| The grazing ecosystem of alpine meadow is extremely important for the maintenance of ecological balance and the development of animal husbandry in China.Under the influence of global warming and human factors,some areas are seriously degraded.Grassland usually rests during the regreening period to facilitate grassland recovery,but the soil has begun to thaw before the grass regreens.At this time,grazing will destroy the soil structure and damage the plant roots.This paper takes the cold season pasture of alpine meadow in the eastern margin of the Qinghai-Tibet Plateau as the object and determines the period of rest grazing according to the soil thawing and grass regreening in spring.The critical period of soil thawing,the late period of soil thawing,the early period of regreening,the late period of regreening and the local traditional rest grazing were taken as the start time of rest grazing,and the plant withering period was the end time of rest grazing to study the effects of rest grazing in different periods of spring on the reproduction and biomass allocation of accompanying species Kobresia humilis and dominant species Polygonum viviparum,and the suitable start time of rest grazing in spring was selected and sustainable utilization of alpine meadow.The main results are as follows:1.Rest grazing at the critical period of soil thawing is conducive to the growth of aboveground parts of K.humilis and P.viviparum.During the critical period of soil thawing,the biomass of each component of K.humilis was higher than that in other plots.The biomass of roots and rhizomes was significantly higher than that of other plots.The leaves biomass,stalk + panicle biomass,root biomass and rhizome biomass were 239.6 %,207.1 %,200.6 % and 141.6 % higher than those in the traditional rest grazing plot,respectively.The flower biomass of P.polygonum in the grazing plots was significantly higher than that in other plots during the critical period of soil thawing,and the flowers biomass,bulbils biomass,stalk biomass and leaves biomass of P.viviparum were 862.4%,37.0%,56.0% and 32.2% higher than those in the traditional rest grazing plot.Early rest grazing has a greater promoting effect on the sexual reproduction input of P.viviparum and has a greater promoting effect on the lower part input of K.humilis.With the advance of rest grazing,the two forages completed the continuation of the population by reducing the input of underground part and increasing the input of reproduction.2.Rest grazing at the critical period of soil thawing is conducive to the reproduction of K.humilis and P.viviparum.During the critical period of soil thawing,the seed yield and its components(except the number of seeds per panicle)and seed quality of K.humilis in the rest grazing plot were higher than those in other plots.The seed weight per seed was significantly higher than that in other plots.The stalk length and seed yield were 416.3% and 142.5% higher than those in the traditional rest grazing plot,respectively.At the critical period of soil thawing,the sexual reproduction effort and length of the flower spike was significantly higher than that in other plots.The vegetative reproduction effort,panicle length,flower number,panicle number,plant height,panicle base diameter,single seed weight,seed number per panicle,plant density and seed yield of P.viviparum in rest grazing plot were higher than those in other plots.The effect of early rest grazing on sexual reproduction of P.viviparum was greater than that of K.humilis.With the advance of rest grazing,the reproductive capacity of the two forages increased.3.The results of comprehensive evaluation by grey correlation analysis showed that the results of K.humilis and P.viviparum were: critical period of soil thawing >late period of soil thawing > early period of regreening > late period of regreening >traditional rest grazing.Based on the above results,it is suggested that the spring rest grazing in alpine meadow should start at the critical period of soil thawing. |
