Abstract:In order to understand the spatial variability of soil respiration and its influencing factors, soil respiration (Rs) and related factors including soil temperature at 10 cm depth (T10), soil water content from 0 to 10 cm depth (Ws), litter fall mass (Lw), litter fall moisture (Lm), soil total carbon (C), soil total nitrogen (N), and soil sulfur (S) were determined at 4, 2, and 1 m sampling scales, in a conifer-broadleaf mixed forest in Pangquangou nature reserve area of Shanxi province. The goals of this investigation were to monitor Rs heterogeneities at the stand scale and determine the correlations between Rs and affecting factors. The results from traditional statistics indicated that coefficients of variation (CV) for most of the measured factors ranged between 15%-59%; T10 and C/N ratio were approximately 10%. The spatial variations of both T10 and C/N ratio had low variability (CV ≤ 10%), and the others had medium variability (10% ≤ CV ≤ 100%). The simple linear correlations between Rs and Lw, Lm, C, N, and T10 were all highly significant (P < 0.01); the correlation between Rs and Ws was significant (P < 0.05). However, no significant relationship between Rs and C/N ratio and S (P > 0.05) was observed. Stepwise multivariate regression demonstrated that the four factors of Lw, T10, N, and C/N ratio together accounted for 26% of Rs heterogeneity, with the equation Rs = 11.972 + 0.033Lw- 0.267T10 + 8.058N-0.390C/N (R2 = 0.26, P = 0.000). Principal component analysis showed that the soil substrates of C and N, the environmental factors of T10 and Lm, and the biotic factor of Lw could account for more than 70% of the spatial variation in Rs. The results from the geo-statistical analysis showed that the environmental factors of T10, Ws, Lm, C, N, and C/N ratio had a significant spatial autocorrelation, and that structural factors played a leading role in their heterogeneity. S had a weak spatial autocorrelation, showing a random factor acted on its heterogeneity. The range of the semi-variogram function was about 17 m for Rs and the influencing factors. Fractal dimension was used to measure the complexity of natural phenomena, and the rank for the selected factors was in the following order: Lw (1.87) > S (1.84) > Lm (1.82) > N (1.77) > Rs (1.74) > C (1.73) > Ws (1.69) > T10 (1.56) > C/N ratio (1.46). The spatial distribution model of Rs showed a similar pattern to that of Ws, Lm, Lw, C, N, and S, but not similar to that of T10. The required sampling numbers of the Rs for 4, 2, and 1 m scales within ±5% and ±10% of its actual mean at the 95% confidence level were 74, 44, and 39, and 19, 11, and 10, respectively. This showed a decrease in the required sampling number coinciding with a decrease in the sampling scale; there was a similar trend in the estimation of accuracy. Our research results may have important applications in the study of CO2 efflux in similar semiarid regions.