Comparative water fluxes through leaf litter of tropical plantation trees and the invasive grass Saccharum spontaneum in the Republic of Panama

The hydrological properties of leaf litter layers remain relatively unexplored, especially in tropical vegetation communities. In this paper we explore the hydrological dynamics of litter samples from reforestation plots of tropical hardwoods and the invasive sugar cane Saccharum spontaneum, which these trees were planted to replace. Water holding capacity (WHC) and drying rates were compared under controlled conditions, and throughfall interception, drainage and calculated evaporation were measured in two field experiments (A and B) conducted with different sets of samples. The WHC of samples varied from 3.4 to 6.5mm in experiment A, and from 1.6 to 7.1mm in experiment B. Drainage through the litter samples averaged 78.3±34.4% and 61.2±34.70% TF in experiments A and B, respectively. Daily water storage was 70.8±14.25% of total WHC in experiment A and 78.6±25.35% of total WHC in experiment B. Estimated evaporation averaged 34.8±12.52% of WHC in experiment A and 34.3±14.91% of WHC in experiment B. Although significant interspecific differences in WHC, interception of TF and evaporation were recorded, species rankings tended to be different in experiments A and B. The exception was litter from the leguminous tree Gliricidia sepium, which maintained the lowest WHC and water storage in the field in both experiments, but which evaporated water more rapidly than other species. The depth of throughfall draining through litter samples in the field was similar among all species in both experiments. Comparisons of regression slopes also showed that drainage depth increased with increasing throughfall at similar rates among species. On the other hand, both slopes and slope elevations differed among species when drainage was expressed in lkg⁻¹. Patterns of water storage and drainage in our samples were in broad agreement with those of other studies, although WHC and litter necromass in our young tree plantations fell into the lower end of the range reported for mature Amazonian forest.