| Based on their vegetation characteristics,study area distribution and grassland utilization condition,5 degraded alpine wetland plots were selected to investigate grassland degradation processes in Huahu Scenic Area,Zoige County,in Southwest China.Burrow densities of pikas,vegetation composition,soil properties were measured and analysis in July and October.The main results were as follows:1.Small herbivores species,amounts and distribution in Huahu degraded wetlandPlateau pikas(Ochotona curzoniae)were dominant species,and there were few plateau zokor(Myospalax bayieyi)and marmota himalayana(Marmota himalayana)existing in Huahu wetland,Zoige.The active burrows densities of five survey plots were as follows:76 burrows per 1 hm2 in plot V which was near the inner wetland,644 burrows per 1 hm2 in plot Ⅳ which was near the gate inside wetland,1296 burrows per 1 hm2 in plot III which was in sunny slope outside Huahu Scenic Ares,180 burrows per 1 hm2 in plot Ⅱ which was in shady slope outside Huahu Scenery,968 burrows per 1 hm2 in plot I which was in top hill outside Huahu scenery spot,respectively.Wholey the amounts of active burrows were the largest at sunny slope mountain,while those of active burrows were the least at near the inner wetland.Further,there were significant differences in each two plots.The densities rodents of slope area were larger than flat area.A few plateau zokor were found at shady slope and near the wetland,and marmota himalayana just were distributed over shady slope.2.Vegetation composition and aboveground biomass in Huahu degraded wetlandThere were 29,31,33,32,32 kinds of species plants from plot Ⅴ to plot Ⅰ,respectively,and the dominant species were as follows:Potentilla anserina,Elymus nutans.and Poa annua were in plot Ⅴ,Ranunculus tanguticus,Lancea tibetica,and Elymus nutans were in plot Ⅳ,Anaphalis lacteal,Ranunculus tanguticus,and Gentiana macrophy were in plot III,Medicago archiducis,Geranium wilfordii,and Kobresia pygmaea were in plot Ⅱ Kobresia humilis,Ligularia virgaurea,and Leontopodium nanum were in plot Ⅰ.Further,the aboveground biomass(DM)ranged from 117.1 to 303.2 g/m2.Aboveground biomass were the largest in plot V,while aboveground biomass were the least in plot I.3.Soil physical-chemical properties in Huahu degraded wetlandIn July,soil water percentage ranged from 34.22%to 48.82%in 0—10 cm soil layer.Soil water percentage were largest in plot Ⅳ,and those were the least in plot Ⅴ.Soil pH were 6.17—6.47,and soil bulk density were 0.85—1.08 g/cm3.Soil bulk density were the largest in plot Ⅲ,while those were least in plot IV.What’s more,soil bulk density increased with the increase of soil depth.Soil carbon(C),nitrogen(N)content were 3.7%—4.9%and 0.38%—0.56%,respectively,but there were no differences among the plots.Soil C content were the largest in plot Ⅳ,and those were the least in plot Ⅴ.Soil N content were the largest in plot Ⅰ,and those were the least in plot Ⅴ.In addition,soil C,N content in 0—10 cm soil layer accounted for 33.8%,33.2%in total soil layers.Soil phosphorus(P)content were 0.062%—0.101%,and soil P content increased significantly from the slope area to the plain area.And soil P content in 0—10 cm soil layer accounted for 26.7%in other soil layers.Soil available nitrogen(AN)content were 54.13—68.94 mg/kg,those were the largest in plot IV,and those were the least in plot Ⅴ.Carbon storage in 0—30 cm soil layer were 11.10—12.40kg C/m2,18.21—20.93kg C/m2,respectively,in July and October,and carbon storage were the largest in plot Ⅰ.In October,soil water percentage were lower significantly than in July,soil bulk density were larger significantly than in July,and soil pH,soil carbon,nitrogen,phosphorus content were not significant differences.4.Soil enzymes activities and microbial amounts in Huahu degraded wetlandIn July,soil urease,invertase,phosphatase activities were 0.89—1.60 mg/g·d、89.86—134.31 mg/g·d、343.72—463.45 mg/g·d in 0—10 cm soil layer,and there were the significant differences in each two plots.On the whole,soil enzymes activities decreased with the increase of soil depth.Total amounts of soil microbes were(11.70—69.91)×105 No/g,those were the largest in plot Ⅱ,and those were the least in plot III.Total amounts of soil microbes in 0—10 cm soil layer accounted for 86.8%in 0—40 cm soil layer.5.The correlation analysis betw een soil properties and burrows densityBased on soil propenties and density of activities burrows data by correlation and stepwise regression analysis.Density of activities burrows,phosphorus content,soil urease activities and amounts of bacteria,actinomyces had significant negative correlation.But density of activities burrows only appeared in the optimal amounts of bacteria in regression equation.That compared with other factors,in addition to the amounts of soil bacteria and density of activities burrows were not contributed to other soil factors.6.Pikas monitoring and control measures in Huahu degraded wetlandThe results show that 644 burrows per hm2 can be considered as a density threshold in Huahu wetland.In this density of rodents,there were conducive to the improvement of soil physical properties and soil N content.However,aboveground biomass were less.Therefore vegetation and soil data were used to establish suitable density threshold.Huahu wetland as scenery spots in the summer,and as grazing grassland the winter and spring.Because of interference by grazing and tourism(tourists trample,automobile exhaust)alternately disturbance,grassland were drought evolution trend.Recommended that the area of the density of rodent control in 180—644 burrows per hm2,reducing the grazing rate in spring and winter,intensify the management of tourists,and according to the wetland environment bearing capacity limit the number of visitors. |
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