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Inter-annual variability in Prosopis caldenia pod production in the Argentinean semiarid Pampas: A modelling approach
... The inter-annual productivity of pods and seeds is more linked to climate variables and our results indicated a cyclic production of pods and seeds by S. macrostachya depending not only on rainfall but also on endogenous factors of regulation (e.g., a period of low production following a period of high production). Our results are consistent with the findings of Risio et al. (2016) who found that climate (precipitation and temperature) had a strong influence on the flowering-fruiting of Prosopis caldenia (Leguminoseae family) and on the inter-annual variability of the final pod production at the tree level. Some authors found that the level of fruit production was dependent on the amount of rainfall received in the preceding year (Kelly et al., 2011). ...
Senegalia macrostachya, ex-Acacia macrostachya is a multiple-use species providing many benefits to populations in arid and semi-arid regions. Despite its importance, limited research has been undertaken on its silviculture, growth, and productivity in plantations or in the wild. In this paper, we widely deployed the Generalized Additive Models for Location, Scale and Shape to identify factors controlling the temporal variability in S macrostachya annual pod and seed production. Data (survival rate, basal diameter, total height of each individual tree,
and weight of pods and seeds produced) were collected from a factorial experiment testing different nursery production periods and the field performance of S. macrostachya under well-watered and water-stressed conditions. Long-term climate data were analyzed and the Standardized Precipitation–Evapotranspiration Index (SPEI) was calculated. Results showed that seedling survival and both height and radial growth were significantly influenced by seedling age at outplanting, watering, and climate aridity. The watered seedlings had the highest survival rate and grew taller than the non-watered seedlings. The watered seedlings also had the largest basal diameters, along with the highest pod and seed weights. There was temporal variation in S. macrostachya pod and seed production over time, indicating a cyclic production, depending mainly on climate factors. Seedling age at outplanting, early watering of outplanted seedlings, and climate aridity significantly influence not only seedling survival and growth parameters but also determine the levels of pod and seed production of S. macrostachya. Our results provide field-based evidence of the performance of this important species in the production of pods and seeds. The results also highlight the potential for domestication of S. macrostachya including use in plantations to help restore degraded rural landscapes in arid and semi-arid regions.
... En particular para los bosques y montes bonaerenses, se posee información fragmentada y escasa sobre almacenaje de C en biomasa y suelos y ninguna información sobre los flujos de GEI en la interfase suelo-atmósfera, así como su relación con el clima y/o el manejo y uso. En trabajos previos se analizaron tasas de crecimiento de leñosas y su respuesta ante eventos climáticos, o cambios en la productividad o supervivencia en relación a la fluctuación de aguas subterráneas (Bogino y Jobbágy, 2011;Risio, 2016). Sin embargo, dicha información representa una vacancia en el conocimiento en el ambiente de trabajo propuesto. ...
The objective of this study was to evaluate the productive and mitigation capacity of greenhouse gas emissions (GHG) of agroecosystems located in the Espinal Periestético, south of the province of Buenos Aires, by comparing contrasting vegetable cover (woody and herbaceous). To do this, three sampling sites were selected in Villarino and Patagones. Inventories of woody species, the dynamics of water at different soil depths, and forage productivity were carried out and methane concentration profiles (CH4) and potential oxidation rates of CH4 in laboratory conditions were analyzed. Tree density varied between 820 and 1088 individuals.ha-1, a higher value compared to the data of the Second National Inventory of Native Forests. Besides, it was found that forage species presented greater aboveground biomass compared to non-forage ones. As for the dynamics of soil water, differences were observed according to plant cover and soil depth. Finally, CH4 concentration profiles revealed different patterns between sites and vegetable cover. The results highlight the importance of considering plant cover and water dynamics in the sustainable management of these systems, thinking about their potential to reduce GHG emissions.
... Similar results were found by García-Mozo et al. [36] in Mediterranean ecosystems, where periods of high environmental humidity directly influence pollen and fruit production in the genus Quercus. Furthermore, we observed high intraspecific variability in fruit production, consistent with the findings of Laouali et al. [37] and Risio et al. [38]. These trends seem to be common in the genus Prosopis and tend to be associated with the high genetic variability that can be found at the population level in the species belonging to both sections Strombocarpa and Algarobia of this legume genus [39]. ...
Prosopis strombulifera is a widely distributed woody species distributed along arid ecosystems in America. The interannual evolution of ecophysiological parameters and their effects on fruit production and flower sprouting in Prosopis strombulifera were studied for three years in a natural population distributed in the Atacama Desert. Xylem water column tension, pressure-volume curves, specific leaf area (SLA), and chlorophyll fluorescence parameters were assessed. Flower sprouting was assessed in different weeks using tagged flowers. To assess fruit production, four small containers were placed under twenty-five individuals, allowing the estimation of total annual production and individual production. We found considerable variability between years and between individuals. Positive relationships were found between plant water parameters, SLA, and chlorophyll variables measured in spring at flower sprouting and during fruit production. A negative correlation was found between the mean of the minimum temperatures in spring and flower sprouting. These results suggest that spring ecophysiological parameters strongly affect the reproductive status of P. strombulifera. The results also reflect the potential of this species to adapt to a hyperarid climate by preserving a high relative water content before flower sprouting.
... Similar results were found by García-Mozo et al. [36] in Mediterranean ecosystems, where periods of high environmental humidity directly influence pollen and fruit production in the genus Quercus. Furthermore, we observed high intraspecific variability in fruit production, consistent with the findings of Laouali et al. [37] and Risio et al. [38]. These trends seem to be common in the genus Prosopis and tend to be associated with the high genetic variability that can be found at the population level in the species belonging to both sections Strombocarpa and Algarobia of this legume genus [39]. ...
Prosopis strombulifera is a widely distributed woody species distributed along arid ecosystems in America. The interannual evolution of ecophysiological parameters and their effects on fruit production and flower sprouting in Prosopis strombulifera were studied for three years in a natural population distributed in the Atacama Desert. Xylem water column tension, pressure-volume curves, specific leaf area (SLA), and chlorophyll fluorescence parameters were assessed. Flower sprouting was assessed in different weeks using tagged flowers. To assess fruit production, four small containers were placed under twenty-five individuals, allowing the estimation of total annual production and individual production. We found considerable variability between years and between individuals. Positive relationships were found between plant water parameters, SLA, and chlorophyll variables measured in spring at flower sprouting and during fruit production. A negative correlation was found between the mean of the minimum temperatures in spring and flower sprouting. These results suggest that spring ecophysiological parameters strongly affect the reproductive status of P. strombulifera. The results also reflect the potential of this species to adapt to a hyperarid climate by preserving a high relative water content before flower sprouting.
... In particular, Prosopis sp. fruits can be used to make flour of high nutritional value, as supplements for human consumption and cattle fodder (Pérez et al., 2020;Risio et al., 2016). In 2016, Argentina had a production of 7000 t of wood from Prosopis caldenia, Prosopis alpataco and Prosopis flexuosa (MAyDS, 2016), which shows that in the long-term the proposed woodland could also enhance incomes in the area under study. ...
We present a management project for the mitigation of extreme climatic events in the frame of cyclic wet and dry periods in the semiarid Pampean region of Argentina. The developed methodological approach allows quantitative planning of strategies to tackle the effect of recurrent floods and droughts in a salt lake basin through the formulation of an optimal control problem, which constitutes a novel approach to ecohydrological systems management. The control variables correspond to (i) diversion flows from a lake tributary to an artificial freshwater reservoir to damp lake flooding, (ii) freshwater flows from the reservoir to the salt lake to keep its salinity at desired values and (iii) freshwater flows to irrigate crops during drought periods. Further, we address the economic valuation of ecosystem services in the basin. Quantitative results provide useful insights on optimal management strategies and the effects of their implementation, as well as their impact on the valuated services in the watershed under study.
... Sin embargo, si se quieren conservar otros servicios ecosistémicos y una mayor proporción de su diversidad funcional del bosque nativo, deberían incluirse lotes destinados a regeneración natural en los que se podría realizar cortas intermedias, extracción selectiva de madera, leña, miel, plantas medicinales y ornamentales, lo cual tendría menor impacto ambiental sobre los bosques respecto a la tala rasa o clareos con rolados (manejo tradicional: destinar la tierra a agricultura o bien bosque con uso ganadero). Esta sería una propuesta de manejo alternativa con usos múltiples de los bosques, la que también requiere de un plan de manejo detallado (Coirini et al., 2013;Risio et al., 2016). ...
Se presenta el estado de los bosques del Espinal, analizando la estructura y funcionamiento de los principales tipos de unidades de paisaje. Se discuten los principales cambios a nivel del paisaje relacionados con el manejo histórico del territorio y aspectos socioecológicos vinculados a los cambios en el uso de la tierra. Se presentan los tratamientos silvícolas y técnicas de manejo silvicultural que se han realizado o se realizan en esta región, evaluando los distintos factores ecológicos, sociales y económicos relacionados a la pérdida de bosque nativo. Se discuten distintas éticas ambientales en relación con valoraciones de los bosques para así analizar posibles manejos silviculturales en el bosque nativo que posibiliten la conservación de la biodiversidad en los agro-ecosistemas del Espinal. Finalmente, se presentan algunas prioridades en la generación de nuevos conocimientos necesarios para el manejo silvicultural sostenible y se incluyen recomendaciones para mejorar la conservación y la silvicultura en los bosques del Espinal y el buen vivir de la sociedad
... El ACP mostró que la variabilidad observada entre las colectas se asocia a la morfología de las hojas, espinas y vaina, sin tener un efecto considerable por la localidad de la colecta; las colectas CO2, CO7 y LL1 mostraron tamaño medio de foliolos de 0.43 cm y longitud media de vainas de 11.05 cm, valores por debajo de los rangos descritos para P. laevigata (Palacios, 2006), mientras que las colectas BV2, BV3 y BV5 presentaron una longitud promedio de los foliolos de 0.78 cm, hacia el límite superior asociado a P. laevigata; además, se observó floración tardía en el mes de julio en las colectas CO3, CO4 y CO7, dado que en México la floración suele ocurrir entre marzo y mayo (Rodríguez et al., 2014). No obstante, se debe considerar que la extensión de floración y fructificación puede variar de individuo a individuo e incluso de un año a otro (Risio et al., 2016). ...
p> Objetivo: evaluar la amplitud de la variabilidad morfológica del mezquite de la región de Pénjamo, en función de las características con mayor valor descriptivo.
Método: a partir de 32 colectas de mezquite en siete localidades de Pénjamo, Guanajuato, se midieron 20 caracteres morfológicos cualitativos (7) y cuantitativos (13) que fueron analizados por componentes principales (ACP) y conglomerados (AC).
Resultados: la caracterización morfológica permitió diferenciar dos grupos y cinco subgrupos basados en el tamaño de la vaina y área foliar.
Limitaciones: considerar factores bióticos, abióticos y antropogénicos que puedan contribuir a explicar la variación observada.
Principales hallazgos: la longitud y ancho del foliolo, pinna y vaina son los principales contribuyentes a la variación cuantitativa, mientras que en características cualitativas la fuente principal de variación fue la posición y arreglo de las espinas, así como la presencia de flores. El ACP indica que el tipo de suelo del lugar de colecta se asoció a la variación cualitativa del mezquite.</p
... Risio et al. [26] applied ZILN for the Prosopis caldenia pod production data at tree level in the Argentinean semiarid pampas. Tong et al. [27] suggest a zero-adjusted gamma model for mortgage loan loss given default contained extensive numbers of zeroes. Neelon et al. [28] employed ZIP model with spatial effects to examine emergency department visits. ...
Railway accidents are critical issues characterized by a large number of injuries and fatalities per accident due to massive public transport systems. This study proposes a new approach for evaluating the damages resulting from railway accidents using the two-part models (TPMs) such as the zero-inflated Poisson regression model (ZIP model) and the zero-inflated negative-binomial regression model (ZINB model) for the non-negative count measurements and the zero-inflated gamma regression model (ZIG model) and the zero-inflated log-normal regression model (ZILN model) for the semi-continuous measurements. The models are employed for the evaluation of the railway accidents on Korea Railroad, considering the accident damages, such as the train delay time, the number of trains delayed and the cost of considering the accident count responses, for the period 2008 to 2016. From the results obtained, we found that the human-related factors, the high-speed railway system or the Korea Train Express (KTX) and the number of casualties, are the main cost-escalating factors. The number of trains delayed and the amount of delay time tend to increase both the probability of incurring costs and the amount of cost. For better evaluation, the railway accident data should contain accurate information with less recurrence of zeros.
... In addition, the fruit is a fodder highly desired by native fauna and livestock, because of its carbohydrates wealth. Nevertheless, their inter-annual production and their spatial distribution are very variable (Menvielle and Hernandez 1985;Risio et al. 2016). As a heliophyte species, open areas favour its growth , and it responds vigorously to early thinning treatments and pruning (Amieva 2013). ...
This chapter gathers six species that have been extensively used from the natural forest, but that are not included in any domestication programme yet. These species from the Chaco region belong to genera Acacia, Prosopis and Gonopterodendron. Main characteristics of the different species such as botanical, ecological and usage features (timber and non-timber forest products) are described. Natural range of each species is also depicted. The state of knowledge of the molecular genetic diversity and reproductive biology is shown together with the available information about the mating system. Landscape genetic structure analyses among populations of different Acacia species revealed high levels of differentiation. Experiences of germination and plantation, although scarce, give promising results. Special sampling methods for conservation, management and deployment are discussed together with particular genetic considerations for their use in restoration programmes. We call attention to the relevance of these species for their future inclusion in domestication efforts.
... Several models for the NTFP yields have been developed for forest management planning purposes also outside Europe. Models are available for several important NTFPs, for instance pine nuts (Pinus koraiensis) [108], cork [109], rattan (Calamus caesius) [110], bamboo (Yushania alpina) [111], rubber (Hevea brasiliensis) [112], pods (Prosopis caldenia) [113], cranberry (Vaccinium macrocarpon) [114], medicinal plants [115] and maple syrup (Acer saccharum) [116]. The modelling work done in Europe and elsewhere shows how NTFPs can be considered in forest management planning to evaluate the potential of multi-functional forest management. ...
Purpose of Review
The increased popularity and commercial use of non-timber forest products (NTFPs) calls for the development of models for NTFPs to include their predicted yields in forest management planning and to evaluate the potential of multi-functional forest management. This study assesses and discusses the current state of the art and trends in NTFP yield modelling in Europe and the integration of the models in multi-functional forest management planning at different spatial scales.
Recent Findings
Climate-sensitive empirical yield models already exist not only for a variety of NTFPs that are economically important to forest owners (e.g. cork and pine nuts) but also for wild-gathered berries and mushrooms, the harvesting of which cannot be controlled by the forest landowner in all European countries. Several studies on multi-functional forest management planning consider the economic profitability of the joint production of timber and NTFP. Harvesting NTFPs can create significant additional incomes for forest owners, compared with timber production only. However, maximizing the economic returns from the joint production of timber and NTFPs often calls for changes in forest management practices.
Summary
Continued efforts in modelling and predicting the yields of NTFPs have enabled forest managers to further expand the analyses of multi-functional forest planning and management in Europe. Climate-sensitive models also allow analyses on the potential effects of climate change on NTFP yields. New models and forest management practices are still needed for tree fruits, birch sap, a wider variety of wild edible mushrooms, specialty mushrooms cultivated on live trees as well as medicinal and edible forest herbs harvested for commercial value in Europe.
... Seeds deposited on the soil surface rarely germinate due to dehydration as observed for Prosopis ferox Griseback and Prosopis flexuosa DC. across semiarid regions of Argentina and Sudan (Campos et al., 2011;Morandini, Giamminola & Viana, 2013;Yoda et al., 2015). High Prosopis caldenia Burkart seed mortality has also been related to soil water availability reduction across semiarid rangelands of Central Argentina (De Villalobos, Peláez & Elia, 2005;De Villalobos & Peláez, 2015;Risio et al., 2016). ...
Background:
Biological invasion is one of the main threats to tropical biodiversity and ecosystem functioning. Prosopis juliflora (Sw) DC. (Fabales: Fabaceae: Caesalpinioideae) was introduced in the Caatinga dry forest of Northeast Brazil at early 1940s and successfully spread across the region. As other invasive species, it may benefit from the soils and seed dispersal by livestock. Here we examine how seed dispersal ecology and soil conditions collectively affect seed germination, early seedling performance and consequently the P. juliflora invasive potential.
Methods:
Seed germination, early seedling survival, life expectancy and soil attributes were examined in 10 plots located across three habitats (flooding plain, alluvial terrace and plateau) into a human-modified landscape of the Caatinga dry forest (a total of 12,000 seeds). Seeds were exposed to four seed dispersal methods: deposition on the soil surface, burial in the soil, passed through cattle (Boss taurus) digestive tracts and mixed with cattle manure and passed through mule (Equus africanus asinus × Equus ferus caballus) digestive tracts and mixed with mule manure. Seeds and seedlings were monitored through a year and their performance examined with expectancy tables.
Results:
Soils differed among habitats, particularly its nutrient availability, texture and water with finely-textured and more fertile soils in the flooding plain. Total seed germination was relatively low (14.5%), with the highest score among seeds buried in the flooding plain (47.4 ± 25.3%). Seed dispersal by cattle and mule also positively impacted seed germination. Early seedling survival rate of P. juliflora was dramatically reduced with few seedlings still alive elapsed a year. Survival rate was highest in the first 30 days and declined between 30 and 60 days with stabilization at 70 days after germination in all seed treatments and habitats. However, survival and life expectancy were higher in the flooding plain at 75 days and lower in the plateau. Prosopis juliflora seedling survival and life expectancy were higher in the case seeds were mixed with cattle manure.
Synthesis:
Prosopis juliflora seeds and seedlings are sensitive to water stress and habitat desiccation. Therefore, they benefit from the humid soils often present across human-disturbed flooding plains. This plant also benefits from seed deposition/dispersal by livestock in these landscapes, since cattle manure represents a nutrient-rich and humid substrate for both seeds and seedlings. The quality of the seed dispersal service varies among livestock species, but this key mutualism between exotic species is due to the arillate, hard-coated and palatable seeds. Prosopis juliflora traits allow this species to take multiple benefits from human presence and thus operating as a human commensal.
... Flowering processes are influenced by numerous physiological (carbohydrate reserves, hormonal content) and climate factors (temperature, rainfall, relative humidity, photoperiod and water availability) (Villagra et al., 2010). In this context, Prosopis species of semiarid habitats produce abundant flowers at a predictable time of the year, and temperature seems to be the most predictable weather parameter correlated with reproduction variables in nonphreatophyte Prosopis species (Risio et al., 2016). Nonetheless, this hypothesis has not been widely tested on phreatophyte species of the Prosopis genus. ...
Prosopis burkartii is a critically endangered phreatophyte legume endemic to the Atacama Desert of northern Chile where only 50 individuals remain. We studied seasonal water variables and flower parameters in a population of 15 P. burkartii individuals. For each tree, xylem water potential (Ψ) was estimated by measuring two twigs with a Scholander pressure bomb. Each month, we made 3 measurements of xylem Ψ in each tree: pre-dawn (Ψpd), midday (Ψmd), and late-afternoon (Ψla). We also measured pre-dawn hydraulic conductivity (K) and the percent loss of hydraulic conductivity (PLC) on the same trees. Flower parameters were estimated using tagged twigs. The total number of flowers produced by each plant, the number of pods per plants, number of fertile pods and the percentage of abortion of flowers and pods were estimated. Values of Ψ ranged from-2.7 ± 0.1 (July) to-0.8 ± 0.2 MPa (September). On a daily basis, individuals had maximal Ψ at pre-dawn and minimal Ψ at midday, with a recovery of Ψ during the late-afternoon likely due to the low evaporative demand at that time. Furthermore, the native conductance of the stems (Ki) had inverse trends in comparison with PLC data. Number of flowers per plant was strongly correlated with Ψmd estimated during October. During the study period, we observed that Ψmd had higher values during the spring and at the beginning of summer, indicating maintenance of a favorable plant water status during the season of flowering at the time of day when thermal stress is greatest. The differences in PLC suggest that individuals of P. burkartii can maintain functional xylem conduits during summer droughts and extract water from the soil while maintaining high values of midday the period of the day with the greatest stress. 3
The arid and semi-arid areas in Argentina occupy more than the sixty
percent of the country. The genus Prosopis dominates these environments
with approximately 21 species. The driest part of the Argentinean Pampas
is dominated by caldén (Prosopis caldenia) forests which cover
approximately 27,000 km2. For many years, caldén woodlands were
considered as a main source of wood due to its praiseworthy quality. At the
beginning of the last century it was widely used as railroad firewood and
for paving the streets of Buenos Aires, the capital city of Argentina. As a
result, only 18% of the original area of these forests remain nowadays.
Today, new paradigms allow us to value the caldén forests not only for
their wood but also for the many services that they can provide such as
food, medicinal products, dyeing materials, apiculture, regulation of water
basins, stabilization of sandy soils, recycling of nutrients, carbon sink,
forage for livestock and recreation. In a context of global change, the fact
that these forests are a refuge for a large proportion of mammals and birds
emphasizes their value as a source of biodiversity. Despite the many
functions that these forests have and regardless of the ecosystem services
that they provide being valued at USD 2,000 ha-1, they are currently
subject to the highest deforestation rates in Argentina. Valuing these
forests is a complex task and challenge in a globalized economy that
constantly struggles between productive systems which require the
replacement of forests and the need to preserve them for the generations to
come.
Nothofagus obliqua forests in Argentina extend over a wide latitudinal gradient but highly fragmented and locally restricted. The relevance of this species relies in its high wood quality and tolerance to warmer niches, as those predicted under climate change. In this chapter, we describe the species characteristics and natural distribution range as well as the natural hybridisation process that occurs frequently with other Nothofagus species. Genetic variation patterns based on neutral genetic markers (isozymes, cpDNA and microsatellites) allowed inferring past demographic changes during the Pleistocene glaciations. In addition, the level of genetic diversity was used as an indicator for conservation and for the definition of genetic zones as seed sources for breeding and restoration. Quantitative genetic variation and phenotypic plasticity measured at seeds, seedling and juvenile states on nursery and field trials gave insights about adaptation. The first steps towards breeding of roble pellín in Argentina are fully described: provenance and progeny tests and seed producing areas, both natural and cultivated ones. Intra- and interspecific-controlled crossings of N. obliqua represent a fundamental step towards the breeding of this species, and the first achievements are described.
This study explores the effects of year and location on reproductive traits and flowering phenology in Retama raetam populations growing in a hyper-arid environment. Besides year, season, and location, variations in the soil seed bank were also evaluated. Germination percentage of seeds buried in soil at two different depths for one year was determined. I hypothesized that changes in water availability between years and locations would lead to variations in reproductive traits, flowering phenology, and the seed bank of R. raetam. The study was conducted at a midstream and an upstream location during 2013 and 2014 in Wadi Rishrash in the Eastern Desert of Egypt. Flower, fruit, and seed production were significantly higher in the midstream location than the upstream location and in 2014 than in 2013. Flowering onset and duration did not differ significantly between locations. Flowering occurred earlier in 2014 than in 2013 at both locations, and the flowering period was longer in 2014 than in 2013. The size of the seed bank was greater at the midstream than at the upstream location, and in summer than in spring season. Germination of seeds decreased with burial depth, but increased with burial duration. Larger individuals produced more seeds and flowered earlier than smaller plants. The size of plant was also positively correlated with flowering duration. The location and temporal variations in all these traits may be related to environmental differences between locations and differences in annual precipitation.
The seasonal and diurnal water relations were compared among six desert phreatophytes, two evergreen shrubs, and one deciduous shrub. All species were located in one wash woodland in the Sonoran Desert of southern California. There are several mechanisms by which these Phaenicia have adapted to the desert environment. One group of winter-deciduous phreatophytes (Olneya tesota, Prosopis glandulosa, and Acacia greggii) experienced summer midday leaf water potentials below -4.0 MPa. These phreatophytes had a series of physiological mechanisms for tolerating summer water stress, including seasonal and diurnal osmotic adjustment and the maintenance of high leaf conductance at low leaf water potential. Osmotic adjustment of these three phreatophytes was similar to or greater than that of two evergreen species (Larrea tridentata and Simmondsia chinensis). Dalea spinosa, a stem-photosynthetic phreatophyte, avoided water stress by maintaining a very small leaf area. The summer-deciduous phreatophytes (Hyptis emoryi, and Chilopsis linearis) demonstrated mechanisms of drought avoidance such as change in leaf biomass and low summer leaf conductance. Little osmotic adjustment occurred in the summer-deciduous phreatophytes. The phreatophytic species studied in this investigation have evolved adaptations to water stress that are similar to those of deciduous and evergreen shrubs of the Sonoran Desert. Desert phreatophytes are a complex group of species with varied adaptive mechanisms to tolerate or avoid drought and should not be considered simply as a group of species that avoid desert water stress by utilizing deep ground water unavailable to other desert species of drought tolerance and avoidance.
Los cambios más importantes registrados en la distribución del caldén (Prosopis caldenia Burkart) en la región semiárida central de Argentina, Incluyen el aumento de la densidad de esta especie y la invasión de pastizales naturales. Los factores causales y la dinámica de estos cambios no han sido detalladamente estudiados. En este trabajo se relaciona la dinámica de dos poblaciones de caldén con factores tales como manejo, fuego y precipitaciones. Se eligieron como áreas de estudios una planicie cuya vegetación original era un pastizal (sitio 1) y un bosque de caldén que originalmente fue una sabana (sitio 2). En cada sitio se determinaron los patrones espaciales en base a transectas y las tasas de Implantación las cuales fueron inferidas por dendroecologia. Las densidades estimadas fueron 586 y 1259 plantas/ha, para el sitio 1 y 2 respectivamente. No se encontraron evidencias de agrupamiento para la escala espacial de este estudio (p=0.52, sitio 1 y p=0.08, sitio 2 para n=112). Las edades de los individuos muestreados comprendieron un rango de 3 a 65 años en el sitio 1 y de 8 a 55 años en el sitio 2 (en este sitio 2 solo fueron muestreadas las plantas con diámetro menor de 30 cm). Primariamente los dos sitios fueron utilizados para erra de ovinos; durante ese periodo, las tasas de establecimiento fueron 0.99 plantas/ha/año (16 años) en el sitio 1, Y 10 plantas/ha/año (15 años) en el sitio 2. Posteriormente luego de diez años desde la introducción del ganado vacuno, las tasas ascendieron a 12.7 y 48.5 plantas/ha/año respectivamente. Un evento de fuego fue registrado en cada sitio (1980 en el sitio 1 y 1964 en el sitio 2) pero este factor no alteró la tendencia ascendente de la densidad. En el sitio 2 el Incendio fue contemporáneo con la introducción del ganado y coincide a su vez con un importante incremento en el establecimiento. No se encontró relación entre la dinámica de la población de caldén y las fluctuaciones en la precipitación anual o estacional. Las variaciones registradas en las tasas de establecimiento coincidieron con cambios en el manejo ganadero, confirmando la Importancia del ganado en la dispersión de las semillas de caldén.
Resúmenes de Trabajos presentados en otras publicaciones (por docentes de la U.N.L.Pam.) Publicado en JOURNAL OF RANGE MANAGEMENT, 51 (6), November 1998
In a semiarid sedimentary catchment of central Argentina, we describe a recent process of landscape dissection, abrupt canyon and watercourse formation and soil salinization. We link these adverse hydrological and geomorphological transformations to three potentially important drivers: precipitation increase, seismic activity and deforestation. Remote sensing imagery in the last 48 years showed an exponential increase in the length of streams, with drainage density values tripling to reach 0.22 km km 2 . During the same period, forest area declined from 47% to 10%, at the expense of agriculture expansion. A 3.4-fold expansion of surface water bodies and water table level raise of 0.15 m y À1 over the last 35 years was observed. Discharge of a new stream at the middle of the basin ranged between 0.25 and 0.45 m 3 s À1 accompanied by a large and stable load of salts (~0.7 g l À1). Nil recharge and large vadose accumulation of salts in dry forests stands contrasted with recharge rates of ~16 mm y À1 and salt-leached profiles under agriculture. Although the process of landscape dissection occurred during decades of higher than average precipitation, extreme rainfall events and seismic activity were not exceptional in that period. Results suggest that the replacement of forests by annual crops played a more important role, reducing evapotranspiration, triggering the onset of groundwater recharge and favouring subsurface through piping/ sapping processes. The abrupt landscape dissection shows no signs of stabilization at the present and may only be ameliorated through changes in vegetation that restore the original non-flow condition of the forest.
Prosopis glandulosa var. torreyana accounts for nearly 90% of the total plant cover in a mesquite woodland community near Harper's Well along the southern margin of the Salton Sea in the Sonoran Desert of California. Total above-ground biomass ranged from 43- 760 kg per plant and 1.9-8.5 kg m-2 canopy area. Stand biomass ranged locally from a high of 23,000 kg ha-1 near the wash to 3500 kg ha-1 in the fringe of this mesquite stand. Net above-ground primary production for 1980 had a mean of 2.2 kg m-2 canopy for shrub forms and 5.3 kg m-2 canopy for tree forms. Mean Prosopis stand production for 1980 was 3650 kg ha-1, an extremely high value for desert communities. This level of production is particularly high in relation to the low mean annual precipitation of c.70 mm. New woody tissues in trunk and branches accounted for 51.5% of the allocation of productivity, a remarkably high woody allocation for a desert plant. Only 33.6% of net primary production was allocated to leaves. -Authorsmesquite woodland Harper's Well Salton Sea
We present a review on the state-of-the-art of fruit prodution in Western Iberia woodlands («dehesas»), and particularly in Q. ilex (holm oak) «dehesas». This threatened ecosystem is of very high ecological and economical importance. Quercus sp. fruits (acorns) are essential for wildlife, and for pig fattening in «dehesas». In the first part of this review we briefly describe the phenology of the holm oak and the factors affecting acorn morphology and chemical composition. In the second half we analyze the main known factors reported in the literature that determine acorn production: pruning, stand characteristics, and site (weather and soil). We make several suggestions to improve future research and detect the existing gaps in the undertanding of acorn production. Fruit production is highly variable, both between and within years and individuals. The mean production in «dehesas» (mean density circa 50 trees/ha) is around 250-600 kg/ha (≈100 g/canopy-m 2 , CV > 100%). Acorn morphology is also very variable, with mean sound acorn size around 3.5 × 1.6 cm, CV ≈ 10% (3.5 g/acorn, CV > 50%). Silviculture plays an essential role in acorn production. Acorn production per tree seems to be negatively related to density. The effect of pruning is less clear: production seems to be reduced in the first and second years after pruning. After the third year it is not possible to discern from the literature whether there is any response to pruning or not. Weather and soil (site) also impact production and their effects should be explored in future management. The influence of genetics is unknown and should also be addressed. Longer data series are necessary. The dasometric features of the stands need to be characterized, in order to better understand production and compare results from different locations. Much research is still required to understand the functioning of fruiting in these woodlands.
Modelling masting habit, i.e. the spatial synchronized annual variability in fruit production, is a huge task due to two main circumstances: (1) the identification of main ecological factors controlling fruiting processes, and (2) the common departure of fruit data series from the main basic statistical assumptions of normality and independence. Stone pine (Pinus pinea L.) is one of the main species in the Mediterranean basin that is able to grow under hard limiting conditions (sandy soils and extreme continental climate), and typically defined as a masting species. Considering the high economical value associated with edible nut production, the masting habit of stone pine has been a main concern for the forest management of the species. In the present work we have used annual fruit data series from 740 stone pine trees measured during a 13 years period (1996-2008) in order: (a) to verify our main hypothesis pointing out to the existence of a weather control of the fruiting process in limiting environments, rather than resource depletion or endogenous inherent cycles; (b) to identify those site factors, stand attributes and climate events affecting specific traits involved in fruiting process; and (c) to construct a model for predicting spatial and temporal patterns of variability in stone pine cone production at different spatial extents as region, stand and tree. Given the nature of the data, the model has been formulated as zero-inflated log-normal, incorporating random components to carry out with the observed lack of independence. This model attains efficiencies close to 70-80% in predicting temporal and spatial variability at regional scale. Though efficiencies are reduced according to the spatial extent of the model, it leads to unbiased estimates and efficiencies over 35-50% when predicting annual yields at tree or stand scale, respectively. In this sense, the proposed model is a main tool for facilitating decision making in some management aspects such as the quantification of total amount of cones annually supplied to nut industry, design of cone harvest programs or the optimal application of seedling felling.
Population dynamics, mortality factors, growth and dry weight changes in Quercus floribunda seedlings were studied to determine the implication of sun and shade microsites and the role of mast years on regeneration and maintenance of oak forests in Kumaun Himalaya. The number of seedlings was significantly greater at the sun microsites, but seedling survival was not, as ground herbage clearance at sun microsites accounted for 53.5% mortality. Insect herbivores (e.g. acorn worm) were also one of the major mortality factors. At both microsites, most mortality was encountered between June and August. The initial seedling height at sun microsites was significantly lower compared to shade microsites. Seedlings at sun microsites were superior in terms of number of leaves and peak dry weight. Dry mass allocation in seedling components and root:shoot ratio was similar at both microsites. The study shows the importance of sun microsites and of masting in the potential for regeneration and expansion of Q. floribunda forests.
2005. Pollen collected by honey bees (Apis mellifera L.) from south of Caldén district (Argentina): botanical origin and protein content. – Grana 44: 1–8. ISSN 0017-3134. In the south of the Caldén district (Phytogeographical province of Espinal, Argentina) the availability of flowering along with the botanical origin and protein content of pollen harvested by honey bees, was studied. During two apiculture periods (from end August to early January) pollen loads were collected every fortnight using pollen traps. A total of 637.96 g of pollen loads was analysed. From 139 species recorded, only 29 were visited by honey bees. In terms of biomass the contribution of exotic plants was high at the end of the winter (Brassicaceae and Erodium cicutarium); during this period of pollen shortage, honey bees collected spores of Puccinia interveniens. During the spring, the native plants (Condalia microphylla, Chuquiraga erinacea, Discaria americana, Grindelia tehuelches, Larrea divaricata, Prosopis sp., Prosopidastrum globosum and Vicia pampicola) were utilised. Those pollen types of high protein level were collected most intensively.
Cases of mast seeding, involving highly variable seed production synchronized over large geographic areas, provide dramatic examples of resource pulses that have been documented for most major world land masses. Here, we compare the dynamic behavior of two of these systems, with the goal of understanding differences in the long-term consequences of masting events to their respective communities. Responses to mast events in deciduous oak forests in eastern North America are characteristically complex and of low resilience. That is, each event produces long-lasting cascading effects in the community, ultimately influencing not only seed consumers such as rodents and deer, but also the parasites and prey of those consumers, diseases transmitted by those parasites, and outbreaks of insect herbivores. In contrast, despite more extreme resource pulsing in New Zealand Nothofagus forests, responses to mast events there are less complex and more resilient, i.e., producing only short-term (Mustela erminea L.) in New Zealand), while other exotics showed complex dynamics (e.g., gypsy moths (Lymantria dispar L.) in North America). Thirdly, recent extinctions of species such as the passenger pigeon (Ectopistes migratorius L.), once the dominant acorn predator in eastern North American forests, have likely produced qualitative changes in system dynamics in both communities. Fourthly, the North American community has more lags and hysteresis, which probably contribute to the greater dynamic complexity in eastern North America than in New Zealand Nothofagus forests. However, positive feedback loops present in North America seem to have little influence on system dynamics. Because the massive perturbations induced by masting events are major recurring challenges to an ecosystem, disentangling the causes of different system responses is likely to lead us to a better understanding of ecosystem function, resilience and stability.
Prosopispod production was compared in 3 field trials in southern California, i.e., a typical orchard planting, an irrigation trial,
and a heat/drought stress trial. Thirteen species representing North American, South American, Hawaiian, and African germplasm
were evaluated. Hawaiian and African accessions were eliminated from the irrigation trial by a minus 5°C temperature. The
most productive pod producers were P. velutinaaccessions from southern Arizona. In the fifth season, 5 trees of the most productive accession, i.e., P. velutina32 had a mean pod production of 7.2 kg/tree with a range of 3.2–12.2 kg/tree. P. chilensisand P. albatrees of the same age were much larger but had less pod production. Trees in the driest irrigation treatment had the greatest
pod production. Pod production estimates of 3,000–4,000 kg/ha were obtained in the dry irrigation treatment by P. velutina20 which received 370 mm rainfall in the year preceding harvest.
Lentil (Lens culinaris Medikus subsp. culinaris) is traditionally grown as a rainfed crop globally, except in Sudan and Egypt, where it is grown under supplemental irrigation. Its seed is a rich source of protein for human consumption, and the straw is a valued animal feed in Near East. In the Mediterranean environment, lentil productivity is limited primarily by the amount and distribution of rainfall and temperature extremes. This study aimed to develop simple models to predict lentil seed and straw yields as a function of seasonal weather data (rainfall and temperature). Historical weather and yield trial data over 39 environments from three contrasting locations in Syria and Lebanon were used. Best-fit models for seed and straw yields in terms of climatic variables based on stepwise regression were developed. These accounted for over 77% variance in yield for both models. The overall responses to total seasonal rainfall were 5.16 kg ha−1 mm−1 seed yield and 10.7 kg ha−1 mm−1 for straw yield. Although May (period of pod-filling) rain contributed substantially to seed yield, high May temperatures reduced yield drastically. For straw yield, absolute minimum temperature and February temperature are important factors, in addition to total seasonal rainfall. The simple regression models developed from historical data not only describe the variation in lentil yields but can also be used for yield prediction purposes in the Near East.
Many terrestrial ecosystems are characterized by intermittent production of abundant resources for consumers, such as mast seeding and pulses of primary production following unusually heavy rains. Recent research is revealing patterns in the ways that consumer communities respond to these pulsed resources. Studies of the ramifying effects of pulsed resources on consumer communities integrate ‘top-down’ and ‘bottom-up’ approaches to community dynamics, and illustrate how the strength of species interactions can change dramatically through time.
In recruitment modeling, the response variable is a count and its distribution is often characterized by an excess number of zeros. As a result, standard distributions of probabilities, such as Poisson, are inappropriate. A common approach in forestry consists of using two-part conditional models. These models have two distinct components aimed to predicting the occurrence and abundance of recruitment, respectively. For such data, zero-inflated models might provide a more adequate framework by combining the two components into a joint distribution of probabilities. In this article, a conditional model is compared with two different zero-inflated models, namely, a zero-inflated Poisson (ZIP) and a zero-inflated discrete Weibull (ZIdiW) model. The three models were calibrated using a data set provided by permanent sample plots located in hardwood stands. Parsimony criteria (the Akaike information criterion and the Bayesian information criterion) and diagnostic plots were used to perform the comparison. The results show that the ZIdiW model has the best fit. The flexibility of the Weibull function and the possibility of obtaining a more parsimonious model are two advantages related to the use of a ZIdiW model in recruitment modeling.
In Fagus, full-mast seeding years are invariably followed by at least one non-mast year. Both flower and leaf primordia develop during the summer within the same winter buds. Flower bud initiation occurs when the N content of developing seeds is increasing rapidly. We hypothesized that competition for nitrogen (N) between developing seeds and buds limits flower primordium formation in mast years and, hence, limits seed production in years following mast years. We tested this hypothesis in three Fagus crenata Blume forests at elevations of 550, 900 and 1500 m. Bud N concentration (N con), amount of N per bud (N bud) and dry mass per bud (DM) were compared between a mast year (2005) and the following non-mast year (2006), and between winter buds containing both leaf and flower primoridia (BF), which were formed during the non-mast year, and winter buds containing leaf primordia only (BL), which were formed in both mast and non-mast years. In addition, leaf numbers per shoot corresponding to the analyzed buds were counted, and the effect of masting on litter production was analyzed by quantifying the amounts of litter that fell in the years 2004 to 2007. The dry mass and N content of BF formed in 2006 by trees at both 550 and 1500 m were 2.1-3.4-fold higher than the corresponding amounts in BL, although the numbers of leaves per current-year shoot in 2007 that developed from the two bud types in the same individuals did not differ significantly. These results indicate that more N and carbohydrate are expended in producing BF than in producing BL. The amount of litter from reproductive organs produced in the mast year was similar to the amount of leaf litter at 900 and 1500 m, but three times as much at 550 m. Leaf numbers per shoot were significantly lower at all elevations in the mast year than in the non-mast years (and the amount of leaf litter at 550 and 1500 m tended to be lower in the mast year than in the non-mast years. In conclusion, preferential allocation of resources to seeds in the mast year reduced the availability of resources for flower primordium formation, and this may have accounted for the poor seed production in the following non-mast year.
In arid regions throughout the world, shallow phreatic aquifers feed natural oases of much higher productivity than would be expected solely from local rainfall. In South America, the presence of well-developed Prosopis flexuosa woodlands in the Monte Desert region east of the Andes has puzzled scientists for decades. Today these woodlands provide crucial subsistence to local populations, including descendants of the indigenous Huarpes. We explore the vulnerability and importance of phreatic groundwater for the productivity of the region, comparing the contributions of local rainfall to that of remote mountain recharge that is increasingly being diverted for irrigated agriculture before it reaches the desert. We combined deep soil coring, plant measurements, direct water-table observations, and stable-isotopic analyses (2H and 18O) of meteoric, surface, and ground waters at three study sites across the region, comparing woodland stands, bare dunes, and surrounding shrublands. The isotopic composition of phreatic groundwaters (delta2H: -137 per thousand +/- 5 per thousand) closely matched the signature of water brought to the region by the Mendoza River (-137 per thousand +/- 6 per thousand), suggestin that mountain-river infiltration rather than in situ rainfall deep drainage (-39 per thousand +/- 19 per thousand) was the dominant mechanism of recharge. Similarly, chloride mass balances determined from deep soil profiles (> 6 m) suggested very low recharge rates. Vegetation in woodland ecosystems, where significant groundwater discharge losses, likely >100 mm/yr occurred, relied on regionally derived groundwater located from 6.5 to 9.5 m underground. At these locations, daily water-table fluctuations of 10 mm, and stable-isotopic measurements of plant water, indicated groundwater uptake rates of 200-300 mm/yr. Regional scaling suggests that groundwater evapotranspiration reaches 18-42 mm/yr across the landscape, accounting for 7 17% of the Mendoza River flow regionally. Our study highlights the reliance of ecosystem productivity in natural oases on Andean snowmelt, which is increasingly being diverted to one of the largest irrigated regions of the continent. Understanding the ecohydrological coupling of mountain and desert ecosystems here and elsewhere should help managers balance production agriculture and conservation of unique woodland ecosystems and the rural communities that rely on them.
Prosopis glandulosa var. torreyana accounts for nearly 90% of the total plant cover in a mesquite woodland community near Harper's Well along the southern margin of the Salton Sea in the Sonoran Desert of California. Total above-ground biomass in ten individuals studied in detail ranged from 43–760 kg per plant and 1.9–8.5 kg m⁻² canopy area. Stand biomass ranged locally from a high of 23,000 kg ha⁻¹ near the wash to 3,500 kg ha⁻¹ in the fringe of this mesquite stand. Net above-ground primary production for 1980 had a mean of 2.2 kg m⁻² canopy for shrub forms and 5.3 kg m⁻² canopy for tree forms. Mean Prosopis stand production for 1980 was 3,650 kg ha⁻¹, an extremely high value for desert communities. This level of production is particularly high in relation to the low mean annual precipitation of approximately 70 mm. New woody tissues in trunk and branches accounted for 51.5% of the allocation of productivity in Prosopis, a remarkably high woody allocation for a desert plant. Only 33.6% of net primary production was allocated to leaves.
The amount of new growth and the number of inflorescences per branch exhibited high variability. The respective differences among the trees could explain 80 and 40% of the total variability. Fruiting also showed a marked variability, with a high shedding of fruit during ripening. Branches orientated N-E showed a higher number of inflorescences and fruit than those orientated S-W. -from Authors
Field bruchids attacking fruit of the leguminous trees Prosopis cineraria, Prosopis juliflora, Acacia tortilis, Acacia senegal and Albizia lebbek in different regions of the Thar desert are reported. No damaged seed from any species germinated.
Describes a community of Prosopis chilensis, P. flexuosa and P. pugionata growing in the Reserva Provincial "Los Pocitos', Dpto. de Pocho, Prov. de Cordoba. Pollinators included Caupolicana mendocina, Xylocopa splendidula and Apis mellifera. -from English summary
Taking a functional rather than an ecosystem or a utilitarian approach, Thomas and Packham provide a concise account of the structure of woodlands and forests. Using examples from around the world - from polar treelines to savannahs to tropical rain forests - the authors explain the structure of the soil and the hidden world of the roots; how the main groups of organisms which live within them interact both positively and negatively. There is particular emphasis on woodland and forest processes, especially those involving the flow and cycling of nutrients, as well as the dynamics of wooded areas, considering how and why they have changed through geological time and continue to do so. This clear, non-technical, text will be of interest to undergraduates, foresters, ecologists and land managers.
A description of the wood structure of Prosopis flexuosa DC. (Legum.) is given. It is semiring-porous, shows pores solitary, in multiples and in clusters; small to large-sized vessels with simple perforation plates,
and thick vessel walls. Rays multiseriate and homogeneous. Paratracheal axial parenchyma and libriform fibres. The hydraulic tissue seems well adapted to very low rainfall and prolonged dry periods. Seasonal variations in cambial activity have been investigated from July 1982 to June 1984. Prosopis flexuosa has an annual rhythm of wood production which coincides with the climatic rhythm. Cambial activity is initiated in the last week of October, reaches a peak in November/December and ceases in April. The initiation time in the activity of vascular cambium seems to be endogenous. A dormant period was noted when defoliation takes place during the dry months. Relationships between xylem production, phenology and climatic factors are discussed. Although the growth rings are not always clearly demarcated, one growth ring is generally formed each year.
Mesquite or Vilayati babul (Prosopis juliflora) is a drought resistant, evergreen, spiny tree with drooping branches and a deep laterally spreading root system. It grows in semi-arid and arid tracts of tropical and sub-tropical regions of the world and is spreading because the leaves are unpalatable and animals do not digest its seed. The mesquite has become a major nuisance; cutting or pruning its branches to form a canopy would provide shade for travelers, aid harvesting of pods, as well as make available wood for fuel. An average plant starts fruiting by 3-4 years of age and yields annually 10-50 kg pods/ tree, which can be collected from May-June and September-October. Availability of pods worldwide is estimated to be about 2-4 million metric tonnes. Ripe pods are highly palatable; on dry matter basis they contain 12% crude protein, 15% free sugar, a moderate level of digestible crude protein (7% DCP) with a high level of energy (75% TDN). The pods contain low tannin levels below those toxic to animals. Seeds contain 31-37% protein; pods should be finely ground before feeding to facilitate utilization of the seeds. Mesquite pods could replace costlier feed ingredients such as grain and bran contributing 10-50% of the diet. Phosphorus supplements need to be added when mesquite pod, exceeds 20% of animals’ diet.
Export Date: 2 July 2013, Source: Scopus, Article in Press
It is argued that a conflict between data and models is inherent in many mortality functions. Equations are utilised which have the property that however short a chosen growth period, then some loss of stems/ha must occur. But permanent sample plot records frequently contains data which exhibit no mortality over several years. If these data are discarded then mortality must be overpredicted. If they are retained, difficulties can occur in residual plot analyses and fitting of models, through the creation of bimodal residual distributions and failure to produce average residual values near zero. To resolve this, a two-step modelling strategy is suggested. A logistic regression predicting the probability of stems/ha death is first constructed. A mortality equation is then built, but only utilising data where death has occurred over a period. Estimates from this second model are then reduced by a factor, equivalent to the probability of death occurring, acquired from the logistic equation. An example involving Pinus radiata data in New Zealand is given. It is argued that better behaved prediction emerges through adoption of the system and clearer information on stand death dynamics is obtained. The system can be utilised stochastically, if desired.
On occasion, generalized linear models for counts based on Poisson or overdispersed count distributions may encounter lack of fit due to disproportionately large frequencies of zeros. Three alternative types of regression models that utilize all the information and explicitly account for excess zeros are examined and given general formulations. A simple mechanism for added zeros is assumed that directly motivates one type of model, here called the added-zero type, particular forms of which have been proposed independently by D. LAMBERT (1992) and in unpublished work by the author. An original regression formulation (the zero-altered model) is presented as a reduced form of the two-part model for count data, which is also discussed. It is suggested that two-part models be used to aid in development of an added-zero model when the latter is thought to be appropriate.
Prosopis L. pods have been proposed as a source of gum (galactomannans), with potential applications as a thickening agent in the food industry. The objective of this work was to compare, under field conditions, the production and mortality of reproductive structures in two sympatric shrub species of Prosopis: P. alpataco Phillipi and P. denudans Bentham. Our results indicate that fruit production in Prosopis denudans and P. alpataco is very low and erratic in non-irrigated lands. Although large quantities of flowers (15,000–25,000 flowers*0.40 m−2) can be found in one flowering season, 70–80% are shed before they reach anthesis and 20–28% are aborted between anthesis and fruit set. We conclude that the utilization of native populations of Prosopis denudans and P. alpataco for fruit production in Patagonian steppe, could not guarantee a consistent supply for the food industry.
Data from a 10 year series of cone production taken from 755 trees were used to model individual cone production in stone pine (Pinus pinea L.) stands in the Northern Inland Plateau of Spain following three different approaches. The first step was the construction of a silvicultural model, including typical forest growth covariates as tree size, stand density, site index and distance independent competition indices. Remaining between-plot variability was related with ecological attributes, as winter rainfall and altitude, resulting in a hybrid model. The third approach attempted to develop an ecological-type based model by considering a previous stratification of stone pine forests based on altitude, soil, geology and climate characteristics. The best model in terms of likelihood, bias and accuracy on predictions was the ecological-type one, producing unbiased marginal estimates for the main part of the territory with an efficiency reaching up to 39%.Due to the hierarchical structure of data set, proposed model was formulated as a multilevel mixed model. Stochastic formulation allows simulating cone production under different changing scenarios and describing real distribution of cone production within a given stand. Developed model constitutes the cone yield module for PINEA2, an integrated single tree model for the management of stone pine stands within the northern Plateau of Spain.
Mediterranean forests are characterised by a remarkable set of features that make them naturally and aesthetically attractive, on the one hand, but also quite fragile, on the other, therefore calling for careful strategies for their conservation and management. An exceptionally large variation of environmental conditions characterises the Mediterranean countries, where the environment can limit forest growth and succession but can also give rise, more often than it is supposed, to lush, mesic forest ecosystems, similar to those of central Europe. Moreover, Mediterranean forests contain an ample, plant and animal biological diversity, exemplified by the large number of tree species as compared to Nordic forests, and by their relatively high genetic variability due to the survival of many conifer and broadleaf species in southern European refuges, during the glacial periods. Another peculiar aspect of this region is the long-lasting manipulation of trees, forests and landscapes, since ancient times, with the diffusion all over the Mediterranean basin of such species as Pinus pinea, Cupressus sempervirens, Castanea sativa, and Quercus suber. The harsh and unpredictable climate, the difficult socio-economic conditions and the history of over-exploitation of the Mediterranean forests require that a scientifically sound conservation strategy and a locally-tailored sustainable management should be implemented. In particular, the need for identifying those silvicultural and management strategies appropriate for southern European forests should be stressed. Obviously, this consideration will have important effects on the definition of criteria for sustainability and eco-certification. Also, social issues should be considered key factors for effective forest conservation in the Mediterranean region, otherwise it will be impossible to control forest fires and landscape degradation.
We consider several statistical models for the analysis of the abundance of a rare species and these are illustrated in detail with data for the abundance of Leadbeater's Possum in montane ash forests of south-eastern Australia. These data are characterised by a discrete distribution with the zero class inflated. In many statistical problems the parameters of this distribution depend on covariates, such as the number of hollow bearing trees. We advocate a conditional model which is simple to interpret and readily fitted. We show how to obtain standard errors for the parameter estimates. We also show how to estimate the mean abundance of animals at a site. The methods outlined in this paper offer a powerful framework for the study of problems having a discrete response (like abundance) with the zero class inflated.
Temporally variable production of seed crops by perennial plants (masting) has been hypothesized to be a valuable mechanism in the reduction of seed predation by satiating and starving seed consumers. To achieve these benefits, coexisting species subjected to the same predator would benefit from a similar pattern of seeding fluctuation over time that could lead to a reduction in predation at the within-species level. We tested for the existence of an environmental factor enforcing synchrony in acorn production in two sympatric Mediterranean oaks (Quercus ilex and Q. humilis) and the consequences on within-species and between-species acorn predation, by monitoring 15 mixed forests (450 trees) over seven years. Acorn production in Q. ilex and Q. humilis was highly variable among years, with high population variability (CVp) values. The two species exhibited a very different pattern across years in their initial acorn crop size (sum of aborted, depredated, and sound acorns). Nevertheless, interannual differences in summer water stress modified the likelihood of abortion during acorn ripening and enforced within- and, particularly, between-species synchrony and population variability in acorn production. The increase in CVp from initial to mature acorn crop (after summer) accounted for 33% in Q. ilex, 59% in Q. humilis, and 60% in the two species together. Mean yearly acorn pre-dispersal predation by invertebrates was considerably higher in Q. humilis than in Q. ilex. Satiation and starvation of predators was recorded for the two oaks, and this effect was increased by the year-to-year variability in the size of the acorn crop of the two species combined. Moreover, at a longer time scale (over seven years), we observed a significant reduction in the mean proportion of acorns depredated for each oak and the variability in both species' acorn production combined. Therefore, our results demonstrate that similar patterns of seeding fluctuation over time in coexisting species mediated by an environmental cue (summer drought) may contribute to the reduction of the impact of seed predation at a within-species level. Future research should be aimed at addressing whether this process could be a factor assisting in the coexistence of Q. ilex and Q. humilis.
Effect of woody plant encroachment on livestock production in North and South America
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Las Leguminosas Argentinas Silvestres Y Cultivadas An empirical ecological-type model for predicting Stone pine (Pinus pinea L.) cone production in the Northern Plateau (Spain)
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