Below-ground secondary succession in tropical forests of Borneo

As the destruction and severe disturbance of primary tropical forest continues, it is important to understand how these forests may recover from perturbations. Considerable work has been done on above-ground recovery but below-ground processes are less well understood. To determine changes in root mass during tropical secondary succession in lowland forests of Central Borneo, samples were taken from stands of increasing ages since abandonment of agriculture (1, 3, 14 and 31 y) with a primary forest control (six plots from 1-y-old stands and three from all other ages). Root mass and elemental concentrations were determined and soils were chemically analysed. There was no increase in root mass with stand age for fine-root (< 2 mm diameter) or small-root (< 5 mm diameter) mass but there was a trend for coarse-root mass (5-10 mm diameter) to increase with stand age. Negative correlations were shown between root mass and soil nutrient status. Fine-root C concentrations increased with stand age but there was no clear effect of stand age on fine-root N or P. Fine-root mass did not increase significantly with stand age suggesting a rapid recovery; instead, soil nutrient status appeared to be the most important factor controlling root mass. Of the soil nutrients measured in this study, N had a stronger control over root mass than P suggesting that this element may be limiting during secondary succession in tropical lowland forests of Borneo.