Reasonable grazing may balance the conflict between grassland utilization and soil conservation in the semi-arid hilly areas, China

Soil erosion caused by unsustainable grazing is a major driver of grassland ecosystem degradation in many semi-arid hilly areas in China.Thus,grazing exclusion is considered as an effective method for solving this issue in such areas.However,some ecological and economic problems,such as slow grassland rejuvenation and limited economic conditions,have become obstacles for the sustainable utilization of grassland ecosystem.Accordingly,we hypothesized that the conflict between grassland use and soil conservation may be balanced by a reasonable grazing intensity.In this study,a two-year grazing fence experiment with five grazing intensity gradients was conducted in a typical grassland of the Loess Plateau in China to evaluate the responses of vegetation characteristics and soil and water losses to grazing intensity.The five grazing intensity gradients were 2.2,3.0,4.2,6.7,and 16.7 goats/hm2,which were represented by G1-G5,respectively,and no grazing was used as control.The results showed that a reasonable grazing intensity was conducive to the sustainable utilization of grassland resources.Vegetation biomass under G1-G4 grazing intensity significantly increased by 51.9%,42.1%,36.9%,and 36.7%,respectively,compared with control.In addition,vegetation coverage increased by 19.6%under G1 grazing intensity.Species diversity showed a single peak trend with increasing grazing intensity.The Shannon-Wiener diversity index under G1-G4 grazing intensities significantly increased by 22.8%,22.5%,13.3%,and 8.3%,respectively,compared with control.Furthermore,grazing increased the risk of soil erosion.Compared with control,runoff yields under G1-G5 grazing intensities increased by 1.4,2.6,2.8,4.3,and 3.9 times,respectively,and sediment yields under G1-G5 grazing intensities were 3.0,13.0,20.8,34.3,and 37.7 times greater,respectively,than those under control.This result was mainly attributed to a visible decrease in litter biomass after grazing,which decreased by 50.5%,72.6%,79.0%,80.0%,and 76.9%,respectively,under G1-G5 grazing intensities.By weighing the grassland productivity and soil conservation function,we found that both two aims were achieved at a low grazing intensity of less than 3.5 goats/hm2.Therefore,it is recommended that grassland should be moderately utilized with grazing intensity below 3.5 goats/hm2 in semi-arid hilly areas to achieve the dual goals of ecological and economic benefits.The results provide a scientific basis for grassland utilization and health management in semi-arid hilly areas from the perspective of determining reasonable grazing intensity to maintain both grassland production and soil conservation functions.

Structural effects of reedbed grazing and its cessation on reed-nesting songbird densities

Reedbeds are crucial breeding habitats for vulnerable songbird species.Irrespective of their protection status,these habitats may be threatened by organic matter accumulation,progressively leading to structural homoge-nization and habitat succession towards woodland.Managers prevent excessive litter build-up with various in-terventions opening-up the reedbeds,such as grazing,which may be detrimental or suitable for some reed bird species.We assessed the effects of extensive grazing by horses and its cessation in the medium and long terms on reedbed structure,and the consequences on reed-nesting songbird densities in Estagnol Nature Reserve,a pro-tected wetland near the French Mediterranean coast.We compared reedbed structural features between grazed,newly ungrazed and old-ungrazed plots.During nine years,we censused four songbird species in spring and collected water level data in the same survey plots.Grazing reduced reedbed extent,rejuvenated the vegetation with more short green stems on a thinner litter,and produced higher structural heterogeneity and discontinuity compared to long-lasting non grazing.Newly ungrazed plot showed intermediate effects.All surveyed songbird total densities were similar among plots while species numbers and densities differed.Grazed reedbed was more attractive to Moustached Warblers(Acrocephalus melanopogon)and Great Reed Warblers(Acrocephalus arundi-naceus),likely due to the large edges and the high vegetation structural heterogeneity.However,Moustached Warblers were more negatively affected by higher water level in grazed reedbed,presumably because flooding prevents litter foraging.The newly ungrazed reedbed was not preferred by any species.All warbler species were found under low density in the old-ungrazed reedbed,where Reed Buntings(Emberiza schoeniclus)were exclu-sively found.Food availability related to thick litter layer may explain this predilection.Common Reed Warblers(Acrocephalus scirpaceus)were found everywhere in similar densities.We conclude that reedbed management by extensive horse grazing and also its long-term cessation may benefit several songbird species.Within a context of wetland degradation and disappearance,both management strategies are useful to establish and maintain suitable habitats for reed-nesting songbird communities.

Grasslands Response to Livestock Grazing Intensity in the Austral Pampas(Argentina):Testing the Intermediate Disturbance Hypothesis

Livestock grazing has a significant impact on natural grasslands,with approximately one-third of the world’s land area dedicated to this industry.Around 20%of global grasslands are highly degraded due to overgrazing,affecting their productivity and conservation capacity.Best practices are required to ensure sustainable livestock production that supports biodiversity.The Intermediate Disturbance Hypothesis(IDH)suggests that environments with moderate levels of disturbance exhibit a higher species diversity.Moderate grazing can reduce the dominance of certain species,thereby enhancing plant diversity.However,concerns arise regarding the increase of exotic and unpalatable species under moderate grazing levels,complicating grassland conservation efforts.The impact of livestock grazing on the functional structure of grasslands depends on factors such as grazing intensity,livestock species,and environmental conditions.Variations in grazing intensity may increase specific and functional diversity under moderate grazing,potentially masking the presence of invasive exotic species.In the Austral Pampas(Pampean phytogeographic province,Buenos Aires,Argentina),grasslands face various pressures from domestic livestock grazing that endanger their integrity if not properly managed.Therefore,our study aims to investigate potential differences in species richness and diversity,functional diversity,exotic plant abundance,and the number and distribution of plant functional groups across varying grazing intensities.The IDH is utilized as a tool to regulate livestock pressure for grassland conservation.Species and functional diversity indices were used to assess the impact of grazing on grassland diversity.Moderate grazing increased species and functional diversity,while intensively grazed or ungrazed areas showed reduced diversity.Livestock presence influenced the balance between native and exotic plants,with ungrazed areas having higher native plant abundance and grazed areas exhibiting higher exotic plant abundance.Grazing also influenced the composition of functional groups,with grazing-avoiding species being more prevalent in heavily grazed areas.Principal Component Analysis revealed a clear association between vegetation composition and livestock grazing intensity.These findings offer valuable insights into effectively managing grazing intensity for biodiversity conservation purposes.

Assessing the Environmental Impact of Extensive Beef Production in Grazing Lands of Argentina

Because of environmental constraints,beef cattle was for more than a century the only viable farming option in the extensive semiarid and subhumid lands of Argentina and the main source of nutrients for humans as well.However,a growing concern and criticism have risen today about its possible negative impact on the climate and the environment.These worries tend to affect current public opinions,national policies,and international trade.Based on 40 beef cattle farms scattered across different semiarid and subhumid regions of Argentina,here we evaluated the impact of extensive cattle production on carbon,water,and nutrient pollution.Life-Cycle Assessment(LCA)and Land-Based Assessment(LBA)were the two approaches we used here to compare the environmental impact of beef production.While the environmental footprint(EF)resulting from LCA expresses the impact per unit of food,the environmental balance(EB),derived from LBA,aims at quantifying the impact per unit of land.As such,the EB considers both negative and positive impacts on the farm as an integrated system.Following standardized procedures,we evaluated EF and EB up to the farm gate,leaving aside delocalized post-farm impacts such as those of processing,packaging,and transportation that occur beyond the farm gate.In agreement with previous evidence,our results show that the EF tends to decrease as per-head production increases.Correlation coefficients and statistical significance were the following for carbon(R=−0.574;p<0.01),water(R=−0.561;p<0.01),and N(R=−0.704;p<0.01)and Phosphorus(P)pollution(R=−0.802;p<0.01)footprints.On the contrary,the EB seems to be highly sensitive,and as per-hectare beef production increases.Correlations were the following for carbon emissions(CE:R=0.955;p<0.01),water consumption(WC:R=0.822;p<0.01),nitrogen excretion(NE:R=0.948;p<0.01)and phosphorus excretion(PE:R=0.945;p<0.01).What our results suggest is that the notion of EF is useful to evaluate the environmental impact in intensive beef production systems,and the EB is suitable to assess the impact of the extensive ones.In practice,both approaches provide different perspectives on the environmental-impact problem and they should be complementary used.We concluded that the methodological rigidity of EF does not allow proper discrimination among farms in the extensive systems.On the contrary,the EB approach tended to be highly sensitive to detecting differences between individual farms and farmers,thus allowing the identification of successful options for extensive beef production in terms of public image,policy-making,and commercial opportunities.

Feeding Calcium Salts of Linseed Oil on Metabolic Status and Reproductive Traits in Grazing Dairy Cows

This experiment aimed to evaluate the effect of calcium salts of linseed oil (rich in alpha-linolenic acid (ALA, C18:3n-3) on metabolic and reproductive traits in high-producing dairy cows under grazing. Thirty-six Holstein dairy cows were randomly assigned, in a complete block design, to receive ALA supplementation (0.85 kg∙day−1 of calcium salts of linseed oil) or to remain as untreated control (CON). The concentrate was formulated to offer the same amount of energy across treatments (CON cows received an extra kg of corn to compensate for the higher energy density of ALA treatment). A PMR + Alfalfa pasture was offered to all cows at the same time. A fixed time artificial insemination (FTAI) at 80 DIM, preceded by a Presynch plus Ovsynch protocol was implemented for the first service and later, on return to estrus, heat detection and artificial insemination (AI) were performed. Pregnancy diagnosis was checked at 30, 42, 60, and 90 d after AI. Blood and milk samples were taken biweekly. Treatment affected plasma cholesterol concentration (160.36 vs. 186.70 mg∙dl−1, p = 0.03, for ALA and CON, respectively) and on size of corpus luteum (CL, 17.6 vs. 13.7 mm, p = 0.02, for ALA and CON, respectively). Supplementation tended (p = 0.136) to increase conception rate by 200 DIM (81.69% vs. 55.43% in ALA and CON cows, respectively). However, treatment had no effect (p > 0.05) on body weight (BW), body condition score (BCS), and circulating levels of beta-hydroxybutyrate (BHBA), glucose, insulin, growth hormone (GH) and insulin-like growth factor (IGF-I). Our results suggest that supplementation with calcium salts of linseed oil could enhance ovarian function without affecting energy metabolism in early lactation dairy cows.

Effects of long-term grazing exclusion on vegetation structure,soil water holding capacity,carbon and nitrogen sequestration capacity in an alpine meadow on the Tibetan Plateau

Grazing exclusion is one of the primary management practices used to restore degraded grasslands on the Tibetan Plateau.However,to date,the effects of long-term grazing exclusion measures on the process of restoring degraded alpine meadows have not been evaluated.In this study,moderately degraded plots,in which the vegetation coverage was approximately 65%and the dominant plant species was Potentilla anserina L,with grazing exclusion for 2 to 23 years,were selected in alpine meadows of Haibei in Qinghai-Tibet Plateau.Plant coverage,plant height,biomass,soil bulk density,saturated water content,soil organic carbon(SOC)and total nitrogen(TN)were evaluated.The results were as follows:(1)With aboveground biomass and total saturated water content at 0-40 cm depth,the average SOC and TN contents in moderately degraded alpine meadows increased as a power function,and the plant height increased as a log function.(2)The average soil bulk density at 0-40 cm depth first decreased and then increased with increasing grazing exclusion duration,and the minimum value of 0.90 g·cm^(-3) was reached at 15.23 years.The plant coverage,total belowground biomass at 0-40 cm depth,total aboveground and belowground biomass first increased and then decreased,their maximum values(80.49%,2452.92g·m^(-2),2891.06 g·m^(-2))were reached at 9.41,9.46 and 10.25 years,respectively.Long-term grazing exclusion is apparently harmful for the sustainable restoration of degraded alpine meadows.The optimal duration of grazing exclusion for the restoration of moderately degraded alpine meadows was 10 years.This research suggests that moderate disturbance should be allowed in moderately degraded alpine meadows after 10years of grazing exclusion.

Does nature-based solution sustain grassland quality? Evidence from rotational grazing practice in China

Rotational grazing is considered as one of the nature-based solutions(NbS)to grassland protection by natural scientists.However,its effects on improving grassland quality are still unclear when it is adopted by herders.Using a householdlevel panel data from field survey in two main pastoral provinces of China,empirical results from fixed-effect model and instrumental approach show that rotational grazing practices have insignificant short-term effects on grassland quality,but have positive long-term effects.In addition,rotational grazing practices can improve grassland quality when villages invest public infrastructure or herders have private supporting measures for more efficiency livestock production.Further analysis shows that herders adopting rotational grazing have higher grazing intensity,higher supplementary intensity and more livestock-house-feeding days,which indicate herders can utilize more efficient livestock management without increasing pressure on natural grassland.We also find that herders with pastoral income are more likely to adopt rotational grazing practice.These insightful findings offer policy implications on promoting grassroot NbS for ecosystem protection and resource utilization in developing pastoral countries.

Long-term light grazing does not change soil organic carbon stability and stock in biocrust layer in the hilly regions of drylands

Livestock grazing is the most extensive land use in global drylands and one of the most extensive stressors of biological soil crusts(biocrusts).Despite widespread concern about the importance of biocrusts for global carbon(C)cycling,little is known about whether and how long-term grazing alters soil organic carbon(SOC)stability and stock in the biocrust layer.To assess the responses of SOC stability and stock in the biocrust layer to grazing,from June to September 2020,we carried out a large scale field survey in the restored grasslands under long-term grazing with different grazing intensities(represented by the number of goat dung per square meter)and in the grasslands strictly excluded from grazing in four regions(Dingbian County,Shenmu City,Guyuan City and Ansai District)along precipitation gradient in the hilly Loess Plateau,China.In total,51 representative grassland sites were identified as the study sampling sites in this study,including 11 sites in Guyuan City,16 sites in Dingbian County,15 sites in Shenmu City and 9 sites in Ansai District.Combined with extensive laboratory analysis and statistical analysis,at each sampling site,we obtained data on biocrust attributes(cover,community structure,biomass and thickness),soil physical-chemical properties(soil porosity and soil carbon-to-nitrogen ratio(C/N ratio)),and environmental factors(mean annual precipitation,mean annual temperature,altitude,plant cover,litter cover,soil particle-size distribution(the ratio of soil clay and silt content to sand content)),SOC stability index(SI)and SOC stock(SOCS)in the biocrust layer,to conduct this study.Our results revealed that grazing did not change total biocrust cover but markedly altered biocrust community structure by reducing plant cover,with a considerable increase in the relative cover of cyanobacteria(23.1%)while a decrease in the relative cover of mosses(42.2%).Soil porosity and soil C/N ratio in the biocrust layer under grazing decreased significantly by 4.1%–7.2%and 7.2%–13.3%,respectively,compared with those under grazing exclusion.The shifted biocrust community structure ultimately resulted in an average reduction of 15.5%in SOCS in the biocrust layer under grazing.However,compared with higher grazing(intensity of more than 10.00 goat dung/m2),light grazing(intensity of 0.00–10.00 goat dung/m2 or approximately 1.20–2.60 goat/(hm2•a))had no adverse effect on SOCS.SOC stability in the biocrust layer remained unchanged under long-term grazing due to the offset between the positive effect of the decreased soil porosity and the negative effect of the decreased soil C/N ratio on the SOC resistance to decomposition.Mean annual precipitation and soil particle-size distribution also regulated SOC stability indirectly by influencing soil porosity through plant cover and biocrust community structure.These findings suggest that proper grazing might not increase the CO_(2) release potential or adversely affect SOCS in the biocrust layer.This research provides some guidance for proper grazing management in the sustainable utilization of grassland resources and C sequestration in biocrusts in the hilly regions of drylands.

Influence of rangeland protection and seasonal grazing on aboveground vegetation,forage quality and weight gain of small ruminants–a study in Thar Desert,Pakistan

The Thar Desert,Sindh,Pakistan is characterized by low productivity.Besides,economy is based on agriculture,livestock and mining,nevertheless,livestock graze freely on public and private land.The aim of this research was to determine biomass production and to evaluate the effects of continuous and seasonal grazing on protected and unprotected plots.A 45 ha protected rangeland area of Hurrabad in the Umerkot Thar desert was selected and divided into three blocks of 15 ha each.Blocks of the same size were also established in unprotected area.The data for vegetation biomass,canopy cover,forage nutrients and weight gain of animals in two seasons(spring and summer)was collected from both protected and unprotected sites.The results showed that biomass significantly increased in summer in both sites.However,the biomass values in protected sites were significantly higher.Similarly,the vegetation cover also seemed to increase in summer in both protected(90.7%±0.29%)and unprotected sites(39.2%±0.09%).The foliar concentrations of all nutrients varied significantly with season.The average final live-weight gain for does on the protected grazing sites during the 42-day period in spring and the 96 days after the monsoon was almost double that of does grazing on the unprotected site during 2016 and 2017(P<0.05).The study concludes that the protection of grazing lands during certain periods can lead to better production of vegetation and livestock and improve range conditions.

Preliminary Study of Microzooplankton Grazing and Community Composition in the North of South China Sea in Autumn

Microzoopiankton community composition in the north of South China Sea was investigated during autumn （between September and October）, 2004. Dilution technique using chlorophyll a （Chl a） was employed to estimate grazing rates and grazing pressure. The results showed that Polymenophorea Oligotrichida was the dominant group with 16 species, and there were 4 species in Oligotrichina and 11 species in Tintinnina. The ciliates abundance ranged from 9 to 102 ind/m^3, instantaneous growth rates of phytoplankton （k） varied from 0.03 / d to 2.13 / d. Grazing rates of microzooplankton（g） ranged between 0.01 / d and 1.06 / d. The grazing pressure on initial phytoplankton stock （Pi） and primary production （Pp） was 0.089 % - 65.23 % and 33.63 % - 86.04 %, respectively. The grazing of microzooplankton was mainly limited by ciliates abundance. Results of grazing pressure on primary production indicated that microzooplankton played an improtant role in transmitting primary production in the north of South China Sea.

Studies on growth rate and grazing mortality rate by microzooplankton of size-fractionated phytoplankton in spring and summer in the Jiaozhou Bay,China

Dilution experiments were performed to examine the growth rate and grazing mortality rate of size-fractionated phytoplankton at three typical stations, inside and outside the bay, in the spring and summer of 2003 in the Jiaozhou Bay, China. In spring, the phytoplankton community structure was similar among the three stations, and was mainly composed of nanophytoplankton, such as, Skeletonema costatum and Cylindrotheca closterium. The structure became significantly different for the three stations in summer, when the dominant species at Stas A, B and C were Chaetoceros curvisetus, Pseudo-nitzschia delicatissima, C. affinis, C. debilis, Coscinodiscus oculus-iridis and Paralia sulcata respectively. Tintinnopsis beroidea and T. tsingtaoensis were the dominant species in spring, whereas the microzooplankton was apparently dominated by Strombidium sp. in summer. Pico- and nanophytoplankton had a relatively greater growth rate than microzooplankton both in spring and summer. The growth rate and grazing mortality rate were 0.18~0.44 and 0.12~1.47 d-1 for the total phytoplankton and 0.20~0.55 and 0.21~0.37 d-1 for nanophytoplankton in spring respectively. In summer, the growth rate and grazing mortality rate were 0.38~0.71 and 0.27~0.60 d-1 for the total phytoplankton and 0.11~1.18 and 0.41~0.72 d-1 for nano- and microphytoplankton respectively. The carbon flux consumed by microzooplankton per day was 7.68~39.81 mg/m3 in spring and 12.03~138.22 mg/m3 in summer respectively. Microzooplankton ingested 17.56%~92.19% of the phytoplankton standing stocks and 31.77%~467.88% of the potential primary productivity in spring; in contrast, they ingested 34.60%~83.04% of the phytoplankton standing stocks and 71.28%~98.80% of the potential primary productivity in summer. Pico- and nanophytoplankton appeared to have relatively greater rates of growth and grazing mortality than microphytoplankton during the experimental period. The grazing rate of microzooplankton in summer was a little bit greater than that in spring because of the relatively higher incubation temperature and different dominant microzooplankton species. Microzooplankton preferred ingesting nanophytoplankton to microphytoplankton in spring, while they preferred ingesting picophytoplankton to nanophytoplankton and microphytoplankton in summer. Compared with the results of dilution experiments performed in various waters worldwide, the results are in the middle range.

Effects of Grazing Exclusion on Soil Carbon and Nitrogen Storage in Semi-arid Grassland in Inner Mongolia, China

The semi-arid grasslands in Inner Mongolia, China have been degraded by long-term grazing. A series of ecological restoration strategies have been implemented to improve grassland service. However, little is known about the effect of these ecological restoration practices on soil carbon and nitrogen storage. In this study, characteristics of vegetation and soil properties under continued grazing and exclusion of livestock for six years due to a nationwide conservation program—′Returning Grazing Lands to Grasslands(RGLG)′ were examined in semi-arid Hulun Buir grassland in Inner Mongolia, China. The results show that removal of grazing for six years resulted in a significant recovery in vegetation with higher above and below-ground biomass, but a lower soil bulk density and pH value. After six years of grazing exclusion, soil organic C and total N storage increased by 13.9% and 17.1%, respectively, which could be partly explained by decreased loss and increased input of C and N to soil. The effects of grazing exclusion on soil C and N concentration and storage primarily occurred in the upper soil depths. The results indicate that removal of grazing pressure within the RGLG program was an effective restoration approach to control grassland degradation in this region. However, more comprehensive studies are needed to evaluate the effectiveness of the RGLG program and to improve the management strategies for grassland restoration in this area.

Effects of grazing on net primary productivity,evapotranspiration and water use efficiency in the grasslands of Xinjiang,China

Grazing is a main human activity in the grasslands of Xinjiang, China. It is vital to identify the effects of grazing on the sustainable utilization of local grasslands. However, the effects of grazing on net primary productivity （NPP）, evapotranspiration （ET） and water use efficiency （WUE） in this region remain unclear. Using the spatial Biome-BGC grazing model, we explored the effects of grazing on NPP, ET and WUE across the different regions and grassland types in Xinjiang during 1979-2012. NPP, ET and WUE under the grazed scenario were generally lower than those under the ungrazed scenario, and the differences showed increasing trends over time. The decreases in NPP, ET and WUE varied significantly among the regions and grassland types. NPP decreased as follows： among the regions, Northern Xinjiang （16.60 g C/（m2·a））, Tianshan Mountains （15.94 g C/（m2·a）） and Southern Xinjiang （-3.54 g C/（m2·a））; and among the grassland types, typical grasslands （25.70 g C/（m2·a））, swamp meadows （25.26 g C/（m2·a））, mid-mountain meadows （23.39 g C/（m2·a））, alpine meadows （6.33 g C/（m2·a））, desert grasslands （5.82 g C/（m2·a）） and saline meadows （2.90 g C/（me.a））. ET decreased as follows： among the regions, Tianshan Mountains （28.95 mm/a）, Northern Xinjiang （8.11 mm/a） and Southern Xinjiang （7.57 mm/a）; and among the grassland types, mid-mountain meadows （29.30 mm/a）, swamp meadows （25.07 mm·a）, typical grasslands （24.56 mm/a）, alpine meadows （20.69 mm/a）, desert grasslands （11.06 mm/a） and saline meadows （3.44 mm/a）. WUE decreased as follows： among the regions, Northern Xinjiang （0.053 g C/kg H2O）, Tianshan Mountains （0.034 g C/kg H2O） and Southern Xinjiang （0.012 g C/kg H2O）; and among the grassland types, typical grasslands （0.0609 g C/kg H2O）, swamp meadows （0.0548 g C/kg H2O）, mid-mountain meadows （0.0501 g C/kg H2O）, desert grasslands （0.0172 g C/kg H2O）, alpine meadows （0.0121 g C/kg H2O） and saline meadows （0.0067 g C/kg H2O）. In general, the decreases in NPP and WUE were more significant in the regions with relatively high levels of vegetation growth because of the high grazing intensity in these regions. The decreases in ET were significant in mountainous areas due to the terrain and high grazing intensity.

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.

Changes of Protective Enzyme Activity and MDA Content in Leaves of Agropyron cristatum Under Grazing Stress

[Objective] This study was conducted to explore the mechanism of physi- ological adaptation of Agropyron cristatum under grazing pressure, and to provide a theoretical basis for the protection and rational utilization of forage resources, breeding and introduction of high-quality forage materials. [Method] The mature leaves of upper parts of A. cristatum plants in grazed and non-grazed areas were collected at tillering （late May）, heading （late June）, flowering （late July） and seed maturity （late August） stages for determination of superoxide dismutase （SOD）, peroxidase （POD） activities and malondialdehyde （MDA） content. [Result] The MDA content of grazing population was higher than that of non-grazing population throughout the whole growth period of A. cristatum. The SOD activity was significantly increased from heading to flowering stage but was rapidly reduced at seed maturity stage, with no significant difference between grazing and non-grazing populations of A. cristatum. The POD activity kept increasing from heading stage, and it was higher of grazing population than that of non-grazing population. [Conclusion] The MDA content in leaves of A. cristatum was increased under grazing pressure, leading to increased membrane lipid oxidation; POD played an important role in removal of the free radicals those accumulated in A. cristatum under grazing pressure.

Suppression of grazing-induced instability in single degree-of-freedom impact oscillators

As a typical non-smooth bifurcation, grazing bifurcation can induce instability of elementary near-grazing impact periodic motion in impact oscillators. In this paper,the stability for near-grazing period-one impact motion to suppress grazing-induced instabilities is analyzed, based on which, a control strategy is proposed. The commonly-used leading order zero time discontinuity mapping is extended to a higher order one to aid the perturbation analysis of the characteristic equation. It is shown that the degenerate grazing bifurcation can eliminate the singular term in the characteristic equation, leading to bounded eigenvalues. Based on such a precondition, the bounded eigenvalues are further restricted inside the unit circle, and a continuous transition between non-impact and controlled impact motion is observed. One discrete feedback controller that changes the velocity of the oscillator based on the selected Poincar′e sections is adopted to demonstrate the control procedure.

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.

Investigating factors driving phytoplankton growth and grazing loss rates in waters around Peninsular Malaysia

In tropical waters where temperatures are relatively stable,we investigated whether the relationship between phytoplankton growth and grazing loss rate across diff erent habitats around Peninsular Malaysia can be attributed to its eutrophication states.We measured phytoplankton growth(μ)and grazing loss(g)rates in waters off Bachok Marine Research Station(BMRS),located northeast of Peninsular Malaysia.Chlorophyll-a(chl-a)concentration ranged from 2.90 to 15.78μg/L and was dominated by nanoand micro-phytoplankton(>2μm in size).Using the Landry and Hassett dilution method,μat BMRS ranged from 1.02 to 1.58/d whereas g varied from 0.07 to 0.88/d.Grazing accounted for 35%of the primary production at BMRS.A systematic review of available data in waters around Peninsular Malaysia,revealed howμfl uctuated over a wide range(0.01–1.80/d)and correlated with chl a distribution(R 2=0.181,P<0.001).However,the relationship was only signifi cant at<9μg/L chl a for mesotrophic waters and<16μg/L chl a for eutrophic waters.In contrast,g ranged from 0.00 to 1.01/d,and correlated withμat all locations.The g/μslope ranged from 19%to 84%,and was generally similar for waters around Peninsular Malaysia.However,all the g/μslopes had a positive y-intercept except for BMRS,and this seemed to suggest the availability of alternative prey supporting grazing at the other stations.

Analysis of Temporal Changes in Botanical Composition of a Long-term Grazing Experiment in Nixinasuno, Japan

In order to understand the temporal changes of botanical composition in grassland ecosystem, and to clarify the relation between these changes and environmental impacts, such as climatic factors and artificial disturbance, a grazing trail was carried out during a 21-year period from 1974 at a sown grassland of the National Grassland Research Institute, located in Nishinasuno, the central area of Japan. The data sets of biomass for each mouth(from April to November)of the 21 year period were analyzed in this paper. The botanical composition of aboveground biomass varied greatly with both season and year. The biomass ratio of improved herbage species to invaded native plants gradually decreased each year. This may have been owing to meteorological factors, such as low air-temperature in winter, dry and hot summers, grassland management(including grazing intensity and fertilizer application), and inter-specific competition between native and introduced herbage plants.

Influences of various grazing systems on community biomass of a desert grassland in Inner Mongolia,China

This study investigated the effects of various grazing systems, including continuous grazing, rotational grazing, and no-grazing systems, on the community biomass in the Stipa breviflora Griseb desert grassland during the grazing seasons in 2005, 2006, and 2007, based on study sites established in 1999. We found that the seasonal dynamics of the aboveground biomass were quite similar among the three treatments, which reached peak values in period from August to September during each study year. The continuous grazing system reduced the aboveground biomass from 2005 to 2007 under drought conditions, and the rotational grazing and no-grazing systems maintained more aboveground biomass than the continuous grazing system did. The belowground biomass declined with the increase of soil depth among the three treatments, and in the surface 20-cm soil layer it accounted for more than 60% of the total biomass. The belowground biomass was found to be highly correlated with soil depth under rotational grazing. The total belowground biomass within the 0--100-cm soil layer for rotational grazing was sig- nificantly higher than for continuous grazing and no-grazing, and had 15,775 kg/ha more biomass. Our results demonstrate that conservative rotational grazing can alleviate grassland deterioration by reserving more aboveground and belowground biomass than the continuous grazing system does.