Seasonal Variation Of Soil Of Different Grassland Communities In Saline Desert Area Of Gansu Province

Soil salinization has become a worldwide resource issue and environmental problems.The world area of saline-alkali land is about 9.55 × 10⁸ hm²,accounting for7.26% of the earth's land area.The area of saline-alkali land in China is about 9913 × 10⁴hm²,which is mainly distributed in the northeast,north and northwest inland areas and the coastal areas north of the Yangtze River.Therefore,how to rationally develop and utilize this land resource with great potential and economic value is of great significance.In recent years,studies on species succession have shown that the improvement of soil conditions by pioneer species is more conducive to the coexistence of species and the increase of biodiversity.Then whether there is interaction between plants and soils,and whether these interactions play a key role in the further development of the community.In this study,the main plant groups?Haloxylon ammodendron,Nitraria tangutorum,Tartarum chinensis and Alhagi spiglia?in the saline grassland of Hexi Corridor in Gansu had been researched,we studied the soil physical and chemical properties,soil nutrient compositions and soil micrological traits of different plant communities in different seasons.The main results are as follows:?1?The soil salts of the Haloxylon ammodendron community showed a "T" type distribution,and the salinity mainly accumulated in 0-60 cm soil layer,and in July the surface soil salinity accumulated significantly.The seasonal variation of salt and Cl^-,p H and HCO₃^-,SO₄^2-,K⁺ and Na⁺,Mg²⁺ and Ca²⁺ in Haloxylon ammodendron community was similar.The number of soil microbes is: bacteria> actinomycetes> fungi.In the Haloxylon ammodendron community,there was a significant positive correlation between fungi and actinomycetes,and there was a significant positive correlation between bacteria and dehydrogenase.There was a significant negative correlation between fungi and urease,and there was a significant negative correlation between actinomycetes and urease relationship.There was a significant positive correlation between fungi and available copper,and there was a significant negative correlation between respiration rate and organic matter.?2?The soil wanter content of Nitraria tangutorum community increased with the increase of soil depth,and the soil moisture in 0-5cm soil layer and 5-10 cm soil layer increased with the seasons.The accumulation of salinity in the surface and seasonal variation of soil salts were very obvious,especially in July,and the amount of salt was up to 40.7% in 0-20 cm soil layer.Soil respiration rate showed a decreasing trend with the change of seasons.The number of soil microbes is: bacteria> actinomycetes> fungi.There was a significant negative correlation between soil bulk density and soil moisture in the Nitraria tangutoracae community,and there was a significant positive correlation between fungi and urease.There was a significant negative correlation between soil bulk density and available phosphorus.There was a significant positive correlation between soil moisture and available phosphorus.There was a significantly positive correlation between urease and available copper,and there was a significant positive correlation between dehydrogenase and available potassium.There was a significant positive correlation between fungi and available copper,and the content of available copper was directly affected by the number of fungi.?3?The soil water content of the Tartarum chinensis community increased with the depth of the soil,and the soil moisture in the 0-5cm soil layer and the 5-10 cm soil layer showed a decreasing trend with the seasons.Soil microbiological quantity: Bacteria>Actinomycetes> Fungi.The seasonal changes of soil salinity and Cl^-,p H and HCO₃^-,SO₄^2-,K⁺and Na⁺,Mg²⁺and Ca²⁺were consistent.The amount of salt,Cl^-,HCO₃^-,SO₄^2-,K⁺ and Na⁺ was accumulated visibly in surface,and the amount of Mg²⁺ and Ca²⁺ was accumulated obviously in the bottom.There was a significant positive correlation between bacteria and dehydrogenase,and there was a significantly positive correlation between bacteria and urease.There was a significantly positive correlation between urease and dehydrogenase,and the bulk density was significantly positively correlated with available nitrogen.And there was a significantly positive correlation between respiration rate and available potassium.?4?The soil bulk density of the Alhagi spiglia community showed a decreasing trend with the change of the seasons in 0-5cm soil layer and 5-10 cm soil layer.Theamount of salt,Cl^-,HCO₃^-,SO₄^2-,K⁺ and Na⁺ was accumulated obviously in surface,and the amount of Mg²⁺and Ca²⁺was accumulated in bottom.Soil microbes are mainly bacteria,followed by actinomycetes,fungi content is minimal.There was a significant positive correlation between respiration rate and alkaline phosphatase.There was a significant negative correlation between fungi and urease,dehydrogenase and organic matter,and positively with available manganese and available copper.The urease was positively correlated with dehydrogenase and organic matter.There was a significant positive correlation between dehydrogenase and organic matter.The available N was positively correlated with available iron,and the availability of trace elements in soil is affected by soil p H and organic matter.