C:N:P stoichiometry of Ericaceae species in shrubland biomes across Southern China:influences of climate,soil and species identity

Aims Carbon(C),nitrogen(N)and phosphorus(P)stoichiometry strongly affect functions and nutrient cycling within ecosystems.However,the related researches in shrubs were very limited.In this study,we aimed to inves-tigate leaf stoichiometry and its driving factors in shrubs,and whether stoichiometry significantly differs among closely related species.Methods We analyzed leaf C,N and P concentrations and their ratios in 32 species of Ericaceae from 161 sites across southern China.We examined the relationships of leaf stoichiometry with environmen-tal variables using linear regressions,and quantified the interactive and independent effects of climate,soil and species on foliar stoi-chiometry using general linear models(GLM).Important Findings The foliar C,N and P contents of Ericaceae were 484.66,14.44 and 1.06 mg g−1,respectively.Leaf C,N and P concentrations and their ratios in Ericaceae were significantly related with latitude and altitude,except the N:P insignificantly correlated with latitude.Climate(mean annual temperature and precipitation)and soil properties(soil C,N and P and bulk density)were significantly influenced element stoichiom-etry.The GLM analysis showed that soil exerted a greater direct effect on leaf stoichiometry than climate did,and climate affected leaf traits mainly via indirect ways.Further,soil properties had stronger influ-ences on leaf P than on leaf C and N.Among all independent factors examined,we found species accounted for the largest proportion of the variation in foliar stoichiometry.These results suggest that species can largely influence foliar stoichiometry,even at a lower taxonomic level.

青藏高原高寒草原植物群落对降雨的响应依赖于优势种的功能性状

人类活动和全球变化引起了全球和区域降雨格局的改变。大量的研究表明,降雨影响全球不同草地生态系统的群落组成,但目前很少有研究从物种水平揭示高寒草原植物群落如何响应降雨变化的生态学过程。本研究利用在青藏高原建立的长期(6年)控雨试验平台,包括减少降雨50%、增加降雨50%和对照3个处理,从优势种地上和地下性状揭示高寒草原植物群落响应降雨变化的生态学过程。研究结果表明,长期减少降雨改变了植物群落的结构,主要体现在优势种丛生禾草紫花针茅(Stipa purpurea)逐渐被根茎禾草赖草(Leymus secalinus)所取代。进一步通过比较紫花针茅和赖草的地上和地下性状,发现减少降雨主要促进了赖草根系向深土层的生长、增加了地下碳的分配和减少了叶片宽度,而紫花针茅的这些性状并没有发生显著的改变;另外,减少降雨增加了赖草根茎生物量、总长度、直径及其节上根的数目。赖草这些性状的改变可能增加了对深土层水分的利用能力,以及减少了水分的蒸腾,从而增强了其在干旱胁迫过程中的竞争力。因此,我们的研究结果强调了优势种的地上和地下性状在高寒草原植物群落组成对降雨变化响应过程中起着极其重要的作用。