不同水分下准噶尔无叶豆分株种群特征和生物量分配差异

准噶尔无叶豆是豆科无叶豆属小半灌木,在中国仅片断化分布于新疆古尔班通古特沙漠局部区域.该种自然种群种子萌发率极低(<3%),主要靠克隆繁殖维持种群.为研究克隆生长在异质性生境中的可塑性特征及其生态适应意义,对生境土壤含水量存在差异的两个准噶尔无叶豆自然种群(河边种群,沙漠种群)的分株种群特征、生物量及其分配比重进行了比较,研究发现:①在分株种群特征上,河边种群的分株显著高于沙漠种群,分株间距也显著大于沙漠种群.沙漠种群分株密度和根的密度显著大于河边种群,但每一分株拥有根的概率显著小于河边种群;②在生物量分配方面,河边种群具有比沙漠种群大的根生物量,但根茎生物量则要显著的小于沙漠种群;③在植株各部分生物量比重随植株大小的变化趋势上,河边种群各部分的比重随植株大小变化的趋势平缓,而沙漠种群各部分的比重变化趋势则较为急剧,表明河边准噶尔无叶豆分株种群随着植株的大小变化,资源分配比例并没有发生很明显的变化,而沙漠种群变化较大.结果表明,准噶尔无叶豆种群对所处生境水分条件存在可塑性响应,并通过分株种群特征变化和生物量分配差异应对水分条件的变化,形成自身的适应对策.

Ramet population characteristics and biomass allocation of Eremosparton songoricum growing under different water conditions

Eremosparton songoricum is a dwarf shrub found in mobile or semi-fixed sand dunes of central Asia. The germination of E. songoricum seeds in the natural populations is less than 3%, thus clonal propagation seems to be particularly important. Understanding clonal growth characteristics of E. songoricum is potentially helpful for vegetation restoration and conservation efforts. In this paper, two natural populations in the Gurbantuggut Desert of Xinjiang, China, one located along a riverside (GPS location: 46°31.09′N, 88°33.06′E, sand dune slope 15°) and another located in the desert hinterland (GPS location: 46°28.07′N, 088°33.07′E, sand dune slope 30°), were investigated in late June of 2007. Height and density of ramets were investigated within three 4m 4m sites in the two populations. Biomass of above and underground (0-60cm) of ramets was measured and the proportions of biomass in each plant part (foliage, flower, adventitious roots (rhizomes) and vertical roots) were calculated in one of three sites. The results were as follows:①Ramet density and adventitious root density were significantly higher, but ramet height and distance between individuals were significantly lower in the desert population than those in the riverside population.②The biomass of adventitious roots (rhizomes) was significantly lower and the biomass of vertical roots was significantly higher in the desert population compared to the riverside population.③The change in proportion of biomass in each plant part with increasing plant biomass were more dramatic in the desert population than in the riverside population, suggesting different resource allocation strategies with increasing plant biomass for the two populations. These findings indicate that the clonal growth of ramet populations of E. songoricum have greater morphological plasticity under different water conditions, which are attributed to survival in the arid and stressful sand dune environment.