图7. 降水量变化下荒漠草原土壤呼吸速率与环境因子的结构方程模型。CP, 降水量; PB, 植物生物量; R, Patrick丰富度指数; SBP, 土壤生物学性质(蔗糖酶活性、脲酶活性、磷酸酶活性、微生物生物量碳含量); SCP, 土壤化学性质(pH、电导率、有机碳、速效磷含量); SPP, 土壤物理性质(含水量和温度); SR, 土壤呼吸速率。黑色实线和虚线分别表示显著(p < 0.05)和不显著(p > 0.05)路径。箭头上数字为标准化的路径系数(*, p < 0.05; **, p < 0.01; ***, p < 0.001)。模型拟合总结: χ² ?= 5.709, p = 0.457, df = 6; 拟合优度指数(GFI) = 0.998; 标准化残差均方根(RMSEA) = 0.000; 相对配适指数(SRMR) = 0.035。

Fig. 7. Structural equation model of soil respiration rate and environmental factors under changing precipitation regimes in a desert steppe. CP, precipitation; PB, plant biomass; R, Patrick richness index; SBP, soil biological properties (sucrase activity, urease activity, phosphatase activity, microbial biomass carbon content); SCP, soil chemical property (pH, electrical conductivity, organic carbon, available phosphorus content); SPP, soil physical property (water content and temperature); SR, soil respiration rate. Black solid and dashed arrows indicate significant (p < 0.05) and insignificant (p > 0.05) path, respectively. Numbers on the arrows are normalized path coefficients (*, p < 0.05; **, p < 0.01; ***, p < 0.001). Model fit summary: χ² = 5.709, p = 0.457, df = 6; comparative fit index (GFI) = 0.998; root mean square error of approximation (RMSEA) = 0.000; standardized root mean square residual (SRMR) = 0.035.