放牧扰动下高寒草甸植物多样性、生产力对土壤养分条件变化的响应

为了揭示高寒小嵩草草甸群落在放牧扰动下,探讨土壤养分供给水平的变化对生态系统初级生产力和多样性影响,为高寒草地的退化演替机理研究提供依据,以野外样地调查和室内分析法研究了放牧扰动下高寒草甸植物多样性、生产力对土壤养分条件变化的响应.结果表明,放牧干扰不仅改变了高寒小蒿草草甸群落土壤根系和蕴育土壤根系的"载体"量及根土比例,改变了植物群落的结构和功能,而且使土壤的物理和化学特性发生了明显的改变.随着放牧强度的增加,蕴育土壤根系的基质量逐渐减少,根土比特别是0～10 cm土层的根土比例增加;"载体"量减少导致大部分地下根系由于营养供给水平的降低而死亡,归还土壤中有机质的数量逐渐减少,加之地上部分持续利用,土壤养分也在不断消耗,土壤基质量的减少和土壤资源持续供给能力的下降,草地发生逆向演替(退化),表现在:物种数减少、多样性下降、能量的分配转向地下等;土壤性状上的某些改变(土壤容重、土壤湿度等),也会引起植被组成、物种多样性变化;放牧主要通过影响土壤环境及其养分含量来改变草地群落生物量(地上、地下);土壤表面的适度干扰和原有植物的适度破坏为新成员提供了小生境,从而允许新的植物侵入群落,并提高了植物的丰富度.但是,在受到强度干扰时,草地植物群落的主要物种的优势地位发生明显的替代变化.     

土壤-牧草氮素供需状况变化对高寒草甸植被演替与草地退化的影响

在中国科学院海北高寒草甸生态系统定位站 ,选取处于不同退化阶段的具有典型代表意义的草甸草场为研究对象 ,通过对其土壤氮素矿化补给能力、牧草对氮素的需求量的研究 ,探讨土壤 牧草氮素供需状况变化对高寒草甸植被演替与草地退化的影响。结果表明 ,在牧草生长季 5～ 8月 ,高寒草甸土壤的氮素矿化补给量为 15 86 g·m-2 ,而随着高寒草甸退化程度的加重 ,植物群落中优势种群由禾草演替为禾草 苔草 嵩草、嵩草至杂类草 ,其牧草生长需要的总氮量分别为 2 2 86、2 4 87、37 3、14 96g·m-2 ,只有在杂类草草甸阶段 ,其牧草生长对氮素的需求才与其土壤氮素供求相适配 ,可见养分是高寒草甸植被演替与草场退化的重要驱动因子之一。     

高寒矮嵩草群落退化演替系列氮、磷生态化学计量学特征

运用历史资料与实地调查相结合的方法,以多元数量统计为手段确定采样地点,以空间尺度代替时间尺度,确定演替系列,以生态化学计量学为基础探讨了高寒矮嵩草草甸退化演替系列氮(N)磷(P)含量及化学计量学特征,发现:1)高寒矮嵩草草甸土壤全量N、P含量随退化演替程度的加深而呈倒"V"字形变化趋势,速效N、P含量随退化程度的加深呈降低趋势,但土壤草甸全量及速效N/P化学计量学特征则呈现降低趋势;2)地上植物N/P化学计量学特征在整个退化演替过程没有明显的差异。说明高寒矮嵩草群落退化改变了土壤中全量及速效N、P的积累和分解速率,打破了土壤系统养分平衡模式,但并没有明显改变植物地上部分整体的N/P化学计量学特征,因此在退化演替过程中植物N/P比为草地退化诊断的惰性指标;土壤N/P化学计量学特征变化同草地退化演替过程具有较好的同步性,其对草地退化演替的敏感性较高,有可能成为未来草地退化诊断的生态指示指标。     

青藏高原多年冻土区不同水分条件的高寒草甸根系功能性状对增温的响应

在青藏高原多年冻土广泛分布的风火山地区,选择小嵩草（Kobresia pygmea）草甸和藏嵩草（Kobresia tibetica）沼泽化草甸为研究对象,采用开顶增温室（Open top chambers, OTCs）模拟气候变暖,探讨模拟增温对土壤水分差异的两种草甸地下生物量及根系功能性状的影响。结果显示,（1）增温显著增加小嵩草草甸0—20 cm根系生物量,主要是由于表层（0—10 cm）根系生物量显著增加,而对藏嵩草沼泽化草甸根系生物量无影响。（2）增温显著增加了小嵩草草甸根组织密度,同时提高了藏嵩草沼泽化草甸10—20 cm的比根长和比根面积（3）增温降低了小嵩草草甸的根系碳含量及10—20 cm根系氮含量,增加了藏嵩草沼泽化草甸的碳含量及10—20 cm根系氮含量,显著提高了小嵩草草甸和藏嵩草沼泽化草甸深层（10—20 cm）根系碳氮比。这些结果预示着增温使得土壤水分较低的小嵩草草甸朝着资源保守的慢速生长型发展,以适应暖干化的环境;土壤水分较高的藏嵩草沼泽化草甸朝着资源获取的快速生长型发展,加速利用土壤中的养分满足植物生长需要。可见,土壤水分可以调节高寒草甸对气候变暖的演变趋势,强调了水分的重要性。     

青藏高原高寒草甸退化对矮嵩草有关生理特性的影响

该研究采用空间分布代替时间演替的方法,选取青藏高原青海省果洛藏族自治州玛沁县境内典型的未退化草甸和退化草甸样地,分别设置3个5m×5m的样方,于6至9月下旬上午进行植株和土壤采样,测定矮嵩草生理指标,探讨高寒草甸退化所导致的环境变化对自然生长状态下矮嵩草生理特性的影响机制。结果表明:(1)与未退化草甸相比,退化导致土壤表层速效氮含量极显著降低,而速效磷和速效钾含量显著升高;全氮、全磷和全钾的含量总体上表现为未退化草甸低于退化草甸。(2)与未退化草甸相比,退化草甸矮嵩草叶中超氧化物歧化酶(SOD)活性在生长前期高而后期低(低4%),谷胱甘肽(GSH)含量在两个样地的变化趋势基本一致。(3)退化草甸矮嵩草叶片可溶糖和可溶蛋白含量在生长后期分别比未退化草甸降低17.6%和34.9%,且9月份降低达极显著水平。(4)生长中期以后,退化草甸矮嵩草叶片叶绿素a、b含量比未退化草甸的下降速度快、含量分别低18.84%和20.68%。(5)退化草甸矮嵩草叶片超氧阴离子自由基(O_2~)的产生速率在9月份极显著高于未退化草甸。研究表明,在非生物胁迫下未退化草甸的矮嵩草具有更高的ROS清除能力和渗透调节能力,退化导致的环境变化可能是矮嵩草在生长后期抗氧化能力降低、衰老早的内在原因。     

人类活动对青藏高原高寒矮嵩草草甸碳过程的影响

随着人类活动干扰(放牧)的增加,青藏高原高寒嵩草甸的退化演替过程依次为禾草-矮嵩草群落、矮嵩草群落、小嵩草群落和杂类草-黑土滩4个阶。其中小嵩草群落又可划分为草毡表层加厚、开裂与塌陷3个子阶段。采用时空转换的方法,研究了人类活动对青藏高原高寒矮嵩草草甸碳过程的影响。结果表明,随着人类干扰强度的增加,植物群落地上部分有机碳储量逐渐降低,由禾草-矮嵩草群落的(134.7±17.3)gC/m2逐渐降低到杂类草-黑土滩次生裸地(18.96±6.18)gC·m-2。土壤、植物地下部分有机碳贮量呈单峰曲线变化,草毡表层开裂子阶段最高,分别为(49.7±0.83)gC·kg-1和(3596.7±179.8)gC·m-2。;杂类草-黑土滩阶段最低,分别为(19.2±1.13)gC·kg-1和(121.6±6.1)gC·m-2。受植物地下部贮碳的影响,土壤-植被系统呈现逐渐降低的变化特征。随人类活动干扰的加强,高寒嵩草草地植物有机碳地下/地上分配比发生巨大改变,草地草毡表层厚度不高于4.3cm是保证草地生产与生态服功能双赢的重要指标。     

青海省高寒草甸不同退化阶段土壤无机碳分异特征

采用时空转换的方法,选取青海省高寒草甸退化演替过程中典型退化阶段,探讨高寒草甸不同退化阶段土壤无机碳(SIC)含量及储量分异特征。结果表明:禾草-矮嵩草群落、小嵩草群落、小嵩草剥蚀期和黑土滩型退化草地0~50 cm土层SIC总储量分别为0.45、0.10、0.13和1.10 kg C·m-2;0~50 cm土层范围内,禾草-矮嵩草群落与黑土滩型退化草地存在明显的碳酸盐淀积层(主要在30 cm土层以下),而小嵩草群落和小嵩草剥蚀期在剖面内无明显的碳酸盐淀积层;草甸草毡表层特征(厚度、破碎度等)以及土壤容重、pH值与SIC变化特征存在某种协同演化关系;高寒草甸退化与无机碳储量之间没有明显的耦合作用,只有当草甸极度退化(黑土型退化草地)时,草甸SIC分层及总储量特征才表现出明显的差异。     

青藏高原高寒矮嵩草草甸碳增汇潜力估测方法

以广布于青藏高原的高寒矮嵩草草甸为研究对象,研究了草甸碳储存的场所、碳库容量随草甸演替的变化过程及其碳增汇潜力的空间分布格局,同时探讨了高寒草甸碳增汇潜力估测的困惑与解决方法。结果表明,高寒草甸生态系统碳增汇潜力空间分布格局差异极大,主要受到土层厚度和草地演化进程的影响。高寒草甸碳主要贮存于草毡表层,其增汇潜力在于退化草地草毡表层的恢复与重建。保持适宜厚度的草毡表层是协调高寒草甸生产与碳生态服务功能的关键。随着退化高寒草甸的恢复,土壤容重呈现下降趋势,计算其系统碳增汇潜力,需要用根土体积比进行土层深度的校正。高寒草甸具有较大的固碳潜力,但其潜力的发挥受到气候和草地恢复与管理措施的影响,比较漫长。     

江河源区高山嵩草(Kobresia pygmaea)草甸植物和土壤碳、氮储量对覆被变化的响应

以青海省果洛州藏族自治州甘德县青珍乡高山嵩草Kobresia pygmaea草甸轻度退化草地和重度退化草地为研究对象,通过植物地上部分主要功能群(禾草类、杂类草、莎草类)、植物根系和土壤碳、氮浓度及储量动态研究,结果表明:高寒小嵩草草甸轻度退化草地地上部分主要功能群碳、氮浓度和C ∶ N比值明显高于重度退化草地的浓度.同一草地类型主要功能群比较,碳、氮浓度依次为杂类草>禾草类>莎草类;植物地上部分的碳、氮浓度明显高于地下根系的碳、氮浓度.重度退化草地植物根系碳、氮浓度高于轻度退化草地植物根系碳、氮浓度.重度退化草地土壤总有机碳浓度显著低于轻度退化草地土壤总有机碳浓度,随着土层的加深碳、氮浓度有减少的趋势.江河源区高山嵩草草甸的土壤有机碳、氮储量最大,植物根系碳、氮储量居中,植物地上部分碳、氮储量最小.重度退化草地总有机碳储量(13554.3 g/m2)较轻度退化草地储量(14669.2 g/m2)下降7.60%.其中,0～40cm土壤层碳储量下降4.10%,植物根系碳储量下降59.97%,植物地上部分碳储量下降15.39%;重度退化草地总氮储量(3780.6 g/m2)较轻度退化草地储量(3352.7 g/m2)高12.76%,其中,0～40cm土壤中总氮储量高13.07%,植物根系全氮储量下降55.09%,植物地上部分全氮下降16.00%.由于草地退化损失有机碳11149 kg/hm2,而全氮增加4278 kg/hm2.     

高寒草甸不同扰动斑块植物功能群和根土复合体特征变化研究

高原鼠兔(Ochotona curzoniae)活动在高寒草甸上会形成各种类型扰动斑块, 扰动斑块类型的转变是导致草地退化的原因之一。目前, 斑块类型发生转变的关键影响因子尚不清楚, 因此, 对高寒草甸活动斑块、非活动斑块和恢复斑块三个扰动斑块类型植物功能类群结构、根土复合体特征和斑块分布特征进行研究, 旨在探讨斑块类型发生转变的主要因子, 说明高寒草甸退化机理。研究结果表明, 高寒草甸中活动斑块土壤表层由于放牧和高原鼠兔活动扰动强度大, 无法形成稳定的植物群落, 非活动斑块的植物群落处于次生演替早期阶段, 但是恢复斑块已具备高寒草甸优势种莎草科植物生长的基本条件。退化高寒草甸中活动斑块与非活动斑块呈现镶嵌性分布, 而恢复斑块相对独立没有镶嵌性分布现象。造成高寒草甸干扰斑块类型转变的主要原因是高原鼠兔活动强度由间歇性干扰转变为持续干扰的结果。     

Changes in plant biomass and species composition of alpine <Emphasis Type="Italic">Kobresia</Emphasis> meadows along altitudinal gradient on the Qinghai-Tibetan Plateau

Alpine Kobresia meadows are major vegetation types on the Qinghai-Tibetan Plateau. There is growing concern over their relationships among biodiversity, productivity and environments. Despite the importance of species composition, species richness, the type of different growth forms, and plant biomass structure for Kobresia meadow ecosystems, few studies have been focused on the relationship between biomass and environmental gradient in the Kobresia meadow plant communities, particularly in relation to soil moisture and edaphic gradients. We measured the plant species composition, herbaceous litter, aboveground and belowground biomass in three Kobresia meadow plant communities in Haibei Alpine Meadow Ecosystem Research Station from 2001 to 2004. Community differences in plant species composition were reflected in biomass distribution. The total biomass showed a decrease from 13196.96±719.69 g/m2 in the sedge-dominated K. tibetica swamp to 2869.58±147.52 g/m2 in the forb and sedge dominated K. pygmaea meadow, and to 2153.08±141.95 g/m2 in the forbs and grasses dominated K. humilis along with the increase of altitude. The vertical distribution of belowground biomass is distinct in the three meadow communities, and the belowground biomass at the depth of 0-10 cm in K. tibetica swamp meadow was significantly higher than that in K. humilis and K. pygmaea meadows (P＜0.01). The herbaceous litter in K. tibetica swamp was significantly higher than those in K. pygnaeca and K. humilis meadows. The effects of plant litter are enhanced when ground water and soil moisture levels are raised. The relative importance of litter and vegetation may vary with soil water availability. In the K. tibetica swamp, total biomass was negatively correlated to species richness (P＜0.05); aboveground biomass was positively correlated to soil organic matter, soil moisture, and plant cover (P＜0.05); belowground biomass was positively correlated with soil moisture (P＜0.05). However, in the K. pygnaeca and K. humilis meadow communities, aboveground biomass was positively correlated to soil organic matter and soil total nitrogen (P＜0.05). This suggests that the distribution of biomass coincided with soil moisture and edaphic gradient in alpine meadows.     

Changes in plant biomass and species composition of alpine Kobresia meadows along altitudinal gradient on the Qinghai-Tibetan Plateau

Alpine Kobresia meadows are major vegetation types on the Qinghai-Tibetan Plateau. There is growing concern over their relationships among biodiversity, productivity and environments. Despite the im-portance of species composition, species richness, the type of different growth forms, and plant bio-mass structure for Kobresia meadow ecosystems, few studies have been focused on the relationship between biomass and environmental gradient in the Kobresia meadow plant communities, particularly in relation to soil moisture and edaphic gradients. We measured the plant species composition, her-baceous litter, aboveground and belowground biomass in three Kobresia meadow plant communities in Haibei Alpine Meadow Ecosystem Research Station from 2001 to 2004. Community differences in plant species composition were reflected in biomass distribution. The total biomass showed a de-crease from 13196.96±719.69 g/m2 in the sedge-dominated K. tibetica swamp to 2869.58±147.52 g/m2 in the forb and sedge dominated K. pygmaea meadow, and to 2153.08±141.95 g/m2 in the forbs and grasses dominated K. humilis along with the increase of altitude. The vertical distribution of below-ground biomass is distinct in the three meadow communities, and the belowground biomass at the depth of 0-10 cm in K. tibetica swamp meadow was significantly higher than that in K. humilis and K. pygmaea meadows (P<0.01). The herbaceous litter in K. tibetica swamp was significantly higher than those in K. pygnaeca and K. humilis meadows. The effects of plant litter are enhanced when ground water and soil moisture levels are raised. The relative importance of litter and vegetation may vary with soil water availability. In the K. tibetica swamp, total biomass was negatively correlated to species richness (P<0.05); aboveground biomass was positively correlated to soil organic matter, soil moisture, and plant cover (P<0.05); belowground biomass was positively correlated with soil moisture (P<0.05). However, in the K. pygnaeca and K. humilis meadow communities, aboveground biomass was posi-tively correlated to soil organic matter and soil total nitrogen (P<0.05). This suggests that the distribu-tion of biomass coincided with soil moisture and edaphic gradient in alpine meadows.     

基于地形因素的高寒草甸土壤温湿度和物种多样性与初级生产力关系研究

山地是高寒草甸的主要分布区,地形变化引起了土壤温湿度和物种的差异性分布,进而影响到草地生态系统生产功能。为明晰高寒草甸山地环境因子(土壤温湿度)和物种多样性(丰富度、多度、均匀度、优势度)与初级生产力的关系,本研究以青藏高原东北缘马牙雪山支脉的高寒草甸山体为研究对象,选择阶地、阴坡、山脊和阳坡与3个海拔梯度段,调查了189个样方的植物群落组成和土壤温湿度。采用线性回归法分析土壤温湿度和物种多样性与初级生产力之间的关系。结果表明:(1)以山地高寒草甸整体为研究单元,初级生产力只随物种多度的增加而显著增加(R~2=0.07 P=0.01)。(2)坡向影响初级生产力的因素不同,阴坡初级生产力与物种丰富度正线性相关;山脊初级生产力与土壤湿度正线性相关,也随物种丰富度增加而显著增加;阳坡初级生产力与物种多度正线性相关;阶地初级生产力随均匀度增加而显著增加,随优势度增加而显著降低。(3)只有低海拔区(2860-2910 m)初级生产力随物种多度和丰富度的增加而显著增加。综上所述,山地高寒草甸土壤温湿度和物种多样性与初级生产力关系受坡向比海拔的影响更大,且物种多样性对初级生产力的影响大于土壤温湿度。建议山地高寒草甸生态系统生产和生态管理过程中要重点考虑坡向对植物多样性和初级生产力的影响。     

高寒草毡层基本属性与固碳能力沿水分和海拔梯度的变化

高寒草毡层是高原寒区自然植被下形成的松软而坚韧且耐搬运的表土层,认识其生态功能是促进草牧业生产休养保护和工程施工主动利用的前提。通过对青藏高原东部若尔盖高原植被的广泛调查,在布设沼泽、退化沼泽、沼泽化草甸、湿草甸、干草甸和退化草甸水分梯度群落样地,以及亚高山草甸、亚高山灌丛草甸、高山灌丛草甸和高山草甸海拔梯度群落样地的基础上,通过对不同类型群落样地草毡层容重、土壤颗粒组成和土壤有机碳(SOC)含量的测定分析,比较了水分和海拔梯度下草毡层固碳能力。结果表明,草毡层厚度平均为30cm,沼泽湿地草毡层容重最小,SOC含量在300g/kg以上;退化草甸容重最高,SOC含量显著下降。不同群落草毡层SOC密度在10—24kg C/m~2之间,随着土壤水分有效性的降低而降低;高山灌丛草甸草毡层SOC密度比草甸高15%。研究得出,保持草毡层稳定的质量含水量阈值为30%,SOC含量阈值为30g/kg;高寒植被草毡层在沼泽到草甸的退化演替中,容重、紧实度变大,有机碳含量减少,碳密度和碳储量下降;灌丛草甸的固碳能力大于草甸,但灌丛草甸的生产功能降低;保持可持续发展的草地生产能力,维护固碳生态功能,需要防止草毡层退化,抑制草甸向灌丛草甸演替。     

祁连山东段高原鼢鼠对高寒草甸危害评价

为了客观评价高原鼢鼠(Myospalax baileyi)对高寒草甸的危害程度,在祁连山东段研究了高原鼢鼠不同种群密度与草地质量之间的关系,共设置了3个高原鼢鼠种群密度梯度,调查了3个危害等级变量(鼠丘数、鼠丘面积和鼠丘产草量)和6个生境变量(草地产草量、总盖度、可食牧草产量、植被组成、土壤水分和土壤紧实度),通过One-Way ANOVA检验法研究这些因子与高原鼢鼠危害程度的关系。结果表明:在设置的3个种群密度梯度下,草地产草量、总盖度、可食牧草产量和鼠丘产草量无显著性差异;草地植物群落结构、新鼠丘面积占调查区面积的比例无显著性差异,除高原鼢鼠采食深度(0—20 cm)外,3个种群密度区土壤紧实度无显著性差异,而0—30 cm处土壤水分存在显著性差异,说明本研究中不同高原鼢鼠种群密度区的草地质量没有显著性差异。此外,研究结果表明调查样地大小与危害评价有着密切关系,在高寒草甸区,单个样方调查面积以0.5 hm~2以上为宜。     

祁连山北麓高原鼢鼠栖息地选择要素

Studying the habitat characteristics and habitat selection of the plateau zokor in different grassland types is very important to understand the function and position of the zokor in these grassland ecosystems. We selected the plateau zokor inhabiting in the alpine meadow, alpine shrub meadow and alpine grassland located in northern Qilian Mountain to describe habitatcharacteristics and study its habitat selection by dividing five plots in each grassland according to the zokor’s mounds densities, which can be regarded as relative population density of zokors. We investigated soil compaction, soil moisture, soil temperature, soil pH, as well as plant community structure in each plot of three grassland types. One-Way ANOVAs showed that there were significant differences in vegetation and soil among the three grassland types. Soil compaction, soil temperature, and total plant species number in alpine meadow were the highest (P<0.05), soil moisture and total vegetation coverage in alpine shrub meadow were the highest (P<0.05), soil pH in alpine grassland was the highest (P<0.05). Correlation analysis showed that soil compaction was negatively correlated with the relative population density of the zokor (P<0.05). Stepwise linear regression analysis showed that the plateau zokor preferred habitat with lower compaction, richer forbs in alpine meadow, lower compaction in alpine shrub meadow, and lower compaction, higher soil moisture, richer sedges in alpine grassland. In the three grassland types, we found that the soil compaction was the key factor of habitat selection of the plateau zokor and food resources was the secondary factor.     

Landscape patterns of CH4 fluxes in an alpine tundra ecosystem

We measured CH₄ fluxes from three major plant communities characteristic of alpine tundra in the Colorado Front Range. Plant communities in this ecosystem are determined by soil moisture regimes induced by winter snowpack distribution. Spatial patterns of CH₄ flux during the snow-free season corresponded roughly with these plant communities. InCarex-dominated meadows, which receive the most moisture from snowmelt, net CH₄ production occurred. However, CH₄ production in oneCarex site (seasonal mean=+8.45 mg CH₄ m^–2 d^–1) was significantly larger than in the otherCarex sites (seasonal means=–0.06 and +0.05 mg CH₄ m^–2 d^–1). This high CH₄ flux may have resulted from shallower snowpack during the winter. InAcomastylis meadows, which have an intermediate moisture regime, CH₄ oxidation dominated (seasonal mean=–0.43 mg CH₄ m^–2 d^–1). In the windsweptKobresia meadow plant community, which receive the least amount of moisture from snowmelt, only CH₄ oxidation was observed (seasonal mean=–0.77 mg CH₄ m^–2 d^–1). Methane fluxes correlated with a different set of environmental factors within each plant community. In theCarex plant community, CH₄ emission was limited by soil temperature. In theAcomastylis meadows, CH₄ oxidation rates correlated positively with soil temperature and negatively with soil moisture. In theKobresia community, CH₄ oxidation was stimulated by precipitation. Thus, both snow-free season CH₄ fluxes and the controls on those CH₄ fluxes were related to the plant communities determined by winter snowpack.     

Plant community and soil available nutrients drive arbuscular mycorrhizal fungal community shifts during alpine meadow degradation

Arbuscular mycorrhizal fungi (AMF) play an important role in maintaining the function and sustainability of grassland ecosystem, but they are also susceptible to environmental changes. In recent decades, alpine meadows on the Tibetan Plateau have experienced severe degradation due to the impact of human activities and climate change. But it remains unclear how degradation affects the AMF community, a group of functionally important root associated microorganisms, which potentially limit the development and application of microbial technologies in the restoration of degraded grasslands. In this study, we investigated AMF communities richness and composition in non-degraded (ND), moderately degraded (MD) and severely degraded (SD) alpine meadows on the Tibetan Plateau, and then explored their main biotic and abiotic determinants. Alpine meadow degradation significantly reduced plant community biomass, richness, soil organic carbon, total nitrogen, total phosphorus, available nitrogen and available phosphorus, but increased soil pH. AMF community composition and the iesdominant family and genera differed significantly among different degradation stages. Grassland degradation shifted the AMF community composition in favor of Claroideoglomus over Rhizophagus, and resulted in a marked loss of Glomeraceae and the dominance of Diversisporaceae. Alpine meadow degradation significantly increased AMF hyphal density and richness, likely working as a plant strategy to relieve nutrient deficiencies or loss as a result of degradation. The structural equation model showed that AMF community richness and composition were significantly influenced by plant community, followed by soil available nutrients. Soil available nutrients was the key contributor to the increased AMF hyphal density and richness during grassland degradation. Our findings identify the effects of alpine meadow degradation on AMF richness and highlight the importance of the plant community in shaping the AMF community during alpine meadow degradation. These results suggest that plant community restoration should be the primary goal for the ecological restoration of degraded alpine meadows, and these soil functional microorganisms should be simultaneously integrated into ecological restoration strategies and management.     

祁连山中段高寒草甸草毡表层发育程度的空间分异及环境影响因子

高寒草甸植被下的草毡表层能够发挥水土保持、水源涵养等生态环境效益,是高寒草甸植被生态功能发挥的核心,认识草毡表层发育程度的空间分异及环境影响因子有利于深入理解高寒草甸在高原生态系统中的作用。本研究以祁连山中段高寒草甸分布区为研究区,依据根系体积并结合草毡层厚度以及土壤容重,将草毡表层划分为弱发育、中等发育以及强发育草毡。分析了不同发育程度草毡的地形、植被、气候等环境特征,并采用支持向量机模型对其分布进行了空间制图。结果表明:祁连山中段发育程度较高的草毡表层趋向于分布在水分条件较好的低海拔、缓坡,低坡位以及北向坡的位置,以嵩草属植物为主,中等以上发育程度的草毡地表植被及水分条件都较好;发育程度较高的草毡表层年均温较高,各发育程度草毡表层降水量差异不显著。空间分布结果整体与现有的高寒草甸植被类型分布具有高度的一致性,但空间分辨率更为详细,并且实现了不同发育程度草毡表层的空间细分。