| In the context of global change,the growth of vegetation in grassland ecosystems in semi-arid areas of my country is limited by water.Groundwater is an important source of soil moisture.The depth of groundwater level affects the material circulation and energy flow of the soil-vegetation system.To this end,using field control experiments,a control experiment was set up in 2017,with three groundwater depth gradients(0.5 m,1.0 m,2.0 m)and two plant communities(Pennisetum centrasiaticum and Artemisia halodendron)a total of 6 treatments.In 2017-2019,soil samples were collected in layers according to soil depths of 0-10 cm,10-20 cm,and20-40 cm;in 2020,three different groundwater depth gradients were respectively 0-10 cm,10-20 cm,and 20-40 cm.Three different soil depths of 40 cm and 0-20 cm,20-40 cm,40-60 cm,60-80 cm,and 0-20 cm,20-40 cm,40-80 cm,80-100 cm,and 100-120 cm are divided into layers for sampling.Through the determination of soil organic carbon,total nitrogen,total phosphorus and other soil nutrients,glucosidase,and other soil enzyme activities,soil microbial biomass carbon and nitrogen,and plant root biomass and other biological indicators Analyze and study the relationship between soil nutrients,soil enzyme activities,soil microbial biomass and vegetation roots in Horqin sandy grassland under different groundwater depth treatments.Reveal the response mechanism of the soil environment and plant roots to the depth of the groundwater table,and provide a theoretical basis for the discussion of global changes and carbon storage prediction.The main research is as follows:(1)After three different groundwater depth treatments,the average value of soil nutrients in the 0-40 cm soil surface layer from 2017 to 2020 will change to varying degrees in the inter-annual changes.Pennisetum centrasiaticum community,the soil p H,total nitrogen and total phosphorus content gradually increase with the inter-annual changes,and the soil organic carbon content gradually decreases.In the Artemisia halodendron community,soil organic carbon and total nitrogen content gradually decreased with interannual changes,soil p H showed an upward trend year by year,and total phosphorus content was not obvious in interannual changes.In 2020,the average soil organic carbon content of the Pennisetum centrasiaticum community will decrease with the depth of the groundwater table and the depth of the soil.The average content of total nitrogen and total phosphorus will gradually decrease with the depth of the groundwater table;the soil of the Artemisia halodendron community The average content of p H,soil organic carbon,total nitrogen and total phosphorus decreased with the depth of groundwater level.(2)In the treatment of different groundwater depths,the soil enzyme activities of the 0-20 cm and 20-40 cm will reach a significant difference in soil enzyme activities in the communities of Pennisetum centrasiaticum and Artemisia halodendron(P<0.05).The six enzyme activities of the 0-20 cm in semi-arid soil It is higher than the 20-40 cm in the process of chemical transformation.It explains that aridification can aggravate the decomposition of organic carbon in the surface soil of grassland,and also shows that arid environment is beneficial to increase soil enzyme activity.(3)In the 20-40 cm soil layer in 2020,the mean values of soil microbial biomass carbon were highest in the Pennisetum centrasiaticum and Artemisia halodendron communities,and the soil microbial biomass carbon content in the Pennisetum centrasiaticum community and the soil microbial biomass nitrogen content in the Artemisia halodendron community showed significant decreasing and increasing patterns in the 0-20 cm soil layer,respectively.(4)In 2020,the total root biomass of Pennisetum centrasiaticum decreased with deeper water table burial in all 0-40 cm soil layers.The total root biomass,fine root biomass and coarse root biomass of Artemisia halodendron decreased with the deepening of the water table.The coarse root biomass of both vegetation species was only present above 100 cm soil layer in the experiment.(5)The results showed that the content of soil organic carbon,total nitrogen and total phosphorus increased significantly with the increase of total root biomass,with a significant positive correlation;soil p H decreased with the increase of total root biomass,showing a negative correlation.From the correlation analysis between the root systems of the two vegetations and soil enzyme activities.In the treatment of 1.0m of groundwater depth,the L-leucine aminopeptidase,catalase and polyphenol oxidase of the Pennisetum centrasiaticum community had a significant negative correlation with the total root biomass(P<0.05).Oxidase has a significant negative correlation with fine root biomass,and L-leucine aminopeptidase has a significant negative correlation with thick root biomass.In the Artemisia halodendron community,L-leucine aminopeptidase was significantly negatively correlated with fine root biomass,and polyphenol oxidase was significantly negatively correlated with total root biomass and fine root biomass(P<0.05)and extremely Significantly negative correlation(P<0.01).In the treatment of the groundwater depth of 2.0 m,only the polyphenol oxidase in the Pennisetum centrasiaticum community has a significant correlation with total root biomass.In the Artemisia halodendron community,β-N-acetylglucosaminidase and polyphenol oxidase have significant positive correlation and extremely significant positive correlation with total root biomass,respectively;acid phosphatase,β-glucosidase,β-N-Acetyl-glucosaminease and polyphenol oxidase were significantly positively correlated and extremely significantly positively correlated with fine root biomass.The total root biomass and fine root biomass of the Pennisetum centrasiaticum community were significantly negatively correlated with soil microbial biomass carbon and soil microbial biomass nitrogen(P<0.01);coarse root biomass and soil microbial biomass carbon were extremely significant There was a significant negative correlation with soil microbial biomass nitrogen(P<0.05);the total root biomass of the Artemisia halodendron community was significantly negatively correlated with soil microbial biomass carbon.Based on the principal component analysis of the relationship between the root system of vegetation and soil nutrients,soil enzyme activity and soil microbial biomass at the depth of groundwater table,the root biomass are all positively correlated with soil organic carbon,total nitrogen and total phosphorus.In addition,there is a positive correlation between the root biomass of Artemisia halodendron and soil p H and soil microbial biomass nitrogen,and the root biomass of Artemisia halodendron has a negative correlation with soil p H and soil microbial biomass nitrogen.In the treatment of 1.0 m groundwater depth,the soil catalase and soil p H of the Pennisetum centrasiaticum community were negatively correlated with root biomass;the soil catalase of the Artemisia halodendron community was negatively correlated with soil p H,and the root biomass There is a positive correlation. |
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