塔里木盆地濒危物种灰叶胡杨克隆生长的生态适应机制

Tarim basin is the only distribution of endangered species Populus pruinosa Schrenk in China. The natural forest seeding regeneration of Populus pruinosa Schrenk is restricted by the extreme lack of surface water resource, so the clonal growth becomes the main way of keeping its population regeneration and development. However, under natural conditions, the ecological adaptation mechanism of keeping its population regeneration and development in responding to habitat heterogeneity is still unclear. This study, from the level of genet and genet population, is to explore its clonal organ growth and expansion, adventitious shoots development, clonal rame formation and the relationship of dynamic growth pattern and habitat resources of genet population clonal growth in different temporal-spatial scales. It is hoped to explain the plasticity reaction of habitat heterogeneity resources utilization of horizontal lateral root level distribution pattern, the resources regulatory mechanism of the carbonitride, plant endogenous hormones and soil moisture and nutrients of horizontal lateral root for adventitious shoots growth and clonal ramet development, and the temporal-spatial dynamic characteristics of growth pattern and clonal architecture of genet population in response to habitat heterogeneity resources, plasticity size and direction, and scientifically reveal the mechanism of ecological adaptation of the clonal growth of Populus pruinosa Schrenk. The research outputs will provide scientific basis for drawing up measures of natural forest clonal regeneration of Populus pruinosa Schrenk, it is of important theoretical and practical significance for ecological safety construction of Tarim basin.

塔里木盆地是濒危物种灰叶胡杨在中国的唯一分布区。灰叶胡杨天然林种子繁殖更新受到盆地地表水资源缺乏的制约，所以克隆生长成为它维持种群更新发展的主要繁殖方式。但在自然条件下，灰叶胡杨克隆生长如何响应生境异质性资源来维持种群更新发展的生态适应机制尚不清楚。本研究拟从基株和基株种群的水平，研究不同时空尺度下灰叶胡杨克隆器官生长拓展、不定芽发生、克隆分株形成以及基株种群克隆生长格局动态与生境资源的关系。以期阐明灰叶胡杨横走侧根水平生长拓展对生境异质性资源利用的可塑性反应；横走侧根碳氮化合物、内源激素及土壤水分和养分对不定芽发生和克隆分株形成的资源调节机制；以及基株种群克隆生长格局和克隆构型对生境异质性资源响应的时空动态特征、可塑性大小与方向，科学地揭示灰叶胡杨克隆生长的生态适应机制。研究成果将为制定灰叶胡杨天然林克隆繁殖更新措施提供科学依据，对塔里木盆地生态安全建设具有重要的理论指导和实践意义。

灰杨克隆生长在天然林种群更新中扮演着重要角色。为阐明灰杨克隆繁殖特征及其与环境因子的关系，沿垂直塔里木河道的方向在两个不同的微生境设置样方，研究灰杨不定芽、未出土和出土克隆分株数量格局动态，以及克隆分株种群的数量和空间分布格局及其影响因子。结果表明：. 1、不定芽、未出土和出土分株在10-30cm土层的横走侧根上数量最多，它们具有围绕已有克隆分株50cm根段范围集中发生的数量格局特征。林缘、林内均表现出不定芽、未出土/出土分株和每丛分株数及分株高和基径生长速率在洪水漫溢前的4月-6月逐渐增加，在洪水漫溢后的8月-10月则逐渐降低。不定芽通过向未出土分株转化率的高低调节分株种群密度及每丛分株数量。. 2、在８种不同取样尺度（５ｍ×５ｍ、５ｍ×１０ｍ、５ｍ×１５ｍ、１０ｍ×１０ｍ、１０ｍ×１５ｍ、１５ｍ×１５ｍ、１５ｍ×２０ｍ、２０ｍ×２０ｍ）下，３个研究区的克隆分株种群空间分布格局均表现为集群分布；在５ｍ×５ｍ取样尺度下，2个不同生境的克隆分株种群在4-10月的空间分布格局均表现为集群分布。克隆分株种群数量和空间分布格局的变化会受到一些土壤理化指标的影响，且在洪水漫溢前后影响不同。. 3、不定芽和出土克隆分株数在4-7月与土壤水分含量呈极显著正相关，不定芽数在8-10月与地表温度、气温呈极显著/显著正相关，未出土克隆分株数则与土壤水分含量呈极显著正相关。土壤含水量、田间持水量和土壤孔隙度、土壤容重以及土壤有机质和碱解氮含量、土壤速效磷、速效钾、全盐含量和PH值对不定芽、未出土/出土分株和每丛分株数以及分株高和基茎生长速率有不同的促进或抑制作用。不定芽、未出土分株和出土分株数与横走侧根可溶性糖含量呈极显著/显著负相关，与全氮、全钾、全磷含量存在显著正相关，但可溶性糖、全氮、全钾及全磷含量对不定芽、未出土分株和出土分株数量的影响在同一年份的不同生境以及同一生境的不同年份有所不同。