Bianca de Oliveira

Effects of soil and space on the woody species composition and vegetation structure of three Cerrado phytophysiognomies in the Cerrado-Amazon transition

The Cerrado Biome is considered one of the worlds biodiversity hotspots because of its rich biodiversity, the high level of endemism and the increasing threat. The Cerrado is composed by a mosaic of different vegetation types, including physiognomies that vary from grasslands (campo limpo) to savannas (typical cerrado or cerrado sensu stricto) and cerrado woodlands (cerradão). However, the factors that determine the composition of the Cerrados flora and the structure of the physiognomies that compose this biome are still poorly understood. Here, we investigate the influence of the chemical and granulometric properties of the soil and the effect of geographic distance on the occurrence and abundance of woody species in three Cerrado phytophysiognomies - cerrado woodland (cerradão), dense cerrado savanna and typical cerrado savanna - in the Cerrado-Amazon transition. We tested the hypothesis that the edaphic characteristics and geographic space determine the species composition and the structure of the woody vegetation of these three phytophysiognomies. We demonstrate that the dissimilarities in the structure and composition of the three sites were determined more by space (13% of explanation) than edaphic properties (1%), but primarily by the interaction between these two factors (26%). We conclude that, in situations where the chemical and granulometric properties of the soil are relatively homogeneous, as we found in the present study, geographic distance between sites has a greater influence than variation in the substrates properties on modelling the occurrence and abundance of the woody plant species in the Cerrado.

DESENVOLVIMENTO INICIAL E QUALIDADE DE MUDAS DE Copaifera langsdorffii Desf. SOB DIFERENTES NÍVEIS DE SOMBREAMENTO

As florestas de galeria vem sendo fragmentadas, levando a perda de sua elevada diversidade, tornando-se imprescindiveis estudos que avaliem o comportamento ecologico de suas especies arboreas. O presente estudo teve como objetivo testar a hipotese de que a producao de mudas de Copaifera langsdorffii e influenciada pela luminosidade do ambiente, apresentando maior qualidade e desenvolvimento inicial em niveis intermediarios de luz. As plantas foram testadas em pleno sol, 30%, 50%, 70% e 90% de sombreamento, avaliando-se numero de folhas, altura e diâmetro aos 60, 90, 120 e 191 dias apos a emergencia (DAE) e massa seca aerea e radicular e, indice de qualidade de Dickson ao final do experimento (191 DAE). O efeito dos niveis de sombreamento foi analisado por meio de analise de regressao. As plantas apresentaram boa plasticidade de crescimento nos diferentes niveis de luminosidade, mas com melhor desenvolvimento e qualidade (IQD) em 50% de sombreamento, corroborando a hipotese testada. A luminosidade ou sombreamento excessivo devem ser evitados para garantir a producao de mudas mais vigorosas de Copaifera langsdorffii. Assim, recomenda-se a producao de mudas desta especie sob 50% de sombreamento para favorecer a sua qualidade e possivelmente garantir melhor sobrevivencia em campo.

Climate and fragmentation affect forest structure at the southern border of Amazonia

ABSTRACT Background: The remaining forests in the extensive contact zone between southern Amazonia (seasonal rain forest) and the Cerrado (savanna) biomes are at risk due to intense land-use and climate change. Aims: To explore the vulnerability of these transitional forests to changes in land use and climate, we evaluated the effects of fragmentation and climatic variables on forest structure. Methods: We measured the diameter and height of 14,185 trees with diameter ≥10 cm at 24 forest plots distributed over an area of 25,000 km2. For each plot, we obtained data on contemporary fragmentation and climatic variables. Results: Forest structure variables (height, diameter, height:diameter allometry, biomass) varied significantly both within and among plots. The height, H:D and biomass of trees were positively correlated with annual precipitation and fragment area. Conclusions: The association between forest structure and precipitation indicates that these forests plots are likely to be vulnerable to dry season intensification anticipated for the southern edge of the Amazon. Additionally, the reduction in the fragment area may contribute to reductions in forest biomass and tree height, and consequently ecosystem carbon stocks. Given the likely susceptibility of these forests, urgent conservation action is needed to prevent further habitat degradation.

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.