典型草原不同演替阶段群落结构与物种多样性变化

针对退化草地恢复进程及恢复过程中的合理利用问题,选取生长季围封(4至9月)收获干草,其它时间轻度放牧利用的草地为研究对象,同时选取自由放牧草地为对照,开展典型草原围封演替过程中群落结构与物种多样性变化的研究。研究结果表明:典型草原不同演替阶段群落的物种组成基本一致,但主要物种的优势地位发生了显著改变。在自由放牧草地,以星毛萎陵菜、冷蒿、糙隐子草为优势物种,采用生长季围封恢复措施后,优良牧草羊草、克氏针茅的优势地位增加,退化草地正向演替,群落的盖度、密度、地上、地下生物量及优良牧草比例增加,群落结构优化,物种多样性增加。但若围封后连续多年(13年以上)刈割利用,容易导致群落的盖度、密度、地上、地下生物量再次下降,草地发生2次逆行演替。研究认为:季节性围封的管理方式既可保证退化草地在一定程度上得到恢复,也能避免全年围封禁牧所带来的饲草资源浪费。季节性围封在我国牧区是可行的草地管理方法,但适宜的围封季节及围封后的合理利用问题(如合理的割草制度等)有待进一步研究。     

不同保护和利用方式下羊草草原群落生物量及能量功能群构成的比较

基于野外调查数据,结合能量功能群分类方法,对不同围封年限(围封4年,围封9年,围封29年)及不同利用方式(放牧、割草)影响下羊草草原的生物量、根冠比及不同能量功能群优势度进行比较分析,结果表明:围封使得群落地上、地下总生物量增加,并随着围封年限的增加渐趋稳定。相比围封保护,放牧和打草利用均会使群落根冠比变大。5个样地比较,放牧退化对群落的能量功能群构成影响较大,相比其他样地,低能值植物功能群优势度明显增加,而中能值和高能值植物功能群则明显下降。几个围封样地和打草场样地之间则没有显出规律性变化。相比重度放牧而言,围封和打草这两种利用方式都可以使羊草草原得到很好的保护。而对于围封而言,围封3-5年后对羊草草原加以适度的利用对草原保护和经济的发展都是有利的。     

呼伦贝尔草甸草原不同退化程度羊草群落指标研究

本试验对放牧干扰下不同退化程度呼伦贝尔草甸草原羊草群落进行研究。结果发现,随着退化程度的增加,群落的平均高度、地上生物量及植物群落α多样性指数均表现出降低的趋势。各物种的重要值变化幅度很大,建群种羊草的重要值在重度退化区高于轻度退化区。随着退化程度的增加,羊草群落伴生种的重要值降低,一些耐践踏、适口性差的物种增加,一、二年生植物的重要值也呈现出增加的趋势。通过研究表明,可用群落的平均高度和地上生物量、物种α多样性指数和重要值作为放牧干扰下确定不同退化程度的植物群落学指标。     

基于CVOR指数的巴音布鲁克高寒草原健康评价

利用草地生态系统健康评价CVOR综合指数,对巴音布鲁克高寒草原生态系统2004—2012年健康状态进行评价与退化分级研究,并对引起CVOR变化的内在驱动力因素进行探讨。结果表明:(1)研究区高寒草原生态系统健康状况由一般病态(2004年CVOR=0.58)逐渐恢复为健康状态(2012年CVOR=0.72);退化状况由强度退化恢复为中度退化,但局部仍存在强度退化;(2)降水是高寒草原生态系统CVOR指数的主要限制因子,降水也是除基况外各分指数变化的重要驱动因素;在气候变化背景下,CVOR指数将上升;(3)放牧改变了围栏外的群落功能组分,围封可以改善高寒草原生态系统的健康状况,有利于植被的正向演替,过度放牧是影响高寒草原恢复和演替的重要因素。总体上,降水和放牧是影响研究区高寒草原健康状况的主要原因。     

巴音布鲁克高寒草地退化演替阶段植物群落特性研究

以新疆天山南坡巴音布鲁克高寒草地为研究对象,通过主分量分析以及群落多样性指标,分析了不同退化演替阶段高寒草地植物群落特性变化规律。结果表明:以重要值为参数通过主分量分析(PCA)对样方进行排序,得到未退化、轻度退化、中度退化、重度退化4种类型群落;随着植物群落的逆行演替,优良牧草盖度、高度、频度等呈递减趋势,杂类草表现为增加趋势,植物群落物种多样性丧失。未退化阶段群落羊茅(Festuca ovina)、紫花针茅(Stipa purpurea)为优势种,随着退化加重,天山赖草(Leymus tianschanicus)、委陵菜(Ptentilla spp.)等在群落中占主导地位,地下芽根茎型草本植物逐渐代替地面芽密丛型禾草植物成为群落优势种。     

内蒙古草原退化与恢复演替机理的探讨

1 98 3 -2 0 0 0年对内蒙古锡林河中游的典型草原放牧退化演替变型实行封育禁牧 ,并连续进行了恢复演替的动态监测 ,本文根据监测的数据及已经发表的论文 ,从生态系统、群落、种群、个体等层次上对退化草原的特征、退化序列、演替进程的诊断、恢复演替的轨迹与节奏性 ,恢复演替中的植物种群动态与植物个体变异进行了阐述 ,进而对退化与恢复演替的生态学机理提出了基本认识 :认为草原退化演替使其物质与能量流程及收支平衡失调 ,打破了生态系统自我调控的相对稳态 ,下降到低一级能量固定与转化效率的系统状态是草原退化的生态学实质     

内蒙古草原退化群落恢复演替的研究 Ⅳ.恢复演替过程中植物种群动态的分析

本文根据 1 983-1 993年退化草原群落恢复演替过程中主要植物种群地上现存量与密度的变化 ,将这些种群区分成 6种类型 :优势增长型—羊草 (Leymuschinensis) ;缓慢增长型—大针茅 (Stipa grandis) ;典型衰退型—糙隐子草 (Cleis-togenes squarrosa)和变蒿 (Artemisia commutata) ;迟滞衰退型—冷蒿 (Artemisiafrigida) ;中间过渡型—米氏冰草 (Agropyron michnoi)、双齿葱 (Allium bidenta-tum)和洽草 (Koeleria cristata) ;演替中立型—小叶锦鸡儿 (Caragana microphyl-la)。并依据各种群的拓殖 ,生物产量和根系分布等生物学特性分析了各种群在恢复演替中的作用。根据种群根系分布范围与种群密度变化的关联 ,本文提出“恢复演替的作用域扩展”概念。在过度放牧导致草原退化演替中 ,表现出群落地上部分矮化和地下部分的浅层化 ,恢复演替则表现其逆过程。当恢复演替开始后 ,浅层土壤中最先出现拥挤 ,浅根性植物种群趋于衰退 ,也促使一些种群向土壤深层发展。表现出种群更替的作用空间扩展的趋势。其中衰退种群植株死亡后的资源空间可使拓殖能力强的种群或原种群增长。于是资源与种群增长构成一个反馈调节环。反馈调节使群落演替自组织过程表现出方向性。在恢复演替过程中各种群的数量指标均表现出波动性     

荒漠草原地区不同载畜率对功能群特征及其多样性的影响

采用随机区组试验研究了内蒙古高原荒漠草原亚带短花针茅(Stipa breviflora)草原群落不同载畜率对草原功能群特征及其多样性的影响,结果表明:不同载畜率水平下,功能群组成结构没有改变,功能群内物种组成及其群落学特征随着载畜率的增加发生了相应的变化。灌木类和多年生禾草特性比较稳定,多年生杂类草随着载畜率的增加物种组成下降幅度较大,使得群落结构和组成随载畜率的增加趋于简单化。丰富度指数和多样性指数重牧区最低,均匀度变化有所不同,因为中度放牧提高草地群落的植物多样性,更主要地是通过改变群落物种均匀性来实现的。     

不同利用方式下贝加尔针茅草甸草原群落多样性变化

以内蒙古贝加尔针茅草甸草原围封、刈割和放牧样地为研究对象,分析2016~2018年内植物群落物种组成和多样性变化规律,为草原合理利用提供指导。结果表明:(1)贝加尔针茅草原共调查到76种物种,不同利用方式下植物组成不同。(2)相比较围栏和刈割利用,2018年放牧样地Margalef丰富度指数、Simpson优势度指数、Shanon-Wiener多样性指数和Pielou均匀性指数均显著降低(P<0.05)。(3)围封利用下Simpson优势度指数表现为降-升年度变化(P<0.05);放牧样地Margalef丰富度指数表现为降低年度变化(P<0.05)。综合分析表明,相比较围封和刈割利用,放牧对贝加尔针茅草甸草原健康发展构成威胁,围封和刈割利用下群落物种多样性较高。     

呼伦贝尔草甸草原羊草群落不同退化程度土壤理化指标

文中对放牧干扰下不同退化程度呼伦贝尔草甸草原羊草群落土壤理化性质进行了研究。结果发现,土壤含水量、土壤全氮、土壤有机物、土壤速效氮随着退化程度的增加显著下降,而土壤容重、土壤(1-2mm)粗粒百分含量、土壤速效钾随着退化程度的增加而显著提高。土壤速效磷和pH值没有规律性变化。通过研究表明:土壤含水量、土壤容重、土壤(1-2mm)粒径粗粒、土壤有机物、全氮、速效氮和速效钾在不同退化程度之间都具有显著性差异,因此,这些指标可做为草甸草原羊草群落确定土壤退化程度的退化指标。     

放牧与刈割对科尔沁草甸植被演替的影响

本文研究了放牧与刈割两种草地利用方式对科尔沁草甸植被演替的影响。结果表明:1)在自由放牧干扰下,优势度最大的前五个种为虎尾草(27.8)、蒲公英(3.52)、狼毒(3.42)、野韭菜(3.03)、鹅绒委陵菜(2.67);在秋季割草干扰下,优势度最大的前五个种为大油芒(9.57)、狗尾草(7.36)、野古草(6.36)、洽草(4.85)、芦苇(4.74)等五种禾本科植物;2)在自由放牧干扰下,一年生植物在群落中占据重要地位,其优势度为35.0,小于多年生植物的优势度55.9;在割草干扰下,多年生植物在群落中占据绝对优势,其优势度为82.9,大于一年生植物优势度10.6;3)在放牧扰动下,草地群落物种替代表现在不同植物生活型之间,主要是多年生草本为一年生草本和灌木所替代;表现在同一生活型不同物种之间,主要是多年生优质牧草为多年生劣质牧草或有毒有害杂草替代。     

Impacts of grazing and mowing on reproductive behaviors of Stipa grandis and Stipa krylovii in a semi-arid area

Disturbance can affect biomass allocation of plants,but can it influence plant reproductive behavior?To address this issue,we performed field plant community investigations and explored the reproductive behaviors of Stipa grandis and Stipa krylovii in response to grazing and mowing treatments at Maodeng pasture of Xilinguole League of Inner Mongolia,China during 2007–2009.The results showed that,with a similar niche width for the two plant species under mowing and grazing treatments,mowing significantly increased the ratio of ramet to genet number of S.krylovii and the carbon to nitrogen ratio of S.grandis,and grazing significantly decreased the ratio of vegetative to reproductive tiller biomass of S.grandis and increased the ratio of vegetative to reproductive tiller number of S.krylovii.Regression analysis showed that the significantly positive effect of root to shoot biomass ratio was stronger on the ratio of vegetative to reproductive tiller number of S.grandis than on that of S.krylovii.These results indicated that grazing and mowing influenced the reproductive manner and the process of sexual reproduction of S.grandis and S.krylovii.     

Impacts of livestock grazing on a savanna grassland in Kenya

The dynamics of most rangelands in Kenya remain to be poorly understood.This paper provides baseline information on the response of a semiarid rangeland under different livestock grazing regimes on land inhabited by the Massai people in the east side of Amboseli National Park in Kenya.The data were collected from grasslands designated into four types:(1) grassland from previous Massai settlements that had been abandoned for over twenty years;(2) grassland excluded from livestock grazing for eight years;(3) a dry season grazing area;and (4) a continuous grazing area where grazing occurred throughout all seasons.Collected data included grass species composition,grass height,inter-tuft distance,standing grass biomass and soil characteristics.The results indicated that continuous grazing area in semiarid rangelands exhibited loss of vegetation with negative,long-term effects on grass functional qualities and forage production,whereas grassland that used traditional Maasai grazing methods showed efficiency and desirable effects on the rangelands.The results also showed that abandoned homestead sites,though degraded,were important nutrient reservoirs.     

Effects of grassland management on the community structure,aboveground biomass and stability of a temperate steppe in Inner Mongolia,China

Plant community structure responds strongly to anthropogenic disturbances, which greatly influence community stability. The changes in community structure, aboveground biomass(AGB), biodiversity and community stability associated with different management practices were studied with a three-year field investigation in a temperate steppe of Inner Mongolia, China. The species richness, Shannon-Wiener index, evenness, plant functional type abundance, AGB, temporal community stability, summed covariance, scaling coefficient and dominant species stability were compared among areas subjected to long-term reservation(R), long-term grazing(G), mowing since enclosure in 2008(M) and grazing enclosure since 2008(E). Site R had higher perennial grass abundance and lower species richness than sites G, M and E, although the AGB was not significantly different among the four sites. The species structure varied from a single dominant species at site R to multiple dominant species at sites G, M and E. The long-term reservation grassland had lower biodiversity but higher stability, whereas the enclosed grassland with/without mowing had higher biodiversity but lower stability. Different stability mechanisms, such as the compensatory dynamics, mean-variance scaling and dominant species stability were examined. Results showed that community stability was most closely related to the relative stability of the dominant species, which supports the biomass ratio hypothesis proposed by Grime.     

蝗虫种群密度对牧草生长与损失量的影响

在贺兰山东麓天然草地,以黄胚小车ｅｄａｌｅｕｓ ｉｎｆｅｒｎａｌｉｓ Ｓａｕｓｓ为对象,进行了不同植物群落组成下不同蝗虫密度对牧草生长和损失影响的测定。田间笼养供试成虫,以实际取食日计取食时间,用目测法和收获法进行牧草生长量测定,用相关方差分析进行数据处理。结果表明;蝗虫取食对牧草生长的影响具有双重作用,在低密度时,有利于禾本科牧草的生长,随着种群密度的增多,对禾本科牧草的过量取食,会导致杂草增长     

黄土高原农牧交错带退耕坡地苜蓿-铁杆蒿群落养分分布特征

植物群落养分的空间分布反映了生态系统物质循环特征,可以为揭示生态系统资源的有效性及生态系统中植物群落的演替过程提供依据。本研究以黄土高原农牧交错带退耕坡地苜蓿-铁杆蒿群落为对象,分析其生物量和养分含量的空间分布特征。结果表明:退耕地苜蓿-铁杆蒿群落坡上部以苜蓿为主导物种,坡下部以铁杆蒿为主导物种,坡中部由二者共同主导。同一植物的生物量和N含量具有相似的空间结构,并且与植物种类有关;苜蓿和铁杆蒿P含量均以球状模型最佳,K含量的空间分布均以高斯模型最佳。苜蓿-铁杆蒿群落生物量和养分含量具有较强的空间依赖性,其空间变异主要由结构性因素决定。苜蓿和铁杆蒿生物量和养分含量的自相关性随距离变化表现出相似的趋势,但随生物量和养分种类的不同而异,且铁杆蒿生物量和养分含量的自相关性大于苜蓿。随着人工草地向天然草地的演替,群落生物量和养分含量的空间自相关性和空间依赖性逐渐增强。     

放牧模式对高山草地蝗虫群落生物多样性的影响及其作用机制

为明确不同放牧模式对高山草地蝗虫群落生物多样性的影响及其作用机制,本研究调查牛放牧、羊放牧、牛羊混合放牧和休牧4种模式下高山草地植物群落特征、蝗虫群落组成和数量,分析蝗虫群落生物多样性特征,利用冗余分析方法分析植物群落与蝗虫群落的相关性,采用结构方程模型分析放牧模式对蝗虫群落的影响路径。结果显示,与休牧相比,牛放牧、羊放牧、牛羊混合放牧模式显著影响高山草地植物群落高度、植物群落覆盖度和禾本科牧草高度,但对植物群落生物多样性影响不显著。4种放牧模式下共捕获蝗虫13种,不同放牧模式下,高山草地的生物指示种不同。与休牧模式相比,牛放牧、羊放牧、牛羊混合放牧模式显著影响高山草地Shannon-Wiener指数、Simpson优势度指数和Pielou均匀度指数;在牛放牧、羊放牧和牛羊混合放牧模式下,高山草地蝗虫群落Shannon-Wiener指数分别为0.36、0.35和0.29,高山草地蝗虫群落Simpson优势度指数分别为0.45、0.45和0.35,高山草地蝗虫群落Pielou均匀度指数分别为0.33、0.33和0.24。高山草地植物群落高度、覆盖度和禾本科牧草高度与红翅皱膝蝗Angaracris rhodopa、鼓翅皱膝蝗A.barabensis、青海痂蝗Bryodema miramae等呈负相关,与狭翅雏蝗Chorthippus dubius呈正相关。结构方程模型分析表明不同高山草地放牧模式主要通过改变植物群落高度间接影响蝗虫群落生物多样性。     

Termite effects on soils and plants are generally consistent along a gradient in livestock grazing

Livestock grazing is a major driver of ecosystem functions in drylands and would be expected to influence soil biota such as termites. We examined changes in soil chemistry and plant community composition on mounds constructed by the subterranean termite Anacanthotermes ahngerianus along a gradient in grazing intensity in an arid steppe in north-eastern Iran. The grazing gradient was represented by increasing distance from an area used by resting livestock, and plant and soil attributes measured within three adjacent microsites (termite mounds, non-mound controls, intervening annular zone surrounding the mounds). Values of soil EC; pH; exchangeable Ca, Mg, and Na; and total nitrogen and organic carbon were greatest in mound soils and declined from mounds to control microsites. Mounds were completely devoid of plants. Annular zones had three-times less cover than the control sites, but there were no differences in diversity or evenness. Electrical conductivity values were ten-times greater on mounds than controls close to resting sites, but the difference diminished rapidly with distance from resting sites. For all other soil and plant variables, differences between microsites were consistent across the grazing gradient. Increased grazing intensity was associated with increasing soil pH, EC and sand content, and reduced plant cover. Overall our study shows that the effects of termites on soil chemistry and plant cover varied little across the grazing gradient. Our results suggest that termite mounds may sustain their role as sites of enhanced soil nutrients under even high levels of grazing.