CLONAL GROWTH CHARACTERISTICS OF THYMUS SERPYLLUM VAR.ASIATICUS

Abstract

Aims The relationship between clonal growth and ecological adaptation is a central issue in clonal plant population ecology, but few studies have examined of growth patterns of small half-shrubs. Thymus serpyllum var. asiaticus is a dwarf half-shrub with creeping stems. Soil erosion is a serious problem in the pisha-sandstone area, such as the Huangfuchuan watershed, where T. serpyllum var. asiaticus can form a mono-dominant community and help maintain ecosystem stability. Understanding clonal growth characteristics of T. serpyllum var. asiaticus, therefore, is potentially helpful for vegetation restoration in this area. Methods We sampled T. serpyllum var. asiaticus clones consisting of mother, daughter and granddaughter ramets from May to September 2004 in Huangfuchuan watershed. For each clone, we counted numbers of roots, stems and branches and measured biomass of roots, stems, branches, leaves and flowers. We examined monthly changes in biomass allocation of the different ramets. Important findings Compared with the daughter and granddaughter ramets, the mother ramets of T. serpyllum var. asiaticus were bigger with more complex structure, biomass and number of modules. Mother ramets had largest biomass allocation to roots and much smaller to leaves. For the daughter and granddaughter ramets, biomass allocation to leaves was largest and that to roots was smaller. Differences in biomass allocation patterns between mother and daughter (and granddaughter) ramets may reflect different ramet functions. Mother ramets may be specialized for water and nutrient absorption, while daughter and granddaughter ramets may be specialized for photosynthesis, a phenomenon called `division of labor'. According to changes in biomass allocation to branches, stems and flowers from May to September, the module growth of mother and daughter ramets was similar, but differed from that of granddaughter ramets. Findings may reflect different physiological integrations of ramets.