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。     

生物结皮发育对地表蒸发过程影响机理研究

生物结皮的形成与发育显著改变了土壤地表特征及下伏土壤性质,对地表蒸发过程产生深远影响.但目前已有研究对生物结皮存地表蒸发过程中的作用仍存在很大争议.文中通过覆盖结皮和模拟降水的方法对土壤蒸发过程进行研究,以期初步揭示生物结皮发育影响地表蒸发过程的机理.结果表明:生物结皮主要通过结皮层对降水的截留和阻碍扩散作用及对下伏土...     

黄土高原生物结皮形成过程中土壤胞外酶活性及其化学计量变化特征

生物土壤结皮在增强土壤抵抗水蚀风蚀能力、改善土壤养分等方面发挥着重要作用,土壤胞外酶活性可作为土壤生化反应强度的微生物指标,对理解荒漠生态系统微生物参与的养分循环过程具有重要意义.选取黄土高原神木县六道沟小流域5个生物结皮发育阶段(裸沙地、全藻结皮、藻-藓混生结皮、藓-藻混生结皮、全藓结皮)的土壤作为研究对象,研究生物...     

古尔班通古特沙漠不同类型生物结皮对草本植物多样性影响

选择古尔班通古特沙漠的北部(一号点)、中部(二号点)、南部(三号点)3个不同样点的裸沙和藻结皮、地衣结皮与苔藓结皮3种生物结皮类型,对比研究了草本植物多样性的差异性及其主要环境影响因素.结果表明:(1)不同生物结皮类型的土壤理化性质有明显差异,土壤有机质、全氮、全磷、全钾含量以及黏粒、粉粒和细沙的含量随生物结皮演替显著...     

古尔班通古特沙漠生物结皮影响下土壤水分的日变化

对新疆古尔班通古特沙漠生物结皮影响下土壤水分的日变化特征进行了定量研究,结果表明:①无论是结皮覆盖区还是无结皮覆盖区,其土壤含水量随深度的变化均表现出明显的层次性,其中以距地表 20 cm处的土壤含水量最高.②结皮覆盖区距地表5 cm和10 cm处的土壤含水量显著高于无结皮覆盖区(LSD检验, p ＜0.05);而45 cm和60 cm处的土壤含水量则表现为结皮覆盖区极显著低于无结皮区(LSD检验,p＜0.05),说明生物结皮具有较强的保持土壤表层水分的能力.③结皮覆盖区与无结皮覆盖区土壤水分的日变化特征明显不同于距地表5 cm处,而其他各土层的变化趋势则较为一致.无结皮覆盖区距地表5 cm处土壤水分的日变化呈先上升后下降的趋势,而结皮覆盖区的变化则恰恰相反.     

黄土丘陵沟壑区生物土壤结皮理化性质

为了解黄土丘陵沟壑区生物结皮发育过程中理化性质的变化,分析了不同盖度水平结皮的机械组成、养分、化学元素以及土壤因子与生物结皮盖度的相关性和结皮发育过程中土壤因子之间的相互作用。结果表明:随着结皮的发育,土壤有机质、全氮、全钾、速效氮、速效磷、速效钾含量均呈增长趋势,pH值则相反;土壤细砂粒含量(0.25~0.05 mm)减少,粗粉粒(0.05~0.01 mm)含量增加;土壤中的化学元素含量也呈增加趋势。土壤有机质、全氮、全磷、pH值、细砂粒、粗粉粒、Ca,Mg,Na和Fe含量与生物结皮的形成发育密切相关(P0.01)。此外,各土壤因子之间存在着相关关系,特别是粗粉粒含量和pH值,与其他因子有显著的相关性。     

黄土高原藓结皮覆盖土壤导水性能和水流特征

生物结皮具有特殊的水文物理性质,为探究其对土壤水分渗透性和水流特征的影响,以黄土高原风沙土和黄绵土上3种典型地表覆盖类型(裸地、藓结皮、藓结皮-草本植物混合)为对象,采用环刀法和染色示踪法对其导水性质与水流特征进行探究。结果表明:藓结皮对2种土壤类型0~5 cm土层土壤理化性质影响较大,与裸地相比土壤容重降低了9.85%~10.00%,土壤黏粒含量增加了1.01~1.29倍,表层有机质含量提高了2.73~3.02倍;藓结皮使0~5 cm土层土壤饱和导水率降低了61.32%~88.89%,而在5~10 cm土层饱和导水率则有明显上升。另外,由于草本植物的影响,藓结皮-草本植物0~5 cm土层与藓结皮土壤相比土壤饱和导水率提高了1.32~6.43倍;黄绵土藓结皮与藓结皮-草本植物的染色面积比均高于裸地,且水分下渗深度增加了10 cm,而风沙土藓结皮与风沙土裸地的染色面积比差异不明显。综上所述,藓结皮和藓结皮-草本植物的存在改变了表层土壤水分渗透性以及水流运动特征和水分下渗深度,影响着黄土高原土壤水分保持和生态恢复。     

结皮土壤的抗风蚀性分析

土壤结皮是土壤在自然状态下形成的“保护层”,它的存在使得土壤变得稳定,使土壤的抗风蚀性有显著的提高,可以有效地抵抗冬春季节严重的风蚀,因此在干旱荒漠化地区越来越受到重视。土壤结皮分为物理结皮和生物结皮两类,由于生物结皮的生成需要长时间的积累,而且要求具有一定的湿度、温度,才可能存活和生长。而物理结皮只要土壤经过干-湿的过程很容易形成。本文通过实地观察,从不同的土质取得的原状土壤结皮样本进行扫描电镜观察,对土壤物理结皮的形成,与土壤的含水量、颗粒组成、含盐量等的关系,以及对土壤抗风蚀性的作用进行了详细的论述,以便使其在干旱、寒冷地区土壤荒漠化防治中受到足够的重视,减少人为因素对土壤结皮的破坏,利用人为手段促使结皮的形成,减少冬春季节风沙对土壤的侵蚀。     

荒漠结皮对土壤水分状况的影响

本研究针对鄂尔多斯沙地生物结皮进行调查 ,利用人工喷水模拟降雨分析结皮对土壤入渗性能的影响。研究表明 :生物结皮能显著地降低土壤水分的入渗速率。在去掉结皮时 ,表层下 5 cm处的土壤含水量在 1 0分钟时即开始显著增加 ,而有结皮时 ,此处的含水量则在 1 5分钟时才开始显著增加。利用圆盘入渗仪测定有结皮和无结皮条件下的土壤饱和导水率表明 :固定沙丘间地有生物结皮的土壤饱和导水率范围是 :2 9.1 0 - 82 .2 1 mm/ h;半固定沙丘有微弱结皮时饱和导水率为 1 43.5 4 - 2 30 .2 5 ;去掉结皮后土壤的饱和导水率可显著上升数倍 ,无结皮的流沙的饱和导水率最高。     

北方农牧交错带沙地生物结皮研究

为了解我国北方农牧交错带生物结皮的生态意义,本文以宁夏盐池为例,采用样线调查法进行结皮及植被调查,并在有结皮和无结皮覆盖两种情况下进行入渗试验。研究表明:北方半干旱区生物结皮对植物生长存在先促进、后抑制的过程。在风蚀环境条件和不稳定的土壤条件下,生物结皮的出现可创造适合植物生长的微环境,为植物的生长提供了条件。方差分析显示有结皮时的植被盖度明显高于无结皮覆盖的植被盖度。当环境条件改善时,结皮开始抑制植物的生长,两者存在一种显著的线性负相关关系。研究区从封育边缘到核心,结皮盖度为核心>边缘,植被盖度正好相反,两者的相关系数高达-0.920;生物结皮对入渗具有明显的阻碍作用,结皮盖度与入渗深度之间呈线性负相关,相关系数为-0.765,说明结皮的存在使土壤水分呈现浅层化趋势。     

Microbiotic Crust Influence on Unsaturated Hydraulic Conductivity

Microbiotic crusts occur extensively in rangeland soils . Developed by filaments of cyanobacteria and algae , and thalli of lichen and moss entanglement of soil particles , they create a physical discontinuity in the surface profile with greater concen trations of clay , silt , and potentially hydrophobic organic matter. These conditions potentially contribute to variability in soil hydrology of arid land and should be considered in the development of hydrologic and erosion models. However, there is limited manipulative research examining the functional relationships between soil and microbiotic crusts . We investigated the influence of cyanobacterial-dominated microbiotic crust on measured hydraulic conductivity (K) in a sandy loam soil at a southeastern Utah site . Using a tension infiltrometer , we determined K under three surface treatments: undisturbed , chemically killed (representing dead microphytes within the crust), and removed (scalped) microbiotic crusts. We applied treatments to spatially interspersed intact surface soils within shrub interspaces . Microbiotic crusts at this site and in this stage of successional development had no discernible influence on K. This finding supports results from research conducted in a variety of soils from sandy to silt dominated with a range of microbiotic development . Because this research was site and time specific , and because the role of microbiotic crusts in the environment continues to be debated , additional research is warranted to deter mine how stage of development of microbiotic crust influences soil hydrology .     

Effects of biological soil crusts and drought on emergence and survival of a Patagonian perennial grass in the Monte of Argentina

Biological soil crusts are widely distributed in arid and semiarid regions. They have an important eco- logical role, especially by modifying physical and chemical properties of soils. Biological crusts may also modify seed germination and seedling establishment. The effects vary widely according to the type of crust and the vas- cular plant species. The objective of this study was to determine the effect of moss-dominated biological soil crusts on the emergence, biomass and survival of Poa ligularis Nees ex Steud. under different irrigation regimes. We col- lected seeds of P. ligularis and biological soil crusts composed of two species of mosses： Syntrichia princeps （De Not.） Mitt and Ceratodon purpureus （Hedw.） Brid. from an area in the Monte of Argentina. The result showed that seedling emergence of P. ligularis was higher in treatments with bare soil than in soil covered by crusts, and also in those with watering to field capacity. Mean emergence time was higher in treatments with bare soil and watering to field capacity. Seedling biomass also showed significant differences between treatments. These results suggest that biological soil crusts dominated by mosses do not promote P. ligularis emergence, although they would not affect its survival.     

黄土高原土壤生物结皮对植物种子出苗和生长的影响

为了解生物土壤结皮对植物种子萌发出苗和植物生长的影响,于2009年7～8月在陕西省吴起县进行野外调查,对油松（Pinus tabulaeformis）、柠条（Caragana korshinskii）、沙棘（Hippophae rhamnoides）和杜梨（Pyrus betulae-folia）种子进行萌发实验,研究...     

生物土壤结皮结构、功能及人工恢复技术

生物土壤结皮作为典型的有机地被层,广泛分布在干旱半干旱地区.由于其具有良好的水土保持及土壤稳定等功能,可有效控制土地沙漠化,防治水土流失,因此,生物土壤结皮恢复被看作是荒漠生态系统修复和重建的关键.本文系统综述了国内外学者在生物结皮领域开展的研究工作,包括生物土壤结皮的生物组成、演替过程、生态功能、干扰响应、人工培育及...     

中国西北干旱区城市水、大气污染排放与FDI关系研究

"一带一路"倡议在中国西北干旱半干旱区的实施,是否会带来水、大气的污染转移效应引起广泛关注。匮乏的水资源、脆弱的生态环境决定了其不宜引入污染密集型的外商直接投资(FDI)。有别于以往文献从国家、省级层面或分东、中、西地区对FDI的污染转移效应进行研究,本文使用更能体现干旱半干旱区生态、经济差异的城市级数据,运用灰色关联、双重差分方法,研究"一带一路"倡议下,FDI是否对中国西北干旱半干旱区城市水、大气产生污染转移效应。结果显示,"一带一路"倡议实施以来,西北干旱区城市水、大气污染排放与FDI的关联程度下降;且半干旱区远大于干旱区的FDI增幅,并没有导致城市间显著的水、大气污染排放的差异。     

中国干旱半干旱地区土壤凝结水研究综述

中国北方干旱半干旱地区的气象条件有利于土壤凝结水的形成。从20世纪60年代以来,相继开展了一系列土壤凝结水的实验与研究。土壤凝结水特指地面温度和表层地温达到露点时,大气水汽和土壤孔隙水汽由汽态水凝结而成的液态水。近地气温、地温、相对湿度、下垫面性质、地下水埋深等因素都会影响凝结水形成的速度、深度和数量。土壤凝结水的水汽来源主要是近地表大气和包气带孔隙中的水汽。土壤凝结水是土壤水和地下水水分平衡不可忽缺的因素。土壤凝结水也是干旱半干旱地区的主要水源之一,具有重要的生态与环境意义。     

Anatomical and morphological characteristics of Populus euphratica in the lower reaches of Tarim River under extreme drought environment

Populus euphratica Oliv.is an old desert tree species that has been naturalized and invades zones along the watercourses in many arid and semiarid regions.The plant species developed some plasticity to adapt to the gradual environmental gradients.The aim of this study was to test the hypothesis that the changes in leaf morphology of P.euphratica reflect the adaptability of the plant to the unique environment of the lower reaches of Tarim River in China.The foliar architecture,blade epidermal and internal anatomies of P.euphratica were analyzed at different sites along the Tarim River.Compared with the abaxial surface of the leaves,their adaxial surface has more hairs,a greater stomatal density and opening,higher mesophyll proportion,and increased blade thickness,palisade width,and epidermal thickness.The long trichome of the roots found at site 6 in the Yinsu section may be an adapted structure of the plants in arid areas.The mature leaves of P.euphratica have comparatively more epidermis and cuticles,well developed palisades and more chloroplasts at different sites compared to the young leaves.Foliar morphological and anatomical variability in P.euphratica may be considered an adaptive advantage that enables leaves to develop and function in different habitats,marked by strong variations in solar radiation,air temperature,humidity and water table.     

Saline dust storms and their ecological impacts in arid regions

In many arid and semiarid regions,saline playas represent a significant source of unconsoli-dated sediments available for aeolian transport,and severe saline dust storms occur frequently due to human disturbance.In this study,saline dust storms are reviewed systematically from the aspects of con-cept,general characteristics,conditions of occurrence,distribution and ecological impact.Our researches showed that saline dust storms are a kind of chemical dust storm originating in dry lake beds in arid and semiarid regions;large areas of unconsolidated saline playa sediments and frequent strong winds are the basic factors to saline dust storm occurrence;there are differentiation characteristics in deposition flux and chemical composition with wind-blown distance during saline dust storm diffusion;and saline dust storm diffusion to some extent increases glacier melt and results in soil salinization in arid regions.An under-standing of saline dust storms is important to guide disaster prevention and ecological rehabilitation.     

荒漠化防治的另一途径——C4植物

荒漠化和沙尘暴不仅影响西北地区,同时也影响到相邻地区的国民经济的发展和人民生活的改善.虽然,我国政府历年来都十分重视西北地区的生态条件的改善和环境的建设,但我国沙尘暴的频次和强度在未来几年仍有增加之势.C4(碳四)植物具有高光饱和点、高光合速率和高光合生产效率的生理特性.比C3(碳三)植物耗水少,而光合效率高.对土壤的适应性广,具有较强的竞争力.它应是优先考虑的干旱区水土保持植物.从美国选育的C4纤维禾草可以看出,多年生的C4纤维禾草具有:①光合效率高,而水耗低;②多年生可节省每年播种所需的种、肥和耕作费用,节省生产成本;③强大的根系可使植物体内的氮元素储存起来,提高了土壤养分的利用率等特点.它是干旱区中一种既节水,又是水土保持最有成效的植物资源,对缓解西北地区的荒漠化问题将会发挥巨大的作用.我国温带地区的草本植物资源丰富,其中有不少的C4植物.建议开展C4草本植物和木本植物的选育、引种和推广研究,以在半荒漠地区营造一个环境良好、人与自然和谐的家园.