Data from: Carbon isotopes of C3 herbs correlate with temperature on removing the influence of precipitation across a temperature transect in the agro-pastoral ecotone of Northern China

Plant δ13C–temperature (δ-T) relation has been established in many systems
and is often used as paleotemperature transfer function. However, it is
still unclear about the exact contributions of temperature variation to
plant 13C discrimination because of covariation between temperature and
precipitation (aridity), which reduces confidence in reconstruction of
paleoclimate. In this study, we measured carbon isotope composition (δ13C)
of 173 samples of C3 perennial herbs from 22 sites across a temperature
gradient along the 400 mm isohyet in the farming-pastoral zone of North
China. The results showed that precipitation obviously affected the
correlations of temperatures and foliar δ13C. After removing the influence
of precipitation by analysis of covariance (ANCOVA), a more strongly
positive relationship was obtained between site-mean foliar δ13C and
annual mean temperature (AMT), with a regression coefficient of 0.1636‰/°C
(p = .0024). For widespread species, Artemisia lavandulaefolia and
Artemisia capillaries, the slopes (or coefficients) of foliar δ13C and AMT
were significantly steeper (larger) than those of foliar δ13C and AMT
where the precipitation influence was not excluded, whereas the δ-T
coefficients of Polygonum persicaria and Leymus chinensis showed little
change across the transect after deducting the precipitation effect.
Moreover, the positive relationship between temperature and δ13C over the
transect could be explained by soil moisture availability related to
temperature. Our results may afford new opportunities for investigating
the nature of past climate variability.