漓江流域不同弃耕年限下4种常见草本植物功能性状种内变化及其影响因素

Intraspecific variations in plant functional traits of four common herbaceous species under different abandoned years and their relevant driving factors in Lijiang River Basin,China

为探究不同弃耕年限下植物功能性状的种内变化及其影响因素,加深对弃耕地植被恢复演替过程的认识,该研究聚焦于漓江流域桂林市临桂区几个村庄的农田边界、弃耕草地、灌草丛和林地4种一定程度上反映弃耕地植被恢复程度的生境,以分布较广的草本植物,即白茅(Imperata cylindrica)、双穗雀稗(Paspalum distichum)、鬼针草(Bidens pilosa)和喜旱莲子草(Alternanthera philoxeroides)为研究对象,研究不同弃耕年限下其比叶质量、叶干物质含量、叶片氮含量、叶片磷含量和植株高度5个功能性状的种内变化,并阐明土壤氮含量、磷含量、pH和木本植物盖度对其的影响。主要发现如下:随弃耕年限增加,样地土壤氮、磷含量显著下降,土壤氮磷比先增加后下降,木本植物盖度显著增加。白茅叶片氮含量随弃耕年限增加而增加,叶片磷含量随弃耕年限增加而下降,这是由于叶片氮含量与土壤磷含量呈负相关关系,叶片磷含量与土壤磷含量呈正相关关系。双穗雀稗比叶质量和叶干物质含量随弃耕年限增加而增加,植株高度随弃耕年限增加而降低。鬼针草植株高度随弃耕年限增加而降低,这是由于其植株高度随木本植物盖度增加而显著下降。喜旱莲子草比叶质量随弃耕年限增加而下降,这是由于喜旱莲子草比叶质量与土壤氮磷比呈正相关关系。总之,植物功能性状的种内变化是由土壤理化性质和木本植物盖度随弃耕年限变化造成的。

Aims Exploring intraspecific variations of plant functional traits with abandoned years and the relevant driving factors will deepen our understanding about the vegetation recovery of abandoned lands and thus guide our agricultural management.Methods Using the method of substitution of space for time,we set up 42 plots in four types of habitat,i.e.,field margin,abandoned grassland,shrub-grassland and forest which represents community succession along a chronosequence of vegetation restoration in Sitang town,Lingui District of Guilin in the middle reaches of Lijiang River watershed.We investigated change of intraspecific variation of five functional traits(i.e.,leaf mass per area,leaf dry matter content,leaf nitrogen(N)content,leaf phosphorus(P)content and plant height)for four common herbaceous species(Imperata cylindrica,Paspalum distichum,Bidens pilosa and Alternanthera philoxeroides)with abandoned years.We also investigated the effects of soil properties and woody plant coverage on the intraspecific variation of functional traits.Important findings With the increase of abandoned years,soil N and P content decreased significantly,soil N:P increased first and then decreased,and the woody plant coverage increased significantly.Leaf N content of I.cylindrica increased significantly,while leaf P content decreased significantly with the increase of abandoned years.This is because leaf N content decreased significantly and leaf P content increased significantly with the increase of soil P content.Leaf mass per area and leaf dry matter content of P.distichum increased significantly and plant height decreased significantly with the increase of abandoned years.Plant height of B.pilosa decreased significantly with the increase of abandoned years,because plant height of B.pilosa decreased significantly with the increase of woody plant coverage.Leaf mass per area of A.philoxeroides decreased significantly with the increase of abandoned years,because leaf mass per area of A.philoxeroides increased significantly with the increase of soil N:P.In sum,the intraspecific changes of plant functional traits are caused by the changes of soil physical and chemical properties and woody plant coverage with abandoned years.