人工小叶锦鸡儿(Caragana microphylla)灌丛土壤水分动态研究

采用由植被空间序列推断时间系列的方法 ,分析了 1984、1987、1995和 1999年建立的人工小叶锦鸡儿固沙植被土壤水分的时空变化特征 .结果表明 ,受沙地土壤机械组成的影响 ,沙地土壤组成以物理性沙粒为主 ,>0 .0 1mm沙粒占 97%以上 ,凋萎湿度为 1.5 5 % ,田间持水量为 5 .5 % ,土壤最大有效水为3.95 % .随着固沙植被优势度的增加 ,小叶锦鸡儿灌丛下土壤含水量持续下降 ,1984年建立的植被区土壤含水量明显低于 1999年建立的植被区 ;在年内土壤水分季节变化中 ,4个阶段植被区土壤水分状况在 4～6月不断降低 ,到 6月达到最低值 ,7～ 10月逐渐回升 ;对于建立较早的植被区 (1984和 1987年 ) ,土壤水分垂直变化表现出随着土层深度的增加 ,土壤含水量逐层递减的趋势 ,特别是 70cm下土层中 ,土壤含水下降明显 ,含水量低于凋萎湿度 ;由于对根际区域土壤水分的利用 ,加剧了固沙植被区深层土壤 (70cm下 )水分的亏缺 ,进而影响植被物种的组成 ,随着小叶锦鸡儿灌丛年龄的增加 ,浅根性植物所占比重增加 .

Interspecific Transition Among Caragana microphylla, C. davazamcii and C. korshinskii Along Geographic Gradient. Ⅰ. Ecological and RAPD Evidence

The former plant population survey has shown that three genetically-related species, Caraganamicrophylla Lam., C. davazamcii Sancz. and C. korshinskii Kom., form a geographical replacement series inNei Mongol Plateau. The present study on population distribution, taxonomy, morphology, development andgenetic structure demonstrated that the geographical distribution of these three species was successiveand in gradual change, thus forming a geographical cline which extended from the east to the west of NeiMongol Plateau. With an analysis of climate change over time, it was considered that the formation of thisgeographical cline was a result of plant adaptation to its natural environment.

Interspecific Transition Among Caragana microphylla, C. davazamcii and C. korshinskii Along Geographic Gradient. Ⅱ. Characteristics of Photosynthesis and Water Metabolism

The characteristics of photosynthesis and water metabolism of Caragana microphylla Lam.,C. davazamcii Sancz. and C. korshinskii Kom. populations in different sites (117.6o-105.7o E, 44.6o-38.8o N)were studied. (1) From the east to the west, the responses of the three species to photosyntheticallyavailable radiation (PAR) in net photosynthesis rate increased, the relative humidity of the air whichcorresponded to the occurrence of maximum photosynthesis rate decreased, and the corresponding airtemperature increased. Along the same gradient, the before-noon superiority of the photosynthesis be-came evident, and the photosynthesis rate and the light use efficiency (LUE ) increased, while the transp-iration rate decreased, thus the water use efficiency (WUE ) increased notably, and the leaf water contentdecreased gradually. From the east to the west, the plants took a water-saving strategy step by step withhigher photosynthesis rate and lower transpiration rate. These physiological changes in the plants wereadaptable to the conditions of light, temperature and humidity in the habitat of the plants, and might be thebiological foundation for the geographical transition among C. microphylla , C. davazamcii and C. korshinskii.(2) The adaptation of photosynthetic system of C. microphylla , C. davazamcii and C. korshinskii to PAR, airhumidity and temperature exhibited the interspecific continuity, which was consistent with theenvironmental gradient. In different species and different sites, the diurnal changes of net photosynthesisrate, the daily cumulative value of net photosynthesis, the diurnal changes of transpiration rate, the dailycumulative value of transpiration, the water use efficiency and the diurnal changes of leaf water contentvaried with longitudinal descent (from the east to the west). The characteristics of photosynthesis andwater metabolism indicated that the geographical transition among C. microphylla , C. davazamcii and C.korshinskii was in gradual change, and these three species formed a geographical cline.

内蒙古高原小叶锦鸡儿(Caragana microphylla)中间锦鸡儿(C．davazamcii)和柠条锦鸡儿(C．korshinskii)的遗传多样性及遗传关系

采用RAPD技术对10个具较大地理跨度的小叶锦鸡儿、中间锦鸡儿和柠条锦鸡儿种群的遗传多样性和遗传关系进行了研究。共检测到678个位点,多态条带比率(PPB)为100%;特有位点41个,占6.05%。总体上3种锦鸡儿的遗传多样性表现出自东向西递减的趋势,分析表明其与生长地点年均气温呈显著负相关。AMOVA表明:3种锦鸡儿种间变异只占总体变异的6.08%,且显著性检验表明这种变异不显著;种内种群间的变异占总变异的11.90%;总变异的主要部分来自种群内部(82.02%)。3种锦鸡儿各种群总体分析结果表明:种群内变异比率Hpop/Hsp为0.8013,基因分化系数Gst为0.1603,种群每代迁移数Nm为2.6192,显示种群间存在一定强度的基因流,3种锦鸡儿间表现为异交性。3种锦鸡儿多样性高低及种群聚类分布格局都表现出一定的地理连续性。

Soil exchangeable base cations along a chronosequence of Caragana microphylla plantation in a semi-arid sandy land,China

As a pioneer leguminous shrub species for vegetation re-establishment, Caragana microphylla is widely distributed in the semi-fixed and fixed sandy lands of the Horqin region, North China. C. microphylla planta- tions modify organic carbon （SOC）, nitrogen （N） and phosphorus dynamics, bulk density and water-holding capacity and biological activities in soils, but little is known with regard to soil exchange properties. Variation in soil ex- changeable base cations was examined under C. microphylla plantations with an age sequence of 0, 5, 10, and 22 years in the Horqin Sandy Land, and at the depth of 0-10, 10-20, and 20-30 cm, respectively. C. microphylla has been planted on the non-vegetated sand dunes with similar physical-chemical soil properties. The results showed that exchangeable calcium （Ca）, magnesium （Mg）, and potassium （K）, and cation exchange capacity （CEC） were significantly increased, and Ca saturation tended to decrease, while Mg and K saturations were increased with the plantation years. No difference was observed for exchangeable sodium （Na） neither with plantation years nor at soil depths. Of all the base cations and soil layers, exchangeable K at the depth of 0-10 cm accumulated most quickly, and it increased by 1.76, 3.16, and 4.25 times, respectively after C. microphylla was planted for 5, 10, and 22 years. Exchangeable Ca, Mg, and K, and CEC were significantly （P〈0.001） and positively correlated with SOC, total N, pH and electrical conductivity （EC）. Soil pH and SOC are regarded as the main factors influencing the variation in ex- changeable cations, and the preferential absorption of cations by plants and different leaching rates of base cations that modify cation saturations under C. microphylla plantation. It is concluded that as a nitrogen-fixation species, C. microphylla plantation is beneficial to increasing exchangeable base cations and CEC in soils, and therefore can improve soil fertility and create favorable microenvironments for plants and creatures in the semi-arid sandy land ecosystems.

Variation in soil water content to rainfall under Caragana microphylla shrub in Horqin Sandy Land

In order to investigate the spatio-temporal variability of soil water content to rainfall under Caragana microphylla shrub in Horqin Sandy Land,a plot of 25 m × 25 m,where there were 6 shrub canopies of C. microphylla,was sited for measuring soil water content at two soil layers of 0-20 cm (top layer) and 20-40 cm (lower layer). Soil water content was measured on the 1st,5th,10th and 15th day after a 42 mm rainfall in Naiman of Inner Mongolia. The results showed that soil water contents at both layers under C. microphylla shrub were gradually decreased after the rain. Soil water content at the top layer outside the shrub canopy was higher than that inside the shrub canopy within 5 days,and became similar inside and outside the shrub canopy on the 10th day after the 42 mm rainfall,and it was lower outside than that inside the shrub canopy on the 15th day. The soil water content at lower layer in the area without shrubs was higher than that under shrub canopy all along. All the measured values of soil water content can be fitted to a variogram model. There was significant autocorrelation of the values of soil water content between top layer and lower layer,except for the fourth measured values of soil water content at top layer. The range and spatial dependence of soil water content at top layer were lower than that at lower layer.

A Leguminous Shrub (Caragana microphylla) in Semiarid Sandy Soils of North China

Caragana microphylla Lam., a pioneer leguminous shrub species for vegetation re-establishment, is widely distributed in the semi-fixed and fixed sandy lands of the Horqin region. Some soil chemical and physical properties were measured under the canopy of C. microphylla and in the adjacent open areas to determine the effects of individual shrubs on soil properties. The influence of isolated C. microphylla on chemical and physical properties of the topsoil was significantly different between plots under the shrub canopy and in the shrub interspaces. Beneath the shrub canopy greater amounts of fine particle fractions, a higher water-holding capacity, and a lower bulk density, as well as higher aboveground and belowground litter biomass were found. Soil organic C and total N concentrations were 23%-31.6% and 14%-27.2% higher under the shrub canopies than in the shrub interspaces, respectively, giving rise to 'islands of fertility'. In a desertified sandy grassland ecosystem, C. microphylla was believed to play a major role in organic C sequestration, N accumulation, and the hydrologic cycle. Additionally, it has been found to be of ecological importance for vegetative restoration and reversal of desertification.

The response of Caragana microphylla seedlings to water table changes in Horqin Sandy Land,China

This paper focuses on the growth response of Caragana microphylla seedlings to changes of artificially controlled water table in Horqin Sandy Land, China. Monitoring results of soil water content shows that soil moisture is closely correlated to groundwater depths. Soil volumetric water increased rapidly when close to water sources and finally stabilized in a saturated state. The soil moisture trend of CK （control） increased gradually at 0-50 cm of soil depth then decreased to 4% below 50 cm soil depth. C. microphylla can adapt to different soil environments by changes in ecological and physiological characteristics. By comparing the ecological characteristics of C. microphylla seedlings at various water tables, we found that a shallow water table of 40 cm depth inhibited seedling groundwater depth of 120 em was more advantageous for plant growth because of weak ecological characteristics. A height and canopy growth of C. microphylla seedlings. During the first two years, the most suitable water depth for root biomass was 120 cm, and 180 cm for root length. The growth of vertical roots is positively correlated with groundwater depth, and root thickness is the determinate factor for root biomass while the fine root is the determinate factor for root length. A thick root would grow much more in a natural drought environment while access to ground water promotes the growth of fine roots.

Stable isotopes reveal varying water sources of Caragana microphylla in a desert-oasis ecotone near the Badain Jaran Desert

Understanding the variation in a plant’s water sources is critical to understanding hydrological processes in water-limited environments. Here, we measured the stable-isotope ratios(δ18 O) of xylem water of Caragana microphylla, precipitation,soil water from different depths, and groundwater to quantitatively analyze the proportion of water sources for the shrub.We found that the water sources of C. microphylla differed with the plant’s ages and the seasons. The main water source for young shrubs was upper-soil water, and it showed significant changes with seasonal precipitation inputs. In summer,the proportion contributed by shallow water was significantly increased with increased precipitation inputs. Then, the contribution from shallow-soil water decreased with the decline in precipitation input in spring and autumn. However, the adult shrubs resorted to deep-soil layers and groundwater as the main water sources during the whole growing season and showed much less seasonal variation. We conclude that the main water source of the young shrubs was upper-soil water and was controlled by precipitation inputs. However, once the shrub gradually grew up and the roots reached sufficient depth, the main water sources change from the upper-soil layer recharged by precipitation to deep-soil water and groundwater, which were relatively stable and abundant in the desert ecosystem. These results also suggest that desert shrubs may be able to switch their main water sources to deep and reliable water sources as their age increases, and this adjustment to water availability carries significant importance for their acclimation to the desert habitat.

Effects of Caragana microphylla plantations on organic carbon sequestration in total and labile soil organic carbon fractions in the Horqin Sandy Land, northern China

Afforestation is conducive to soil carbon（C） sequestration in semi-arid regions. However, little is known about the effects of afforestation on sequestrations of total and labile soil organic carbon（SOC） fractions in semi-arid sandy lands. In the present study, we examined the effects of Caragana microphylla Lam. plantations with different ages（12-and 25-year-old） on sequestrations of total SOC as well as labile SOC fractions such as light fraction organic carbon（LFOC） and microbial biomass carbon（MBC）. The analyzed samples were taken from soil depths of 0–5 and 5–15 cm under two shrub-related scenarios： under shrubs and between shrubs with moving sand dunes as control sites in the Horqin Sandy Land of northern China. The results showed that the concentrations and storages of total SOC at soil depths of 0–5 and 5–15 cm were higher in 12-and 25-year-old C. microphylla plantations than in moving sand dunes（i.e., control sites）, with the highest value observed under shrubs in 25-year-old C. microphylla plantations. Furthermore, the concentrations and storages of LFOC and MBC showed similar patterns with those of total SOC at the same soil depth. The 12-year-old C. microphylla plantations had higher percentages of LFOC concentration to SOC concentration and MBC concentration to SOC concentration than the 25-year-old C. microphylla plantations and moving sand dunes at both soil depths. A significant positive correlation existed among SOC, LFOC, and MBC, implying that restoring the total and labile SOC fractions is possible by afforestation with C. microphylla shrubs in the Horqin Sandy Land. At soil depth of 0–15 cm, the accumulation rate of total SOC under shrubs was higher in young C. microphylla plantations（18.53 g C/（m^2·a）; 0–12 years） than in old C. microphylla plantations（16.24 g C/（m^2·a）; 12–25 years）, and the accumulation rates of LFOC and MBC under shrubs and between shrubs were also higher in young C. microphylla plantations than in old C. microphylla plantations. It can be concluded that the establishment of C. microphylla in the Horqin Sandy Land may be a good mitigation strategy for SOC sequestration in the surface soils.

ISSR analysis of Caragana microphylla(Leguminosae) in different temperature gradients

Caragana microphylla is the most dominant and constructive shrub species in the Horqin Sandy Land of northeastern China. We evaluated the level of genetic variation within and among C. microphylla populations sampled from three different temperature gradients in the Horqin Sandy Land by using inter-simple sequence repeat polymorphism （ISSR） molecular markers. The results show that eight ISSR primers generated 127 bands, of which 123 （96.85%） were polymorphic. At the species level, genetic diversity was relatively high （P = 96.85%, h = 0.3143, I = 0.4790）. The highest genetic diversity was observed in the Subp6 population from low temperature regions, whereas the lowest diversity was found in the Subp2 population from high temperature regions. Six populations of C. microphylla clustered into two clades. These results have important implications for restoring and managing the degraded ecosystem in arid and semi-arid areas.

Microclimate Effect of Artificial Caragana microphylla Communities in Horqin Sandy Land

Caragana microphylla is one of the key species for vegetation restoration in Horqin Sandy Land. Adopting field investigation and outdoor experiments,the microclimate effect of artificial C. microphylla communities with different restoration years were studied by observing wind velocity,air temperature,relative humidity and soil temperature. The results show that:( 1) Caragana microphylla community has an obvious wind-breaking effect near ground surface. Compared with shifting dunes,the wind velocity in the 6-year-old and 11-year-old C. microphylla shrubs at the height of 30 cm separately decreases by 71. 9% and 76. 0%.( 2) Mean daily temperature in the 6-year-old and 11-yearold C. microphylla communities is 3. 7 ℃ and 4. 9 ℃ lower than in shifting dunes,respectively.( 3) The relative humidity of air in the Caragana microphylla shrubs is higher than in shifting dunes.( 4) Soil temperature in C. microphylla plantation is lower than in shifting dunes. These results are significant in further exploring material and energy exchange near surface layer of artificial vegetation in the extremely arid condition.

基于ITS序列和trnL-F序列探讨小叶锦鸡儿、中间锦鸡儿和柠条锦鸡儿的种间关系

中间锦鸡儿CaraganadavazamciiSancz.的分类处理一直存在争议,它与小叶锦鸡儿C.microphyllaLam.和柠条锦鸡儿C.korshinskiiKom.的关系尚不清楚。该种被处理为一个独立的种或后两个种的变种。本文利用ITS序列和叶绿体trnL-F序列,综合形态和地理分布,探讨了中间锦鸡儿的起源及与另外两个种的种间关系。结果显示,中间锦鸡儿的trnL-F序列与小叶锦鸡儿完全一致,而与柠条锦鸡儿有明显差异。中间锦鸡儿的ITS序列高度纯合,不支持该种可能是杂交起源的假设。相反,另外两个种的ITS序列均出现多个位点杂合,克隆后均得到2种不同的序列。中间锦鸡儿的ITS序列与小叶锦鸡儿2种序列中的1种完全一致。该结果表明,中间锦鸡儿可能作为亲本之一参与了小叶锦鸡儿的杂交起源,或者基因流是造成这两个种形态相似的主要原因。中间锦鸡儿与柠条锦鸡儿形态上的相似可能是趋同进化的表现。

小叶锦鸡儿根瘤菌的分离及其16S rDNA PCR-RFLP分析

对辽宁地区与小叶锦鸡儿共生的根瘤菌资源进行了初步调查。采自5个不同地区样品的根瘤,通过分离、纯化、回接验证等试验共获得65株供试根瘤菌菌株。进一步选用4种限制性内切酶对供试根瘤菌进行了16S rDNA PCR-RFLP研究,结果表明其系统发育地位位于中慢生根瘤菌属(Mesorhizobiumspp.),并在96%相似性水平上分为5个不同的类群,分别由相应的rDNA图谱组合代表。丰富度及频度分析表明,组合15是辽宁省的优势群,组合18丰富度居第二位,但频度最高,也是辽宁省的主要类群。

小叶锦鸡儿基因组DNA的提取及AFLP反应体系的建立

以小叶锦鸡儿幼嫩叶片为材料,采用改良的SDS法提取其基因组DNA,通过优化AFLP技术体系中的几个主要因素,建立了适合小叶锦鸡儿的AFLP银染反应体系。改良的SDS法能通过在提取液中加入β-巯基乙醇防止氧化、加入PVP去除酚类等物质,获得满足AFLP分析要求的纯度高、完整性好的基因组DNA;用EcoRⅠ和M seⅠ37℃双酶切4 h后可以将500 ng的基因组DNA完全切开。酶切产物和接头经16℃连接过夜后,用带有1个选择性碱基的引物和带有3个选择性碱基的引物分别进行预扩增和选择性扩增,扩增产物经变性聚丙烯酰胺凝胶电泳分离,用AgNO3染色,得到了清晰的指纹式样。小叶锦鸡儿AFLP反应体系的建立为利用该技术研究小叶锦鸡儿的遗传多样性奠定了实验基础。

采煤沉陷区模拟土壤侵蚀胁迫对灌木生理生长特性的影响

【目的】探究半干旱地区采煤活动造成的土壤侵蚀对北沙柳Salix cheilophila、小叶锦鸡儿Caragana microphylla生长生理特性的影响,阐明植物在逆境胁迫下的适应性及生存策略。【方法】在野外原位试验条件下,对北沙柳、小叶锦鸡儿根部进行原位根系断裂试验来模拟土壤侵蚀胁迫,设置对照组(CK)和轻度胁迫(S1)、中度胁迫(S2)和重度胁迫(S3)四种不同程度的土壤侵蚀,测定了不同胁迫处理下两种灌木的生长指标和生理指标变化,并使用模糊数学隶属函数综合评价其抗逆性。【结果】土壤侵蚀胁迫显著抑制北沙柳和小叶锦鸡儿的株高、冠幅、枝条长度和枝条直径,且随着侵蚀胁迫程度增大,抑制程度越明显;北沙柳叶片叶绿素含量随着土壤侵蚀胁迫程度增大而降低,且随胁迫时间延长呈逐渐降低趋势,而小叶锦鸡儿的叶绿素含量在胁迫后期恢复至侵蚀胁迫前期;北沙柳的丙二醛含量随胁迫时间的延长呈先降低后升高趋势,而小叶锦鸡儿的丙二醛含量呈先升高后降低趋势;侵蚀胁迫后期北沙柳和小叶锦鸡儿叶片超氧化物歧化酶活性、过氧化物酶活性和过氧化氢酶活性升高;隶属函数分析显示,在土壤侵蚀环境中,小叶锦鸡儿抗逆性最强,北沙柳次之。【结论】小叶锦鸡儿对采煤沉陷区土壤侵蚀的破坏致损效应具有更好的抵抗力和恢复力,更适于干旱、半干旱矿区的生态修复与植被建设。

不同组合TMR日粮对滩湖杂代羔羊饲喂效果对比分析

试验旨在研究日粮中南瓜籽壳粉、柠条粉、芦苇草粉不同组合对滩湖杂代羔羊生长性能、血液生化指标的影响。选择体重25kg左右、体况较好的断奶公羔羊57只,随机分为3组,每组19只,每只羔羊为1个重复。试验分为前后两期:试验1组试验前期日粮中南瓜籽壳粉、柠条粉、芦苇草粉分别为15%、15%、7%,试验后期分别为15%、10%、5%;试验2组试验前期日粮中南瓜籽壳粉、柠条粉、芦苇草粉分别为10%、11%、14%,试验后期分别为10%、7.5%、11.0%;试验3组试验前期日粮中南瓜籽壳粉、柠条粉、芦苇草粉分别为20%、10%、7%,试验后期分别为20%、7%、3.5%。预试期10d,正式试验期90d。结果显示:各组羔羊末重、平均日增重、平均日采食量、料重比差异均不显著(P>0.05),但以试验1组平均日增重最高,料重比最低。试验2组羔羊血清白蛋白(ALB)、免疫球蛋白M(IgM)含量显著高于其他两组(P<0.05),肌酐(CREA)含量显著高于试验3组(P<0.05)。综合增重情况和饲料成本,试验1组平均日收益最高,试验3组次之,试验2组最低。研究表明,前期以15%南瓜籽壳粉+15%柠条粉+7%芦苇草粉的组合,后期以15%南瓜籽壳粉+10%柠条粉+5%芦苇草粉的组合饲喂滩湖杂代羔羊可提高其平均日增重,增加养殖效益。

柠条收割机圆盘锯式刀片设计与试验

柠条圆盘锯式刀片是收割机的主要零部件之一。在收割运动过程中刀片受力不均匀,且往复循环切割动作导致其易损耗。调研柠条刀片的使用性能及材料特点,研究以特种钢作为刀片基体,在刀刃部表面利用等离子弧熔覆技术进行高合金粉末涂覆,通过优化齿形和热处理工艺参数,获得较优异的耐磨性和强度。经过摩擦磨损试验和作业主体实地收割试验可知,该柠条刀片平茬效果好,使用寿命比同类产品提高了1~2倍。

氮添加对锡林郭勒灌丛草原羊草(Leymus chinensis)化学计量特征的影响

本研究以内蒙古锡林郭勒小叶锦鸡儿(Caragana microphylla)灌丛草原优势物种羊草(Leymus chinensis)为研究对象,研究氮添加对羊草碳、氮、磷元素含量及其化学计量特征的影响。结果表明氮添加对羊草茎叶N,P含量和叶片C∶N,C∶P影响显著;不同氮添加水平对灌丛下和灌丛间羊草C,N,P含量及其化学计量特征的影响存在分异;随氮添加的增加,灌丛间羊草茎叶C∶N和叶片C∶P呈降低趋势,灌丛下羊草茎叶化学计量特征变化不显著;灌丛下羊草茎叶C,N,P含量及其化学计量特征的变异系数均低于灌丛间羊草;氮添加显著影响灌丛间羊草茎叶N含量,C∶N和C∶P,但是,氮添加对灌丛下羊草茎叶化学计量特征影响不显著。小叶锦鸡儿灌丛化过程可能会削弱氮添加对草本植物叶片C,N,P含量及化学计量特征的影响,本研究结果为草原生态系统管理提供了新的视角和重要的理论依据。

Grazing and heat stress protection of native grass by a sand-fixing shrub in the arid lands of northern China

Shrub species are used in restoration projects on dryland for their facilitation effects,which include environmental improvements and protection from herbivore feeding.Facilitation effects on forage grasses are potentially important in improving grazing capacity on rangelands.However,the morphology-dependent performance of benefactor plants in facilitating forage species growth and supplementation under moderate grazing intensity remains unclear.Here,our main purpose was to measure facilitation performance in terms of the survival of a native forage grass,Agropyron cristatum(L.)Gaertn.(Gramineae).,in accordance with the growth conditions of a sand-fixing benefactor shrub,Caragana microphylla Lam.,in the Hulun Buir Grassland,northern China.Six study sites with patches of A.cristatum and C.microphylla were established at the foot of fixed sand dunes.At each site,five quadrats were set in places where C.microphylla coverage was 100%and A.cristatum grew among the shrubs(shrub quadrats),and another five were set where A.cristatum grew alone without C.microphylla(grass quadrats).We measured the morphological traits of C.microphylla and A.cristatum in all 60 quadrats,along with the soil water content and soil temperature.The data were compared between the shrub and grass quadrats by generalized linear mixed-effect models to assess the shrub's facilitation effects.We also used such models to elucidate the relationship between the average height of C.microphylla and the morphological traits of A.cristatum in the shrub quadrats.The maximum height,average grazed height,and the number of seed heads of A.cristatum were greater in the shrub quadrats than in the grass quadrats.The soil surface temperature was lower in the shrub quadrats.The maximum height and seed head number of A.cristatum were positively associated with the average height of C.microphylla.These results suggest that the grazing impact and heat stress were smaller in shrub quadrats than in grass quadrats,and that the degree of this protective effect depended on the shrub height.The shrub canopy seemed to reduce the increase in soil temperature and keep the grass vigorous.Livestock likely avoided grazing grasses in the C.microphylla patches because of the shrub's spiny leaves;only the upper parts of the grass stems(including the seed heads)protruding from the shrub canopy were grazed.The sand-fixing shrub thus moderates the grazing impact and soil temperature,and contributes to vegetation restoration and grazing system sustainability.