influence of silvopastoral system “live fences” of gliricidia sepium on soil respiration in tacotalpa, tabasco, mexico

The aim of this study was to quantify rates of soil respiration on livestock systems with live fences (LF) formed by Gliricidia sepium trees and on livestock systems in signal grass monoculture (MP) (Brachiaria decumbens); examine the variation of flows in the rainy and dry seasons, and fluctuations during the day, as well as soil temperature and relative humidity. Soil respiration was measured twice a month, four times a day between the hours of 00:00 to 06:00 h, 6:00 to 12:00 h, 12:00 to 18:00 h, and 18:00 to 24:00 h, in both seasons. Soil temperature and the relative humidity were simultaneously measured. The results show that the rate of soil respiration is similar between these systems, LF issued 0.97 and MP 1.01 mol CO2 m2 h-1. In contrast, there was influence of the time of year and time of collection of the samples. In both systems the soil flows were higher in the rainy season (1.1 mol CO2 m2 h-1 on average) and slightly lower in the dry season (0.90 mol CO2 m2 h-1 on average) and were higher during the night (00:00 to 06:00 hours), during the early morning hours (6:00 to 12:00 hours). Soil temperature was higher in the MP, and the relative humidity in LF. It is concluded that the main factor that caused the variation in soil respiration rates was the presence of G. sepium trees in LF, which led to lower temperatures and more stable humidity, which resulted in lower soil CO2 fluxes.