准噶尔荒漠梭梭幼苗应对干旱的养分吸收分配策略对种群更新的影响

The Gurbantunggut desert in Junggar Basin in Xinjiang is a typical arid desert ecosystem in China, and is also the most widely distributed area of the desert plant Haloxylon. According to the current problem that heavy degradation of natural Haloxylon ammodendron and low survival rate of new seedlings in Junggar desert. In the most vulnerable phase of Haloxylon's life history, this study uses natural regeneration seedlings as research materials, based on the theory and methods of plant restoration ecology, plant nutrition, soil science, and forestry Science, combined with field monitoring and laboratory regulation experiment, using laboratory analysis and plant nutrition diagnostics principles, we will analyze the characteristics of seasonal changes of soil moisture and nutrients in the microhabitat of seedling root zone, find the nutrient uptake and distribution characteristics during seedling growth period, research on nutrient absorption, distribution and response of seedlings under drought stress. Furthermore, we will establish the relationship between nutrient uptake and distribution ratio and seedling survival rate and productivity under different drought conditions. Then, we will get the effects of nutrient uptake and distribution on the survival and growth of seedlings under drought stress. Eventually, we will reveal its impact on regional population renewal and understanding the survival adaptation strategies of H.ammodendron seedlings under extreme drought stress timely. The results of the study are of great significance in promoting the self-renewal and ecological restoration of the H.ammodendron population. All these research would provide management theory and technical basis for ecological conservation and vegetation restoration along the Silk Road Economic Belt.

新疆准噶尔盆地古尔班通古特沙漠为我国典型的干旱区荒漠生态系统，同时也是荒漠植物梭梭分布面积最广的区域，针对目前准噶尔荒漠天然梭梭林存在严重退化和更新苗存活率低的问题. 以梭梭生活史中最脆弱阶段的更新苗为研究材料，以植物恢复生态学、植物营养学、土壤学和林学的理论为依托，采用野外监测与室内调控相结合的方法，利用土壤农化分析和植物营养诊断技术，通过对更新苗根区微生境土壤水分、养分的季节变化特征及其相互影响关系、更新苗生长期的养分吸收分配特性和干旱胁迫下幼苗的养分吸收分配策略及其响应等方面的深入研究，建立不同干旱条件下幼苗的养分吸收分配比率与存活率、生产力间的关系模型，明确其对梭梭幼苗存活与生长的影响，进而揭示对区域种群更新的影响，及时掌握梭梭幼苗在极端干旱逆境下的生存适应策略，对促进退化梭梭种群的自我更新、生态恢复具有重要意义，为做好丝绸之路经济带沿线的生态保育与植被恢复工作提供理论资料。

梭梭是准噶尔盆地荒漠区的主要建群种，在维护该区域生态平衡以及生物多样性保护方面起着关键的作用。幼苗的补充与定居能力决定着种群更新和群落稳定，而土壤水分和养分是其自然更新的主要限制因子。采用野外监测和室内控制相结合的方法，以退化梭梭种群中1~3 a生幼苗为研究对象，研究生长期幼苗根区土壤水分、养分的动态特征及其相互影响关系，幼苗生物量、养分吸收与分配格局特征，揭示其适应干旱贫瘠环境的养分吸收分配规律。通过盆栽试验明确幼苗的生长、生理和养分吸收对干旱-复水的响应特征，揭示干旱幼苗维持正常生长的适应对策及抗旱生理提升机制。结果表明：（1）幼苗根区土壤水分和养分含量均在4月时达最大值，8月时达最小值。土壤水平（0~40 cm）空间内，随着水平距离的延伸，土壤水分具有明显的“湿岛”效应，土壤速效养分具有明显的“内低外高”特征。土壤垂直（0~50 cm）空间内，随着土壤深度的增加，土壤水分含量呈先增后减趋势，土壤养分含量呈递减趋势，土壤20~30 cm层水分含量最大，土壤水分对表层有机质、碱解氮和速效钾含量影响程度高（P<0.05）。（2）幼苗萌芽期至同化枝扩展期是植株氮素和磷素养分积累的主要时期，占比达75.80%和85.58%，同化枝扩展期至生长后期为钾素积累的主要时期，占比达55.69%。生长后期各器官中的养分含量从同化枝和茎不断向根中转移，表现出明显的“养分回流”特征。（3）随着干旱时间的延长，株高、冠幅面积、基径和梢长呈先升高后降低趋势，抗氧化酶活性呈不断升高趋势，总叶绿素含量呈不断降低趋势。干旱时间与总叶绿素含间量呈极显著负相关（P<0.01）。（4）随着复水时间的延长，同化枝中可溶性蛋白、可溶性糖、脯氨酸和丙二醛的含量呈不断降低趋势，幼苗同化枝的水分利用率和氮、磷、钾素养分含量与复水时间呈显著正相关（P<0.05）。干旱20 d幼苗的复水效应高于干旱40 d幼苗。从植物养分吸收与分配角度揭示幼苗应对荒漠土壤水分变化的养分吸收分配策略及生理响应机理对种群更新的影响，为梭梭属植物的保育更新提供理论依据。

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