围栏禁牧对毛乌素沙地土壤理化特征的影响

过度放牧导致干旱半干旱区毛乌素沙地草地严重退化。通过禁牧措施排除放牧干扰,使草地自然恢复,作为一种低投入的措施在世界各国退化草地生态系统恢复中得到广泛采用。文中对毛乌素沙地三种不同管理类型(持续放牧、围栏5年和围栏16年)土壤理化性状进行了研究,研究结果显示:围栏禁牧5年对0～30cm土壤颗粒组成和容重没有显著影响;围栏禁牧16年0～10cm土壤容重显著小于持续放牧区,而极细沙、粉粒和粘粒含量显著高于持续放牧区;围栏5年显著增加了0～5cm土壤有机碳,而0～30cm的全氮均没有显著增加。围栏16年土壤有机碳较放牧区在0～5cm、5～10cm、10～30cm分别显著增加了231%、81%、55%;全氮含量的变化趋势与之相同。结果表明,围栏5年对土壤粘粉粒、全氮含量的恢复基本没有效果;围栏16年能显著增加表层土壤粘粉粒含量和有机碳、全氮,但土壤碳、氮水平还是在比较低的水平(有机碳:4.30g.kg-1;全氮:0.74g.kg-1),即长期禁牧可以逐渐改善土壤质地和提高土壤肥力。研究结果为半干旱退化沙质草地生态系统的恢复、重建及管理提供科学依据。     

Rangeland Monitoring and Fire: Wildfires and Prescribed Burning,Nutrient Cycling,and Plant Succession

Prescribed fires are used to manipulate and manage rangelands, but effective monitoring techniques are needed to ensure that management goals and objectives are being met. The application of an effective fire program on rangelands is not a simple task. Overgrazing by livestock since the early development of the livestock industry has altered the vegetative complex on most rangelands with an increase in woody plants. Because of its relatively low cost, prescribed fire, both cool and warm season, are sustainable practices if proper grazing management is part of the management scheme. Grazing management and prescribed fire have often been treated as separate issues by rangeland managers; however, development and application of an effective prescribed burning program requires an understanding of the relationship between fire and grazing. Ranchers need fuel (grass) to burn and they also need income from livestock, which requires forage (grass, a major part of forage). In the short-term, fire reduces carrying capacity for livestock but, in the long-term, fire increases grass production, resulting in increased carrying capacity. Therefore, some monitoring technique is needed that will allow the manager to budget grass for both fuel and forage. The Grazing Manager (TGM) is a software program that projects both forage production (expressed as animal unit days) and, animal demand (expressed as animal unit days) for each forage year. TGM has been successfully used on the Texas A&M University Research Station at Sonora as a tool to integrate prescribed fire and grazing management.     

Determinants and rates of land degradation: Application of stationary time-series model to data from a semi-arid environment in Kenya

The causes of land degradation in the African drylands have been shown to vary. Some researchers consider climate to be the major contributor to degradation, with anthropogenic factors playing a minor role. Others reverse the significance of these two factors. A third group attributes land degradation to climate and anthropogenic factors equally. This study was undertaken to establish the factors influencing land degradation in a semi-arid environment in southeastern Kenya and the rate of change in vegetation types for a period of 35 years(1973–2007). The reduction in grassland cover was used as an indicator of land degradation. Causes of land degradation were determined by a multiple regression analysis. A log-linear regression analysis was used to establish the rate of vegetation change. The multiple and log-linear regression analyses showed:(1) woody vegetation, livestock population and cultivated area to be the main contributors of reduction in grassland cover in the area, and (2) an increase in undesirable woody species, livestock population and cultivated area had a significant(P0.05) negative effect on grassland vegetation. Increased human population, low amounts of rainfall and drought showed no significant negative effect on grassland vegetation cover. In conclusion, human and livestock population growth and increased agricultural land have contributed to intensive crop cultivation and overgrazing in the semi-arid lands. This overuse of the semi-arid rangelands has worsened the deterioration of the natural grassland vegetation.     

宁南山区不同放牧强度对天然草地土壤水分的影响

本文对位于宁夏南部黄土高原半干旱区过渡放牧区、中度放牧区和持续禁牧三种条件下的天然草地 0 - 9.9m土壤深度的水分含量进行了测定。三者土壤水分含量的主要差别在 0 - 4m以上土层。 0 - 4m土层的土壤湿度 ,核心保护区显著 ( p =0 .0 2 2 838)高于中度放牧区 ,极显著 ( p <0 .0 0 1 )高于过渡放牧区 ,中度放牧区也显著高于过渡放牧区 (p =0 .0 2 80 2 3)。平均土壤湿度 ,核心保护区分别是中度和过渡放牧区的 1 .2 5和 1 .5 6倍 ,中度放牧区是过渡放牧区的 1 .2 5倍。 4- 9.9m土壤湿度 ,核心保护区、中度放牧区和过渡放牧区没有显著差异 ,平均土壤湿度分别为 1 2 .3%、1 2 .7%、1 2 .7%。     

1983-2003年浑善达克沙地中部沙丘植被在放牧条件下的比较

为了研究长期放牧条件下植被的变化,采用样方调查方法分析了1983-2003年浑善达克沙地中部的沙丘植被在放牧条件下的变化.期间,物种多样性、生物量和盖度在第1个10年缓慢下降,而第2个10年则加速下降,在沙丘阳坡形成了以适口性差的一年生草本植物为主的稀疏植被,阴坡以木本树木为主.且表现为木本植物的降低速度比草本植物慢....     

Grazing and heat stress protection of native grass by a sand-fixing shrub in the arid lands of northern China

Shrub species are used in restoration projects on dryland for their facilitation effects, which include environmental improvements and protection from herbivore feeding. Facilitation effects on forage grasses are potentially important in improving grazing capacity on rangelands. However, the morphology-dependent performance of benefactor plants in facilitating forage species growth and supplementation under moderate grazing intensity remains unclear. Here, our main purpose was to measure facilitation performance in terms of the survival of a native forage grass, Agropyron cristatum (L.) Gaertn. (Gramineae)., in accordance with the growth conditions of a sand-fixing benefactor shrub, Caragana microphylla Lam., in the Hulun Buir Grassland, northern China. Six study sites with patches of A. cristatum and C. microphylla were established at the foot of fixed sand dunes. At each site, five quadrats were set in places where C. microphylla coverage was 100% and A. cristatum grew among the shrubs (shrub quadrats), and another five were set where A. cristatum grew alone without C. microphylla (grass quadrats). We measured the morphological traits of C. microphylla and A. cristatum in all 60 quadrats, along with the soil water content and soil temperature. The data were compared between the shrub and grass quadrats by generalized linear mixed-effect models to assess the shrub's facilitation effects. We also used such models to elucidate the relationship between the average height of C. microphylla and the morphological traits of A. cristatum in the shrub quadrats. The maximum height, average grazed height, and the number of seed heads of A. cristatum were greater in the shrub quadrats than in the grass quadrats. The soil surface temperature was lower in the shrub quadrats. The maximum height and seed head number of A. cristatum were positively associated with the average height of C. microphylla. These results suggest that the grazing impact and heat stress were smaller in shrub quadrats than in grass quadrats, and that the degree of this protective effect depended on the shrub height. The shrub canopy seemed to reduce the increase in soil temperature and keep the grass vigorous. Livestock likely avoided grazing grasses in the C. microphylla patches because of the shrub's spiny leaves; only the upper parts of the grass stems (including the seed heads) protruding from the shrub canopy were grazed. The sand-fixing shrub thus moderates the grazing impact and soil temperature, and contributes to vegetation restoration and grazing system sustainability.     

围栏与不同放牧强度对东祁连山高寒草甸植被和土壤的影响

在东祁连山高寒草地,对围栏7年和不同放牧强度的草地进行了物种数、地上生物量、地下生物量、土壤理化性质等研究。结果表明,围栏7年的高寒草地鲜草产量为425.8 g·m-2,显著高于夏季中牧159.3 g·m-2和夏季重牧91.0 g·m-2,但与冬季轻牧、夏季轻牧差异不显著。围栏条件下的物种数为26.3种·16 m-2,显著低于其他放牧条件下的物种数,但显著高于夏季重牧条件下的物种数23.0种·16 m-2;轻度或重度放牧都会使物种数减少,夏季中牧下的物种数最高(33.5种·16 m-2)。在0~10 cm的表层土壤中,围栏7年的草地根系生物量显著高于其他放牧强度。随着放牧强度的增加,根系生物量在0~10 cm土壤中呈下降趋势,在30~40 cm土壤中则表现为升高趋势。围栏7年的土壤容重低于其他放牧强度下的土壤容重,但差异不显著;夏季重牧的土壤容重显著高于围栏7年和其他放牧强度的土壤容重。随着放牧强度的增加,0~10 cm土壤碱解氮增加,围栏7年草地最低。围栏封育可有效改善和恢复草地植被,但不能长时间禁牧不进行放牧利用。合理的放牧能够维护高寒草甸草地生态系统功能、促进物种丰富度和土壤营养的均衡。     

Conversion of communal grazing land into arable land and its impacts on soil properties and vegetation cover

With rapid population growth and absence of agricultural intensification, smallholders need more land to grow crops. This resulted in communal grazing land conversion to cultivated land. This study, therefore, aimed at exploring the magnitude of communal grazing land conversion and its influence on soil properties and vegetation cover change. Ecological time line approach was used to measure the magnitude of change. Plants and soil samples were taken from open grazing land, seasonal grazing land, 6 years old cultivated land, 16 years old cultivated land and 20 years old cultivated land. Moreover, 95 respondents were selected to assess their perception on the subject. Data were analyzed using statistical analysis system software. Results showed that grazing land declined by 41.88%, while cultivated land increased by 56.80% in the years between 1992 and 2012. Plant attributes showed significant (P?P?相似文献   

Breeding Improved Grasses for Semiarid Rangelands

Vast areas of semiarid rangelands in western USA are severely degraded and infested with troublesome weeds such as cheatgrass (Bromus tectorum) and medusahead rye (Taeniatherum asperum). Reseeding with appropriate plant materials that are adapted to the site and competitive enough to replace existing undesirable vegetation is often the most plausible way to reclaim such sites. Unfortunately, many of our native grasses are more difficult to establish and are not as competitive with these exotic weedy grasses as their introduced counterparts, including crested and Siberian wheatgrass (Agropyron cristatum, A. desertorum, and A. fragile). Most native grasses did not evolve under intense management or in association with species as competitive as cheatgrass. Genetically improved germplasms and cultivars of native and introduced (naturalized) grasses have been and are being developed by the Forage and Range Research Laboratory (FRRL) of the United States Department of Agriculture-Agricultural Research Service (USDA-ARS) in cooperation with the Utah Agricultural Experiment Station (UAES) and other agencies. These plant materials have demonstrated the potential for increasing the genetic diversity, protecting watersheds and soil resources, and improving the habitat and grazing potential for livestock and wildlife on semiarid rangelands. Research is also in progress at FRRL to develop germplasm and methodology whereby introduced grasses may be used in combination with natives, and in some instances assist in the establishment of native stands. The proper choice of plant materials must be based on objective criteria if we are to protect our lands and natural resources from further degradation.     

退化草原定量化放牧条件下土壤动物的比较研究

在以冷蒿（Artemisia frigda）、糙隐子草（Cleistogemes sprrosa）、冰草（Agropyron cristatum）、寸草苔（Carex duriusula）等为主的退化草原上,是置以4、8、12、16、20只内蒙古细毛羊和零只羊（对照区）指标定量化的牧压梯度系列（均为100×100m2面积的放牧围栏试验小区）的土壤动物比较研究表明：其中以8和12只羊小区的土壤动物群落结构复杂而稳定，8只羊小区的土壤动物数量高于12只羊小区；多样性指数、均匀度、丰富度两者均较高，丰富度前者大于后者，理论上，8只羊／公顷是较理想的牧压指标。4、16、20只羊小区的土壤动物种类和数量明显减少，多样性指数、均匀度均低、20只羊／公顷小区由于少数种类数量高至使多样性指数偏高；三者的丰富度均低，综合分析认定为不可取的牧压指标。植食和捕食性的土壤动物与牧压呈负关联，杂食和粪食性土壤动物则与收压呈正关联。土壤动物各类群中以鞘翅类（Coleoptera）随牧区梯度的改变而呈规律性变化，是较理想的监测草原退化的生物指标。     

Effect of spatial scale and topography on spatial heterogeneity of soil seed banks under grazing disturbance in a sandy grassland of Horqin Sand Land, Northern China

Soil seed banks play an important role in the distribution and composition of plant communities in semiarid grassland ecosystems.However,information on how spatial scale influences the spatial heterogeneity of soil seed banks in a grassland under grazing disturbance is still lacking.Based on field sampling and greenhouse germination,we measured the species composition and seed density of soil seed banks at different spatial scales (30 m×30 m,30 m×60 m and 30 m×90 m)along a topographical gradient in a sandy grassland in Horqin Sand Land, Northern China.By applying geostatistical methods,we examined how spatial scale and topography affected the spatial distribution of soil seed banks in the study area.Our results showed that the total number of species in soil seed banks,as well as the number of dominant annuals,increased with the increase of spatial scales.Seed density in soil seed banks decreased with the increase of spatial scales due to an increase in the slopes and relative heights of the sampling points.Geostatistical analysis showed that the relative structural variance(C/(C0+C))of seed density and species richness were over 65%for all spatial scales,indicating that these variables had an obvious spatial autocorrelation and the spatial structured variance accounted for the largest proportion of the total sample variance.Spatial autocorrelation of seed density in soil seed banks increased with the increase of measured scales,while that of species richness showed a reverse trend.These results suggest that the total number of species in soil seed banks is spatial scale dependent and lower topography may accommodate more seeds.Spatial distribution of seed density in soil seed banks is also scale dependent due to topographic variation.Grassland management,therefore,needs to consider local grazing disturbance regime,spatial scale and topography.     

Herbaceous vegetation response to controlled fire and postfire defoliation in a semiarid rangeland of Argentina

Semiarid rangelands of central Argentina are shaped by fire and grazing. The aim of this study was to quantify the effect of controlled fire on aboveground biomass production of (1) herbaceous species as a whole group and (2) herbaceous species subclassified as desirable or undesirable perennial grasses and as herbaceous forbs at the end of two growing seasons after an experimental fire in a semiarid rangeland of central Argentina. The effect of the length of the resting period after fire on aboveground biomass production of desirable perennial grass species was also assessed; treatments consisted in defoliations at the end of the first and second postfire growing seasons, at the beginning and at the end of the second postfire growing season and only at the end of the second postfire growing season. Total biomass production of the burned treatments was higher than that of the control treatment, the difference being attributed to an increase in desirable perennial grass species biomass. This in turn was negatively affected by defoliation at the end of the first postfire growing season, suggesting that the beneficial effect of fire on biomass production might have been overridden by the stress imposed by an early defoliation. Overall, the results of the present study suggest that grazing should be held back for at least a whole year after the fire to achieve the pursued aim of increasing forage production by the use of controlled fire.     

荒漠草原群落及主要植物种群特征对放牧制度的响应

本文研究了短花针茅荒漠草原划区轮牧和自由放牧两种放牧制度群落及主要植物种群特征变化,结果表明:经过3年的轮牧试验后,划区轮牧区群落及主要植物种群的高度、盖度、密度均较自由放牧区有不同程度的提高。划区轮牧区与自由放牧区相比,草地基况有明显好转,而自由放牧区一些退化植物、一年生植物、杂类草在草群中的高度、盖度、密度有所增加。划区轮牧区现存量高于自由放牧区。     

Leaf gas exchange and photosynthesis curves of Elymus nutans and Potentilla anserina under fencing and grazing conditions in the Qilian Mountains,Northwest China

Potentilla anserina L. and Elymus nutans Griseb. are dominant species in the subalpine meadows of China. Grazing is one of the most important factors that influence community structure and productivity of subalpine meadows. Understanding how grazing changes photosynthetic capability is essential for preservation and restoration of grasslands. However, information about the effects of grazing on photosynthetic capability remains inadequate. Experiments were conducted in fencing and grazing areas in the Qilian Mountains, Northwest China. The leaf gas exchange and photosynthetic curves of P. anserina and E. nutans were measured at different growth stages. Results showed that grazing decreased the values of leaf gas exchange parameters, such as net photosynthetic rate, stomatal conductance, transpiration rate, and intercellular CO_2 concentration of P. anserina and E. nutans. In addition, grazing decreased the values of net photosynthetic rate-photosynthetically active radiation(PN-PAR) curve parameters, such as light-saturated net photosynthetic rate, apparent quantum efficiency, light compensation point, light saturation point, and dark respiration rate. Our results demonstrated that grazing was the primary limiting factor for photosynthesis of dominant grassland species in the study area.     

Effects of fencing on vegetation and soil restoration in a degraded alkaline grassland in northeast China

In order to restore a degraded alkaline grassland, the local government implemented a large restoration project using fences in Changling county, Jilin province, China, in 2000. Grazing was excluded from the protected area, whereas the grazed area was continuously grazed at 8.5 dry sheep equivalent（DSE）/hm2. In the current research, soil and plant samples were taken from grazed and fenced areas to examine changes in vegetation and soil properties in 2005, 2006 and 2008. Results showed that vegetation characteristics and soil properties improved significantly in the fenced area compared with the grazed area. In the protected area the vegetation cover, height and above- and belowground biomass increased significantly. Soil pH, electrical conductivity and bulk density decreased significantly, but soil organic carbon and total nitrogen concentration increased greatly in the protected area. By comparing the vegetation and soil characteristics with pre-degraded grassland, we found that vegetation can recover 6 years after fencing, and soil pH can be restored 8 years after fencing. However, the restoration of soil organic carbon, total nitrogen and total phosphorus concentrations needed 16, 30 and 19 years, respectively. It is recommended that the stocking rate should be reduced to 1/3 of the current carrying capacity, or that a grazing regime of 1-year of grazing followed by a 2-year rest is adopted to sustain the current status of vegetation and soil resources. However, if N fertilizer is applied, the rest period could be shortened, depending on the rate of application.     

Farmers' knowledge and perceptions of the stunting disease of Napier grass in Western Kenya

Production of Napier grass, Pennisetum purpureum, the most important livestock fodder in Western Kenya, is severely constrained by Napier stunt (Ns) disease. Understanding farmers' knowledge, perceptions and practices is a prerequisite to establishing an effective disease management approach. Using a random sample of 150 farmers drawn from Bungoma, Busia and Teso districts of Western Kenya, this study sought to: (i) assess farmers' perceptions and knowledge of Ns disease, including its effects on the smallholder dairy industry; (ii) record farmers' current practices in managing Ns disease; and (iii) identify Ns disease management challenges and intervention opportunities in order to develop an efficient integrated disease management approach. The majority (86·7%) of the farmers were aware of Ns disease and observed that it was spreading rapidly in the region, which was perfectly predicted by farmers' access to agricultural information (marginal effect = 0·164), indicating a need for extension platforms for knowledge sharing among the industry stakeholders. The disease had affected Napier grass yields so most farmers could not feed their livestock on the amounts they produced, and they were buying Napier grass. Those who relied on income from selling Napier grass received less due to loss in productivity. Milk production had reduced by over 35%. The cause of the disease was unknown to the farmers, with no effective disease management strategy available to them. An integrated disease management approach needs to be developed to fit within the mixed farming systems, supported by simple decision aids.     

基于主成分分析的内蒙古草原刈割与放牧退化演替比较研究

基于多年的野外调查和控制实验数据,采用主成分分析的方法,对内蒙古羊草草原刈割退化演替系列,放牧退化演替系列,退化群落恢复演替系列进行比较研究,研究放牧和刈割影响下群落功能群组成的替变规律。结果表明:PCA排序很好地指示了放牧与刈割演替方向的变化,在功能群的替变上,共同点是根茎禾草减少,不同点是刈割导致小禾草增加,而放牧导致小禾草和小半灌木均增加。PCA排序验证了前人关于8月份刈割对羊草草原群落影响最大的结果。PCA排序显示放牧退化空间梯度系列与退化群落恢复演替时间梯度系列的逆过程一致,表明退化演替研究中时空替代的方法可行。     

论西北天然草地保护对策与技术

中国西北地区的广阔草原约为1．2亿hm^2，占我国北方天然草地总面积的50％，是我国畜牧业的主要基地之一。由于过分地注重牧畜头数的增加，草原退化日趋严重。保护西北的天然草地，实现其合理利用，基本对策为：1．稳定性畜头数，提高牲畜群体质量，以质定数；2．施行季节畜牧业，实现草畜平衡，逐步建立牧区繁殖－农区肥育的新体系；3．进一步加强草地建设的投资；4．封育改良相结合，实行大范围的轮封轮牧制度；5．解决实现上述对策的关键问题与技术。     

我国北方半干旱区草地水分供需状况研究

利用半干旱区181个站点40a的气象资料,依据伊万诺夫湿润系数对半干旱区草地进行气候分区,采用计算精度较高的FAO Penman-Monteith方法(1998)计算可能蒸散。在计算不同草地类型草地蒸散系数的基础上,计算半干旱区草地实际蒸散量,通过水分盈亏和水分订正系数等来分析评价不同草地类型的水分供需状况。结果表明:不同草地类型的蒸散系数也不同,草甸草原的蒸散系数最大,荒漠的蒸散系数最小;不同草地类型的实际需水量也不同:草甸草原>典型草原>荒漠化草原>草原化荒漠>荒漠;在半干旱地区实施退耕还草有利于水资源的可持续利用和生态环境的改善。     

放牧干扰对典型草原植被光谱及蝗虫密度的影响

为研究内蒙古典型草原不同放牧强度植被反射光谱与植被参数和蝗虫密度的关系,使用地物波谱仪于2015年和2016年对5个放牧梯度,共20hm~2样地进行调查研究。结果表明,不同放牧强度植被地上总生物量与归一化植被指数(NDVI)关系为y=0.034 8+0.002 9x(R~2=0.645 5,P=0.000 2),蝗虫密度与NDVI线性关系为y=0.067+0.013x(R~2=0.415,P=0.006)。对其进行冗余分析(RDA)发现,植被地上总生物量、植物高度、糙隐子草生物量是蝗虫数量和NDVI变化的主要影响因子,其中植被地上总生物量是显著性影响因子(P=0.001)。在不同放牧强度下蝗虫密度与草地NDVI显著相关(P0.05),随NDVI增大而增多。本文研究结果为进一步开展放牧区蝗灾遥感监测和科学合理地利用草地资源奠定了基础。