氮磷添加对金露梅叶片化学计量及光合特征的影响

通过三种养分添加处理,氮添加(5、10和15 g??m-2)、磷添加(梯度同氮添加)、氮磷同时添加[(5 g N＋5 g P)??m-2、(10 g N＋10 g P)??m-2、(15 g N＋15 g P)??m-2],对照(无养分添加),探讨养分添加对金露梅叶片性状氮含量(Nmas )、磷含量(Pmas )、氮磷比(N∶P)、比叶重(LMA)、净光合速率(Pn )和光合氮利用效率(PNUE)的影响,以及各性状之间的相互关系.结果表明：在处理水平上,除N或P显著提高金露梅叶片的N∶P外,氮、磷添加对叶片其它性状无显著影响；不同氮、磷处理下添加水平对金露梅叶片的Nmas、N∶P、Pn和PNUE均有显著影响,随着养分水平提高,各性状的变化模式各不相同,叶片Pmas无明显变化,而叶片LMA虽有降低的趋势但不显著.回归分析表明,叶片Pmas与Nmas之间呈显著正相关(R2＝0．347,P＜0．001),叶片Nmas 与N∶P之间也呈显著正相关(R2＝0．018,P＜0．05),而叶片Pmas与N∶P呈显著负相关(R2＝0．505,P＜0．001)；叶片LMA与Pn之间显著负相关(R2＝0．02,P＜0．05),而与PNUE之间显著正相关(R2＝0．077,P＜0．001).这表明在一定范围内,环境变化可以改变金露梅叶片的养分保持能力、光合能力以及养分利用效率.

Effects of N and P additions on foliar stoichiometry and photosynthetic characteristics of Potentilla fruiticosa

In a global context,increasing of nitrogen and phosphorus are affecting the ecosystem biogeochemical cycles,which may have an impact on nutrient retention properties of plants. We studied the potential effects of nutrients additions on foliar nutrient and photosynthetic traits of Potentilla fruiticosa in a sub-alpine meadow,and the relationships between these leaf traits. The treatments involved additions of 5,10 and 15 g·m^-2 nitrogen(N),phosphorus(P)alone and combined,respectively,and a control(no nutrient added). The results showed,at the treatment level,N or P addition alone increased N:P ratio(N:P)significantly of P. fruiticosa,but nutrients addition treatments had no significant effect on foliar nitrogen content(N_mass),phosphorus content(P_mass),leaf mass per area(LMA),net photosynthetic rate(P_n)and photosynthetic nitrogen use efficiency(PNUE). Nutrient levels had significant effect on foliar N_mass,N:P,P_n and PNUE in each treatment,except P_mass and LMA in P addition alone,and there was a decreasing but insignificant trend of LMA with increasing nutrients levels. Across the study,the N_mass was positively correlated with the P_mass(R²=0.347,P<0.001)and the N:P(R²=0.018,P<0.05),while the P_mass was significantly negatively correlated with the N:P(R²=0.505,P<0.001). The LMA had a significantly negative relationship with the P_n(R²=0.02,P<0.05),but a significantly positively one with the PNUE(R²=0.077,P<0.001). In general,these results suggested moderate environmental change would change nutrient retention,photosynthetic capacity and nutritional use strategy of P. fruiticosa.