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

Abstract

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.

Keywords:

• canopy cover
• cluster analysis forest
• savanna
• tropics
• vegetation categorisation

Acknowledgments

This work was funded by the UK Natural Environment Research Council through a TROBIT Consortium grant administered by the University of Leeds. Simon Lewis was funded by a Royal Society University Research Fellowship and Elmar Veenendaal received additional funding from the EU funded Geocarbon project (nr. 283080). Part of the work in Mato Grosso, Brazil, was funded by PROCAD/CAPES and we also acknowledge the support and assistance of CSIR-Forestry Research Institute of Ghana (CSIR-FORIG) and Resource Management Support Center of the Ghana Forestry Commission (FC-RMSC). WCS-Cameroon and J. Sonké provided logistical assistance in Cameroon and Annette den Holander provided fieldwork assistance in both Bolivia and Cameroon. Shiela Lloyd assisted with anger management as well as manuscript and figure preparation.