养分添加对退化草地豆科植物草木犀功能性状的影响

Effects of nutrient addition on the functional traits of Melilotus officinalis growing in a degraded grassland

养分亏缺是造成草地生态系统退化的重要因素,养分添加被认为是促进退化草地恢复的重要手段。豆科植物作为草地生态系统的重要功能种群,其对养分添加的响应尚不清楚。该研究选取典型豆科植物草木犀(Melilotus officinalis)为研究对象,在浑善达克沙地开展了鸡粪添加(L0–L6分别为0、500、1000、1500、2000、2500和3000 kg·hm–2·a–1)控制实验,探究了养分添加对豆科植物功能性状的影响。鸡粪添加对草木犀的叶片氮(N)含量、磷(P)含量、钾(K)含量、最大净光合速率(Pnmax)、水分利用效率(WUE)、株高(H)和比叶面积(SLA)均有显著影响。随鸡粪添加量的升高,草木犀叶片N、P、K含量均线性升高,当添加量达到3000 kg·hm–2·a–1(L6)时,N、P、K含量升高幅度分别达到15%、67%和25%;草木犀的H、SLA、Pnmax和WUE先上升后下降,转折点出现在鸡粪添加量为1500 kg·hm–2·a–1(L3)时,以8月份为例,L3较L0的升高幅度分别达到51%、18%、12%和38%,而L6与L0则无显著差异。因此,适量的鸡粪添加能显著提高豆科植物的光合能力和水分利用能力,改善其生长状况,有利于豆科植物种群的维持。

Aims Nutrient deficiency is one of the important factors that cause grassland ecosystem degradation.Nutrient addition was regarded as an effective method to restore the degraded grassland.Legumes,an important component of grassland ecosystems,would be significantly affected nutrient addition.This study aims to clarify the effects of nutrient addition on the functional traits of legumes.Methods We carried out a nutrient addition experiment in Onqin Daga Sandy Land,in which different amount of chicken manure(CMA,L0–L6 were 0,500,1000,1500,2000,2500 and 3000 kg·hm–2·a–1)was used as the nutrients.Then we explored the effects of nutrient addition on Melilotus officinalis,a typical legume plant.Important findings The results showed that the leaf nitrogen(N),phosphorus(P),potassium(K)content,maximum photosynthetic rate(Pnmax),water use efficiency(WUE),specific leaf area(SLA)and plant height(H)of M.officinalis were significantly affected by CMA.Leaf N,P and K content of M.officinalis increased linearly with the increase of CMA.When CMA amount arrived at 3000 kg·hm–2·a–1(L6),the leaf N,P,and K content of M.officinalis increased by 15%,67%and 25%respectively compared with L0.CMA also influenced H,SLA,Pnmax and WUE of M.officinalis,and the responses of these functional traits to CMA was hump shaped.When CMA amount was lower than 1500 kg·hm–2·a–1(L3),H,SLA,Pnmax and WUE of M.officinalis in August increased significantly by 51%,18%,12%and 38%respectively;when CMA amount was higher than1500 kg·hm–2·a–1 they all decreased significantly.There was no significant difference in the values of H,SLA,Pnmax and WUE between L6 and L0.CMA in an appropriate amount could improve the photosynthetic capacity and water use capacity of legumes growing in grassland,and then promote their growth,ultimately improve the maintenance of their population.