| A full understanding of the ecosystem of the alpine grassland in the lake area of the northern Tibet Plateau is conducive to regional ecological protection and construction,in order to explore the impact of environmental changes on the soil of the alpine grassland.In this paper,the method of field investigation and quantitative analysis is used to study the soil in the lakeside zone of Zhari Namco.Start with the spatial distribution of soil pH,organic matter content,and soil salinity in the alpine grassland ecosystem.From the main environmental changes in the lake area,namely the impact of lake water fluctuations on the soil,the two spatial factors of lake level and lake shore distance are used to show the dynamic changes in time and combined with its inherent influence mechanism: salt input caused by lake water fluctuations,The difference in the accumulation process of evaporation in the soil surface caused by elevation difference and topography,and the difference in soil organic matter caused by surface vegetation are analyzed.The main conclusions of this paper are as follows:(1)The fluctuation of lake water,strong alkaline lake water and groundwater entering the soil,has a greater impact on the soil pH in areas with small elevation differences from the lake surface and close distances from the lake shore.The average pH value of soil pH in the near lakeside zone was 8.27,the average pH value in the middle lakeside zone was 7.12,and the average pH value in the far lakeside zone was7.38.The soil in the lakeside zone is alkaline or weakly alkaline as a whole,and the pH value of the soil that is farther away has an obvious trend of falling first and then falling slowly and then rising slowly.The soil pH value of the low altitude group was 8.72,the soil pH value of the middle altitude group was 7.79,and the soil pH value of the high altitude group was 6.74.The pH value decreases with the increase in altitude.For every10 m increase in altitude,the pH value decreases by an average of 0.149,and the soil changes from alkaline to acidic.(2)As the height difference from the lake surface and the distance from the lake bank increase,the possibility of being submerged by lake water decreases,the vegetation coverage increases,and the species diversity increases.The continuous replenishment of plant litter increases the soil organic matter content.The average content of organic matter near the lakeside is 23.37g/kg,the average content of organic matter in the middle lakeside area is 32.72g/kg,and the average content of organic matter in the far lakeside area is 38.78g/kg.As the distance increases,the content of soil organic matter gradually increases,and there is an obvious trend of increasing first and then slowly.The content of soil organic matter in the low altitude group was 21.05g/kg,the content of soil organic matter in the middle altitude group was 19.07g/kg,and the content of soil organic matter in the high altitude group was 43.64g/kg.Overall,the soil organic matter content was low.The soil organic matter in the coastal zone of Zhari Namco Lake with a height difference of more than 40 m is greater than 40 g/kg.The greater the height from the lake surface,the organic matter content of the soil increased,and the average soil organic matter content increased by 5.801 g/kg for every 10 m increase in altitude.(3)The high-salinity lake water has flooded the soil in the area close to the lake bank with small height difference from the lake surface for a long time.Through the long-term lake inundation and retreat,the lake water rises and floods the land.After the lake retreats,the water in the soil evaporates due to the local arid climate,which brings salt from the ground to the surface and remains in the soil.As a result,the accumulation of minerals in the soil continues to increase and the salt content rises.The soil in the near lakeside zone and the area with a slightly lower lake level is weakly saline soil.The average value of total soluble salt in the near lakeside zone is the highest value of3282.66mg/kg,the average value of total soluble salt in the middle lakeside zone is2815.48mg/kg,and the average value of total soluble salt in the far lakeside zone is closer to that of the middle lakeside zone at 2779.94mg/kg.The coefficient of variation of total soluble soil salt content is the largest in the near lakeside zone,the lowest in the middle lakeside zone,and slightly rises to the far lakeside zone.The soil salt content in the low altitude group was 3306.27 mg/kg,the middle altitude group was 2808.36mg/kg,and the high altitude group was 2929.89 mg/kg.The soil salt content is relatively high in areas with relatively low altitudes,and the total soluble soil salt is reduced by 61.878 mg/kg for every 10 m increase in altitude from the lake surface.The sampling points with soil salt content greater than 3500 mg/kg are all within 40 meters above the lake surface,and the soil salt content is relatively low at about 40-100 meters above the lake surface.(4)The relationship between soil salt cations and total soluble soil salt changes consistent with the distance between the lake shore and the height of the lake.The average total content of cations in the near lakeside soil is 3105.98mg/kg,the average total content of the four major cations in the middle lakefront area is 2737.24mg/kg,and the average total content of the four major cations in the far lakefront area is2685.65mg/kg.The total content of the four major cations of soil salinity decreased stepwise with the lakeside zone from near to far,but the coefficient of variation was the largest in the near lakeside zone,the lowest in the middle lakeside zone,and rose slightly to the far lakeside zone.The cation content of soil salt in the low altitude group was 3111.45 mg/kg,the content of soil salt cation in the middle altitude group was2715.77 mg/kg,and the content of soil salt cation in the high altitude group was2841.74 mg/kg.,The low-altitude group has the highest soil salt cation content,and the middle-altitude group has lower soil salt cations overall.(5)The average total anion content of soil salt in the near lakeside zone is176.68mg/kg,the average total anion content in the middle lakeside zone is 78.24mg/kg,and the average total content of the four major anions in the far lakeside zone is94.29mg/kg.The change of total soil salt anion content is the same as the change of soil salt cation.As the lakeside zone decreases stepwise from near to far,the coefficient of variation is the largest in the near lakeside zone,the lowest in the middle lakeside zone,and slightly rises to the far lakeside zone.The total soil salt anion content generally decreases with the lakeside zone from near to far.The soil salt anion content of the low altitude group was 194.82mg/kg,the soil organic matter content of the middle altitude group was 92.59mg/kg,and the soil organic matter content of the high altitude group was 88.15mg/kg.The low-altitude group has the highest content,and the middle-altitude group has a lower overall content.The soil salt anion content is relatively high with a small height difference from the lake surface,and most of the sampling points with a soil salt anion content greater than 20 mg/kg are below 40 meters from the lake surface. |
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