| Alpine meadow is one of the most widely distributed alpine vegetation types in China and an important water-conserving area in the upper reaches of the Yellow River Basin,which play an important role in environmental protection and maintenance of species diversity.In recent years,alpine meadow degradation has become common and soil erosion has been serious in some areas due to unsuitable use of alpine meadow.Soil erosion was mainly directly related to soil texture,above-ground vegetation species composition,rainfall and grazing management.These problems were further accentuated by the fragile alpine grassland ecosystem in the Qilian Mountains region.Therefore,the maintenance of water retention and soil consolidation effects are important scientific issues for their management in alpine meadows.However,there is a relative lack of research on water retention and soil consolidation in alpine meadow under different land use types and slope positions.In view of this,this study was conducted to investigate the permeability,water-holding,erosion resistance and erosion resistance of alpine meadow soils from different land use types and slope positons and angles under artificially simulated rainfall in Tianzhu alpine meadow in the eastern part of Qilian Mountains.We aimed to determine the relationship between grassland vegetation status and soil erosion,the capacity of water retention and soil consolidation and its response to different grassland use types,and to reveal the driving mechanisms of changes in the capacity of water retention and soil consolidation.the main results were as follows:(1)Above-ground biomass was the highest and below-ground biomass was the lowest in artificial grassland with 30 years of cultivation;above-ground biomass was the lowest in grazing roads and below-ground biomass was the highest in grazing grassland.Soil all-valent N,P,and K content,total soil porosity,and>2 mm water-stable aggregates were the highest in fenced pastures and the lowest in artificial pastures.Soil all-valent N,P,and K content was the highest in the middle of the slope and the lowest in the foot of the slope;aboveground biomass was the highest at the bottom of the slope and the lowest at the top of the slope;belowground biomass was highest at the top of the slope and lowest at the foot of the slope.(2)The stable infiltration rate and cumulative infiltration volume of the soil were ranked as fenced grassland>grazing grassland>grazing path>artificial grassland.Soil infiltration rate tended to increase from the top to the bottom of the slope,and decreased with increasing soil depth;the factors affecting soil infiltration rate were ranked as porosity>bulk density>particle composition>water-stable aggregates.The organic matter,total potassium and total nitrogen contents in the soil were basically consistent with the changes of infiltration rate.(3)The soil water holding capacity increased with the increase of powder content and decreased with the increase of clay content,and showed a significant positive correlation with the total porosity,capillary porosity and non-capillary porosity.The soil water holding capacity in the field ranked as fenced grassland>grazing grassland>grazing path>artificial grassland,and the soil water holding capacity was the largest at the bottom of the slope and the smallest at the foot of the slope.(4)Soil anti-scourability was found to be ranked as grazing grassland>grazing path>fenced grassland>artificial grassland,with the strongest at 5°and the weakest at 15°,and 0-20 cm>20-40 cm.Soil organic matter,all-valent phosphorus,nitrogen and potassium were significantly and positively correlated.The results showed that flushing decreased significantly soil organic matter,total nitrogen and total phosphorus in different land use types,with the highest decrease in artificial grassland;the flushing resistance index was the highest in the middle of the slope and the lowest at the foot of the slope,and increased with the flushing time.(5)Soil anti-erodibility was the strongest for fenced grassland and the weakest for artificial grassland,and gradually weakened with increasing soil depth.The runoff volume,runoff coefficient and sand production decreased and then increased from the top to the foot of the slope,with the smallest in the middle of the slope and the largest at the top of the slope;In contrast,the water content increased and then decreased from the top to the foot of the slope,with the highest in the middle of the slope and the lowest at the top of the slope.Our results showed that the soil and water conservation effect was the best in the middle of the slope.(6)The highest ecological service value of soil conservation was 54.88yuan·m-2·a-1for fenced grassland,and the lowest was 37.57 yuan·m-2·a-1for artificial grassland.Among different slope positions,the highest ecological service value of soil conservation was 83.77 yuan·m-2·a-1under the slope.In summary,based on the different grassland use types and slope positions,our resuts indicated that the middle and lower slopes in fenced grassland have the best effects of soil and water conservation and the highest ecological service value.Our foundings can provide a scientific basis for protection,utilization and management of alpine meadow. |
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