Study on the Degradation Characteristics of Haloxylon Ammodendron Community in Western Gurbantunggut Desert
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【Author in Chinese】 李中赫；
【Author's Information】 石河子大学， 农业工程， 2018， 硕士
【Abstract in Chinese】 梭梭群落是中国第二大沙漠—古尔班通古特沙漠的主要植物群落,在防风固沙、改良土壤和维护绿洲-荒漠生态平衡中起到举足轻重的作用。但调查发现古尔班通古特沙漠西部的梭梭群落处于严重退化状态。退化区梭梭群落内的植株大量枯死,群落内物种稀少,因此梭梭群落退化的原因有待研究。本文通过对古尔班通古特沙漠西部的梭梭群落进行调查,对比研究总结3种环境下梭梭群落物种组成、植物分布、多样性特征及土壤理化性质的变化特征,并结合土壤理化性质分析天然梭梭群落退化与土壤理化性质的关系,对梭梭林退化区的植被修复及北疆绿洲区的生态保护具有理论指导意义。结果如下:(1)3种不同退化程度的所有样方中共出现了20种植物,群落物种的组成较为简单,有乔木1种,灌木5种,草本14种,隶属8科19属。3种不同退化程度的梭梭群落的物种组成、物种数量以及物种多样性指数均发生改变,随着退化程度的加重,植物物种数先增大后减小,而物种多样性指数表现为先增大后减小,三种不同退化程度的梭梭群落皆属于极不相似级别。(2)严重退化区19个样地的梭梭群落物种组成稀少,群落结构较为单一,Shannon-Wiener指数大于0.8的样地仅有3个,Simpson优势度指数均较高,而Pielou指数在各样地间的波动明显,所选样地中植被盖度最高为15.35%,最低为0.99%。(3)不同土层土壤剖面理化性质表明土壤平均电导率、有机碳、氯离子、土壤含水量、土壤储水量均随着退化程度的加剧表现为增长的趋势。并且随退化程度的加剧,表层土壤理化性质大于深层土壤理化性质。(4)相关分析表明严重退化区19个样点的梭梭群落总盖度与0~40cm土层土壤理化性质有显著的正相关性(p<0.05),梭梭群落死亡植株盖度与0~40cm土层土壤理化性质有显著的正相关性(p<0.05)。主成分分析发现0~40cm土层的土壤理化性质综合起来对群落物种多样性产生抑制作用。(5)综合研究认为,古尔班通古特沙漠西部梭梭群落结构简单,物种组成稀少,并且正进行逆向演替的过程。随着梭梭群落的退化,群落内梭梭植株的衰败分解糜烂,将体内矿质元素积聚在土壤表层,致使表层土壤理化性质变劣,从而抑制了群落中不同物种的种子萌发、幼苗建立,进一步恶化了梭梭群落物种多样性组成,最终导致梭梭群落的大面积退化。
【Abstract】 Haloxylon ammodendron community is the main plant community in the Gurbantunggut desert of the second largest desert in China.It plays a important role on windbreak and sand fixation,soil improvement and maintaining the oasis-desert ecological balance.However,the survey found that the H.ammodendron community in the western part of the Gurbantunggut Desert is in a state of severe degradation.The plants died a lot in the H.ammodendron community in the degraded area and the species in the community were scarce,so the cause of the degeneration of H.ammodendron community remains to be studied.In this study,three different degraded H.ammodendron communities in the western Gurbantonggut desert were investigated to compare and study the species composition,plant distribution,diversity characteristics,and soil physicochemical properties of H.ammodendron community.Combining with the physicochemical properties of soil,the relationship between the soil physicochemical properties and degradation of natural H.ammodendron community were analyzed.It is theoretical significance for the restoration of vegetation in the degraded areas of H.ammodendron and ecological protection in the northern Xinjiang’s oasis area.The results are as follows:(1)There are 20 species of plants in all three species with different degrees of degradation.The composition of species in the community is relatively simple: there are 1 species of trees,5 species of shrubs,and 14 species of herbs,belonging to 8 genera and 19 genera.The species composition,species number,and species diversity index of H.ammodendron communities with different degrees of degradation were changed.As the degree of degradation increased,the number of plant species increased first and then decreased,while the species diversity index showed the first increase.And three different degrees of degradation of H.community are very dissimilar.(2)The H.ammodendron community in 19 plots in the degraded area is rare and its community structure is relatively simple.Shannon-Wiener of only 3 plots index were higher than 0.8.Simpson dominance index were all higher,and the Pielou index fluctuate significantly among plots.The highest coverage of vegetation in selected plots was 15.35% and the lowest was 0.99%.(3)The physicochemical properties of the soil profiles in different soil layers indicated that the average soil electrical conductivity,organic carbon,chloride ions,soil moisture content,and soil water storage all showed an increasing trend with increasing degree of degradation.With the intensification of degradation,the physicochemical properties of surface soil were higher than the physicochemical properties of deep soil.(4)Correlation analysis showed that there was a significant positive correlation between the total coverage of H.ammodendron communities in 19 plots and the physicochemical properties of 0-40 cm soil layers in the degraded areas.And there was a significant positive correlation between the coverage of the dead plants of H.ammodendron communities and the physicochemical properties of 0-40 cm soil layers.Principal component analysis revealed that soil physicochemical properties in 0-40 cm soil layer combined to inhibit community species diversity.(5)A comprehensive study suggests that the community structure of H.ammodendron in the Gurbantunggut Desert is simple and species composition is scarce,and it’s undergoing a process of reverse succession.With the degeneration of H.ammodendron community,the H.ammodendron in the community is degraded through years of decomposition and erosion,witch resulted in the accumulation of mineral elements in the soil surface.As a result,the physicochemical properties of the surface soil deteriorate,which affects the seed germination and seedling establishment of different species in the community and the plant distribution and diversity composition,and in turn causes changes of the species diversity of H.ammodendron community.Eventually it will be lead to extensive degradation of H.ammodendron community.