Consequences of increasing forest use intensity for biomass, morphology and growth of fine roots in a tropical moist forest on Sulawesi, Indonesia

Tropical moist forests in South-East Asia are heavily exploited by timber extraction and forest conversion into agroforestry systems. Twelve forest stands were selected to investigate fine root biomass, morphology, and growth along a gradient of increasing forest conversion from near-natural forest to cacao agroforestry systems in Central Sulawesi, Indonesia. Fine root biomass decreased markedly with increasing forest disturbance. Fine root growth rate showed a weak dependence on forest disturbance, whereas fine root turnover (growth per standing fine root biomass) was higher in the more heavily disturbed stands. Specific root area was higher in the stands with large timber extraction and fine root N concentration was particularly high in the cacao agroforests. These two root morphological traits were positively related to fine root turnover. We conclude that the higher growth activity of fine roots in the moderately and heavily disturbed forests resulted from differences in fine root morphology and N concentration, hence partly compensating for the decrease in fine root biomass with disturbance.