A Study On Limiting Factors For Vegetation Restoration In The Bald Patch Damaged By Plateau Pika And Evaluation Of Vegetation Restoration Measures In Alpine Meadow

The bald patch caused by plateau pika in the alpine rangeland is that the plateau pika push soils during it dig holes and the soil cover plants to death,which form the secondary bare land with low plant cover or no plant cover under the livestock trampling and wind-water erosion.Previous studies have focused on the functional group structure,root-soil complex characteristics and patch distribution characteristics in the bald patch.However,there are few reports on recovery limiting factors of plant restoration and the evaluation of targeted restoration measures in bald patch.In this study,the typical bald patches caused by plateau pika in alpine meadow Gannan Prefecture in Gansu Province were selected and conducted a series of studies as follow,1.The patches were clustered and divided into six gradient areas(I,II,III,IV,V and VI)according to the diameter of bald patches,the grassland without bald patch was regarded as the control(CK).The effects of soil seed bank,soil permeability,soil total porosity,soil maximum water holding capacity,capillary water holding capacity,soil minimum water holding capacity,soil temperature and humidity,soil total nitrogen,total phosphorus and total potassium on plant community composition in the patch with different gradient areas were analyzed.(2)Based on the results of study(1),shallow plowing,shallow plowing with coconut fiber,shallow plowing with coconut fiber and peat and spraying different concentrations of wetting agents(concentrations of 2000ml/m~2,4000 ml/m~2,6000 ml/m~2 and 9000 ml/m~2,respectively)were used to investigate the soil physical and chemical properties and plant community characteristics of bare patches under different measures.Redundancy analysis,correlation analysis and grey correlation analysis were used to explore the effects of restoration measures on plant communities.The main results are as follows:1.Soil organic matter and soil porosity were the main limiting factors affecting vegetation restoration in bald patches.The soil seeds in different areas of bald spots were mainly distributed in 0～2 cm soil layer,and the seed density of gradient II was the highest,which was 6724.12 grains/m~2.The maximum water holding capacity in the soil of bare patch with different areas was lower than that of CK(P<0.05).Partial redundancy analysis showed that soil organic matter,soil temperature,capillary porosity and average infiltration rate significantly affected plant height,coverage and biomass(P<0.05),and soil organic matter had the most significant effect on plant height.2.The soil organic matter in the 0～10 cm surface layer under the restoration measures with shallow ploughing,shallow ploughing mixed coconut bran,and shallow ploughing mixed coconut bran and peat treatments was greater than that the control(P<0.05).Compared with the grassland without bald patch,the restoration measure with shallow ploughing mixed coconut bran significantly increased the maximum water holding capacity,total porosity,and N,P,organic matter and C/P in the 0～10 cm surface soil(P<0.05).Partial redundancy analysis showed that soil organic matter(OM),soil capillary water holding capacity(Cc)and total porosity(Tp)had a significant net effect on the variance interpretation of plant community characteristics(P<0.05).Grey correlation analysis showed that the recovery effect of plant community was the best under shallow plowing with coconut fiber treatment.3.The measures of shallow plowing,shallow plowing mixed coconut coir,shallow plowing mixed coconut coir mixed peat can restore the vegetation and soil in the bare patch,the combination of shallow plowing and coconut coir has the best effect of vegetation restoration.The aboveground biomass of plants under all restoration measures with shallow ploughing,shallow ploughing mixed coconut fiber,and shallow ploughing mixed coconut coir and peat treatments was significantly higher than that of the grassland without bald patch(P<0.05).Among them,the plant coverage,height and biomass under the restoration measures with shallow ploughing mixing coconut were significantly higher than those of the grassland without bald patch(P<0.05),and the plant height,species number and biomass increased during the recovery period(2019～2021).4.Spraying wetting agent on bald patch can improve soil water holding capacity and increase plant species richness,and the concentration of 4000ml/m~2 wetting agent is the best for the plant growth.After spraying different concentrations of wetting agents,the maximum water holding capacity(Mc),capillary porosity(Cp)and total porosity(Tp)of soil were higher than those of unsprayed bald patch(P<0.05).In the spraying area with wetting agent concentration of 4000 ml/m~2,the richness of perennial forbs was significantly higher than that of other concentration treatments,and higher than that of unsprayed bald spots(P<0.05).Soil maximum water holding capacity(Mc)and capillary water holding capacity(Cc)were significantly correlated with plant height(H)(P<0.05).5.Under the different restoration measures,the cover,height,biomass and the plant species number increased while the number of effective holes of plateau pika showed a decreasing trend during three years.