为研究克隆植物在不同生境中对小生境的利用能力和对不同尺度异质性生境的等级可塑性及其格局差异,比较了林缘和荒草坡不同草本层盖度小生境中积雪草(Centella asiatica)分株种群、克隆片段和叶水平的形态和生理特征。在分株种群水平,林缘和荒草坡积雪草被测的分株种群特征差异均不显著,不同草本层盖度小生境间积雪草根冠比差异显著,即在盖度小的小生境中其根冠比显著大于盖度大的小生境。在克隆片段水平,林缘和荒草坡生境显著影响积雪草的根干重、花果干重、一级匍匐茎节间长和总匍匐茎节间长,而不同草本层盖度小生境则显著影响花果干重、根冠比、一级匍匐茎数、二级匍匐茎节间长和总匍匐茎节间长。荒草坡积雪草拥有更大的根干重和花果干重,但一级匍匐茎节间长和总匍匐茎节间长较短。草本层盖度小的小生境中积雪草的根冠比和一级匍匐茎数显著高于盖度大的小生境,而花果干重、二级匍匐茎节间长和总匍匐茎节间长则相反。在叶水平,荒草坡和草本层盖度大的小生境中,积雪草的叶片长、叶片宽和叶面积都较大,而草本层盖度大的小生境中积雪草叶柄长和比叶柄长都显著大于盖度小的小生境;林缘和荒草坡生境与不同草本层盖度小生境对4个叶绿素指标影响均不显著,林缘和荒草坡生境与不同草本层盖度小生境的交互作用对所有测量特征均无显著影响。上述结果表明,积雪草对不同生境和有草本层盖度差异的小生境的反应存在等级可塑性,但是二者的等级差异格局不同;等级反应格局的差异反映出积雪草对不同生境条件有不同的生态适应对策,且对生境小尺度异质性的可塑性强于对大尺度异质性的可塑性。

Aims In natural environments, resources of critical importance to plant growth are patchily distributed, even at a small spatial scale. The aims of this study are to address: 1) Centella asiatica exploitation of heterogeneous microsites in different habitats, 2) hierarchical effects of habitats and microsites with different herbaceous coverage on growth traits of C. asiatica, and 3) differences in hierarchical response patterns for large and small scales of heterogeneous habitats.
Methods Microsites with low and high herbaceous coverage were selected in abandoned grassland slope and forest edge habitats. We measured morphological and physiological characteristics of C. asiatica in spring 2004 and 2005 at three levels: ramet population, clonal fragment and leaf. Environmental factors of different microsites were investigated again in September 2006.
Important findings At the ramet population level, we observed no effect of habitat (forest edge vs. abandoned grassland slope). Root-shoot ratio of ramet population with low herbaceous coverage was significantly higher than that with high herbaceous coverage. At the level of clonal fragment, root dry weight, flower and fruit dry weight were significantly higher and internode length of primary and total stolons were shorter on abandoned grassland slope. Root-shoot ratio and number of primary stolons were significantly larger with low herbaceous coverage, but flower and fruit dry weight, internode length of secondary stolon and internode length of total stolon were lower. At the leaf level, lamina length, lamina width and lamina area were larger on abandoned grassland slope and with high herbaceous coverage. Plants with high herbaceous coverage had larger petiole length and specific petiole length. No significant effects of habitat and microsite on chlorophyll content were observed. These findings indicated that there were hierarchical effects of habitat and microsite on the growth traits of C. asiatica, and different hierarchical responses of C. asiatica to different habitats and microsites with different herbaceous coverage were observed. Plastic response to heterogeneous habitat is stronger at smaller scale than that at larger scale.