巴丹吉林沙漠沙鞭斑块植被种群扩张过程及其对风沙环境的响应

The gramineous patch vegetation has strong adaptability and better binding-sand effect in the semi-mobile dune, its expansion processes has potential application value to increase the proportion of semi-mobile dune, and reduce the expansion rate of the desert in the local area. Badian Jaran Desert is the highest moving dune in the world, where the vegetation patches of Psammochloa villosa is the common landscape in the mobile dune. However, we cannot comprehensively understand the formation mechanism, expansion processes and adaptation with the patches of Psammochloa villosa. In addition, it is an open problem that the influence of vegetation development and vegetation patch on the soil water in the Badian Jaran Desert. This study will take the mean annual precipitation is around 100 mm of vegetation patch of Psammochloa villosa in the Badain Jaran Desert as the research object on the basis of field survey for many times. Based on the multiple field investigation, we will carry out researches on the seed bank and bud bank in the Psammochloa villosa plant community, the expansion processes of Psammochloa villosa and its influence factors, the response and laws of expansion processes to the wind-sand activity and its effect on the soil water with field monitoring and control experiments. The study aims to understand the process of formation and evolution about the vegetation patches of gramineous plants in typical dune habitats from the perspective of the expansion processes, revel the effect of plant patch to the soil moisture on the dune, and clear the adaptation thresholds, limiting factors and strategies of patch vegetation expansion processes to the wind erosion and sand burial. It is will contribute to the ecological mechanism and practice of gramineous plant sand-fixation on dune, and provide technical support for sand controlling.

禾本科斑块植被在半流动沙丘中具有较强的适应性和较好的固沙作用，其扩张过程对于局部增加半流动沙丘的比例，减缓沙漠扩张速度具有潜在的应用价值。巴丹吉林沙漠是世界上流动沙丘最高的沙漠，沙鞭植被斑块是流动沙丘上常见的景观，但关于沙鞭斑块的形成机制、扩张过程、适应能力以及植被发育对生境土壤水分状况的影响缺乏系统了解。本项目在多次野外考察的基础上，拟以降水量100mm左右的巴丹吉林沙漠内部沙鞭植被斑块为研究对象，采用野外监测和控制试验相结合的方法，研究沙鞭植被群落种子库和芽库特征、沙鞭种群扩张过程及其影响因素、种群扩张对土壤水分的影响以及对风沙活动的响应规律等，旨在从种群扩张的视角理解典型沙丘生境禾本科植被斑块的形成演化过程，揭示植被斑块对沙丘土壤水分的影响，厘清斑块植被扩张应对风蚀和沙埋的适应阈值、限制因子和策略，丰富禾本科植物固沙的生态学机制与实践，为防沙治沙提供科技支撑。

沙鞭（Psammochloa villosa）是典型的旱生、沙生禾本科斑块植物，对流动沙丘具有很强的适应性，可以通过分蘖和根茎繁殖方式使其在适应异质性强且水分匮乏环境中具有独特优势。研究沙鞭的形成与扩张在一定程度上对流沙斑块的固定、增加沙漠中半流动沙丘的比例、减缓沙漠扩张速度等方面具有潜在的应用价值。本项目研究了风沙环境下沙鞭种群的更新规律和扩张过程，厘清了植物种群扩张应对沙埋、坡位和斑块属性的阈值，及植被拓展关键性制约因子和适应策略。主要结论有：.（1）明确了不同景观类型的沙鞭群落特征。在89—395mm的降水范围内，物种丰富度随降水量增大而增加，植被类型从“一年生草本植物”，转变为“一年生草本和多年生草本混生”，直至“灌木、多年生草本和一年生草本组合”的植被类型。.（2）明晰了沙鞭空间格局的尺度转变特征规律，揭示出聚集分布是沙鞭种群在干旱风沙环境下的主要格局类型，斑块状分布和种内种间竞争可能是沙鞭种群空间格局转变的关键。.（3）沙鞭株丛高度存在显著的季节变化规律。返青期和开花期光合作用产物向地上器官分配“促进茎干伸长”，结实期转变为“以穗粒发育为主要表现的有性繁殖”，生长季末期不再向“已完成有性繁殖功能的株丛”进行资源投入。.（4）沙鞭种群层面叶片面积与叶片数量遵循Corner法则延伸出的“叶片大小与叶片数量一般负相关”规律，揭示出“淘汰老旧叶片、增加新生叶片，提高内部运行效率”的自然选择结果的可塑性策略。.（5）沙鞭地下根茎拓展对温度、沙埋深度和斑块大小响应敏感程度。3月中旬至12月中旬是沙鞭根茎拓展季，12月中旬至次年3月中旬是休眠季；沙鞭根茎拓展速率阈值为0.146—0.8 cm/天，高温和低温都会抑制沙鞭地下根茎生长甚至于停止生长；沙埋深度过浅或者过深均会影响根茎拓展速率，且中等大小斑块根茎拓展速率高于其它斑块，反映了沙鞭对于不同生境因子的响应和适应策略。