Groundwater evapotranspiration under psammophilous vegetation covers in the Mu Us northern China

Groundwater is a significant component of the hydrological cycle in arid and semi-arid areas. Its evapotranspiration is an important part of the water budget because many plants are groundwater-dependent. To restore the degraded ecosystems, the need is pressing to further our understanding of the groundwater evapotranspiration (ET_g) in arid and semi-arid areas. This study employed the White method to estimate ET_gat four sites in the Mu Us Sandy Land in northern China, and the four sites are covered by Salix psammophila(SP site), Artemisia ordosica(AO site), Poplar alba (PA site), and Carexenervis(CE site), respectively. The depth of groundwater table and the duration of drainage were taken into account in calculating the specific yield (S_y) to improve the accuracy of the ET_gestimats. Our results showed that from late May to early November 2013 the ET_g were 361.87 (SP site), 372.53 (AO site), 597.86 (PA site) and 700.76 mm (CE site), respectively. The estimated ET_g rate was also species-dependent and the descending order of the ET_g rate for the four vegetation was: C. enervis, P. alba, A. ordosica, and S. psammophila. In addition, the depth of groundwater table has an obvious effect on the ET_g rate and the effect varied with the vegetation types. Furthermore, the evapotranspiration for the vegetation solely relying on the water supply from unsaturated layers above the groundwater table was much less than that for the vegetation heavily relying on the water supply from shallow aquifers.     

Effects of vegetation types on soil water dynamics during vegetation restoration in the Mu Us Sandy Land,northwestern China

The arid and semi-arid northwestern China has been undergoing ecological degradation and the efforts to reverse the ecological degradation have been undertaken for many years. Some shifting dunes have been fixed and the vegetation has been partially recovered in certain areas and the Mu Us Sandy Land in the Ordos Plateau is an example of the success. The present study attempts to reveal the relationships between the vegetation restoration and ecohydrology in the Mu Us Sandy Land. We continuously measured soil water content at 10-min intervals under three vegetation types(i.e., shifting dune, shrub-dominated community, and herb-dominated community) in the Mu Us Sandy Land from April 2012 to October 2013. The results show the infiltration coefficient increased with increased rainfall amount and eventually reached a stable value. Infiltration coefficients were 0.91, 0.64, and 0.74 in the shifting dune, in the shrub-dominated community, and in the herb-dominated community, respectively. Cumulative infiltration and soil texture are two vital factors affecting the depths of rainfall penetration. Only rainfall events larger than 35.0 mm could recharge soil water at the 60–80 cm layer in the herb-dominated community. Our results imply that the expected forward succession of restored vegetation may be destined to deterioration after reaching the climax simply because of following two facts:(1) soil water is mainly retained at shallower layer and(2) plant fine roots mainly distribute in deeper layer in the herb-dominated community.     

Wind-proof and sand-fixing effects of Artemisia ordosica with different coverages in the Mu Us Sandy Land,northern China

Wind erosion is a key global environmental problem and has many adverse effects. The Mu Us Sandy Land of northern China is characterized by an arid climate, where vegetation patches and bare sand patches are usually distributed mosaically, and aeolian activities occur frequently. Vegetation plays a significant role in controlling wind erosion. Artemisia ordosica is the most dominant native plant species in the Mu Us Sandy Land. It is urgent to study the wind-proof and sand-fixing effects of Artemisia ordosica in the Mu Us Sandy Land. This study analyzed the wind-proof and sand-fixing effects of Artemisia ordosica based on the field data of wind regimes, aeolian sediment transport, and surface change of Artemisia ordosica plots with four coverages (denoted as site A, site B, site C, and site D) in the Mu Us Sandy Land during the period from 1 June 2018 to 29 June 2019. The coverages of Artemisia ordosica at site A, site B, site C, and site D were 2%, 16%, 29%, and 69%, respectively. The annual average wind speeds at 2.0 m height above the ground for site A, site B, site C, and site D were 3.47, 2.77, 2.21, and 1.97 m/s, respectively. The annual drift potentials were 193.80, 69.72, 15.05, and 6.73 VU at site A, site B, site C, and site D, respectively. The total horizontal aeolian sediment fluxes during the period from 2-3 June 2018 to 6 June 2019 at site A, site B, site C, and site D were 4633.61, 896.80, 10.54, and 6.14 kg/m, respectively. Site A had the largest surface changes, and the surface changes at site B were significantly weaker than those at site A, whereas the surface changes at site C and site D were minimal. The results indicated that Artemisia ordosica significantly reduced the wind speed, drift potential, aeolian sediment transport, and surface changes. The higher the coverage of Artemisia ordosica is, the more obvious the effects of wind-proof and sand-fixing. Wind erosion would be effectively controlled in the Mu Us Sandy Land if the coverage of Artemisia ordosica is greater than 29%. These results provide a scientific basis for evaluating the ecosystem service function of Artemisia ordosica and the vegetation protection and construction projects in the Mu Us Sandy Land.     

Ecological effect of the plantation of Sabina vulgaris in the Mu Us Sandy Land,China

Vegetation restoration through artificial plantation is an effective method to combat desertification, especially in arid and semi-arid areas. This study aimed to explore the ecological effect of the plantation of Sabina vulgaris on soil physical and chemical properties on the southeastern fringe of the Mu Us Sandy Land, China. We collected soil samples from five depth layers(0–20, 20–40, 40–60, 60–80, and 80–100 cm) in the S. vulgaris plantation plots across four plantation ages(4, 7, 10, and 1...     

毛乌素沙地不同生境主要植物叶性状研究

叶性状与植物的生长对策及资源利用效率密切相关,能够反映植物对环境的适应策略.文中比较分析了毛乌素沙地不同生境中(固定沙地、半固定沙地和流动沙地)8种植物叶性状的差异及其相关关系.结果 表明:1)8种植物叶性状差异显著,流动沙地沙米(Agriophyllum squarrosum)具有较大的比叶面积(SLA)和较小的单位...     

毛乌素沙地南缘沙区水分入渗特征及其影响因素

水分入渗是土壤水分循环的重要环节。为探明毛乌素沙地生物结皮覆盖沙区水分入渗特征及其影响因素,采用双环法测定不同类型地表(裸沙、浅灰色藻类结皮、黑褐色藻类结皮和藓类结皮,依次用BS、LC、DC和MC表示)水分入渗速率及其土壤理化性质。结果表明:1与BS相比,LC、DC和MC样地初始入渗率分别减少了37.7%、59.2%和73.6%,稳定前平均入渗率分别减少了37.5%、62.2%和81.3%,稳定入渗率分别减少了13.6%、67.4%和78.9%,累计入渗量分别减少了25.8%、61.3%和78.6%。2不同类型地表达到稳定入渗所需的时间在3~8 min;相关性分析结果显示,水分入渗速率与砂粒和土壤容重呈正相关关系,与粉粒、黏粒、结皮厚度、结皮抗剪强度、结皮层容重和有机碳含量呈负相关关系。3主成分分析结果表明,黏粒、结皮抗剪强度和土壤容重是影响该地区水分入渗速率的主要因子。因此,生物结皮在沙丘表面的形成和发育过程中,通过改变土壤的理化性质,减缓了该地区水分入渗速率,增加了降水的径流流失风险。     

Estimating aboveground biomass in Mu Us Sandy Land using Landsat spectral derived vegetation indices over the past 30 years

Remote sensing is a valuable and effective tool for monitoring and estimating aboveground biomass （AGB） in large areas.The current international research on biomass estimation by remote sensing technique mainly focused on forests,grasslands and crops,with relatively few applications for desert ecosystems.In this paper,Landsat Thematic Mapper （TM）/Enhanced Thematic Mapper Plus （ETM＋） images from 1988 to 2007 and the data of 283 AGB samples in August 2007 were used to estimate the AGB for Mu Us Sandy Land over the past 30 years.Moreover,temporal and spatial distribution characteristics of AGB and influencing factors of climate and underlying surface were also studied.Results show that：（1） Differences of correlations exist in the fitted equations between AGB and different vegetation indices in desert areas.The modified soil adjusted vegetation index （MSAVI） and soil adjusted vegetation index （SAVI） show relatively higher correlations with AGB,while the correlation between normalized difference vegetation index （NDVI） and AGB is relatively lower.Error testing shows that the AGB-MSAVI model established can be used to accurately estimate AGB of Mu Us Sandy Land in August.（2） AGB in Mu Us Sandy Land shows the fluctuant characteristics over the past 30 years,which decreased from the 1980s to the 1990s,and increased from the 1990s to 2007.AGB in 2007 had the highest value,with a total AGB of 3.352×106 t.Moreover,in the 1990s,AGB had the lowest value with a total AGB of 2.328×106 t.（3） AGB with relatively higher values was mainly located in the middle and southern parts of Mu Us Sandy Land in the 1980s.AGB was low in the whole area in the1990s,and relatively higher AGB values were mainly located in the southern parts of Uxin.In 2007,AGB in the whole area was relatively higher than those of the last twenty years,and higher AGB values were mainly located in the northern,western and middle parts of Mu Us Sandy Land.     

Vulnerability to drought-induced cavitation in shoots of two typical shrubs in the southern Mu Us Sandy Land,China

Salix psammophila and Caragana korshinskii are two typical shrubs in the southern Mu Us Sandy Land of China which are threatened by increasing water deficits related to climate change and large-scale human activities(e.g. coal mining and oil exploitation). In this study, we assessed their vulnerability to xylem embolism and the related anatomical traits in two-year-old regenerated shoots of these two shrubs to understand how they cope with drought environment. We also evaluated the in situ hydraulic safety margins to hydraulic failure from measurements of annual predawn and midday leaf water potentials. The results showed that S. psammophila stems had a higher water transport capacity than C. korshinskii stems. The stem xylem water potentials at 12%, 50% and 88% loss of conductivity were –1.11, –1.63 and –2.15 MPa in S. psammophila, respectively, and –1.37, –2.64 and –3.91 MPa in C. korshinskii, respectively. This suggested that C. korshinskii was more resistant to cavitation than S. psammophila. Compared with S. psammophila, C. korshinskii had shorter maximum vessel length, lower vessel density, smaller conductive area and higher wood density, which may contribute to its more resistant xylem. The in situ hydraulic safety margins indicated that even during the driest periods, both shrubs lived well above the most critical embolism thresholds, and the hydraulic safety margin was wider in C. korshinskii than in S. psammophila, suggesting that the regenerated shoots of both shrubs could function normally and C. korshinskii had greater hydraulic protection. These results provide the basis for an in-depth understanding of the survival, growth and functional behavior of these two shrubs under harsh and dry desert environments.     

毛乌素沙地天然臭柏种群年龄结构

以毛乌素沙地天然臭柏(Sabina vulgaris)种群为研究对象,按水分、地形等立地条件变化,将臭柏种群划分为滩地、沙丘底部、沙丘坡面和沙丘顶部4种生境类型进行实地调查,分析种群的年龄结构及其动态。运用WinDENDRO~(TM)年轮分析系统确定种群个体年龄,建立幼龄个体和成过熟个体的地径与年龄的回归方程,用以推算样地内所有个体的年龄。结果表明:滩地和沙丘底部生境下的臭柏种群10年以下幼龄植株占94%以上,其年龄结构图表现为金字塔型,属扩展种群;沙丘坡面生境下的臭柏种群以21～30年中龄植株为主,年龄结构表现为圆锥型,属稳定种群;沙丘顶部生境下的臭柏种群以51～60年成熟或老龄植株为主,年龄结构表现为倒金字塔型,属衰退种群。     

Biological soil crust distribution in Artemisia ordosica communities along a grazing pressure gradient in Mu Us Sandy Land,Northern China

This study investigated the distribution pattern of biological soil crust (BSC) in Artemisia ordosica communities in Mu Us Sandy Land. Three experimental sites were selected according to grazing pressure gradient. In each experimental site, the total vegetation cover, A. ordosica cover, BSC cover, litter-fall cover, BSC degree of fragmentation, BSC thickness and soil properties were investigated in both fixed and semi-fixed sand dunes and simultaneously analyzed in the laboratory. The results showed that at the same grazing pressure, BSC cover and composition were significantly affected by the fixation degree of sand dunes. In addition, BSC cover in the fixed sand dunes was 83.74% on average, whereas it is proportionally dominated by 28% mosses, 21% lichens, and 51% algae. Meanwhile, BSC cover in the semi-fixed sand dunes was 23.54% on average, which is proportionally dominated by 6.3% mosses, 2.5% lichens, and 91.2% algae. Fine sand, organic matter, and total nitrogen (N) contents in the fixed sand dunes were all significantly higher than those in the semi-fixed sand dunes. Litter-fall cover decreased along the grazing pressure gradient, whereas BSC fragmentation degree increased. Fine sand content decreased along with the increase of grazing pressure, whereas medium sand content increased in both fixed and semi-fixed dunes. The organic matter and total N contents in the no grazing site were significantly higher than those in light and normal grazing sites. However, there were no significant differences between the light and normal grazing sites. In addition, there were also no significant differences in BSC thickness between the light and normal grazing sites in the fixed sand dunes. However, a significant decrease was observed in both BSC cover and thickness in the normal grazing site. The BSC in the semi-fixed dunes was more sensitive to disturbance.     

明代边墙修筑时毛乌素沙地范围探讨

根据野外调查,并结合历史文献记载,对明代毛乌素沙地的范围进行了分析。结果表明:明代时毛乌素沙地边墙一带已经处于沙地之中,其环境为沙地、湖滩交错组成,沙漠早在边墙修筑之初就远在边墙的南面。边墙的修建虽说"草茂之地,筑之于内,使虏绝牧;沙碛之地,筑之于外",这只能代表一种景观的差异,与现今所定义的沙地概念不符,不能用来作为沙地与非沙地的分界线。但当时边墙附近植被盖度应好于现在,多为固定沙丘或者平沙地。     

毛乌素沙地南缘不同林龄人工柠条林土壤渗透性研究

为了探讨不同林龄人工柠条林对土壤渗透性能的影响,以天然草地为对照,以土壤初渗速率,稳渗速率,平均渗透速率和渗透总量表征土壤渗透性,运用主成分分析及散点聚类法对毛乌素沙地南缘不同林龄人工柠条(Caragana korshinkii)林地土壤渗透性进行了研究。结果表明:不同林龄人工柠条林地土壤渗透性能大小依次为:15a>24a>36a>天然草地(CK)。即随着人工柠条林林龄的增加,其土壤渗透性能力逐渐减弱,对照天然草地的土壤渗透能力最小。不同林龄人工柠条林地土壤入渗过程回归模拟结果表明:土壤水分入渗过程符合Kostiakov模型,相关系数在0.8003～0.9535之间,且F检验均达到极显著水平。Kostiakov模型是比较适用于干旱、半干旱区的人工柠条林地土壤入渗特征的模型。。     

近60a毛乌素沙地东缘主要气候要素的多时间尺度变化特征

基于中国气象科学数据共享服务网提供的1954-2013年的气候资料,采用线性倾向分析、累积距平法、Morlet连续复小波变换等方法,探讨了毛乌素沙地东缘年均气温、年降水量和年均相对湿度的年代际变化、周期性及突变特征.结果表明:1)毛乌素沙地东缘的年均气温和年均相对湿度变化趋势较显著,气候倾向率分别是0.25℃/10a和-0.78％/10a,降水量变化呈微弱下降趋势(-7.74mm/10a),但趋势性变化并不显著.2)年均气温、年降水量和年均相对湿度在研究时域上均表现出多时间尺度变化特征,时间序列变化的主周期分别为16a、13a和18a.3)年均气温、年降水量与年均相对湿度相比,突变时间存在2a左右的滞后期;年均气温、年降水量与年均相对湿度在主周期时间尺度下,分别经历了5次、7次和4次正负位相循环,且在2013年以后的短时间尺度上分别处于偏低期、偏少期、偏干期.4)年均气温、年降水量和年均相对湿度在16a、13a和18a时间尺度上的位相结构变化既有相似性,又有差异性,具体表现为气温偏高(低)年(代)对应着降水量和相对湿度的偏少/小(多/大)年(代)的变化规律.     

毛乌素沙地飞播区植被动态变化研究

对毛乌素沙地不同飞播年限的4个播区进行调查研究,通过对盖度、重要值以及生活型的研究和分析,说明飞播对沙地退化植被有明显的改善作用。分析表明:飞播后飞播植被盖度随时间逐年增加,由14%增加到33%,说明飞播后植被得到良好的恢复;飞播后在不同的沙丘部位植被盖度各不相同,但是随着飞播年限的增加沙丘各部位的盖度相差不大;各飞播植物种的盖度和重要值随飞播年限的增加而变化,在飞播后的24年中呈现出不同的消长动态。飞播改良了沙地土壤的性质,使多年生和一年生的草本植物在群落中得以生长,随着飞播年限的增长,飞播群落的结构逐渐复杂,群落更趋于稳定。     

Geochemical weathering of aeolian sand and its palaeoclimatic implications in the Mu Us Desert,northern China,since the Late Holocene

In the semi-arid and arid regions of northern China,geochemical behavior of the aeolian deposit is closely related to climatic and environmental changes,which was used to reconstruct the past history of environmental evolution and possibly forcing mechanisms.However,the related result was still scarce due to the lack of detailed geochemical analysis results in the desert sediments.In the present study,we systematically analyzed the geochemical components and parameters of the paleo-aeolian sand dune and modern mobile sand deposits in the Mu Us Desert and discuss the climatic variation inferred from the paleo-aeolian sand dune during the past 4.2 ka BP.The results indicated that (1) geochemical composition of the sandy deposits were dominated by SiO_2,Al_2O_3 and Na_2O and the deposits probably originated from the widespread upper continental crust (UCC) and were formed by long-term weathering,transport and re-deposition;(2) these sandy deposits were subjected to weaker weathering or uneven weathering under cold and dry conditions,and had highly similar material sources and degrees of weathering and leaching in general;and (3) the direct OSL (Optically Stimulated Luminescence) dating ages and geochemical parameters from the palaeosol-aeolian sand dune indicated that the regional climate change experienced several typically cold and warm intervals.These intervals are 4.2,2.8 ka BP and Little Ice Age and Medieval Warm Period,which probably attributed to periodic variations of the Asian summer monsoonal strength and cold events of the northern Atlantic Ocean in low and high latitudes of the Northern Hemisphere.Our results suggest that the development of the sand dune in the Mu Us Desert provided a suitable archive for understanding the past local climatic change,which is linked to the global climatic change.     

毛乌素沙地东南缘不同类型沙丘土壤水分分布特征

通过对横山县境内毛乌素沙地东南缘的实地考察,根据植被类型和植被覆盖度,将沙丘分为裸露流动沙丘、灌木覆盖沙丘、乔木覆盖沙丘,分别在各类沙丘不同地貌部位实施4 m深度钻孔取样,并进行含水量测试和粒度分析,研究沙地土壤含水量变化。结果表明:对于垂直方向0～4m深度的沙地、灌木和乔木覆盖沙丘平均含水量变化为:丘间洼地>迎风坡>背风坡,而裸露流动沙丘平均含水量变化为:丘间洼地>背风坡>迎风坡;不同类型沙丘在各地貌部位不同层段含水量变化差异明显,变化趋势不统一。沙丘的地貌部位相同,地表的植被类型和覆盖度差异是影响沙地土壤含水量的重要因素,测试结果显示,迎风坡含水量为:灌木覆盖沙丘>乔木覆盖沙丘>裸露流动沙丘;背风坡含水量为:灌木覆盖沙丘>裸露流动沙丘>乔木覆盖沙丘;丘间洼地含水量为:灌木覆盖沙丘>乔木覆盖沙丘>裸露流动沙丘。灌木覆盖沙丘土壤含水量变异系数最大,水分含量在不同层位波动较大,裸露流动沙丘和乔木覆盖沙丘含水量波动差异较小。沙丘上生长的灌木和乔木明显地改变了沙丘含水量的变化特征,灌木比乔木对沙丘含水量及其垂向变化的影响更显著。灌木对地表大气中的粉尘有较强的拦截能力,灌木沙丘平均的粉砂和黏土含量高,灌木的覆盖有利于沙地的土壤化进程和保持沙地水分,在沙地绿化过程中,应充分考虑灌木植物的作用。     

科尔沁沙地青贮玉米蒸散量的估算与分析

为准确估算科尔沁沙地青贮玉米实际蒸散量的变化规律,选用ASCE Penman-Monteith(ASCE-PM)模型计算参考作物蒸散发(ET0);利用双作物系数模型模拟土壤含水率与对应实测值进行统计分析,根据均方根误差、一致性指数、平均绝对误差和Nash-Sutcliffe效率指数4个指标以及回归系数和决定性系数对双作物系数模型进行率定和验证,然后模拟青贮玉米的作物系数,与ASCE-PM模型结合后模拟青贮玉米的蒸散发、棵间土壤蒸发和作物蒸腾规律,并分析其影响因素。结果表明:双作物系数模型准确地模拟土壤含水率和棵间土壤蒸发的变化过程,率定各阶段基础作物系数为0.25、0.9和0.5。棵间土壤蒸发先由播种时峰值下降到较低水平,于收割前有所回升;蒸腾速率除刚出苗和收割前呈单峰变化外大部分时段呈双峰变化,日内变化规律大体为中午高,早晚低,自出苗之日起生长中期后半段处于较高水平,之后逐渐减弱。青贮玉米蒸散量与太阳辐射线性关系最为显著(R=0.643),与气温、空气湿度和风速的相关性依次次之。ASCE-PM模型空气动力项5 d尺度贡献率为27.94%~77.66%,且随风速同增减。综上所述,ASCE-PM模型结合双作物系数可较好估算科尔沁沙地青贮玉米的实际蒸散量,以及棵间土壤蒸发和作物蒸腾量。     

毛乌素沙地生物结皮对土壤温度的影响

土壤温度对作物生长发育、土壤水盐运移、生物的数量与活性、土壤碳平衡等均有较大的影响。为了研究毛乌素沙地生物结皮区和裸沙区土壤温度的差异,于2010年9~11月在陕北毛乌素沙地东南缘神木县圪丑沟地区,选择晴朗天气进行定位观测试验。结果表明: ① 同一剖面深度,生物结皮样地土壤温度的日变化趋势同裸沙样地一致;且从6:00~21:00时每隔3 h,土壤垂直剖面的温度沿着“\” 型、 微“（”型、明显“（”型、“/” 型、微“）”型、“\”型进行周期性变化。② 生物结皮的覆盖极显著降低了地表的土壤温度（[WTBX]P[WTBZ]＜0.01）。③ 生物结皮样地和裸沙样地表层土壤温度变幅最大,随剖面深度的增加土壤温度变化趋缓。当气温和土壤含水量较低时,生物结皮对同一深度土壤温度变化幅度的影响更明显。从垂直剖面角度看,生物结皮降低了土壤温度及其变幅。④ 生物结皮提高了0~25 cm深度土壤温度对气温的敏感程度。表明土壤温度的变化是多因素作用的结果,前人仅根据生物结皮的颜色来判断其对土壤温度的影响是不够的。生物结皮对土壤温度造成影响的主要原因,可能是其改变了土壤表层结构及土壤水分状况。在今后相关研究中如水分蒸发、土壤化学性状的改变等,要特别注意生物结皮的温度效应对这些过程的影响,从而使分析更加客观深入。     

Effects of vegetation cover on recruitment of Ulmus pumila L. in Horqin Sandy Land,northeastern China

Understanding the effects of vegetation cover on seedling survival is helpful for promoting vegetation restoration in environmentally fragile zones. This study was conducted in the desertified, moving sand dunes of Horqin Sandy Land, Inner Mongolia, northeastern China. We hyphothesized that(1) seed density(i.e., number/m2) increases as vegetation cover increases, and(2) there will be more surviving seedlings in locations with higher vegetation covers. Total vegetation cover and initial densities of seeds, germinated seeds and surviving seedlings of Ulmus pumilia were evaluated under various vegetation covers in trying to clarify the effects of vegetation cover on the early stages of the plant life history. In agreement with the first hypothesis, initial seed densities were greater(P<0.05) under higher vegetation covers. The relationship between vegetation cover and initial seed density was represented by a quadratic regression, where a threshold occurred with a vegetation cover of 36%(P<0.05). The higher total vegetation covers, however, did not result in increased densities of germinated seeds(P>0.05), which on average represented 16.7% of initial seed densities. Even more, three months after the study initiation, total vegetation covers were similar(P>0.05) at all positions in the dunes, and they determined a similar number(P>0.05) of surviving seedlings at those positions(i.e. the second hypothesis had to be rejected). The mean number of seed- lings that survived at all positions was only 4.5% of germinated seeds. The number of surviving elm seedlings(0 to 1.7 seedlings/m2) under various vegetations covers(12.2% to 20.8%) at all dune positions by late summer would most likely not contribute to vegetation restoration in the study area.     

围栏禁牧对毛乌素沙地土壤理化特征的影响

过度放牧导致干旱半干旱区毛乌素沙地草地严重退化。通过禁牧措施排除放牧干扰,使草地自然恢复,作为一种低投入的措施在世界各国退化草地生态系统恢复中得到广泛采用。文中对毛乌素沙地三种不同管理类型(持续放牧、围栏5年和围栏16年)土壤理化性状进行了研究,研究结果显示:围栏禁牧5年对0～30cm土壤颗粒组成和容重没有显著影响;围栏禁牧16年0～10cm土壤容重显著小于持续放牧区,而极细沙、粉粒和粘粒含量显著高于持续放牧区;围栏5年显著增加了0～5cm土壤有机碳,而0～30cm的全氮均没有显著增加。围栏16年土壤有机碳较放牧区在0～5cm、5～10cm、10～30cm分别显著增加了231%、81%、55%;全氮含量的变化趋势与之相同。结果表明,围栏5年对土壤粘粉粒、全氮含量的恢复基本没有效果;围栏16年能显著增加表层土壤粘粉粒含量和有机碳、全氮,但土壤碳、氮水平还是在比较低的水平(有机碳:4.30g.kg-1;全氮:0.74g.kg-1),即长期禁牧可以逐渐改善土壤质地和提高土壤肥力。研究结果为半干旱退化沙质草地生态系统的恢复、重建及管理提供科学依据。