生长型分类方案不同导致森林生态系统植物功能性状的统计偏差

将植物划分为不同的生长型来统计植物功能性状特征,是当前植物性状研究中常用的方法;但生长型分类方案的不同很可能造成植物功能性状统计分析的偏差,对此偏差的评估却尚未见报道。根据植物志描述及野外调查实际情况,将生长型划分为3种不同的分类方案：分类1：根据植物志信息划分为传统意义的乔木和灌木;分类2：根据树高和胸径划分乔木、小乔木和灌木;分类3：仅根据树高划分乔木层与灌木层的乔木和灌木。以东部亚热带常绿阔叶林区域的浙江金华北山35种优势阔叶木本植物的枝叶性状为研究对象,比较不同生长型分类对植物枝叶性状统计数据的影响。结果表明：（1）与传统的分类1相比,分类2对乔木植物枝叶性状影响的显著程度要高于分类3,而对灌木植物枝叶性状的影响程度低于分类3;但不同生长型分类方案中乔木和灌木的枝叶性状总体差异不显著。而与分类2小乔木相比,分类1以及分类2内部的乔木和灌木生长型的性状与分类2小乔木差异非常明显;（2）将不同生长型植物再划分为不同生活型后,不同生长型分类方案对性状统计的影响增大。无论是常绿还是落叶生活型的小乔木,其与不同生活型乔木和灌木的性状差异仍然显著。可见,不同的生长型分类方案可造成植物功能性状统计的差异;把小乔木植物这一功能类群划分出来,能更好地反映森林生态系统性状特征的差异性。

Statistical bias of plant functional traits in forest ecosystems caused by different classifications of growth form

In current research of plant functional traits, classifying plants into different growth forms to statistically analyze features of plant functional traits is a common approach. Different classifications of growth form, however, may lead to statistical bias of plant trait values, and such bias has not been evaluated. In this paper we investigate how different classifications of growth form influence the calculation of plant functional traits. We classified the growth form of 35 dominant woody plants in eastern subtropical evergreen broadleaved forest region in Beishan Mountain of Jinhua, Zhejiang Province into three schemes according to the Flora of China and actual situation in filed investigation: the classification 1, traditional tree and shrub described in the floras; classification 2, trees, small trees and shrubs based on height and diameter in breast height; and classification 3, trees and shrubs of tree layer and shrub layer according to height only. The statistical bias of plant leaf and twig traits under three classifications of growth form was analyzed and compared. The results showed that: (1) compared with the traditional classification 1, classification 2 had a significant influence on twig and leaf traits of trees than classification 3, while the influence on twig and leaf traits of shrubs was lower than classification 3. However, there was no significant difference of tree and shrub traits in different growth classification schemes. Compared with small trees in classification 2, leaf and twig traits of trees and shrubs in classification 1 and even within the classification 2 were significantly different to those of small trees in classification 2; (2) After subdividing different growth forms into different life forms, the impact of different growth form classification schemes on trait statistics increased. However, leaf and twig traits of both evergreen and deciduous small trees were still significantly different from those of trees and shrubs in different life forms. In general, different classification schemes of plant growth forms can result in the statistical bias of plant functional traits. Separating the small tree from the tree and shrub functional groups could better reflect the differences of plant functional traits in forest ecosystems.