Our focus on NDVI aimed to establish a foundation for future investigations t could utilize advanced remote-sensing technologies to explore specific vegetation char teristics, such as LiDAR or airborne laser scanning [36,105,106]. Recovery metrics ba on remote sensing are particularly relevant for planning and managing conservation eas, as they inform adaptive management practices by identifying regions where po disturbance recovery is slow or incomplete [107,108]. ...
Wildfires and drought stressors can significantly limit forest recovery in Mediterranean-type ecosystems. Since 2010, the region of central Chile has experienced a prolonged Mega Drought, which intensified into a Hyper Drought in 2019, characterized by record-low precipitation and high temperatures, further constraining forest recovery. This study evaluates short-term (5-year) post-fire vegetation recovery across drought gradients in two types of evergreen sclerophyllous forests and a thorny forest and shrubland, analyzing Landsat time series (1987–2022) from 42 wildfires. Using the LandTrendr algorithm, we assessed post-fire forest recovery based on NDVI changes between pre-fire values and subsequent years. The results reveal significant differences in recovery across drought gradients during the Hyper Drought period, among the three forest types studied. The xeric forest, dominated by Quillaja saponaria and Lithrea caustica, showed significant interaction effects between levels of drought and fire severity, while the thorny forest and shrubland displayed no significant interaction effects. The mesic forest, dominated by Cryptocarya alba and Peumus boldus, exhibited additional significant differences in recovery between the Hyper Drought and Mega Drought periods, along with significant interaction effects. These findings underscore the critical role of prolonged, severe drought in shaping forest recovery dynamics and highlight the need to understand these patterns to improve future forest resilience under increasingly arid conditions.
... Shifting agriculture is responsible for 90% of all farms worldwide, and throughout the regions, 60% of all arable lands are unevenly distributed (Chazdon, 2003). Various tropical countries still practice shifting cultivation, slash, and burn agriculture as a form of subsistence agriculture. ...
... A shifting cultivation system results in land abandonment followed by secondary forest succession (Mertz, 2002). Small-scale abandoned farmlands were related to faster forest recovery of native ecosystems than other agricultural clearings (Chazdon, 2003;Queiroz et al., 2014). Slash and burn farming, for example, is practiced worldwide and has been the mainstay of subsistence for indigenous communities in Guyana. ...
An intelligent method of shifting cultivation to regenerate vegetation after a long fallow period is critical information for restoration strategies. The literature review identified that the assessment of woody plant species on abandoned farmland has never been done before in Kamwatta, Moruca Region 1. In addition, more information should be available in indigenous communities and at the national level, including more documentation of the utilization of natural resources by the Warrau community. This study assessed the valuable woody plant species that grew during the fallow periods. Nine farmlands were randomly selected along a 100 m transect, each with varying fallow periods. In order to collect information on the age of farm abandonment, the researcher employed a mixed-methods approach. First, we found how long each farm had been fallow by administering a semi-structured questionnaire. Then, we conducted a flora survey to gain information on the variety and abundance of valuable plants using the age of farm abandonment as a dependent variable. The data analysis included the number of valuable woody trees with a diameter of >10 cm, seedlings and saplings with a diameter of <10 cm, the location of identified trees, and the uses of identified tree species. Micro-soft Excel was used to code and analyze the questionnaire, while QGIS, Shannon's Index of Diversity, and Simple Linear Regression were used to analyze the inventory data. The results showed that the respondents listed 38 valuable woody species, and 79% occurred in the studied area. The field verification revealed that the dominant family in the area was Mimosaceae. Species abundance increased with fallow up to 10 years before declining in the latter years. Plant diversity and abundance had a weak relationship with the age of abandoned farmlands for woody trees, while the seedlings and saplings showed no relationship.
... Secondary forests are an important feature of tropical landscapes, covering more area than mature forests [1]. In the Neotropics, these forests are increasing in area and value, acting as habitat refugia and biodiversity reservoirs [1][2][3][4], commercial sources of timber and non-timber forest product [5][6][7], and sinks for anthropogenic carbon emissions [8,9]. Tropical secondary forests have until recently been poorly studied, and unifying principles for predicting expected changes along a chronosequence of stand age are lacking. ...
... Although species composition may not recover as rapidly as species richness in tropical forests [3,11,[79][80][81][82], floristic reassembly of understory herbs in northeastern Costa Rica is gradually occurring. Our results are contrary to what has been reported in Singapore, where secondary forests failed to recruit species from adjacent mature forests due to a highly fragmented study area and the extinction of seed-dispersing fauna [80]. ...
Broad-leaved monocot herbs form one of the most common and diverse growth forms of Neotropical plants. Their significance and frequency of occurrence is particularly notable in the understories of tropical rainforests, where they form a dominant element. We assessed and quantified changes in the cover and diversity of understory herb communities in a chronosequence of 1 ha permanent plots established as part of a multidisciplinary study on tropical forest regeneration in the Atlantic lowlands of northeastern Costa Rica. Sampled were two young stands cleared 12 years ago, two secondary forests with 21 and 39 of years of recovery since clearance, and two stands in old-growth primary forest. Changes in species composition during succession were assessed using Chao’s Jaccard similarity index. Observed species richness ranged from 15 to 26 species in individual plots, with the greatest number of species in the 21-year intermediate-age and fewest in the young 12-year plots. Herb species sampled represented 6 families, 15 genera, and 39 species, with the Araceae contributing the largest number of species. Ten species were sampled in all six stands, while fourteen species were found exclusively in one plot. Herb density (ramets m−2) showed a hump-shade trend, with peak density in the intermediate stands and a lower level in mature and young secondary forests. Mean herb cover in 25 m2 quadrats ranged from 2.0% (young stand) to 22.7% (intermediate-age stand) and differed significantly both among stand types and among sites. Both observed and estimated species richness increased along the chronosequence as a whole, with the highest number of species in primary forest, although only slightly higher than in intermediate-age stands. Over half of the species exhibited some degree of clonal growth, with the extent of clonal spread varying among species and forest stands. Although we did not find a clear pattern between clonality and forest age, we observed a greater number of clonal patches in secondary over primary forest stands.
... The conservation value of tropical secondary forests has been debated for decades [12,82,83]. Here, we define a secondary forest as a habitat that has recovered or regenerated largely through natural processes after significant human or natural disturbance (e.g., clearcut logging or hurricanes) that caused a complete removal of the original forest vegetation [82]. ...
Human-caused habitat conversion, degradation, and climate change threaten global biodiversity, particularly in tropical forests where vascular epiphytes-non-parasitic plants growing on other plants-may be especially vulnerable. Epiphytes play vital ecological roles, in nutrient cycling and by providing habitat, but are disproportionately affected by land-use changes due to their reliance on host trees and specific microclimatic conditions. While tree species in secondary forests recover relatively quickly, epiphyte recolonization is slower, especially in humid montane regions, where species richness may decline by up to 96% compared to primary or old-growth forests. A review of nearly 300 pertinent studies has revealed a geographic bias toward the Neotropics, with limited research from tropical Asia, Africa, and temperate regions. The studies can be grouped into four main areas: 1. trade, use and conservation, 2. ecological effects of climate and land-use change, 3. diversity in human-modified habitats, and 4. responses to disturbance. In agricultural and timber plantations, particularly those using exotic species like pine and eucalyptus, epiphyte diversity is significantly reduced. In contrast, most native tree species and shade-grown agroforestry systems support higher species richness. Traditional polycultures with dense canopy cover maintain up to 88% of epiphyte diversity, while intensive management practices, such as epiphyte removal in coffee and cacao plantations, cause substantial biodiversity losses. Conservation strategies should prioritize preserving old-growth forests, maintaining forest fragments, and minimizing intensive land management. Active restoration , including the translocation of fallen epiphytes and planting vegetation nuclei, is more effective than passive approaches. Future research should include long-term monitoring to understand epiphyte dynamics and assess the broader impacts of epiphyte loss on biodiversity and ecosystem functioning.
... The importance of soil moisture is particularly pronounced in tropical forests, where temperature is less limiting and soil microbial activity is primarily moisturedriven (Meir et al. 2008;Schaap et al. 2024). However, past land-use exerts a lasting influence on forest structure and soil properties (Chazdon 2003), which can affect decomposition trajectories over time. ...
Litter decomposition by arthropods, microbes, and fungi is a key ecosystem process in tropical forests, yet its response to forest disturbance and recovery remains poorly understood. To investigate decomposition dynamics across forest succession, we conducted an experiment in the Ecuadorian lowland Chocó (Esmeraldas) using a chronosequence approach. We deployed above- (AG) and belowground (BG) litterbags in 32 plots spanning active cacao plantations and pastures (age 0), secondary forests (1–38 years), and old-growth forest. AG litterbags (5 mm mesh) allowed arthropod access, while BG litterbags restricted decomposition to microbial activity. Each contained standardized leaf litter from five common tree species: Pourouma bicolor, Brosimum utile, Compsoneura atopa, Vochysia macrophylla, and Trema micrantha. Litterbags were collected at three time points, with replacements every 45 days. We examined decomposition drivers by modeling litter mass loss (%) against forest age and environmental factors. AG decomposition was analyzed in relation to tree aboveground biomass, surface temperature, leaf litter biomass, elevation, and terrain slope, while BG decomposition was assessed with soil pH, soil C:N, terrain slope, soil moisture, and soil temperature. Additionally, we tested how small-scale disturbances and large animal exclusion affected decomposition (PREX) using four treatments: control (C), fenced (CF, exclusion of large ground-dwelling animals), perturbed (P, removal of litter and understory vegetation in 100 m²), and perturbed-fenced (PF, combined litter removal and animal exclusion). AG decomposition rates increased with forest succession but followed a U-shaped pattern in plots recovering from cacao land-use, with a mid-succession decline and higher rates in old-growth forests. Key drivers included surface temperature, elevation, and tree aboveground biomass, with temperature varying significantly depending on land-use history. BG decomposition was unaffected by forest age, decreased with C:N, and showed a bell-shaped response to soil moisture. Large animal exclusion (CF) had no effect, whereas perturbation (P, PF) significantly altered decomposition. Notably, decomposition in P plots showed dynamic recovery, whereas in PF plots, mass loss remained suppressed throughout the 135-day study, emphasizing the role of large animals in facilitating ecosystem recovery.
... Sobrinho et al. (2016) reported that Caatinga vegetation cannot recover completely in 15 years following land abandonment. This study, together with earlier studies, agrees that most woody plant assemblages take 20-70 years to recover after land abandonment in the absence of intense habitat degradation or disturbance (Kennard 2002;Chazdon 2003;Lebrija-Trejos et al. 2010;Maza-Villalobos et al. 2011). According to Hamzah (1999), the forest recovery rate in the loggedover forest after harvesting greatly depends on the extent of degradation during forest harvesting. ...
Alias MAB, Rahmani W, Azizi F, Ninchaleune B, Abdu A. 2024. Forest recovery assessment in degraded dry evergreen forestlands in Vientiane Province, Lao People's Democratic Republic. Asian J For 8: 31-40. Shifting cultivation and logging are the significant causes of deforestation and forest degradation in tropical region. Lao PDR has vast shifting cultivation areas, and regrowth forests have spontaneously been established on fallow fields. This study aims to assess the forest recovery through vegetative succession after fallow cultivation and logging in degraded dry evergreen forestlands in Vientiane Province, Lao PDR. Braun-Blanquet method was applied to assess vegetation composition in primary forest, logged-over forest and fallow lands with age of 1-, 5- and 15-year-old. Data obtained from the vegetation study has enabled the community plant identification and forest recovery calculation by various analytical methods using statistical software. Based on the phytosociological analysis, logged-over forests had the highest vegetation composition similarity to primary forests with a similarity of 42.29%, followed by the 15, 5, and 1-year-old fallows with similarity value of 39.90%, 34.80%, and 26.10%, respectively. The three fallows with 1-, 5- and 15-year-old age and two forest types were compared for their canopy structure recovery with each other. The logged-over forest, harvested by wood logging companies and local villagers in the past two decades, recorded the lowest recovery in the canopy structure. The sites of 1-, 5- and 15-year-old fallows have not fully recovered their top layers (ST and T1). Only the T2 layer of the 15-year-old fallow recovered. This indicated that the three fallow types heavily degraded and required a longer time to recover naturally. In conclusion, local authorities should avoid over-using the natural forest in the future and should control timber and non-timber forest products. Alternative land use with integrated land management should be established. Long-term tree planting programs will enable the people to use and own their land.
... Soil plays a significant role in shaping dipterocarp forest communities and plant growth (Paoli, Curran, and Zak 2006). Many tropical species especially dipterocarp grow in highly weathered clay soils, which are acidic and have low nutrient content (Chazdon 2003;Palmiotto et al. 2004;Paoli, Curran, and Zak 2006;Peay et al. 2010). However, the presence of humus content and ectomycorrhizal fungi association in dipterocarp species contributed to tree height and diameter growth by enhancing and retaining the nutrient uptake (Brearley, Press, and Scholes 2003;Ducousso et al. 2004;Baillie et al. 2006;Paoli, Curran, and Zak 2006;Tedersoo et al. 2007). ...
The role of trait evolution in shaping the functional and ecological diversity of tropical forests remains poorly understood. Analyses of trait variation as a function of evolutionary history and environmental variables should reveal the drivers of species distributions, as well as generate insights valuable to conservation. Here, we focus on the Dipterocarpaceae, the key plant family underpinning the hyperdiversity of South‐East Asian tropical forest canopies and of major conservation concern due to over‐exploitation for timber, cultivation, and climate change. Our objectives are to (i) assess whether dipterocarp species traits are phylogenetically conserved through a phylogenetic signal, indicating phylogenetic niche conservatism (PNC); (ii) determine the drivers of dipterocarp species distribution; (iii) examine the relationship between morphological traits with habitat factors; and (iv) assess the correlation between conservation status and phylogeny. We compiled a dataset of species‐level plant traits of the Dipterocarpaceae together with population‐level ecological trends. We found substantial evidence of phylogenetic conservatism of plant traits in dipterocarp species, with a moderate to strong phylogenetic signal, and that the elevational gradient shapes dipterocarp species distribution pan‐tropically. Morphological traits including height and diameter show phylogenetically dependent relationships with soil type, while shade tolerance traits are related to survival. We find that conservation status is related to phylogeny and correlated with population trend status, suggesting that decreasing population trends correlated with conservation status. Overall, our analyses show that functional traits and ecological trends of dipterocarp species are shaped by the phylogenetic history. Our study highlights that conservation strategies require consideration of the consequences of these relationships for long‐term population changes.
... O uso do fogo foi recorrente nessas áreas para a eliminação do material lenhoso, provocando um acúmulo de cinzas nas leiras. Como resultado, em grande parte da área desmatada o maquinário e as queimadas alteraram consideravelmente a camada superficial do solo (Chazdon, 2003). Embora muitos estudos sobre o efeito dos incêndios na savana tenham sido realizados, especialmente em relação à ecologia dessas áreas, poucas pesquisas examinaram os efeitos do fogo empregado durante a conversão das áreas nativas, especialmente sobre o comportamento dos nutrientes do solo (Lal;Ghuman, 1989;Fraser;Scott, 2011;Tavares Filho et al., 2011). ...
... The numerical abundance and varied behaviors of small, omnivorous bird species makes them important seed dispersal vectors both within and among forest habitats (Greenberg, 1981a;Wenny et al., 2016). In consequence, smaller-seeded plants are readily dispersed in regenerating forests and often dominate early successional habitats (Chazdon, 2003). For example, the five most abundant plant species (representing 27% of individuals) are small seeded in 45 early successional forest plots in the Agua Salud landscape adjacent to Parque Nacional Soberanía and the BCNM (Van Breugel et al., 2013). ...
Birds disperse the seeds of up to three-quarters of tropical tree species,
so avian frugivory and seed dispersal are key to determining the future distribution of adult plants and hence maintaining a range of ecosystem services. We collated previously published avian frugivore–plant interaction networks for Barro Colorado Island (BCI), encompassing 299 interactions between 59 bird and 86 plant species. The effects of geographical isolation on BCI’s network structure has probably been relatively minor, with ongoing movements of larger frugivores between BCI and the mainland, and relatively few extirpations of avian frugivores. However, climate change threatens all avian frugivore–plant interaction networks and, in the wider region, networks outside protected areas are vulnerable to habitat disturbance. The loss of large-gaped frugivores in human-modified landscapes likely leads to altered seed dispersal patterns. Only a fraction of the BCI network has been quantified; we have yet to identify the key dispersers for many plant species nor which plants are critical for maintaining avian frugivore populations on the island.
... Improving AGB estimates depends on predictor variables and prediction methods (Lu et al., 2016). In the first case, it is known that numerous variables (e.g., climatic and edaphic) stand out for influencing AGB patterns (Chazdon, 2003;Poorter et al., 2017;Ali et al., 2019). Furthermore, other variables from remote sensing, such as spectral indices and topography, also contribute to a better understanding of the spatial distribution of AGB (Lu et al., 2004;Barbosa et al., 2014;Silveira et al., 2019). ...
The Atlantic Forest stores vast amounts of aboveground biomass (AGB), yet it is still a challenge to estimate these stocks. We aimed to predict the AGB stock of the largest biodiversity remnant of Serra da Tiririca State Park (Rio de Janeiro, Brazil) by comparing the accuracy of generalized linear models (GLM) and random forest (RF) models, using data from field plots, remote sensing, and environmental variables. The plots showed an AGB of 371.12 Mg/ha. The comparison between the modelling methods revealed that the GLM is more accurate, still the RF is also fit to estimate the AGB of the remnant. The most accurate GLM predicted an AGB of 405.31 Mg/ha. We observed that the accuracy of the models improved when all predictor variables were combined. This study allowed us to improve the AGB estimates, and produce an AGB map useful for the management and conservation of the remnant
... Analyzing forest disturbances from the perspective of forest dynamics and resilience offers numerous opportunities, but also presents significant challenges [7,11]. In particular, this approach would allow this definition to be generalized and distinguished from any biases introduced by biased human perspectives [11,93,94]. ...
Forest degradation and forest disturbance are distinct yet often conflated concepts, complicating their definition and monitoring. Forest degradation involves interrupted succession and a severe reduction in forest services over time, caused by factors like fires, illegal selective logging, and edge effects. Forest disturbance, on the other hand, refers to abrupt, localized events, natural or anthropogenic, such as legal selective logging, tropical blowdowns, storms, or fires, without necessarily leading to long-term degradation. Despite the varying intensity and scale of forest degradation and disturbance, systematic studies distinguishing its types and classes are limited. This study reviews anthropogenic impacts on forests in the Brazilian Amazon, analyzing 80 scientific articles using remote sensing techniques and data. Most research focuses on the “arc of deforestation,” characterized by intense human activity, showcasing methodological advancements but also revealing gaps in monitoring less-studied regions like the central and western Amazon. The findings emphasize the need for advanced remote sensing tools to differentiate degradation types, particularly in sustainable forest management (SFM) contexts. Expanding research to underrepresented regions and refining methodologies are crucial for better understanding forest dynamics and improving conservation strategies. These efforts are essential to support effective forest management and informed policy development across the Amazon.
... Human activities have shaped the forests for generations in which species composition, structure, and functioning of secondary forests altered then impacting their biodiversity and ecological processes. Therefore, understanding the impact of anthropogenic factors on secondary forests is crucial for effective conservation and sustainable management of these valuable ecosystems (Chazdon 2003;Pyles et al. 2022;Rosenfield et al. 2022). In the tropics, the tropical secondary forest harbors a diverse group of vegetation and fauna. ...
Marwa J, Ungirwalu A, Imburi CS, Djitmau DA, Murdjoko A, Benu NMH. 2024. Ecological perspective to sustainably manage the secondary forest in the lowland of Doberai Peninsula, Indonesia. Biodiversitas 25: 2720-2732. This research aims to examine the composition of flora and fauna in secondary forests, with the aim of using the results to provide input for sustainable forest management. Suggestions for proper ecological management have been put forward, as they are crucial for preserving ecosystem functions and protecting species. We revealed that the identified area was a secondary forest with a composition of 225 species and 83 families of vegetation. The distribution was fairly uniform, encompassing 6 life forms: ferns, herbs, lianas, palms, shrubs, and trees. For fauna, the result indicated the presence of 10 species of mammalia, 37 species of aves, 6 species of reptiles, and 4 species of insects. The secondary forest still supports a high species richness of vegetation and fauna. These findings suggest that the secondary forest is undergoing a successional process in which various vegetation, particularly lianas and herbs, compete to gain more sunlight due to increased canopy openness. Forest management must optimize multi-factors, as in this research, and we suggest considering development and conservation, utilization of buffer zones, monitoring vegetation and animal breeding, and reforestation. The balance between development and conservation is critical, offering opportunities for sustainable practices and community involvement.
... When crop productivity decreases, cropland is abandoned to allow for forest recovery (Figure 1). The ecological drivers and consequences of this process, as well as the successional trajectories of second-growth forests, have been extensively studied (Figure 4), leading to significant theoretical and empirical advances with considerable practical implications [11,13,24,26,106,107]. ...
Slash-and-burn agriculture (SBA) is critical to maintaining rural peoples' livelihoods. Yet, it causes environmental degradations that challenge its sustainability. Such degradations are often underestimated, as they are usually assessed at the local (stand) scale, overlooking larger-scale impacts. Here, we drew upon existing SBA and landscape ecology knowledge to assess the multiscale abiotic and biotic effects of SBA. This agroecosystem involves four stages (slashing of vegetation, burning of vegetation, farming, and forest recovery) but the SBA research is biased towards biotic impacts, especially during forest recovery. Despite its importance for key abiotic (e.g., soil fertility) and biotic (e.g., species richness) attribute recovery, this stage is typically too short (<10 years) to compensate for the environmental degradation caused by the previous stages. Successional and landscape ecology theory suggests that such compensatory dynamics can promote SBA sustainability in landscapes dominated by old-growth forests. Yet, when old-growth forest loss exceeds certain boundaries, abiotic and biotic SBA impacts may compromise the conservation value and sustainability of this ancient agroecosystem. We highlight that SBA sustainability should be comprehensively assessed by including landscape-scale variables (e.g., percent old-growth forest cover) that may be key for maintaining biodiversity patterns and processes in landscapes where SBA is practiced.
... A.Chev., Lovoa trichilioides Harms, and Daniellia ogea (Harms) Holland, identified in the restoration sites rather than the primary forests, underscores the capacity of these sites to enhance biodiversity conservation at the landscape level. The variability in the pace of regeneration of indigenous plant species in tropical abandoned farmlands or plantations is contingent upon factors such as the specific environment, proximity to sources of propagules, and the intensity of previous land use (Chazdon 2003(Chazdon , 2008Holl, 2007). The origins of these propagules in the context of this study are expected to be primarily from seed dispersal mechanisms such as avian and mammalian (particularly bats) seed rain, wind dispersal, and ballochory. ...
Deforestation and forest degradation in the tropics has resulted in the depletion of vital forest resources and services, the near eradication of suitable habitats for forest fauna and flora, and the impoverishment of human populations reliant on forest ecosystems. The rapid and concerning pace of deforestation in tropical regions calls for urgent and pragmatic steps to tackle the root causes and rehabilitate or restore degraded and deforested landscapes. The aim of the study was to evaluate the effectiveness of old, unmanaged forest plantations compared to similar-aged secondary forests in restoring forest stand structure, floristics and diversity of vascular plants, and important ecological functions with reference to neighbouring primary forests. In addition, timber value was estimated and compared among the three forest types. The research was conducted across 11 sites within Ghana's moist and wet climatic/forest zones. Systematic random sampling of 93 plots each measuring 20m × 20m with nested subplots measuring 5m x 5m for saplings and 2m x 2m for ground vegetation was undertaken. Forty-two years after establishment and/or abandonment, both the plantation and secondary forests showed structural attributes comparable to those of the primary forests. Nevertheless, the plantation recorded much higher bole volume and basal area compared to the secondary forests. The secondary, plantation and primary forests exhibited considerable overlap in terms of floral composition, with the presence of several rare and restricted-range species. A significant proportion of primary forest vascular plant species, namely 60% and 77%, were identified in the secondary and plantation forests, respectively. The diversity of plant species, as quantified by the Shannon-Wiener Diversity Index (H') and Simpson Index (S), showed no significant variation between primary (H'=3.07, S = 0.91) and secondary (H'=2.95, S = 0.87) or plantation (H'=2.85, S = 0.87) forests. Generally, the primary and secondary forests exhibited higher species richness than the plantations. The mean above-ground carbon stocks of the plantations (159.7 ± 14.3 Mg ha-1 ) was found to be similar to that of the primary forests (173.0 ± 25.1 Mg ha-1 ), but both were much higher than the secondary forests (103.4 ± 12.0 Mg ha-1 ). Soil pH levels in the wet sites were much lower, ranging from 4.2 to 4.6, compared to moist sites, which had pH levels ranging from 4.6 to 5.4. Soil physicochemical properties, carbon stocks, fertility, microbial activity, and litter decomposition measurements across the different forest types within the climatic zones were similar. Nevertheless, significant differences were observed between climatic zones. Contrary to results of earlier tropical studies, we observed higher litter decomposition rates in the moist compared to the wet zone, which experiences higher annual rainfall, especially for the recalcitrant carbon fraction of the litter. Relatedly, soil microbial biomass and microbial population were significantly greater in the moist compared to the wet zone. Mean soil carbon stocks (0 - 50 cm) was significantly higher in the wet (106.8 Mg ha-1 ) compared to the moist (56.9 Mg ha-1 ), with mean site values ranging from 51.16 Mg ha-1 to 122.84 Mg ha-1 . The mean timber stumpage value of plantations was 3112 and $1870 per hectare, respectively. Tropical forest plantations established on long rotations under low-intensity management regimes, and secondary forests can evolve into forest systems that exhibit structural complexity, floristic diversity, ecological functionality, and self-sustainability, akin to primary forests. Such forest plantations and secondary forests constitute viable pathways for the restoration of deforested landscapes and climate change mitigation, while potentially providing landowners with moderate financial returns through selective timber harvesting.
... Behind the homogeneous green carpet often illustrated in maps or considered by global models, tropical forests are known to harbour a complex mixture of forest types organized at different spatial scales (Brando et al., 2019;Chazdon, 2003;Couvreur, 2015). Ecologists and foresters have long identified major differences between forest types, leading to different ecosystem services (e.g. ...
Tropical moist forests are not the homogeneous green carpet often illustrated in maps or considered by global models. They harbour a complex mixture of forest types organized at different spatial scales that can now be more accurately mapped thanks to remote sensing products and artificial intelligence. In this study, we built a large‐scale vegetation map of the North of Congo and assessed the environmental drivers of the main forest types, their forest structure, their floristic and functional compositions and their faunistic composition. To build the map, we used Sentinel‐2 satellite images and recent deep learning architectures. We tested the effect of topographically determined water availability on vegetation type distribution by linking the map with a water drainage depth proxy (HAND, height above the nearest drainage index). We also described vegetation type structure and composition (floristic, functional and associated fauna) by linking the map with data from large inventories and derived from satellite images. We found that water drainage depth is a major driver of forest type distribution and that the different forest types are characterized by different structure, composition and functions, bringing new insights about their origins and successional dynamics. We discuss not only the crucial role of soil–water depth, but also the importance of consistently reproducing such maps through time to develop an accurate monitoring of tropical forest types and functions, and we provide insights on peculiar forest types (Marantaceae forests and monodominant Gilbertiodendron forests) on which future studies should focus more. Under the current context of global change, expected to trigger major forest structural and compositional changes in the tropics, an appropriate monitoring strategy of the spatio‐temporal dynamics of forest types and their associated floristic and faunistic composition would considerably help anticipate detrimental shifts.
... Our focus on NDVI aimed to establish a foundation for future investigations that could utilize advanced remote-sensing technologies to explore specific vegetation characteristics, such as LiDAR or airborne laser scanning [96][97][98]. Recovery metrics based on remote sensing, such as NDVIrec, are particularly relevant for planning and managing conservation areas, as they inform adaptive management practices by identifying regions where post-disturbance recovery is slow or incomplete [99,100]. ...
The interplay between wildfires and drought stress has significantly limited forest recovery in the Mediterranean ecosystem of central Chile. Since 2010, the region has faced a prolonged 'Mega Drought,' which intensified into a 'Hyper Drought' in 2019, with record-low precipitation and high temperatures, further constraining forest recovery amidst increasing wildfire frequency. This study evaluates short-term vegetation recovery across drought gradients in three sclerophyllous evergreen forests, analyzing Landsat time series (1987–2022) for 42 wildfires. Using the LandTrendr algorithm, we assessed post-fire forest recovery based on NDVI changes between pre-fire values and subsequent years. The results revealed significant differences in recovery across drought gradients and fire severity interactions. After five years, the xeric forest dominated by Quillaja saponaria and Lithrea caustica showed 89% recovery during the Mega Drought and 34% during the Hyper Drought. In contrast, the mesic forest dominated by Cryptocarya alba and Peumus boldus exhibited 28% recovery during the Mega Drought and 43% during the Hyper Drought. Degraded thorny shrublands showed the lowest recovery, averaging 23% under Hyper Drought and medium fire severity. These findings underscore the critical role of prolonged, severe drought in shaping forest recovery dynamics and highlight the need to understand these patterns to improve future forest resilience under increasingly arid conditions.
... Warm temperatures and abundant fresh litter can stimulate high rates of litter decomposition and associated soil CO 2 fluxes from heterotrophic respiration (Ostertag and others 2003;Vargas 2012). Despite the severity and magnitude of these short-term effects, most tropical forest vegetation has been shown to be resilient to the historical hurricane regime with regard to ecosystem structure, usually recovering to canopy conditions similar to pre-disturbance environments during the periods between storms (Everham and Brokaw 1996;Weaver 2002;Chazdon 2003;Zimmerman and others 2021). This resilience to hurricanes can be attributed to evolutionary adaptations of the biota to frequent wind disturbances (that is, fast growth of early-successional species, high abundance of decomposers, high resistance to wind damage; Basnet and others 1993;Zimmerman and others 2021). ...
Models project that climate change is increasing the frequency of severe storm events such as hurricanes. Hurricanes are an important driver of ecosystem structure and function in tropical coastal and island regions and thus impact tropical forest carbon (C) cycling. We used the DayCent model to explore the effects of increased hurricane frequency on humid tropical forest C stocks and fluxes at decadal and centennial timescales. The model was parameterized with empirical data from the Luquillo Experimental Forest (LEF), Puerto Rico. The DayCent model replicated the well-documented cyclical pattern of forest biomass fluctuations in hurricane-impacted forests such as the LEF. At the historical hurricane frequency (60 years), the dynamic steady state mean forest biomass was 80.9 ± 0.8 Mg C/ha during the 500-year study period. Increasing hurricane frequency to 30 and 10 years did not significantly affect net primary productivity but resulted in a significant decrease in mean forest biomass to 61.1 ± 0.6 and 33.2 ± 0.2 Mg C/ha, respectively (p < 0.001). Hurricane events at all intervals had a positive effect on soil C stocks, although the magnitude and rate of change of soil C varied with hurricane frequency. However, the gain in soil C stocks was insufficient to offset the larger losses from aboveground biomass C over the time period. Heterotrophic respiration increased with hurricane frequency by 1.6 to 4.8%. Overall, we found that an increasing frequency of tropical hurricanes led to a decrease in net ecosystem production by − 0.2 ± 0.08 Mg C/ha/y to − 0.4 ± 0.04 Mg C/ha/y for 30–10-year hurricane intervals, respectively, significantly increasing the C source strength of this forest. These results demonstrate how changes in hurricane frequency can have major implications for the tropical forest C cycle and limit the potential for this ecosystem to serve as a net C sink.
... However, disturbances to forest ecosystems from industrialization, urbanization, agriculture and silviculture have caused historical deforestation in the tropics and sub-tropics of South China, modifying plant community species composition and compromising vital ecological functions and services (Abbas et al., 2019;Måren et al., 2017;Purschke et al., 2017;Zhuang & Corlett, 1997). Over 80% of global forests have undergone or are currently subject to degradation and fragmentation due to human disturbances, and determining methods for forest conservation and restoration is a major concern for the fulfilment of environmental targets (Chazdon, 2003;Collins et al., 2017;Holl et al., 2013;Watson et al., 2018). ...
Secondary forests represent a significant proportion of global forest cover, with over 70% of forests in East Asia classified as regenerating. While succession has been studied extensively in temperate systems, trajectories of subtropical succession remain poorly characterized in highly disturbed, urban‐adjacent forests. Investigating the additive beta diversity components of turnover and nestedness may reveal community assembly mechanisms driving secondary succession. The present study investigates plant community assembly along a successional gradient from 7 to 70 years following the onset of succession in secondary subtropical forests in Hong Kong, China. Plant survey data for 28 plots were analysed, generating additive Simpsons turnover and nestedness beta diversity metrics. Dissimilarity matrices were generated and modelled as a function of environmental matrices including forest plant community age (years following onset of secondary succession), inter‐community distance (metres), and soil moisture saturation (%) across three elevational bands using generalized dissimilarity models. Nonmetric multidimensional scaling of plant communities was conducted with Bray–Curtis dissimilarity matrices. Inter‐community distance and successional age differentially influenced plant species turnover between lowland and Montane forest types. Models of nestedness found that plot age and soil moisture saturation were significant drivers of nestedness patterns in plant communities across elevational classes. Turnover represented a higher proportion of Sorensen beta diversity than nestedness, while ANOSIM found significant differentiation between plant communities at different successional stages. Turnover patterns suggest a deterministic model of community assembly, with strong patterns of species replacement between communities at fine spatial scales and successional stages, as well as clear compositional shifts between lowland and montane forest types. NMDS analysis and functional compositional assessments suggested a transition from early successional communities with a high proportion of shrub species, to later successional communities with a higher proportion of tree species, with an increase in species turnover with greater age dissimilarity.
... The historical use of the environment and the resulting configuration of the landscape influence the richness and diversity of valuable species present in plant communities, as well as the structural characteristics of managed populations (Chazdon 2003). In this way, the physiognomy of the landscape is modified, creating mosaics of use close to the home space-such as gardens, cultivated fields, and orchards, as well as fragments of secondary forest in different successional stages and agroforestry home gardens (Milanesi et al. 2013;Wright 2005). ...
Field studies involve prolonged contact with families with whom experience, and knowledge are shared to detect emerging resources and management practices that often go unnoticed, both for the local collective imagination and those who define development and conservation policies. A productive innovation is analyzed from the fruits of Euterpe edulis, a species vulnerable to environmental changes, endemic to the Atlantic Forest. Until 20 years ago, individuals were cut to extract the apical heart. The trajectory covered in developing a family-community productive model that emerged in ethnobiological studies of the interaction between rural residents and researchers is detailed. At present, multiple uses of the fruits are made. The pulp is extracted for food and commercial purposes, and the seeds are used in nurseries for ornamental seedlings. Given the previous extractive management of these populations, advances in studies on the genetic and productive landscape are presented, adding a key element to the conservation of the populations in use. The ongoing local research and actions expand the understanding of local conservation models based on use.
... El ecosistema tropical es uno de los más afectados por las actividades antrópicas. Esta condición ha propiciado la disminución de diversos servicios ecosistémicos como la recarga de acuíferos, captura de CO 2 , erosión del suelo, pérdida de biodiversidad, entre otros (Sabogal et al., 2015;Chazdon, 2003). ...
La pérdida de biodiversidad se ha incrementado en las últimas décadas. La conexión del paisaje por restauración permite conectar fragmentos de bosque aislados para mejorar flujo génico, En Jalpan Puebla se analizó la fragmentación, la conectividad y las variables socioeconómicas del paisaje con imágenes de satélite de 1999 y 2021,
Calculándose tres índices de fragmentación: número de parches, tamaño
promedio de parche y la suma del área total de parches y el Índice Integral de Conectividad y el delta del Índice Integral de Conectividad. Se consideraron características ecológicas y biológicas de dos especies Herpailurus yagouaroundi
y Leopardus pardalis. En los últimos 22 años, la vegetación de selva alta perennifolia, ha disminuido en más del 50% . Los índices de fragmentación de parches disminuyeron, de 3730 en 1999 a 2616 en 2021 y el promedio del tamaño de parches se redujo, de 0.9 a 0.6 ha. Disminuyendo la conectividad del paisaje. Se identificaron 30 sitios prioritarios para la restauración para el incremento de la concetividad del paisaje.
... Large-scale modern agriculture excludes mixed forest patches and eliminates sources of colonizing trees that provide ecosystem resilience after disturbance (Bush & Colinvaux, 1994). The modern forest includes secondary forest and mature, old-growth forests that are species-rich and support modern peoples (Allen & Rincón, 2003;Ford & Nigh, 2015;Toledo et al., 2003), but the resilience of the forest after the collapse of the ancient Maya does not promise the same resilience after modern deforestation (Chazdon, 2003). ...
The land use of the ancient Maya strongly affected the environment of the previously forested Maya Lowlands. A forest grew back after the Maya “collapse”, some 1100 years ago. Two activities of the ancient Maya could have had widespread effects on the tree species composition of the regrown, modern forest. First, in areas with topographic relief Maya agriculture caused substantial soil erosion and accumulation, changing soil depth and character. Soil character is associated with differential distributions and abundances of many tree species in the Maya Lowlands. To the extent that soil character on the modern landscape differs from that on the pre‐Maya landscape, regrown forests on the modern landscape would differ from pre‐Maya forests. Second, the ancient Maya cleared much forest but likely also cultivated or favored certain tree species in home gardens, regenerating farm plots, and patches of older growth. A rigorous study suggests that descendants of favored tree species persist in elevated abundance in some areas of the modern forest but not in other areas. After c. 1100 years of regrowth in some places, the legacy of the ancient Maya in the modern forest likely ranges from strong to absent across the varied landscape of the Lowlands. An ancient mosaic of forest patches would have provided a species‐rich, multiple‐point source for forest regrowth. Such a mosaic is lacking in modern deforested tropical landscapes, likely inhibiting recovery of a species‐rich forest.
... Warunki te pozwalają na szybki rozkład materii organicznej (Danielsen i in. 2009), a uwalniane substancje odżywcze pobierane są przez rozwijające się rośliny (Chazdon 2003;Węglarska, Węglarski 2008). ...
Ochrona przyrody i zachowanie różnorodności biologicznej jest zadaniem trudnym, zwłaszcza na obszarze krajów rozwijających się, do jakich należą państwa Azji Południowo-Wschodniej. Do jednych z najbardziej zagrożonych ekosystemów lądowych zaliczamy lasy deszczowe. Przykładem może być indonezyjska roślinność na Sumatrze, gdzie znajdują się znaczne przestrzenie leśne, uznawane za cenne ekosystemy w skali globalnej. Powierzchnia lasów deszczowych kurczy się, obserwowane jest także zmniejszenie się całkowitego bogactwa gatunkowego. Prowadzone są liczne badania naukowe, których zadaniem jest monitoring przyrodniczy lasów deszczowych. Zaobserwowano jednak również bardzo postępującą degradację tych terenów. W pracy przedstawiono najważniejsze kwestie dotyczące znaczenia i ochrony lasów deszczowych, a także możliwych sposobów przeciwdziałania ich degradacji z zachowaniem możliwości ich częściowego wykorzystania gospodarczego przez ludność. Celem artykułu było zgromadzenie wybranych informacji na temat degradacji terenów lasów deszczowych w oparciu o analizę literatury
... Studies enumerated stems ≥1 cm dbh (Proctor et al. 1983;Putz & Chai 1987;Chalmers & Turner 1994;Rice et al. 2004;Burnham 2004;Muthuramkumar et al. 2006;Reddy & Parthasarathy 2003Campanello et al. 2007;Ding & Zang 2009) studies enumerating stems ≥1.6 cm dbh (Padaki & Parthasarathy 2000). However, it is important for identifying small-sized regeneration of climbers to know the consequences of forest dynamics (Gerwing et al. 2006), but such studies received little attention (Chazdon 2003). Some studies enumerating smaller stems to mention are ≥0.5 cm dbh studied by Dewalt et al. (2000), Yuan et al. (2009), and much lesser stem girth of ≥0.2 cm dbh by Mascaro et al. (2004), Cai et al. (2009), andChettri et al. (2010). ...
... Studies enumerated stems ≥1 cm dbh (Proctor et al. 1983;Putz & Chai 1987;Chalmers & Turner 1994;Rice et al. 2004;Burnham 2004;Muthuramkumar et al. 2006;Reddy & Parthasarathy 2003Campanello et al. 2007;Ding & Zang 2009) studies enumerating stems ≥1.6 cm dbh (Padaki & Parthasarathy 2000). However, it is important for identifying small-sized regeneration of climbers to know the consequences of forest dynamics (Gerwing et al. 2006), but such studies received little attention (Chazdon 2003). Some studies enumerating smaller stems to mention are ≥0.5 cm dbh studied by Dewalt et al. (2000), Yuan et al. (2009), and much lesser stem girth of ≥0.2 cm dbh by Mascaro et al. (2004), Cai et al. (2009), andChettri et al. (2010). ...
Decalepis hamiltonii Wight & Arn., is a woody climber, endangered due to the destructive harvest of fragrant roots and substituted for Hemidesmus indicus (L.) R.Br. (Nannari). We assessed the density, size class, distribution across habitat types, disturbance types, and environmental variables that influence the D. hamiltonii population in the Savandurga Reserve Forest (SRF). Method: The entire forest was divided into 1 km² grids, with 10 plots of 5 x 5 m established in each of the 24 grids, totaling 240 plots. Disturbances were categorized as low, medium, and high, while plots were classified into dense, mixed, and rocky outcrop habitats. Results: D. hamiltonii density ranged from 0.1 ± 0.32 to 5.2 ± 2.66 per 25 m² across the grids with an overall mean density of 675 ± 455 stems per ha. The size class distribution showed a typical inverted “J” curve, with fewer saplings (3.01–6.0 cm class), indicating potential future population instability. Stem density was lower in dense vegetation and higher in mixed vegetation and rocky outcrops, with greater densities in areas of higher disturbance. Adult density was mainly influenced by harvesting (78% variation), saplings by NDVI (2.09%) & altitude (18.72%), and seedlings by aspect (4.44%), increasing from the south to the north. Conclusion: Strict monitoring and periodic assessment of the population are essential to protect the seedlings to the sapling stage, regulation of selective harvesting of the adults, and control of the herders feeding the leaves. Encouragement of local and large-scale cultivation to reduce pressure on the wild source and to improve livelihood. Capacity and confidence building of the community with citizen science reporting of destructive harvesting will help the forest department to save the declining population.
... The structural heterogeneity likely also reflects the small-scale, high-frequency disturbance regimes causing these areas to become a complex mosaic of regeneration stages. We did not focus on forest age as a main distinguishing factor among the three regenerating forest classes because major structural discrepancies can exist in forests of the same age even if they are neighboring patches due to local environmental heterogeneity as well as complex community-and species-level interactions (Chazdon, 2003;Norden et al., 2015;Rozendaal & Chazdon, 2015). Rather, we isolated forest stages of regrowth by identifying forest patches that fit a locally defined description of visually observable canopy texture and spectral characteristics. ...
Improving our ability to monitor fragmented tropical ecosystems is a critical step in supporting the stewardship of these complex landscapes. We investigated the structural characteristics of vegetation classes in Ucayali, Peru, employing a co‐production approach. The vegetation classes included three agricultural classes (mature oil palm, monocrop cacao, and agroforestry cacao plantations) and three forest regeneration classes (mature lowland forest, secondary lowland forest, and young lowland vegetation regrowth). We combined local knowledge with spaceborne lidar from NASA's Global Ecosystem Dynamics Investigation mission to classify vegetation and characterize the horizontal and vertical structure of each vegetation class. Mature lowland forest had consistently higher mean canopy height and lower canopy height variance than secondary lowland forest (μ = 29.40 m, sd = 6.89 m vs. μ = 20.82 m, sd = 9.15 m, respectively). The lower variance of mature forest could be attributed to the range of forest development ages in the secondary forest patches. However, secondary forests exhibited a similar vertical profile to mature forests, with each cumulative energy percentile increasing at similar rates. We also observed similar mean and standard deviations in relative height ratios (RH50/RH95) for mature forest, secondary forest, and oil palm even when removing the negative values from the relative height ratios and interpolating from above‐ground returns only (mean RH50/RH95 of 0.58, 0.54, and 0.53 for mature forest, secondary forest, and oil palm, respectively) (p < .0001). This pattern differed from our original expectations based on local knowledge and existing tropical forest succession studies, pointing to opportunities for future work. Our findings suggest that lidar‐based relative height metrics can complement local information and other remote sensing approaches that rely on optical imagery, which are limited by extensive cloud cover in the tropics. We show that characterizing ecosystem structure with a co‐production approach can support addressing both the technical and social challenges of monitoring and managing fragmented tropical landscapes.
... Succession is crucial in plant ecology as it reflects the postdisturbance changes in species and abiotic factors over time (Chazdon, 2003;Chesson, 2000;Sutherland et al., 2013). Classical Relay Floristics Hypothesis regards succession as a directional and predictable pathway, where the community is thought to undergo deterministic species replacements after disturbance to become a stable and climatically appropriate climax community (Pool, 1917;Poorter et al., 2021). ...
... Secondary succession pathways depend on multiple factors and processes at different scales, driving direct or indirect changes at different levels:Patch characteristics (e.g. soil properties, size, shape, isolation, and microclimate;Chazdon, 2003;Guariguata & Ostertag, 2001).With increasing time since agricultural abandonment and structural complexity of vegetation, some amphibian assemblages can increase their richness and number of individuals (Acevedo-Charry & Aide, 2019;Thompson & Donnelly, 2018). There is mainly an increase in the abundance of generalist forest species, given the colonisation of species from the matrix (sensu spillover edge effects:Riest et al., 2004;Bowen et al., 2007). ...
Habitat loss is the primary driver of amphibian declines. The protection and management of habitats are thus the most critical conservation actions needed for at least 60% of amphibians, with habitat loss accounting for population declines and extinctions at local and regional levels. Habitat loss is directly related to pollution, but it also exacerbates other major threats to amphibians, such as disease, illegal trade, and invasive species. Habitat loss
also reduces the ability of amphibian species to disperse and alter their distribution within their ecophysiological
tolerance ranges in order to adapt to climate change. Currently, less than 30% of amphibian species are represented in the global protected-area system. The restricted geographic distribution, high habitat-specificity, and dependence on narrow climatic envelopes of many amphibian species mean that amphibians are particularly prone to local extinctions. Of the 37 amphibian species reported as extinct as of 2021, 48.6% were distributed in South and Southeast Asia, and 21% in Mesoamerica. These species mainly inhabited inland wetlands and forests. Considerable research into understanding the effects of habitat loss, fragmentation and degradation on amphibians have been undertaken over the past 15 years, including a review on the effectiveness of amphibian-targeted conservation interventions.
Habitat protection and management priorities must include the urgent preservation of remnant native forest habitats,
given that over 85% of amphibian species occur in these systems. Conservation actions must also include the
protection and rehabilitation of other aquatic and terrestrial breeding habitats critical for supporting viable amphibian populations. Given the limited resources for conservation, protection of globally important sites for amphibians (such as Alliance for Zero Extinction- AZE, and Key Biodiversity Areas - KBA), and their integration with protected areas into a network of conservation areas, is a key priority. The creation, rehabilitation and restoration of amphibian habitats, including in urban and agricultural landscapes, must not be excluded from the toolkit of interventions needed to avoid declines of more generalist species. Beyond implementing direct habitat protection mechanisms, it is essential to ensure targeted management of newly created protected areas and improve that of existing protected areas, inclusive of amphibians. For these actions to be sustainable, it is critical to facilitate the participation, communication, and involvement of a broad range of stakeholders, including government entities, productiveextractive sectors, NGOs, academia, local communities, and civil society.
... Birds are conspicuous elements of tropical forests and have been considered indicators of ecosystem integrity (Canterbury et al., 2000;Durant et al., 2009). Despite several studies documenting the effects of tropical forest restoration on bird occurrence (Chazdon, 2003;Karp et al., 2011), we still require cheap and reliable tools to measure how bird species sort themselves across recovery gradients. Since MacArthur's seminal work in the 1960s (MacArthur and MacArthur, 1961), niche theory predicts that forest structure determines bird distribution and abundance (Gregory and Gaston, 2000;Cano-Barbacil et al., 2023). ...
Conservation programs need improved tools to measure the recovery of animal diversity across restoration gradients. We used soundscapes and expert identifications of bird species to calculate niche position (i.e., mean of environmental conditions across all areas a species occupies) and niche breadth (i.e., the standard deviation of the species distribution) along a recovery gradient; from agriculture to early (up to 20 yrs) and late (up to 38 yrs) recovery, to old-growth forests. Our survey included 323 bird species and was conducted in 66 plots in the lowland Chocoan tropical rainforest in Ecuador where less than 11% of the forest remains intact, and large areas are currently undergoing regeneration post-abandonment. First, we validated our niche metrics by contrasting them against independent global categories of forest density dependency. We then explained the niche metrics of the bird species with different ecological traits, gathered from the literature, reflecting species-specific primary diet, morphology and distribution, and accounting for the phylogenetic relatedness of species. Finally, we explored the phylogenetic signal present in bird species' ecological traits and recovery niche metrics. Niche position and breadth across the recovery gradient closely followed global categories of forest density dependency. However, our approach provided a more fine-scaled sorting of bird species in forest plots categorized as late recovery and old-growth. Granivorous birds occupied niche positions in active cacao and pasture plots and were replaced by frugivorous birds in older regeneration plots. Along the recovery gradient, tail length and handwing index decreased with niche position, supporting previous observations that birds in old-growth forests are less mobile. Birds in old-growth forests had smaller global distribution ranges than birds in agricultural plots. Finally, the latitudinal distribution of birds in the study area averaged south of the equator, with birds in old-growth plots averaging latitudinal centroids in wet forests north of the equator, whereas birds in agriculture plots averaged latitudinal centroids further south of the country, towards the dry and open Tumbesian forest. Frugivores, invertivores and vertivores had broader niche breadths, but these decreased (marginally) with tail length. We suggest these recovery niche metrics as a potentially powerful tool for the rapid assessment of the recovery process, which might support conservation strategies such as biodiversity credits, compensation payments , and strategic land purchases. With the increasing availability of information-intensive models for bird species identification, such as deep learning artificial intelligence, our new niche metrics open the avenue for rapid assessment of tropical biodiversity and new conservation areas at larger scales.
... Forest types in the tropics differ in canopy structure and function, which vary with climate 4 , topography 5 , soil biogeochemistry 6,7 , and natural and anthropogenic disturbance histories and regimes 8,9 . Airborne imaging spectroscopy and LiDAR have enabled the measuring, mapping, and monitoring of tropical forest functional and structural diversity at large spatial scales, in ways that inform ecological understanding 10,11 , support conservation efforts 12 , and constrain terrestrial biosphere models 13 . ...
Past human influence from the pre‐Columbian and colonial periods may have played a role in shaping modern Amazonian vegetation. Here, we assessed past human activities and vegetation change from a well‐studied research station in the Peruvian Amazon using charcoal and phytoliths recovered from soil cores. The moderate seasonality has contributed to its high diversity, while its remoteness has generally led to assumptions of minimal past land modification by humans. We asked: (i) Is there evidence of past human influence, including cultivation, forest opening, or plant enrichment/depletion, in the forests around Cocha Cashu Biological Station? and (ii) was there a consistent increase in palm phytolith abundances through time as has been documented in the aseasonal forests of northwestern Amazonia? Only 38 (14%) of the 279 samples analyzed contained charcoal, highlighting the rarity of past fire at Cocha Cashu. The two charcoal fragments large enough for ¹⁴ C dating had ages of 570–670 and 1350–1520 calibrated years before present. No cultivar phytoliths were found. Spheroid echinate phytoliths, produced by the palm genera Attalea, and Oenocarpus , and Euterpe , were more abundant in past samples than in modern samples. There was no increase in palm phytolith abundances from the bottom to top of the core, contrasting with recent findings from northwestern Amazonia. Our results support ideas that Cocha Cashu is composed of old growth forests and suggest that gradients of past human activities exist on local and regional scales in western Amazonia.
Se evalúa el papel de los bosques secundarios en la conservación de abejas y en la producción de aguacate en la región Trifinio, Chalatenango, El Salvador. Este estudio evalúa la composición y diversidad de las comunidades de abejas en sitios de bosque secundario y plantaciones de aguacate, así como el efecto del tipo de manejo agronómico de las plantaciones y la estructura y diversidad de la vegetación de los bosques. Se emplearon métodos de muestreo pasivos y activos, los cuales incluyen redes entomológicas y trampas de paletas azules. Además, se evaluaron parámetros ambientales como temperatura, humedad y cobertura de dosel, para relacionarlos con la diversidad y abundancia de las abejas. Los resultados muestran que las plantaciones de aguacate presentaron mayor riqueza de especies en comparación con los bosques secundarios, mientras que la diversidad fue igual para ambos usos de suelo. La abundancia de abejas fue mayor en los bosques al controlar por variables ambientales. La estructura del bosque influye en la diversidad, con una menor diversidad de abejas en bosques con mayor altura, área basal y cobertura de dosel. En cuanto a la composición de especies, aunque las plantaciones y los bosques comparten muchas especies de abejas, las plantaciones albergan una cantidad significativa de especies únicas. No se encontraron diferencias sustanciales en la composición de especies entre los usos de suelo. Las abejas sociales, como Apis mellifera y Trigona fulviventris, dominan en ambos tipos de hábitats, reflejando su adaptabilidad a diversos entornos. La gestión agrícola también impacta en la abundancia de abejas. Las plantaciones con manejo inorgánico e intensidad media muestran las mayores abundancias, mientras que no se detectan efectos significativos en términos de diversidad. Esto está relacionado con el entorno circundante y la complementariedad del hábitat. Los productores reconocen la importancia de las abejas para la polinización, aunque pocos implementan prácticas que promuevan su conservación. Este estudio contribuye a entender el papel crítico de los bosques secundarios en la conservación de polinizadores y en el mantenimiento de servicios ecosistémicos clave para la agricultura, especialmente en el contexto de una creciente presión sobre los ecosistemas forestales. Los hallazgos resaltan la relevancia de integrar prácticas de manejo que favorezcan a los polinizadores en los sistemas agrícolas y la conservación de fragmentos de BS, para mejorar la sostenibilidad de cultivos comerciales en la región Trifinio.
The article presents the research results of spatial structure of the main park-forming species (Acer platanoides L., A. campestre L., Fraxinus excelsior L., Tilia cordata Mill.) in the ecotopes of the «Оlexandria» State Dendrological Park of the National Academy of Science of Ukraine are presented. The spatial structure was determined by mapping trees by age groups. The spatial organization of the studied tree species has species specificity and shows age confinement to different park ecotopes. The most numerous Acer platanoides and A. sampestre are distributed more or less evenly throughout the park. The third most abundant species, Fraxinus excelsior, is concentrated in the eastern part of the park. The formation of a large young cenopopulation in the south-western part of the park was noted. The predominant number of natural stands of Tilia cordata is concentrated in the oak woodlands of the western part of the park. Today the population of Tilia cordata is practically not recovered, however, over the past half of a century it has formed a powerful ecotone in the oak forest in the central part of the park, displacing the species-edifier Quercus robur L. Populations of all studied species have a full age structure in oak-oak-type plots. The age structure of all species is disturbed in technogenically polluted ecotopes, in areas of mass phytopathogens reproduction in quasi-natural areas with significant anthropogenic interference. The distribution of older age groups individuals is mostly random and uniform, while group distribution is observed in younger trees. In all studied species more dense areas of all ages’ specimens or sparse, small groups or even single specimens, are distinguished. The latter is typical for older age groups trees. The main factors determining the distribution of the main park-forming species are the ability of tree species natural regeneration, pest and disease damage, and economic activity. Key words: forest type plantations, spatial structure, tree mapping, age groups, types of spatial distribution, factors determining distribution.
Ecosystem services (ESs) are extremely important, specifically in urban areas. Urban forests, even representing a pivotal role in global sustainability, have been converted into different human-modified landscapes. This paper aims to analyze the ES provided by the urban areas of 25 cities of the Atlantic Forest in Brazil. We used i-Tree Canopy v.7.1 to classify the land use. We quantified the monetary benefits of the urban vegetation and used socioeconomic variables (i.e., total population, population density, Human Development Index (HDI), and Gross Domestic Product (GDP) per capita) to analyze if the ecosystem services or the land uses are associated with this. Our data reveal that together, the cities studied sequester a significant total of 235.3 kilotonnes of carbon and a substantial 864.82 kilotonnes of CO 2 Equivalent (CO 2 Equiv.) annually. Furthermore, together, they also store a total of 4861.19 kilotonnes of carbon and 17,824.32 kilotonnes of CO 2 Equiv. We found out that the average monetary estimate of annual carbon sequestration was USD 3.57 million, while the average stored estimate was USD 73.76 million. Spearman's correlogram showed a strong positive correlation between density and the percentage of impervious cover non-plantable no trees (IN) in urban areas (p < 0.001). IN was also positively correlated with HDI (p = 0.01), indicating that urban areas with higher HDI tend to have larger impervious areas. Our data suggest essential insights about the ecosystem services provided by urban areas and can serve as significant findings to drive policymakers' attention to whether they want to provide more ecosystem services in cities.
Acoustic communities are acoustically active species aggregations within a habitat, where vocal interactions between species can interfere their communication. The acoustic adaptation hypothesis (AAH) explains how the habitat favors the transmission of acoustic signals. To understand how bird acoustic communities are structured, we tested the effect of habitat structure on the phylogenetic structure, and on the phylogenetic and vocal diversity of acoustic communities in a semi-arid zone of Mexico. From autonomous recordings in three types of vegetation (crop fields, tetecheras, and mesquiteras), which differ in terms of complexity and canopy openness, we evaluated sound attenuation, and estimated metrics of phylogenetic structure and diversity as well as acoustic diversity with the use of two indices. Mesquiteras showed greater vegetation density, more attenuation, more vocal diversity, as well as a phylogenetic structure that tended towards overdispersion, in contrast to crop fields that showed less vegetation density, less attenuation, less vocal diversity and more phylogenetic relatedness, while tetecheras showed intermediate patterns. Phylogenetic structure was explained by vegetation density and excess attenuation. The higher vocal diversity, phylogenetic structure tended towards overdispersion. These results suggest a role for environmental filters in the crop fields, where more closely related species with similar vocal characteristics coexist (supporting AAH), and probably competitive exclusion in the mesquiteras, where more distantly related species coexist, promoting vocal diversity. This study offers information about the influence of habitat on the acoustic community structure, which could inform our understanding of the distribution of species from acoustic perspective.
At this stage of the Great Acceleration of the Anthropocene, humanity is experiencing the global issues of worsening climate change impacts, devastating damage from more frequent and severe natural disasters and the COVID-19 pandemic, all of which are attributable to ecosystem degradation and biodiversity loss. The global community recognises that these issues pose severe societal and economic risks. “Nature-based solutions” have been posited as a means to address these threats. Nature-based solutions utilise natural terrestrial ecosystem functions to provide environmental, social and economic benefits at low cost. The growing social demand for nature-based solutions constitutes an opportunity for the field of ecology to expand beyond the conventional focus on biodiversity and conservation and shift to presenting biodiversity and ecosystem functions as the basis of human well-being and social sustainability. We sought to identify a trajectory for ecological research that is aimed at contributing to the effective implementation of nature-based solutions. First, we summarise current social needs related to terrestrial ecosystem utilisation. Next, we provide an overview of existing literature and knowledge regarding biodiversity and terrestrial ecosystem function, which are critical to nature-based solutions. Finally, we identify outstanding ecological hurdles to the implementation of these strategies and propose a way forward based on our findings. We explain that any basic presentation of ecological processes requires addressing the impacts of climate change and the interrelatedness of biodiversity, climate and social systems. Enhanced ecological process models are critical for linking biodiversity and ecosystems with climate and social systems. It is crucial to establish a framework that embeds monitoring systems, data infrastructure and delivery systems within society to mobilise terrestrial ecosystem and biodiversity data and results. Furthermore, the implementation of nature-based solutions must include acknowledging trade-offs in objectives and transdisciplinary research with other fields and stakeholders with the shared goal of transformative change. Ecological research must demonstrate more clearly how terrestrial biodiversity and ecosystems are linked to human health and well-being, as well as how they are affected by production and consumption systems. In the age of climate change, the knowledge and tools of the ecologist form the foundation of nature-based solutions and provide an indispensable theoretical basis for this approach.
In May 2008, Chaitén volcano entered an eruptive process, leading to one of the world’s largest eruptions in recent decades. The magnitude of tephra ejected by the eruption left different types of disturbances and caused diverse forms of environmental damage that were heterogeneously distributed across the surrounding area. We went to the field to assess the early vegetation responses a year after the eruption in September 2009. We evaluated the lateral-blast disturbance zone. We distributed a set of plots in three disturbed sites and one in an undisturbed site. In each of these sites, in a rectangular plot of 1000 m2, we marked all standing trees, recording whether they were alive, resprouting, or dead. Additionally, in each site of 80 small plots (~4 m2), we tallied the regenerated plants, their coverage, and the log volume. We described whether the plant regeneration was occurring on a mineral or organic substrate (i.e., ash or leaf litter, respectively). In the blast zone, the eruption created a gradient of disturbance. Close to the crater, we found high levels of devastation marked by no surviving species, scarcely standing-dead trees and logs, and no tree regeneration. At the other extreme end of the disturbance zone, the trees with damaged crowns were resprouting, small plants were regrowing, and seedlings were more dispersed. The main form of regeneration was the resprouting of trunks or buried roots; additionally, a few seedlings were observed in the small plots and elsewhere in disturbed areas. The results suggest that the early stages of succession are shaped by life history traits like dispersion syndrome and regeneration strategy (i.e., vegetative), as was found after other volcanic eruptions. Likewise, the distribution of biological legacies, which is related to disturbance intensity, can cause certain species traits to thrive. For instance, in the blow-down zone, surviving species were chiefly those dispersed by the wind, while in the standing-dead zone, survivors were those dispersed by frugivorous birds. Additionally, we suggest that disturbance intensity variations are related to the elevation gradient. The varying intensities of disturbance further contribute to these ecological dynamics. The early succession in the blast zone of Chaitén volcano is influenced by the interaction between species-specific life history, altitudinal gradient, and biological legacies. Further studies are required to observe the current successional patterns that occur directly in the blast zone and compare these results with those obtained following other volcanic disturbances.
Cultural and natural values form the core of World Heritage designation. Properties displaying both values, however, comprise a fraction of inscriptions (currently c. 3%) to the World Heritage List. In 1992, when that fraction stood at c. 5%, adoption of the popular ‘cultural landscapes’ category of cultural heritage in 1992 was therefore hailed as a key development under the 1972 World Heritage Convention. This new designation provided, for the first time, a definitive bridge between humans and the environment, and was intended to open the door to World Heritage recognition for underrepresented parties to the Convention, particularly in the Global South, and to pave the way for a diverse range of landscape‐based inscriptions. As important and successful as this category has been in the three decades since its adoption, European sites in the Global North dominate the category and >90% of cultural landscape inscriptions recognise cultural heritage values alone rather than mixed values. This paper examines the largely hidden role of human–environment legacies in tropical World Heritage properties in the Global South, in some of the most biologically diverse and endangered ecosystems on the planet. Specifically, it highlights the long‐term interaction between people and tropical environments as revealed through palaeo science, pre‐recent (>200 years) history, Indigenous and traditional practices. Using exemplars internationally recognised as being wholly of natural outstanding universal value, it argues that limited reference to this evidence in World Heritage narratives potentially inhibits wider recognition of the role that humans have played in shaping the ecological development of contemporary environments.
The global biodiversity crisis is driven by a complex set of human-caused disturbances across different spatial scales. Such disturbances not only cause species losses but also affect a myriad of ecological processes that are critical for forest recovery. Here, we present the most comprehensive meta-analysis to date (1976–2023) of human impacts on the regenerating tree community (i.e. seedlings, saplings, and juveniles) across tropical rainforests. We examined the response of woody plant (i.e. trees, shrubs and palms) community patterns (e.g. species diversity) and processes (e.g. individual growth and survival) to four major human disturbances: fire, defaunation, logging, and exotic/invasive species. We gathered 773 disturbed vs. non-disturbed comparisons from 99 studies. Exotic/invasive species and fire showed strong negative impacts on the regenerating plant community, causing a decrease in species richness, diversity and abundance in more disturbed areas. Such impacts were especially detrimental to old-growth forest species, which are usually rare and more prone to local extirpation. Time since the last fire had a negative impact on the early phases of the regenerating community recovery. Conversely, most response variables increased in defaunated and logged forests, as these disturbances (e.g. loss of herbivores) increased plant performance. Yet, the loss of seed dispersers seems to have weak effects on most responses. Interestingly, reduced-impact logging activities show effects similar to those of conventional and selective logging. Overall, our results revealed that human disturbances threaten the abundance and diversity of regenerating tropical trees, but tree performance and productivity variables may be favored by some human activities. Although further research is needed to fill persisting knowledge gaps, our findings have valuable ecological and applied implications that can guide urgently needed conservation and restoration strategies aimed at mitigating the impact of human disturbances on forest regeneration.
L'extraction automatique des caractéristiques du paysage est de plus en plus rendue possible grâce à l'utilisation croissante des algorithmes SIG et des méthodes avancées d'analyse des données géospatiales. L'article aborde le potentiel du SIG GRASS pour l'analyse de la géométrie des unités de paysage à travers le calcul de données raster. Les données ont été obtenues en se basant sur des images satellites classifiées du Libéria, en Afrique de l'Ouest, entre 2014 et 2023. La dynamique du paysage a été analysée dans les changements diachroniques de six indices indiquant la déforestation au Libéria : indice de densité des unités paysagères, indice de forme, indice de numéro des unités de paysage, écart type, coefficient de variation et plage de patch. L'analyse numérique a été effectuée techniquement en utilisant les méthodes de script de SIG GRASS par les modules suivants : r.li.patchdensity, r.li.shape, r.li.patchnum, r.li.padsd, r.li.padcv et r.li.padrange. A l’échelle parcellaire, l’indice de forme est passé de 2,86 en 2014 à 4,09 en 2023, ce qui indique l’augmentation de la somme des longueurs de bords du paysage, donc une fragmentation accrue du parcellaire. A l’échelle du paysage, la courbure accrue de la zone paysagère et la séparabilité des éléments individuels indiquent également des processus de fragmentation mais à l’échelle des forêts. Cette fragmentation à différentes échelles s’accompagne d’une baisse notable de la part de la forêt dense, information prouvée par des valeurs inférieures de l’indice de densité des patchs en 2023 (1,15) qu’en 2014 (1,68). En global, la superficie forestière a été réduite de 12 % ce qui suggère un taux annuel moyen de déforestation de 0,9 % au Liberia.
Here, we developed and applied models to quantitatively reconstruct forest cover and biomass changes at three lakes in northwestern Amazonia over the past > 1500 yr.
We used remotely sensed data and a modern dataset of 50 Amazonian lakes to develop generalized linear models that predict aboveground biomass, using phytolith morphotypes and forest cover as predictor variables. Also, we applied a published beta regression model to predict forest cover within 200 m of each lake, using Poaceae phytoliths. Charcoal and maize phytoliths were analysed to identify past land use.
Results showed forest cover and biomass changes at our study sites ranged between 48–84% and 142–438 Mg ha⁻¹, respectively. Human occupation was discontinuous, with major changes in forest cover and biomass coinciding with periods of land use. Forest cover and biomass decreased notably after fire (at all sites) or cultivation events (Lakes Zancudococha, Kumpaka). The timing and ecological impact of past land use were spatially and temporally variable.
Our results suggest past human impact was small‐scaled and heterogenous in northwestern Amazonia, with a significant impact of fire on forest cover and biomass changes.
Tamarind cultivation faces challenges due to marginal land use, soil erosion, nutrient depletion and suboptimal fertilization practices, impacting productivity and quality. A study assessed nitrogen-fixing tree leaf powder's effect on Tamarindus indica seedling growth, employing a Complete Randomized Design with four treatments (Bauhinia racemosa, Tamarindus. indica, Siamese cassia and control) and ten replications. Results showed no significant differences at 0.05 probability level, yet Bauhinia racemosa supported branch length, stem diameter and leaf production, outperforming other treatments. Siamese cassia exhibited highest shoot height, while control promoted leaf production. Bauhinia racemosa proved optimal for T. indica growth. Innovative strategies, such as examining leguminous leaves, breeding and bio-engineering, can enhance tamarind's slow growth, ensuring sustainable production and utilization.
Although selective logging has become the primary cause of degradation in many African countries, little is known about its long‐term effects. This study investigated the long‐term effects of selective logging on forest tree species diversity and dynamics in the East Region of Cameroon. Six permanent monitoring plots of 1 ha each in unlogged and logged forests were established in 2005 and a recensus in 2011. Each 1 ha plot was divided into 25, 20 × 20 m quadrats. Each 20 × 20 m quadrat was further divided into 16, 5 × 5 m subquadrats, where the diameter at breast height (DBH) of all trees ≥ 2 cm was measured. There was a decrease in plant species density and richness in all forest types. Sloetiopsis usambarensis was the most important species in the unlogged forests and forests logged 21 years ago. The most important family was Putrangivaceae, Euphorbiaceae and Violaceae in the unlogged forests and forests logged 11 and 21 years ago, respectively. The frequency distribution of stem size classes indicated a reversed J‐shape of tropical forests. The above ground biomass (AGB) recovered more than 50% in all forests, and the unlogged forest had the highest AGB (961.8 Mg/ha). Larger stems indicated a forest at a stage of recovery from disturbance. Silvicultural management should be considered.
Nutrient recycling is a fundamental process for the functioning of tropical forests; however, anthropogenic activities such as mining could affect this process in tropical ecosystems. Given that little is known about the effects of mining on nutrient recycling in tropical forests, the objective was set to evaluate the influence of mining on nutrient cycling in tropical rainforests of the Colombian Pacific. Additionally, the hypothesis that nutrient cycling could be lower in post-mining areas was evaluated. To evaluate the effect of mining on nutrient cycling, permanent plots were established in mature and post-mining forests. In both forests, soil acidity, aluminum (Al), organic matter (OM), total nitrogen (N), available phosphorus (P), magnesium (Mg), potassium (K), calcium (Ca), and effective cation exchange capacity (ECEC) were considered. Likewise, the litter production, decomposition, and accumulation on the ground were determined; additionally, nutrient content and nutrient use efficiency (NUE) were determined. It was observed that mining influenced the nutrient contents of the soil in a different way. It was evident that total N and soil OM were similar in both forests, while the contents of P, K, Ca, Mg, Al, and ECEC available were higher in post-mining. The litterfall production and litter mass accumulation on the ground were greater in post-mining, while litter decomposition was greater in mature forests. In mature forests, there was higher foliar content of N, Ca, and B and, in addition, higher NUE of Ca. However, in post-mining, there was higher leaf content of K, Mg, P, Fe, Cu, Mn, and Zn and, in addition, greater NUE of N, P and K. In conclusion, an increase in post-mining nutrient cycling was noted as a strategy for nutrient conservation, and recovery of the functioning and maintenance of productivity in degraded Pacific ecosystems. Consequently, it is expected that in the future, if mining continues in the region, productivity and nutrient recycling will be altered.
Vegetation maps were prepared from aerial photographs taken in 1943?45 and 1991?92 of three, widely separated areas of sclerophyll forest adjacent to the western edge of rainforest on granitic soils in north Queensland. Nine types of sclerophyll communities could be discerned from aerial photos and characterized by field measurement. Two types of Wet Sclerophyll Forest (WSFa and b) were separated on the species of tree composing the tallest stratum and these were subdivided according to whether the ground layer was dominated by grass or young rainforest. A related type showed large, residual Eucalyptus grandis emergent from mature rainforest. Closed canopy sclerophyll forest with no emergents (SF), sclerophyll woodland and Acaciaforest were also discerned. WSF was defined as having more than 30 per cent of the closed crown cover contributed by trees more than 35 m tall. During the 50-year study period rainforest invaded 70 per cent of WSFa (tallest stratum dominated by E. grandis), which principally occurs as a narrow strip along the rainforest margin, and 57 per cent of the adjacent WSFb (tallest stratum composed of mixed species). Grass would be quickly excluded from invaded areas and thereafter they would only burn under extreme atmospheric conditions. Because sclerophyll trees are unable to regenerate in shade and usually require fire to provide the appropriate conditions, a long-term transition to rainforest may ensue. The final stages of this transition were observed in areas that exhibited full-stature rainforest with large, relictual E. grandis emergents in 1943, but had disappeared by 1992. The initial cause of this vegetation transition is a fire-free period of sufficient length for rainforest tree seedlings to establish and suppress the grass layer. It is not known whether these vegetation changes represent a trend, possibly caused by a change a century ago from fire management by Aboriginal people to management for the cattle industry, or whether it is a temporary phase in the fire-induced, dynamic relationship between rainforest and sclerophyll vegetation. The current loss of WSF probably endangers the survival of a range of genetically endemic biota. Most groups are poorly known but the marsupial Yellowbellied Glider Petaurus australis reginae is totally dependent upon WSF and a number of vertebrates would probably go locally extinct if WSF is replaced by rainforest. WSF is the wettest part of the sclerophyll communities and probably acts as a refuge in times of unusual aridity. To maintain the WSF habitat, fire management is clearly indicated, but the intensity of fire required to reverse the advance of rainforest may be socially unacceptable to instigate or impossible to control if it occurs by accident.
Changes to Aboriginal fire regimes since European occupation are thought to have affected the range and demographic structure of many vegetation communities. This study shows a contraction by 49% of the area of fire-prone open forest through rainforest invasion between 1945 and 1991-94 in the northern wet tropics of Queensland, Australia. Relative Growth Rates (RGR) for open forest areas varied from -0.112 to -0.005. Collaborative historical research with the Aboriginal traditional owners, the Kuku-Yalanji people, investigated possible linkages with alterations to their fire practices. A multiplicity of human impacts is associated with the measured vegetation change, including clearing for agriculture and mining, logging for timber and firewood, and the introduction of cattle and horses. Some rainforest expansion since 1945 represents a recovery following clearing from earlier mining operations. Contraction of open forest through rainforest invasion was most rapid (RGR = -0.124) where there was a continuation of Aboriginal fire management with cattle grazing. The contraction of open forest was nine times slower in an ungrazed area (RGR = -0.005) than in a nearby area grazed by horses (RGR = -0.045). Aboriginal fire regimes may act synergistically with cattle or horse grazing to accelerate the invasion of rainforest into open forest. Management prescriptions currently focus on active fire management to prevent further open forest contraction. However, fire management may have unexpected outcomes when rainforest-open forest dynamics are complicated by recent historical factors such as cattle grazing, logging, and tin mining, and possible synergies between these factors and fire regimes. Managers need to understand the histories of particular sites when formulating plans, and monitor the consequences of their actions to enable an adaptive approach.
Models based on island biogeography theory are used to evaluate the relationship between extinctions of species and deforestation. Natural resiliency causes the models to overestimate the rates of species extinctions for given intensities of deforestation. There is an opportunity to couple natural processes with management activities to reduce species extinctions and restore species richness to degraded lands. The authors show how tropical monoculture tree plantations can foster diverse native forests in areas previously deforested. The object is to discuss both the losses and gains of species in damaged lands with particular attention to the opportunitites for augmenting the numbers of species per unit area through management. The authors focus on the importance of managed forest stands as species refugia and more importantly, as tools for restoring species richness in degraded sites. Studies in Caribbean island coffee plantations suggest that these human-managed ecosystems served as refuges for orchids and avifauna when high deforestation rates had consumed and/or fragmented available natural habitat. -from Authors
Physical and biological barriers can delay natural regeneration in degraded ecosystems. Tropical tree plantations can contribute to restore soils and accelerate forest regeneration. In a program on ecosystem rehabilitation in three regions of Latin America, about 50% of a total of 29 tree species tested had positive effects on soils and good growth, making them attractive to farmers for reforestation. In plantations with indigenous tree species in the humid lowlands of Costa Rica, tree regeneration was higher under plantations than in abandoned pastures. Tree regeneration was high under mixed-species plantations. Open pastures had the highest proportion of wind-dispersed seeds, while bird and bat seed dispersal was predominant in the plantations. High litter accumulation on the plantation poor diminished grass growth and encouraged woody invasion. In regions with larger agricultural fields and farther from sources of propagules, windbreaks and remnant trees in pastures may be important reservoirs of native tree species. Windbreaks are more attractive to birds if they include native, fruit-producing trees, if they have high species and structural complexity, and if positioned between forest patches, facilitating bird movement. Strategies for recovery of degraded ecosystems need to consider factors influencing tree regeneration, other potential effects on the ecosystem, and economic, social and environmental constraints.
Anthropogenic alteration of the landscape is a long-term disturbance both in duration and consequences. This study addresses land-cover responses to a history of human land use in northeastern Puerto Rico. Analysis of aerial photographs indicated that the pattern of land use in the municipality of Luquillo changed dramatically between 1936 and 1988. In 1936, sugar cane and pasture were the dominant land uses, occupying about one third of the study area each, while dense forest was rare. Pasture still occupied about a quarter of the area by 1988, but the area of sugar cane had declined to zero. Most sugar cane land was transformed to pasture after abandonment, while much of the pasture at higher elevations reverted to forest. More than half the study area in 1988 was occupied by dense forest, and the degree of forest regeneration was greatest adjacent to the Luquillo Experimental Forest and around parches that were dense forest remnants in 1936. The overall trend was from high-intensity agriculture to dense forest, bur urban areas increased more than 2000 percent between 1936 and 1988 and are presently encroaching on forested areas. It is unclear from one study whether the same pattern would hold true at other sites in the tropics, but our study indicates the importance of preserving remnants of mature forest as sources of forest regeneration. In addition, the nature of the patches in the Luquillo landscape has changed as the land use has changed. In 1936, dense forest was highly fragmented, the patches were small and many of them had linear configurations (riparian corridors and hedgerows). By 1988, the average parch size of dense forest had increased greatly, although with one exception the parches were still small relative to other land-cover types.
In tropical moist forests, disturbance may enhance the coexistence of species through reduction of competition by dominants (Connell 1978; Huston 1979) and creation of establishment sites for seedlings (Brokaw 1985; Denslow 1980a, 1987). However, intense, repeated, and extensive human disturbance causes high rates of species extinctions (Wilson 1988). The debate on how best to manage tropical forests commercially shows that the relations between disturbance patterns, species diversity, and ecosystem processes are not well understood (Whitmore and Sayer 1992). In particular, the effects of species richness on disturbance regimes and successional patterns are more poorly understood than the effects of disturbance on community composition. This chapter examines the effects of species and groups of species on both disturbance regimes and the successional processes they trigger.
A preliminary series of transects, covering approximately the first 200 years of forest development on undisturbed riverbends in Peruvian lowland forest, were analyzed for community changes in plant dispersal spectrum and its apparent consequences. The annual beach community is composed of approximately half true beach species and half seedlings of forest species. The seedlings of those species dominating the canopy for the first few centuries are present at the initial stages of forest development, and the riverbend deposition process is seen as critical for the maintenance of naturally occuring stands of large trees. Water, bats and wind are the principal initial determinants of forest community structure. Both the understory and canopy fill in first with more bird-dispersed and later with more mammal-dispersed species. Some floristic differences between adjacent old river levees are attributable to age and site characteristics, but seed availability and dispersal are probably more important.
A worst-case scenario for the future of tropical forests is based on beliefs that tropical forests are unusually fragile, that continued population growth will raise demands for forest products beyond what they can produce, that increased dependence on technology will result in faster and more catastrophic destruction of resources, and that human greed, misguided public policies, and market failure will also cause destruction of tropical forests no matter what else is done to protect them. All these beliefs are based on experience. However, there are alternatives. The belief that tropical forests are unusually fragile is based on ideas of ecosystem properties that have been modified since the 1970s when they were prevalent. Today, ecologists emphasize tropical forest resiliency and its capacity to regenerate after natural disturbances. Tropical forest environments have changed and continue to change at an accelerated pace as a result of human activity. Although the change can be directed to minimize negative effects, even under a best-case scenario, future tropical forests will be exposed to different atmospheric conditions and may support a different combination of species, including more exotic and cosmopolitan species and fewer endemic species. Humans must step up management activities to include the whole landscape over a long-term scale and use ecologically sensitive technologies to rehabilitate damaged ecosystems. Human populations will have to be concentrated to better distribute food and fiber, process waste water, and minimize damage to the biota. Success in managing tropical landscapes will depend on the attention given to socioecological factors, the education of the population on issues of resource conservation, the focus of research activity, and the strengthening of resource management institutions.
This study reviews how West African deforestation is represented and the evidence which informs deforestation orthodoxy. On a country by country basis (covering Sierra Leone, Liberia, Cote D'Ivoire, Ghana, Togo and Benin), and using historical and social anthropological evidence the authors evaluate this orthodox critically. Reframing Deforestation suggests that the scale of deforestation wrought by West African farmers during the twentieth century has been vastly exaggerated. The authors argue that global analyses have unfairly stigmatised West Africa and obscured its more sustainable, even landscape-enriching practices. Stessing that dominant policy approaches in forestry and conservation require major rethinking worldwide, Reframing Deforestation illustrates that more realistic assessments of forest cover change, and more respectful attention to local knowledge and practices, are necessary bases for effective and appropriate environmental policies.
Recent paleoecological, biogeographical, atmospheric and climatological findings have revealed that general conceptions of the assumed ageless stability of today’s tropical forest ecosystems can no longer be supported. Pleistocene climatic changes and Holocene climate oscillations have caused significant fluctuations in tropical forest biomes, which leads to the conclusion that patterns of distribution and species composition of today’s tropical forest formations are closely related to the relatively short period of modern climate conditions.
In addition to the impact of climate change, other forces such as anthropogenic forest disturbance, the ecological feedback mechanisms of deforestation and other humaninduced environmental changes, determine the present and the possible future development of the tropical forest biota. A predictive assessment of tropical forest development requires detailed knowledge of interacting ecological processes, that is, the coupling of small-scale impacts (e.g. timber extraction, shifting cultivation, grazing, fire) with large-scale feedback mechanisms (e.g. atmospheric changes, meso- and macro-climate change).
A thorough understanding of paleoclimate and forest changes and the coupling of terrestrial ecology with atmospheric sciences will be imperative to predict the possible development of tropical forests in transition to a new climate-supported equilibrium. The introductory paper to this volume gives some selected examples of past and present natural disturbance processes in the tropical forest biota. The possible impacts of anthropogenic disturbances on present and future ecosystem processes are highlighted.
Lowland tropical rain forests have generally been regarded as ecosystems in which natural fire was excluded by fuel characteristics and the prevailing moist environment (Richards 1966; Mutch 1970; Mueller-Dombois 1981). However, recent findings demonstrate that climatic conditions since the late Pleistocene have favored the occurrence of natural and anthropogenic fires in the Amazon Basin and in East Kalimantan (Sanford et al. 1985; Saldarriaga and West 1986; Goldammer and Seibert 1989). It has also been demonstrated that the fuel characteristics, and the influence of drought on the microclimate and flammability of rain forest, may create conditions suitable for the occurrence and spread of long-return interval wildfires in today’s primary rain forests (Uhl and Kauffmann this Vol.). Modern human impact on tropical forest lands is rapidly increasing, causing overall degradation, and conversion of rain forest vegetation to pyrophytic life forms with increased flammability and fire frequency (Mueller-Dombois and Goldammer this Vol.; Goldammer 1991).
Forest structure and dynamics in the Luquillo Experimental Forest (LEF) are organized along an altitudinal gradient that reflects atmospheric, edaphic, and topographic conditions in the Luquillo Mountains. Global circulation drives atmospheric conditions in the LEF. In spite of its favorable tropical climate, the environment in the LEF has periods of considerable stress associated with storms and hurricanes. These events trigger landslides and periods of massive sudden tree mortality that greatly influence conditions for forest growth and succession. The main abiotic conditions that stress the biota are: (1) mechanical stress imposed by heavy winds and rains, (2) strong leaching of all surfaces by nearly pure waters with high chemical potential, (3) unstable terrain subject to mass movements on which plants must anchor and grow, and (4) saturated and anaerobic soils. Fourteen biotic responses to these abiotic challenges are discussed. These are: (1) smooth forest canopies, (2) episodic tree mortality, (3) size and age dominance among tree populations, (4) high diversity of life forms, (5) interception and retention of nutrients by epiphytes and other specialized life forms, (6) high interception of water, (7) formation of tree unions and morphological or growth plasticity, (8) modification of microtopography by trees, (9) overriding importance of certain groups of organisms, (10) high turnover of species in microscales, (11) heterophylly and sun and shade light adaptation, (12) high root density, root biomass, and turnover of fine roots, (13) high turnover of nutrients and organic matter as a result of root and vegetation dynamics, and (14) constancy of ecosystem rate processes in mature stands. Because of disturbances and the high rainfall, biotic control over nutrient cycles and organic matter turnover appears critical. We identify five main interfaces where the biota controls these parameters, forming the basis for resiliency of forest ecosystems in the LEF. These interfaces and their key biotic controls are: (1) atmosphere-terrestrial interface dominated by epiphytes and atmospheric fungi, (2) soil-aboveground interface dominated by microorganisms and animals such as earthworms, (3) plant-soil interface dominated by woody vascular plants and animal populations such as termites, (4) terrestrial-aquatic interface dominated by a large array of aquatic and amphibian species of plants and animals, and (5) the aerobic-anaerobic interface dominated by bacteria and fungi.
Provides a descriptive overview of riparian primary succession near the Cocha Cashu Biological Station in the Manu National Park, Peru. Plant growth may be rapid in the early stages of colonisation of newly-formed alluvial deposits (where the characteristic pioneer woody species is Tessaria integrifolia), but the forest acquires the structure and species composition of the mature phase by a continuous filling out of the vertical profile over several hundred years. The mature phase comprises five strata, though any interpretation of such a structure must be tentative. Implications of mature forest structure on animal communities are noted. -P.J.Jarvis
Damage included defoliation, breakage of twigs, branches and trunks, tree falls and post-cyclone tree mortality. Extrapolations from meteorological data indicate that 33-44% of the range of dry evergreen forest may be subject to cyclone damage per century. The species composition of dry evergreen forest on a local and wider geographical scale typically is fairly uniform in the subcanopy layer, but variable in the upper layers. Recurrent cyclone damage may be an important factor contributing to succession in dry evergreen forest and to the variation in species composition of the upper layers. -from Author
Cyclone "Winifred' crossed the coast of N Queensland on 1 February, 1986 causing extensive damage to coastal forests, crops and property. Forest damage was classified in 4 categories defined according to scale and intensity of tree injury. Patterns of forest damage were influenced by location in the cyclone's path, topographic exposure, characteristics of the forest type and site conditions such as soil drainage. The effects of previous disturbance, eg past cyclone damage or logging were difficult to determine in the absence of replicated comparative data. Large gaps caused by previous cyclones were not extended. Although vegetative regrowth was rapid and widespread, fires occurred later in some disturbed coastal forests, including fire sensitive rainforests and palm forests. Such fires in closed forests are an effective invitation to grass and weed invasion. Periodic disturbances of cyclone, drought fire and man appear most potent to the distribution and succession of forest types when operating in close association. -from Authors
Indonesia has extensive areas of post-extraction secondary forests and degraded lands-arising from intensive exploitation of forest resources in recent decades. Using the area of forests resulting from selective logging practices as an estimate, in year 2000, post-extraction secondary forests covered about 23 million ha, or about 55% of the total concession area. This paper analyses the underlying causes of transformation of primary to secondary forests and degraded lands, including policy and regulations in forestry and forest resources, poor enforcement of regulations, and the lack of recognition of timber exploitation rights for local communities. The government is committed to promoting participation of local communities in managing forests. Recent policy changes for ameliorating some of the degrading factors have resulted in increased pressure on secondary forests due to rampant illegal logging and use claims by local communities and land speculators. While the largest proportion of post-extraction secondary forests has been maintained as part of the permanent forest estate, substantial areas have been converted for swidden agriculture, industrial tree and estate crop plantations and transmigration areas. Local community involvement and an understanding of the underlying degradation pressures would be imperative for the effective rehabilitation and sustainable management of post-extraction secondary forests.
Ridges in the lower montane rain forests of Puerto Rico and the Lesser Antilles from St. Kitts to Grenada are dominated by tabonuco (Dacryodes excelsa Vahl), a long-lived tree adapted to recurrent hurricanes. The oldest tabonuco trees in Puerto Rico appear to survive 500 to 600yrs in forests that periodically (perhaps every 50 to 60yrs) lose nearly one-fifth of their biomass. Post hurricane-recovery, characterized by greater rates of stem ingrowth and mortality, showed an immediate and abundant regeneration of yagrumo hembra (Cecropia schreberiana Mig.) along with numerous small-to medium-sized species in forest openings. Stem density, species numbers, and the rate of biomass accumulation are at a maximum 15yrs after the hurricane; about 50yrs later, most of the secondary species associated with past forest disturbance have disappeared and the rate of biomass accumulation becomes asymptotic.
The 1980 eruption of Mount St. Helens destroyed dense forests of evergreens and clear, cold streams and lakes, producing an apparently sterile landscape, but ecological recovery has been generally rapid. Three years later, 90% (>230) of the plant species that originally inhabited the area could be found, although dominance has sometimes changed drastically. The complex event of the eruption shows that no simple model of ecological recovery fits the whole array of processes. -from Authors
Large-scale, catastrophic fires have become a significant and visible part of the tropical forest landscape in the past two decades with increased commercial exploitation of forests, forest conversion and increased population pressure. Secondary forests are an increasingly prominent feature of tropical landscapes and fires play a significant role in both the creation and destruction of these forests. In the past two decades large-scale forest fires have become more frequent in the moist tropics. In addition to climatic factors, the nature of tropical forests appears to be changing and becoming, as a consequence, more predisposed to burning. Secondary forests arising from intensive logging, in particular those that are in a degraded condition, are particularly vulnerable to repeated burning and further degradation. There has been limited general success in fire prevention and rehabilitation of secondary forests affected by fire. In addition, forest policy is not yet sufficiently attuned to address the management needs of the ever-increasing area of secondary forests affected by or developing following fire. Little is known about the exact extent and economic value or potential of post-fire secondary forests in Asia. It is clear, however, based on the experience of the past two decades, that there has been a significant increase in secondary forest affected by fire, particularly in Indonesia. Rough estimates for Indonesia infer that there could be as many as 5 million ha of post-fire secondary forests following the 1997-98 fires. Based on this knowledge alone, it would seem that post-fire secondary forest is already an important forest type that will provide important goods and services both to the environment, the state and local communities alike, as the area of primary forest diminishes through over-exploitation and conversion.
This paper provides the general objectives of the Special Issue: Secondary forests in Asia: their diversity, importance and role in future environmental management. It provides a brief overview of the renewed attention to tropical secondary forests and sketches the history of research on this subject. The paper introduces two analytical tools that are used throughout this Special Issue to better understand the current situation and trends of secondary forests in Asia: a typology of tropical secondary forest in Asia, and a conceptual framework that explains the formation and dynamics of these forests. It then outlines some of the main messages that emerge from discussions in the various papers and ends with recommendations for actions and needs for future research.
Guanica Forest, with seasonal rainfall averaging 860 mm annually, is among the driest of tropical or subtropical forests studied to date. It is composed of over 12,000 live tree stems per hectare, only 2.3 and 12 percent of which exceed 10 cm DBH or 5 m in height, respectively. Of all stems greater than 2.5 cm DBH, 57 percent are stump or root sprouts, attributable to forest cutting 50 years earlier. The dry winter months induce maximum deciduousness and are reflected in a 50 percent reduction in leaf area index, from approximately 4.3 to 2.1. Although less in magnitude, leaf fall was also observed in the moderately dry midsummer months. Relative to wetter forests, tree species richness and total community biomass is low. Approximately 50 percent of the total live-plant biomass of 89.9 t/ha occurs below ground, a higher proportion than for any other comparable forest measured thus far.
The incidence and importance of fire in the Amazon have increased substantially during the past decade, but the effects of
this disturbance force are still poorly understood. The forest fire dynamics in two regions of the eastern Amazon were studied.
Accidental fires have affected nearly 50 percent of the remaining forests and have caused more deforestation than has intentional
clearing in recent years. Forest fires create positive feedbacks in future fire susceptibility, fuel loading, and fire intensity.
Unless current land use and fire use practices are changed, fire has the potential to transform large areas of tropical forest
into scrub or savanna.
Weeds established just as readily in plots with Manihot esculenta (the principal crop plant of the region) present as in plots with M. esculenta removed. Repeated farm-plot weedings caused woody plants to decline in numbers and biomass and herbaceous plants to increase. Forbs and grasses dominated immediately following farm site abandonment, but by one year these had begun to senesce and fast-growing successional woody species (particularly Vismia spp) were common. Standing crop biomass at one year was 773 g dry weight m-2. Several microhabitat types were present on abandoned farm sites. Grasses and forbs showed no microhabitat preference, whereas successional woody individuals had their best establishment near slash and under fruit trees. -Authors
Native forest species exhibit a well-known range of ecological roles with respect to natural disturbance regimes, from pioneer phase to mature phase, and they regenerate from a range of sources, including dormant seeds, seed rain, pre-established juveniles, and resprouts from damaged adults. In contrast, the ecological roles of invasive, non-indigenous species in forest communities after natural disturbances are not well understood. Some previous studies of invasive species have emphasized their weedy nature and their ability to colonize anthropogenic disturbances. Tropical hardwood hammock forests in southern Florida experience frequent disturbance by hurricanes. Our studies of forest regeneration during two years following a recent severe hurricane suggest that invasive non-indigenous forest species exhibit the same range of ecological roles as native forest species and compete with native species for particular kinds of regeneration opportunities. To study ecological roles of non-indigenous species in regenerating forests after Hurricane Andrew, we set up four large study areas at each of three study sites that had differing amounts of hurricane-caused canopy disturbance. There were two pairs of 30 x 60 m research plots per site, and in each pair there was one control plot and one restoration plot; restoration areas were subject to an aggressive management program, focused on reducing non-indigenous vine cover. Within these study areas we subsampled vegetation in small study plots that were regularly spaced, and conducted vegetation censuses in April (the end of the dry season) and October (the end of the rainy season) for 2 yr, beginning in April 1993. We found that the source of regeneration for forest species was dependent upon the amount of canopy disturbance, the time since disturbance, and the autecology of the constituent species. Overall, 28% of the 90 species were non-indigenous: 34% of the vines (N = 32) and 24% of other life-forms (N = 58). Non-indigenous vines seemed to have a special role; not only could they compete with native vines, but they could also negatively affect the regeneration of other natives from a diverse array of sources including pre-established juveniles and resprouts from damaged adults. Both native and non-indigenous vine cover in unmanipulated study areas increased following the hurricane. Non-indigenous vine species had higher cover than native vine species, and many species formed dense "blankets." Non-indigenous species in general (not just vines) did not differ significantly from native species in seed mass, nor were they restricted to the pioneer type of life history. Many non-indigenous species had invaded forests prior to hurricane disturbance and had their own banks of pre-established juveniles; others recruited from dormant seeds, seed rain, and/or resprouts from pre-established adults. Based on information on source of regeneration and impact on native species, we propose a classification scheme for functional roles of non-indigenous invasive species in forests. To investigate whether non-indigenous taxa had roles in other geographic regions similar to those they had in Florida, we reviewed literature for 50 taxa belonging to genera that have species known to be invasive in southern Florida. We found that these taxa were invasive or had congeners that were invasive in other geographic regions (Western Australia, the Mariana Islands, Hawaii, the Mascarene Islands, and South Africa). We propose that taxa predominantly retain their invasive, functional-role type across regions. Thus, studies of ecological roles of invasive species with respect to natural disturbance regimes in one region may help us predict invasive roles in other regions.
The problem of scale has been a critical impediment to incorporating important fine-scale processes into global ecosystem models. Our knowledge of fine-scale physiological and ecological processes comes from a variety of measurements, ranging from forest plot inventories to remote sensing, made at spatial resolutions considerably smaller than the large scale at which global ecosystem models are defined. In this paper, we describe a new individual-based, terrestrial biosphere model, which we label the ecosystem demography model (ED). We then introduce a general method for scaling stochastic individual-based models of ecosystem dynamics (gap models) such as ED to large scales. The method accounts for the fine-scale spatial heterogeneity within an ecosystem caused by stochastic disturbance events, operating at scales down to individual canopy-tree-sized gaps. By conditioning appropriately on the occurrence of these events, we derive a size-and age-structured (SAS) approximation for the first moment of the stochastic ecosystem model. With this approximation, it is possible to make predictions about the large scales of interest from a description of the fine-scale physiological and population-dynamic processes without simulating the fate of every plant individually. We use the SAS approximation to implement our individual-based biosphere model over South America from 15° N to 15° S, showing that the SAS equations are accurate across a range of environmental conditions and resulting ecosystem types. We then compare the predictions of the biosphere model to regional data and to intensive data at specific sites. Analysis of the model at these sites illustrates the importance of fine-scale heterogeneity in governing large-scale ecosystem function, showing how population and community-level processes influence ecosystem composition and structure, patterns of aboveground carbon accumulation, and net ecosystem production.