Variation characteristics of soil respiration fluxes in four types of grassland communities under different precipitation intensity

A two consecutive years' field experiment was carried out on four types of semiarid grassland along precipitation gradient in Xilin River Basin of Inner Mongolia during 2001-2003 using a static enclosed black chamber technique. The variation characteristics of soil respiration fluxes from four different types of grassland along precipitation gradient were compared. The possible effect of water-heat factors on characteristics of grassland soil respiration was statistically analyzed and the numerical relational model between soil respiration and water-heat factors was established. Meanwhile the soil CO2 annual emissions of different types of grassland were estimated based on the consecutive and complete set of field observation data. The results indicate that soil respiration has apparent seasonal variation laws, seasonal variation patterns of soil respiration from different types of grassland along precipitation gradient are basically the same, soil respiration fluxes of various grassland communities are relatively high in late spring and summer but relatively low in autumn and winter, negative fluxes of soil respiration were observed from different types of grassland in winter and the further study of their mechanism is favorable for the accurate estimation of soil respiration amount; soil annual (or growth season) respiration amount of four types of grassland along precipitation gradient decreases progressively along the gradient in the order of Stipa baicalensis meadow steppe > Aneurolepidium chinense steppe > Stipa grandis steppc > Stipa krylovii steppe; soil respiration of different types of grassland during growth season is positively correlated with soil water content at depths of 0-10 and 10-20 cm to different degrees but the correlativity with air temperature and top depth soil temperature is relatively weak, variations of surface soil water content of. pes of grassland during growth season can normally four types explain 70.2%-94.7% of the variations of soil respiration fluxes, whereas during non-growth season of the plants, soil respiration are more likely restricted by air temperature and top depth soil temperature, and variations of temperature conditions can explain over 70% of the variations of soil respiration fluxes