Effects of burning strength in shifting cultivation on the early stage of secondary succession in Sarawak, Malaysia

Abstract

The effects of burning strength in shifting cultivation on the early stage of secondary succession in tropical rain forest was investigated at four sites (Sabal, Balai Ringin, Niah, and Bakam) in Sarawak, Malaysia. The number and growth (diameter, height, and biomass) of germinated seedlings were measured in experimental shifting cultivation plots in which the burning strength varied between 0, 100, 200, and 300 t/ha at Sabal, Balai Ringin, and Niah and 0, 20, and 100 t/ha at Bakam. Species composition of germinated tree and herbaceous seedlings was surveyed, and a germination test of buried seed was conducted at Niah and Bakam. The number of germinated seedlings decreased with increasing burning strength, whereas seedling growth was promoted by burning. During the first year, growth was best in the intermediate burning strength plots, whereas during the second year, growth was best in the most strongly burned plots. Species composition differed between unburned and burned sites. Site-specific factors such as original stand biomass, soil properties, and invasion of exotic species also affected germination and growth. Buried seeds in the Ao layer were killed by burning, and nearly all seeds in the 0-5 cm layer were killed in the plots with the highest burning strength (> 100 t/ha). On the basis of our findings, we conclude that in shifting cultivation systems burning promotes vegetation recovery when the burning strength is properly managed.