Altitude patterns of leaf carbon isotope composition in a subtropical monsoon forest

Leaf carbon isotope composition (delta C-13) of both vascular and non-vascular plants were investigated in order to assess their variability along an altitude gradient (414, 620, 850, 1086, 1286 and 1462 m) from a subtropical monsoon forest located at Mt. Tianmu Reserve, eastern China. Leaf delta C-13 values of all plant species ranged from -34.4 to -26.6 parts per thousand, with an average of -29.8 parts per thousand. There is no significant difference in leaf delta C-13 between vascular plants and mosses, however, trees had significantly higher delta C-13 values than herbs. For pooled data, leaf delta C-13 was positively correlated with altitude. Leaf delta C-13 was significantly and negatively correlated with annual mean temperature and atmospheric pressure, while it was significantly and positively correlated with soil water content. Furthermore, there was no relationship between leaf delta C-13 and soil nitrogen content or soil phosphorus content. The altitudinal trend in leaf delta C-13 is the consequence of the interaction between temperature, atmospheric pressure and soil water content.