关于退牧还草的意义和技术标准问题探讨

退牧还草是一项长期而又复杂的系统工程,需要统筹考虑、科学规划、合理安排.但各地在实际操作中对究竟怎么退、如何退,缺乏规范和技术标准,这集中表现在没有明确什么样的草地需要禁牧、什么样的草地需要休牧、什么样的草地需要轮牧等问题上.禁牧、休牧和轮牧的工程标准和技术措施缺乏,给当前正在进行的退牧还草工作带来很多混乱和困难.因此,规范退牧还草的技术标准是当前退牧还草工作首先要解决的问题.     

Effects of Sagebrush Restoration and Conifer Encroachment on Small Mammal Diversity in Sagebrush Ecosystem

Conifer encroachment in sagebrush ecosystems reduces habitat heterogeneity, niche space, and resource availability, all of which negatively affect many wildlife populations. Sagebrush restoration is recommended as a management action to mitigate conifer encroachment and restore wildlife across millions of hectares in the Great Basin. Despite this recommendation, the effects of conifer encroachment and sagebrush restoration are unknown for most wildlife species. Small nonvolant mammal communities include keystone species, consumers and prey; facilitate energy flow and ecological function; and provide important ecological goods and services. We assessed causal relationships between conifer encroachment and sagebrush restoration (conifer removal and seeding native plants) on small mammal communities over 11 yr using a Before-After-Control–Impact design. Sagebrush habitat supported an additional small mammal species, twice the biomass, and nearly three times higher densities than conifer-encroached habitat. Sagebrush restoration increased shrub cover, decreased tree cover, and density but failed to increase native herbaceous plant density. Restoration caused a large increase in the non-native, invasive annual cheatgrass (Bromus tectorum L.). Counter to prediction, small mammal diversity did not increase in response to sagebrush restoration, but restoration maintained small mammal density in the face of ongoing conifer encroachment. Piñon mice (Peromyscus truei), woodland specialists with highest densities in conifer-encroached habitat, were negatively affected by sagebrush restoration. Increasing cheatgrass due to sagebrush restoration may not negatively impact small mammal diversity, provided cheatgrass density and cover do not progress to a monoculture and native vegetation is maintained. The consequences of conifer encroachment, a long-term, slow-acting impact, far outweigh the impacts of sagebrush restoration, a short-term, high-intensity impact, on small mammal diversity. Given the ecological importance of small mammals, maintenance of small mammal density is a desirable outcome for sagebrush restoration.     

Behavioral and Ecological Implications of Bunched,Rotational Cattle Grazing in East African Savanna Ecosystem

Rangelands and the wildlife and livestock they support are critical to human livelihoods, but rangeland ecosystems increasingly suffer from overgrazing and degradation. Planned grazing, a strategy that commonly involves time-controlled rotations of high-density (bunched) groups of cattle across a pasture, is marketed as a method to enhance rangeland health and lessen livestock impacts. However, the behavioral mechanisms underlying any potential rangeland improvements resulting from rotational, high-density planned grazing have rarely been examined. To investigate these mechanisms, we compared planned grazing with conventional continuous grazing management in a savanna ecosystem in Kenya. We surveyed cattle grazing behavior, measured changes in vegetation characteristics through surveys conducted before and after cattle grazing, and measured native ungulate abundance following grazing using camera traps. Stocking rates were held constant across treatments, resulting in a commensurate decline in total foliar hits per pin (a proxy for vegetative biomass) across treatments. Planned grazing management altered cattle behavior and reduced grazing selectivity by restricting movements, causing cattle to walk more slowly while grazing and to take more bites per step. Vegetation survey results supported this finding: cattle in the planned grazing treatment ate significantly more Pennisetum grasses (typically avoided because of their unpalatability), creating the opportunity for regrowth of more palatable species after seasonal rains. We also documented significantly higher zebra presence in planned grazing plots after cattle grazing, likely due to increased relative abundance of more palatable grass species. This investigation of grazing behavior, and specifically decreased grazing selectivity as a mechanism underpinning the benefits of planned grazing, shows that when conducted at appropriate stocking densities, planned grazing has the potential to help mitigate rangeland degradation and improve rangeland sustainability for both livestock and wildlife in pastoral African savanna ecosystems.     

Effects of Twice-Over Rotational Grazing on Songbird Nesting Success in Years With and Without Flooding

Rotational grazing is sometimes promoted for grassland bird conservation, but the benefits to wildlife have not been comprehensively documented. We examined effects of twice-over rotational grazing on nesting success of grassland songbirds in southwestern Manitoba, Canada in comparison to season-long grazing. We monitored nesting attempts and collected structural vegetation data in 2011 (during a 1/300 flood event), and 2012 (average water levels), for five species of obligate grassland bird species (n = 110) and one shrub-nesting species (n = 41). Nesting analyses were conducted using logistic exposure models. Nesting success was 2.4 to 4 times lower in twice-over grazed pastures compared with season-long grazed pastures, perhaps because of the increased cattle density during the short grazing periods of the twice-over system. Nests protected by shrubs from grazing activities of cattle did not show this pattern. The grazing system did not have an effect on vegetation structure. This suggests that twice-over rotational grazing does not benefit grassland songbirds in northern mixed-grass prairies, and that caution must be taken before implementing this grazing system in areas intended to promote biodiversity conservation.     

Cattle Grazing Distribution in Shortgrass Steppe: Influences of Topography and Saline Soils

The distribution of livestock across heterogeneous landscapes is often uneven, which has important implications for vegetation dynamics and how rangeland managers achieve desired outcomes from these landscapes. Here, we use data from widely available digital elevation models to classify a landscape in the shortgrass steppe with subtle topographic variation using two different approaches: topographic wetness index (TWI) and topographic position classes (TPCs) derived from topographic position indices. We used global positioning system collars to track the grazing locations of cattle within replicate pastures and fit generalized linear mixed models to their locations to quantify the influence of topography on grazing distribution. In addition, we examine the influence of the presence of saline vegetation communities on cattle use of lowlands. The resulting models indicate that TPC more effectively predicts grazing distribution than TWI and that the patterns are strongest in the second half of the growing season (August ? October). Model performance was improved with the inclusion of saline vegetation communities, although the magnitude of cattle grazing time in these communities was not consistent across multiple pastures. These models, in combination with local knowledge, can be used by managers to predict and manage livestock distribution even in landscapes with relatively subtle topographic variability.     

Influence of Experience on Browsing Sagebrush by Cattle and Its Impacts on Plant Community Structure

Mechanical and chemical methods used historically to rejuvenate sagebrush-steppe landscapes are cost prohibitive. A low-cost alternative is to fashion systems of management in which locally adapted animals use sagebrush as fall and winter forage to reduce feeding costs and to enhance the growth of grasses and forbs during spring and summer. We evaluated the practicality of fall browsing of sagebrush (Artemisia tridentata ssp. tridentata, ssp. wyomingensis) by cattle. To do so, we assessed 1) the foraging behavior and body weights of cattle with varying levels of experience browsing sagebrush, and 2) the ensuing responses of sagebrush, grasses, and forbs to cattle grazing. In spatially and temporally replicated trials from 2007 to 2009, cattle were challenged to eat sagebrush. Pregnant cows with calves (2007 and 2008), bred yearling heifers (2008), and first-calf heifer/calf pairs (2009), supplemented with protein and energy, learned to eat sagebrush as a significant portion of their diet (up to 63% of scans recorded during grazing). Experienced animals consistently ate more sagebrush and lost less weight, or gained more weight, than naive animals in 2008 and 2009 (P < 0.05). Cover, production, and percent composition of grasses and forbs maintained or dropped slightly from 2007 to 2008 but then rebounded sharply in 2009 to much greater levels than in 2007 or 2008 (P < 0.05). A corresponding reduction in shrub cover, production, and percent composition accompanied the increase in forbs and grasses (P < 0.05). Our research suggests grazing by cattle during fall and winter can be effective, biologically and economically, and can lead to habitat renovation and resilience by creating locally adapted systems of management in ways that landscape manipulations with chemical and mechanical treatments or prescribed fire cannot.     

海晏县沼泽草场牛羊放牧情况及同盘吸虫感染调查

为了解海晏县沼泽草场放牧牛羊及同盘吸虫感染等情况而进行了本调查,结果为：沼泽草场放牧户占到全县总放牧户数的9.27%,放牧牛羊分别占到全县牛羊总数的10.93%和12.65%。77.78%的沼泽草场放牧户牛羊感染同盘吸虫,而牛群和羊群同盘吸虫感染率分别达到了59.26%和48.15%;牛羊群体混合感染率40.74%;牛羊个体同盘吸虫感染率分别为14.83%和17.04%。结果还表明专业技术人员等对同盘吸虫病了解不足,区域间感染率差别较大,牛羊感染率有上升的趋势,证明现在使用的驱除药物对同盘吸虫虫卵阳性率降低很不理想,今后对本病的预防知识普及宣传及技术培训、驱除药物研制和筛选、湿地椎实螺的防治十分迫切。     

日粮结构对羊瘤胃原虫种群及吞噬速率的影响

本文以4只瘤胃瘘管山羊为试验动物,研究碳水化合物结构对山羊瘤胃发酵、原虫种群结构及吞噬速率的影响。设置精粗比为10∶90、30∶70、50∶50、70∶30的4种日粮(A、B、C、D组),其干物质中中性洗涤纤维(NDF)分别为54.87%、44.23%、33.72%、23.23%。采用4×4拉丁方设计,使用荧光标记细菌技术测定原虫吞噬细菌的速率。结果表明:日粮结构影响瘤胃发酵,以B组微生物活力较强、NDF降解率较高、pH也相对稳定;原虫吞噬速率与日粮NDF含量间呈三次方曲线关系(Y=-0.183065X2-0.003092X3+467.117113,R2=0.86795)。吞噬速率与细菌(原虫)密度呈负(正)相关关系,方程为Y=445.514-3.078X1+1.864X(2R2=0.839、Y为吞噬速率;X1和X2为细菌和原虫密度)。日粮结构显著影响原虫种群结构,内毛虫和等毛虫随NDF含量降低而增高,而双毛虫和头毛虫则相反。内毛虫与双毛虫和头毛虫的吞噬速率分别为361.9、606.3个/h和607.5个/h,种属间差异显著,但不同种属吞噬速率随日粮结构变化的趋势基本一致。综上所述,日粮结构可以引起瘤胃发酵状态的改变,从而影响原虫种群结构和吞噬速率。     

Grazing Preferences and Vegetation Feedbacks of the Fire-Grazing Interaction in the Northern Great Plains

The fire-grazing interaction is well studied in mesic grasslands worldwide, but research is limited in semiarid systems. We examined the principal drivers and feedbacks of the fire-grazing interaction on the strength of cattle grazing selection, herbaceous biomass, crude protein, and vegetation structure and composition in two pastures in the Northern Great Plains. Cattle showed significant preference, use, and grazing utilization in recently burned patches that declined as time since fire increased. Cattle selection was driven by significantly increased crude protein in recent burns. Grazing utilization of 70% in patches with < 1 yr after fire established low herbaceous biomass, but the extent to which it was maintained varied with precipitation. Herbaceous biomass increased to nonburned levels 2 yr after fire, and crude protein decreased to nonburned levels 120 d after fire. Species composition was influenced primarily by site and year, though bare ground and litter were influenced by the fire-grazing interaction. Our data indicate that mixed-grass prairies of the Northern Great Plains are resilient to the fire-grazing interaction and that rest from grazing following fire is likely ecologically unnecessary. The use of the fire-grazing interaction is an alternative management strategy suitable for the Northern Great Plains, effectively increasing heterogeneity of grassland habitat.     

不同放牧强度对高寒草甸植被群落结构和土壤理化性状的影响

放牧是青藏高原高寒草甸最基本的利用方式。高寒草甸生态系统能否可持续利用与放牧强度紧密相关。本研究通过在青藏高原东缘碌曲县设置三个放牧强度处理和一个对照,分析了植被群落结构和土壤理化性质对放牧强度的响应。结果表明,植被盖度、高度和地上生物量均随放牧强度增加而降低,物种丰富的在中度放牧下最高;适度放牧能显著增加莎草比例,杂草随放牧强度增加而增加;土壤含水量和有机质随放牧强度增加而降低,pH和全磷无显著性变化,土壤容重无规律性变化;全氮、全钾和速效钾随放牧强度增加呈先增加后降低的趋势;速效磷随放牧强度增加而增加。综合分析认为,适度放牧能显著改良植被群落结构和土壤理化性质,有利于高寒草甸的可持续利用。     

绵羊放牧方式及强度对围封恢复草场牧草细胞壁成分及营养价值的影响

选取内蒙古自治区典型草原区封育恢复中天然放牧草场,进行毛肉兼用细毛羊的暖季放牧试验.采用2×5完全随机试验设计,设定不同放牧方式（不放牧,连续放牧,四区、五区、六区轮牧）及2种放牧强度（1.0,1.4 hm2/un.sh）,运用酶分析方法分析比较了围封过程中放牧绵羊对封育草场牧草细胞壁成分月动态变化及营养价值的影响.结果表明,整个暖季放牧期内,不同放牧区牧草营养物质含量主要受到放牧方式的显著影响（P＜0.05）.具体表现为,不放牧处理牧草细胞壁有机物（OCW）含量始终显著低于各放牧处理,不同放牧处理间没有明显差异;划区轮牧处理牧草始终保持着较高的消化性部分且显著高于连续放牧处理;不放牧处理牧草始终保持着较高的Oa和较低的Ob,而连续放牧处理与其相反,各轮牧处理间没有显著差异;轮牧处理总可消化养分（TDN）和代谢能（ME）含量较高,尤其在牧草生长旺盛期（八月份）,六区轮牧放牧场牧草可利用营养物质含量最高,营养价值最高.     

藏北地区草地补播及放牧制度对草地覆盖影响的遥感监测研究

草地畜牧业作为藏北地区的重要经济产业,一直以来政府和科研人员致力于通过试验示范区探索和推广天然草场围封改良、补播改良、优质混播人工草地建植等措施来提高草场利用率和维持草地生态系统的可持续发展。基于GPS实地测量人工、天然草场以及自由放牧、暖季休牧和禁牧不同放牧制度的草场试验样地范围,以2006年7月及2008年年内时间序列的CBERS-02星数据作为遥感数据源,分别监测人工与天然的休牧草场、天然的自由放牧-暖季休牧-禁牧草场的植被长势。利用归一化植被指数(NDVI)和差值植被指数(DVI)的均值、标准差、极值及优势度反映不同草场植被长势、覆盖均匀度等情况。结果表明:人工补播的草场植被普遍长势、最佳长势及最劣长势均优于天然草场,但人工草场的覆盖均匀度不及天然草场;天然禁牧、天然暖季休牧、天然自由放牧草场长势依次递减;休牧在九月中旬放牧之前与禁牧草场的植被覆盖均匀度基本保持一致,两者的NDVI标准差远低于自由放牧草场,但休牧草场在放牧之后,植被均匀度遭到破坏,NDVI标准差介于禁牧与自由放牧草场之间。此外,该研究采用3S技术,从另一角度有效地实现了对草场覆被长势的动态、宏观监测。     

13种激素对暖季天然草场放牧羔羊生长发育调控的研究

试验选取4月龄、平均体重为(24.71±2.07)kg的哈萨克土种公羔羊20只,于2008年5月15日-9月23日进行自然放牧羔羊各月龄体重、采食量和激素含量变化测定。试验结果表明,4～8月龄羔羊月平均日增重依次为175 g±34 g、92g±36 g、158 g±46 g和81 g±36 g,羔羊增重在4～5和6～7月龄出现2个高峰期,平均日增重高于5～6和7～8月龄。放牧羔羊干物质采食量逐月增高,4～8月龄依次为0.65 kg±0.21 kg、1.45 kg±0.32 kg、1.74 kg±0.48 kg、1.95 kg±0.50 kg和2.30 kg±0.45 kg,且各月龄间差异极显著(P0.01)。全期血清激素NPY含量5月龄最高(39.10 pg/mL±2.60pg/mL),7月龄最低(36.87 pg/mL±1.10 pg/mL);血清CCK、PP、SS、CORT含量,各月龄间差异不显著(P0.05),最高值分别为4月龄(45.19 pg/mL±9.70 pg/mL)、8月龄(108.53 pg/mL±19 pg/mL)、6月龄(160.34 pg/mL±10 pg/mL)、4月龄(22.1 ng/mL±4 ng/mL);GAS、T3、T4含量,4～8月龄逐渐升高;全期血清T4含量5月龄最高(78.30 ng/mL±12.7 ng/mL)、7月龄最低(65.83 ng/mL±13 ng/mL);MTL、SEC、GH、INS、T3变化规律相同,4～5和6～7月龄升高、5～6和7～8月龄降低。     

食道瘘管法在放牧家畜采食习性研究中的运用

本文介绍了目前广泛运用于草地放牧研究中的食道瘘管法的发展、食道瘘管手术及护理、食道瘘管样的制取、食道瘘管样品用于放牧家畜采食的营养成分、植物成分、采食量和消化率方面的测定，以及与其它常用的方法——放牧前后样方测定法、扣笼与未扣笼双样方法和模拟家畜采食采摘法对放牧家畜采食的营养成分、植物成分、采食量和消化率测定的比较，认为代表放牧家畜真实采食日粮的食道疹管样在以上各项指标的测定中都优于其它测定方法所得到的样品，更能代表放牧家畜的实际采食习性。     

Self-Regulation of Supplemental Feed Intake by Grazing Dairy Cows and its Effect on Animal Performance

Abstract

Grazing Norwegian Red dairy cows were offered one of two roughage supplements ‘baled silage (S) or ryegrass (R)’ on an ad libitum basis for a limited period daily. A third group received concentrate (C). Milk and FCM yields were significantly (P<0.05) influenced by treatment (23.65 and 22.81, 23.20 and 22.05 and 22.58 and 22.73 kg d^?1, for S, C and R, respectively). Milk composition was unaltered. The cattle offered ryegrass consumed significantly (P<0.05) more supplementary feed and less pasture, and spent less time grazing and more time ruminating than the other two groups. Cattle with high initial yields, despite higher intakes of both pasture and supplement, had reduced liveweight gains and a faster decline in milk production in comparison with low yielders.     

浅谈奉节县退耕还草发展围栏轮牧的思路

在调查和分析退耕还林还草问题的基础上,结合奉节县自然地理情况,提出了在奉节县退耕还草使用生物围栏发展围栏轮牧的思路。这是加快生态建设,发展经济,促进林牧互相结合共同发展,使生态效益、经济效益与社会效益相协调的重要措施。     

自由牧马对草甸草地群落结构及牧草品质的影响:以新疆昭苏夏马场为例研究

为探明自由牧马对草甸草地群落结构及牧草品质的影响,在新疆昭苏夏马场设置放牧试验,采用控制笼进行对照,分析了2013-2015年草地群落结构及牧草营养品质的动态变化。结果表明:(1)无芒雀麦(Bromus inermis)、羊茅(Festuca ovina)等一些马喜食的禾本科牧草的相对密度降低,狼毒(Euphorbia fischeriana)、龙胆(Gentiana scabra)等一些毒性植物和马不食植物的相对密度升高,但主要优势植物变化不大;(2)在3年夏场放牧中,草甸草地多样性指数(Simpson指数)维持在0.74～0.81;不同植物种类重要值变化趋势不同,白三叶(Trifolium repens)、草地早熟禾(Poa pratensis)和龙胆在群落中重要值增加,而细果苔草(Carex stenocarpa)和羊茅的重要值显著降低;(3)牧草中的中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)总体呈现上升趋势;粗蛋白(CP)含量随着放牧年限的增加从13.4%下降到11.3%,仍可达到马对粗蛋白含量(8%)的基本要求。由试验可知:目前的放牧强度(5匹马·ha-1)基本维持了草地的可持续性,但一定程度上降低了牧草的品质。     

青藏东缘高寒草甸植物群落结构及功能群特征对长期季节放牧的响应

为阐明高寒草甸植物群落对长期季节放牧的响应机制,本试验选取有10年以上冷、暖季放牧历史的湿生、中生、旱生高寒草甸进行探究。结果显示暖季放牧(6月至10月)下,湿生草甸香农指数与物种丰富度均显著小于冷季放牧(11月至翌年5月)(P<0.05),而旱生草甸多样性指数显著大于冷季放牧(P<0.05);冷季放牧地上生物量显著高于暖季放牧(P<0.05),其中暖季放牧下莎草科地上生物量所占比例最高。湿生草甸暖季牧场与旱生草甸冷季牧场莎草科重要值最高,其余牧场均为双子叶杂草重要值最高(P<0.05);经ANOSIM检验,季节性放牧下群落结构均有显著差异(P<0.01),湿生、旱生草甸群落结构差异较大,而中生草甸群落结构差异较小。本研究表明长期季节性放牧会影响植物群落结构特征,研究可为不同生境草甸的放牧制度和可持续发展提供理论基础。     

Vegetation,Hydrologic, and Erosion Responses of Sagebrush Steppe 9 Yr Following Mechanical Tree Removal

Land managers across the western United States are faced with selecting and applying tree-removal treatments on pinyon (Pinus spp.) and juniper (Juniperus spp.) woodland-encroached sagebrush (Artemisia spp.) rangelands, but current understanding of long-term vegetation and hydrological responses of sagebrush sites to tree removal is inadequate for guiding management. This study applied a suite of vegetation and soil measures (0.5 ? 990 m²), small-plot rainfall simulations (0.5 m²), and overland flow experiments (9 m²) to quantify the effects of mechanical tree removal (tree cutting and mastication) on vegetation, runoff, and erosion at two mid- to late-succession woodland-encroached sagebrush sites in the Great Basin, United States, 9 yr after treatment. Low amounts of hillslope-scale shrub (3 ? 15%) and grass (7 ? 12%) canopy cover and extensive intercanopy (area between tree canopies) bare ground (69 ? 88% bare, 75% of area) in untreated areas at both sites facilitated high levels of runoff and sediment from high-intensity (102 mm ? h^? 1, 45 min) rainfall simulations in interspaces (~ 45 mm runoff, 59 ? 381 g ? m^? 2 sediment) between trees and shrubs and from concentrated overland flow experiments (15, 30, and 45 L ? min^? 1, 8 min each) in the intercanopy (371 ? 501 L runoff, 2 342 ? 3 015 g sediment). Tree cutting increased hillslope-scale density of sagebrush by 5% and perennial grass cover by twofold at one site while tree cutting and mastication increased hillslope-scale sagebrush density by 36% and 16%, respectively, and perennial grass cover by threefold at a second more-degraded (initially more sparsely vegetated) site over nine growing seasons. Cover of cheatgrass (Bromus tectorum L.) was < 1% at the sites pretreatment and 1 ? 7% 9 yr after treatment. Bare ground remained high across both sites 9 yr after tree removal and was reduced by treatments solely at the more degraded site. Increases in hillslope-scale vegetation following tree removal had limited impact on runoff and erosion for rainfall simulations and concentrated flow experiments at both sites due to persistent high bare ground. The one exception was reduced runoff and erosion within the cut treatments for intercanopy plots with cut-downed-trees. The cut-downed-trees provided ample litter cover and tree debris at the ground surface to reduce the amount and erosive energy of concentrated overland flow. Trends in hillslope-scale vegetation responses to tree removal in this study demonstrate the effectiveness of mechanical treatments to reestablish sagebrush steppe vegetation without increasing cheatgrass for mid- to late-succession woodland-encroached sites along the warm-dry to cool-moist soil temperature ? moisture threshold in the Great Basin. Our results indicate improved hydrologic function through sagebrush steppe vegetation recruitment after mechanical tree removal on mid- to late-succession woodlands can require more than 9 yr. We anticipate intercanopy runoff and erosion rates will decrease over time at both sites as shrub and grass cover continue to increase, but follow-up tree removal will be needed to prevent pinyon and juniper recolonization. The low intercanopy runoff and erosion measured underneath isolated cut-downed-trees in this study clearly demonstrate that tree debris following mechanical treatments can effectively limit microsite-scale runoff and erosion over time where tree debris settles in good contact with the soil surface.