Soil carbon storage is promoted more by Jícaro than by Guácimo trees in silvopastoral systems in Nicaragua

Abstract The role of solitary trees in providing ecosystems services to silvopastoral systems gained attention in recent years. Next to providing fodder (fruits), fuel and timber wood, trees are also likely to affect soil characteristics and the cycling of C and nutrients in their vicinity. These tree – soil effects are hypothesized to affect soil respiration (CO2 efflux) and C stabilisation. The soils in the Rivas area were formed in marine clay and sand deposits of young Tertiary age. For this study, 6 Guazuma ulmifolia (Guácimo) and 6 Crescentia alata (Jicaro) trees were selected in relatively flat parts of the landscape. Soils were classified as Vertic Haplustolls (Mollisols on gently sloping alluvial fans) and Haplusters (Vertisols in the central parts of depressions). Soil samples and soil respiration measurements were collected from three locations near each tree: 1 pasture – no tree effect (10 m up-wind from the tree); 2 tree canopies – above and belowground tree litter input; 3 pasture and aboveground leaf litter input (down-wind zone where most leaf litter is deposited). Soil samples were taken to represent the 0 – 20 and 20 – 50 cm depth increments. Soil bulk density was affected by soil type (P=0.011), tree species (P