Seasonal Fluctuation of Soil Carbon Dioxide Emission in Differently Managed Pastures

Soil carbon dioxide emission (ECO2) is a process determined by biotic and abiotic factors influenced by land use and management practices. In grassland ecosystems, grazing intensity may affect C input from plants into soil, and thus may also change soil respiration rate. Indeed, limited information is available regarding the effects of grazing management on ECO2. This study was conducted to evaluate ECO2 seasonal variation, and its relationship to soil temperature (Tsoil) and precipitation, in an area with different pasture heights of Marandu palisade grass [Brachiaria brizantha (A. Rich.) Stapf.]. The pasture heights (15, 25, and 35 cm) were distributed in a completely randomized design with 12 repetitions in each area. The evaluations of ECO2 and Tsoil occurred from January 2011 to February 2013, totaling 73 d of observation that were distributed according to climatic seasons. The results showed that seasonal variation of ECO2 was directly related to variations in precipitation and Tsoil. Soil CO2 emission was higher in summer and lower in winter. The data variability of ECO2 was higher in rainy, hot summers than in dry, cold winters. A positive linear association between ECO2 and Tsoil was observed in summer and autumn. In most seasons measured, ECO2 reduced with increasing pasture height. Accordingly, 2-yr data indicated that accumulated ECO2 decreased with increasing pasture height. Thus to better understand the effect of pasture height on ECO2, a shorter period of measurements is not suitable since a different result was observed in the first year of evaluation.