沙丘坡面异质性小生境中准噶尔无叶豆对水分条件变化的响应

以多年生克隆植物准噶尔无叶豆(Eremosparton songoricum(Litv.)Vass.)为材料,选择河边(A种群)和沙漠腹地(B种群)两个沙丘,研究从沙丘底部至顶部,沿着水分条件连续变化的梯度,准噶尔无叶豆在分株种群和克隆片段水平的形态变化特征,以期能揭示其在异质性小生境内利用水分资源的对策,并为准噶尔无叶豆的资源保护、培育和利用提供有意义的参考.研究发现:①在分株种群水平,A种群分株高度及地上部生物量显著高于B种群,而B种群地下部(根)的生物量则显著高于A种群;②在克隆片段水平,随着沙丘底部至顶部,A种群与B种群克隆片段高度和地上生物量都减小,而分株密度都增加,但升高或降低的强度不同;A种群根的生物量和长度增加,主要是水平的位于地下0～10 cm层面的直径10mm以下的根长度增加,而B种群根的生物量减小,但长度却在增加,主要是水平的位于地下0～10 cm层面的直径6mm以下的细根长度增加.水平细根的长度增加,更利于无性系进行广泛觅食,同时促进无性系尽快越过不利生境斑块和提高分株在有利生境中的生长概率.结果表明,准噶尔无叶豆对沙丘坡面水分条件连续变化的异质性小生境存在分株种群及克隆片段两个等级的可塑性响应,并通过可塑性变化适应了沙丘坡面水分条件的分异.

The morphological plasticity of Eremosparton songoricum along heterogeneous micro-habitats of continuous moisture gradient changes in sand dunes

Eremosparton songoricum is a dwarf shrub surviving in mobile or semi-fixed sand dunes of central Asia desert. In order to detect the response of E. songoricum to micro-habitat heterogeneity with continuous moisture gradient changes along sand dunes from bottom to top, the morphological characteristics were measured under ramet population and clonal fragment levels in two populations, one located along a riverside (population A, 46 31.09′N, 88°33.06′E, sand dune slope 15°) and another located in the center of a sand dune area (population B, 46°28.07′N, 088°33.07′E, sand dune slope 30°) in Gurrbantuggut Desert of Xinjiang, China. Height and density of ramets were investigated within twelve 1m×1m sites designed along three transects. Length, rhizome diameter (< 2 mm, 2-4 mm, 4-6 mm, 6-8 mm, 8-10 mm, 10-12 mm, >12mm), and biomass of clonal fragments were measured at 0-10 cm and 10-30 cm belowground. The results were as follows: ①At the ramet population level, the height and aboveground biomass in population A were significantly higher than those in population B, while the underground biomass (including vertical roots and horizontal rhizomes) was significantly lower in population A than population B; ②At the clonal fragment level, with the moisture content continuously reduced from the bottom to top of the sand dunes, the height and aboveground biomass reduced and the density of ramets increased in both populations, but with different intensity. Root biomass increased in population A and reduced in population B. Root length increased in both populations, but the attribution to different portions of the root system was different. At 0-10 cm belowground, population A increased root length mostly via horizontal rhizomes less than 10 mm in diameter, while population B increased mostly via horizontal rhizomes less than 6mm in diameter. The increase of small diameter horizontal rhizomes in upper slopes of sand dunes in both populations has important significance in the aspects of promoting forage behavior of the plants, escaping from adverse environmental patches, and increasing possibility of survivorship. These findings indicate that there is plasticity in response to micro-habitat heterogeneity along the continuous moisture content gradients of sand dunes at the ramet population and clonal fragment levels.