Effects Of Grazing Intensity Research Articles

Impact of livestock activity on near-surface ground temperatures in central Mongolian grasslands

Abstract. Grazing by livestock can alter the surface conditions at grassland sites, impacting the transfer of energy between the atmosphere and ground and consequentially ground temperatures. In this study, we investigate surface cover in summer and winter and measure ground surface temperatures over 14 months at sites in central Mongolia that feature different grazing intensities (intensely and ungrazed) and topographic aspects (north- and south-facing). Overall, intense grazing leads to a substantially reduced vegetation cover, altered snow conditions, and lack of surface litter accumulation. Comparing intensely grazed and ungrazed plots shows large seasonal differences in ground surface temperatures, with grazed plots being up to +5.1 °C warmer in summer and −5.4 °C colder in winter at a south-facing site. We also find that the effect of grazing intensity depends on topographic aspect, with smaller seasonal differences of +1.4 °C and −2.5 °C found between grazed and ungrazed plots at a north-facing site. This relates to the lower available solar radiation at north-facing sites, which reduces the differences in vegetation cover between open and fenced plots. For both aspects, the seasonal differences largely offset each other, with both a small net cooling and warming depending on effects in spring and autumn. Our study suggests that livestock management could be used to modify the annual ground temperature dynamics, possibly even influencing local permafrost dynamics.

Divergent Effects of Grazing Intensity on Soil Nutrient Fractions in Alpine Meadows

ABSTRACTLarge herbivore grazing plays a key role in regulating ecosystem functioning and nutrient cycling in terrestrial ecosystems. However, the effects and mechanisms of large herbivore grazing intensity on soil nutrient fractions remain largely unclear in alpine grasslands. Here, we determine 20 indicator variables associated with soil nutrient fractions (e.g., particulate organic carbon, POC; mineral‐associated organic carbon, MAOC) to investigate how grazing intensity on labile fractions through a well‐controlled grazing experiment in an alpine meadow on the eastern Tibetan Plateau. Our results show that microbial biomass carbon, dissolved organic carbon, light fraction organic carbon, microbial biomass nitrogen and phosphorus, total potassium, and available potassium significantly decrease with increased grazing intensity, whereas other fractions (e.g., POC, MAOC, dissolved organic nitrogen, ammonium nitrogen, nitrate nitrogen, available nitrogen, etc.) have marginal or non‐significant responses to grazing intensity. Further analysis reveals that above‐and below‐ground biomass, soil moisture, and soil pH jointly determine the grazing effects on soil nutrient fractions, without the impact of species richness. Moreover, correlation analyses indicate that grazing intensity decouples carbon and nitrogen from phosphorus and potassium in alpine meadows. Collectively, our results emphasize the importance of grazing intensity effects on nutrient cycling in alpine grasslands and incorporate the impacts of grazing intensity into terrestrial ecosystem models may help accurately predict carbon sequestration potential in grazinglands.

Pastoralism in the high tropical Andes: A review of the effect of grazing intensity on plant diversity and ecosystem services

AbstractAimsPastoralism is a land‐use system that involves the care and use of grazing livestock and has been more common in areas of low resource availability. In this review, we analyze the impact of pastoralism on biodiversity and ecosystem services across the tropical Andes. This region is the most extensive and populated tropical mountain region in the world and presents a high diversity of biomes, livestock types and management histories. Given that pastoralism is a main land use here, understanding its impacts is important for providing appropriate recommendations for sustainable management.LocationTropical Andes; Venezuela to the north of Argentina and Chile.MethodsTo understand these impacts, we performed a systematic literature search (August 2021) and obtained 103 articles. We created a conceptual framework to map how available research has contributed to our understanding of the main pastoral systems, their associated management strategies and the impact of different grazing intensities on vegetation cover/diversity and ecosystem services.ResultsWe found that research has focused on two leading pastoral systems in the region: bovines in the páramo biome of the northern Andes and camelids in the puna biome of the central Andes. We found important environmental impacts at high grazing intensities for both the puna camelid and páramo bovine pastoral systems, including a decrease in soil organic carbon and an increase in soil compaction, a decrease in above‐ground biomass, plant species richness, and graminoid cover, as well as clear changes in the growth‐form composition of vegetation.ConclusionsGiven these findings, we recommend coordinated research efforts using common methodologies, documenting current and previous land use, including stocking rates, and combining observational and experimental approaches to develop a more integrated understanding of pastoralism's impacts across this diverse and vulnerable region.

Exploring grazing intensity effects: nitrogen uptake in grassland species and soil carbon allocation

Exploring grazing intensity effects: nitrogen uptake in grassland species and soil carbon allocation

Diversified vegetation types on rangelands promote multiple soil‐based ecosystem services

AbstractRangelands have the potential to be provisioners of ecosystem services, including livestock products, carbon storage and greenhouse gas regulation, water and nutrient cycling, wildlife habitat, and biodiversity. Due to their vast extent and landscape heterogeneity, the degree to which different ecological components of rangelands contribute to ecosystem services can be varied. Soils are the foundation of rangeland health and associated ecosystem services. While many studies have examined the effect of grazing intensity on rangeland ecosystem services, few studies have looked at the broader rangeland landscape and how managing varying vegetation types can influence soil‐based ecosystem services. In this study, a suite of physical, chemical, and biological soil health indicators were measured in various vegetation types found within a working cattle ranch, including coastal live oak woodlands, coastal scrublands, annual grassland, and restored native perennial grassland. Based on the measured soil health indicators, results from this study show scrubland significantly diverges from other vegetation types, having higher water infiltration and plant available water, carbon stocks, and a more diverse microbial community that drives more dynamic cycling of carbon and nitrogen. Strategically maintaining scrubland on unproductive, highly erosive slopes downgradient of highly productive grassland areas could maintain forage production while protecting water quality and increasing carbon storage. These results highlight the relevance of holistically evaluating rangeland operations to assess soil function and ecosystem services and the potential risks and co‐benefits of varying vegetation types. Ultimately, process‐based linkages described here may provide a working example of how to manage ranches as functional mosaics of strategically maintained vegetation types.

Grazing intensity effects on rangeland condition and tree diversity in Afar, northeastern Ethiopia

This study assessed the effects of different grazing pressures (light, moderate and heavy) on rangeland condition and woody species diversity in northeastern Ethiopia. Rangeland condition was analyzed using common protocols for the assessment of semi-arid rangelands. A total of 4 grasses, 5 herbs, 1 sedge and 14 tree and/or shrub species were identified. Results show that grazing intensity had detrimental effects on condition of the rangeland, and caused undesirable changes in herbaceous species composition. The contribution of undesirable plants to herbaceous aboveground biomass was particularly high (40 %) compared to the 30 % contributed by highly desirable species. Nearly all measures of range condition were negatively affected by grazing. Grass composition, number of seedlings and age distribution, basal and litter cover, soil erosion and compaction decreased significantly as grazing intensity increased. Species richness and diversity (Hill numbers) of woody plants were reduced significantly by grazing. The overall condition of the rangeland was generally poor. The pastoralists perceived that recurring droughts, heavy continuous grazing and inappropriate management interventions, and bush encroachment were the main contributing factors that led to overgrazing and rangeland deterioration in the area. In conclusion, our study shows that livestock grazing in northeastern Ethiopia degrade range condition and woody vegetation, and its effects are sever under moderate and heavy grazing. Management measures such as resting of the rangelands preferably with stock exclusions for 6–12 months or protecting heavily degraded or sensitive areas from livestock activity and reseeding may be the viable options to mitigate declines in range conditions.

Relationships between plant species richness and grazing intensity in a semiarid ecosystem.

Plant species richness is an important property of ecosystems that is altered by grazing. In a semiarid environment, we tested the hypotheses that (1) small-scale herbaceous plant species richness declines linearly with increasing grazing intensity by large ungulates, (2) precipitation and percent sand interact with grazing intensity, and (3) response of herbaceous plant species richness to increasing intensity of ungulate grazing varies with patch productivity. During January-March 2012, we randomly allocated 50, 1.5-m × 1.5-m grazing exclosures within each of six 2500 ha study sites across South Texas, USA. We counted the number of herbaceous plant species and harvested vegetation in 0.25-m2 plots within exclosures (ungrazed control plots) and in the grazed area outside the exclosures (grazed treatment plots) during October-November 2012-2019. We estimated percent use (grazing intensity) based on the difference in herbaceous plant standing crop between control plots and treatment plots. We selected the negative binomial regression model that best explained the relationship between grazing intensity and herbaceous plant species richness using the Schwarz-Bayesian information criterion. After accounting for the positive effect of precipitation and percent sand on herbaceous plant species richness, species richness/0.25 m2 increased slightly from 0% to 30% grazing intensity and then declined with increasing grazing intensity. Linear and quadratic responses of herbaceous plant species richness to increasing grazing intensity were greater for the least productive patches (<15.7 g/0.25 m2) than for productive patches (≥15.7 g/0.25 m2). Our results followed the pattern predicted by the intermediate disturbance hypothesis model for the effect of grazing intensity on small-scale herbaceous plant species richness.

Grazing intensity effects on herbaceous community composition in burned sagebrush steppe

AbstractThere is limited knowledge of grazing impacts on longer term plant community dynamics following fire in sagebrush steppe. This study evaluated vegetation response to different intensities of deferred rotation cattle grazing over 16 years (2007–2022) on burned Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis (Beetle &amp; Young) Welsh) steppe in eastern Oregon. Treatments were applied in a randomized complete block, which included no grazing on burned (nonuse, n = 5) and unburned (control, n = 5) steppe; and cattle grazing at low (low, n = 4), moderate (moderate, n = 4), and high (high, n = 4) intensities on burned steppe. Vegetation dynamics were evaluated by repeated measures analysis of canopy cover and density of shrub and herbaceous species and functional groups. Herbaceous functional groups were an early‐season bunchgrass (one species, Sandberg bluegrass [Poa secunda J. Presl]), tall perennial bunchgrasses, perennial forbs, annual grass (one species, cheatgrass [Bromus tectorum L.]), and annual forbs. Tall perennial bunchgrass, Sandberg bluegrass, and perennial forb cover and density did not differ among the treatments but did decrease over time in all treatments. The cover of several tall bunchgrass species was generally less in the high treatment, mainly, Idaho fescue (Festuca idahoensis Elmer) and Thurber's needlegrass (Achnatherum thurberianum (Piper) Barkworth). The cover of cheatgrass and annual forbs varied among years but was greater in the burned‐grazed and nonuse treatments than in the control. Native plant cover in the burned treatments (grazed and nonuse) represented 77%–85% of total herbaceous cover versus the control where native plants comprised 91% of the total. Annual weather variability appears to account for most of the compositional dynamics measured in the various grazed and ungrazed treatments.

The effect of grazing intensity on pattern dynamics of the vegetation system

The evolution of vegetation system in arid and semi-arid grazing areas is a complex dynamical system which depends not only on the rainfall, but also grazing intensity. Currently, most of the research focuses on the influence of rainfall, but the effects of grazing have not been fully understood. Simultaneously, the intraspecific competition delay widely exists in vegetation system. In this project, we develop a vegetation model coupled with the intraspecific competition delay, discuss the vegetation pattern caused by the combination of grazing intensity, rainfall and competition delay, by analyzing conditions of the occurrence of Turing instability. In particular, we propose a new theoretical method to deal with the Turing instability of delayed diffusion system when the system exists a zero eigenvalue and the corresponding transversity condition is not zero. Using the theory of dynamics, we can show: (i) a bistable region in which vegetation-existence and vegetation-extinction states coexist for relatively large grazing rate, in the corresponding ordinary differential system, while the vegetation-existence state is replaced by vegetation pattern state for non-delayed diffusion system, and the range of bistable region is extended as the increase of rainfall; (ii) spatial distribution structure and spatially mean density of vegetation patterns reveal that degradation of the vegetation becomes more and more obvious with the increase of grazing intensity; (iii) the bistable region corresponding to the delayed diffusion system is narrowed, and vegetation system undergoes regime shift from the pattern state to bare-soil state before reaching the threshold of grazing rate. Overall, this study yields a new theoretical perspective for pattern dynamics of delayed reaction–diffusion equation, and provides valuable insights into the study of vegetation system in grazing ecosystem.

Light grazing reduces gaseous nitrogen emissions from temperate grassland soils during freeze‒thaw cycles: An intact core incubation study

Livestock grazing and soil freeze‒thaw cycles (FTCs) can affect the biogeochemical processes of nitrogen (N) and gaseous N (N2O, NO, and N2) emissions from grassland soils. However, the effect of grazing intensity on soil gaseous N emissions during FTCs and the underlying mechanisms are not clearly understood. In this intact core incubation study, soil gaseous N emissions during two FTCs were simultaneously quantified from temperate grasslands that included grazing exclusion (GE), light grazing (LG), and heavy grazing (HG) in Inner Mongolia. Additionally, the abundance of N cycle-related functional genes and the main soil characteristics were determined to better understand the drivers of gaseous N emissions. The results showed that N2 emissions dominate the gaseous N loss from all investigated soils during FTCs, with cumulative N2 exceeding NO and N2O emissions by factors of 47–135 and 71–161, respectively. Increased soil moisture during thawing promoted N2 and N2O emissions from all three sites, except for N2O at the LG site. However, no obvious NO emission peak was observed from all investigated soils during FTCs. Soil C and N availability and aeration changed by grazing regulated soil N2O fluxes, while the abundances of key functional genes generally did not show significant correlations with gaseous N emissions. Moreover, compared to the GE and HG sites, LG substantially decreased the soil N2O and total gaseous N emissions during FTCs, suggesting that light grazing rather than long-term grazing exclusion could be a promising measure to reduce gaseous N losses during spring thaw. Our results highlighted the importance of the simultaneous determination of all kinds of gaseous N emissions during FTCs for closing the ecosystem N balance and developing appropriate strategies for grassland management.

Grazing intensity effects on sward responses of UF Riata Bahiagrass

AbstractBahiagrass (Paspalum notatum Flüggé) is a rhizomatous, perennial, warm‐season forage widely grown in the southeastern United States "UF Riata" bahiagrass is more upright growing with greater herbage production when days are shorter compared with most other cultivars. Lesser daylength sensitivity extends the grazing season, but in combination with more upright growth may negatively affect persistence under grazing, especially if out‐of‐season herbage production interferes with normal reserve storage. This 3‐year study investigated above and belowground sward responses of UF Riata bahiagrass to three levels of post‐grazing herbage mass (HM) (500 [heavy grazing, HG], 1500 [moderate grazing], or 2500 [light grazing, LG] kg DM ha−1, where DM is dry matter) imposed by mob stocking every 14 days. Total herbage accumulation (HA) and HA rate were not affected by treatment. Crude protein (CP) was affected by treatment × grazing cycle × year, whereas in vitro digestible organic matter concentrations were affected by treatment × year and grazing cycle × year. Root–rhizome biomass (12,940–9230 kg OM ha−1, where OM is organic matter) and soil cover percentage (97%–93%) decreased linearly as grazing intensity increased from LG to HG. Proportion of non‐planted grasses was 34% and 17% in HG and LG swards, respectively. Proportion of non‐grass weeds increased across treatments from 2% to 22% over the years. Moderate grazing could maintain similar CP to HG, and similar root–rhizome biomass to LG. Thus, considering both sward persistence and forage nutritive value, a target post‐grazing HM of ≈1500 kg DM ha−1 is recommended when UF Riata pastures are grazed every 2 weeks.

Integrated crop-livestock systems result in less nitrate leaching than ungrazed crop systems in North Florida.

Integrated crop-livestock systems provide an array of benefits to agricultural systems, including a reduction in nitrogen (N) leaching. A farm approach to integrate crops and livestock is the adoption of grazed cover crops. Moreover, the addition of perennial grasses into crop rotations may improve soil organic matter and decrease N leaching. However, the effect of grazing intensity in such systems is not fully understood. This 3-year study investigated short-term effects of cover crop planting (cover and no cover), cropping system (no grazing, integrated crop-livestock [ICL], and sod-based rotation [SBR]), grazing intensity (heavy, moderate, and light grazing), and cool-season N fertilization (0, 34, and 90kg N ha-1 ) on NO3 -N and NH4 -N concentration in leachate, and cumulative N leaching by using 1.5-m deep drain gauges. The ICL was a cool-season cover crop-cotton (Gossypium hirsutum L.) rotation, whereas SBR was a cool-season cover crop-bahiagrass (Paspalum notatum Flüggé) rotation. There was a treatment × year × season for cumulative N leaching (p=0.035). Further contrast analysis indicated that cover crops decreased cumulative N leaching compared to no cover (18vs. 32kg N ha-1 season-1 ). Nitrogen leaching was lesser for grazed compared to nongrazed systems (14vs. 30kg N ha-1 season-1 ). Treatments containing bahiagrass had lesser NO3 -N concentration in leachate (7vs. 11mg L-1 ) and cumulative N leaching (8vs. 20kg N ha-1 season-1 ) compared to ICL systems. Adding cover crops can reduce cumulative N leaching in crop-livestock systems; moreover, warm-season perennial forages can further enhance this benefit.

Relationship of Plant Species Diversity and Sampling Area Under Different Grazing Intensities in the Steppe of Northern China

The relationship between sampling area of plant community and number of species contained in it has an importance in vegetation ecology. Using a nested quadrat survey, the relationship between plant species and sampling area was discussed under different grazing pressure in the steppe and the determination of minimum sampling area was calculated herein. Ten curve models were selected to fit the species-area relation of plant community in a typical steppe of northern China. The residual standard deviation, correlation index, average value of absolute deviation, and average value of absolute relative deviation were used as the evaluation indexes for model fitting. The results show that the curve equations S = B + CAZ and S = C(1-e−BA)Z have the best simulation effect. According to the simulation results, the minimum sampling areas are determined as 1.16 m2 (T0), 1.23 m2 (T7), 1.28 m2 (T10), and 1.10 m2 (T14), presenting the minimum sampling area is feasible when the second derivative is zero. Generally, sheep grazing reduced the species richness of steppe, though some of the plans flourished while some others disappeared or dismissed, but increased spatial heterogeneity, especially on a smaller scale. However, there are also variances in different area scales and grazing intensities. When the sampling area was small (< 2 m2), heavy grazing T14 increased the number of plant species per unit area, yet light grazing T8 reduced the number of plant species per unit area of steppe. When the sampling area was large (> 16 m2), grazing reduced the number of plant species per unit area in the natural steppe. Anyhow, the effect of grazing intensity on plant species fluctuated greatly when the sampling area was medium (2 m2 ∼ 16 m2). In general, the similarity of plant communities had an increasing trend with accumulated sampling area, though it varied at different grazing intensities.

Grazing intensity's effects on rangeland vegetation

Mongolia is a massive, semi-arid country in central Asia that encompasses 1,500,000 km2, with grasslands making up around 75% of the territory. These grasslands have long supported herders and are important for grazing animals. However, one of the most severely impacted ecosystems in the world is the Mongolian rangeland, and approximately 70% of the rangelands have been degraded by biotic and abiotic factors, as well as human activities. Our research focuses on the Khanbogd soum district of the southern Mongolian province of Umnugobi. The Khanbogd soum is occupied by the herds of Nomgon, Javkhlant, Bayn, and Gaviluud. With a total area of 15,150 km2, Khanbogd Soum District is located in the Gobi Desert and is primarily dry due to the low levels of precipitation. 38 monitoring plots in 2014 and 27 monitoring plots in 2015 were sampled from 19 winter camps of the four herder groups. Every 1m along each transect, the plant cover, litter, rocks, gravel, and bare ground were recorded. Inside each 1m2 plot, biomass and plant species were recorded and collected. There were similar grazing pressures at 1,000 m and 2,000 m from the winter camp center in the desert steppe, as shown by the fact that vegetation biomass, cover, and species richness did not differ with increasing distance from the center of the winter camps. In comparison to other plant functional groups, shrubs and grass had higher biomass levels of vegetation. Shrubs are among the plants that may tolerate periods of drought. The lower cover of other plant functional groups may have been caused by a lack of precipitation. ЦӨЛӨРХӨГ ХЭЭРИЙН УРГАМАЛЖИЛТАД МАЛ БЭЛЧЭЭРЛЭЛТИЙН ЭРЧМИЙН НӨЛӨӨ Монгол улс 1,500,116 км2 газар нутагтай ба нийт нутаг дэвсгэрийн 70 орчим хувийг бэлчээрийн талбай эзэлдэг төв Азийн хагас хуурай бүс нутаг юм. Уг бэлчээрийн нутаг нь эрт дээр үеэс малчдын амьдрал, ахуйг тэтгэж ирсэн бөгөөд таван хошуу малаас гадна зэрлэг амьтад бэлчээрлэх ач холбогдолтой газар юм. Гэсэн хэдий ч Монгол орны бэлчээрийн газар, нутаг нь амьд ба амьгүй хүчин зүйл болон хүний сөрөг үйл ажиллагааны нөлөөгөөр хамгийн их хүчтэй нөлөөлд өртсөн бүс нутаг бөгөөд бэлчээрийн 70 орчим хувь аль хэдийн их болон бага хэмжээгээр доройтсон байна. Тиймээс бид орон нутагт тулгамдаж буй бэлчээр ашиглалт, хамгаалалт ба сайжруулалтыг шийдвэрлэхэд суурь мэдээлэл болох бэлчээрийн мониторингийн тогтолцоо, чадвар чадамжийг бий болгох зорилгоор судалгааны ажил хийж гүйцэтгэлээ. Бидний хийсэн судалгааны газар нь Өмнөговь аймгийн Ханбогд сум ба Номгон, Жавхлант, Баян, Гавилууд багаас бүрдсэн 15150 км2 талбайтай. Байнгын хяналтын цэгийг (plot) өвөлжөөнөөс 1000 м, 2000 м-ийн алслалтайгаар, ижил зовхист, ойролцоо өндөрлөг болон ижил хөрстэй байх шалгуур хангасан цэгүүдийг сонгосон. Цэг тус бүрд 50м*50м трансектийн талбай байгуулан ургамлын бүрхэц, баялаг, биомасс, олон наст ургамлын суурь хоорондын зайн өгөгдөл цуглуулав. Цөлөрхөг хээрийн бэлчээрийн ургамлын бүрхэц, зүйлийн баялаг, болон олон наст ургамлын суурь хоорондын зай зэрэг үзүүлэлтүүдэд өвөлжөөнөөс бэлчээрийн градиентийн дагуу 1000 болон 2000 метрийн зайд ялгаа ажиглагдсангүй. Сөөгийн бүрхэц бусад ургамлын аж ахуйн бүлгүүдээс илүү бүрхэцтэй байв. Монгол улс 1,500,116 км2 газар нутагтай ба нийт нутаг дэвсгэрийн 70 орчим хувийг бэлчээрийн талбай эзэлдэг төв Азийн хагас хуурай бүс нутаг юм. Уг бэлчээрийн нутаг нь эрт дээр үеэс малчдын амьдрал, ахуйг тэтгэж ирсэн бөгөөд таван хошуу малаас гадна зэрлэг амьтад бэлчээрлэх ач холбогдолтой газар юм. Гэсэн хэдий ч Монгол орны бэлчээрийн газар, нутаг нь амьд ба амьгүй хүчин зүйл болон хүний сөрөг үйл ажиллагааны нөлөөгөөр хамгийн их хүчтэй нөлөөлд өртсөн бүс нутаг бөгөөд бэлчээрийн 70 орчим хувь аль хэдийн их болон бага хэмжээгээр доройтсон байна. Тиймээс бид орон нутагт тулгамдаж буй бэлчээр ашиглалт, хамгаалалт ба сайжруулалтыг шийдвэрлэхэд суурь мэдээлэл болох бэлчээрийн мониторингийн тогтолцоо, чадвар чадамжийг бий болгох зорилгоор судалгааны ажил хийж гүйцэтгэлээ. Бидний хийсэн судалгааны газар нь Өмнөговь аймгийн Ханбогд сум ба Номгон, Жавхлант, Баян, Гавилууд багаас бүрдсэн 15150 км2 талбайтай. Байнгын хяналтын цэгийг (plot) өвөлжөөнөөс 1000 м, 2000 м-ийн алслалтайгаар, ижил зовхист, ойролцоо өндөрлөг болон ижил хөрстэй байх шалгуур хангасан цэгүүдийг сонгосон. Цэг тус бүрд 50м*50м трансектийн талбай байгуулан ургамлын бүрхэц, баялаг, биомасс, олон наст ургамлын суурь хоорондын зайн өгөгдөл цуглуулав. Цөлөрхөг хээрийн бэлчээрийн ургамлын бүрхэц, зүйлийн баялаг, болон олон наст ургамлын суурь хоорондын зай зэрэг үзүүлэлтүүдэд өвөлжөөнөөс бэлчээрийн градиентийн дагуу 1000 болон 2000 метрийн зайд ялгаа ажиглагдсангүй. Сөөгийн бүрхэц бусад ургамлын аж ахуйн бүлгүүдээс илүү бүрхэцтэй байв. Түлхүүр үгс: ургамлын параметр, тэнцвэрт бус бүлгэмдэл, бэлчээрийн ургамалжил

Effects of Grazing Intensity on the Carbon, Nitrogen and Phosphorus Content, Stoichiometry and Storage of Plant Functional Groups in a Meadow Steppe

Studies on the impacts of grazing on carbon, nitrogen, and phosphorus stoichiometry and storage are crucial for better understanding the nutrient cycles of grasslands ecosystems. Using a controlled grazing experimental platform in a meadow steppe ecosystem, the effects of different stocking rates (0.00, 0.23, 0.34, 0.46, 0.69, and 0.92 AU ha−1) on the carbon, nitrogen, and phosphorus contents of plant functional groups were explored. The major results were: (1) The carbon content of Gramineae Barnhart was significantly reduced by grazing intensity (p &lt; 0.05), and the organic carbon content of Cyperaceae Rotundus was significantly higher than that of the other groups; the total nitrogen content of Cyperaceae and other groups and total phosphorus contents of Gramineae, Leguminosae Sp., Cyperaceae, and other groups all increased significantly with increasing grazing intensity (p &lt; 0.05). (2) The carbon, nitrogen, and phosphorus storage amounts of Gramineae, Leguminosae, and Ranunculaceae L. decreased significantly with increasing grazing intensity. Heavy grazing reduced the carbon, nitrogen, and phosphorus storage amounts of Cyperaceae and other groups, while the carbon, nitrogen, and phosphorus storage amounts of Compositae were the largest under moderate grazing. (3) The nitrogen content of each functional group was highly significantly negatively correlated with the C/N ratio, and the phosphorus content was highly significantly negatively correlated with the C/P ratio. Grazing and foraging affected the growth of the different functional groups, which in turn affected their carbon, nitrogen, and phosphorus content, stoichiometry, and storage. Moderate grazing improved the nutrient utilization efficiency of grassland and is beneficial for promoting sustainable grassland development.

Sown alfalfa pasture decreases grazing intensity while increasing soil carbon: Experimental observations and DNDC model predictions.

Grasslands are the most important land use in China and have experienced extensive degradation in the past few decades due to overgrazing. However, regionally viable solutions to grazing intensity alleviation remained elusive to date. Here, we evaluated the grazing intensity effects of sown alfalfa pastures in northern China using an experiment-modeling combined approach that involved six sites in field experiments and five provinces in DNDC modeling of sown alfalfa pasture's forage production and carbon sequestration potentials in marginal lands. Our results showed that the sown alfalfa pasture's dry-matter yield varied between 4.5 and 9.0 Mg ha-1 under rainfed and irrigated conditions, respectively, from 2025 to 2035. If half of the available marginal lands were mobilized for alfalfa forage production, these yield levels meant that livestock grazing intensity on natural grasslands may drop 8-13% under rainfed and 20-33% under irrigated conditions. Our results also showed that marginal land's soil organic carbon contents were systematically higher under sown alfalfa pasture than under fallow management by a big margin of 8.5 and 9.9 g kg-1 (i.e., +79 and +95%), under rainfed and irrigated conditions, respectively, during 2025-2035. Overall, these results demonstrated that sown alfalfa pasture on marginal lands represents an effective grassland conservation pathway over the short- to medium-term time horizon based on current technologies.

Relationship between Biomass and Biodiversity of Degraded Grassland in the Sanjiangyuan Region of Qinghai–Tibet Plateau

Understanding the mechanisms of diversity–productivity relationships is a central question in community ecology. Grazing is the main driving force affecting biodiversity, function, and stability of grassland ecosystems, and thus should play an important role in mediating diversity-productivity relationships. In this study, we examined the effect of grazing intensity on both aboveground biomass and biodiversity and explored the relationship between them in alpine meadow ecosystems in Sanjiangyuan, which is the source of the Yangtze, Yellow, and Lancang rivers. The results showed that the aboveground biomass and species richness decreased significantly due to multi-state succession in alpine meadows caused by long-term grazing, while the Shannon–Wiener index and Pielou evenness index decreased and then increased with increasing grazing intensity. The relationship between the aboveground biomass and biodiversity was U-shaped. Our results highlighted the opposite pattern of the diversity–productivity relationship under low and medium grazing intensity versus an extremely high grazing intensity; evenness contributed largely to this pattern. This study provided a new perspective on grassland management and the relationship between productivity and biodiversity. Attention should be paid to rational grazing to restore biodiversity and ecosystem functions and services in alpine meadows.

When disturbances favour species adapted to stressful soils: grazing may benefit soil specialists in gypsum plant communities

Background Herbivory and extreme soils are drivers of plant evolution. Adaptation to extreme soils often implies substrate-specific traits, and resistance to herbivory involves tolerance or avoidance mechanisms. However, little research has been done on the effect of grazing on plant communities rich in edaphic endemics growing on extreme soils. A widespread study case is gypsum drylands, where livestock grazing often prevails. Despite their limiting conditions, gypsum soils host a unique and highly specialised flora, identified as a conservation priority. Methods We evaluated the effect of different grazing intensities on the assembly of perennial plant communities growing on gypsum soils. We considered the contribution of species gypsum affinity and key functional traits of species such as traits related to gypsum specialisation (leaf S accumulation) or traits related to plant tolerance to herbivory such as leaf C and N concentrations. The effect of grazing intensity on plant community indices (i.e., richness, diversity, community weighted-means (CWM) and functional diversity (FD) indices for each trait) were modelled using Generalised Linear Mixed Models (GLMM). We analysed the relative contribution of interspecific trait variation and intraspecific trait variation (ITV) in shifts of community index values. Results Livestock grazing may benefit gypsum plant specialists during community assembly, as species with high gypsum affinity, and high leaf S contents, were more likely to assemble in the most grazed plots. Grazing also promoted species with traits related to herbivory tolerance, as species with a rapid-growth strategy (high leaf N, low leaf C) were promoted under high grazing conditions. Species that ultimately formed gypsum plant communities had sufficient functional variability among individuals to cope with different grazing intensities, as intraspecific variability was the main component of species assembly for CWM values. Conclusions The positive effects of grazing on plant communities in gypsum soils indicate that livestock may be a key tool for the conservation of these edaphic endemics.

Grazing Intensity Effects on Fire Ignition Risk and Spread in Sagebrush Steppe

Wildfire activity is accelerating on many rangelands worldwide, yet the potential for grazing to be used as a fire management tool remains largely unknown. Particularly, little is known about the influence of grazing on ignition and initial spread of fire, as well as how these vary by differences in grazing management. We investigated effects of grazing intensity (light, moderate, high) on fuel characteristics, fire ignition, and initial spread during the wildfire season in a native-dominated shrub steppe in eastern Oregon. We found that differences in grazing intensity have differential effects on fuel profiles (cover, height, moisture, biomass) with resulting impacts on fire behavior, but these relationships varied across study years. In particular, grazing had a stronger effect on ignition probability in drier years. Fire behavior in lightly grazed plots were similar to ungrazed plots, while moderate grazing was similar to high-intensity grazing. Results of this study highlight that grazing can be useful as a tool for wildfire management, and grazing at moderate and high intensities can reduce the probability of fire propagation in native-dominated sagebrush ecosystems. Further, the effects of grazing are context dependent and therefore may depend on specific objectives and environmental conditions.

Impacts of Short-Term Grazing Intensity on the Plant Diversity and Ecosystem Function of Alpine Steppe on the Qinghai-Tibetan Plateau.

Livestock grazing is the primary land use of grasslands worldwide. Grazing has been asserted to alter grassland ecosystem functions, such as productivity, nutrient cycling, and biodiversity conservation. However, few studies have focused on the impact of grazing intensity on the ecosystem multifunctionality (EMF) of alpine grasslands. We conducted a field experiment of manipulating sheep grazing intensity effects on alpine steppe by surveying plant community characteristics and ecosystem functions. Our results showed that plant community composition was altered with increasing grazing intensity, and the dominant species shifted from grasses and sedges to forbs. EMF was the highest under no grazing (CK) and the lowest under heavy grazing (HG), but there was insignificant difference between CK and HG. HG significantly decreased some indicators that reflected nutrient cycling functions, such as soil available nitrogen, plant leaf nitrogen (PN) and phosphorus content (PP). Furthermore, plant diversity had strong correlations with SOC, total nitrogen (TN), and PN. The results could provide scientific bases for biodiversity conservation and sustainable grazing management of alpine steppe.