Secondary succession after fire in Imperata grasslands of East Kalimantan, Indonesia

Regeneration of grassland areas is becoming increasingly important, not only to create new secondary forest and recover the original biodiversity, but also recover for agriculture. We studied an early succession in Imperata grasslands in East Kalimantan, Indonesia, using plots that last burned 3 years, 4 years and 9 years previously on, secondary and primary forest. The species coverage data were analyzed using CANOCO. While Imperata decreases, the average percentage of shrubs and young trees clearly increases with time. In the burned plots, Melastoma malabathricum, Eupatorium inulaefolium, Ficus sp., and Vitex pinnata L. strongly increase with the age of regeneration, but these species were rare in the secondary forest. Texture strongly influenced regeneration: soils with more than 50% sand had a slower development towards secondary forest. The number of species was lower in the more sandy soils. The latter showed a stronger increase with time of Pteridium aquilinum L., which appears to slow down the subsequent vegetation development. Canonical correspondence analysis (CCA) of the environmental gradient and vegetation showed that pH, bulk density, sand and clay are the factors influencing the distribution of species. CCA showed also that soil properties had a strong influence on vegetation composition. M. malabathricum, V. pinnata L., Lycopodium cernum, Vernonia arborea Buch.-Ham., Dicranopteris linearis are all species associated with high levels of exchangeable Al and low pH. Imperata grasslands are not a final and stable stage of land degradation, but, when not maintained by frequent fires and human disturbances, regenerate spontaneously and rapidly to secondary forest. The introduction of native shrubs and trees will speed up this process. Recovery for agriculture has not been studied but should not pose major problems under management system without fire.