中国东部南北样带森林优势植物叶片的水分利用效率和氮素利用效率

通过测定中国东部南北样带主要森林生态系统中10种优势植物(兴安落叶松、蒙古栎、水曲柳、紫椴、色木槭、红松、杉木、木荷、马尾松、锥栗)叶片的碳氮含量(Cmass、Nmass)、同位素丰度(δ13C、δ15N)以及光合响应曲线,分析了不同优势植物叶片的水分利用效率和氮素利用效率之间的差异及其相互关系.结果表明:不同生活型植物叶片的Nmass和δ15N差异显著,表现为阔叶植物＞针叶植物,落叶植物＞常绿植物;最大光合速率(Pnmax)表现为针叶植物＞阔叶植物,落叶植物＞常绿植物;植物叶片的瞬时水分利用效率(WUEi)和长期水分利用效率(WUE)均表现为阔叶植物＞针叶植物,常绿植物＞落叶植物;植物叶片的瞬时氮素利用效率(NUEi)和长期氮素利用效率(NUE)则表现出相反的规律,且常绿植物和落叶植物叶片的NUE差异显著;WUEi和WUE之间相关性不显著,而NUEi和NUE之间呈显著正相关.植物叶片的水分利用效率与氮素利用效率显著负相关.两种资源利用效率均受植物生活型的影响,并且存在一定的制约关系.

Foliar water use efficiency and nitrogen use efficiency of dominant plant species in main forests along the North-South Transect of East China

Based on the measurements of the foliar carbon content (Cmass, nitrogen content (Nmass), isotope abundance (delta13C and delta15N), and light response curve of 10 dominant plant species (Larix gmelinii, Quercus mongolica, Fraxinus mandshurica, Tilia amurensis, Acer mono, Pinus koraiensis, Cunninghamia lanceolata, Schima superba, Pinus massoniana, and Castanea henryi) in the main forests along the North-South Transect of Eastern China (NSTEC), this paper analyzed the differences and the relationships between the foliar water use efficiency and nitrogen use efficiency of the plant species. There existed significant differences in the foliar Nmass and delta15N among the plant species, manifesting as broadleaved species > coniferous species, and deciduous species > evergreen species. The maximum photosynthetic rate (Pn max) was coniferous species > broadleaved species, and deciduous species > evergreen species. Broadleaved and evergreen species tended to have higher foliar instantaneous water use efficiency (WUEi) and long-term water use efficiency (WUE), as compared to coniferous and deciduous species, but an opposite trend was observed in the foliar instantaneous nitrogen use efficiency (NUE) and long-term nitrogen use efficiency (NUE). Moreover, there was a significant difference in the foliar NUE between evergreen and deciduous species. No significant correlation was observed between WUEi and WUE, but a significant positive correlation existed between NUEi and NUE. There was a significant negative correlation between the foliar water use efficiency and nitrogen use efficiency at instantaneous or long-term time scales. In sum, the foliar water use efficiency and nitrogen use efficiency were dominated by plant life-form, and a trade-off existed between the two resources use efficiencies.