Pedro Manuel Villa

La agroforestería como estrategia para la recuperación y conservación de reservas de carbono en bosques de la Amazonía

Durante los ultimos anos los continuos cambios en el uso de la tierra en la Amazonia, principalmente a traves de la conversion de bosques por practicas agropecuarias y de extraccion, han generado graves transformaciones en la estructura y funcionamiento de los ecosistemas con impactos a escala regional y global. La deforestacion para establecer sistemas agricolas itinerantes es uno de los principales factores que contribuyen con las emisiones de carbono a la atmosfera como uno de los servicios de mayor repercusion ambiental. Sin embargo, existen reconocidos mecanismos de reduccion de emisiones de carbono por deforestacion y degradacion (REDD+), i) bien sea controlando la reduccion de emisiones de las fuentes a traves de la conservacion y manejo sustentable de los bosques, y ii) recuperando e incrementando la biomasa vegetal como importantes sumideros a traves de estrategias de rehabilitacion y restauracion forestal. Con la finalidad de incrementar la eficiencia en la recuperacion y conservacion de carbono en areas vulnerables de deforestacion y degradacion forestal en la Amazonia, se propone como objetivo desarrollar un analisis de los impactos ambientales potenciales de la Agroforesteria como alternativa REDD+, a traves de i) la rehabilitacion de areas degradadas sometidas a ciclos sucesivos de fuego y cultivos, ii) la restauracion pasiva de bosques secundarios, e iii) implementacion de barbechos mejorados con el manejo de especies agroforestales. La agroforesteria representa una importante alternativa para recuperar y conservar reservas de carbono a traves de las principales actividades REDD+ frente a la presion generada por la agricultura itinerante en la Amazonia.

Plant diversity and community structure of Brazilian Páramos

In Eastern South America, high altitude grasslands represent a mountain system that has a high number of endemic species. However, studies on the ecology of plant communities in these environments remain scarce. We aimed to evaluate the patterns of biodiversity and structure of plant communities from rocky outcrops in high altitude grasslands of three areas at the Caparaó National Park, southeastern Brazil, by sampling 300 randomly distributed plots. Then, we compared the floristic composition, relative abundance, and biological and vegetation spectra among areas. We classified species as endemic and non-endemic and verified the occurrence of endangered species. Species richness was evaluated by rarefaction analysis on the sampling units. The importance value and species abundance distribution (SAD) models were assessed. We also performed an indicator species analysis. We sampled 58 species belonging to 49 genera and 32 families. The number of species decreased with increasing altitude, with significant differences being observed among areas regarding richness, abundance, and cover. Of the total number of species, 10 are endemic to the Caparaó National Park and 17 are listed on the Brazilian Red List of endangered species. The dominant families on all peaks were Asteraceae and Poaceae. The SAD models showed lognormal and geometric distributions, corroborating the fact that 10 species that were common to all three areas were also the most dominant ones in the communities and showed the highest importance values, which ranged between 35% and 60%. Indicator species analysis revealed that 28 species (48.27%) were indicators. Of these, 42.85% had maximum specificity, meaning that they occurred only in one area. Thus, the number of species per life form ratio was similar among areas, yet vegetation spectra differed, especially for hemicryptophytes. The altimetric difference among the areas showed to be a very important driver in the community assembly, influencing the evaluated variables, however, other drivers as soil depth, slope and water could also influence the community structure on a smaller and local spatial scale.

Phylogenetic structure is determined by patch size in rock outcrop vegetation on an inselberg in the northern Amazon region

Although inselbergs from around the world are iconic ecosystems, little is known on the underlying mechanisms of community assembly, especially in their characteristic patchy outcrop vegetation. Environmental constraints are expected to cause phylogenetic clustering when ecological niches are conserved within evolutionary lineages. We tested whether vegetation patches from rock outcrops of the Piedra La Tortuga Natural Monument, in the northern Amazon region, are phylogenetically clustered, indicating that environmental filtering is the dominant driver of community assemblage therein. We classified all patches according to their size as very small (< 1 m2), small (1-4 m2), medium-sized (4-8 m2), and large patches (8-15 m2). From each class, we randomly selected 10 patches, totalizing 40 patches covering 226 m2. All individuals found in the 40 isolated patches were identified to the species level. We also correlated measurements of phylogenetic community structure with patch size. We found that species from patches are restricted to the clades monocots, fabids, malvids, and lamiids. We conclude that vegetation in this rock outcrop is phylogenetically clustered. Furthermore, we found that phylogenetic turnover between pairs of patches increases with patch size, which is consistent with a scenario of higher environmental stress in smaller patches. Further research is necessary to identify nurse species in inselberg vegetation, which is pivotal for conservation and restoration of this particular ecosystem.