Can the scaling of plant nitrogen to phosphorus be altered by global change? An empirical test

全球变化可能引起土壤中各种养分的供应失衡,进而导致陆地植物中氮(N)和磷(P)元素化学计量学的不平衡。前人的研究报道了全球变化因子对植物N、P含量和N:P的影响,但鲜有研究探讨全球变化因子是否影响以及如何影响这两种元素之间的异速关系。本研究利用改变降水(增雨和干旱)、增温和N添加处理的野外控制试验,结合异速函数N=βPα(或对数转换后的线性关系:Log N=Logβ+αLog P),检验了中国西北地区黄土高原半干旱草原植物N和P化学计量特征及N和P之间的异速关系对这些全球变化因子的响应。研究结果表明,干旱和增温均降低了植物P浓度,N添加增加了植物N浓度,这些都导致植物N:P增加。干旱、增温和N添加没有显著改变植物N和P浓度之间异速关系的斜率(即N和P浓度对数转换后的线性关系斜率α),但是显著增加了其截距(Logβ)。这些结果表明,全球变化因子可能不会影响植物N和P之间的协同变化关系,植物中N和P之间可能存在着紧密的耦合关系。这些结果将有助于我们更好地理解全球变化背景下的植物养分动态和元素平衡。

Aims Global change may cause unparalleled supplies of soil nutrients and further lead to stoichiometric imbalance of nitrogen(N)and phosphorus(P)in terrestrial plants.While previous studies had reported the effects of global change factors on plant N,P contents and their ratios,few had examined whether or how these factors may influence the scaling of these two elements.Methods Taking advantage of a manipulative experiment with altered precipitation,warming and N addition,and using the general scaling function N=βPα,we examined how the scaling of plant N to P may respond to global change factors in a Loess grassland in northwestern China.Important Findings We found that precipitation reduction(PR)and warming decreased plant P concentrations,while N addition increased plant N concentrations,resulting in increased N:P ratios.The slopes of the linear regressions between plant N and P(i.e.log-transformed N versus P)did not change significantly,whereas the intercepts increased significantly under PR,warming and N addition.These results indicate that global change factors may not affect the synergistic variation of plant N and P,showing a closely coupled relationship between them.Our findings may help to better understand plant nutrient dynamics and element balance in a changing world.