放牧管理模式对高寒草甸鼢鼠鼠丘群落演替的影响

高寒草甸放牧利用下高原鼢鼠(Eospalax baileyi)等危害的发生是草地管理的关键难题,分析放牧管理模式对鼢鼠鼠丘植被群落演替的影响能为草地管理提供重要依据。研究选择划区轮牧(RG)、生长季休牧(GSG)、连续放牧(CG)和禁牧(PG)4种放牧管理模式,以及各模式下不同年限鼠丘(一年(ZM1)、两年(ZM2)、三年(ZM3)和多年鼠丘(ZMM))与对照(CM)草地。分析不同放牧管理模式对鼠丘植被群落特征和生物量等的影响,结果发现:PG和GSG下所有年限鼠丘的植被高度、地上生物量均高于RG和CG;RG和GSG下ZM1和ZM2物种Shannon-wiener指数均高于对照样地物种Shannon-wiener指数。主成分分析表明:RG下地上生物量和物种丰富度指数是影响鼠丘植被群落演替的重要因子,PG下地上生物量、盖度、Shannon-wiener指数和均匀度指数是鼠丘植被群落演替的重要因子,CG下物种丰富度和重要值是影响鼠丘植被群落演替的重要指标,GSG下Shannon-wiener指数、盖度和高度是影响鼠丘植被群落演替的重要指标。可见,不同放牧制度对鼠丘植被群落演替的影响不同,禁牧和生长季休牧管理模式能够较好地恢复鼠丘植被群落演替。     

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。     

高原鼢鼠干扰下高寒草甸大型土壤动物多样性对环境因子的响应

为研究高寒草甸大型土壤动物群落组成和分布对环境因子的响应,选取祁连山东段的甘肃省天祝县高原鼢鼠典型分布区域,以鼠丘密度代表干扰强度设置4个干扰区。调查各干扰区植被群落特征、土壤理化性质、大型土壤动物类群组成及其数量,采用约束性排序方法分析环境因子对大型土壤动物类群组成和分布的影响。结果表明：高原鼢鼠干扰下高寒草甸大型土壤动物优势类群为瓦娄蜗牛科、象甲科和短角亚目幼虫;极重度干扰区大型土壤动物类群的丰度、丰富度、Shannon指数显著高于重度干扰区（P<0.05）;多元回归分析表明大型土壤动物类群丰度、丰富度和Shannon指数与土壤温度呈显著负相关（P<0.05）,丰富度与土壤含水量呈显著负相关（P<0.05）,丰度与土壤紧实度呈显著负相关（P<0.05）,丰富度和Shannon指数与植物Shannon指数呈显著负相关（P<0.05）;冗余分析和偏冗余分析表明,土壤温度、紧实度和含水量是影响高寒草甸大型土壤动物类群组成和分布的主要环境因子。     

克氏针茅草原群落物种多样性与生物量关系对放牧强度的响应

放牧强度引起的草原植物群落物种多样性与地上生物量变化是近年来草地生态系统研究的热点问题。以内蒙古锡林郭勒克氏针茅草原为研究对象,探究植物群落结构特征、物种多样性与地上生物量之间相互关系及其对不同放牧强度的响应。结果表明：随着放牧强度的增加植物群落结构逐步向退化方向演替;植物群落高度逐渐降低（P<0.05）,密度逐渐增加（P<0.05）,盖度总体呈下降趋势（P<0.05）;植物群落和原有群落优势种地上生物量总体呈下降趋势（P<0.05）,而退化指示物种的地上生物量逐渐增加（P<0.05）;轻度、中度放牧条件下群落物种Margalef指数、Pielou指数、Simpson指数均显著高于重度放牧（P<0.05）;地上生物量与Shannon-Wiener指数、Margalef指数和Pielou指数呈正相关关系,而与Simpson指数呈负相关关系。综上所述,克氏针茅草原植物群落结构和功能在不同放牧强度下产生不同的响应,适度放牧有利于提高群落物种多样性与生物量。     

不同形成时间高原鼢鼠鼠丘土壤养分分配规律

高原鼢鼠(Myospalax baileyi)作为青藏高原唯一营地下生活的鼠类,其造丘活动不仅能影响草地群落演替的方向和进程,而且对鼠丘土壤养分含量和分配造成空间异质性。关于不同形成时期的高原鼢鼠鼠丘养分含量及在垂直高度的分配规律研究报道尚少。基于此本研究以不同形成时期的鼢鼠鼠丘为研究对象,对鼠丘土壤养分含量及空间分配规律进行探讨。结果表明:随着鼠丘形成时间的推移,土壤养分总体表现为:1年鼠丘多年鼠丘对照区;与非鼠丘区相比,随着土壤土层增加,土壤养分未呈现规律性的变化。其中,土壤全氮和速效氮含量表现为1年鼠丘3年鼠丘5年鼠丘对照区;0—10cm土壤全磷和速效磷含量变化总体表现为多年鼠丘1年鼠丘对照区,10—30cm土层1年鼠丘土壤中全磷和速效磷含量最高。土壤速效钾和有机质含量随着鼠丘形成时间推移总体表现为:1年鼠丘5年鼠丘3年鼠丘;其中在10—30cm土层,1年鼠丘速效钾和有机质含量显著高于多年鼠丘和对照区。由此可见,高原鼢鼠造丘活动能显著改变土壤养分分配格局,短期内形成养分富集的肥力岛,为鼠丘土壤种子库中种子的萌发和植被生长提供必需的养分保证。     

放牧干扰下高原鼢鼠栖息地选择因素

以祁连山东段高寒草甸栖息的高原鼢鼠(Myospalax baileyi)为研究对象,探讨放牧干扰下高原鼢鼠适合栖息地选择的影响因素,为合理控制草原鼠害和保护生物多样性提供科学依据。在5个不同放牧强度小区中,连续3年监测高原鼢鼠相对种群密度变化,同时获取植被和土壤的变化数据。分析高原鼢鼠相对种群密度、植被(盖度、高度、频度、植被生物量、植被均匀度、丰富度、多样性和地下根系生物量)和土壤(紧实度、容重、水分)之间的关系。中度放牧干扰下,高原鼢鼠相对种群密度最低,不利于对栖息地的选择,轻度、次轻度放牧区的高原鼢鼠相对种群密度高于重度、次重度放牧区的;轻度放牧干扰的草地有利于高原鼢鼠种群数量的增加。高原鼢鼠相对种群密度与土壤紧实度、容重呈显著负相关(R=﹣0.921、﹣0.883,P0.05);与土壤水分呈显著正相关(R=0.879,P0.05);高原鼢鼠相对种群密度与地下根系生物量呈极显著正相关(R=0.982,P0.01),与植被丰富度呈显著正相关(R=0.921,P0.05),与地上植被总盖度呈显著正相关(R=0.909,P0.05),与地上生物量、均匀度、多样性呈不显著正相关(P0.05)。在草地放牧干扰系统中,非生物因素土壤紧实度、水分可能是高原鼢鼠栖息地选择的首要选择因素,食物资源也许是次要选择因素。     

半干旱草地不同植物枯落物分解对放牧和封育的响应

为探究放牧和封育对半干旱草地植物枯落物分解的影响,选取赖草、牛枝子及其混合物为研究对象,调查了不同网孔分解袋中宁夏半干旱草地植物枯落物分解特征及对放牧和封育的响应规律。结果表明：（1）放牧样地250目网孔中,枯落物质量残留率表现为牛枝子显著高于赖草和混合物（P<0.05）,而在放牧样地30目网孔、封育样地2种网孔中,枯落物质量残留率均表现为3种枯落物间无显著差异。（2）250目网孔中,放牧和封育样地枯落物分解衰减常数均表现为混合物显著高于牛枝子,而赖草居中;并且,牛枝子枯落物分解衰减常数表现为封育样地显著高于放牧样地。30目网孔中,放牧和封育样地枯落物分解衰减常数均表现为赖草、混合物显著高于牛枝子（P<0.05）;并且,牛枝子枯落物分解衰减常数表现为封育样地显著高于放牧样地（P<0.05）。（3）在放牧样地,仅牛枝子枯落物R_m表现为30目显著低于250目网孔（P<0.05）,k表现为30目显著高于250目网孔（P<0.05）;土壤动物对枯落物分解的贡献率表现为混合物显著低于牛枝子,赖草居中（P<0.05）。而在封育样地,仅牛枝子枯落物k表现为30目显著高于250目网孔（P<0.05）;土壤动物对枯落物分解的贡献率表现为混合物和牛枝子均显著高于赖草,且混合枯落物的土壤动物贡献率表现为封育样地显著高于放牧样地（P<0.05）。（4）枯落物残留率与其初始N、P、木质素/N、C/P呈显著相关性（P<0.05）;枯落物分解衰减常数与其初始N、P、木质素、N/P、C/P和木质素/P间均呈显著相关性（P<0.05）。研究表明,植物种类组成显著影响枯落物的残留率和分解衰减常数。放牧与封育管理通过影响网孔中土壤动物分布来调控半干旱区草地植物枯落物的分解,而且封育管理更有利于促进土壤动物对低质量枯落物（牛枝子）的分解。     

放牧强度对内蒙古荒漠草原土壤有机碳及其空间异质性的影响

放牧是内蒙古荒漠草原主要利用方式之一,研究不同放牧强度下土壤有机碳分布规律对退化草原恢复以及推广精准放牧技术具有重要的指导意义。基于不同放牧强度长期放牧样地（0、0.93、1.82、2.71羊单位hm^-2（a/2）^-1）,采用高样本数量的取样设计并结合地统计学分析方法,研究荒漠草原土壤有机碳及其空间异质性。结果表明：中度放牧会显著降低0-30 cm土层全氮含量（P<0.05）,全磷含量随放牧强度增强出现先降低后升高趋势;放牧样地土壤有机碳含量均显著低于对照样地（P<0.05）,不同放牧强度处理土壤有机碳含量没有显著差异;土壤有机碳密度受放牧影响在0-20 cm土层出现显著下降（P<0.05）,变化趋势同有机碳含量相似,碳氮比在重度放牧区0-10 cm土层显著降低（P<0.05）。土壤有机碳空间异质性和异质性斑块的破碎程度随放牧强度增加而增大;土壤有机碳含量与海拔高度在对照、轻度放牧和中度放牧区均呈极显著负相关（P<0.01）,在重度放牧区土壤有机碳含量和海拔无显著相关性;土壤有机碳含量与土壤全氮、全磷含量均呈极显著正相关（P<0.01）。综上所述,放牧降低土壤有机碳含量,提高土壤有机碳空间异质性,土壤有机碳含量的空间变异受海拔和土壤养分含量等因素的共同影响。     

黄土高原草地根系生物量沿环境梯度变化规律

草地是陆地生态系统的重要组成部分，根系生物量是研究草地生态系统的重要参数之一，研究草地根系生物量沿环境梯度的变化规律对当地的植被建设和恢复具有重要意义。以黄土高原3种不同草地类型（森林草原、典型草原和荒漠草原）为研究对象，沿环境梯度从东到西选择10个样地，每个样地内设置8个1 m×1 m样方进行根系生物量的调查，旨在分析不同草地类型根系生物量的垂直分布规律，并探讨了根系生物量沿环境梯度的变化规律及其影响因素。结果表明：（1）黄土高原3种草地类型根系生物量有显著差别（P<0.05），其中森林草原的根系生物量最大，典型草原最小；（2）3种不同草地类型根系生物量垂直分布均呈"T"型，土壤表层（0-10 cm）占55%以上的根系生物量，且荒漠草原根系有更多比例的生物量分布在土壤表层；（3）黄土高原草地根系生物量沿经度从东到西呈现先减少后缓慢增加的趋势，但浅层生物量与深层生物量比例（浅深比）没有表现出明显的经度格局；（4）总根系生物量的变化主要受年均温（MAT）影响（P<0.01），随MAT增大而增大；深层生物量同时受气候和土壤养分含量的影响（P<0.01）；浅深比则与样点平均土壤全磷含量、深层土壤全磷含量有显著负相关性（P<0.05）；（5）气候和土壤因素能解释根系生物量5.12%-39.36%的变异，独立作用中，气候因子对根生物量的解释度最大，可达到2.77%-9.12%的解释度。     

不同修复措施对黄河源退化高寒草甸植物群落与土壤养分的影响

为了揭示退化高寒草甸逆向转变的驱动因子，通过野外调查和室内分析相结合的方法探究了黄河源不同修复措施（施有机肥F、免耕补播N、施有机肥+免耕补播FN）处理高寒草甸植物群落特征、土壤理化性质和两者相关性的变化规律，阐明不同修复措施对黄河源退化高寒草甸植物群落与土壤养分的影响。结果表明：免耕补播显著增加草甸物种丰富度指数（P<0.05）；施有机肥+免耕补播显著增加草甸植物盖度、总生物量、Shannon Wiener多样性指数和Pielous均匀度指数（P<0.05）。不同人工修复后草甸植物功能群地上、地下生物量变化趋势基本一致（除豆科）。和对照相比，莎草科，杂类草地上和地下生物量含量在N、FN处理分别降低83.04%、73.86%、30.43%、92.37%和96.51%、84.09%、85.68%、95.36%；禾本科地上和地下生物量含量在F、N和FN处理分别增加7.29%、23.45%、17.93%和6.04%、4.03%、10.52%；豆科地上生物量含量基本保持不变，地下生物量含量在F、N和FN处理分别降低24.43%、82.19%和42.61%。F显著增加土壤有机碳含量（P=0.033）；N显著降低土壤NO₃^--N含量（P=0.009）；FN显著降低土壤pH和增加土壤速效磷含量（P=0.024）；F和FN显著增加土壤含水量（P=0.000），N则显著降低土壤含水量（P=0.000）；F显著降低土壤容重（P=0.018）。相关性分析表明植物Shannon Wiener多样性和Pielous均匀度与土壤速效磷含量呈显著正相关（P=0.037；P=0.033），土壤有机碳和含水量与总生物量呈显著正相关（P=0.027；P=0.032），pH与盖度呈显著负相关（P=0.049）。冗余度分析结果表明土壤有机碳含量和含水量显著影响了植物群落结构特征，解释率分别为30.3%和19.7%。研究结果表明，因地制宜进行退化高寒草甸施有机肥+免耕补播修复措施，能够明显提高草地生产力，改善草甸植物群落及其土壤养分和水分环境。     

Interactive effects of soil-dwelling ants, ant mounds and simulated grazing on local plant community composition

Interactions between aboveground vertebrate herbivores and subterranean yellow meadow ants (Lasius flavus) can drive plant community patterns in grassland ecosystems. Here, we study the relative importance of the presence of ants (L. flavus) and ant mounds under different simulated grazing regimes for biomass production and species composition in plant communities. We set up a greenhouse experiment using intact soil cores with their associated vegetation.We found that plant biomass production in the short term was affected by an interaction between simulated grazing (clipping) and ant mound presence. Clipping homogenized production on and off mounds, while in unclipped situations production was higher off than on mounds. During the experiment, these differences in unclipped situations disappeared, because production on unclipped mounds increased. Plant species richness was on average higher in clipped treatments and patterns did not change significantly over the experimental period. Plant community composition was mainly affected by clipping, which increased the cover of grazing-tolerant plant species. The actual presence of yellow meadow ants did not affect plant community composition and production.We conclude that the interaction between ant mounds and clipping determined plant community composition and biomass production, while the actual presence of ants themselves was not important. Moreover, clipping can overrule effects of ant mounds on biomass production. Only shortly after the cessation of clipping biomass production was affected by ant mound presence, suggesting that only under low intensity clipping ant mounds may become important determining plant production. Therefore, under low intensity grazing ant mounds may drive the formation of small-scale plant patches.     

Effects of Erosion from Mounds of Different Termite Genera on Distinct Functional Grassland Types in an African Savannah

A key aspect of savannah vegetation heterogeneity is mosaics formed by two functional grassland types, bunch grasslands, and grazing lawns. We investigated the role of termites, important ecosystem engineers, in creating high-nutrient patches in the form of grazing lawns. Some of the ways termites can contribute to grazing lawn development is through erosion of soil from aboveground mounds to the surrounding soil surface. This may alter the nutrient status of the surrounding soils. We hypothesize that the importance of this erosion varies with termite genera, depending on feeding strategy and mound type. To test this, we simulated erosion by applying mound soil from three termite genera (Macrotermes, Odontotermes, and Trinervitermes) in both a field experiment and a greenhouse experiment. In the greenhouse experiment, we found soils with the highest macro nutrient levels (formed by Trinervitermes) promoted the quality and biomass of both a lawn (Digitaria longiflora) and a bunch (Sporobolus pyramidalis) grass species. In the field we found that soils with the highest micro nutrient levels (formed by Macrotermes) showed the largest increase in cover of grazing lawn species. By linking the different nutrient availability of the mounds to the development of different grassland states, we conclude that the presence of termite mounds influences grassland mosaics, but that the type of mound plays a crucial role in determining the nature of the effects.     

高原鼢鼠干扰对三江源区高寒草甸群落特征的影响

高原鼢鼠是三江源高寒草甸区域的主要啮齿动物之一.它啃食植物根系,挖掘大量通道,并将挖掘出的土壤堆积于地表,形成覆盖于植物地上部分的裸露土丘,对草地群落特征会产生不同程度的影响.本研究以高原鼢鼠土丘密度表示高原鼢鼠对草地的干扰程度,选取7个不同高原鼢鼠土丘密度的样地,同时选取没有遭受高原鼢鼠干扰的样地作为对照,获得各样地的物种信息及地上、地下生物量,探讨不同高原鼢鼠干扰强度对草地群落的物种组成、物种多样性及群落生产力的影响.结果表明: 随着高原鼢鼠土丘的增加,草地植物优势种群发生由以莎草科和禾本科植物为主向珠牙蓼、鹅绒委陵菜、西伯利亚蓼等杂类草植物为主的转变,群落盖度和高度显著降低;轻度或中度的高原鼢鼠干扰能够提高群落的物种多样性,而群落均匀度指数变化不显著;群落生产力不存在类似中度干扰假说的结果.随高原鼢鼠干扰活动的增强,群落地上、地下及总生物量显著降低,群落生产力大幅度降低.     

高原鼢鼠土丘对矮嵩草草甸植被演替及土壤营养元素的作用

本文研究了矮蒿草草甸上高原酚鼠土丘的出现率及其对植被的覆盖状况,土丘高度的下降及其直径的变化,土丘植物地上生物量和土丘营养元素含量。高原鼢鼠土丘出现率为242个/只/年,合土壤干重为1023.82公斤/只/年,对植被的覆盖面积高达22.53平方米/只/年。土丘在地表滞留时间约1年,处于不同演替阶段植被区域内出现的土丘,其植物地上生物量间的差异显著。5月前,在原生植被区出现的土丘,经4个月后,土丘边缘形成环状富草区,士丘边缘至中心区形成环状贫草区,而土丘中心仍处于无草状况。在次生植被区上的土丘则无此现象。新土丘除速效钾的含量与对照区无显著差异外,速效氮、磷的含量显著地高于对照区。旧土丘土壤中的速效氮、磷、钾含量均低于新土丘,但氮、磷的含量仍高于对照区。     

Impact of Formica exsecta Nyl. on seed bank and vegetation patterns in a subalpine grassland ecosystem

The mound building ant Formica exsecta Nyl. is widely distributed in grassland ecosystems of the Central European Alps. We studied the impact of these ants on seed bank and vegetation patterns in a 11 ha subalpine grassland, where we counted over 700 active ant mounds. The mounds showed a distinct spatial distribution with most of them being located in tall‐grass, which was rarely visited by ungulates (red deer; Cervus elaphus L.). Heavily grazed short‐grass, in contrast, seemed to be completely avoided by ants as only few mounds were found in this vegetation type. The species composition of the ant mound and grassland seed banks was quite similar, i.e. from 15 common plant species 12 were found in both seed bank types. We found the same proportions of myrmecochorous seeds in ant mound and grassland soil samples. In contrast, the number of seeds was 15 times higher in mound compared with the grassland soil samples. Also, the vegetation growing on ant mounds significantly differed from the vegetation outside the mounds: graminoids dominated on ant mounds, herbaceous and myrmecochorous species in the grassland vegetation. We found significant continuous changes in vegetation composition on gradients from the ant mound centre to 1 m away from the mound edge. Overall, F. exsecta was found to have a considerable impact on seed bank and vegetation patterns in the grassland ecosystem studied. These insects not only altered grassland characteristics in the close surrounding of their mounds, but also seem to affect the entire ecosystem including, for example, the spatial use of the grassland by red deer.     

鼢鼠的造丘活动及不同休牧方式对草地植被生产力的影响

研究表明,高原鼢鼠的造丘活动在停止放牧扰动的条件下,对于过牧型退化草地而言,非但不会对草地生产力造成破坏,相反,在植被高度、植被组成和产草量等生产力构件上均表现出了显著的促进作用。在相同的休牧条件下,鼢鼠分布地植被性状的各项指标除植物多样性低于无鼢鼠分布地外,其余指标均极显著高于无鼢鼠分布地(P<0.01),其中丘缘地又极显著地高于丘间地(P<0.01);在同为3年的三种休牧方式中,实施绝对禁牧的方式最佳,其次为降低载牧量50%且于返青至6月前禁牧的方式,这两种休牧方式均可较好地满足鼠丘在退化草地植被恢复过程中充分发挥其生态功能所必需的外部条件。     

Effects of Grazing Regimes on Plant Traits and Soil Nutrients in an Alpine Steppe,Northern Tibetan Plateau

Understanding the impact of grazing intensity on grassland production and soil fertility is of fundamental importance for grassland conservation and management. We thus compared three types of alpine steppe management by studying vegetation traits and soil properties in response to three levels of grazing pressure: permanent grazing (M1), seasonal grazing (M2), and grazing exclusion (M3) in the alpine steppe in Xainza County, Tibetan Plateau. The results showed that community biomass allocation did not support the isometric hypothesis under different grassland management types. Plants in M1 had less aboveground biomass but more belowground biomass in the top soil layer than those in M2 and M3, which was largely due to that root/shoot ratios of dominant plants in M1 were far greater than those in M2 and M3. The interramet distance and the tiller size of the dominant clonal plants were greater in M3 than in M1 and M2, while the resprouting from rhizome buds did not differ significantly among the three greezing regimes. Both soil bulk density and soil available nitrogen in M3 were greater than in M1 at the 15–30 cm soil depth (P = 0.05). Soil organic carbon and soil total nitrogen were greater in M3 than in M1 and M2 (P = 0.05). We conclude that the isometric hypothesis is not supported in this study and fencing is a helpful grassland management in terms of plant growth and soil nutrient retention in alpine steppe. The extreme cold, scarce precipitation and short growing period may be the causation of the unique plant and soil responses to different management regimes.