Daniel Villarroel

On the delineation of tropical vegetation types with an emphasis on forest/savanna transitions

Background: There is no generally agreed classification scheme for the many different vegetation formation types occurring in the tropics. This hinders cross-continental comparisons and causes confusion as words such as ‘forest’ and ‘savanna’ have different meanings to different people. Tropical vegetation formations are therefore usually imprecisely and/or ambiguously defined in modelling, remote sensing and ecological studies. Aims: To integrate observed variations in tropical vegetation structure and floristic composition into a single classification scheme. Methods: Using structural and floristic measurements made on three continents, discrete tropical vegetation groupings were defined on the basis of overstorey and understorey structure and species compositions by using clustering techniques. Results: Twelve structural groupings were identified based on height and canopy cover of the dominant upper stratum and the extent of lower-strata woody shrub cover and grass cover. Structural classifications did not, however, always agree with those based on floristic composition, especially for plots located in the forest–savanna transition zone. This duality is incorporated into a new tropical vegetation classification scheme. Conclusions: Both floristics and stand structure are important criteria for the meaningful delineation of tropical vegetation formations, especially in the forest/savanna transition zone. A new tropical vegetation classification scheme incorporating this information has been developed.

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.

One New and One Long-lost Species of Eugenia (Myrtaceae) from the Bolivian Cerrado

Abstract. Two species of Eugenia L. (Myrtaceae) within Eugenia sect. Umbellatae O. Berg, E. teresa-ruiziana Villarroel & Faria and E. cydoniifolia O. Berg, are described and illustrated. The former is a new species, whereas the latter has not been collected since 1842. Both species are endemic to the cerrados of the Lomerío region of eastern Bolivia. This article examines and discusses the vegetative and reproductive characteristics that distinguish these species, which include the leaf morphology, indumentum type, secondary vein number, stamen number, and ovule number per locule. Resumen. Dos especies de Eugenia L. (Myrtaceae) dentro de la Eugenia sect. Umbellatae O. Berg, E. teresa-ruiziana Villarroel & Faria y E. cydoniifolia O. Berg, se describen e ilustran. La primera es una nueva especie, mientras que la segunda no se había colectado desde 1842. Ambas especies son endémicas de los cerrados de la región de Lomerío del este de Bolivia. En este artículo se examinan y discuten las características vegetativas y reproductivas que diferencian estas especies, siendo estas: la morfología foliar, tipo de indumento, número de venas secundarias, número de estambres, y el número de óvulos por lóculo.