放牧强度对短花针茅荒漠草原甲虫群落分布格局的影响

放牧对脆弱的荒漠草原生态系统有着重要影响,且随放牧强度及持续时间不同而变化。鞘翅目昆虫是环境监测与生物多样性变化的指示生物。利用巴氏罐诱法对短花针茅荒漠草原不同放牧强度草地的甲虫群落组成和多样性进行调查,探究放牧对荒漠草原甲虫群落的影响。结果表明:(1)步甲科、金龟科为短花针茅荒漠草原甲虫群落优势类群,埋葬甲科、芫菁科、拟步甲科和花金龟科为常见类群。(2)放牧强度增加不利于维持更多的捕食性甲虫;对照和轻度放牧样地可维持更多的腐食性甲虫。(3)甲虫数量随放牧强度增加而递减;群落多样性以重度放牧草地最大,轻度放牧草地最小;群落优势度为对照、中度、重度显著高于轻度放牧草地。各甲虫类群在不同放牧强度草地出现时间、高峰期均不同。(4)对照、轻度、重度放牧样地的甲虫优势类群群落结构不同于其他生境,但均与中度放牧样地存在相似性。轻度、中度、重度放牧样地的甲虫稀有类群群落结构不同于其他生境,但均与对照样地存在相似性。(5)甲虫群落个体数与植物群落物种丰富度、盖度、植物平均高度、生物量呈显著正相关。Shannon-Wiener多样性指数、Margalef丰富度指数均与植物群落物种丰富度、生物量显著负相关。研究结果为荒漠草原甲虫多样性保护提供参考依据。     

放牧干扰下的蝗虫－植物相互作用关系

本文研究了内蒙古典型草原植物和蝗虫群落在不同放牧强度影响下的多样性、均匀性和丰盛度变化。比较了蝗虫群落与植物群落在放牧梯度上的相互作用关系。研究发现,放牧干扰活动会明显地影响植物和蝗虫群落结构,但蝗虫群落结构的变化趋势并非与植物完全同步。蝗虫与植物间的联系更多地表现在植物起着蝗虫栖息地条件的作用,而并不完全是食料植物的作用。文中对放牧实践与多样性保护的关系进行了讨论。     

放牧干扰下的蝗虫－植物相互作用关系

本文研究了内蒙古典型草原植物和蝗虫群落在不同放牧强度影响下的多样性、均匀性和丰盛度变化。比较了蝗虫群落与植物群落在放牧梯度上的相互作用关系。研究发现,放牧干扰活动会明显地影响植物和蝗虫群落结构,但蝗虫群落结构的变化趋势并非与植物完全同步。蝗早与植物间的联系列多地表现在植物起着蝗虫栖息地条件的作用,而并不完全是食料植物作用。文中对放牧实践与多样性保护的关系进行了讨论。     

不同放牧强度下的内蒙古草原蝗虫群落动态

本文研究了内蒙古草原蝗虫群落在不同放牧强度下的动态变化。植物和蝗虫的取样涉及3种植物群落类型。每一种群落类型又根据放牧强度的不同,划分为5个放牧梯度。随着放牧强度的增加,蝗虫群落的组成和结构均发生了明显的变化。使用贴近度分析及择近原则的方法,阐明了蝗虫种的优势度变化及替代种的替代次序。通过灰色关联及系统聚类分析方法的结合,分析了11个蝗虫种对不同放牧强度的反应。对应性分析和多元逐步回归分析说明,蝗虫群落的变化是与某些植被因子和土壤因子密切相关,特别是植物种类数、生物量、高度以及土壤硬度和含水量等。某些蝗虫种的生态指示意义也在文中进行了讨论。     

不同放牧强度对短花针茅草原植物种群种间关系的影响

为了解不同放牧强度对荒漠草原植物种群关联对的影响, 以不同放牧强度下短花针茅荒漠草原植物种群为研究对象, 在苏尼特右旗附近的荒漠草原试验示范基地, 设置 3 个放牧强度试验处理(SA1、 SA2、 CK), 于 2013 年 8 月对不同试验处理区种群存在状况和出现频率进行调查和统计, 旨在探讨不同放牧强度下短花针茅荒漠草原植物种群关联关系。结果表明, 3 个植物种群出现频率受放牧强度影响的敏感程度表现为碱韭<无芒隐子草<短花针茅。重度放牧导致显著正相关种对数减少, 物种关联链简单, 关联物种对较少。在研究的放牧强度范围内, 随着放牧强度的增加,植物群落总体关联性呈正联结的变化趋势。短花针茅和无芒隐子草主要表现为无关联性, 短花针茅与碱韭主要表现为负关联性, 无芒隐子草和碱韭受放牧强度影响, 其种间的竞争与亲和作用可以转化。     

内蒙古不同草地类型针茅属植物对放牧强度和气候因子的响应

以内蒙古草甸草原、典型草原、荒漠草原为研究对象,设置轻度、中度、重度以及对照4个放牧梯度,经过连续5年野外调查试验,研究针茅属植物在不同放牧强度及不同水热条件下的变化趋势,为针茅属植物为建群种的草地管理提供理论基础。结果表明:1)草甸草原的贝加尔针茅相对生物量随着放牧强度的增加呈下降趋势,即使降水波动较大,依然保持该趋势;2)典型草原大针茅受降水的影响较大,在对照样地中相对生物量与降水呈显著正相关(r=0.326),在轻度放牧样地中则为负相关(r=-0.319),在干旱年份大针茅相对生物量在轻度放牧强度中显著高于对照样地,所以放牧对大针茅的影响随降水的不同而不同;3)荒漠草原的短花针茅相对生物量随放牧强度增加而降低,但差异不显著,短花针茅受降水和温度的影响较大,与降水呈显著负相关(r=-0.440~-0.583),与温度呈显著正相关(r=0.282~0.299)。综上所述,在水分不受限制的草甸草原,即使降水温度有较大波动也不会对群落建群种产生较大影响,放牧成为草甸草原退化的主要因子;而在降水较少的典型草原和荒漠草原,气候逐渐成为除放牧以外的主要制约因子。     

荒漠草原蝗虫群落空间格局的研究

应用种－面积关系模型,计算出宁夏荒漠草原蝗虫群落最小调查面积;通过２×２联列表,用点相关系数和相关系数公式对蝗虫种间分布关系进行分析,用模糊聚类法将调查蝗虫划分为４个类群;以６项聚集指标和新提出的混合度指数,对９种蝗虫种群及群落分布型进行了分析,用主成分分析法进行了排序归类。最后依据种群数量、混合度指数、分布型相似性提出群落格局的“主导分布型”新概念,认为宁夏束颈蝗种群分布型为宁夏荒漠草原蝗虫群落空间格局的“主导分布型”     

不同尺度下荒漠草原建群种短花针茅的空间分布对载畜率的响应

为探讨不同尺度下短花针茅种群密度空间分布对载畜率的响应特点及差异,本研究以内蒙古四子王旗短花针茅荒漠草原建群物种短花针茅为对象,分析了不同尺度(1 m×1 m小尺度和5 m×10 m中尺度)下对照、轻度放牧、中度放牧和重度放牧4种处理短花针茅种群的空间异质性。结果表明: 与小尺度相比,中尺度的对照与轻度放牧下短花针茅种群密度显著降低。在2种尺度下,与对照相比,放牧使得短花针茅种群密度显著增加。通过半方差函数进行模型拟合, 小尺度下,对照、轻度放牧、中度放牧及重度放牧样地短花针茅种群分布分别符合线性、指数、指数和指数模型,中尺度下分别为高斯、指数、高斯和指数模型。不同尺度和放牧强度下短花针茅种群空间结构发生改变,小尺度下,对照样地短花针茅分布格局较简单、空间结构较好;而重度放牧样地短花针茅分布格局较复杂、空间结构较差;中尺度下,重度放牧样地短花针茅分布格局较简单、空间结构较好,而中度放牧样地短花针茅分布格局较复杂、空间结构较差。中、小尺度下,中度和重度放牧使得短花针茅种群空间异质性降低且分布更为均匀;此外,对照、中度和重度放牧下中、小尺度短花针茅种群空间分布趋势基本一致,而轻度放牧则有所不同。     

不同放牧强度下克氏针茅(Stipa krylovii)草原的根系特征

以呼伦贝尔克氏针茅草原不同放牧强度下的演替群落为对象,开展群落及其群落建群种的地下生物量和根系形态特征研究.结果表明:从轻度放牧到重度放牧,群落种类组成和根系功能群类型趋于简单化;群落地下生物量的空间分布形态呈“T”型;不同放牧强度下草原群落的建群种出现了明显替代现象,轻度放牧样地群落建群种为密丛型根系的克氏针茅,中度放牧为疏丛型根系的糙隐子草(Cleistogenes squarrosa,重度放牧为鳞茎型根系的碱韭(Allium polyrhizum);随着放牧强度的增大,群落建群种根冠比逐渐增加,分别为0.47、1.0、4.1,并且群落建群种根系数量、根系体积、根系生物量、比根长及根长密度等各指标均发生了明显变化.另外,3种放牧强度样地群落建群种根冠比、根长密度均与土壤速效氮含量呈现显著正相关(P＜0.05).     

草地群落放牧干扰梯度β多样性研究

放牧过程通过牲畜的啃食、践踏作用干扰草场环境,使草地群落的物种组成发生变化,植物种群的优势地位发生更替。结果表明,随放牧干扰强度加重,从盐湿化草甸到典型草原,群落植物种丰富度呈下降趋势。β多样性测度结果显示,盐湿化草甸和羊草杂类草草甸群落物种变化的中度干扰出现在轻牧→中牧阶段,并在整个放牧干扰进程中,表现较低的稳定性;草甸草原和典型草原群落出现在中牧→重牧阶段;而荒漠草原物种变化表现出高度的稳定性,从轻牧到过牧物种替代仅1～3种。各群落放牧干扰植物多样性的稳定性次序是:荒漠草原>典型草原≥草甸草原>盐湿化草甸.     

Yaks and sheep trigger different changes in the grasshopper assemblages of the Qilian Mountains via differentially altering plant assemblages

1. The Qilian Mountains represent one of the key livestock‐raising grasslands in China. The two main herbivore species raised in this area – yaks and sheep – are of critical economical value. Grasshoppers compete with these animals for available nutrients, creating multifaceted relationships between livestock, grasshoppers and plants. A clear understanding of such relationships is lacking and is urgently needed to guide conservation efforts. 2. This study aims to document the effects of yak and sheep grazing on grasshopper assemblages and to elucidate the underlying mechanisms of such effects. 3. It is shown here that yaks and sheep impact grasshopper assemblages differently. Grasshopper assemblages exhibited lower density, biodiversity, richness, and evenness of distribution in yak‐grazed pastures than in grazing‐free grasslands. Sheep‐grazed pastures exhibited a dramatically divergent picture, with elevated density, biodiversity and richness, and a slightly decreased evenness of distribution. Grasshoppers were generally larger in grazed pastures than in grazing‐free grasslands, especially in yak‐grazed plots. 4. The present study suggests that differences between yak and sheep pastures in plant assemblage structure and plant traits are probably the underlying forces driving the differences in grasshopper assemblage structure and grasshopper traits, respectively. 5. The study shows that the grasshopper habitat indicator species differ between yak and sheep pastures, raising the possibility that such indicators can be used to monitor grassland usage and degradation in the Qilian Mountains. 6. These results provide novel insights into the dynamic interactions of common domesticated herbivore species, grasshoppers and plants in Qilian Mountains, which augment current knowledge and may ultimately lead to better conservation practices.     

Can re-establishment of cattle grazing restore bryophyte diversity in abandoned mesic semi-natural grasslands?

Changes of agricultural practices have led to decline of semi-natural habitats sustained by traditional animal husbandry in many European regions. The abandonment of semi-natural pastures leads to increase of vascular plant biomass and subsequent decline of weak competitors such as bryophytes. Re-establishing traditional animal husbandry may potentially restore biodiversity but the success of such measures remains insufficiently known. In this study, we asked if re-establishing cattle grazing on previously abandoned grasslands will restore their bryophyte communities. The effect of cattle grazing on bryophyte communities of mesic semi-natural grasslands was studied in south-western Finland in a comparison of (i) continuously grazed pastures, (ii) previously abandoned pastures where grazing was re-established during 1990s, and (iii) abandoned pastures, where grazing had ceased during late 1960s to early 1980s. The average cover, species richness, species density and species diversity of bryophytes were significantly higher in the continuously grazed than in the abandoned grasslands. Ordination analyses revealed clear differences also in community structure between the management classes. Re-established grasslands were ecologically heterogeneous and situated in between the continuously grazed and abandoned grasslands in all characteristics, indicating variable effect of the restoration measure. Seventeen bryophyte species were recognized as significant indicators of the three grassland classes, four of which could be used as indicators of valuable grassland habitats. Although there was variation in the consequences of re-introduction of grazing, the results give evidence of positive effect of grazing on regaining bryophyte diversity of abandoned grasslands.     

Effects of fire and grazing on grasshopper sparrow nest survival

Patch-burn grazing is a management framework designed to promote heterogeneity in grasslands, creating more diverse grassland structure to accommodate the habitat requirements of many grassland species, particularly grassland birds. Published studies on the effects of patch-burn grazing on passerines have been conducted on relatively large (430–980 ha pastures), contiguous grasslands, and only 1 of these studies has investigated the reproductive success of grassland birds. We assessed the effects of the patch-burn grazing and a more traditional treatment on the nesting ecology of grasshopper sparrows (Ammodramus savannarum) in small (<37 ha pastures) grasslands located in southern Iowa from May to August of 2008 and 2009. The study pastures were grazed from May to September and prescribed burns were conducted in the spring. We investigated the effects of treatments on clutch size and modeled grasshopper sparrow nest survival as a function of multiple biological and ecological factors. We found no difference in clutch size between treatments; however, we did find a reduction in clutch size for nests that were parasitized by brown-headed cowbirds (Molothrus ater). Constant daily survival rates were greater in patch-burn grazed pastures than in grazed-and-burned pastures (patch-burn grazed rate and grazed-and-burned rate ). Competitive survival models included year, stage of nest, nest age, and cool-season grass (csg) abundance within 5 m of the nest. Overall, csg abundance had the greatest effect on survival and had a negative influence. Although survival rates were highest in patch-burn grazed pastures, multiple factors influenced grasshopper sparrow survival. Nest survival rates for both treatments were relatively low, and variables other than treatment were more instrumental in predicting grasshopper sparrow survival. We recommend decreasing overall vegetation cover if increasing nesting habitat for grasshopper sparrows is a management goal. In addition, we recommend further investigation of heterogeneity management in fragmented landscapes to better understand how it affects biodiversity in relatively small management units that typify grassland habitats in the Midwest. © 2011 The Wildlife Society.     

放牧对蝗虫栖境结构的改变及其对蝗虫栖境选择的影响

放牧是草原植被利用的主要形式,牲畜的牧食极易改变蝗虫生存的栖境结构,本研究表明：在重牧区蝗虫发生的密度最高,而轻牧区蝗虫发生的密度最低,这说明,不同的牧压强度所形成的栖境对蝗虫栖境选择的适合度不一致。     

DYNAMICS OF GRASSHOPPER COMMUNITIES UNDER DIFFERENT GRAZING INTENSITIES IN INNER MONGOLIAN STEPPES

Abstract Vegetation and grasshopper community variables were monitored on the natural steppes grazed by livestock in Inner Mongolia, China. The sites sampled belong to 3 vegetation types laid separately in 3 continuums from different grazing intensities. Each continuum consisted of 5 plots along grazing gradients. Within the plots, the species composition, population number and population calorific value of grasshoppers that was converted from their biomass varied sensitively with increase of grazing intensities. The methods of neartude and choosing rules of fuzzy mathematics were used to analyze successive populations of grasshoppers. By combining the gray relation with hierarchic cluster analysis, eleven grasshopper species were divided into 3 grazing guilds based on their responses to grazing. The results from detrended correspondence and the multivariate regression analysis proved that there were close successive relationships among the grasshopper species that varied with the changes of plant species, biomass, height and coverage. The importance of some grasshopper indicators to grassland change is discussed.     

Small-scale species richness and its spatial variation in an alpine meadow on the Qinghai-Tibet Plateau

We investigated how the high small-scale species richness of an alpine meadow on the Qinghai-Tibet Plateau, China, is maintained. This area is characterized by strong wind and severe cold during long winters. In winter, most livestock is grazed on dead leaves in small pastures near farmers’ residences, whereas in the short summer, livestock is grazed in mountainous areas far from farmers’ residences. The number of plant species and the aboveground biomass were surveyed for three adjacent pastures differing in grazing management: a late-winter grazing pasture grazed moderately from 1 February to 30 April, an early-winter grazing pasture grazed lightly from 20 September to late October, and a whole-year grazing pasture grazed intensively throughout the entire year. In each pasture, we harvested the aboveground biomass from 80 or 100 quadrats of 0.01 m² along a transect and classified the contents by species. We observed 15.5–19.7 species per 0.01 m², which is high richness per 0.01 m² on a worldwide scale. The species richness in the two winter grazing pastures was higher than that in the whole-year grazing pasture. The spatial variation in species richness and species composition in the two winter grazing pastures in which species richness was high was greater than that in the whole-year grazing pasture in which species richness was lower. Most of the leaves that are preserved on the winter grazing pastures during summer are blown away by strong winds during winter, and the remaining leaves are completely exhausted in winter by livestock grazing. A pasture with a high richess is accompanied by a high spatial variation in species richness and species composition. There is a high possibility that the characteristic of spatial variation is also caused by traditional grazing practices in this area.     

The vertical distribution of below-ground biomass in grassland communities in relation to grazing regime and habitat characteristics

Abstract. 40 sites, representing different pasture types in Northwest Spain, were sampled in respect of their floristic composition, distribution of above and below-ground biomass and environmental and physical variables. Five plant community types were identified by classification techniques of plant species composition. These communities were then characterized in terms of the percentage of ground covered by herbaceous and shrub vegetation, stones, rocks and gaps as well as their topographic location and characteristics of the shallow soil (pH, organic matter, nitrogen and calcium content). Bio-mass was assessed in terms of above-ground structures, surface crowns and three below-ground layers to a depth of 10 cm. Three types of grazing regime were distinguished: Concentrated Intense Grazing in early spring (CIG), Extended Intense Grazing throughout the spring (EIG), and Non-Intense Grazing (NIG). Grazing regime showed the highest association with plant community type and three broad categories were identified: xeric stressed pastures, which nevertheless received CIG, mesic pastures with EIG, and three kinds of NIG mesic pastures. The xeric communities had the highest proportion of aboveground biomass, as a consequence of their greater proportion of woody perennials. These xeric communities displayed a more gradual reduction in below-ground biomass with depth than mesic pastures, a likely consequence of the low water content in the upper soil layers. The mesic communities had a high concentration of below-ground biomass in the upper layers when they were intensely grazed. However, when grazing was low (i.e. NIG situations), these communities had greater variability in biomass profiles than any of the other pasture types. Possible causes of the patterns in biomass distribution of the intensely grazed pastures are discussed.