Das, Arundhati and Nagendra, Harini and Anand, Madhur and Bunyan, Milind
(2015)
Topographic and bioclimatic determinants of the occurrence of forest and grassland in tropical montane forest-grassland mosaics of the Western Ghats, India.
Plos One.
pp. 2-19.
Abstract
The objective of this analysis was to identify topographic and bioclimatic factors that predict
occurrence of forest and grassland patches within tropical montane forest-grassland mosaics.
We further investigated whether interactions between topography and bioclimate are
important in determining vegetation pattern, and assessed the role of spatial scale in determining
the relative importance of specific topographic features. Finally, we assessed the
role of elevation in determining the relative importance of diverse explanatory factors. The
study area consists of the central and southern regions of the Western Ghats of Southern
India, a global biodiversity hotspot. Random forests were used to assess prediction accuracy
and predictor importance. Conditional inference classification trees were used to interpret
predictor effects and examine potential interactions between predictors. GLMs were
used to confirm predictor importance and assess the strength of interaction terms. Overall,
topographic and bioclimatic predictors classified vegetation pattern with approximately 70%
accuracy. Prediction accuracy was higher for grassland than forest, and for mosaics at
higher elevations. Elevation was the most important predictor, with mosaics above 2000m
dominated largely by grassland. Relative topographic position measured at a local scale
(within a 300m neighbourhood) was another important predictor of vegetation pattern. In
high elevation mosaics, northness and concave land surface curvature were important predictors
of forest occurrence. Important bioclimatic predictors were: dry quarter precipitation,
annual temperature range and the interaction between the two. The results indicate complex
interactions between topography and bioclimate and among topographic variables.
Elevation and topography have a strong influence on vegetation pattern in these mosaics.
There were marked regional differences in the roles of various topographic and bioclimatic
predictors across the range of study mosaics, indicating that the same pattern of grass and
forest seems to be generated by different sets of mechanisms across the region, depending
on spatial scale and elevation.
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