不同放牧率对冷蒿小禾草草原土壤微生物数量和生物量的影响

以围栏轮牧方式研究不同放牧率对退化草原土壤微生物的影响。结果表明，围栏及适度放牧四年后使土壤微生物的数量显著提高（P＜0．01），有利于退化草原的逐步恢复。与对照区比较，放牧区微生物各类群的数量均呈减少趋势，并与土壤有机碳变化密切相关（p＜0．01）。九年后，在4羊／ha区的微生物量-C高于对照区，而在1．33和6．67只羊／ha区则有所降低。长期中牧（4只羊／ha）对土壤微生物总数无显著影响。

中国美利奴育成羊夏季放牧采草量及维持代谢能需要量的测定

对有成公羊和有成母羊分别采用全收粪法及Cr2O3外源指示剂法测定排粪量，用食道瘘管羊采集牧草样本，用Tilley－Terry法测定牧草消化率。测得8～9月份嘎达苏地区平均体重30．3kg的育成羊放牧采草量平均790，3g／日·只，占体重的2．61％。测得同一时期育成公羊和育成母羊维持代谢能需要量分别为0．48MJ／W0．75和0．43MJ／W0．75。

放牧胁迫下冰草表型性状的变化

冰草对放牧胁迫的适应是多方面的,表型性状上不仅表现为营养枝数量增加,生殖枝数量、生殖枝高度、营养枝高度、结实率、株丛径、穗宽、穗长、穗节数、穗小花数降低,其中营养枝和生殖枝高度的降低具有显著性差异(p<0.05)。这种小型化变异虽然有保守性,但没有遗传性,解除放牧胁迫后经过一段时间,形态上就能恢复正常的水平。

关于鸭茅及羊茅草地草高动态与草地利用性关系的研究Ⅱ——放牧条件对牧草再生速度的影响

本试验选用荷斯坦青年母年 10头 ,按 5头分 2组 ,分别在鸭茅和羊茅草地进行了放牧试验。本试验以放牧压、放牧前草高 (伸直高度 )及放牧前草量等作为草地放牧前因素 ,认为对草地放牧后草高产生影响 ,并由此给牧草以后的再生速度可能带来的影响进行了探讨。试验表明 ,作为放牧条件的放牧压对鸭茅草地放牧后再生速度终年产生明显的影响 ,而且这一影响与放牧压的高低成反比。在羊茅草地 ,不同放牧压条件对再生速度没有产生明显的影响 ,但春季出现了随放牧压的增高而下降趋势。因此 ,建议在两种草地中进行放牧利用时 ,应根据两种牧草的生长特点及季节合理的放牧利用。

内蒙古典型草原土壤无机氮含量对交替利用方式的响应

2009年6~9月初,在内蒙古典型草原上研究了4个不同放牧强度（对照无牧、轻度放牧、中度放牧和重度放牧）与打草交替利用方式下土壤温度、含水量、无机N（铵态氮和硝态氮）含量的变化及其相关性。结果表明,土壤温度整体呈先增加后降低的趋势,土壤含水量与之相反;6月,NH＋4-N、NO-3-N和无机N含量均高于7月;7~9月,NH＋4-N含量逐渐降低,NO-3-N含量则逐月增加,无机N含量先增加后降低;NH＋4-N和无机N含量在7月和8月均为随放牧强度的增加而增加,9月均在中度放牧下达到峰值。NH＋4-N含量与温度间相关性不明显,与含水量呈负相关;NO-3-N含量与温度呈显著负相关（P〈0.05）,与含水量间呈极显著正相关（P〈0.01）;无机N含量与温度呈负相关,与含水量间呈正相关,且均在中度放牧下达到显著水平（P〈0.05）。综合比较分析,中度放牧与打草交替利用方式较有利于土壤N的转化及无机N含量的增加。

Changes of Amino Acid Content in Leaves of Agropyron cristatum Under Grazing Pressure

By measuring and comparing the contents of amino acids in Agropyron cristatum under grazing pressure, this study showed that the contents of total and each of the amino acids in A. cristatum changed little under grazing pressure. How- ever, the contents of free glycine （Gly） and proline （Pro） were very sensitive to grazing. Glycine content in grazing population was higher than that in non-grazing population at flowering stage; the content of free proline in non-grazing population was higher than that in grazing population at tillering, heading and especially flower- ing stage; the content of free proline under grazing pressure at maturity stage was higher than that of non-grazing population.

Mountain Pastures and Grasslands in the SW Tien Shan,Kyrgyzstan-Floristic Patterns,Environmental Gradients,Phytogeography,and Grazing Impact

Vast grasslands are found in the walnut-fruit forest region of southern Kyrgyzstan,Middle Asia.Located above the worldwide unique walnutfruit forests and used for grazing,they play a pivotal role in the mixed mountain agriculture of local farmers.Accordingly,these pastures are subject to an increasing utilization pressure reflecting the changing political and social conditions in the transformation process from a Soviet republic to an independent state.A first detailed analysis of mountain pasture vegetation in the Ferghana Range answers the following questions:What are the main plant community types among Kyrgyzstan's mountain pastures? What are the main environmental gradients that shape their species composition? Which phytogeographical distribution types are predominant? How does grazing affect community composition and species richness in these grasslands? Species composition was classified by cluster analysis;underlying environmental gradients were explored using DCA.A dataset of 395 relevés was used for classification,and a subset of 79 relevés was used in a DCA to analyze the correlation between vegetation,environment,and grazing impact.The investigated pastures were classified into four distinctive plant communities.The site factors altitude,heat load,inclination and grazing impact were found to be the major determinants of the vegetation pattern.A significant overlap between floristic composition and structural and spatial properties was shown.The majority of the species pool consisted of Middle Asian endemics and Eurosiberian species.However,disturbance-tolerant species played a significant role with respect to species composition and coverage of the herbaceous layer in vast areas of southern Kyrgyzstan's mountain pastures.In general,an intense grazing impact is clearly reflected by both species composition and structural variables of plant communities.The highly diverse and unique ecosystem is modified by an increasing utilization pressure.In order to maintain vital processes and functioning of this valuable ecosystem-in both economical and ecological terms-,it is indispensable to adopt appropriate pasture management strategies.

Research on the Soil Carbon Storage of Alpine Grassland under Different Land Uses in Qinghai-Tibet Plateau

In this article, we mainly analysis the soil carbon storage of the alpine grassland under different land uses in Qinghai-Tibet Plateau. The samples of this investigation include six experimental fields which are fenced mowing grassland, artificial grassland, winter and spring grazing meadowland, summer and autumn mild grazing land, summer and autumn moderate grazing pasture and summer and autumn severe grazing land and seven soil layers included 0 cm-5 cm, 5 cm-10 cm, 10 cm-20 cm, 20 cm-30 cm, 30 cm-50 cm, 50 cm-70 cm and 70 cm-100 cm. The results show that the soil carbon storage in different soil layers will gradually reduce and the difference was remarkable （P 〈 0.05）. What is more, the soil carbon storage of alpine grassland under different land uses has following sequence： winter and spring grazing grassland 〉 summer and autumn mild grazing land 〉 artificial grassland 〉 summer and autumn moderate grazing meadowland 〉 summer and autumn severe grazing pasture 〉 fenced mowing meadow, and the significant difference between them is remarkable （P 〈 0.05）.

Influence of Sulphur Fertilizer on Sulphur Cycling and Its Implications on Sulphur Fertilizer Requirement of Grazed Pasture in Warm Seasonal Rangeland of Nei Monggol Steppe of China

Sulphur (S) cycling and implications on S fertilizer requirement in sheep-grazed pastures receiving three levels of S fertilizer at rates of 0, 30 and 60 kg S/hm 2 in 1995 and 1996 were studied using a mass-balance approach which accounted both for S inputs to and outputs from the soil-plant-animal system. Results indicated that S fertilizer increased by 50% of herbage S uptake and 15% or more of S bio-cycling rate in grazing system. The total S recovery of 30 and 60 kg S/hm 2 treatments from 1995 to 1996 was 74.0% and 37.6% respectively. Mineralization of organic S may be an important source of S for pasture when other S sources are low, accounted for 70% of the total S inputs without S fertilizer. The grazing sheep has an important ecological function, the feature of S cycling in grazed pastures was that 90% of herbage S ingested by grazing sheep was returned to soils as excreta. The amount of S released by sheep excreta accounted about 30% of the total released S through S bio-recycling. Loss from soil S leaching beyond the major plant rooting zone was the main S output from grazing system. However, urinary and fecal S losses, including transfer and leaching losses, also affected S budgets of grazing system. It is therefore important to investigate the recycling rate of both urinary and fecal S under field conditions. Based on the mass-balance principle, at least 10 kg S/hm 2 per year may be necessary for sustainable development of grazing system.

Analysis of Characteristics of Grazed Artificial Pastures in the South of Guizhou

＂Ryegrass, orchard grass, Festuca arundinacea and Trifolium repens＂ were researched in Dushan County, Guizhou Province, in order explore grass characteristics by different grazing methods in seasons. The results show that grass community height in different groups was of little differences（P0.05）; the group of moderate grazing in spring, summer and autumn dominated in grass cover; grass density showed insignificant variations among different treatment groups（P0.05） and in the groups of heavy grazing in spring and autumn and moderate grazing in summer and of moderate grazing in spring, summer and autumn, grass community density was higher compared with the other groups（P0.05）; as for above-ground biomass, the group of moderate grazing in spring and autumn and heavy grazing in summer and of moderate grazing in spring, summer and autumn dominated.

Measuring Herbage Mass by Non-Destructive Methods： A Review

Accurate assessment of herbage mass （HM） in pasture is a key to budgeting forage in grazing systems worldwide. Different non-destructive techniques to measuring pasture yield are commented. The methods compared include visual estimations, manual and electronic pasture meters and remote sensing. All methods are associated with a moderate to high error, showing that some indirect methods of yield estimation are appropriate under most appropriate because many factors as climate variations, soil certain conditions. In general terms, no method was found as the characteristics, plant phenology, pasture management and species composition must be taken into account to make local calibrations from a general model. Best results were found modifying general methods under local calibrations and under local conditions. In order to give farmers the best method to manage adequately their own grazing systems, researchers must select the most suitable technique considering the scale of operation, the desired accuracy and the resources available.

Characteristics of Momentum and Heat Transfer over Semiarid Grasslands with Different Grazing Intensities in Inner Mongolia,China

The drag coefficient （Ca） and heat transfer coefficient （Ch） with the bulk transfer scheme are usually used to calculate the momentum and heat fluxes in meteorological models. The aerodynamic roughness length （z0m） and thermal roughness length （z0h） are two crucial parameters for bulk transfer equations. To improve the meteorological models, the seasonal and interannual variations of Z0m, Z0h, coefficient kB-1, Cd, and Ch were investigated based on eddy covariance data over different grazed semiarid grasslands of Inner Mongolia during the growing seasons （May to September） from 2005 to 2008. For an ungrazed Leymus chinensis grassland （ungrazed since 1979）, Z0m and z0h had significant seasonal and in- terannual variations. Zorn was affected by the amount and distribution of rainfall, kB 1 exhibited a relatively negative variation compared with z0h, which indicates that the seasonal variation of z0h cannot be described by kB 1. To parameterize Zorn and z0h, the linear regressions between ln（z0m）, ln（z0h）, and the leaf area index （LAI） were performed with R2=0.71 and 0.83. The monthly average kB-1 was found to decrease linearly with LAI. The four-year averaged values of Ca and Ch were 4.5 × 10^-3 and 3.9× 10^-3, respectively. The monthly average Cd only varied by 8% while the variation of Ch was 18%, which reflects the dif- ferent impacts of dead vegetation on momentum and heat transfer at this natural grassland. Moreover, with the removal of vegetation cover, grazing intensities reduced Z0m, Z0h, Cd, and Ch.

Unpalatable Weed Stellera chamaejasme L. Provides Biotic Refuge for Neighboring Species and Conserves Plant Diversity in Overgrazing Alpine Meadows on the Tibetan Plateau in China

Steller chamaejasme L. （S. chamaejasme for short） is one of the most noxious unpalatable weeds in China, which has been frequently reported its negative interaction （i.e. competition and allelopathy） with other herbaceous species in grasslands. This study compared species diversity, biomass and sexual reproduction of herbaceous plants in meadows with S. chamaejasme and in open meadows without S. ehamaejasme in overgrazing meadows on the Tibetan Plateau in China to determine whether positive facilitation exist between S. chamaejasme and other herbaceous species under livestock＇s overgrazing. The results showed that there are more herbaceous species in meadows with S. chamaejasme than those in open meadows （35s and30s, respectively）. Diversity index and above-ground biomass were also significantly higher in meadows with S. charnaejasme. There were 39% （11/28） of all species with sexual reproduction found in meadows with S. charnaejasme, which was 7 times more than those in open meadows. Our study showed that S. charnaejasme could provide biotic refuge for neighboring plants and preserve plant diversity from livestock＇s overgrazing in alpine meadows on the Tibetan Plateau. It also suggested that inter-specific facilitation between S. charnaejasme and other herbaceous species may play a key role in overgrazing alpine meadows.

Restoration Prospects for Heitutan Degraded Grassland in the Sanjiangyuan

In many ecosystems ungulates have coexisted with grasslands over long periods of time. However, high densities of grazing animals may change the floristic and structural characteristics of vegetation, reduce biodiversity, and increase soil erosion, potentially triggering abrupt and rapid changes in ecosystem condition. Alternate stable state theory provides a framework for understanding this type of dynamic. In the Sanjiangyuan atop the Qinghai-Tibetan plateau (QTP), grassland degradation has been accompanied by irruptions of native burrowing animals, which has accentuated the loss of ground cover. Severely degraded areas of alpine meadows are referred to as 'Heitutan'. Here, using the framework of alternate stable state theory, we describe the proximate and ultimate drivers of the formation of Heitutan on the QTP, and we assess prospects for recovery, in relation to the degree of biophysical alteration, of these alpine meadows. Effective rehabilitation measures must address the underlying causes of degradation rather than their symptoms. Heitutan degradation is not uni-causal. Rather it reflects different mechanisms operating at different spatio-temporal scales across this vast region. Underlying causes include overly aggressive exploitation of the grasslands (e.g. overgrazing), amplification of grazing and erosion damage by small mammals when outbreaks occur, and/or climate change. Given marked variability in environmental conditions and stressors, restorative efforts must vary across the region. Restoration efforts are likely toyield greatest success if moderately and severely degraded areas are targeted as the first priority in management programmes, before these areas are transformed into extreme Heitutan.

Impact of Simulated Grazing on the Recovery, Production and Modular Dynamic of the White Wormwood Artemisia herba-alba Asso.

One of the species candidates to rehabilitate arid rangelands of Morocco is Artemisia herba-alba Asso. （white Wormwood）. Unfortunately, overgrazing is by far the most important factor causing the reduction of cover and disappearance of this plant. In order to assess the effect of season and grazing on the recovery ofA. herba-alba Asso., plants of similar size were collected from Gourrama region and transplanted in the Experimental Station of Errachidia. These plants were submitted to different clipping heights （Cl = 8 cm, C2 = 15 cm, C3 = 25 cm） during two growing periods： autumn （stage of seed filling） and spring （before the starting of flowering）. Mean results show highly significant （P 〈 0.01） differences between the three treatments during the two periods. The increase of the plant volume clipped influences the performances of production and regrowth, the study has shown that the cutting level C 1 affect negatively the Artemisia performances, in fact 60% of plants cut at this height have died after the second clipping against 25% for C2 and 4.2% for C3. The parameters of growth and modular dynamic of branches are also affected by the cutting height C 1. The phytomass produced after the first cutting results in highly significant differences （P 〈 0.0 l） between the three cutting heights. Finally, the study demonstrated that for better regrowth, the taller height C3 is the most convenient for white Wormwood during the two periods, but the cutting height C2 can also be adopted for the autumn period.

White Mulberry （Morus alba） Foliage as a Feeding Supplement for Growing Calves

The aim of this study was to evaluate the feed consumption and weight gain in calves fed with a nutritional block made of white mulberry （Morus alba） for a 90-day-period, involving dry season months （March-May） in Tuxpan, Veracruz, Mexico. A total of 45 growing Zebu x Swiss calves with an average weight of 200 kg were assigned randomly in three groups of 15 animals, and the following treatments of nutritional block were offered to each group： grazing animals （To）, grazing animals plus nutritious block with white mulberry （T1）, and grazing animals plus nutritious block without white mulberry （T2）. A consumption of 0.545 kg/d from block in treatment T1 was observed, significantly improving calves growing and showing a weight gain of 0.933 kg/d. Use of white mulberry in nutritional blocks is a good alternative for growing calves, as a feeding strategy given the seasonality of pasture production in the tropics.

Rangeland degradation assessment in Kyrgyzstan:vegetation and soils as indicators of grazing pressure in Naryn Oblast

Rangelands occupy more than 80% of the agricultural land in Kyrgyzstan. At least 30% of Kyrgyz pasture areas are considered to be subject to vegetation and soil degradation. Since animal husbandry is the economic basis to sustain people＇s livelihoods, rangeland degradation presents a threat for the majority of the population. We present for the first time an ecological assessment of different pasture types in a remote area of the Naryn Oblast, using vegetation and softs as indicators of rangeland conditions. We analysed the current degree of utilization （grazing pressure）, the amount of biomass, soil samples, and vegetation data, using cluster analysis as well as ordination techniques. Winter pastures （kyshtoo） are characterized by higher pH values （average of 7.27） and lower organic matter contents （average of 12.83%） compared to summer pastures （dzailoo） with average pH values of 6.03 and average organic matter contents of 21.05%. Additionally, summer pastures show higher above- ground biomass, and higher species richness and diversity. Our results support the hypothesis that winter pastures, which are located near settlements, suffer from over-utilisation, while the more distant summer pastures are subjected to much lower grazing pressure,

Forest encroachment in Eastern European forest-steppes at a decadal time scale

In the Eurasian forest-steppe,with increasing aridity,the balance between naturally co-existing forest and grassland patches is expected to shift towards grassland dominance in the long run,although feedback mechanisms and changes in land-use may alter this process.In this study,we compared old and recent aerial photographs of Hungarian forest-steppes to find out whether and how the forest proportion and the number of forest patches change at the decadal time scale.The percentage area covered by forest significantly increased in all study sites.The observed forest encroachment may be a legacy from earlier land-use:due to ceased or reduced grazing pressure,forests are invading grasslands until the potential forest cover allowed by climate and soil is reached.The number of forest patches significantly increased at one site(Fülöpháza),while it decreased at two sites(Bugac and Orgovány)and showed no significant change at the fourth site(Tázlár).This indicates that forest encroachment can happen at least in two different ways:through the emergence of new forest patches in the grassland,and through the extension and coalescence of already existing forest patches.Though the present work revealed increasing tree cover at a decadal time scale,the dynamic process should be monitored in the future to see how the vegetation reacts to further aridification.This could help devise a conservation strategy,as the woody/non-woody balance has a profound influence on basic ecosystem properties.

Grazing effects on the relationship between plant functional diversity and soil carbon sequestration regulated by livestock species

Grazing exerts a profound influence on both the plant diversity and productivity of grasslands,while simultaneously exerting a significant impact on regulating grassland soil carbon sequestration.Moreover,besides altering the taxonomic diversity of plant communities,grazing can also affect their diversity of functional traits.However,we still poorly understand how grazing modifies the relationship between plant functional diversity(FD)and soil carbon sequestration in grassland ecosystems.Here,we conducted a grazing manipulation experiment to investigate the effects of different grazing regimes(no grazing,sheep grazing(SG)and cattle grazing(CG))on the relationships between plant FD and soil carbon sequestration in meadow and desert steppe.Our findings showed that different livestock species changed the relationships between plant FD and soil organic carbon(SOC)in the meadow steppe.SG decoupled the originally positive relationship between FD and SOC,whereas CG changed the relationship from positive to negative.In the desert steppe,both SG and CG strengthened the positive relationship between FD and SOC.Our study illuminates the considerable impact of livestock species on the intricate mechanisms of soil carbon sequestration,primarily mediated through the modulation of various measures of functional trait diversity.In ungrazed meadows and grazed deserts,maintaining high plant FD is conducive to soil carbon sequestration,whereas in grazed meadows and ungrazed deserts,this relationship may disappear or even reverse.By measuring the traits and controlling the grazing activities,we can accurately predict the carbon sequestration potential in grassland ecosystems.

Species Richness and Diversity of Alpine Grasslands on the Northern Tibetan Plateau:Effects of Grazing Exclusion and Growing Season Precipitation

Species richness and diversity indices （Shannon-Wiener index, Simpson dominance index and Pielou evenness index） in alpine grassland ecosystems （alpine meadow, alpine steppe and desert steppe） under grazing-excluded and freely grazed sites were investigated along the Northern Tibetan Plateau Alpine Grassland Transect during summer 2009 and 2010. We found that species richness and diversity have not been significantly altered by short-term grazing exclusion since 2006 at vegetation and regional scales. Species richness and diversity were mainly driven by growing season precipitation （GSP）, which accounted for over 87 % of the total variation observed, Species richness and diversity at grazing- excluded and freely grazed sites appear to respond to growing season precipitation in parallel. Species richness exponentially increased with GSP while diversity indices showed positively linear relationships with GSP. This indicates that GSP on the Northern Tibetan Plateau is crucial in regulating species richness and diversity and should be taken into account in future studies on alpine grassland conservation.