Clarifying the influence of temperature on variances in plant metallic nutrients through minimizing the effect of precipitation.

Understanding the responses of plant nutrients to climate warming is important in the research of global change. However, the responses of plant metallic nutrients to climate warming have been rarely addressed. Furthermore, in previous field investigations, the influence of temperature on plant metallic nutrients has been not effectively separated from that of precipitation; hence, there exists some uncertainties in the relationships between plant metallic nutrients and temperature. To minimize the effect of precipitation, this study collected plant samples over broad geographical scale along the 400 mm isohyet in China with a temperature span of 14.8 °C. The temperature effects on variations in leaf potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn) and zinc (Zn) were assessed. For all species pooled together, leaf Ca and Mg kept relatively stable, whereas leaf K, Fe, Mn and Zn decreased with increasing temperature. The responses of leaf Ca, Mg and Mn to changing temperature were almost similar at functional group, genus and species levels and independent of vegetation and soil type. It suggested that the relationships between leaf Ca, Mg and Mn and temperature should be general results. However, the patterns of leaf K, Fe and Zn vs. temperature varied across functional groups, genera and species and were affected by vegetation and soil type, which indicated that the observed patterns were local phenomena. Our results suggested that global warming might have no effect on leaf Ca and Mg, but could decrease leaf K, Fe, Mn and Zn.