Journal Article

Predicting alpha diversity of African rain forests: models based on climate and satellite-derived data do not perform better than a purely spatial model

Bakayoko, Adama, Harrigan, Ryan J., Dauby, Gilles, Saatchi, Sassan, Gautier, Laurent, Kenfack, David, Senterre, Bruno, Thomas, Duncan, Nusbaumer, Louis, Parren, Marc P. E., Fauset, Sophie, Malhi, Yadvinder, Hawthorne, William D., Lewis, Simon L., Swaine, Mike D., Gillet, Jean-François, Sosef, Marc S. M., Tchouto, Mbatchou G. P., Sonké, Bonaventure, Affum-Baffoe, Kofi, Kouka, Lazare A., Buermann, Wolfgang, Doucet, Jean-Louis, Sunderland, Terry C. H., Sheil, Douglas, Van Valkenburg, Johan L. C. H., Bongers, Frans, Chatelain, Cyrille, Leal, Miguel E., Peh, Kelvin S.-H., Reitsma, Jan M., Comiskey, James A., Parmentier, Ingrid, Kouassi, Edouard K., Kouamé, François N., Hardy, Olivier J., Mitchard, Edward T. A., Chuyong, George B.

2011

Overview

Aim: Our aim was to evaluate the extent to which we can predict and map tree alpha diversity across broad spatial scales either by using climate and remote sensing data or by exploiting spatial autocorrelation patterns. Location: Tropical rain forest, West Africa and Atlantic Central Africa. Methods: Alpha diversity estimates were compiled for trees with diameter at breast height ≥ 10 cm in 573 inventory plots. Linear regression (ordinary least squares, OLS) and random forest (RF) statistical techniques were used to project alpha diversity estimates at unsampled locations using climate data and remote sensing data [Moderate Resolution Imaging Spectroradiometer (MODIS), normalized difference vegetation index (NDVI), Quick Scatterometer (QSCAT), tree cover, elevation]. The prediction reliabilities of OLS and RF models were evaluated using a novel approach and compared to that of a kriging model based on geographic location alone. Results: The predictive power of the kriging model was comparable to that of OLS and RF models based on climatic and remote sensing data. The three models provided congruent predictions of alpha diversity in well-sampled areas but not in poorly inventoried locations. The reliability of the predictions of all three models declined markedly with distance from points with inventory data, becoming very low at distances > 50 km. According to inventory data, Atlantic Central African forests display a higher mean alpha diversity than do West African forests. Main conclusions: The lower tree alpha diversity in West Africa than in Atlantic Central Africa may reflect a richer regional species pool in the latter. Our results emphasize and illustrate the need to test model predictions in a spatially explicit manner. Good OLS or RF model predictions from inventory data at short distance largely result from the strong spatial autocorrelation displayed by both the alpha diversity and the predictive variables rather than necessarily from causal relationships. Our results suggest that alpha diversity is driven by history rather than by the contemporary environment. Given the low predictive power of models, we call for a major effort to broaden the geographical extent and intensity of forest assessments to expand our knowledge of African rain forest diversity.

• Publisher: Blackwell Publishing Ltd,Blackwell Publishing,Blackwell
• Subject: African rain forests / Agriculture & agronomie / Agriculture & agronomy / amazon / Animal and plant ecology / Animal, plant and microbial ecology / autocorrelation / Biodiversity / Biological and medical sciences / Biologie végétale (sciences végétales, sylviculture, mycologie...) / Central Africa / Climate / Datasets / dynamics / Forest ecology / Forestry / Fundamental and applied biological sciences. Psychology / General aspects / General forest ecology / Generalities. Production, biomass. Quality of wood and forest products. General forest ecology / geographical ecology / How space and environment combine to control diversity / image analysis / inventories / Kriging / least squares / Life sciences / linear models / Marine / Modeling / Modelling / moderate resolution imaging spectroradiometer / Ordinary least squares / patterns / Phytobiology (plant sciences, forestry, mycology...) / plant diversity / prediction / Rain forests / Random forest / red herrings / Remote sensing / scale / Sciences du vivant / Spatial autocorrelation / Spatial models / Species diversity / species richness / Synecology / Tree alpha diversity / tree and stand measurements / Trees / Tropical rain forests / tropical tree diversity / Western Africa