Table 2.
The linear relationship between mean C (δ13C) and N isotopic composition (δ15N) values and the C/N ratio from C3 plant sites and mean annual rainfall
| Rainfall (Ln mm/year) | β | α | n | R 2 | P |
|---|---|---|---|---|---|
| δ13Ca | |||||
| W | −0.82 (−1.17) | −22.95 (−20.76) | 23 (17) | 0.41 (0.67) | <0.05 (<0.001) |
| D | −0.55 (−0.78) | −22.88 (−21.74) | 18 (15) | 0.18 (0.44) | 0.086 (<0.01) |
| Dg | −0.96 (−1.73) | −20.75 (−15.97) | 17 (14) | 0.32 (0.79) | <0.05 (<0.001) |
| Dd | −0.97 (−1.22) | −21.74 (−20.19) | 17 (16) | 0.45 (0.61) | <0.01 (<0.001) |
| A | −0.58 (−0.96) | −23.59 (−21.21) | 39 (30) | 0.14 (0.33) | <0.05 (<0.001) |
| δ15Nb | |||||
| W | −2.60 (−3.47) | 15.09 (20.43) | 23 (17) | 0.39 (0.70) | 0.001 (<0.001) |
| D | −2.69 (−3.32) | 15.38 (19.71) | 16 (14) | 0.58 (0.76) | <0.001 (<0.001) |
| A | −2.59 (−3.45) | 14.96 (20.69) | 39 (28) | 0.46 (0.76) | <0.001 (<0.001) |
| C/Nb | |||||
| W | 3.19 (2.99) | 3.73 (4.84) | 21 (15) | 0.28 (0.21) | <0.05 (0.087) |
| D | 4.67 (5.65) | 12.32 (5.94) | 20 (17) | 0.43 (0.50) | <0.01 (<0.01) |
W Wet season; D dry season; Dg dry season green plants; Dd dry season dried plants; A annual, combined wet and dry period; n number of sites; β slope; α intercept
P values < 0.05 are marked in bold
aDry wash desert sites are excluded from the δ13C regression analysis, results are shown in parentheses
bExposed ridge sites are excluded from the δ15N and C/N analysis, results are shown in parentheses