Defaunation changes leaf trait composition of recruit communities in tropical forests in French Guiana.

Hunting impacts tropical vertebrate populations, causing declines of species that function as seed dispersers and predators, or that browse seedlings and saplings. Whether and how the resulting reductions in seed dispersal, seed predation, and browsing translate to changes in the tree composition is poorly understood. Here, we assess the effect of defaunation on the functional composition of communities of tree recruits in tropical rainforests in French Guiana. We selected eight sites along a gradient of defaunation, caused by differences in hunting pressure, in otherwise intact old-growth forests in French Guiana. We measured shifts in functional composition by comparing leaf and fruit traits and wood density between tree recruits (up to 5 cm diameter at breast height) and adults, and tested whether and how these compositional shifts related to defaunation. We found a positive relationship with defaunation for shifts in specific leaf area, a negative relationship for shifts of leaf toughness and wood density, and a weak relationship for shifts in fruit traits. Our results suggest that the loss of vertebrates affects ecological processes such as seed dispersal and browsing, of which browsing remains understudied. Even though these changes sometimes seem minor, together they result in major shifts in forest composition. These changes have long-term ramifications that may alter forest dynamics for generations.

Tree mode of death and mortality risk factors across Amazon forests.

The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing > 3800 species from 189 long-term RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted-modes of death with different ecological consequences. Species-level growth rate is the single most important predictor of tree death in Amazonia, with faster-growing species being at higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limits. These results provide not only a holistic pan-Amazonian picture of tree death but large-scale evidence for the overarching importance of the growth-survival trade-off in driving tropical tree mortality.

Influence of livelihood assets, experienced shocks and perceived risks on smallholder coffee farming practices in Peru.

Smallholder farmers might adopt different farming practices to cope with multiple stressors depending on their livelihood assets, and with varying environmental and economic outcomes. Ongoing global change is triggering stronger and different stressors that threaten conventional farming practices; however, this could be resolved if livelihood assets that drive decision making are actionable and thus can be modified. This study assessed the influence of farmers' livelihood assets, risk perception, and shocks on the choice of non-conventional farming practices for smallholder coffee farmers in San Martín, Peru. Using household survey data, we collected data on 162 coffee plantations along an elevation gradient. We operationalized the sustainable livelihoods framework for the adoption of shade and input coffee farming strategies and explored farmers' motives to change them. Despite associated high risks with pest and disease pressure, coffee price volatility and climate change, these risks did not explain the current shade and input farming strategies. While in the past five years, farmers adapted shade and input management in response to pest and disease and climate change pressures, these occurred in diverging directions: we found higher human and social assets associated with higher shade levels, and a trend for higher physical and financial assets associated with higher input use. These findings illustrate that two main factors affect decisions on farming practices related to shade and input management and they relate to different livelihood capitals. This suggests a potential for conflicting decision-making, push-and-pulling decisions in different directions. Further the disconnect between livelihood assets and perceptions suggests that perception of risk and shocks might not be sufficient to motivate decision making under changing conditions. Such insights in decision-making typologies and drivers can inform the development of farming practices that enhance resilience and sustainability of smallholder coffee production in Peru and elsewhere in the tropics.

Compositional response of Amazon forests to climate change.

Most of the planet's diversity is concentrated in the tropics, which includes many regions undergoing rapid climate change. Yet, while climate-induced biodiversity changes are widely documented elsewhere, few studies have addressed this issue for lowland tropical ecosystems. Here we investigate whether the floristic and functional composition of intact lowland Amazonian forests have been changing by evaluating records from 106 long-term inventory plots spanning 30 years. We analyse three traits that have been hypothesized to respond to different environmental drivers (increase in moisture stress and atmospheric CO2 concentrations): maximum tree size, biogeographic water-deficit affiliation and wood density. Tree communities have become increasingly dominated by large-statured taxa, but to date there has been no detectable change in mean wood density or water deficit affiliation at the community level, despite most forest plots having experienced an intensification of the dry season. However, among newly recruited trees, dry-affiliated genera have become more abundant, while the mortality of wet-affiliated genera has increased in those plots where the dry season has intensified most. Thus, a slow shift to a more dry-affiliated Amazonia is underway, with changes in compositional dynamics (recruits and mortality) consistent with climate-change drivers, but yet to significantly impact whole-community composition. The Amazon observational record suggests that the increase in atmospheric CO2 is driving a shift within tree communities to large-statured species and that climate changes to date will impact forest composition, but long generation times of tropical trees mean that biodiversity change is lagging behind climate change.

Evolutionary heritage influences Amazon tree ecology.

Lineages tend to retain ecological characteristics of their ancestors through time. However, for some traits, selection during evolutionary history may have also played a role in determining trait values. To address the relative importance of these processes requires large-scale quantification of traits and evolutionary relationships among species. The Amazonian tree flora comprises a high diversity of angiosperm lineages and species with widely differing life-history characteristics, providing an excellent system to investigate the combined influences of evolutionary heritage and selection in determining trait variation. We used trait data related to the major axes of life-history variation among tropical trees (e.g. growth and mortality rates) from 577 inventory plots in closed-canopy forest, mapped onto a phylogenetic hypothesis spanning more than 300 genera including all major angiosperm clades to test for evolutionary constraints on traits. We found significant phylogenetic signal (PS) for all traits, consistent with evolutionarily related genera having more similar characteristics than expected by chance. Although there is also evidence for repeated evolution of pioneer and shade tolerant life-history strategies within independent lineages, the existence of significant PS allows clearer predictions of the links between evolutionary diversity, ecosystem function and the response of tropical forests to global change.

Variation in stem mortality rates determines patterns of above-ground biomass in Amazonian forests: implications for dynamic global vegetation models.

Understanding the processes that determine above-ground biomass (AGB) in Amazonian forests is important for predicting the sensitivity of these ecosystems to environmental change and for designing and evaluating dynamic global vegetation models (DGVMs). AGB is determined by inputs from woody productivity [woody net primary productivity (NPP)] and the rate at which carbon is lost through tree mortality. Here, we test whether two direct metrics of tree mortality (the absolute rate of woody biomass loss and the rate of stem mortality) and/or woody NPP, control variation in AGB among 167 plots in intact forest across Amazonia. We then compare these relationships and the observed variation in AGB and woody NPP with the predictions of four DGVMs. The observations show that stem mortality rates, rather than absolute rates of woody biomass loss, are the most important predictor of AGB, which is consistent with the importance of stand size structure for determining spatial variation in AGB. The relationship between stem mortality rates and AGB varies among different regions of Amazonia, indicating that variation in wood density and height/diameter relationships also influences AGB. In contrast to previous findings, we find that woody NPP is not correlated with stem mortality rates and is weakly positively correlated with AGB. Across the four models, basin-wide average AGB is similar to the mean of the observations. However, the models consistently overestimate woody NPP and poorly represent the spatial patterns of both AGB and woody NPP estimated using plot data. In marked contrast to the observations, DGVMs typically show strong positive relationships between woody NPP and AGB. Resolving these differences will require incorporating forest size structure, mechanistic models of stem mortality and variation in functional composition in DGVMs.

Evaluación y ecología de fauna silvestre en áreas de producción

En Bolivia son pocos los profesionales capacitados para realizar investigación sobre fauna silvestre. Para paliar este problema, es importante capacitar a los estudiantes, egresados y profesionales de las carreras relacionadas con fauna, como agronomía, ingeniería forestal y biología. La capacitación debe realizarse a corto plazo y largo plazo, con temas como ecología, conservación y monitoreo de fauna silvestre. Dentro de este ámbito, el primer curso se realizó en Riberalta, Beni (2000) y el segundo en Valle Del Sacta, Cochabamba (2000). El objetivo de los cursos fue el de capacitar a los estudiantes sobre planteamiento de la pregunata, elaboración de hipótesis de predicción, recolección y análisis de los datos, interpretación e inferencia de los resultados, y realización y edición de los trabajos. Entre los métodos desarrollados para la evaluación de fauna silvestre se usaron monitoreo de vertebrados terrestres en base a registro de huellas (en parcelas), observaciones directas (encuentros) y trampas (murciélagos, roedores, aves). Entre los temas desarrollados de incluyeron evaluaciones de fauna en los planes de manejo forestal, fundamentos de dendrología, fenología, tratamientos silviculturales, inventarios y censos forestales ( y su aplicación al manejo de bosque), herbivoría, y remoción de semillas por vertebrados e insectos