[Soil respiration rates and its affecting factors in winter wheat land in the Weihe Plain, Northwest China.]

Based on measurement on winter wheat soil respiration (SR), environmental and biotic factors from 2013 to 2014 in semi-humid and prone-to-drought area of Weihe Plain, this paper analyzed the characteristics of diurnal and seasonal variation of SR and influences of temperature (T), soil water content (W), gross primary productivity (GPP) and leaf area index (LAI). The results showed that the SR diurnal variation appeared as a single-peak curve ranging between 1.5 and 6.94 μmol CO₂·m^-2·s^-1, with the peak presented during 12:00-14:00. Temperature was the driving factor for the SR diurnal variation, and land surface temperature (T_s) could explain 80.9% of the temporal variation for SR. The corresponding relationship between SR and temperature showed a clockwise nearly elliptic curve. From seedling stage to winter, the SR rate of wheat showed a descending trend, and stayed at a relatively low level until regreening stage. Then the rate of SR increased rapidly and reached peak in heading stage and filling stage, but there was a descending trend in mature stage. The SR values in growth period were between 0.65 and 4.85 μmol CO₂·m^-2·s^-1. T, W, GPP and LAI were positively related to SR (P<0.01). Soil temperature and soil water content were the dominant factors affecting the SR seasonal variation, and they could explain 82.6% of its variation by a compound model SR=$e^{(a+bT_{5 cm}+cW_{10 cm}+dW_{10 cm}^2)}$, which was much better than monovariant model (below 65.7%). Based on the compound model results, the average rate of wheat SR during growth period in 2013-2014 was 1.67 μmol CO₂·m^-2·s^-1.