HIERARCHICAL PLASTICITY OF CENTELLA ASIATICA IN RESPONSES TO MICROSITES WITH DIFFERENT HERBACEOUS COVERAGE OF FOREST EDGE AND ABANDONED GRASSLAND SLOPE
林缘和荒草坡不同草本层盖度小生境中积雪草的等级可塑性

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.