Effects Of Different Rest Grazing Periods On Soil Seed Bank,Plant Community Characteristics And Theoretical Grazing Capacity In Alpine Meadow

Alpine meadow is a typical grassland type in the Qinghai-Tibet Plateau,which plays an important role in protecting biodiversity,maintaining regional ecosystem stability and promoting the development of animal husbandry.However,due to factors such as climate change and human activities,alpine meadows have shown varying degrees of degradation in recent years.Grazing management is crucial for maintaining the health of alpine meadows.Rest grazing is an effective measure of grassland scientific management.It is necessary to clarify the optimal rest grazing period of alpine meadows in the Qinghai-Tibet Plateau,and provide a basis for the restoration of degraded alpine meadows and the rational utilization of non-degraded alpine meadows.Five rest grazing periods were set in the cold season pasture of Tianzhu alpine meadow on the eastern edge of the Qinghai-Tibet Plateau,including the critical period of soil thawing–grass withering period(RP1),the later period of soil thawing–grass withering period(RP2),the initial period of grass regreening–grass withering period(RP3),the later period of grass regreening–grass withering period(RP4)and local traditional rest grazing(dominant plant height 5 cm–grass withering period)(RP5).The effects of different rest grazing periods on soil seed bank,plant community characteristics,nutritional quality and theoretical grazing capacity of alpine meadow were studied.The main results are as follows:(1)More than 20 plants germinated in the tested soil seed bank,belonging to 13 families.Among them,the proportion of geocryptophyte is the largest.With the postponement of rest grazing period,the proportion of geocryptophyte decreases.The density of soil seed bank increased with the advance of rest grazing period,and in RP1 rest grazing was the largest.The number of Legumionsae in each treatment was very small,and the seed density of Gramineae and Cyperaceae decreased with the delay of rest grazing period.The Shannon-Wiener index and Simpson diversity index of RP1 rest grazing were higher than those of other rest grazing periods.The similarity between soil seed bank and aboveground vegetation in different rest grazing periods is generally low,and RP1 rest grazing is the highest.(2)Compared with RP5,the plant height of each functional group in early rest grazing was significantly increased.The coverage of Gramineae,the aboveground biomass of Cyperaceae and total aboveground biomass in RP1 were higher,and they were the lowest in RP5 rest grazing.The aboveground biomass of Gramineae in RP3 was the highest.The total underground biomass of RP3 was higher than that of RP4 and RP5,mainly reflected in the 10 ～ 20 cm and 20 ～ 30 cm was higher than that of other rest grazing periods.The root-shoot ratio was the highest in RP5 and the lowest in RP1.The Shannon-Wiener index and Simpson diversity index of plant decreased with the advance of rest grazing period.(3)RP5 rest grazing plants have higher crude protein,crude fat and crude ash content.The contents of neutral detergent fiber,acid detergent fiber and soluble sugar were higher in RP2 rest grazing,among which the content of acid detergent fiber was significantly increased by 10.13% compared with RP5,and the soluble sugar content was significantly increased by 59.64% compared with RP3(P < 0.05).(4)With the advance of rest grazing period,the amount and digestible crude protein grazing capacity showed an increasing trend.Compared with RP2,RP3,RP4 and RP5,the amount grazing capacity and digestible crude protein grazing capacity of RP1 significantly increased by 1.19,1.35,1.47,1.83 times and 1.21、1.34、1.68、1.73 times,respectively(P < 0.05).In summary,rest grazing in the critical period of soil thawing–grass withering period can improve the density and diversity of soil seed bank and the similarity with aboveground vegetation,which is conducive to soil storage of plant seeds and increase the anti-interference ability of grassland.It can improve the plant community structure,increase grassland productivity and theoretical grazing capacity.Therefore,it is suggested that the cold season pasture of alpine meadows in the Qinghai-Tibet Plateau should rest grazing in the critical period of soil thawing–grass withering period when supplementary feeding conditions are available to promote the sustainable utilization of grassland ecosystem.