常绿阔叶林植物叶片N、P化学计量特征对毛竹扩张的响应

为从生态化学计量内平衡角度解释常绿阔叶林不同层次植物对毛竹(Phyllostachys edulis)扩张的生存响应差异性,该研究采用空间代替时间的方法,在江西井冈山国家级自然保护区沿毛竹扩张方向选取典型毛竹-常绿阔叶林界面,依次设置毛竹林、竹阔混交林和常绿阔叶林样地,比较分析了毛竹扩张方向上样地内不同乔木层、灌木层、草本层植物叶片及土壤N、P含量及比例。结果表明:(1)从毛竹林到阔叶林,土壤N含量上升,P含量下降,N:P上升(P<0.05); 乔木层树种 [红楠(Machilus thunbergii)、赤杨叶(Alniphyllum fortunei)及交让木(Daphniphyllum macropodum)]叶片P含量下降,N:P上升(P<0.05); 除灌木层的红果山胡椒(Lindera erythrocarpa)外,各林分中的灌木层和草本层植物N、P含量及比例变化较小。(2)土壤N:P与乔木层、草本层和灌木层植物叶片N:P分布呈显著正相关、负相关与不相关。(3)在各林分中,毛竹叶片N、P含量及比例较稳定。综上认为,毛竹通过改变土壤N、P化学计量特征进行扩张,引起植物体N、P元素化学计量特征发生变化。灌木及草本植物受土壤异质性影响较小,但是乔木层植物N、P元素化学计量特征却因此失衡,这可能是阔叶林乔木层树种存亡受威胁的重要原因。

Response of N and P stoichiometric characteristics of evergreen broad-leaved forest plant leaf to Phyllostachys edulis expansion

In order to explain the difference of survival response of plants at different levels in evergreen broad-leaved forest to the Phyllostachys edulis expansion from the perspective of ecological stoichiometry homeostasis, this study used the method of space-time substitution, a typical P. edulis evergreen broad-leaved forest interface including P. edulis forest, P. edulis broad-leaved mixed forest and evergreen broad-leaved forest was selected in Jinggangshan National Nature Reserve, Jiangxi Province. The N and P contents of soil and leaves of P. edulis, broad-leaved trees, shrubs and herbaceous layer plants in each forest were compared and analyzed. The results were as follows:(1)From bamboo forest to evergreen broad-leaved forest, the soil N content and N:P increased, while soil P content decreased; the leaf P contents of tree species(Machilus thunbergii, Alniphyllum fortunei and Daphniphyllum macropodum)decreased and the N:P increased. Unlike the trees, the leaf N and P stoichiometric characteristics of plants both in shrub and herbaceous layers showed no significant change, except the shrub tree Lindera erythrocarpa.(2)The soil N:P was positively correlated with the leaf N:P of trees, negatively correlated with that of shrubs and had no correlation with that of herbaceous plants, respectively.(3)The leaf N and P contents and N:P for P. edulis remained stable. In conclusion, P. edulis expansion changes plant leaf N and P stoichiometric characteristics by altering the soil N and P stoichiometric characteristics. Shrubs and herbaceous plants are less affected, however, it causes the imbalance of plant N and P stoichiometric characteristics of tree layer plants, which may be an important reason for the survival of tree species in evergreen broad-leaved forest.