峨眉冷杉幼苗叶片功能特征及其N、P化学计量比对模拟大气氮沉降的响应

通过人工施氮模拟大气氮沉降,研究了施氮对峨眉冷杉(Abies fabiri)幼苗叶片功能特征、氮和磷含量及其化学计量比的影响,以及幼苗对氮素的积累效应。结果表明:经过2个生长季节的施氮处理(2009年和2010年,N2)幼苗的总生物量、叶干重、叶重比、叶片氮和磷含量及其N:P分别高于对照处理11.29%、46.70%、41.40%、37.30%、22.33%和6.43%,而比叶面积则降低了6.61%,其中叶干重、叶重比和叶片氮含量与对照处理差异显著(P<0.05),N:P差异极显著(P<0.01),并且叶干重与叶片氮含量具有较强的线性相关;与经1个生长季节施氮处理(2009年,N1)的幼苗总生物量、叶干重、叶重比、比叶面积、叶片氮和磷含量及其N:P的比较分析表明,除叶重比和比叶面积外,其他指标N2均高于N1;人工施氮显著促进了幼苗叶片的生长,提高了叶片氮、磷含量及其N:P,但也反映幼苗生长仍受氮素限制,同时,峨眉冷杉幼苗具有氮素积累效应。

Responses of leaf functional traits and nitrogen and phosphorus stoichiometry in Abies fabiri seedlings in Gongga Mountain to simulated nitrogen deposition

Abies fabiri is one of the dominant conifers in the subalpine area of western Sichuan Province,Southwest China.Taking A.fabiri seedlings as test materials,this paper studied their leaf functional traits and N and P stoichiometry under effects of simulated nitrogen deposition.To simulate nitrogen deposition,ammonium nitrate solution(50 kg N·hm-2·a-1) was weekly sprayed over the growth season(from May to October) of 2009 and 2010.After the two growth seasons,the total biomass,leaf dry weigh,leaf mass ratio,leaf N and P concentrations,and leaf N:P ratio of the seedlings under ammonium nitrate spraying increased by 11.29%,46.70%,41.40%,37.30%,22.33% and 6.43%,respectively,while specific leaf area(SLA) decreased by 6.61%,as compared with the control.There existed significant differences in the leaf dry weigh,leaf mass ratio,leaf N concentration,and leaf N:P ratio between ammonium nitrate spraying and the control,and the leaf dry weight had a strong linear correlation with leaf N concentration.The total biomass,leaf dry weight,leaf N and P concentrations,and leaf N:P ratio of seedlings under ammonium nitrate spraying were higher in the second growth season than in the first growth season.This study demonstrated that nitrogen deposition promoted the leaf growth of A.fabiri seedlings significantly,and increased the leaf N and P concentrations and leaf N:P ratio.However,the variation of leaf N:P ratio under nitrogen supply suggested that the seedling growth was still limited by the shortage of N supply.It was suggested that A.fabiri seedlings had cumulative effect for N.