PS 10-111 - Using a trait-based approach to study the relationships between turnover and wood productivity in two contrasting forests of Venezuela, northern South America

Monday, August 7, 2017
Exhibit Hall, Oregon Convention Center


Emilio J. Vilanova, Universidad de Los Andes; Robert Swan, University of Washington; Gregory J. Ettl, University of Washington


Functional traits can provide insights into a variety of ecological questions within a wide range of scales: from individuals, species, and potentially to communities and landscapes. The main goal of this work is to compare two contrasting forest types in Venezuela, South America, using a trait-based approach to: 1) characterize the functional composition of forests with an emphasis on tree populations; and 2) describe the relationship between the community weighted mean (CWM) of trait values and two ecosystem processes such as wood productivity and aboveground biomass. A group of 15 traits, at different scales (whole-plant, leaf and stem) were measured in the field and/or obtained from selected literature from two areas: Mountain-cloud forests in the Andes (San Eusebio) and Lowland Western plain forests (Caparo). 12 permanent sample plots of 0.25 ha (6 per site) serves as the study area. Between 1 to 5 individuals from a total of 52 tree dominant species (Caparo = 25; San Eusebio = 27) were sampled. To evaluate which predictors among each CWM trait values is the most important for turnover (Tr), wood productivity (WP) and aboveground biomass (AGB), a series of ordinary least squares multiple regression analysis are performed. A general hypothesis being tested is that compared to Andean high elevation forests, Western plain forests are dominated by plant functional types characterized by or acquisitive traits determining a higher productivity and turnover rates.


Both sites had similar values in AGWP (4.56 ± 1.86 Mg C ha-1 year-1 in San Eusebio vs 4.32 ± 1.76 for Caparo), but a faster dynamic was found in the lowland forests of Caparo with an average Tr of 2.73 ± 1.11 % year-1 compared to 1.72 ± 0.70 inSan Eusebio. Contrary to expectations, on average, a higher nitrogen content in soil was found in San Eusebio plots. However, this was not the case for leaf nitrogen where lowland forests had 18% more nitrogen than forests of San Eusebio. The presence of Fabaceae species in Caparo and no record of this family in San Eusebio may be a potential explanation for this. Thicker leaves with a higher chlorophyll content were found at the higher elevation plots. Mean wood density was higher in San Eusebio (0.63 ± 0.25 g cm-3) and overall well correlated with mortality rates (R2 = 0.20) but not with WP. Further tests need to be performed to accurately determine the influence of all traits in forest dynamics.