Spatio-temporal Variations of Temperature and Precipitation During 1951–2019 in Arid and Semiarid Region, China

Understanding the spatio-temporal variations of temperature and precipitation in the arid and semiarid region of China(ASRC)is of great significance for promoting regional eco-environmental protection and policy-making.In this study,the annual and seasonal spatio-temporal patterns of change in average temperature and precipitation and their influencing factors in the ASRC were analyzed using the Mann-Kendall test,linear tendency estimation,accumulative anomaly and the Pearson’s correlation coefficient.The results showed that both annual average temperature and average annual precipitation increased in the ASRC during 1951–2019.The temperature rose by about 1.93℃and precipitation increased by about 24 mm.The seasonal average temperature presented a significant increase trend,and the seasonal precipitation was conspicuous ascension in spring and winter.The spatio-temporal patterns of change in temperature and precipitation differed,with the southwest area showing the most obvious variation in each season.Abrupt changes in annual and seasonal average temperature and precipitation occurred mainly around the 1990 s and after 2000,respectively.Atmospheric circulation had an important effect on the trends and abrupt changes in temperature and precipitation.The East Asian summer monsoon had the largest impact on the trend of average annual temperature,as well as on the abrupt changes of annual average temperature and precipitation.Temperature and precipitation changes in the ASRC were influenced by long-term and short-term as well as direct and indirect anthropogenic and natural factors.This study identifies the characteristics of spatio-temporal variations in temperature and precipitation in the ASRC and provides a scientific reference for the formulation of climate change responses.

Impacts of Climate Change on Net Primary Productivity in Arid and Semiarid Regions of China

In recent years, with the constant change in the global climate, the effect of climate factors on net primary productivity(NPP) has become a hot research topic. However, two opposing views have been presented in this research area: global NPP increases with global warming, and global NPP decreases with global warming. The main reasons for these two opposite results are the tremendous differences among seasonal and annual climate variables, and the growth of plants in accordance with these climate variables. Therefore, it will fail to fully clarify the relation between vegetation growth and climate changes by research that relies solely on annual data. With seasonal climate variables, we may clarify the relation between vegetation growth and climate changes more accurately. Our research examined the arid and semiarid areas in China(ASAC), which account for one quarter of the total area of China. The ecological environment of these areas is fragile and easily affected by human activities. We analyzed the influence of climate changes, especially the changes in seasonal climate variables, on NPP, with Climatic Research Unit(CRU) climatic data and Moderate Resolution Imaging Spectroradiometer(MODIS) satellite remote data, for the years 2000–2010. The results indicate that: for annual climatic data, the percentage of the ASAC in which NPP is positively correlated with temperature is 66.11%, and 91.47% of the ASAC demonstrates a positive correlation between NPP and precipitation. Precipitation is more positively correlated with NPP than temperature in the ASAC. For seasonal climatic data, the correlation between NPP and spring temperature shows significant regional differences. Positive correlation areas are concentrated in the eastern portion of the ASAC, while the western section of the ASAC generally shows a negative correlation. However, in summer, most areas in the ASAC show a negative correlation between NPP and temperature. In autumn, precipitation is less important in the west, as opposed to the east, in which it is critically important. Temperatures in winter are a limiting factor for NPP throughout the region. The findings of this research not only underline the importance of seasonal climate variables for vegetation growth, but also suggest that the effects of seasonal climate variables on NPP should be explored further in related research in the future.

Urban expansion and intra-urban land evolution as well as their natural environmental constraints in arid/semiarid regions of China from 2000–2018

Rapid urbanization has occurred in arid/semiarid China,threatening the sustainability of fragile dryland ecosystems;however,our knowledge of natural environmental constraints on multiscale urban lands in this region is still lacking.To solve this issue,this study retrieved 15-m multiscale urban lands.Results indicated that urban area increased by 68%during 2000–2018,and one-third of the increase was contributed by only three large cities.The coverage of impervious surface area(ISA) and vegetated area(VA) increased by 16.6%and 1.38%,respectively.Such land-cover change may be helpful in suppressing wind erosion and sand storms.We also found that the newly urban lands had relatively lower ISA and higher VA than the old urban lands,indicating an improved human settlement environment.Strong environmental constraints on urban expansion were identified,with cities in oasis urban environments(OUEs) that had water supply expanding 150% faster than cities in desert urban environments(DUEs).Urban development was also constrained by terrain,with 73% of the ISA expansion occurring in relatively flat areas.Overall,the aggregated pattern of urbanization and the increase in ISA and VA in the newly urbanized lands have improved water-use efficiency and ecological services and benefited desert ecosystem protection in arid/semiarid China.

Aeolian dust transportation and deposition by near-surface winds in arid and semiarid China

Dustfall collections were carried out in April and May 2001 and in March 2002 at six sites in northern China.Our results showed that the total deposition of dust fractions 【250 μm in diameter and the deposition of Fe both decreased exponentially with increasing distances from the source areas,and that the half-attenuation distance (HAD) for dust deposition was about 229 km in this re-gion.The HAD was closely related to the grain-size distribution of the dust,and the 15 to 20 μm fractions had the longest HAD.However,the fractions 【15 μm in diameter can be easily adsorbed to coarse particles and deposited after only short distances,and the HAD for the fractions 15 to 100 μm in diameter showed a power relationship with the grain-size distribution.The HAD for Fe deposition was 233 km,which was a little longer than that of total dust deposition,which suggests that the Fe content is higher in fine particles than in coarse particles,as previous studies have suggested.In addition,our analysis showed that under the control of current climatic conditions,the coarse fractions in dust derived from northwestern China cannot be transported over long distances,instead,it is transported primarily by near-surface winds (【3 km above the ground).The Fe in aeolian dust generated from arid and semiarid regions of China and deposited in the North Pacific region is usually transported by the upper westerlies.

A Case Study of the Impacts of Dust Aerosols on Surface Atmospheric Variables and Energy Budgets in a Semi-Arid Region of China

The authors present a case study investigating the impacts of dust aerosols on surface atmospheric variables and energy budgets in a semi-arid region of China. Enhanced observational meteorological data, radiative fluxes, near-surface heat fluxes, and concentrations of dust aerosols were collected from Tongyu station, one of the reference sites of the International Coordinated Energy and Water Cycle Observations Project (CEOP), during a typical dust storm event in June 2006. A comprehensive analysis of these data show that in this semi-arid area, higher wind velocities and a continuously reduced air pressure were identified during the dust storm period. Dust storm events are usually associated with low relative humidity weather conditions, which result in low latent heat flux values. Dust aerosols suspended in the air decrease the net radiation, mainly by reducing the direct solar radiation reaching the land surface. This reduction in net radiation results in a decrease in soil temperatures at a depth of 2 cm. The combination of increased air temperature and decreased soil temperature strengthens the energy exchange of the atmosphere-earth system, increasing the surface sensible heat flux. After the dust storm event, the atmosphere was dominated by higher pressures and was relatively wet and cold. Net radiation and latent heat flux show an evident increase, while the surface sensible heat flux shows a clear decrease.

全球干旱/半干旱区年代尺度干湿变化研究的进展及思考

干旱/半干旱区气候变化研究一直是广泛关注的前沿科学问题,尤其是气候干湿变化规律及未来的发展趋势。过去大量的研究揭示了全球不同干旱/半干旱区的干湿变化事实和机理,取得了一系列重要进展,IPCC第6次评估报告明确指出未来全球干旱化将加剧,但也存在诸多问题没有得到一致的认识。本文将对全球变暖背景下有关干旱/半干旱区年代尺度干湿变化,特别是年代尺度干旱研究进行梳理,系统评述当前相关研究的现状并提出干旱/半干旱区研究所面临的关键科学问题。

西北干旱半干旱区NDVI季节性变化及其影响因素

研究植被的动态变化及其影响因素,不仅能够揭示植被覆盖动态变化特征与气候变化之间的响应机制,同时对区域的植被恢复以及生态可持续具有重要意义。本文基于MODIS遥感卫星数据,借助变异系数、趋势分析、相关分析与Hurst指数探究了2000—2020年西北干旱半干旱区植被覆盖逐季变化特征、影响因素及未来趋势。结果表明:(1)归一化植被指数(Normalized DifferenceVegetationIndex,NDVI)空间变异程度在冬季偏高,且高波动主要分布在新疆与内蒙古大兴安岭的草地与未利用地区域。(2)NDVI随季节波动较大,在林地与耕地最为明显。(3)NDVI主要为改善趋势,其中,春季改善面积最大(84.63%),冬季最小(72.52%),且林地改善最为显著。(4)各季度NDVI均受地表温度与降水量影响(Significance=0.05),且夏季地表温度与冬季降水量逐年递增对植被生长具有抑制作用。(5)未来NDVI主要呈改善趋势。值得注意的是,退化区域零星分布于新疆塔里木盆地、准噶尔盆地等地区。本研究旨在为西北干旱半干旱区的生态修复与治理,以及局部气候暖湿化的应对提供理论参考。

干旱半干旱地区土壤微生物结皮的生态学意义及若干研究进展

土壤微生物结皮广泛存在于干旱半干旱地区 ,且具有重要的生态学意义。文章对微生物结皮的形成、发育过程的特点 ,以及它对微生境的影响 ,包括对土壤理化性质、风蚀水蚀的抗性、土壤水分时空分布特点、养分及微量元素地球生物化学循环等土壤学过程和对植被的影响与作用等方面的国内外研究进展进行了综述 ,并对一些有争议研究结论进行了分析 ;

半干旱区流域土壤养分分布特征及其与地形、植被的关系

以小流域为单元,以典型横断面为代表,初步分析了黄土高原半干旱区中连川小流域坡顶、坡面和坡脚不同部位土壤养分分布特征及其与地形和植被的关系。结果表明,中连川流域土壤养分全量和速效态都匮乏。在开垦利用条件下,0～20cm土层土壤有机碳、氮、磷、Olsen-P、硝态氮含量在不同坡位的高低顺序:坡面<坡顶<坡脚,显示了土壤养分坡脚富集、坡面和坡顶流失的特征。恢复地表植被后,土壤有机碳、氮的含量较相邻的农田显著提高。草本植被群落对土壤养分(0～20cm)的积累促进作用高于灌木。

沙坡头地区多年降水分布特征、趋势及其变率

应用Mann -Kendall秩统计法和回归分析法 ,检验时间序列上的年降水趋势 ;应用一阶自相关分析法 ,对沙坡头地区多年降水持续性特征进行统计分析。结果表明 ,5a滑动平均曲线所对应区间 196 7— 1972年以及1977— 1982年降水量大于多年平均值 ,而 1983— 2 0 0 0年降水量滑动平均值低于多年平均值的趋势明显。 195 5—1970年的分析时段内 ,降水量每连续递减两年后 ,将稍有回升 ,但总体上趋于下降。从滑动平均计算值来看 ,年降水分布存在时间序列上的非随机因素潜在振荡 ,5a滑动平均值突出了以年为时序单位的降水振荡模式。干旱时段的延长通常在多雨年之前或之后发生 ,尤其在 1978年经历高峰降水以后 ,直至 1985年 ,区内干旱时段的延长颇为显著。

半干旱区全膜覆盖垄上微沟种植对土壤水热及马铃薯产量的影响

根据马铃薯的生长习性调节起垄造沟方式,2012—2014年进行大田定位试验,设置全膜覆盖垄上微沟（垄上营造10cm高,20cm宽的微沟,马铃薯种植在微垄顶部,RMF）、全膜覆盖垄沟种植（RF）和露地平作（CK）3个处理,测定土壤温度、土壤含水量和马铃薯产量,计算≥10℃地积温、作物生育期耗水量、贮水量、水分利用效率等参数,研究全膜覆盖垄上微沟种植对土壤水热环境和马铃薯水分利用效率的影响。结果表明,RMF和RF在平水年（2012年和2014年）可显著提高各生育期和全生育期≥10℃积温,在丰水年（2013年）则与CK无差异。块茎膨大期0-80cm的土壤贮水量RMF比CK低28.20-31.61mm,80-200cm的土壤贮水量RMF高于RF和CK。与CK相比,RMF和RF明显提高马铃薯地上基部茎数、茎分枝数和茎干重；马铃薯产量分别比CK提高60.78%-89.37%和41.91%-73.33%,水分利用效率分别比CK提高49.46%-82.55%和35.62%-65.66%。RMF块茎膨大期的耗水量比CK增加66.52%；在季节性干旱年份,0-200cm土层的土壤耗水量比RF增加14.19%,从而显著提高产量和水分利用效率。

旱作条件下披碱草属植物叶的生理生化特征分析

在无控制的野外旱作条件下,比较了披碱草属6种野生植物在内蒙古干旱与半干旱区生理生化特性,并对同一地区引种的不同种及分布于不同地区的同一种植物进行了对比分析。结果表明,材料XJE1和XJP5能够保持较好的水分状况,具有较高的相对含水量,而GSD4保水能力不及其他几种材料;BJT3和XJP5叶绿素含量较高,而GSD4叶绿素含量较低。渗透调节物质Pro以BJT3、XJP5和GSS2显著高于其他材料,而MDA含量以BJT3相对较高,比XJE1高近3倍;保护酶SOD活性以材料GSD4较高,其次为BJT3,GSS2较低,POD活性以XJP5较高,其次为BJT3,NMN6较低。经隶属函数综合分析发现,披碱草属6种植物中,除GSD4和NMN6之间隶属函数值差异不显著外,其他材料之间都比较显著,其隶属度值由大到小的顺序为XJP5>BJT3>XJE1>GSD4>NMN6>GSS2。并且来自同一地区的披碱草属2种不同植物的生理特征表现一定的趋同,而来自不同地区的同一种植物表现出一定适应性分化。这些结果都表明,植物为了适应不同的生态环境,各种生理生化指标都会进行相应的调节,共同起作用来保护植物免受伤害。

辽西半干旱区垄膜沟种方式对春玉米水分利用和产量的影响

【目的】春玉米是辽西地区的主要作物,其整个生育期需水量较多,但该区降水资源短缺且降水变率大,时空分布不均,有限降水难以满足春玉米高产稳产所需。垄膜沟种可有效汇集天然降水,提高降水资源化程度,开展相关研究以充分有效地利用该区有限的自然降水,提高农田水分利用效率,促进玉米稳产高产。【方法】2007—2013年在辽宁朝阳地区进行玉米垄膜沟种微集雨种植试验,研究不同种植模式对土壤水分、玉米产量和农田水分利用效率的影响。试验设垄膜沟种(沟内不覆盖,T1)、垄膜沟覆秸秆(T2)、垄膜沟覆膜(T3)和传统种植(CK)4种处理,随机区组设计,3次重复。传统种植为垄沟种植,行距50 cm,垄膜沟种方式为沟垄相间排列,沟宽80 cm,垄宽40 cm,垄高15 cm,垄上覆膜为集雨区,沟为种植区,种植2行玉米。各处理种植密度为52 500株/hm2左右,种肥为磷酸二铵(375 kg·hm-2,N 18%,P2O5 46%),拔节初期追施尿素(375 kg·hm-2,N 46%)。【结果】垄膜沟种微集雨种植可有效汇集天然降雨,2009年和2010年玉米出苗率分别提高13.0%和14.9%,出苗时间提前1—2 d。前期长时间无有效降雨的情况下,一场有效降雨过后,土壤贮水量增加幅度依次为T2>T1>CK>T3,T1和T2种植区水分入渗深度至少达到60 cm,而CK水分入渗深度只有40 cm,产流效率为61%,T1和T2蓄墒增加率分别为72%和88%。各处理生育期间土壤水分平均值从大到小依次为T2>T1>T3>CK,其值分别为140.93、135.27、127.85和118.98 mm,较对照分别增加18.45%、13.69%和7.46%。2007—2013年,T1—T3产量比对照分别增产24.31%—32.58%、9.95%—17.81%、32.12%—37.16%、16.58%—27.96%、2.50%—9.40%、10.85%—29.33%和4.14%—17.95%,T1、T2和T3较对照平均增产幅度分别为14.52%、20.01%和23.44%。2007—2012年,T1—T3水分利用效率较对照分别增加24.66%—36.07%、14.12%—23.73%、38.34%—53.89%、29.07%—35.68%、1.20%—19.60%和9.02%—32.55%,T1、T2和T3水分利用效率较对照平均增加幅度分别为20.39%、27.94%和28.02%。在相对干旱年份,产量和水分利用效率增加幅度较大。【结论】通过连续7年进行旱作农田垄膜沟种微集雨种植试验,明晰了该技术模式在辽西半干旱地区的集雨、蓄水和保墒效果,有效减轻春季干旱对春播保苗和幼苗生长造成的不利影响,丰富了辽西半干旱地区旱作集水农业的理论基础。通过该项技术的推广应用,可有效提高该区降水资源利用率和农田水分利用效率,使玉米稳产高产,从而促进该区旱作农业健康、可持续发展。该项研究对中国北方旱作集水农业的发展也具有重要的借鉴意义。

旱地全膜覆土穴播对春小麦耗水、产量和土壤水分平衡的影响

目的干旱、降水供需错位和春季低温是制约西北黄土高原丘陵沟壑区春小麦生产的主要因子,如何最大限度保蓄自然降水、实现水分的跨季节利用,则是该区春小麦产量稳定提高的根本途径。本文在大田定位观测的基础上,揭示全膜覆土穴播对西北黄土高原旱作春小麦季节性耗水特征、产量、水分利用效率和休闲期土壤水分补给的影响,并评判其年际土壤水分平衡效应。方法试验于2011—2013年在西北黄土高原半干旱区的甘肃省农业科学院定西试验站进行(104°36′E,35°35′N),以春小麦陇春27号为试验材料,设全膜覆土穴播(FMS)、地膜覆盖穴播(FM)和露地穴播(CK)3个处理,测定春小麦不同生育时期的土壤含水量、生物量、产量和产量构成因子,计算休闲效率、耗水量、水分利用效率、收获指数等指标。结果 2011和2012年3个处理的春小麦耗水量无显著差异,但2013年FMS耗水量显著高于CK。FMS和FM可增加春小麦苗期到孕穗期耗水,且此阶段的耗水量在干旱年份分别较CK增加27.2%和9.6%,在丰水年份分别较CK增加52.2%和44.6%。虽然FMS和FM在各生育期的耗水量无显著差异,但FMS在丰水年(2012年和2013年)的耗水量较FM有增加趋势,且这一效果在2013年尤为明显。FMS和FM在休闲期可补充0—80 cm土层土壤水分25.4和18.3 mm,比CK分别低2.2和9.3 mm;补充80—200 cm土层土壤水分78.0和71.0 mm,比CK分别高30.0和23.1 mm;与2011年播前相比,种植3年春小麦后0—200 cm土层的土壤贮水量FMS增加了23.8 mm、FM增加了22.5 mm、CK增加了12.4 mm。FMS的休闲效率为30.5%—52.6%,比CK高12.8%—109.5%,比FM高4.5%—40.9%。FMS的穗粒数、千粒重等产量构成因子均显著高于CK(P<0.05);收获指数为0.4—0.5,比CK高32.5%。FMS的产量为1 750—3 180 kg·hm-2,水分利用效率为5.5—11.5 kg·hm-2·mm-1,分别比CK增加40%—220%、27%—239%,而且干旱年份的增加幅度更高。在干旱的2011年,FMS处理的产量较FM增加26.2%,水分利用效率提高28.2%;在丰水的2013年,FMS处理的产量较FM增加20.9%,水分利用效率提高14.8%,两年均达到显著差异水平,表明FMS较FM具有更明显的丰水年份增产、干旱年份适应干旱胁迫的潜力,能够实现该区春小麦生产稳产高产的目标。结论西北黄土高原半干旱区FMS种植模式有效提高了春小麦播前和生长前期的土壤贮水量,并使春小麦苗期—孕穗期的作物耗水量显著升高,增加春小麦穗粒数,扩大籽粒产量库容和促进灌浆,显著提高春小麦产量和水分利用效率;并在休闲期完全补充春小麦生育期消耗的0—200 cm土壤水分,保持春小麦田的土壤水分年际平衡。

全球气候变化下的半干旱区相对湿度变化研究

为揭示全球气候变化下半干旱区空气相对湿度的变化规律,利用线性回归分析、多元线性相关分析以及M-K检验法对吉林省西部5个站点的1953年以来的相对湿度、气温、降水和风速资料进行了研究.结果表明:相对湿度的年变化曲线呈双峰型,相对湿度的最大值出现在8月,次大值出现在1月,最小值出现在4月,次小值出现在10月.夏、秋季的相对湿度较大,而春、冬季的相对湿度较小.近50年,年平均相对湿度及春、夏、秋、冬四季的相对湿度在波动中下降,下降趋势不显著;但是9月和10月的平均相对湿度下降显著.影响相对湿度变化的主要因子是温度和降水,风速也起一定的作用.相对湿度的变化与温度和风速变化呈负相关关系,与降水变化呈正相关关系.

秸秆还田对半干旱区农田土壤养分含量及玉米光合作用的影响

为了提升和保育辽西半干旱区农田土壤质量,采用盆栽试验的方式探讨了不同处理方式、不同用量玉米秸秆还田对土壤养分含量的影响。结果表明,秸秆还田后,其土壤含水量比对照组提高了3%~7%;有机质含量比对照组提高幅度为1.9%~19%;全氮含量比对照组提高幅度为0.7%~14.4%;速效磷含量比对照组提高了2.51~14.75 mg/kg;速效钾含量比对照组提高了7.33~188.07 mg/kg;碱解氮含量比对照组提高了8.46mg/kg;净光合速率比对照组提高了3~11.03 CO2μmol/（m2.s）;秸秆还田可以缓解土壤碱化。

干旱半干旱地区土壤矿物组成特征及其环境意义

对处于干旱、半干旱地区的甘肃省15个地点的灰钙土、栗钙土、黑垆土、灰褐土和黄绵土等不同类型土壤剖面进行了机械组成分析、矿物组成显微鉴定和粘土矿物X射线衍射分析．结果表明:土壤机械组成以粉砂为主,粘粒次之;栗钙土、灰钙土、黑钙土和灰褐土等干旱地区典型土壤中表层的粘粒质量分数相对较低,土壤原生矿物组成以石英为主,绿帘石等蚀变矿物质量分数较高,次生矿物含有较高的石膏和方解石等;粘土矿物主要为伊利石、绿泥石、高岭石和蒙脱石．土壤机械组成、矿物组成和粘土矿物组成表明:干旱、半干旱地区土壤为黄土母质,土壤形成条件为碱性环境、较弱的淋滤作用和干冷气候,近代强烈的风蚀作用(或沙尘暴)和大气污染对土壤有一定程度的改造．

辽西半干旱区几种人工林生态系统涵养水源功能研究

从森林生态系统树冠截留降雨、枯落物持水及土壤蓄水 3个层次对辽西半干旱区 5种人工林生态系统的涵养水源功能进行了定量研究 .结果表明 ,各人工林生态系统树冠对降雨的平均截留率为1 4 5 8%～ 37 1 9% ,依次为沙棘林 >油松沙棘混交林 >杨树沙棘混交林 >油松纯林 >杨树纯林 ;枯落物层厚度为 1 6～ 4 1cm ,枯落物贮量为 1 890 4～ 6 4 2 5 2kg·hm-2 ,枯落物层厚度和贮量均为沙棘林 >油松沙棘混交林 >杨树沙棘混交林 >油松纯林 >杨树纯林 ,枯落物最大持水量取决于枯落物贮量及其最大持水率 ,枯落物最大持水量为 5 95 7 7～ 1 9332 9kg·hm-2 ,依次为沙棘林 >油松沙棘混交林 >杨树沙棘混交林 >油松纯林 >杨树纯林 ;各人工林生态系统 0～ 4 0cm土壤层非毛管蓄水量为 2 3 70～ 37 85mm ,依次为沙棘林 >杨树沙棘混交林 >油松沙棘混交林 >杨树纯林 >油松纯林 .在 5种人工林生态系统中 ,沙棘林的涵养水源功能最好 。

浑善达克沙地不同植被下的土壤水分状况

浑善达克沙地的中东段阳坡近裸的流动风沙土 0 - 1 0cm土层整个生长季内平均含水量较低、波动也比较大 ,而在 1 0cm以下则基本稳定在 3%左右 ,尤其是深层。丘间低地草本群落下的土壤湿度随深度增加变化较大 ,2 0cm以上土层含量较高 ,40 - 5 0cm土层的含水量最低 ,波动也剧烈 ,90cm以下达裸沙含水量水平。阴坡灌丛下 ,最低土壤含水量出现在 70 -90cm土层 ,深层土壤含水量长期稳定在 1 .5 %左右。这说明植物的生长使根层土壤含水量下降 ,而且不同植物利用水的土层及利用土壤水的量不同。这可能是引起流动风沙土向固定风沙土转变过程中地表植被演替及决定地区顶级群落的主要原因。在干旱半干旱地区 ,植被影响着降水在土层中的分布及地表的蒸散条件 ,使土壤有效水向浅层分配。而降水在土壤不同深度的分配及入渗深度 ,决定着地表植被的生活型 ,从而影响地表植被的演替方向及顶级类型。需水量较大的灌丛在沙丘阴坡能形成稳定的群落 ,是由于沙丘为植物避免干旱胁迫 ,延长在干旱季节的生存时间创造了条件 ,因此 ,沙丘是沙地的重要环境资源 ,尤其是高大沙丘 ,在这类地区的防风固沙中具有重要的作用。