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2种沙障对流沙生境与植被恢复的影响

Effect of Two Types Sand Barriers on Changing Sandy Environment and Vegetative Restoration

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【Author in Chinese】 申景昕

【Supervisor】 虞毅

【Author's Information】 中国林业科学研究院, 水土保持与荒漠化防治, 2018, 硕士

【Abstract in Chinese】 机械沙障固沙是荒漠化防治的一种主要工程措施,在流沙治理及植被恢复中发挥着不可替代的作用。沙柳沙障是我国西北干旱、半干旱地区广泛使用的植物沙障,可降解聚乳酸(PLA)纤维沙袋沙障是近十年发展起来的一种绿色环境友好型纤维沙障,具有可完全降解、使用寿命长、生态效益好等优点,已在我国多个气候类型区实地推广应用,具有良好的防风固沙效果。本文以沙柳沙障和可降解聚乳酸纤维沙袋沙障作为研究对象,通过测定不同规格沙障(1 m×1 m、2 m×2 m)迎风坡上部、中部、下部的植被种类、数量、株高、冠幅、频度等指标,分析2种沙障对植被空间格局的影响及差异;通过测定土壤物理、化学性质、土壤酶活性以及土壤细菌多样性等指标,结合风速流场的模拟,分析2种沙障对流沙生境的作用效果,初步揭示了沙障对植被恢复与流沙生境的影响。主要结果如下:(1)不同材料及规格沙障对植被恢复的作用效果不同。PLA沙障与沙柳沙障均提高了植被密度、植被覆盖度。1 m×1 m、2 m×2 m PLA沙障的植被密度分别是裸沙丘的8.33倍、8.42倍,1 m×1 m、2 m×2 m沙柳沙障分别是裸沙丘的3.67倍、3.46倍。在不同沙丘部位上,PLA沙障沙丘中部植被密度较大,沙柳沙障沙丘下部植被密度较大。1 m×1m、2 m×2 m PLA沙障的植被覆盖度分别是裸沙丘的13.32倍、13.68倍,1 m×1 m、2m×2 m沙柳沙障植被覆盖度分别是裸沙丘的8.15倍、8.38倍。在不同沙丘部位上,PLA沙障在沙丘中部植被覆盖度较大,沙柳沙障在沙丘下部覆盖度较大。PLA沙障植物多样性高于沙柳沙障,且1 m×1 m PLA沙障植物多样性优于2 m×2 m PLA沙障。总体上,铺设沙障有利于沙丘植被的恢复,且PLA沙障优于沙柳沙障。(2)沙障障格内部植被的生长位置与空间格局表现各异。铺设1年的PLA沙障与沙柳沙障障格内植被多生长于上风向与下风向靠近障角与障边。由于沙障对风沙流的阻碍,障体前后发生不同程度的沙粒沉积,对植物种子产生一定的沙埋,促进了种子的着床萌发。在2 m×2 m障格内,PLA沙障障格内植被在小尺度上(r<7 cm)为聚集分布,随着尺度增加呈现均匀分布,最后为随机分布;沙柳沙障障格内植被呈现为随机分布。(3)沙障铺设后能够在一定程度上改善土壤物理性状。1 m×1 m PLA沙障均显著提高了0-10 cm层土壤含水量,2 m×2 m PLA沙障对0-10cm土壤含水量影响不明显;2 m×2 m沙柳沙障均显著提高了0-10 cm层土壤含水量,1 m×1 m沙柳沙障对0-10cm土壤含水量影响不明显。PLA沙障障格内中部区域的土壤含水量高于障格边缘区域,而沙柳沙障障格内各区域土壤含水量差别不明显。2种材料沙障作用下的土壤温度日变化表现一致:随着土壤垂直深度的增加,土壤温度日变化趋于稳定;5 cm、10 cm、20 cm土层土壤温度日变化幅度较大,变化趋势为先增大后减小;30cm、50cm层土壤温度较稳定,且沙障障格内土壤表层温度分布随着太阳辐射角度变化而变化。PLA沙障与沙柳沙障均增强了土壤表层硬度。两种规格PLA沙障障格内上风向与下风向硬度较小,障格中部硬度较大;1 m×1 m沙柳沙障障格内靠近上风向土壤硬度较小,2 m×2 m沙柳沙障障格内靠近下风向土壤硬度较小。铺设1年的沙柳沙障沙丘粗砂砾与粉沙含量增加;铺设1年的PLA沙障对土壤机械组成影响不明显;沙柳沙障粉粒与粗砂砾粒体积含量均大于PLA沙障沙丘与裸沙丘。(4)铺设1a的PLA沙障与沙柳沙障对土壤p H没有显著影响;铺设1a的PLA沙障土壤p H大于10a的PLA沙障,随着铺设年限的增长土壤p H有下降的趋势。土壤酶是土壤重要组成部分之一。铺设1a的PLA沙障与沙柳沙障对土壤脲酶、蔗糖酶酶活性没有显著影响;但沙柳沙障增加了过氧化氢酶活性。铺设10a的PLA沙障土壤酶活性大于铺设1a的PLA沙障,说明随着铺设年限的增加,土壤酶活性有增强的趋势。土壤微生物是土壤系统的重要组成部分。PLA沙障与沙柳沙障均能提高沙丘土壤细菌丰富度。1a的沙柳沙障土壤细菌丰富度高于1a的PLA沙障土壤细菌丰富度;10a的PLA沙障土壤细菌丰富度大于铺设1a的PLA沙障,随着设障年限增加土壤细菌丰富度有增加的趋势。(5)风速流场的模拟分析,气流经过PLA沙障障格内的风速流场变化趋势为:障前减速区、沿障体气流加速区、障后涡流减速区,障中加速区、障前减速区、沿障体加速区、障后涡流减速区。由于气流经过PLA沙障障格时的变化趋势,在障格内土壤表面蚀积强度不同形成凹曲面形态。通过对2种规格PLA沙障障格内风蚀情况进行分析,1 m×1 m规格障格内风蚀较深处靠近上风向障角或障边,2 m×2 m规格风蚀较深处靠近障格中间部位,且2 m×2 m规格风蚀深度是1 m×1 m规格的大约2倍。

【Abstract】 Mechanical sand barrier is one of the main technical means of desertification control in China.Salix Sand Barrier is a widely used type of sand barrier in the arid and semi-arid regions of Northwest China.Polylactic acid sand barrier(PLA)is a new type of sand barrier that does not pollute the environment.PLA sand barrier and Salix sand barrier are divided into two types(1 m×1 m、2 m×2 m).The study observes the diversity,amount,plant height,crown breadth of vegetation,analyses how the two sand barriers influences the spatial distribution and difference of vegetation.The study also research how sand barriers influence the ecosystem of sand dune by analyzing the chemical,physical,enzymatic and microbial characteristics of the sand dune.The main results are as follows:(1)In the study of restoration of natural vegetation in sand dunes,different types and sizes of sand barriers have different effects on vegetation restoration.PLA sand barrier and Salix Salix barrier increased vegetation density and vegetation coverage.The vegetation density of 1 m×1 m PLA sand barrier is 8.33 times that of bare sand dune.The vegetation density of 1 m×1 m and 2 m×2 m PLA sand barriers is 8.33 and 8.42 times that of bare sand dunes.The vegetation density of 1 m×1 m and 2 m×2 m Salix sand barrier is 3.67 times and 3.46 times that of bare sand dunes.The vegetation density of the PLA sand dunes in the middle of the sand dunes is larger.The vegetation density of the Salix sand dunes in the middle of the sand dunes is larger.The vegetation coverage of 1 m x 1 m and 2 m x 2 m PLA sand barrier is 13.32 times and 13.68 times than that of bare sand dunes.The vegetation coverage of 1 m×1 m and 2 m×2 m Salix sand barrier is 8.15 times and 8.38 times that of bare sand dunes.The vegetation coverage of PLA sand barrier in the middle part of the dune is larger,and the Salix sand barrier is largerr in the lower part of the dune.The plants diversity of PLA sand barrier is higher than Salix sand barrier.The plant diversity of 1 m x 1 m specification PLA sand barrier is better than 2 m×2 m PLA sand barrier.According to the above results,sand barrier is conducive to the restoration of dune vegetation,and PLA sand barrier is superior to Salix sand barrier.(2)In the study of vegetation distribution in the sand barrier,the vegetation is unevenly distributed in the sand barrier.In Grid of PLA Sand Barriers and Salix Sand barrier,vegetation density was the highest at corner and boundary of the grid.The vegetation within small-sized grid is concentrated.With size of grid increases,the vegetation is randomly distributed.The vegetation of the Salix Sand Barrier is evenly distributed.(3)The soil physical properties of the sand dune have been improved.The 1 m×1 m PLA sand barrier and the 2 m×2 m sand silage barrier significantly increased the soil water content in the 0-10 cm layer.The trend of soil water content distribution within the barrier was that the soil water content in the middle of the PLA sand barrier was higher than that in the marginal area of the sand barrier,and there was no significant difference in the Salix sand barrier barrier.With the increase of soil vertical depth,the daily change of soil temperature tends to be stable.The daily variation of soil temperature in 5 cm,10 cm and 20 cm soil layers was larger,and the trend was to increase first and then decrease;30cm,50 cm layer soil temperature is stable.The distribution of soil temperature in sand barrier is changed with the change of solar radiation angle.Both the PLA sand barrier and the Salix sand barrier increase the hardness of the soil surface.The hardness of the soil in the PLA sand barrier is smaller on the upwind and downwind,and the middle of the sand barrier is larger.The hardness of the soil near the upwind in the 1 m×1 m Salix sand barrier is smaller.The hardness of the soil near the downwind in the 2 m×2 m Salix sand barrier is smaller.In the past 1 years of Salix sand barrier,the content of coarse gravel and silt increased.1 year of Salix sand barrier coarse gravel and silt content increased;1 year PLA sand barrier had no obvious effect on soil mechanical composition.(4)In the study of soil biochemical properties,1 year PLA sand barrier and Salix sand barrier had no significant effect on soil p H.However,the soil p H of the PLA sand barrier laid for 1 year is greater than 10 years,and the soil p H has a tendency to decline with the increase of the laying year.1 year PLA sand barrier and Salix sand barrier had no significant effect on soil urease and sucrase enzymic activity.However,salix sand barrier increases catalase activity.The soil enzyme activity of PLA sand barrier for 10 years was greater than 1 years.With the increase of laying age,soil enzyme activity has a tendency to increase.Both the PLA sand barrier and the Salix sand barrier have a tendency to increase the soil bacterial richness of sand dunes.The soil bacterial richness of the Salix sand barrier laid for one year is higher than that of the PLA sand barrier.The soil bacterial richness of PLA sand barrier for 10 years was greater than 1 years.With the increase of laying age,the soil bacterial richness has a tendency to increase.(5)The change rule of the flow field within PLA shows as the following seven parts: Speed reduced area ahead of sand barriers,airflow uplift area along sand barriers,streaming slow-zone behind sand barriers,recovery-zone in sand barriers,the second Speed reduced area ahead of sand barriers,the second airflow uplift area along sand barriers,and the second streaming slow-zone behind sand barriers.The deeper of wind erosion is located near the upwind barrier for 1 m×1 m of PLA Sand barrier.wind erosion depth near the middle part of the barrier for 2 m×2 m of PLA Sand barrier,and 2 m×2 m wind erosion depth is about 2 times of 1m×1m.

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