Study on the impact of selective logging on the abundance of anurans in the rain forests of Central Kalimantan, Indonesia

Abstract

Tropical rain forests are among the most complex natural habitats in the world and widely recognised as areas of high species diversity of both flora and fauna. Despite their biological and ecological importance tropical rain forests throughout the world are coming under pressure to be exploited for timber resources. Where management of rainforests for timber production is carried out on an unsustainable basis, serious degradation of the forest ecosystem may result, followed by loss of forest cover and/or species extinction. Therefore, there is a vital need to understand the effects of forestry practices on these diverse ecological systems and on individual species.

Vertebrates like birds and primates have been widely studied and recognised as a key indicator species for environmental stress. Anurans (amphibians) have also been identified as potentially valuable indicators of some environmental changes. The small home ranges and relatively limited dispersal ability may render amphibians useful for monitoring the effects of local environmental pertubations. In addition, their moist permeable eggs and skin also make them good bioindicators of environmental stress. Amphibians are also important in the food chain and nutrient cycling. They represent a high quality prey item (high in protein and phosphorus content) to predators. They may also play a unique role in forest nutrient cycling by regulating populations of soil invertebrates responsible for the mechanical breakdown of organic material.

Given both the important roles and functions of amphibians in forest ecosystems and the significant impacts of logging on forest ecoystems, an understanding amphibians in relation to forestry practices is required. Relatively few studies have focussed on the impact of logging on amphibians especially in the tropics. Those that have been undertaken have related mainly to temperate regions where the logging is usually clear felling and they have concentrated either on single species or on single genera. Therefore, this study will attempt to address this gap of knowledge about the impacts of selective logging on the abundance of anurans in the rain forests of Kalimantan, Indonesia. The study was undertaken from November 1994 to July 1996 at Camp 92, Central Kalimantan. Three samplingmethods were used in this study e.g. pitfall traps, searched quadrats and night riparian transects.

The results demonstrate that logging had a significant effects on the abundance of anurans and anuran species composition. Logging had a strong influence on vegetation cover, which in turn affects the temperature and humidity. Logging also affects the physical characteristic of the streams especially the bottom substrates. The combination of these associated factors strongly affects the abundance of anurans. The challenge in research for future researchers of amphibian-forestry relationships is to identifying realistic timber harvest prescriptions that best maintain those components of the forests biological legacy that are essential for healthy amphibian populations and forest ecosystem as a whole.