SOIL RESPONSES TO RESTORATION OF A TROPICAL PASTURE IN VERACRUZ, SOUTH-EASTERN MEXICO

Investigations were carried out on litter nitrogen (N) and phosphorus (P), and soil carbon (C), N and P in an active pasture, a mature tropical rainforest, and two treatments of restoration (cattle exclusion alone and combined with planting of tree seedling) in Veracruz, Mexico. The aim was to outline how the two treatments of restoration affect the recovery of soil nutrient status in the short-term (one year). Thirty years of cattle ranching activities decreased the litter N and P pools by a factor of 72 in the former and 31 in the latter, largely reflecting differences in litter mass between pasture and mature forest. Pasture soils consistently had lower pools of organic C and total N and ammonium (NH4 +) than forest soils. However, landuse did not affect the pool of soil nitrate (NO3 -), and total and extractable P. Exclusion of grazing and exclusion of grazing plus planted tree seedlings increased N and P pools in the litter. In contrast, restoration treatments did not consistently affect soil C, N and P. The main response to restoration practices was a decrease of NO3 - and extractable P pools in soils. Overall, we observed that, subsequent to these practices, there were significant changes in the recovery of nutrient pools reaching levels similar to tropical forest soil.