ISRAEL CANTÚ SILVA1, HUMBERTO GONZÁLEZ RODRÍGUEZ1, MARCO V. GÓMEZ MEZA2
1University of Nuevo León, Faculty of Forest Sciences, Mexico
2University of Nuevo León, Faculty of Economics, Mexico
Determinations of CO2 efflux, soil temperature and soil-water content were monitored between July 3, 2001 and January 29, 2002. At each sampling date, two daily measurements (at 08:00 and 14:00 h local time, named as morning and afternoon, respectively) were carried out. A dynamic closed chamber with a portable system EGM employing a infrared gas analyzer (IRGA) and a soil chamber (SRC) was used to assess soil CO2 efflux throughout the experimental period in vertisols under different land uses in northeastern Mexico: Pasture (Dichanthium annulatum), Leucaena leucocephala in an alley cropping system, a native and undisturbed shrubland plot, Eucalyptus microtheca plantation, and a Sorghum bicolor field.
Results have shown that the Eucalyptus and pasture plots showed a highly significant and positive linear relationship between morning and afternoon soil respiration rate and soil temperature, while no significant relationship between any soil temperature and soil respiration for Leucaena, sorghum and shrubland land uses was found. Soil temperature alone explained 68% of the variation in the efflux rate in Eucalyptus and 33% in pasture. During the study period, average morning soil respiration rates for all land uses ranged from 0.7 to 8.4 mol CO2m-2s-1 (in Oct. and Aug., respectively), while afternoon soil respiration rates ranged from 0.6 to 14.4 mol CO2m-2s-1 throughout the experiment. Average morning and afternoon soil respiration rates showed the following decreasing CO2 efflux order among the five investigated land uses pasture>shrubland>Leucaena>Eucalytus>sorghum, indicating that pasture plot showed the highest average morning and afternoon soil respiration rates 3.5 and 5.0 mol CO2m-2s-1, respectively. In contrast sorghum shows the lowest average morning and afternoon soil respiration rates 1.9 and 2.5 mol CO2m-2s-1, respectively.
Keywords: CO2 efflux, Dichanthium grass, Eucalyptus, Leucaena, shrubland, soil respiration, sorghum, vertisol