Soil water-holding capacity and monodominance in Southern Amazon tropical forests

Background and aims: We explored the hypothesis that low soil water-holding capacity is the main factor driving the monodominance of Brosimum rubescens in a monodominant forest in Southern Amazonia. Tropical monodominant forests are rare ecosystems with low diversity and high dominance of a single tree species. The causes of this atypical condition are still poorly understood. Some studies have shown a relationship between monodominance and waterlogging or soil attributes, while others have concluded that edaphic factors have little or no explanatory value, but none has accounted for soil-moisture variation other than waterlogging. This study is the first to explicitly explore how low soil water-holding capacity influences the monodominance of tropical forests. Methods: We conducted in situ measurements of vertical soil moisture using electrical resistance collected over 1 year at 0–5; 35–40 and 75–80 cm depths in a B. rubescens monodominant forest and in an adjacent mixed-species forest in the Amazon-Cerrado transition zone, Brazil. Minimum leaf water potential (Ψmin) of the seven most common species, including B. rubescens, and soil water-holding capacity for both forests were determined. Results: The vertical soil moisture decay pattern was similar in both forests for all depths. However, the slightly higher water availability in the monodominant forest and Ψmin similarity between B. rubescens and nearby mixed forest species indicate that low water-availability does not cause the monodominance. Conclusions: We reject the hypothesis that monodominance of B. rubescens is primarily determined by low soil water-holding capacity, reinforcing the idea that monodominance in tropical forests is not determined by a single factor

Tree diversity and above-ground biomass in the South America Cerrado biome and their conservation implications

Less than half of the original two million square kilometers of the Cerrado vegetation remains standing, and there are still many uncertainties as to how to conserve and prioritize remaining areas effectively. A key limitation is the continuing lack of geographically-extensive evaluation of ecosystem-level properties across the biome. Here we sought to address this gap by comparing the woody vegetation of the typical cerrado of the Cerrado–Amazonia Transition with that of the core area of the Cerrado in terms of both tree diversity and vegetation biomass. We used 21 one-hectare plots in the transition and 18 in the core to compare key structural parameters (tree height, basal area, and above-ground biomass), and diversity metrics between the regions. We also evaluated the effects of temperature and precipitation on biomass, as well as explored the species diversity versus biomass relationship. We found, for the first time, both that the typical cerrado at the transition holds substantially more biomass than at the core, and that higher temperature and greater precipitation can explain this difference. By contrast, plot-level alpha diversity was almost identical in the two regions. Finally, contrary to some theoretical expectations, we found no positive relationship between species diversity and biomass for the Cerrado woody vegetation. This has implications for the development of effective conservation measures, given that areas with high biomass and importance for the compensation of greenhouse gas emissions are often not those with the greatest diversity

Forest restoration with Araucaria angustifolia (Bertol.) Kuntze on Campos do Jordao state park, SP: fire effects on tree and shrub structure

Restoration actions aimed at Mixed Ombrophilous Forests are limited due to the scarce knowledge about composition and structure of these communities on different successional stages, and also the effects of frequent disturbances on its dynamics, such as fire. The present work aimed at evaluating the effect of an accidental fire on the horizontal, vertical and diametric structure of an Araucaria angustifolia planted forest, located on Campos do Jordao State Park, SP, nine years after the disturbance. This study also intends to appraise the potential of these forests on inducing the secondary succession. Two Araucaria angustifolia forests were selected, with similar ages and environmental conditions, called Forests RI and Rh. On RI, there's no account of fire since its planting, in 1959 (control). RII, which was planted in 1958, was affected by an accidental fire in July 2001. During the upper strata survey (circumference at breast height (CBH) >= 15cm), 17 and 8 permanent plots of 10x20m were established on forests RI and RII, respectively. In each one of these plots five sub-plots of 1x1m were randomly chosen, in order to survey the lower strata (total height >= 30cm and CBH < 15cm). In forest RI, 836 trees and shrubs were surveyed, while on forest Rh I 175 individuals were sampled. Forest RI presented significantly higher values than II for density on both strata and dominance on upper strata (absolute totals). The diametric structure follows an inverted J-pattern in both areas. Nevertheless, the fire seems to significantly have reduced the number of individuals of the first diameter classes. Forest RII seems to still express the effect of burning, which was more severe in the lower strata; in case the above hypothesis is correct. However, due to favorable landscape conditions, we hope that both forests continue their natural succession, resembling the surrounding forest matrix in the long term.409427929

Structure of the understory community in four stretches of Araucaria forest in the state of Sao Paulo, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)We analyzed the structure of the understory community in the Atlantic Forest sensu lato, for which phytosociological descriptions of the understory are lacking. We delineated 50 plots of 10 x 20 m each at four sites within an Araucaria forest (a subtype of Atlantic Forest), located in the municipalities of Bananal, Campos do Jordao, Itabera and Barra do Chapeu, all of which are in the state of Sao Paulo, Brazil. To sample the resident species of the understory, we randomly selected five 1 x 1 m subplots within each plot, resulting in a total sampling area of 250 m(2) at each site. We identified differences among the locations, mostly due to proportional differences in growth forms, in terms of species richness and the importance values within the community Factors potentially influencing the understory structure include macrodimatic and microclimatic conditions, as well as forest fragmentation, the abundance of deciduous trees in the canopy, the surrounding vegetation and geographic location.28186101Program Pesquisas em Caracterizacao, Conservacao e Uso Sustentavel da Biodiversidade (Biota, Research into the Characterization, Conservation, Restoration, and Sustainable Use of Biodiversity)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2006/03288-1, 2001/05146-6]CNPq [479084/2007-6