Effects of crop abandonment and grazing exclusion on available soil water and other soil properties in a semi-arid Mongolian grassland
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Keywords:
Overgrazing
Desertification
Silt
Steppe
Abstract Degradation by overgrazing is common in many areas of the world and optimising grassland functions depends upon finding suitable grazing tactics. This four-year study on the northern China steppe investigated combinations of rest, moderate or heavy grazing pressure early in the summer growing season, then moderate or heavy grazing in the mid and late season. Results showed that moderate grazing pressure (~550 sheep equivalent (SE) grazing days ha −1 year −1 ) gave the optimal balance between maintaining a productive and diverse grassland, a profitable livestock system and greenhouse gas mitigation. Further analyses identified that more conservative stocking (~400 SE grazing days ha −1 year −1 ) maintained a desirable Leymus chinensis composition and achieved a higher live weight gain of sheep. Early summer rest best maintained a desirable grassland composition, but had few other benefits and reduced incomes. These findings demonstrate that reducing grazing pressure to half the current district stocking rates can deliver improved ecosystem services (lower greenhouse gases and improved grassland composition) while sustaining herder incomes.
Overgrazing
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Steppe
Grassland Degradation
Conservation grazing
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Fig. 1: Area of research, Inner Mongolia, P.R. China Background Increasing grazing pressure on native grassland in Inner Mongolia, P.R. China Overgrazing and degradation (more than 80% of the typical steppe ecosystem in Inner Mongolia is degraded). Grazing not only alters the ecological functionality of the grassland but also its value for livestock farming. Aim of the present study: Analysis of grazing-induced changes in productivity and herbage quality as well as its effect on animal performance.
Overgrazing
Inner mongolia
Grassland Degradation
Steppe
Conservation grazing
Grassland ecosystem
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Investigation on status of land desertification in northwestern Liaoning was conducted.The results regarding vegetation indicated that the average coverage for grass vegetation was 71.9%.Distribution of phreatophytes and mesophytes lessened and distribution of xerophytes expanded due to the effects of decrease of grassland area and drought in successive years.The degree of presence for 20 plants was highest,among which total times of presence and quantities for annual weeds in fields and sand grown plants were 1.8 and 2.7 times higher than perennial gramineae grass and other perennial plants respectively.Vegetation degradation and land desertification were serious in this region.Times of presence and quantities for abovementioned 20 plants in overgrazing and extreme grazing areas were much higher than that in moderate(no grazing included) and heavy grazing areas,which showed that over grazing and extremely grazing were key factors for vegetation degradation and land desertification.Distribution degrees of presence and richness for Cenchrus panciflorus attained 25.0% and 23.7% respectively,Cenchrus panciflorus has become the major harmful grass in the local grassland.
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Regional impacts assessment model is an indispensable tool for the study on environmental and economical change and the impacts on ecosystems. In this paper a regional impact assessment model AVIMia, which is an extended version of AVIM is designed. AVIMia is consists of two components: original AVIM (AtmosphereVegetation Interaction Model) and an impact assessment model. Over past 50 year the arid/semi-arid grassland of North China degraded severely due to the change in Climate and social economy. AVIMia is applied to assess the impacts of climatic changes and human activities on grassland in North China, based on historical data, and the different climatic and social scenarios for this region. For the assessment of grassland, specially, the following impact facts are taken into consideration: grazing, cultivation on grassland communities and soil attributes from plot to regional scale. The model is validated by observed data of Inner Mongolia semi-arid grassland. Both the data analysis and model assessment show that: Total aboveground NPP of Inner Mongolia grassland is 771.7*10 kg /yr. Edible aboveground biomass is 498.1*10 kg /yr. Typical steppe and meadow steppe dominate the production of this region. Total estimated livestock holding capacity is 45.51million sheep unit. The grassland is overgrazed more than 100% in Inner Mongolia. Overgrazing is one of the most important reasons inducing the widespread degradation and desertification.
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Grassland Degradation
Inner mongolia
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The results are got by field grazing experiment as follows: ① As the grazing density increases, vegetation coverage, height and forage production decrease obviously, of which degenerated grassland tends to recover under light grazing and the vegetation tends to deteriorate under overgrazing and the vegetation changes with climate change under moderate grazing; ② Perennial plants and palatable annual plants withdraw in succession from grassland and annual plants of poor quality dominate absolutely under overgrazing; Ratio of domination index between perennial plant and annual plant is 2∶3 under no grazing and light grazing; The change of domination plants is slow and domination index ratio between perennial plant and annual plant is 1:4 under moderate grazing; ③ Sandy grassland is very susceptible to disturbance in grazing, obvious change appears in the vegetation as soon as the grassland is grazed. The vegetation changes along individual direction under different grazing densities, and the speed relates to the grazing density, especially to the duration.
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Abstract Globally, livestock grazing is an important management factor influencing soil degradation, soil health and carbon (C) stocks of grassland ecosystems. However, the effects of grassland types, grazing intensity and grazing duration on C stocks are unclear across large geographic scales. To provide a more comprehensive assessment of how grazing drives ecosystem C stocks in grasslands, we compiled and analyzed data from 306 studies featuring four grassland types across China: desert steppes, typical steppes, meadow steppes and alpine steppes. Light grazing was the best management practice for desert steppes (< 2 sheep ha −1 ) and typical steppes (3 to 4 sheep ha −1 ), whereas medium grazing pressure was optimal for meadow steppes (5 to 6 sheep ha −1 ) and alpine steppes (7 to 8 sheep ha −1 ) leading to the highest ecosystem C stocks under grazing. Plant biomass (desert steppes) and soil C stocks (meadow steppes) increased under light or medium grazing, confirming the ‘ intermediate disturbance hypothesis ’. Heavy grazing decreased all C stocks regardless of grassland ecosystem types, approximately 1.4 Mg ha −1 per year for the whole ecosystem. The regrowth and regeneration of grasslands in response to grazing intensity (i.e., grazing optimization ) depended on grassland types and grazing duration. In conclusion, grassland grazing is a double-edged sword. On the one hand, proper management (light or medium grazing) can maintain and even increase C stocks above- and belowground, and increase the harvested livestock products from grasslands. On the other hand, human-induced overgrazing can lead to rapid degradation of vegetation and soils, resulting in significant carbon loss and requiring long-term recovery. Grazing regimes (i.e., intensity and duration applied) must consider specific grassland characteristics to ensure stable productivity rates and optimal impacts on ecosystem C stocks. Graphical Abstract
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Degradation by overgrazing is common in many areas of the world and optimising grassland functions depends upon finding suitable grazing tactics. This four-year study on the northern China steppe investigated combinations of rest, moderate or heavy grazing pressure early in the summer growing season, then moderate or heavy grazing in the mid and late season. Results showed that moderate grazing pressure (~550 sheep equivalent (SE) grazing days ha −1 year −1 ) gave the optimal balance between maintaining a productive and diverse grassland, a profitable livestock system, and greenhouse gas mitigation. Further analyses identified that more conservative stocking (~400 SE grazing days ha −1 year −1 ) maintained a desirable Leymus chinensis composition and achieved a higher live weight gain of sheep. Early summer rest best maintained a desirable grassland composition, but had few other benefits and reduced incomes. These findings demonstrate that reducing grazing pressure to half the current district stocking rates can deliver improved ecosystem services (lower greenhouse gases and improved grassland composition) while sustaining herder incomes.
Overgrazing
Steppe
Grazing pressure
Grassland Degradation
Grassland ecosystem
Conservation grazing
Stocking rate
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Shrubland
Desert (philosophy)
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Desertification
Overgrazing
Steppe
Aridity index
Albedo (alchemy)
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Abstract. The degradation of natural resources in arid and semi-arid areas was highlighted dramatically during this century due to population growth and transformation of land use systems. The Algerian steppe has undergone a regression over the past decade due to drought cycle, the extension of areas cultivated in marginal lands, population growth and overgrazing. These phenomena have led to different degradation processes, such as the destruction of vegetation, soil erosion, and deterioration of the physical environment. In this study, the work is mainly based on the criteria for classification and identification of physical parameters for spatial analysis, and multi-sources factors to determine the vulnerability of steppe formations and their impact on desertification. To do this, we used satellite data Alsat-1 (2009) IRS (2009) and LANDSAT TM (2001). These cross-sectional data with exogenous information could monitor the impact of the semi arid ecological diversity of steppe formations. A hierarchical process including the supervised image classification was used to characterize the main steppe formations. An analysis of the vulnerability of plant was conducted to assign weights and identify areas most susceptible to desertification. Vegetation indices combined with classification are used to characterize the forest and steppe formations to determine changes in land use. The results of this present study provide maps of different components of the steppe, formation that could assist in highlighting the magnitude of the degradation pathways, which affects the steppe environment, allowing an analysis of the process of desertification in the region.
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