The Decomposition Characteristics Of Desert Grassland Litter Under Different Utilization Modes And Its Mechanism Of Action On Soil

Inner Mongolia desert grassland has a special geographical location.It is a fragile grassland ecosystem in transition from grassland to desert,and an important environmental ecological barrier in China.However,with the increase of human grazing activities,the desert grassland is faced with environmental problems such as plant community degradation and land desertification.The desert grassland covers a vast area,and it is difficult to take complex control measures to restore the desert grassland.It is an important guarantee for the sustainable development of desert grassland to adopt convenient and quick measures such as enclosure and mowing,and to use local resources to improve the ecological environment.In this study,the methods of field observation,decomposition test and chemical test in the laboratory were used to study the effects of utilization modes on plant community and soil in desert grassland,the decomposition characteristics of common litter in desert grassland under different utilization modes,the effects of litter decomposition on the physical and chemical properties of soil and soil bacterial communities,so as to screening more appropriate management and protection measures for desert grassland,and combining the role of litter decomposition on grassland soil,Provide a restoration plan for desert grassland.The result shows that:1.The effects of utilization modes on grassland plant communities are shown as follows: the height of the constructive species,coverage,and litter thickness of plant communities are enclosed and mowing area>grazing area throughout the plant growth period.The effects of utilization modes on grassland soil are as follows: the contents of soil organic carbon(SOC),alkali hydrolyzable nitrogen(AN),total nitrogen(TN),available phosphorus(AP),total phosphorus(TP)and total potassium(TK)are higher in the mowing area and enclosure area than in the grazing area,and the content of available potassium(AK)in the mowing and enclosure areas have little difference and is significantly higher 12.62-13.12mg/kg and 98.26-105.55mg/kg than that in the grazing area(P<0.05).The abundance of 67-14 family in the soil is relatively high,accounting for7.85% in the enclosed area,2.03% and 1.41% higher than that in the mowing area and grazing area.At the same soil depth,the bacterial diversity in enclosure and mowing areas is higher than that in grazing area.In the same utilization mode,the bacterial diversity at the surface and at the depth of 5cm is higher than that at the depth of 15 cm.2.The decomposition rate of litter is affected by the quality of its own substrate,and litter with high carbon(C),cellulose and lignin content is not easy to decompose.The substrate quality of Leymus chinensis litter and Stipa capillata litter is basically the same,showing that the C content is 439.13-449.26g/kg,the cellulose content is 53.41%-57.06%,and the lignin content is 19.34%-22.69%.The contents of C,cellulose and lignin in Artemisia frigida litter are about 87%,82% and 60% of them,and the content of litter C,cellulose and lignin in mixed(Leymus chinensis+Stipa capillata+Artemisia frigida)litter is about 92%,85% and 81% of them.Therefore,the decomposition rate of litter is as follows:Artemisia frigida litter>mixed litter>Leymus chinensis litter and Stipa capillata litter.3.In the process of litter decomposition,the accumulation of soil nutrients is related to the decomposition rate of litter.During the 120-180 days,the decomposition rate of Stipa capillata litter on the surface in the grazing area is fast,resulting in the increase of the contents of AP,TP,AK and TK in the soil by 1.17mg/kg,0.39g/kg,105.28mg/kg and2.3g/kg,respectively.During the 180-240 days,the decomposition rate of Artemisia frigida litter in the enclosure area is fast,which leads to the increase of the content of AP and TP in the surface soil by 0.78mg/kg and 0.04g/kg,the increase of AN,TN,AP,TP and SOC in the soil at a depth of 5cm,and the increase of AK and TK content in the soil at a depth of15 cm by 23.79mg/kg and 0.26g/kg.During the 180-240 days,the decomposition rate of Artemisia frigida litter in the mowing area is faster,resulting in an increase of 13.47g/kg of SOC at the depth of 5cm,and an increase of 7.66mg/kg and 1.3g/kg of AK and TK at the depth of 15 cm.During the 180-240 days,the decomposition rate of mixed litter is faster at the depth of 15 cm in the mowing area and enclosure area,which leads to the increase of soil AN and TN content.During the 240-300 days,the decomposition rate of Artemisia frigida litter at 15 cm depth in grazing area is fast,which leads to the increase of the content of AP,TP,AK and TK in soil by 1.47mg/kg,0.09g/kg,9mg/kg and 0.68g/kg.4.The decomposition of litter can improve the species richness and community diversity of soil bacteria.At the genus level,the dominant genus of bacteria in the mowing area are Rubrobacter,norank＿f＿67-14 and RB41.The dominant genus in the enclosed area are Rubrobacter,norank＿f＿67-14 and RB41.The dominant genus in the grazing area are Rubrobacter,norank＿f＿67-14 and norank＿o＿Gaiellales.The decomposition of litter increases the number of soil bacterial species by 32.94%-50.17%.Under each utilization mode,the number of soil bacterial species on the surface is obviously different from that at the depth of 5cm and 15 cm.