Effects of irrigation on litterfall, fine root biomass and production in asemideciduous lowland forest in Panama

The effects of irrigation on fine root biomass, root production and litterf all were measured at the community level, in a semideciduous lowland forest in Panama. Biomass of roots less than 2 mm in dia. in the first 10 cm of t he soil (measured with soil cores), was higher in irrigated (1.80 Mg ha(-1) ) than in non-irrigated plots (1.24 Mg ha(-1)). During the dry season, prod uctivity of roots (measured with ingrowth cylinders filled with root-free s oil), was higher in irrigated (1.6 g m(-2) day(-1)) than in control plots ( 0.3 g m(-2) day(-1)). In control plots, root productivity was highly season al. Maximum root growth into the root-free soil, occurred during the transi tions from dry to wet, and from wet to dry season, possibly as a response t o water and/or nutrient pulses. Litterfall was not significantly different between irrigated (3.8 g m(-2) day(-1)) and control plots (3.7 g m(-2) day( -1)). The results of this study show that root-productivity is limited by t he water supply during the dry season, and that water by itself, is not a l imiting factor for community-level litter production.