Contrasting Fire Regimes in a Seasonally Dry Tropical Forest and a Savanna Ecosystem in the Western Ghats, India

Narendran Kodandapani

doi:10.4996/fireecology.0902102

Narendran Kodandapani

Open Access

https://doi.org/10.4996/fireecology.0902102

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Abstract

AbstractTropical dry forests and savannas constitute more than half of all tropical forests and grasslands, but little is known about forest fire regimes within these two extensive types of ecosystems. Forest fire regimes in a predominantly dry forest in India, the Nilgiri landscape, and a predominantly savanna ecosystem in the Sathyamangalam landscape, were examined. Remote sensing data were applied to delineate burned areas, determine fire size characteristics, and to estimate fire-rotation intervals. Belt transects (0.5 ha) were used to estimate forest structure, diversity, and fuel loads. Mean area burned, mean number of fires, and mean fire size per year were substantially higher in the Nilgiri landscape compared to the Sathyamangalam landscape. Mean fire-rotational interval was 7.1 yr in the Nilgiri landscape and 44.1 yr in the Sathyamangalam landscape. Tree (≥10 cm diameter at breast height) species diversity, tree density, and basal area were significantly higher in the Nilgiri landscape compared to the Sathyamangalam landscape. Total fuel loads were significantly higher in tropical dry and moist deciduous forests in the Nilgiri landscape, but total fuel loads were higher in the tropical dry thorn forests of the Sathyamangalam landscape. Thus, the two landscapes revealed contrasting fire regimes and forest characteristics, with more and four-fold larger fires in the Nilgiri landscape. The dry forests and savannas could be maintained by a combination of factors, such as fire, grazing pressures, and herbivore populations. Understanding the factors maintaining these two ecosystems will be critical for their conservation.

Highlights

The Indian sub-continent is extremely diverse in terms of climate, vegetation type distribution, and flammability of vegetation types
Forest fires are annual disturbance events in the two landscapes dominated by dry forests and savannas in the Western Ghats (WG) (Kodandapani et al 2004)
The two landscapes are different in terms of their protected area histories, this alone may not be the chief reason for the large differences in the magnitude of the forest fire regimes

Summary

Introduction

The Indian sub-continent is extremely diverse in terms of climate, vegetation type distribution, and flammability of vegetation types. The rich biological diversity in the forests of India has resulted in four regions (Western Ghats, Himalayas, Indo Burma, and Sundaland) being designated as hotspots of biodiversity among 34 global hotspots (Mittermeier et al 2005). Carbon dating of charcoal from the Western Ghats indicates forest burning as early as 5000 yr BP (Chandran 1997). Fires set in agricultural landscapes to clear land of crop residues escape into adjoining forest areas (Saha 2002). Shifting cultivation that slashes and burns vegetation to clear land is extensively practiced in parts of northeastern India, as well as in central parts of India (Ravindranath and Sukumar 1998). Fires are introduced into forests by various indigenous communities to aid in the collection of non-timber forest products (Narendran et al 2001, Saha 2002)

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