Table 2.

Results of regression analyses of the Shannon diversity index (Shannon) and soil organic carbon (SOC) content across the grassland sites in each of the four quartiles of mean annual temperature (MAT), mean annual precipitation (MAP), and aridity index (AI)

	1. Quartile	2. Quartile	3. Quartile	4. Quartile
MAT ranges (°C) of quartiles	−7.57–7.30	7.31–10.54	10.545–15.579	15.58–24.45
Regression: Shannon and SOC for quartiles of MAT	P = 0.217	P = 0.752	P = 0.582	P = 0.003 R2 = 0.38
MAP ranges (mm) of quartiles	192–522.9	523–802	803–1054	1055–2566
Regression: Shannon and SOC for quartiles of MAP	P < 0.001 R2 = 0.46	P = 0.765	P = 0.409	P = 0.897
AI ranges of quartiles	0.110–0.500	0.501–0.780	0.781–1.080	1.081–2.710
Regression: Shannon and SOC for quartiles of AI	P = 0.002 R2 = 0.42	P = 0.392	P = 0.688	P = 0.084

The number of grassland sites in each quartile is 21 (N = 21). The R² is given for all significant (P < 0.05) regressions. Significant relationships (P < 0.05) are marked in bold font. Note that by definition the aridity index increases with decreasing aridity.