• crbe website

• chave webpage

• Citation
• Database
• Climatic water deficit
• Stress variable E
• Raster tools

This webpage contains supplementary information to the following article: Chave J, Rejou-Mechain M, Burquez A, Chidumayo E, Colgan MS, Delitti WBC, Duque A, Eid T, Fearnside PM, Goodman RC, Henry M, Martinez-Yrizar A, Mugasha WA, Muller-Landau HC, Mencuccini M, Nelson BW, Ngomanda A, Nogueira EM, Ortiz-Malavassi E, Pelissier R, Ploton P, Ryan CM, Saldarriaga JG, Vieilledent G. Improved allometric models to estimate the above ground biomass of tropical trees. 2014. Global Change Biology. DOI: 10.1111/gcb.12629

 

We have compiled tree harvest data for 58 sites around the tropics. Included trees had a diameter at breast height > 5 cm. Every felled tree had at least: (i) a trunk diameter measurement, in cm; (ii) a total tree height measurement, in m; (iii) an aboveground biomass measurement (oven-dry biomass, in kg); and (iv) an estimate of wood specific gravity. The file below (in csv format) contains five columns: the four tree-level variables reported in the database, plus an acronym describing the study site, and described in detail in Table S1 of Chave et al. 2014

 

The long-term climatic water deficit (CWD) is the water lost by the environment during dry months (defined as months where evapotranspiration exceeds rainfall). It is measured in mm/yr as the difference between rainfall and evapotranspiration during dry months only and is, by definition, negative. Sites such that CWD=0 are not seasonally water-stressed; in contrast, sites with very negative CWD values are strongly seasonally water-stressed. Several recent studies have emphasized the importance of CWD as a predictor of ecosystem response to climatic change. Here, we provide a global climate layer for the long-term average of CWD at 2.5 arc-minute resolution.

 

Environmental stress factor on the diameter-height tree allometry. During the analysis of a pantropical tree harvest compilation (Chave et al. 2014), we found that an environmental variable defined by E=1.e-3 x (0.178xTS-0.938xCWD-6.61xPS) is an important covariable of the diameter-height relationship of trees. In this equation, TS is temperature seasonality as defined in the Worldclim dataset (bioclimatic variable 4). CWD is the climatic water deficit (in mm/yr, measured as above). PS is the precipitation seasonality as defined in the Worldclim dataset (bioclimatic variable 15). The raster file for variable E is available below 2.5 arc-minute resolution.

 

Raster tools. For beginners in spatial grid data and/or R (for more information on the R project, see http://www.r-project.org/), you may obtain values for CWD or E at one or several geolocations by copying and pasting the following two lines in the R environment:

 

To check that the routine above works properly, please run the lines below in R (or RStudio):

 

The first value for CWD should return -117.7933. The second value (for E) should return -0.1287045. The coordinates in this test are those of the Nouragues Ecological Research Station.

 

Last update May 10th, 2014