鄱阳湖沙山单叶蔓荆(Vitex rotundifolia)叶性状沿沙化梯度变化特征

Leaf Traits of Vitex rotundifolia along Desertification Gradient in a Sandy Hill of the Poyang Lake

在鄱阳湖湖滨沙山沿沙化梯度测定了单叶蔓荆(Vitex rotundifolia)叶面积、比叶面积、叶氮、叶磷等指标,以阐明单叶蔓荆主要叶性状特征,探讨叶性状对沙化程度的响应。结果表明:单叶蔓荆叶面积1.58~13.14cm^2,与湖岸线距离没有显著相关性,不能指示沙化程度对单叶蔓荆的影响。比叶面积81.6~206.3cm^2·g^(-1),种内差异显著(P<0.05);单位质量的叶氮、磷含量分别为16.0~23.2mg·g^(-1)、0.82~2.20mg·g^(-1),种内差异不显著。比叶面积与叶片氮含量显著正相关(P<0.05),与叶片磷含量无显著相关性。比叶面积对沙化梯度响应敏感,随沙化程度的增加而降低;叶片氮、磷含量及其化学计量比值对沙化程度的变化不敏感,保持了相对稳定性。依据叶片氮磷比值判断,单叶蔓荆在沙山生境中更多地受磷的限制。

There are some sandy hills distributed along Poyang Lake,which belong to typical southern desertification.As located in subtropical climate zone,the sandy hills differed in vegetation and soil from northern deserts.In this study,leaves of Vitex rotundifolia were sampled along desertification intensity gradient in Duobao sandy hill,Poyang Lake.Subsequently,leaf area,specific leaf area(SLA),leaf nitrogen(N)and phosphorus(P)were measured.The objective of this study was to clarify the intraspecific variation in leaf traits and the responses to desertification intensity variation.Results indicated that leaf area of V.rotundifolia ranged from1.58 to 13.14 cm^2.No significant correlation was found between leaf area and the distance away from lakeshore line.Thus,leaf area could not indicate the effects of desertification intensity on V.rotundifolia.SLA varied from81.6 to 206.3 cm^2·g^(-1).SLA showed significant intraspecific difference(P<0.05).Leaf N ranged from16.0 to 23.2 mg·g^(-1),whereas leaf P varied from0.82 to 2.20 mg·g^(-1).Both leaf N and P showed no significant intraspecific difference.SLA was significantly positively correlated with leaf N,but not with leaf P.SLA was very sensitive to desertification intensity variation,and decreased with the increase of desertification.However,leaf N and P,as well as N∶P stoichiometry were not sensitive to the desertification variation,and maintained relatively stable.According to the ratio of leaf N∶P,V.rotundifolia was more limited by phosphorus,rather than nitrogen.