干旱半干旱地区人工固沙灌木林生态系统演变特征

应用实验生态学方法分析了沙坡头地区栽植于1956、1964、1981、1987年的无灌溉人工植被固沙群落浅层土壤分形特征、植被盖度、物种特征、生物量、土壤水分、土壤微生物,以及群落土壤物理和土壤养分特征,并与流动沙丘进行比较。结果表明,在干旱半干旱的草原化荒漠地区,首先利用半隐蔽式草方格沙障对流动沙丘进行固定,然后栽植灌木柠条、花棒等和半灌木油蒿,经过40多年的稳定演变,该区域逐渐形成由矮灌木与草本植物覆盖,以及隐花植物与微生物土壤结皮复合的固定沙丘景观。在人工植被固沙防护体系稳定演变过程中,浅表层土壤的细粒化和养分富集化特征,微生物土壤结皮与亚表层土壤厚度,以及浅表层土壤体积含水率均随固沙年限的延长趋于显著增加。而土壤微生物数量、植被盖度、植物种数等生物群落学属性在固沙年限达40a左右时,已趋于最大,尔后呈缓慢下降趋势。随着固沙年限的增加,灌木树种不断衰退减少,当固沙年限逾17a之后,群落生物量增至峰值后略有下降。土壤分形维数与土壤粘粒含量呈显著正相关关系,流动沙丘被人工植被固定年代越久远,浅表层(0~3cm)土壤粘粒含量(4.50%)越高,其分形维数越大(D=2.4083),表明人工植被固沙防护体系浅表层土壤结构变得越紧实,流动沙丘(D=2.0484)在人工植被的固定作用下,发生逆转的趋势越显著,沙丘日趋固定。     

荒漠地衣对沙坡头人工植被固沙区的生态影响

腾格里沙漠东南缘沙坡头地区所形成的微型生物结皮(microbiotic crust)占优势的生态格局是荒漠地区天然植被中特有的生态景观之一。荒漠地衣作为微型生物结皮中重要的组成部分,在影响生态变化方面扮演着不可或缺的角色。本研究调查了不同建立年代的人工植被固沙区中的维管植物和微型生物结皮中地衣的物种组成和盖度,测定了结皮土壤的主要养分含量。结果显示:微型生物结皮中地衣以胶衣Collema和石果衣Endocarpon两属为优势类群;随人工植被建立时间的延长,维管植物和微型生物结皮盖度、结皮厚度与土壤养分含量呈增高趋势,并基本呈显著的正相关关系。维管植物、微型生物结皮、地衣和土壤养分基本一致的变化规律表明,微型生物结皮对固沙区中浅根系植被发育和土壤恢复具有正效应,为人工高效治沙及全面实施"沙漠生物地毯工程"提供了必要的理论基础。     

我国北方风沙危害区生态重建与恢复:腾格里沙漠土壤水分与植被承载力的探讨

我国北方风沙危害的主要防治区包括贺兰山以东沙地和以西的沙漠、绿洲和沙漠与荒漠草原过渡区,约3.2×105 km2.植被重建与恢复是该区遏制风沙危害的重要手段和有效的途径.基于腾格里沙漠沙坡头地区50余年的长期生态学研究,发现重建植被通过对土壤水分的利用和时空再分配改变了原来沙丘系统的水循环特征,在给定的区域降水条件下,土壤水的时空动态与重建植被动态密切相关;指出沙区水文过程的长期改变驱动着人工植被的演替;探讨了降水小于200 mm风沙区土壤水分的植被承载力和植物固沙的模式.     

腾格里沙漠沙坡头地区荒漠地衣与生物地毯工程

文章论述了荒漠地衣与“沙漠生物地毯工程”。在沙坡头结皮微型生物中发现了23种地衣,其中两个新种已发表,一属6种为中国新记录。对于在腾格里沙漠东南角沙坡头地区人工植被固沙防护体系建成后的生态演替进行了分析。由于人工植被为形成结皮的微型生物提供了适宜的生长环境而导致微型生物结皮的形成和发育。在水分平衡规律的作用下漫长生态演替过程中,具有抽水机效应的人工植被使沙土深层水分消耗殆尽,从而导致人工植被自身逐年衰退。然而,与此相反的是无抽水机效应而具有固沙、固碳和抗旱功能的结皮微型生物却逐年形成并发育。这一结果为借助于结皮微型生物的接种技术在干旱沙漠构建“沙漠生物地毯工程”的可行性提供了科学依据。为了优化“沙漠生物地毯工程”利用荒漠地衣耐旱基因以构建转基因草地植物的研究也正在进行中。该研究是“沙漠生物地毯工程”基础研究的组成部分。     

固沙区时间尺度上生态健康状况分析

以干旱区沙坡头不同时间尺度上人工植被防护体系为研究对象,初步研究了在区域荒漠化的治理过程中,生态环境的演变对生态健康的影响。结果表明：土壤水分和土壤结皮是影响固沙区生态健康的主要因子,老固沙区的健康状况趋于衰退,而新固沙区在演变过程中逐渐达到一种健康稳定状态。这对今后如何对老固沙区进行生态恢复和人工建设、对新固沙区进行调节和维持,使其发挥最优防护效益具有重要的参考价值。     

塔里木沙漠公路灌木固沙带的防护效应

有关湿润区[5] 与半干旱区和干旱区半荒漠带防风固沙片状植被[1～ 4 ] 以及干旱半干旱区乔木防护林带[6～ 9] 防护效益的研究报道较多 ,但极端干旱区灌木固沙带防护效应的报道则很少。为此 ,我们根据塔里木沙漠公路Ｌ2 89～ 2 92 段 3ｋｍ植物固沙示范段的试验观测 ,对极端干旱区灌木固沙带的防护效应做一探讨。1　研究地区与方法1 1　灌木固沙带栽植地段概况塔里木沙漠公路Ｌ2 89～ 2 92 段 3ｋｍ植物固沙示范段地处塔克拉玛干沙漠腹地的中三点处 (Ｎ39°0 1′ ,Ｅ83°36′)。风沙地貌属复合型纵向沙垄。据中三点1995年 6月～ 1996年 5月气…     

基于Meta分析的中国北方植被建设对土壤水分影响

植被建设是中国北方干旱半干旱地区防治风蚀和水蚀的最为有效手段,而合理的植被建设需要考虑土壤水分的植被承载力。在收集有关中国北方干旱半干旱地区植被建设后土壤水分研究文献的基础上,采用Meta分析研究了该地区植被建设(乔木和灌木)对土壤水分的影响。结果表明:北方干旱半干旱地区植被建设总体上对深层(40 cm以下)土壤水分含量产生显著降低作用(结合效应值为-0.40);乔木栽植导致土壤水分含量大幅度降低(-0.58),灌木栽植也在一定程度上导致土壤水分含量降低(-0.27),但其影响不显著;亚组分析表明,建植年限20 a的乔木以及栽植在降雨量超过400 mm以上地区的乔木是导致土壤水分含量显著降低的主要因素(其结合效应值分别为-0.62和-0.69);因此,乔木栽植对于土壤水分的消耗大于灌木,在该地区开展灌木栽植能够有效提高土壤水分利用效率。     

西南地区草地群落灌木植物盖度对生态系统碳库的影响

中国西南地区草地主要为暖性及热性草丛、灌草丛, 约占全国草地面积的1/10, 分析灌木植物盖度与草地碳库及其构成的关系对于准确评估尚处于次生演替阶段的南方草地碳储量具有重要意义。该研究基于野外实地调查, 将西南地区不同地貌类型的41个代表性草地样地依据灌木植物盖度划分为3种类型: 无灌木植物草地群落(灌木植物盖度为0)、低灌木植物盖度草地群落(灌木植物盖度0-10%)和高灌木植物盖度草地群落(灌木植物盖度10%-30%), 测定了群落地上、地下生物量和凋落物生物量以及植物和土壤碳含量, 计算碳密度。结果表明: 随着草地群落灌木植物盖度增大, 生态系统植被碳密度从0.304 kg·m ^-2增加到1.574 kg·m ^-2, 其中根系和凋落物碳库也呈增长趋势; 土壤碳密度从7.215 kg·m ^-2增加到9.735 kg·m ^-2, 生态系统碳密度从7.519 kg·m ^-2增加到11.309 kg·m ^-2。草地碳库构成中, 低灌木植物盖度草地群落的土壤碳库占生态系统碳库比例最小。草地群落灌木植物盖度增加改变了草地生态系统碳库构成并导致生态系统碳库增加, 建议在估算草地生态系统碳库时, 需要统筹考虑并兼顾南方地区草地群落灌木植物盖度变化。     

生物土壤结皮对荒漠土壤线虫群落的影响

在干旱的沙漠生态系统中,生物土壤结皮对于沙丘的固定和土壤生物的维持起着相当重要的作用.土壤线虫能敏感的指示土壤的恢复程度,是衡量沙区生态恢复与健康的重要生物学属性,而目前关于生物土壤结皮与土壤线虫的关系研究很少.为探明生物土壤结皮对土壤线虫的影响,以腾格里沙漠东南缘的人工植被固沙区藻结皮和藓类结皮覆盖的沙丘土壤为研究对象,根据固沙年限的不同将样地分为4个不同的区进行采样(1956、1964、1981和1991年固沙区),以流沙区作为对照;同时,在不同季度(4、7、9和12月)分别采集腾格里沙漠东南缘的人工植被固沙区藻结皮和藓类结皮覆盖下不同土层(0-10、10-20和20-30 cm)的沙丘土壤,以沙坡头地区的红卫天然植被区为对照,分析生物土壤结皮下土壤线虫的时空变化.采用改良的Baermann漏斗法进行分离线虫,用光学显微镜鉴定并统计.研究表明:1956、1964、1981和1991年人工植被固沙区的藻结皮和藓类结皮均可显著提高其下土壤线虫多度、属的丰富度、Shannon-Weaver多样性指数、富集指数和结构指数(P＜0.05),这可能是因为生物土壤结皮的存在为土壤线虫提供了重要的食物来源和适宜的生存环境;固沙年限与结皮下土壤线虫多度、属的丰富度、Shannon-Weaver多样性指数、富集指数和结构指数存在显著的正相关关系(P＜0.05),这说明固沙年限越久,越有利于土壤线虫的生存和繁衍;结皮类型显著影响土壤线虫群落,相对于藻结皮而言,藓类结皮下土壤线虫多度与属的丰富度更高(P＜0.05),这说明演替后期的藓类结皮比演替早期的藻结皮更有利于土壤线虫的生存和繁衍.此外,藻结皮和藓类结皮均可显著增加其下0-10、10-20和20-30 cm土层线虫多度和属的丰富度(P＜0.05),但随着土壤深度的增加,这种影响逐渐减弱,表明生物土壤结皮更有利于表层土壤线虫的生存;而且,随着季节的变化,藻结皮和藓类结皮下土壤线虫多度基本表现为秋季＞夏季＞春季＞冬季,这些反映了生物土壤结皮的生物量、盖度和种类组成随着季节变化而变化.因此,腾格里沙漠东南缘的人工植被固沙区生物土壤结皮的存在与演替有利于土壤线虫的生存和繁衍,增加了线虫数量、种类和多样性,这指示了生物土壤结皮有利于该区土壤及其相应生态系统的恢复.     

荒漠人工固沙植被区土壤水分的时空变异性

表层土壤水分具有高度的时间和空间变异性.研究的目的:(1)揭示沙坡头人工固沙植被区浅层土壤水分的时空变异性特征;(2)确定驱动土壤水分变异的主要环境因子.在人工固沙植被区内一个4500m2的网格样地上每隔10m设置取样点,在连续7个月的时间内 (2005年4～10月),每隔15d用时域反射仪测量各样点表层以下15cm和30cm深度的土壤容积含水量.结果表明,该区网格尺度上浅层土壤水分的分布具有明显的空间变异性,其变异性随着土壤水分含量的降低而减小;相对海拔是驱动土壤水分空间变异的主要环境因子,其作用在降雨后尤为显著,且其对土壤下层的影响比上层更明显;植被和土壤水分含量的相关性时间序列与相对海拔一致--降雨使其相关性增加;土壤质地(土壤粒径分布)和土壤水分含量的相关性时间序列特征与植被和相对海拔相反,且其对土壤上层的影响比下层更明显.因此,在沙坡头荒漠人工固沙植被区,降雨后的短暂湿润期,地形和植被是驱动浅层土壤水分变异的主要影响因子,而随着降雨之后土壤逐渐变干,土壤质地的影响变得更加明显.     

腾格里沙漠东南缘人工植被区降水入渗与再分配规律研究

试验于2001年8月17日至9月30日在中国科学院沙坡头沙漠试验研究站进行,主要利用时域反射仪(TDR)连续测量土壤剖面水分含量的方法,观测受植物根系吸水,蒸散作用影响下的人工植被荒漠灌木柠条(Caragana korshinskii)群落区固定沙丘降水入渗与再分配过程。土壤体积含水率由水平埋设在植物根系剖面内12个深度层次(5～200cm)的时域反射仪探头每小时自动测定1次。天然降水条件下的土壤入渗速率由入渗深度与相应的入渗时间之比值计算得到。结果表明：在7次不连续降水过程中,土壤入渗速率与降水强度呈简单线性相关关系,土壤入渗速率约为降水强度的10倍强。然而当次降水过程中降水强度小于0．46mm／h时,土壤入渗速率约为0cm／h,此时的降水对人工植被固定沙丘区的土壤基本上没有水分补给作用。受荒漠灌木柠条根系吸水作用的影响,其根系密集剖面深度40～140cm内降水水分入渗积累不明显。降水入渗速率及入渗深度受土壤剖面初始含水率多寡而变化,干燥土壤剖面有助于提高入渗速率及入渗深度。降水以后随着时间的推移,区域环境内空气温度、湿度等气象条件适宜,柠条生长进入相对旺盛阶段,其根系密集层140cm深度处土壤含水率在总体上下降的过程中,表现出昼消夜长的趋势,翌日8：00土壤含水率值略高于前一日20：00水分值0．1％～0．3vol．％。     

Evolutionary characteristics of the artificially revegetated shrub ecosystem in the Tengger Desert, northern China

The rain-fed sand-binding vegetation which stabilizes the migrating desert dunes in the Shapotou area at the southeastern edge of the Tengger Desert was initiated in 1956. The shrubs initially employed were predominantly Caragana korshinskii, Hedysarum scoparium, and Artemisia ordosica, and a desert shrub ecosystem with a dwarf shrub and microbiotic soil crust cover on the stabilized sand dunes has since developed. Since 1956 the success of this effort has not only ensured the smooth operation of the Baotou–Lanzhou railway in the sand dune area but has also played an important role in the restoration of the local eco-environment; therefore, it is viewed as a successful model for desertification control and ecological restoration along the transport infrastructure in the arid desert region of China. Some of the effects of recovery from desertification and ecological restoration on soil properties are shown by the increase in the distribution of fine soil particles, organic matter, and nutrients. The physical surface structure of the stabilized sand dunes, and inorganic soil crusts formed by atmospheric dust, have also led to the gradual formation of microbiotic soil crusts. Sand dune stabilization is associated with: (1) decreased soil particle size, (2) increased total N, (3) increased thickness of microbiotic crusts, (4) increased thickness of subsoil, and (5) an increase in volumetric soil moisture in the near-surface environment. After 17 years of dune stabilization, both the number of shrubs and community biomass decreased. The number of microbes, plant species and vegetation cover, all attained a maximum after the dunes had stabilized for 40 years. There is a significant positive correlation between the fractal dimension of soil particle size distribution (PSD) and the clay content of the shallow soil profile in the desert shrub ecosystem; the longer the period of dune stabilization, the greater the soil clay content in the shallow soil profiles (0–3 cm), and the greater the fractal dimension of soil PSD. This reflects the fact that during the revegetation processes, the soil structure is better developed, especially in the upper profile. Hence, the migrating sand dune becomes more stabilized. Therefore, the fractal model can be used to describe the texture and fertility of the soil, and, along with the degree of stability of the previously migrating sand dunes, can be used as an integrated quantitative index to evaluate the revegetation practice in the sand dune areas and their stabilization.     

Changes in soil and vegetation following stabilisation of dunes in the southeastern fringe of the Tengger Desert, China

Properties of the soil and sand-binding vegetation were measured at five sites plus a control on dunes of the Tengger Desert stabilized for periods of up to 50 years. In the topsoil, fine particles, total N, P, K and organic matter increased significantly with increasing site age. However, there were no significant changes in deeper soil profiles (>0.4 m depth). Soil pH, calcium carbonate content, and total salt content tended to increase with age. Soil water in the topsoil changed little with increasing age, but was closely related to rainfall during the 50-year period. For deeper soil layers (0.4–3.0 m) soil water decreased significantly with age. After revegetation, the number of herbaceous species increased up to 30 years and then levelled off to 12–14 species, whereas the number of shrub species decreased from the 10 initial sand-binding species to only 3 species. Shrub cover decreased from a highest average of about 33% to the current 9%, whereas cover and biomass of herbaceous species increased throughout succession from 1956 to 2006. The development of soil and cryptogamic crusts on the surface of stabilized dunes enhanced the colonization and establishment of herbaceous plants due to increasing water availability, clay and silt content and soil nutrients. We propose that changes in properties of the surface soil led to increased interception of water, favoring shallow rooted grasses and forbs over perennial shrubs.     

绿洲―荒漠交错带土壤水分变化特征初步研究

 以甘肃省的民勤绿洲为例,选择土壤水分最为亏缺的7月,对白刺(Nitraria tangutorum)沙包不同迎风面,以及绿洲和荒漠交错地带的土壤水分进行了取样分析。结果表明,对于白刺沙包而言,其上层和深层土壤水分是迎风坡大于背风坡,中间层次（40～80 cm）则刚好相反。在绿洲与荒漠的交错带上,灌丛沙包与沙丘间低地水分变化有很大的不同,总体而言,丘间地水分含量大于灌丛沙包,但在距离绿洲406 m处,二者均出现一个土壤水分的最低值。在丘间地表层,水分变化是距离绿洲愈近,土壤含水量愈高;而深层土壤水分的变化趋     

Long-Term Ecosystem Effects of Sand-Binding Vegetation in the Tengger Desert, Northern China

The planting of sand‐binding vegetation in the Shapotou region at the southeastern edge of the Tengger Desert began in 1956. Over the past 46 years, it has not only insured the smooth operation of the Baotou–Lanzhou railway in the sand dune section but has also played an important role in the restoration of the local eco‐environment; therefore, it is viewed as a successful model for desertification control and ecological restoration along the transport line in the arid desert region of China. Long‐term monitoring and focused research show that within 4–5 years of establishment of sand‐binding vegetation, the physical surface structure of the sand dunes stabilized, and inorganic soil crusts formed by atmospheric dust gradually turned into microbiotic crusts. Among the organisms comprising these crusts are cryptogams such as desert algae and mosses. In the 46 years since establishing sand‐binding vegetation, some 24 algal species occurred in the crusts. However, only five moss species were identified, which was fewer than the species number in the crust of naturally fixed sand dunes. Other results of the planting were that near‐surface wind velocity in the 46‐year‐old vegetation area was reduced by 54.2% compared with that in the moving sand area; soil organic matter increased from 0.06% in moving sand dunes to 1.34% in the 46‐year‐old vegetation area; the main nutrients N, P, K, etc., in the desert ecosystem increased; soil physicochemical properties improved; and soil‐forming processes occurred in the dune surface layer. Overall, establishment of sand‐binding vegetation significantly impacted soil water cycles, creating favorable conditions for colonization by many herbaceous species. These herbaceous species, in turn, facilitated the colonization and persistence of birds, insects, soil animals, and desert animals. Forty‐six years later, some 28 bird species and 50 insect species were identified in the vegetated dune field. Thus, establishment of a relatively simple community of sand‐binding species led to the transformation of the relatively barren dune environment into a desert ecosystem with complex structure, composition, and function. This restoration effort shows the potential for short‐term manipulation of environmental variables (i.e., plant cover via artificial vegetation establishment) to begin the long‐term process of ecological restoration, particularly in arid climates, and demonstrates several techniques that can be used to scientifically monitor progress in large‐scale restoration projects.     

Effect of sand-stabilizing shrubs on soil respiration in a temperate desert

Aims

Explore how soil CO₂ efflux and its components change after moving sand dunes are stabilized with shrubs, and how abiotic factors affect those components at different scales.

Methods

Soil CO₂ efflux from a sand-stabilized area was compared to that from moving sand dunes in the Tengger Desert. To partition rhizosphere respiration (R_R) from soil basal respiration (R_B), a root-isolation plot was established.

Results

Compared to moving sand dunes, total soil respiration (R_T) in the sand-stabilized area increased 3.2 fold to 0.28?±?0.08 μmol CO₂ m^-2?s^-1, two thirds of which was from R_B. Shrub patchiness produced spatial variation in soil respiration, whereas temporal dynamics of soil respiration were affected mainly by soil water content. Shallow soil water content (0–20 cm) influenced R_T and R_B, whereas deep soil water content (30–210 cm) influenced R_R and the ratio R_R/R_T. During most of the year when soil water content was below field capacity, diurnal changes in soil respiration were partially decoupled from soil temperature but could be modeled using soil temperature and photosynthetic active radiation.

Conclusions

Sand-dune stabilization increased soil respiration, and increased R_B from biological soil crust and altered soil properties such as increased soil organic matter contributed more than increased R_R from increased shrubs.     

Ecological restoration and recovery in the wind-blown sand hazard areas of northern China: relationship between soil water and carrying capacity for vegetation in the Tengger Desert

The main prevention and control area for wind-blown sand hazards in northern China is about 320000 km2 in size and includes sandlands to the east of the Helan Mountain and sandy deserts and desert-steppe transitional regions to the west of the Helan Mountain.Vegetation recovery and restoration is an important and effective approach for constraining wind-blown sand hazards in these areas.After more than 50 years of long-term ecological studies in the Shapotou region of the Tengger Desert,we found that revegetation changed the hydrological processes of the original sand dune system through the utilization and space-time redistribution of soil water.The spatiotemporal dynamics of soil water was significantly related to the dynamics of the replanted vegetation for a given regional precipitation condition.The long-term changes in hydrological processes in desert areas also drive replanted vegetation succession.The soil water carrying capacity of vegetation and the model for sand fixation by revegetation in aeolian desert areas where precipitation levels are less than 200 mm are also discussed.