Silvopastoral Use Research Articles

Evaluation of different felling intensities in management of secondary carob forests under silvopastoral use in the Humid Chaco

The progressive reduction of the forest surface to enable land destined for other productive activities and its subsequent abandonment, allowed the appearance of fragments of secondary forests, frequently dominated by carob trees. Prosopis alba that have been identified as a strategic biological resource of the Chaco Park, due to its characteristic of multipurpose tree, which gives it a high value for the management of secondary forests in areas abandoned by agriculture and livestock, offering at the same time an alternative productive. A fundamental aspect in the management of secondary forests of this species is the need to concentrate growth on the dominant trees, since the achievement of large-sized individuals is essential for supplying the wood industry. Within the framework of a project aimed at designing management tools that make it possible to make high forest production compatible with livestock. To this effect, preliminary results of the response of the forest mass as well as of the remaining individuals are presented against three intensities of selective thinning. The objective of the work is to have basic information that allows establishing sustainable management guidelines in secondary forests, in its initial stages for the provision of quality wood for forestry-industry with forestry-livestock production schemes.

Differential response of natural regeneration to silvopastoral use intensity in mixed forests of northern Patagonia, Argentina

Silvopastoral use (combined livestock and forestry) is widely distributed in South America's native forests. Without medium to long-term planning, this activity may affect the population dynamics of the dominant canopy tree species, resulting in forest degradation. The early stages of tree life cycles are usually the most vulnerable, so the successful establishment and development of seedlings and saplings is a key indicator of the potential for continuity of the tree layer over time. This study evaluated the effect of silvopastoral use intensity (SUI) upon the density and development of dominant tree species - Austrocedrus chilensis and Nothofagus dombeyi - along a gradient generated by spatially and temporally heterogeneous livestock activity and forest harvesting in mixed forests of northwestern Patagonia, Argentina. We monitored the survival and growth of 740 seedlings and saplings over two years (2018–2020) in three medium-sized estates SUI gradients and upland migration of livestock during the summer season. We also evaluated changes in biophysical variables that influence the tree regeneration process: light input, soil moisture, and understory vegetation structure. We found that higher SUI modifies the biophysical environment, increasing light input and horizontal understory cover. The response of saplings and seedlings to SUI was not homogenous; N. dombeyi showed significant changes in its regeneration dynamics, denoted by a decrease in the density of seedlings and an increase in the density and height growth of the saplings along the SUI gradient. Meanwhile, A. chilensis only showed tendencies to deformation by browsing (height: diameter ratio). Thus, in medium-size estates with low stocking rates and which are free of herbivory during summers; fast-growing species (e.g. N. dombeyi) could be favored by the slight canopy openings, compensating for the negative impact of browsing. However, it is necessary to monitor and potentially individually protect A. chilensis saplings until browsing height is exceeded.

Forest active restoration for silvopastoral use in Northwestern Patagonia: relative importance of the nurse effect

Forest active restoration for silvopastoral use in Northwestern Patagonia: relative importance of the nurse effect

Resilient Andisols under silvopastoral systems

Livestock can affect physical and chemical soil properties, depending on both stocking rates, and intrinsic soil properties. This study aimed to analyze changes in physicochemical properties in volcanic soils under silvopastoral systems. Two contrasting study sites were selected in Patagonia, Argentina, where Nothofagus antarctica silvopastoral systems develop on volcanic soils with different moisture regimes: Udands and Xerands. In each site, four treatments were considered according to canopy openness and accessibility for livestock: closed forests (control), open forests, 5-year exclosures in open forests, and finally, degraded areas affected by large-scale disturbances (i.e., grazing + clear cutting + fire). Localized stocking rate was estimated, and soil properties were analyzed at two depths (0–10 and 10–20 cm). Results showed that physicochemical properties were slightly modified by silvopastoral use, with no critical values found, except for penetration resistance. Soil types behaved differently: while Udands were more fertile and resilient, Xerands were more susceptible to livestock impact, and localized stocking rate was a good short-scale soil degradation indicator for these soils. Although grazing negatively affected soil fertility, increments in carbon stock, nitrogen, and phosphorus were found in Xerands. Besides, an evident improvement in physical soil properties in the short term (5 years) was found in Udands when livestock was excluded. Despite the high resilience of udic volcanic soils under silvopastoral use, total organic matter and organic matter associated with macroaggregates severely decreased. Such decrease occurred especially when grazing was overlapped with other impacts, leading to the loss of forest cover, regardless the soil moisture regime. Nothofagus antarctica forests on volcanic soils seem to form a system capable of sustaining silvopastoral use with controlled stocking rate, but they are highly vulnerable to major impacts.

Plant-plant co-occurrences under a complex land-use gradient in a temperate forest.

Land-use generates multiple stress factors, and we need to understand their effects on plant-plant interactions to predict the consequences of land-use intensification. The stress-gradient hypothesis predicts that the relative strength of positive and negative interactions changes inversely under increasing environmental stress. However, the outcome of interactions also depends on stress factor's complexity, the scale of analysis, and the role of functional traits in structuring the community. We evaluated plant-plant co-occurrences in a temperate forest, aiming to identify changes in pairwise and network metrics under increasing silvopastoral use intensity. Proportionally, positive co-occurrences were more frequent under high than low use, while negative co-occurrences were more frequent under low than high. Networks of negative co-occurrences showed higher centralization under low use, while networks of positive co-occurrences showed lower modularity and higher centralization under high use. We found a partial relationship between co-occurrences and key functional traits expected to mediate facilitation and competition processes. Our results shows that the stress-gradient hypothesis predicts changes in spatial co-occurrences even when two stress factors interact in a complex way. Networks of negative co-occurrences showed a hierarchical effect of dominant species under low use intensity. But positive co-occurrence network structure partially presented the characteristics expected if the facilitation was an important mechanism characterizing the community under high disturbance intensity. The partial relationship between functional traits and co-occurrences may indicate that other factors besides biotic interactions may be structuring the observed negative spatial associations in temperate Patagonian forests.

Conservation values of understory vascular plants in even- and uneven-aged Nothofagus antarctica forests

Usually, stands with aging trees are considered forests with higher conservation values, regardless their structural diversity and other functional attributes. Natural stands present a wide range of age structures, from even-aged stands growing at different development growth phases (e.g. CO = stands at initial or final optimum development growth phase, MD = stands at mature or decaying development growth phases) to uneven-aged stands with mixed development growth phases (e.g. UOG = stands combining mature or decaying development growth phases with initial or final optimum development growth phases, UMD = stands combining only mature and decaying development growth phases). The aim of this work was to compare richness and cover of understory vascular plants of even- and uneven-aged stands of Nothofagus antarctica (nire) forests in Tierra del Fuego (Argentina), and relate these characteristics with abiotic, soil and forest structure variables. A total of 75 stands were sampled across the natural range distribution of the forests, where understory (point intercept method), forest structure (angle count sampling and eye-fish photos) and environmental (soil) variables were measured. 17 one-way ANOVAs were conducted using Tukey test at p UOG > MD > CO (17–28 total, and 13–24 native species, respectively). Neither exotic species richness (4–5 species) nor understory cover significantly changed among treatments (total, dicots, ferns and bryophytes). However, monocots cover significantly differed among treatments (F = 3.9, p = 0.012), where UMD > MD > UOG > CO. Finally, indicator species cover for environmental degradation did not present significant differences (F = 2.1, p = 0.106), but they were positive related to forests growing in mature stages. We concluded that uneven-aged stands presented significantly higher conservation values compared to even-aged stands, where mature/decay stands have better conservation values than optimum growth development phases. These findings can be used for better silviculture practices that combine silvopastoral use and conservation strategies.

Simulated deforestation versus satellite data in Roraima, Northern Amazonia, Brazil

Cenários de mudança de uso e cobertura da terra na Amazônia são necessários para subsidiar decisões que podem evitar a emissão de milhões de toneladas de CO2 para a atmosfera. Portanto, é importante avaliar modelos que visam a geração de cenários futuros. O atual estudo avaliou cenários gerados para o período 2011-2017 em Roraima, norte da Amazônia. Comparou-se o desmatamento simulado com os dados de satélite do PRODES. O mapeamento compreendeu (i) uma Área de Uso Silvo-pastoril – AUS (excluindo terras indígenas, unidades de conservação e não-floresta) intersectada com (ii) uma grade de nove (9) células de 10.000 km2 (100 × 100 km) para avaliações. O cenário de 2013 apresentou a maior similaridade (55,2%) com o mapa correspondente do PRODES. Apesar das divergências entre o desmatamento simulado nos cenários e o desmatamento oficial, no geral, as avaliações demonstraram a validade do modelo e a sua habilidade para gerar cenários que representam, de forma realística, o desmatamento ocorrido em Roraima no período analisado.

High Methane Uptake from Soils of Low and High Density Radiata Pine Afforestations Compared to Herbaceous Systems

ABSTRACT During a one-year period, methane (CH4) fluxes from soil were studied in a southern temperate region system using a static chamber technique. Four treatments on neighboring areas with similar environmental characteristics but different vegetation cover were considered: a natural grassland (NG), an agricultural land (AL), a low tree density radiata pine afforestation (P1 – suitable for silvopastoral use), and a dense radiata pine afforestation (P2). CH4 uptake increased in the following order: AL < NG < P1 and P2 (statistically significant differences), without differences between P1 and P2. CH4 fluxes were mainly influenced by soil water content (R = 0.78; p = .0001) and bulk density (R = 0.75; p = .0004) indicating that CH4 uptake by soils is primarily connected to methane soil diffusivity. The statistical differences of these parameters could partially justify CH4 flux differences found among treatments. However, a multiple linear regression analysis indicated that other factors such as soil temperature also control CH4 fluxes (R2 = 0.86, p≪4x10−6), and could explain temporal patterns. Results suggest that the low tree density afforestations, suitable for silvopastoral use, have a functional role (CH4 uptake) similar to that of dense forests, and could be a good option to mitigate CH4 emissions by livestock and agricultural sector.

Decomposition and nutrient release of grass and tree fine roots along an environmental gradient in southern Patagonia

AbstractDecomposition of fine roots is a fundamental ecosystem process that relates to carbon (C) and nutrient cycling in terrestrial ecosystems. However, this important ecosystem process has been hardly studied in Patagonian ecosystems. The aim of this work was to study root decomposition and nutrient release from fine roots of grasses and trees (Nothofagus antarctica) across a range of Patagonian ecosystems that included steppe, primary forest and silvopastoral forests. After 2.2 years of decomposition in the field all roots retained 70–90% of their original mass, and decomposition rates were 0.09 and 0.15 year−1 for grass roots in steppe and primary forest, respectively. For N. antarctica roots, no significant differences were found in rates of decay between primary and silvopastoral forests (k = 0.07 year−1). Possibly low temperatures of these southern sites restricted decomposition by microorganisms. Nutrient release differed between sites and root types. Across all ecosystem categories, nitrogen (N) retention in decomposing biomass followed the order: tree roots &gt; roots of forest grasses &gt; roots of steppe grasses. Phosphorus (P) was retained in grass roots in forest plots but was released during decomposition of tree and steppe grass roots. Calcium (Ca) dynamics also was different between root types, since trees showed retention during the initial phase, whereas grass roots showed a slow and consistent Ca release during decomposition. Potassium (K) was the only nutrient that was rapidly released from both grass and tree roots in both grasslands and woodlands. We found that silvopastoral use of N. antarctica forests does not affect grass or tree root decomposition and/or nutrient release, since no significant differences were found for any nutrient according to ecosystem type. Information about tree and grass root decomposition found in this work could be useful to understand C and nutrient cycling in these southern ecosystems, which are characterized by extreme climatic conditions.

Land‐use intensity indirectly affects ecosystem services mainly through plant functional identity in a temperate forest

Abstract Land‐use change is known to affect biodiversity, and there is increasing concern regarding how these changes may impact the provision of ecosystem services. Although functional composition (diversity and identity) could influence ecosystem properties and services at the community level, there is little quantitative understanding of these relationships in the field. Here, we evaluate the direct and indirect effects (through ecosystem properties) of biodiversity on the provision of multiple ecosystem services in native mixed forest in north‐west Patagonia, and how land‐use intensity influences these relationships. We used structural equation modelling to test hypotheses regarding the relationship between understorey plant functional composition, two ecosystem properties, four ecosystem services and silvopastoral use intensity (SUI). We also evaluated two alternative models to assess the mechanism behind biodiversity and ecosystem properties relationships (biomass ratio and niche complementarity). Finally, we performed pairwise correlations to identify synergies and trade‐offs between ecosystem services. SUI affected functional composition, and the provision of three out of four ecosystem services was indirectly affected by land‐use intensity through changes in ecosystem properties. We found that this indirect effect of biodiversity on ecosystem services happens mainly through changes in functional identity rather than functional diversity. Under increasing land‐use intensity, functional composition changed towards a community characterized by a resource acquisition strategy. Trade‐offs between ecosystem services (provisioning vs. regulating) were enhanced under high SUI, while synergies where enhanced under low SUI (provisioning vs. cultural). Thus, although the strength of these relationships varied between SUI, its nature (trade‐off or synergy) stayed the same. Our results expand on previous studies by simultaneously considering the effect of land‐use intensification directly on functional composition and on the ecosystem processes underpinning ecosystem services, as well as on the relationship among them. We provide evidence of an indirect effect of land‐use intensification on multiple ecosystem services through biodiversity. Moreover, we found that functional identity is more important than diversity for ecosystem functionality. Land‐use intensification affects biodiversity, and thus, ecosystem properties, but does not change the relationship among ecosystem services. A plain language summary is available for this article.

Modelo de estados y transiciones de los ñirantales del NO de la Patagonia como herramienta para el uso silvopastoril sustentable

Desarrollamos un modelo de estados y transiciones (MEyT) para el bosque de nire ( Nothofagus antarctica ) en el norte de la Patagonia, con el fin de sintetizar el conocimiento disperso sobre las repuestas de este sistema al manejo silvopastoril. En base a una recopilacion bibliografica, a un taller de expertos seguido por sesiones de consulta y a relevamientos de campo propusimos los estados alternativos e identificamos los disturbios naturales y las practicas de manejo mas comunes que disparan cambios entre estados. Definimos siete estados, 13 transiciones de degradacion y cuatro de restauracion. Los bosques mas integros estan dominados por nire y cana ( Chusquea culeou ) y el estado mas degradado lo componen estepas sub-arbustivas de cadillo ( Acaena splendens ). Los estados intermedios serian los mas aptos para el uso silvopastoril (bosque abierto de nire con cana y pastizal, y bosque de nire con pastizal), pero tienen una alta inestabilidad con las practicas de manejo actuales, ya que, a causa de dicho manejo, con el paso del tiempo perderian el componente arboreo y la cobertura de cana. El pastoreo, la extraccion forestal, los incendios y las especies invasoras son los principales factores que disparan las transiciones de degradacion. Estos efectos estan agravados por la competencia del componente herbaceo con la vegetacion arborea, la mortandad de arboles y de cana, y por la erosion del suelo. La reversion de las transiciones de degradacion no se produce de forma natural en el horizonte productivo del predio (~40 anos) y requiere del uso de tecnologias como plantacion, proteccion de los plantines de arboles y desarbustado. La identificacion de las fases de riesgo en cada estado permite contar con alertas tempranas de deterioro, visualizar los efectos del manejo y orientar las practicas para mantener la composicion y estructura del bosque dentro de los limites que contemplan los aspectos productivo y ambiental. https://doi.org/10.25260/EA.17.27.2.0.240

Cambios en la diversidad funcional del sotobosque y la tasa de descomposición frente a diferentes intensidades de uso silvopastoril en el noroeste de la Patagonia, Argentina

Functional diversity loss by human land-use changes is of great importance for achieving sustainable management, as it plays a key role in ecosystem functioning through a direct influence over ecological processes. In northwest Patagonian forests, livestock production is among the main activities affecting natural ecosystems. The aim of the study was to characterize changes in functional diversity of understory vegetation in sites with different silvopastoral use intensity, and the effects that these variations may have on rate of litter decomposition in mixed forests of cypress and coihue of southwest Rio Negro Province, Argentina. Changes in plant functional traits (life cycle, life style, architecture, habitat, leaf size, leaf texture and root system) were characterized, and the decomposition rate of each site's litter was quantified. Our results showed that both functional diversity index (FD Q ) and decomposition rate were higher under high silvopastoral use intensity, but the relationship was not significant. Results also showed that certain plant functional traits (i.e., rosette architecture, prostrate habitat and fern life form) have a significant effect on litter lost weight. Under high silvopastoral use intensity, the relative proportion of species with rosette architecture and prostrate habitat increases, which led to an increase in decomposition rate. This indicates that silvopastoral activity may modify the original community composition towards species with a rapid resource acquisition, altering also nutrient cycling. In this sense, ecosystem functioning seems to be influenced by certain functional traits, rather than functional diversity itself.

Linking potential biodiversity and three ecosystem services in silvopastoral managed forest landscapes of Tierra del Fuego, Argentina

ABSTRACTSeveral studies confirm that biodiversity loss endangers ecosystem services (ES) supply and human well-being. A better understanding of biodiversity–ES relationships and effects of biodiversity loss on ES supply is needed. The objective was to determine relationships between potential biodiversity and three ES in Patagonia where cattle ranching under silvopastoral use occurs. We used grids of potential biodiversity (plant species richness) and three ES, provisioning (cattle stocking rate), regulating (CO2 sequestration) and cultural (geo-tagged digital-images). Potential biodiversity was negatively related to provisioning, but no significant relations were detected with regulating and cultural. These relations showed regional differences related to forest landscape distribution. High values of regulating were found in southern areas being coincident with high potential biodiversity. Opposite trends (negative relationship with biodiversity) was observed for provisioning in eastern and western regions where provisioning decrease from N-S. Results suggest that provisioning do not overlap spatially with the higher values of potential biodiversity maps, which is an advantage for land use planning when conservation and management requirements must be combined. Our results are the first contribution for Patagonia to underpin scientific and institutional efforts to connect biodiversity conservation with ES maintenance. However, further studies must be addressed including more ES and regions.EDITED BY Sandra Luque

Biodiversity and ecological long-term plots in Southern Patagonia to support sustainable land management: The case of PEBANPA network

Historically, interactions and trends between biodiversity, ecosystem function (EF) and land use practices in southern Patagonia (Argentina) have been largely undocumented and poorly understood. Since 2002, 1214 permanent and semi-permanent plots within the PEBANPA Network have enabled researchers to monitor and assess functions and trends among vegetation parameters, biodiversity, forest dynamics, soil physicochemical characteristics, and land use management. The objectives of this manuscript are to communicate the role and rationale of the PEBANPA Network, summarize examples of the main results found within the network and provide guidance to decision makers with respect to advancing sustainable land management in southern Patagonia. As examples, rangeland health indices, seedling and sapling regeneration under different timber managed forests, litterfall and seeds production under silvopastoral use, and soil carbon content impacted by livestock grazing have all been assessed. Vegetation and environmental variables including soil respiration, soil water infiltration, soil water retention capacity, soil erosion, and litter cover were measured under different grazing intensities. Livestock and forestry production have caused changes in the original floristic patterns, with several areas experiencing desertification. Heavy stocking rates have caused the greatest impacts on grassland soil carbon (C) loss as a consequence of soil erosion. We were able to conclude that low − medium grazing intensities yield the most positive impacts for biodiversity and soil physicochemical characteristics. Studies regarding levels of seedling and sapling regeneration post-harvest of timber further supported the importance of long-term monitoring due to the strongest evidence of interactions occurring 20 to 30 years after harvest. Distribution patterns of vascular plants and epigaeic coleopterons diversity revealed statistically significant differences among geographical zones and dominant vegetation types. The PEBANPA Network helps southern Patagonia address the challenges of unsustainable land management and climate change through monitoring ecosystem function and services. Long-term monitoring of biodiversity and ecosystem function help decision makers better understand the impacts of land use practices, develop well-informed policies and secure present and future human well-being.

Ten years of seed production and establishment of regeneration measurements in Nothofagus antarctica forests under different crown cover and quality sites, in Southern Patagonia

This study evaluated the seed production and quality and the subsequent regeneration establishment in five pure Nothofagus antarctica forests growing at different site qualities and crown cover during 10 years, in Southern Patagonia (Argentina). Four traps of 1 m2 were installed in each stand and sampled monthly (between February and May) each year. The incorporation and survival of seedlings were evaluated using four permanent plots of 1 m2 in each stand. The site quality of the studied forests did not influence seed production and regeneration. The amount of seed production and seed quality were proved to have a decisive influence on the N. antarctica seedling establishment in the subsequent years. At the same time, our results suggest that independently of the site class, the canopy openness for silvopastoral use improved the conditions for seedling establishment. However, the success of seedling survival over time would be conditioned for the influence of other factors such as understory competition.

A review of silvopastoral systems in native forests of Nothofagus antarctica in southern Patagonia, Argentina

Silvopastoral systems in Nothofagus antarctica (nire) forest have become an economical, ecological and productive alternative in Patagonia. Southern Patagonia’s experience over the past 12 years with silvopastoral systems is reviewed. The productivity and nutritive value (crude protein content and dry matter digestibility) of the understorey grassland were dependent on the interaction of environmental (mainly soil water availability and light intensity) and management factors under the trees and in turn determined animal performance. A method developed for carrying capacity estimation at the paddock level was based on the potential aboveground net primary production, and values ranged from 85 to 2200 kg DM ha−1 year−1. Planned thinning in secondary forest stands provides wood production and also improves the undestorey DM production by increasing incoming radiation. Within a management plan, a stand’s water stress conditions as well as the use of Reineke’s stand density index are proposed to assist in determining thinning intensities. Livestock production is the main annual income of silvopastoral systems where cattle and mixed livestock production (cattle + sheep) is the main activity. Animal performance at the whole farm scale is presented by comparing traditional extensive grazing management with an adaptive silvopastoral management that included strategic separation in homogeneous areas (grass steppe, forest and riparian meadows), stocking rate adjustment to grassland net primary production and the protection of regeneration from herbivores browsing. Data from litter decomposition, nutrient cycling and carbon storage studies also are presented. Finally, aspects related to the criteria and indicators to assess nire forest’s sustainability under silvopastoral use along with biodiversity conservation issues are presented.

Mistletoes and epiphytic lichens contribute to litter input in Nothofagus antarctica forests

Litter input is one of the key components that define nutrient cycling in forests and the majority of studies only consider the tree components of litterfall. However, epiphytic species can play a crucial role in litter input throughout the growing season. This work evaluates changes in litter production by mistletoe (Misodendrum sp.) and epiphytic lichen (Usnea sp.), related to crown cover in mature unmanaged, second-growth and managed (thinned for silvopastoral use) forests in Tierra del Fuego (Argentina). We used plastic traps to collect litterfall biomass from trees, lichens and mistletoes on a monthly basis over three consecutive years. Tree litter was considerable during autumn (March to May), which is typical of Nothofagus deciduous species in the Southern hemisphere. In contrast, peak litterfall from mistletoes and lichens occurred during spring and summer seasons. Tree litter (1954–3398 kg dry matter ha−1 year−1) was correlated with crown cover gradient being highest in second-growth forests and lowest in thinned sites. While litter input from mistletoes did not vary among forest types (307–333 kg dry matter ha−1 year−1), lichen litter (11–40 kg dry matter ha−1 year−1) was higher in unmanaged and thinned mature forests despite differences in tree crown cover. Contrary to what we expected, the management practices investigated here did not affect the biomass of canopy communities compared to unmanaged mature forests. Mistletoes and lichens significantly increased the spatial (forest type) and temporal complexity (extended period of falling) of litterfall in Nothofagus antarctica forests. This study provides a starting point to understand the ecological relevance of canopy communities in the Patagonian forests of southern Argentina.

Litterfall and nutrients return in Nothofagus antarctica forests growing in a site quality gradient with different management uses in Southern Patagonia

We evaluated the annual litterfall and nutrients return in primary forests of Nothofagus antarctica growing at three different site classes (SC) (III, IV and V) and compared two of these forests with adjacent stands under silvopastoral use (thinned 40 years ago), in Patagonia, Argentina. Traps were installed in each stand and sampled monthly during the litterfall over 10 years. Sample from the five stands was ground for further analyses of nutrients (N, P, K, Ca, Mg and S). The litterfall varied significantly between SC, but not between years, from 1,306 to 1,972 kg ha−1 in the best site. The nutrients return from litterfall did not change neither between site classes and years in most nutrients. Comparing primary forests with silvopastoral stands, in SCIV, significant differences among uses occurred for litterfall production and nutrients return, being higher in primary forest. While, in SCV, the litterfall and nutrients return practically did not change among uses. The results showed the incidence of site quality and forest use on the litterfall and nutrients return in N. antarctica forests.

Response of Axonopus catarinensis and Arachis pintoi to shade conditions

In the northeast of Argentina, there are more than 100,000 ha of silvopastoral systems, where trees, forages and livestock are combined with the goal to diversify income, reduce financial risk, obtain more profit and enhance environmental benefit (Cubbage et al. 2012). The rapid adoption of these production systems by farmers has generated high demand for information on shade-tolerant forage grass and legume species. Axonopus catarinensis is a native grass from Itajai Valley (Brazil), that was introduced to the northeast of Argentina 10 years ago, and Arachis pintoi is a subtropical legume (also native to Brazil) adapted to acid soils and tolerant of medium levels of shade (Fisher and Cruz 1994). Visual observation of these species in the field indicated high yields and acceptable tolerance to shade. A trial was subsequently carried out with the aim to quantify dry matter yield and nutritive quality of the species under different levels of shade for silvopastoral use.

Pressão de preconsolidação como ferramenta de análise da sustentabilidade estrutural de classes de solos com diferentes usos

O principal problema ambiental causado pelo uso do solo em áreas de preservação permanente longitudinais aos rios é a supressão da mata ciliar. O tipo e a intensidade desse uso alteram a estrutura do solo e comprometem as funções físicas dessas áreas, principalmente próximo aos cursos d'água. O objetivo deste trabalho foi avaliar a sustentabilidade estrutural, a partir do ensaio de compressão uniaxial, de três classes de solo (Cambissolo Háplico, Argissolo Amarelo e Gleissolo Háplico) e o impacto de diferentes tipos de usos do solo - não permitido pela legislação ambiental - de áreas de preservação permanente na sub-bacia do rio Ribeira de Iguape, SP. Foram delimitadas na área experimental três classes de solo: Cambissolo, Argissolo e Gleissolo. Numa primeira etapa, compararam-se as três classes de solos sob mata nativa e sob pastagem. Na segunda, avaliou-se a influência de diferentes tipos de uso do solo - cultivo de banana, pastagem degradada, uso silvipastoril e mata nativa - sobre a estrutura de um Cambissolo. A pressão de preconsolidação mostrou-se ferramenta capaz de identificar a degradação nos solos. O uso do solo nas áreas de preservação permanente altera a pressão de preconsolidação do solo, causando sua degradação estrutural, colocando em risco a sustentabilidade das terras, e não deve ser permitido. O Gleissolo mostrou maiores valores de pressão de preconsolidação em função de teores crescentes de água e, portanto, maior capacidade de suporte de carga em relação ao Cambissolo e Argissolo. O cultivo de banana foi o tipo de uso que mais degradou os solos das áreas de preservação permanente.