准噶尔盆地南缘梭梭群落春季融雪期的土壤呼吸动态

积雪对温带中高纬度地区早春土壤温度和水分具有调控作用,并对土壤呼吸具有重要影响。利用箱式法观测2012年早春积雪融化阶段古尔班通古特沙漠南缘典型温带荒漠梭梭群落内土壤呼吸的动态变化。结果表明：春季融雪期梭梭群落土壤呼吸变异极大,变化范围为0.2~1.2 μmol•m-²•s^-1,日平均土壤呼吸速率变化呈先增后减趋势,但土壤最大呼吸速率随土壤含水量的减少而减少。融雪期灌丛内外土壤呼吸变化规律相同,梭梭灌丛内土壤呼吸速率显著高于灌丛外。融雪期土壤含水量与最大土壤呼吸具有显著的相关关系,但在日尺度上土壤温度与土壤呼吸具有显著的相关关系。研究表明：积雪融化对土壤呼吸具有显著的激发效应,早春积雪变化对土壤呼吸速率将产生重要影响。     

不同植被覆盖度沙垄土壤化学性质的空间分异

为了研究温带固定半固定沙漠土壤化学性质与地表植被的关系,本文以古尔班通古特沙漠西南缘莫索湾地区沙漠–绿洲过渡带为研究区,分别选取植被覆盖度为10%和15%的半固定沙垄及植被盖度为30%的固定沙垄。采集了各沙垄不同地貌部位的土壤样品,室内测试了土壤pH、电导率、有机质、全氮和全磷等指标。结果表明：① 随着植被覆盖度下降,沙垄西坡、坡顶和东坡,土壤pH、电导率、有机质、全氮和全磷呈逐渐降低趋势;② 不同地貌部位的分布格局各沙垄表现不一致,沙垄A和沙垄B的 pH、电导率、有机质、全氮和全磷含量最大值均出现在垄间地,其他部位之间没有明显的规律,沙垄C 的pH和电导率最大值出现在垄间地,而土壤养分含量于坡顶部位富集;③ 各沙垄不同土层土壤性质分布规律相对一致,土壤pH、电导率随着土层深度的增加呈上升的趋势,而土壤养分随着土层深度的增加而降低;④ 土壤化学性质空间分布异质性与植被的分布格局密切相关,相互影响,当植被覆盖度较高时,生物作用起主导作用,当植被覆盖度较低时,风蚀、地形等非生物因素作用加强,影响生物作用,植被对土壤颗粒和养分的拦截及富集作用逐渐减弱或消失。     

不同植被覆盖度沙垄土壤化学性质的空间分异

为了研究温带固定半固定沙漠土壤化学性质与地表植被的关系,本文以古尔班通古特沙漠西南缘莫索湾地区沙漠-绿洲过渡带为研究区,分别选取植被覆盖度为10%和15%的半固定沙垄及植被覆盖度为30%的固定沙垄。采集了各沙垄不同地貌部位的土壤样品,室内测试了土壤pH、电导率、有机质、全氮和全磷等指标。结果表明:①随着植被覆盖度下降,沙垄西坡、坡顶和东坡,土壤pH、电导率、有机质、全氮和全磷呈逐渐降低趋势;②不同地貌部位的分布格局各沙垄表现不一致,沙垄A和沙垄B的pH、电导率、有机质、全氮和全磷含量最大值均出现在垄间地,其他部位之间没有明显的规律,沙垄C的pH和电导率最大值出现在垄间地,而土壤养分含量在坡顶部位富集;③各沙垄不同土层土壤性质分布规律相对一致,土壤pH、电导率随着土层深度的增加呈上升的趋势,而土壤养分随着土层深度的增加而降低;④土壤化学性质空间分布异质性与植被的分布格局密切相关,相互影响,当植被覆盖度较高时,生物作用起主导作用,当植被覆盖度较低时,风蚀、地形等非生物因素作用加强,影响生物作用,植被对土壤颗粒和养分的拦截及富集作用逐渐减弱或消失。     

天山北坡融雪期季节性冻土融化过程分析

利用军塘湖河流域典型试验场2013年11月至2014年3月整个冻结融化期野外观测的季节性冻土温度和水分数据,对融雪期该地区季节性冻土的融化过程和特点进行了分析,研究了融雪期土壤在融化过程中各土壤层的时间与垂直温度和水分的变化,并探讨了融雪期季节性冻土的水文效应。结果表明:1季节性冻土的融化过程可以分为融雪前期、融雪中期和融雪后期3个阶段;2融雪期季节性冻土的温度呈阶段性变化,随着土壤深度的增加,大气温度对土壤温度的影响越小,且存在明显的滞后性;3土壤的水分含量在融雪中期才有所提升,季节性冻土从上下2个方向融解;4融雪中后期的积雪液态含水率对土壤水热状况的影响显著,整个融雪期积雪密度对土壤水热状况影响较小;5季节性冻土的冻融过程对春季融雪径流有着十分重要的影响。     

土壤吸附作用对土壤水分有效性的影响

围绕土壤结皮生物是否可以对夜间土壤吸附水输入产生响应展开研究。假定-1.5 MPa作为土壤水分有效性的临界值,通过观测降水后清晨和午后0~3 cm土壤含水量,分析土壤水分的有效性和空间异质性;并利用连续记录气象数据,建立表层土壤含水量与水汽压饱和差数量关系。结果表明:土壤吸附作用提高了土壤水分对土壤结皮生物的有效性,并延长了土壤结皮生物对降水脉冲的响应时段。在古尔班通古特沙漠东南部的不同部位,凝结吸附作用对沙面水分条件影响很大(特别是干旱季节),水分条件由好到坏依次为:沙垄西坡面、沙垄垄顶、沙垄东坡面和垄间低地。     

沙尘对天山积雪消融的影响

积雪是西北干旱区重要的水资源,春季融雪时期,沙尘天气频繁,沙尘沉降会减少积雪表面反射率,增加雪层的太阳辐射吸收,加速积雪的融化,影响干旱区年内的水资源分布。通过融雪期在天山积雪雪崩研究站开展模拟沙尘沉降试验,观测积雪物理特性参数变化,分析沙尘对积雪消融的影响。本研究设置2 g·m^-2、4 g·m^-2、8 g·m^-2、自然雪4个处理,3组重复,从3月4日开始,3月11日结束。结果表明：沙尘沉降对积雪消融具有明显影响。在2 g·m^-2、4 g·m^-2、8 g·m^-2沙尘沉降量下,随着融雪的进行,沙尘沉降量逐渐增大,致使积雪表面粒径增大,积雪反射率降低,雪表层温度差变大,2 g·m^-2、4 g·m^-2、8 g·m^-2导致积雪消融速率比自然状态下的快22.36%、46.05%和76.90%。通过野外试验获得了主要积雪物理参数对沙尘沉降的响应,量化了沙尘沉降对积雪消融的影响,其结果可为西北干旱区水资源管理提供参考。     

冷荒漠草本植物数量特征对不同水分输入和气象因子的响应

草本层是古尔班通古特沙漠植被的重要组成部分,在维持沙漠稳定、养分循环等方面具有重要意义。水分通常以积雪和降雨形式输入到土壤,输入方式及数量变化对荒漠植物的存活和生长有重要影响。本文以古尔班通古特沙漠南缘草本层为研究对象,利用人工增减积雪的方法,共设置4个积雪处理(0,50%,100%,200%积雪,其中100%积雪为对照),于2009—2016年春季调查草本植物的数量特征和物种丰富度,分析草本植物数量特征对水分变化的响应;同时结合气象数据,分析不同年份一年生荒漠草本植物数量特征与主要气象因子的关系。结果表明：表层土壤含水量与积雪厚度成正比,相应的草本植物的幼苗密度与积雪水当量、表层土壤含水量成正比关系;2009—2016年,年内积雪量的变化对物种丰富度没有显著影响,各积雪处理间物种丰富度差异不显著;2009—2016年自然处理下年际间物种丰富度差异显著,2015年物种丰富度显著小于其余年份。结合气象数据分析发现,物种丰富度年际变化主要受幼苗建成期的降雨调控,并且干旱年份过后的湿润年份物种丰富度不受前一年降水的影响,说明荒漠草本植物层片具有较强的自我调节能力;自然处理下,不同年份草本植物旺盛期的存活数量与大气干旱程度(空气饱和差)呈显著负相关关系（R²值为0.611,P<0.05）,与生长季的降雨量呈正相关关系（R²值为0.162, P>0.05）,说明大气干旱程度更能表征荒漠草本植物生长峰值期的存活情况。     

库姆塔格沙漠综合考察的主要进展

通过对库姆塔格沙漠的实地观测、样品分析和资料收集,获得了沙漠地区的基础数据。沙漠面积约2.29×104km2(2001年),沙漠存在向东南方向移动和周边扩大的趋势;库姆塔格沙漠沙丘形态以新月形沙丘链为主,羽毛状沙丘为特色,星状和其他复合型沙丘大量分布的特点;羽毛状沙丘的"羽轴"是一种较特殊的复合型沙垄,由单个新月形沙丘前后相连,在沙垄和沙垄之间的沙平地有地形起伏,形成较宽大的弧形沙埂,基本与沙垄走向垂直,由这些沙垄和沙埂组成了独特的羽毛状沙丘;沙漠内部羽毛状沙丘分布区全年盛行东北风,全年平均风速5.94m/s,年总输沙势944.46 VU;调查记录了沙漠区107种植物和79种脊椎动物,发现野骆驼在沙漠西部的水源地,3种稀有荒漠植物的新分布区;提出沙漠最早形成于70万年的中更新世。     

天山北坡季节性积雪消融对浅层土壤水热变化影响研究

融雪期,浅层土壤水热变化影响融雪水下渗及积雪产流过程,是融雪产流模拟及汇流计算的重要参数.本研究以天山北坡军塘湖流域为研究区,从积雪消融角度来分析浅层土壤水热变化情况,通过分析积雪消融期土壤剖面水分、温度的变化规律确定二者之间的定量关系.结果表明,气温对土壤温度的影响随着土壤深度增加减弱,积雪越厚,土壤温度越高;土壤水分受地温影响较大,雪水入渗能在一定程度上补给土壤水,但消融后期剧烈的蒸发引起土壤表层10cm内水分损失较多.阴阳坡土壤水分均随时间呈中等变异(除阳坡60cm),在30-60cm土壤层土壤水热间表现出显著的相关性.此结果为该区域农业生产、春季融雪洪水预警进一步研究提供参考.     

天山北坡融雪期雪层含水率、密度和雪层温度研究

利用DELTA T自动气象仪和Snow Folk积雪特性仪等观测分析整个融雪期阴阳坡雪层含水率、密度与雪层温度的时间变化特征和垂直变化特征并分析与气温、雪深、风速、空气湿度、露点温度（[WTBX]DP）、湿球温度（WB[WTBZ]）等的相关性。结果表明：① 融雪期雪层温度的变化,总的来说阳坡雪层温度大于阴坡。前期阳坡雪层平均温度大于阴坡,后期阴坡积雪平均温度大于阳坡。阴阳坡平均温度在上层最高,中层最低。融雪期温度梯度变化,阴坡总的温度梯度值为负,阳坡为正。② 融雪期含水率的变化,阳坡雪层平均含水率大于阴坡,阴阳坡下层含水率最大,上层次之。融雪期含水率梯度的变化,融雪期阴坡的含水率为正梯度,阳坡的含水率为负的含水率梯度。③ 融雪期密度初期密度梯度较大,后期密度梯度减小。阳坡平均密度大于阴坡,阳坡较阴坡会出现较大的密度值。阴坡密度每日拐点比阳坡早2 h。     

Combined effects of snow depth and nitrogen addition on ephemeral growth at the southern edge of the Gurbantunggut Desert, China

Water and nitrogen(N) inputs are considered as the two main limiting factors affecting plant growth.Changes in these inputs are expected to alter the structure and composition of the plant community,thereby influencing biodiversity and ecosystem function.Snowfall is a form of precipitation in winter,and snow melting can recharge soil water and result in a flourish of ephemerals during springtime in the Gurbantunggut Desert,ChinaA bi-factor experiment was designed and deployed during the snow-covering season from 2009 to 2010.The experiment aimed to explore the effects of different snow-covering depths and N addition levels on ephemerals.Findings indicated that deeper snow cover led to the increases in water content in topsoil as well as density and coverage of ephemeral plants in the same N treatment;by contrast,N addition sharply decreased the density of ephemerals in the same snow treatment.Meanwhile,N addition exhibited a different effect on the growth of ephemeral plants:in the 50% snow treatment,N addition limited the growth of ephemeral plants,showing that the height and the aboveground biomass of the ephemeral plants were lower than in those without N addition;while with the increases in snow depth(100% and 150% snow treatments),N addition benefited the growth of the dominant individual plants.Species richness was not significantly affected by snow in the same N treatment.However,N addition significantly decreased the species richness in the same snow-covering depth.The primary productivity of ephemerals in the N addition increased with the increase of snow depth.These variations indicated that the effect of N on the growth of ephemerals was restricted by water supply.With plenty of water(100% and 150% snow treatments),N addition contributed to the growth of ephemeral plants;while with less water(50% snow treatment),N addition restricted the growth of ephemeral plants.     

塔里木沙漠公路生态防护林沿线土壤表层盐分特征

根据56个土壤表层样品、49个水样的分析,探讨了塔里木沙漠公路生态防护林带沿线土壤表层盐分的基本特征,并研究了防护林沿线土壤盐分的分布规律。结果表明:表层土壤具有盐分含量高、表聚性强烈的特征;地下水矿化度与地下水电导率、土壤电导率与土壤盐分含量均呈现极显著相关性,土壤盐分属于碱性钠型氯化物。     

Snowpack shifts cyanobacterial community in biological soil crusts

Winter snowpack is an important source of moisture that influences the development ofbiological soil crusts(BSCs)in desert ecosystems.Cyanobacteria are important photosynthetic organismsin BSCs.However,the responses of the cyanobacterial community in BSCs to snowpack,snow depth andmelting snow are still unknown.In this study,we investigated the cyanobacterial community compositionand diversity in BSCs under different snow treatments(doubled snow,ambient snow and removed snow)and three snow stages(stage 1,snowpack;stage 2,melting snow;and stage 3,melted snow)in theGurbantunggut Desert in China.In stages 1 and 2,Cyanobacteria were the dominant phylum in the bacterialcommunity in the removed snow treatment,whereas Proteobacteria and Bacteroidetes were abundant inthe bacterial communities in the ambient snow and doubled snow treatments.The relative abundances ofProteobacteria and Bacteroidetes increased with increasing snow depth.The relative abundances ofCyanobacteria and other bacterial taxa were affected mainly by soil temperature and irradiance.In stages 2and 3,the relative abundance of Cyanobacteria increased quickly due to the suitable soil moisture andirradiance conditions.Oscillatoriales,Chroococcales,Nostocales,Synechococcales and unclassifiedCyanobacteria were detected in all the snow treatments,and the most dominant taxa were Oscillatorialesand Chroococcales.Various cyanobacterial taxa showed different responses to snowpack.Soil moisture andirradiance were the two critical factors shaping the cyanobacterial community structure.The snowpackdepth and duration altered the soil surface irradiance,soil moisture and other soil properties,whichconsequently were selected for different cyanobacterial communities.Thus,local microenvironmentalfiltering(niche selection)caused by snow conditions may be a dominant process driving shifts in thecyanobacterial community in BSCs.     

Stable isotope analysis of water sources for Tamarix laxa in the mega-dunes of the Badain Jaran Desert,China

The complex interactions in desert ecosystems between functional types and environmental conditions could be reflected by plant water use patterns. However, the mechanisms underlying the water use patterns as well as the water sources of Tamarix laxa in the mega-dunes of the Badain Jaran Desert, China, remain unclear. This study investigated the water sources and water use patterns of T. laxa using the stable oxygen isotope method. The δ¹⁸O values of xylem water, soil water in different layers (0-200 cm), rainwater, snow water, lake water, atmospheric water vapor, condensate water, and groundwater were measured. The sources of water used by T. laxa were determined using the IsoSource model. The results indicate that T. laxa mainly relies on soil water. At the beginning of the growing season (in May), the species is primarily dependent on water from the middle soil layer (60-120 cm) and deep soil layer (120-200 cm). However, it mainly absorbs water from the shallow soil layer (0-60 cm) as the rainy season commences. In September, water use of T. laxa reverts to the deep soil layer (120-200 cm). The water use patterns of T. laxa are closely linked with heavy precipitation events and soil water content. These findings reveal the drought resistance mechanisms of T. laxa and are of significance for screening species for ecological restoration.     

不同技术措施对梭梭免灌造林成活率的影响

分别于2009年、2010年春季,在新疆古尔班通古特沙漠南缘选取了迎风坡、丘间平地、背风坡作为研究样地,采用不同的技术措施(保水剂、生根粉和液体地膜)进行梭梭免灌造林试验,以确定这些技术措施是否能有效提高古尔班通古特沙漠地区免灌造林成活率。结果表明:实施这些措施后,不同立地条件之间梭梭免灌造林成活率存在显著差异;水分是限制古尔班通古特沙漠梭梭免灌造林成活的关键因子,土壤理化性质对梭梭免灌造林成活率影响不显著;三种造林措施对梭梭免灌造林成活率有一定作用,但效果不显著。     

塔克拉玛干沙漠腹地人工绿地水盐动态的研究

自１９９４年塔中开始绿地建设以来,绿地长期使用高矿化度的地下水灌溉,局部地区出现积盐,盐分积累问题成为人们关注的焦点,本语文立足于几年来对绿地土壤水盐连续观测的资料,对水盐动态规律进行总结,提出在沙漠腹地长期高矿化度水灌溉,并不会靠民土壤大面积积盐结论。     

乌兰布和沙漠绿洲不同生态功能区划分及其建设策略

绿洲是乌兰布和沙漠最重要的生态经济区域,绿洲寓于沙漠而异于沙漠。本文采用样线与样方相结合的方法,综合调查了绿洲-荒漠综合体的景观、地貌、植被、水土资源特征、经济活动及生态环境问题等因子,依据各因子特征的差异,将乌兰布和沙漠绿洲-荒漠综合体划分为绿洲生态经济核心区、绿洲—荒漠生态缓冲区和自然荒漠生态恢复区三个生态功能区;并论述了各功能区的特征、存在的生态环境问题,提出了不同生态功能区今后的建设方向和策略。     

Stable oxygen-hydrogen isotopes reveal water use strategies of Tamarix taklamakanensis in the Taklimakan Desert,China

Tamarix taklamakanensis,a dominant species in the Taklimakan Desert of China,plays a crucial role in stabilizing sand dunes and maintaining regional ecosystem stability.This study aimed to determine the water use strategies of T.taklamakanensis in the Taklimakan Desert under a falling groundwater depth.Four typical T.taklamakanensis nabkha habitats(sandy desert of Tazhong site,saline desert-alluvial plain of Qiemo site,desert-oasis ecotone of Qira site and desert-oasis ecotone of Aral site)were selected with different climate,soil,groundwater and plant cover conditions.Stable isotope values of hydrogen and oxygen were measured for plant xylem water,soil water(soil depths within 0–500 cm),snowmelt water and groundwater in the different habitats.Four potential water sources for T.taklamakanensis,defined as shallow,middle and deep soil water,as well as groundwater,were investigated using a Bayesian isotope mixing model.It was found that groundwater in the Taklimakan Desert was not completely recharged by precipitation,but through the river runoff from snowmelt water in the nearby mountain ranges.The surface soil water content was quickly depleted by strong evaporation,groundwater depth was relatively shallow and the height of T.taklamakanensis nabkha was relatively low,thus T.taklamakanensis primarily utilized the middle(23%±1%)and deep(31%±5%)soil water and groundwater(36%±2%)within the sandy desert habitat.T.taklamakanensis mainly used the deep soil water(55%±4%)and a small amount of groundwater(25%±2%)within the saline desert-alluvial plain habitat,where the soil water content was relatively high and the groundwater depth was shallow.In contrast,within the desert-oasis ecotone in the Qira and Aral sites,T.taklamakanensis primarily utilized the deep soil water(35%±1%and 38%±2%,respectively)and may also use groundwater because the height of T.taklamakanensis nabkha was relatively high in these habitats and the soil water content was relatively low,which is associated with the reduced groundwater depth due to excessive water resource exploitation and utilization by surrounding cities.Consequently,T.taklamakanensis showed distinct water use strategies among the different habitats and primarily depended on the relatively stable water sources(deep soil water and groundwater),reflecting its adaptations to the different habitats in the arid desert environment.These findings improve our understanding on determining the water sources and water use strategies of T.taklamakanensis in the Taklimakan Desert.