Table 3.

Results of regression analyses of Shannon diversity index (Shannon) and soil organic carbon-to-nitrogen (C:N) ratio 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 C:N ratio for quartiles of MAT	P = 0.372	P = 0.578	P = 0.568	P = 0.003 R2 = 0.38
MAP ranges (mm) of quartiles	192–522.9	523–802	803–1054	1055–2566
Regression: Shannon and C:N ratio for quartiles of MAP	P < 0.001 R2 = 0.54	P = 0.171	P = 0.075	P = 0.872
AI ranges of quartiles	0.110–0.500	0.501–0.780	0.781–1.080	1.081–2.710
Regression: Shannon and C:N ratio for quartiles of AI	P < 0.001 R2 = 0.56	P = 0.041 R2 = 0.20	P = 0.834	P = 0.278

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.