Spatial and temporal variation of biomass in a tropical forest: results from a large census plot in Panama

Abstract

Summary 1We estimated the dry, living, above-ground biomass (AGB) standing stock and its turnover in a 50-hectare forest plot located in moist tropical forest on Barro Colorado Island, Panama. The estimates were obtained using inventory data collected every 5 years from 1985 to 2000, including measurements of all trees ≥ 1 cm diameter. 2 Four different allometric regressions relating trunk diameter and height with AGB were compared. Based on the most consistent method, we estimated that the Barro Colorado forest holds 281 ± 20 Mg ha − 1 (1 Mg = 10 3 kg) of AGB, lianas included. A third of the AGB is stored in trees larger than 70 cm in diameter. 3 Stand-level AGB increment (growth plus recruitment) was highest in the period 1985-90 (7.05 ± 0.32 Mg ha − 1 year − 1 , mean ± 95% confidence limits based on samples of multiple hectares) and smallest in the period 1990-95 (5.25 ± 0.26 Mg ha − 1 year − 1 ), while AGB losses were similar during the three intervals (mean 5.43 ± 0.72 Mg ha − 1 year − 1 ). This resulted in significant differences in AGB change (defined as increment minus loss) among census intervals; including branchfalls, the AGB of Barro Colorado Island increased in 1985-90 (+0.82 ± 0.84 Mg ha − 1 year − 1 ), decreased in 1990-95 ( − 0.69 ± 0.82 Mg ha − 1 year − 1 ), and increased again in 1995 -2000 (+0.45 ± 0.70 Mg ha − 1 year − 1 ). The 15-year average was +0.20 Mg ha − 1 year − 1 , but with a confidence interval that spanned zero ( − 0.68 to 0.63 Mg ha − 1 year − 1 ). 4 Branchfalls and partial breakage of stems had a significant influence on the AGB changes. They contributed an average of 0.46 Mg ha − 1 year − 1 to the AGB loss. About 5% of AGB increment was due to trees less than 10 cm in diameter. 5 To test whether the AGB of tropical forests is increasing due to climate change, we propose that in each forest type, at least 10 hectares of forest be inventoried, and that measurements of the small classes (< 10 cm diameter) as well as large size classes be included. Biomass loss due to crown damage should also be estimated.

Detecting and projecting changes in forest biomass from plot data

“…censuses may be explained by stochastic temporal environmental variation. This is consistent with the similarity in the biomass distribution across all six censuses evaluated here (Figure 14.4A), and with the lack of consistent directional change observed in the past 25 years (Chave et al 2003(Chave et al , 2004. However, it is important to note that this approach has clear limitations, related to the limitations of the underlying data.…”

“…The data cleaning steps that are taken typically seem reasonable, but multiple alternative procedures meet the 'reasonable' test. Where authors have, to their credit, examined multiple alternatives, they often find that these produce different results (Chave et al 2003;Lewis et al 2009a). Such sensitivity analyses are laudable, but do not shed light on which alternative is best.…”

“…Past approaches to error identification most typically involved absolute cutoffs for diameter growth rates, with more extreme values considered unrealistic and thus necessarily erroneous. For example, diameter increases of more than 35 mm yr −1 , 40 mm yr −1 or 45 mm yr −1 , or decreases of more than 5 mm yr −1 , have been flagged for correction (Chave et al 2003(Chave et al , 2008Lewis et al 2009b;Phillips et al 2009). Where multiple census data are available, these presumed errors are corrected by interpolation or extrapolation where possible.…”

Architecture of Iberian canopy tree species in relation to wood density, shade tolerance and climate

“…Alternatively, no clear asymptote is found because mature undisturbed pine forests are rare in the Mediterranean. Although it is generally assumed that height-diameter relationships should be asymptotic, studies from different forests show that a quarter of the species evaluated do not show such an asymptotic relationship (Thomas 1996;Chave et al 2003;Poorter et al 2006; but also see Aiba and Nakashizuka 2009). Species that do show an asymptote are canopy species from closed forest types, or species from more open woodland.…”

Biomasa aérea almacenada en Ficus soatensis y Tecoma stans en la localidad de Puente Aranda, Bogotá, Colombia

“…Para valorar la predicción que cada modelo hace de los resultados de los otros modelos empleados para la estimación de la biomasa, se utilizó el coeficiente de correlación de Spearman (R), tomando como referencia el estudio de Chavé et al (2003), de tal modo que se logre seleccionar el modelo que presenta la mayor correlación media con los otros modelos que se están comparando. El coeficiente de correlación de Spearman es una medida de asociación entre dos variables aleatorias continuas.…”