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     

民勤绿洲-荒漠过渡带植被梯度特征及其土壤水环境

民勤绿洲-荒漠过渡带的植被和土壤水环境随着与绿洲距离的增加具有明显的空间异质性,在景观分异角度沿绿洲至荒漠方向可划分为4个区段。本文研究了各景观区段上的植被特征以及各区段丘间地及灌丛沙包土壤水分特征。结果表明:过渡带植被总盖度约为36%,灌木盖度为18.7%,草本盖度为18.0%,物种丰富度为19。区段1至区段4,物种组成、植被盖度、优势种、建群种均表现出与各区段立地条件相适应的特征,呈现出大灌木→草本→小灌木→草本的格局,对应的地貌呈现出固定→半流动→半固定→流动的格局。各区段丘间地土壤含水量垂直分布差异较大,5～60cm为降水主要持水层;因弱透水层的出现,区段1至区段3在60～180cm含水量出现了第二次波动,水分在弱透水层上的积累为地上植物的生存提供了重要的补给。沙包内土壤含水量从区段1到区段3显著减少。     

科尔沁沙地不同地形小叶锦鸡儿灌丛土壤水分动态

根据科尔沁沙地广泛分布的小叶锦鸡儿灌丛的植被调查和土壤水分监测数据,分析了沙地人工固沙灌丛的土壤水分时空动态和土壤储水量变化,并应用水量平衡法测定了灌丛蒸散发.结果表明:丘间地的土壤水分条件最好,丘中次之,丘上最低;灌丛区的土壤水分含量随深度增加而增加,在生长季内不会发生水分胁迫.灌丛区土壤水分与降雨过程高度相关,深层(50～180 cm)土壤水分同降雨的相关性高于表层(0～50 cm)土壤,并且深层土壤水分的变异也大于表层.整个生长期内,小叶锦鸡儿灌丛土壤储水量增加,土壤水分处于积累中,估算蒸散量占同期降雨量的64%以上.     

民勤绿洲-荒漠过渡区水量平衡规律研究

以甘肃省民勤县刘家地村外缘的绿洲 -荒漠过渡地带为定位研究区域 ,利用长期调查和水文学研究方法从生态系统的角度对绿洲 -荒漠过渡区的水量平衡特别是土壤水分和蒸散量的时空格局与动态特征进行了研究。结果显示 :1沿绿洲至流动沙丘这一过渡带 ,随着与绿洲距离的逐渐拉大 ,土壤含水量减小 ,0～ 80 cm土层的月平均土壤含水量的大小顺序为红柳沙包(5 .6 1% ) >白刺沙包 (5 .4 7% ) >流动沙丘 (5 .2 2 % ) ;土壤水分垂直变化规律是由表层到深层依次递增。 2在蒸散日进程中 ,红柳沙包和白刺沙包的蒸散率峰值到来时间比流动沙丘早 1～ 2 h,且日最大蒸散速率大小顺序为红柳沙包 (0 .2 4 mm / h) >白刺沙包 (0 .2 0 m m/ h) >流动沙丘 (0 .18mm/ h) ;影响绿洲荒漠 -过渡区蒸散的主要气象因子为日照百分率、气温、空气饱和差以及风速等 ,它们与日蒸散量的斜率关联度分别为 0 .717、0 .6 4 3、0 .6 4 9和 0 .70 5。3生态系统总的水量平衡特点是 ,水分输入主要靠降水和土壤水分的水平运动补给 ,而土壤和植被蒸发散是系统的主要输出项。     

内蒙古高原荒漠区四种锦鸡儿属植物灌丛沙包形态和固沙能力比较

测定了内蒙古高原荒漠区4种锦鸡儿属优势植物(柠条锦鸡儿、狭叶锦鸡儿、荒漠锦鸡儿和垫状锦鸡儿)不同大小灌丛的灌丛形态参数、沙包形态参数和沙包体积,目的是掌握这些锦鸡儿属植物灌丛的沙包形态特征、沙包发育特征和固沙能力随着灌丛发育的变化,比较4种锦鸡儿属植物灌丛沙包的形态、发育特征和固沙能力的差异。研究发现:柠条锦鸡儿沙包形态呈球冠状,狭叶锦鸡儿沙包呈圆锥状,荒漠锦鸡儿沙包呈圆台状,垫状锦鸡儿沙包呈半球状。同种锦鸡儿属灌丛沙包的底面直径与地上枝条鲜重呈极显著正相关关系(P<0.01),沙包高度与地上枝条鲜重无显著相关性(P>0.05),沙包高度与植物株高呈显著正相关关系(P<0.05),沙包坡角与地上枝条鲜重呈显著负相关关系(P<0.05),沙包半径与沙包高度呈显著正相关关系(P<0.05)。灌丛水平扩展快于垂向生长,灌丛沙包的水平发育也快于垂向发育。随着灌丛地上生物量的增加,4种锦鸡儿属植物不仅沙包体积增大,而且固沙效率也显著增加(P<0.01)。不同锦鸡儿属植物灌丛和沙包形态参数存在显著差异。柠条锦鸡儿和狭叶锦鸡儿的灌丛水平和垂直方向成比例扩展,而荒漠锦鸡儿和垫状锦鸡儿无论灌丛面积多大,高度基本不变。随着灌丛地上枝条鲜重的增加,4种锦鸡儿灌丛沙包底面积都在增大,其中荒漠锦鸡儿增长最快,垫状锦鸡儿次之,柠条锦鸡儿排位第三,狭叶锦鸡儿增长最慢。随着灌丛沙包水平方向的扩展,荒漠锦鸡儿沙包垂向扩展最慢,最终导致其沙包垂向尺度最小;柠条锦鸡儿、垫状锦鸡儿和狭叶锦鸡儿沙包两个方向发育较为均衡。4种锦鸡儿属植物的固定沙包体积和固沙效率都表现为:荒漠锦鸡儿>柠条锦鸡儿>狭叶锦鸡儿>垫状锦鸡儿。这些研究结果表明,灌丛地上生物量的不同决定了种内沙包的体积、形态和植物固沙能力的差异;灌丛形态和发育特征的不同决定了种间沙包形态、沙包发育和植物固沙能力的差异。     

绿洲-荒漠交错带环境特征初步研究

以甘肃省石羊河下游的民勤绿洲为例,对其绿洲外围与荒漠交错地带的植被和植被关系密切的灌丛沙包特征进行了系统研究,结果表明,由于生态交错带边缘效应的存在,植被盖度的变化呈现绿洲附近与交错带外围靠近流沙的地方较低,而位于流沙和绿洲之间的部分相应较高,植被盖度较高的部位主要集中于自流动沙丘至绿洲外600m处,而非紧靠近绿洲、这与地下水自沙漠向绿洲方向运移有关,在绿洲外缘300～600m的范围内植被盖度出现下降,原因可能与绿洲荒漠交错带界外区的形成有关,说明研究区绿洲0～600m范围即是该区域绿洲界外区的存在区域,灌丛沙包上的裸沙率以绿洲界外区为最大,大量沙包裸露,可致沙子的活动性增强,因此该地带是对绿洲土地造成沙质荒漠化的最大流沙来源。     

干旱荒漠白刺灌丛植被演替过程土壤种子库变化特征

土壤种子库是反映气候与土地利用变化的指示器,也是荒漠植被更新与恢复的基础。典型荒漠白刺灌丛植被广泛分布于我国西北绿洲边缘地带,对保护绿洲免受风沙危害发挥着重要作用。但是,对干旱荒漠白刺灌丛植被土壤种子库仍未见研究报道。应用空间代替时间的方法,选择石羊河下游白刺灌丛植被演替的初始阶段、稳定阶段、衰退阶段与严重衰退阶段样地,研究了白刺灌丛植被演替过程的土壤种子库物种组成、时空分布和数量变化特征。结果表明:石羊河下游白刺灌丛植被演替过程中,土壤种子库共出现9科18种植物,其中草本植物占到55%—80%,是白刺灌丛植被土壤种子库的主体。不同演替阶段土壤种子库密度以稳定阶段最高,达到660.7粒/m2,是初始阶段、衰退阶段和严重衰退阶段的5.6、14.5倍和6.2倍。不同沙堆部位,土壤种子库密度以迎风坡中部与背风坡中部最高,分别达到329粒/m2和309粒/m2;沙堆土壤种子库密度是堆间地的1.9倍,土壤种子库主要分布于灌丛沙堆上。不同演替阶段土壤种子库间的相似性系数均在0.6以下,除稳定阶段外,其他阶段间均属于中等相似水平;土壤种子库与地上植被的相似性系数均在0.5以上,达到中等相似或极相似水平。该研究进一步证明了灌丛沙堆和土壤种子库在白刺灌丛植被中的重要性,也说明人为干扰损害了白刺灌丛地下潜在植被及其恢复潜力。因此,需要开展人工种子库或人工植被建设以控制干旱荒漠白刺灌丛沙堆活化,并实现退化白刺灌丛植被恢复。     

浑善达克沙地不同微地形的土壤物理性质和草本群落分布及其相关性分析

采用样方调查和室内检测相结合法对内蒙古浑善达克沙地迎风坡、坡顶、背风坡和丘间地不同土层(0~10、10~20和20~40 cm)的土壤物理性质(包括含水量、田间持水量、容重、总孔隙度和毛管孔隙度)及草本群落的生产力(包括盖度和地上部生物量)和物种多样性(包括Margalef丰富度指数、Simpson多样性指数、Shannon-Wiener多样性指数和Pielou均匀度指数)进行比较分析;在此基础上,采用Pearson相关性分析法对不同微地形的土壤物理性质与草本群落各指标间以及草本群落生产力与物种多样性各指标间的相关性进行分析.结果表明:4种微地形的土壤物理性质总体上差异显著,但不同土层的土壤物理性质总体上无明显差异;从丘间地、背风坡、坡顶到迎风坡,土壤的含水量、田间持水量、总孔隙度和毛管孔隙度依次递减,而土壤容重则依次递增,说明迎风坡的土壤结构较差且水分散失较多,而丘间地的土壤结构和水分状况均相对较好.不同微地形间草本群落生产力和物种多样性总体上也存在明显差异,从背风坡、丘间地、坡顶到迎风坡,草本群落的生产力和物种多样性依次递减,仅Margalef丰富度指数表现为在丘间地最高、在迎风坡最低,说明迎风坡的草本群落物种多样性较低,群落稳定性差,而背风坡和丘间地的草本群落物种多样性和生产力水平均较高,群落稳定性较好.相关性分析结果表明:该区域的草本群落生产力和物种多样性与土壤容重呈负相关,与土壤的其他物理性状呈正相关,但仅部分指标间有显著或极显著相关性;草本群落生产力与物种多样性各指标间呈正相关,但多数指标间的相关性并不显著.研究结果显示:微地形能够显著影响浑善达克沙地的土壤物理性质和草本群落的分布特征,气候和人为干扰使该沙地的土壤物理性质受到严重破坏,导致草本群落生产力降低并处于不稳定状态.     

荒漠绿洲湿地土壤优先流与水分入渗特征

地表水分、溶质和污染物以土壤优先流的形式下渗到深层土壤或地下水中,将导致土壤养分流失与地下水污染等问题。因此,土壤优先流研究将为干旱区荒漠绿洲湿地水分运移与盐分积累过程提供理论依据。以荒漠绿洲湿地为研究区,选取柽柳灌丛、盐碱草地和杨树林,以道路为对照,采用室外染色示踪法对湿地土壤优先流特征与水分入渗进行研究。结果表明:不同植被类型土壤优先流入渗深度存在显著差异,其柽柳灌丛和盐碱草地几乎是杨树林和道的2倍;染色面积比随深度的增加而波动下降,0—20 cm土层染色面积比占总染色面积的54.42%—89.27%;染色路径宽度以20—250 mm和250 mm为主;优先流类型以高相互作用混合流和非均质指流为主。在荒漠绿洲湿地,砾石促进土壤优先流发生,增加了侧向流;同时,粗根的减少抑制了优先流的发生;此外,土壤盐分通过影响土壤大孔隙分布而影响水分入渗过程。因此,荒漠绿洲湿地土壤优先流与水分入渗差异是土壤质地、根系分布与盐分离子共同作用的结果。     

福建平潭岛海岸不同演化阶段草丛沙堆表面老鼠艻叶水势日变化特征

以福建省平潭岛海岸不同演化阶段草丛沙堆表面典型沙生植物老鼠艻为对象,研究其叶水势日变化特征及其影响因素.结果表明: 老鼠艻叶水势日变化以“W”型为主,午间出现短暂升高现象.发育阶段沙堆表面老鼠艻叶水势日均值较稳定阶段高,且夜间水分恢复能力更强;老鼠艻叶水势与大气水势和相对湿度呈显著正相关,与气温呈显著负相关,但与不同深度土壤水势无显著相关性;发育阶段沙堆丘间地老鼠艻叶水势在10:00—16:00皆高于迎风坡和背风坡,迎风坡除10:00和12:00外皆低于背风坡.不同坡位叶水势日变异程度表现为背风坡>迎风坡>丘间地,但无显著差异.沙堆迎风坡老鼠艻叶水势与大气水势和相对湿度呈显著正相关,与气温呈显著负相关;沙堆背风坡和丘间地老鼠艻叶水势与气象因子有一定相关性,但不显著.     

民勤沙区植被退化与年际降水量关系的定位研究

民勤沙区荒漠植物盖度随年际降水量变化明显,植被在随年际降水量变化的波动中退化。在一般年份,白刺、梭梭、沙蒿等灌木上部发生枯梢,在降水量偏少或分布异常年份会整株枯死,所以有的年份植被盖度和灌木高度反而会降低。不同植被群落分布的地貌条件和土壤条件有较大差异:白刺以白刺沙丘的形式存在,白刺沙丘0～30cm土壤含水率在1.4%～2.0%之间;膜果麻黄仅分布在粘砾石质滩地上,0～30cm土壤含水率<0.8%;沙蒿分布在低缓的半固定沙丘、流动沙丘和覆沙滩地上,0～30cm土壤含水率在0.9%～1.7%之间。植物通过土壤水分变化对降水作出反应,土壤水分条件对降水的反应受土壤颗粒的影响,细砂粒对降水反应灵敏。优势种植物高度与7月下旬～9月下旬的降水量之间存在较大的正相关;草本植物平均盖度与7月下旬～9月下旬和5月下旬～7月下旬期间的降水量之间存在较大的正相关。全年降水量主要影响植被总盖度。5月下旬～7月下旬的降水量对植被的影响较全年降水量更为明显。     

毛乌素沙地沙丘土壤含水量特点——兼论老固定沙地上油蒿衰退原因

土壤表面干沙层在冬春少雨季节较厚,流动沙地的又明显地大于固和地的。流动沙地地表干沙层以下的土壤含水量一般在于同深化度固定沙地的,特别是在报系密集分布的土层。科季或早春土壤含水量比较低,雨季的明显较高,雨季结束后,土层中的水分在重力的作用下会向深层运动,导致根系层土壤含水量下降。在植物生长季,缺少降雨时,因少地的土土壤水量会因植物的蒸腾消耗而变得很低（１％～２％）,而流动沙地的不受或受此影响很小。地     

腾格里沙漠人工植被区固沙灌木影响深层土壤水分的动态模拟研究

灌木是我国沙漠地区主要的优势植物类型,固沙灌木的存在有益于沙丘的固定进而有利于退化沙漠生态系统的生态恢复。基于腾格里沙漠沙坡头地区50多年的人工植被区长期观测研究,建立生态-水文模型模拟了该地区固沙灌木盖度和深层土壤水分的动态变化过程,结果表明,固沙灌木的建立改变了沙区原有的生态-水文过程,在固沙灌木建立40多年后,固沙灌木的盖度和深层土壤水分达到了新的平衡状态。灌木盖度逐渐稳定在(10±0.9)%左右,而深层土壤水分稳定在(2.58±0.2)%左右。因此,在年均降雨量为186mm的腾格里沙漠沙坡头地区,土壤水分的最大植被承载力为:灌木和生物土壤结皮的盖度分别维持在10%和60%,深层土壤水分维持在3%左右。     

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.     

荒漠绿洲边缘区泡泡刺种群对风沙干扰的响应

研究了位于黑河中游荒漠绿洲外缘 (荒漠与绿洲过渡带 )戈壁与沙漠两种生境下泡泡刺种群对风沙干扰的响应。结果表明 ,因风沙干扰的响应 ,泡泡刺种群以斑块状格局形式存在 ;独立灌丛沙堆的形成途径主要有 4种 :种子发育、根蘖繁殖、较大的沙堆退化 (生境破碎化 )和邻近沙堆的兼并。水分条件是泡泡刺种群生长的重要制约因素 ,长期对有限的水分资源竞争 ,使其大小和空间分布都形成了明显的特征。绿洲与戈壁交错带 (类似戈壁生境 )样地的泡泡刺种群的沙埋深度、种群高度、种群盖度、种群大小、生物量都小于绿洲与沙漠交错带 (类似沙漠生境 )样地的泡泡刺种群的相应的种群特征变量 ,而绿洲与戈壁交错带样地的泡泡刺种群密度却大于绿洲与沙漠交错带样地的相应的种群特征变量。绿洲与戈壁交错带样地的泡泡刺种群密度为33.3株 / m2 ,而绿洲与沙漠交错带样地的泡泡刺种群密度为 2 5 .4株 / m2 。两样地泡泡刺种群的沙埋深度、种群高度、盖度、密度及大小存在着显著差异 ,只有生物量无显著差异。两样地中泡泡刺的沙埋深度对泡泡刺种群特征的影响明显 ,无论戈壁还是沙漠生境 ,沙埋深度与种群高度、种群大小、种群生物量明显正相关。适度沙埋可以促进泡泡刺种群的生长 ,但当沙埋深度超过10 0 cm时 ,又会对泡泡刺种群     

新月形沙丘稳定性机理——以甘肃河西沙区为例

新月形沙丘是一种重要的沙丘类型,一般存在于绿洲边缘。研究新月形沙丘的稳定性,对于揭示绿洲缘的风沙运动规律有重要学术价值,而到目前新月形沙丘的稳定性还是沙漠生态学领域中一个的尚未解决的科学问题。以河西沙区新月形沙丘为例,通过调查其分布环境、测定沙丘各部位风速和风蚀积沙等,分析了新月形沙丘顶部稳定机理。结果表明:1)甘肃河西沙区的新月形沙丘分布在沙漠边缘的下风向,一般为斑块状分布。分布区域为平坦的沙粘质或沙砾质滩地,丘间地较为开阔且具有明显的主风向。2)主风向(NW)过程是新月形沙丘顶点与沙脊线重合的过程,也是新月形沙丘前移和高度降低的过程;反主风向(SE)过程是新月形沙丘顶点与沙脊线分离的过程,也是新月形沙丘背风坡上部风蚀与沙丘增高的过程。3)新月形沙丘越高大,两翼越长、夹角越小。4)较为开阔的前后滩地是新月形沙丘及新月形沙丘链存在所必须的环境条件,相对单一的主风向是新月形沙丘及新月形沙丘链维持其稳定性的关键因子,反向风及两翼的廊道效应是新月形沙丘增高增大的关键因子,主、反两个方向的风速及其分布频率是控制该区域新月形沙丘及新月形沙丘链高度的限制因子。     

Factors influencing the natural regeneration of the pioneering shrub Calligonum mongolicum in sand dune stabilization plantations in arid deserts of northwest China

Calligonum mongolicum is a successful pioneer shrub to combat desertification, which is widely used for vegetation restoration in the desert regions of northwest China. In order to reveal the limitations to natural regeneration of C. mongolicum by asexual and sexual reproduction, following the process of sand dune stabilization, we assessed clonal shoots, seedling emergence, soil seed bank density, and soil physical characteristics in mobile and stabilized sand dunes. Controlled field and pot experiments were also conducted to assess germination and seedling emergence in different dune soil types and seed burial depths. The population density of mature C. mongolicum was significantly different after sand dune stabilization. Juvenile density of C. mongolicm was much lower in stabilized sand dunes than mobile sand dune. There was no significant difference in soil seed bank density at three soil depths between mobile and stabilized sand dunes, while the emergence of seedlings in stabilized dunes was much lower than emergence in mobile dunes. There was no clonal propagation found in stabilized dunes, and very few C. mongolicum seedlings were established on stabilized sand dunes. Soil clay and silt content, air‐filled porosity, and soil surface compaction were significantly changed from mobile sand dune to stabilized dunes. Seedling emergence of C. mongolicm was highly dependent on soil physical condition. These results indicated that changes in soil physical condition limited clonal propagation and seedling emergence of C. mongolicum in stabilized sand dunes. Seed bank density was not a limiting factor; however, poor seedling establishment limited C. mongolicum's further natural regeneration in stabilized sand dunes. Therefore, clonal propagation may be the most important mode for population expansion in mobile sand dunes. As a pioneer species C. mongolicum is well adapted to propagate in mobile sand dune conditions, it appears unlikely to survive naturally in stabilized sand dune plantations.     

Effects of Sand Dune Stabilization on the Spatial Pattern of Artemisia ordosica Population in Mu Us Desert,Northwest China

Vegetation patterns are strongly influenced by sand mobility in desert ecosystems. However, little is known about the spatial patterns of Artemisia ordosica, a dominant shrub in the Mu Us desert of Northwest China, in relation to sand fixation. The aim of this study was to investigate and contrast the effects of sand dune stabilization on the population and spatial distribution of this desert shrub. Spatial autocorrelation, semi-variance analysis, and point-pattern analysis were used jointly in this study to investigate the spatial patterns of A. ordosica populations on dunes in Yanchi County of Ningxia, China. The results showed that the spatial autocorrelation and spatial heterogeneity declined gradually, and the distance between the clustered individuals shortened following sand dune fixation. Seedlings were more aggregated than adults in all stage of dune stabilization, and both were more aggregated on shifting sand dunes separately. Spatial associations of the seedlings with the adults were mostly positive at distances of 0–5 m in shifting sand dunes, and the spatial association changed from positive to neutral in semi-fixed sand dunes. The seedlings were spaced in an almost random pattern around the adults, and their distances from the adults did not seem to affect their locations in semi-fixed sand dunes. Furthermore, spatial associations of the seedlings with the adults were negative in the fixed sand dune. These findings demonstrate that sand stabilization is an important factor affecting the spatial patterns of A. ordosica populations in the Mu Us desert. These findings suggest that, strong association between individuals may be the mechanism to explain the spatial pattern formation at preliminary stage of dune fixation. Sand dune stabilization can change the spatial pattern of shrub population by weakening the spatial association between native shrub individuals, which may affect the development direction of desert shrubs.