Effects of nitrogen and phosphorus fertilization in a lowland evergreen rainforest

A nutrient addition experiment was set up in August 1993 in a species-rich primary lowland dipterocarp forest in Barito Ulu, Central Kalimantan, Indon esia. The following treatments were applied: control, +N, +P and +NP. There were five blocks of four 50 m x 50 m plots with a separate treatment for e ach plot. Fine litterfall was measured on all the plots from 1 May 1994 for 12 months. Litterfall mass and phosphorus concentrations were significantl y higher in all the fertilizer treatments compared with the controls. All t rees (greater than or equal to 10 cm dbh) were measured in August 1993 and in August 1998, and there was no significant girth increment response to fe rtilization in dipterocarps or non-dipterocarps. Dipterocarps of the red me ranti group showed a doubling of girth increment in the +NP treatment, howe ver, the difference from the control fell short of significance.