Recovery of species diversity and composition of braconid parasitic wasps after reforestation of degraded grasslands in lowland East Kalimantan

Abstract

Human-induced disturbances and wildfires can transform areas of tropical rainforest into Imperata-dominated grassland, but it may be possible that recovery of biodiversity is facilitated by reforestation with fast-growing trees. We compared the assemblages of braconid wasps as parasitoids of taxonomically diverse groups of insects among Imperata grasslands, young and mature plantations of Acacia mangium, young secondary forests after wildfires, and old secondary forests in the lowland of East Kalimantan. The abundance and species richness of braconids, which had declined in Imperata grasslands, somewhat increased in Acacia plantations, and also the species composition of braconids in Acacia plantations was transitional between Imperata grasslands and old secondary forests. Parasitoids of detritivores and wood borers increased markedly after plantation, while those of herbivores showed a distinct turnover of species all over the range from grasslands to old secondary forests. The plantation of A. mangium had most likely facilitated the recovery of the diversity of host forest and their parasitoids, but the recovery was just at the rudimentary stage even in mature plantations. Monitoring of parasitic wasps would be useful to test the continuous recovery of forest biodiversity in plantation stands.