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沙漠绿洲过渡带柽柳灌丛沙堆—丘间地系统土壤理化性质分异规律
刘进辉
学位类型硕士
导师王雪芹
2015
学位授予单位中国科学院大学
学位授予地点北京
学位专业水土保持与荒漠化防治
关键词沙漠—绿洲过渡带 柽柳灌丛沙堆 土壤粒度 土壤水分 土壤养分 土壤盐分 空间异质性
摘要本文以塔克拉玛干沙漠南缘策勒沙漠绿洲过渡带为研究区,选取土地退化进程中植被盖度依次为30%、15~20%、10%和<5%的四个典型样地,在对各样地蚀积分布有所认识的前提下,系统采集柽柳灌丛沙堆—丘间地系统典型部位0-10 cm和10-20 cm土壤样品,分析土壤粒度、枯落物、土壤水分、有机质、全效N、P、K,速效N、P、K含量,土壤pH值、总盐、Cl-、Na+、K+、SO42-、Ca2+、Mg2+、CO3 2-和HCO3-离子含量,从风沙地貌的角度研究过渡带沙漠化进程中土壤理化性质分异规律。结果表明: (1)研究区以极细沙为主,其次为粉沙和细沙,属于风力有效搬运的粒径范围。随着植被总盖度从30%→15~20%→10%→<5%降低,0-10 cm土层平均粒径从74.41 μm→77.28 μm→86.29 μm→92.71 μm变化,并伴随着黏粒消失和粗沙出现。相同植被条件下,以灌丛下土壤平均粒径最小、沙堆边缘和风影区次之、丘间地最大,分选性则以丘间地最好而灌丛下最差。30%植被覆盖地表以沉积过程为主,表明可截获相当部分悬移质使表层粒度组成细化。在植被盖度为10~20%地表,丘间地风蚀而沙堆表面及风影区积沙,对应丘间地物质组成粗化,而沙堆表层和风影区则出现相反的变化规律。在植被盖度<5%地表,灌丛沙堆及丘间地均发生强烈风蚀,地表物质组成普遍粗化。 (2)四个样地柽柳灌丛沙堆—丘间地系统0-10 cm土层土壤水分含量均很低(<0.4%),同一样地水分含量最大值多位于灌丛下部位。四个沙堆土壤水分含量具有相同的时间变化趋势,最小值均出现在八月份。随着植被总盖度的降低,灌丛沙堆表层0-10 cm土壤的枯落物、有机质、全N、全K、速效K含量呈降低趋势,从灌丛下→沙堆边缘→丘间地→风影区,土壤枯落物、有机质、全N、全P、速效N、速效P、速效K含量最大值位于灌丛下部位,最小值位于丘间地,但在植被盖度<5%的样地,沙堆—丘间地系统各部位之间养分含量无显著性差异。与0-10 cm土层相比,10-20 cm土层的枯落物、有机质、全N、全P、全K、速效P、速效K含量显著降低。随着植被盖度的降低,10-20 cm土层的养分含量具有与0-10 cm土层相一致的变化趋势。灌丛的生物反馈作用使得灌丛下部位具有明显的养分富集效应,但随着植被总盖度的降低和风沙活动不断加剧,非生物因素逐渐占据主导,灌丛的养分富集效应趋于减弱和消失,至少要维持>10%的植被覆盖是过渡带灌丛沙堆科学保育的前提。 (3)随着植被总盖度的降低,0-10 cm土层土壤pH值、总盐含量、Cl-、K+和Na+含量总体呈先升高后降低的趋势。从灌丛下→沙堆边缘→丘间地→风影区,总盐含量、Cl-、K+、Na+、SO42-、Ga2+和Mg2+含量最大值均位于灌丛下,最小值位于丘间地;pH值和HCO3-含量最小值位于灌丛下,最大值多位于丘间地,二者之间存在中度相关(r=0.644)。与0-10 cm土层相比,10-20 cm总盐含量、Cl-、K+和Na+明显增加,SO42-、HCO3-和Ga2+含量降低,Mg2+含量和pH值没有明显的变化。两土层各盐分含量随植被盖度的梯变呈相对一致的变化趋势。在不同的环境条件下,以蒸腾作用、泌盐作用和根系的选择性吸收作用等为主的生物积盐作用与地下水蒸发聚盐以及地表风蚀强度等非生物因素之间的平衡关系,应该是影响沙漠绿洲过渡带柽柳灌丛沙堆盐岛效应强弱的关键因素。 (4)相关性分析表明,柽柳灌丛枯落物分解是研究区表层土壤养分和盐分的主要来源,灌丛沙堆不同部位枯落物含量及其分布状态对土壤养分和盐分的分布有很大的影响。有机质是土壤氮和钾的主要来源。土壤pH值与养分指标之间呈负相关关系,尤其与有机质和速效钾呈显著性相关关系,说明土壤有机质和速效钾含量及分布状态对土壤盐分有很大的影响,同时还说明土壤高养分状态可以降低土壤的盐碱程度。速效钾与各养分和盐分指标之间具有较好的协调性。土壤粒度与养分和盐分之间的相关性表明,该研究区土壤养分和盐分的分布状态主要受细粒物质的影响,因此可以推断土壤蚀积对细粒物质的重新分配过程伴随着土壤养分和盐分的再分配过程。柽柳灌丛沙堆—丘间地系统表层土壤极低的水分含量对盐分的影响要大于对养分的影响。
其他摘要In present study, field experiments were carried out in desert-oasis ecotone in the south edge of Taklimakan Desert. Four types of typical plots with different vegetation coverage of 30%, 15~20%, 10% and <5% were chose as study sites. Soil at depth of 0-10 cm and 10-20 cm in Tamarix ramosissima nebkhas and interdune for analysis of soil grain size, litter, water , soil organic matter, total N, total P, total K, available N, available P, available K content, soil pH, total salinity, Cl-, Na+, K+, SO42-, Ca2+, Mg2+, CO32- and HCO3- content. Results showed that : (1) The study area was dominated by very fine sand and silt and both belong to the partical size that can be transported by wind. With the decrease of vegetation cover from 30% to 15~20% to 10% and to <5%, the average partical size in 0-10 cm soil layer gradually increased from 74.41 μm, 77.28 μm, 86.29 μm to 92.71 μm and accompanied by clay disappear and coarse sand appeared. Under the same vegetation condition, the minimum soil partical size mainly distributed under shrub, and the maximum value mainly distributed in interdune. For different position of nebkhas, the sorting of the interdune soil was the best, while under shrub was the worst. The vegetation in desert-oasis ecotone can intercept a considerable part of suspended sediment transported from far away places by wind and lead the surface material of the study area becoming more fine. The area of under shrub had much finer grains and the interdune had coarser sand apparently, which were closely related to wind-driven and redistribution of sand grain in situ. In areas with vegetation coverage less than 5% both nebkhas and interdune surface existed widespread soil erosion and ‘resource islands’ effects disappeared. For the sake of the stability of nebkhas, the total vegetation coverage should be maintained at least>10% in desert-oasis ecotone. (2) Soil water content is extremely low in Tamarix nebkhas-interdune system. The average values are all below 0.4%. Maximum values mainly distribute under shrub position. The soil water content change trends are same from April to October, with the minimum value appeared in August. With the decrease of vegetation coverage, Nebkhas litter, soil organic matter, total N , total K and available K content decreased. The content of available N and available P decreased firstly and then increased. The total P content had no obvious change. Litter, soil organic matter, total N, total P, available N, available P and available K content from Under shrub to Margin of nebkha to interdune to Leeward shadow decreased at first and then increased. Maximum values are happened under shrub position, and minimum values in the interdune. For each nutrient index, there was no significant difference among four study sites with vegetation coverage of <5%. Litter, organic matter, total N , total P, total K, available P and available K content was generally reduced in 10-20 cm soil layer compared to these in 0-10cm soil layer. With the decrease of vegetation coverage, the change trends of soil nutrient in two soil layers were consistent. The biological feedback of shrub made the nutrient Under shrub position obviously enriched. But with the decrease of total vegetation coverage and the increase of aeolian activities, nonbiological factors gradually became the dominant and the nutrient enrichment effect of shrub began to diminish and disappear. (3) With the decrease of vegetation cover from plot 1 to plot 4, soil pH, total salinity, Cl-, K+and Na+ content in 0-10 cm layer increased at first and then decreased. The maximum values mainly distribute in the plot with vegetation cover of 30%, the minimum values mainly distributed in the plot with vegetation cover of 15~20%. However, the maximum values of HCO3- content mainly distributed in the plot with vegetation cover of 15~20%, and there was no obvious change of Mg2+ content. However, soil pH and HCO3- content increased at first and then decreased and slightly cor-relationship was found between soil pH and HCO3- content (r=0.644). The maximum values mainly distributed in the ground of Under shrub, while the minimum values mainly distributed in the Interdune. Total salinity, Cl-, Na+ and K+ content in 10-20 cm soil layer significantly increased compared to these in 0-10 cm soil layer. However, SO42- content, Ca2+ content and HCO3- content were reduced and soil pH without obvious change. With the decrease of vegetation coverage, the changes of soil salinity content in the two soil layers are consistent. The transpiration, recretion and selective absorption of root of Tamarix ramosissima and soil evaporation result in obvious soil salinity enrichment effects around the area of Nebkhas. However, with the decrease of total vegetation cover and the increase of desertification intensity, the non-biological factors such as wind erosion began to play a leading role, and soil salinity enrichment effects of shrubs tended to diminish and disappear gradually. (4) Nebkhas litter content and distribution had a strong influence on the distribution of soil nutrients and salinity. Organic matter was a major source of soil nitrogen and potassium. There was a negative correlation between soil pH value and nutrient index, especially showed a significant correlation with organic matter and available potassium. So the content and distribution of soil organic matter and available potassium had a great influence on soil salinity. At the same time high soil nutrient status can reduce the degree of soil salinization. Available K had a good coordination with soil nutrients and salinity index. The distribution of soil nutrients and salinity was mainly affected by the fine material in the study area. It can be concluded that the redistribution of soil fine-grained material was accompanied along with the process of redistribution of soil nutrients and salinity. Effect of low surface soil water content on salinity was greater than the effect of nutrient in Tamarix ramosissima nebkhas and interdune in desert-oasis ecotone.
学科领域水土保持与荒漠化防治
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14653
专题研究系统_荒漠环境研究室
作者单位中科院新疆生态与地理研究所
推荐引用方式
GB/T 7714
刘进辉. 沙漠绿洲过渡带柽柳灌丛沙堆—丘间地系统土壤理化性质分异规律[D]. 北京. 中国科学院大学,2015.
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