青藏高原东部高山植物的水分利用效率与氮素利用效率研究

对生长在青藏高原东部隶属于23科、49属的71种高山植物(包括多年生和一年生植物)的稳定碳同位素比值、氮含量以及碳/氮比率进行了分析,并以稳定碳同位素比值及碳/氮比率来分别指示植物的水分利用效率和氮素利用效率.结果表明:(1)多年生植物稳定碳同位素比值显著高于一生年植物,而碳/氮比率显著低于一年生植物(P<0.01),氮含量两者无显著性差异.(2)多年生植物和一年生植物的稳定碳同位素比值均与碳/氮比率呈显著负相关(-0.643**和-0.707),而与氮含量均无明显相关性.研究证实,在自然条件下多年生植物的水分利用效率比一年生植物更高,而氮素利用效率却更低;高山植物水分利用效率和氮素利用效率存在明显的权衡",即植物不能同时提高水分利用效率和氮素利用效率,高水分利用效率的代价是降低氮素利用效率,青藏高原不同植物即使在相同环境条件下具有不同适应对策.

Water Use Efficiency and Nitrogen Use Efficiency of Alpine Plants Grown in the East of Qinghai-Tibet Plateau

Nitrogen concentrations, C/N ratios and δ13C values of 71 alpine plants(perennials and annuals) grown at the east of Qinghai-Tibet Plateau in natural condition were measured. δ13C values were used to de note the long-term water use efficiency(WUE) of plants whereas long-term nitrogen use efficiency(NUE) was estimated by the ratio of C to N. The results indicated that (1) perennials had higher δ13C values and lower C/N ratios compared with annuals (P＜0.01). On the contrary, the N concentrations of perennials and annuals was similar (P＞0.05). (2)δ13C values were not correlated with N concentrations in perennials or annuals (P＞0.05) ,whereas significantly negative correlations between δ13C values and C/N ratios were found for all samples (P＜0.001) ,or for perennials (P＜0.001) or annuals (P＜0.05) analyzed separately. The results revealed there was a trade-off between WUE and NUE for alpine plants in natural condition,i. e. alpine plants could not irnprove WUE and NUE simultaneously. The cost of a high WUE was a low NUE,and vice versa,which may be associated with the different life strategies for different species in the extremely natural condition in Qinghai-Tibet Plateau. In addition,the differences of δ13C values or C/N ratios between perennials and annuals suggested perennials had higher WUE and lower NUE compared with annuals,re flecting the different adaptations of alpine with different life span to environmental condition.