Effect Of Simulated Tibetan Sheep And Yak Trampling In Different Periods On The Reproductive Characteristics,Underground Morphology And Carbohydrate Content Of Kobresia Humilis

Grazing is the most main use way to alpine meadow.The forage turning green stage is called the “forbidden grazing” of the natural grassland,while in the earlier soil thawing period that the “hoof cultivation” effect of livestock is used to stripping the thawed turf from the grassland or form a “hoof pit”,which will damage the underground organs of the plant and not conducive to the turning green.However,the changes in the growth and development characteristics of forage are still unclear under the action of livestock trampling at soil thawing to turning green stage in the cold season pastures of alpine meadows.Based on this,from the perspective of grassland grazing management,this study takes the Kobresia humilis of the main constructive species of alpine meadow in the eastern margin of the Qinghai-Tibet Plateau as a research object.In the alpine meadow of Tianzhu,Gansu Province,the changes of growth,reproduction and storage characteristics of K.humilis after two years of simulated Tibetan sheep and yak trampling at five periods of soil thawing to turning green stage in the cold season pastures were studied.To explore a scientific and reasonable rest-grazing period and suitable collocation model of livestock adaptable to the cold season pastures,and provide a basic theoretical basis for the determination of accurate rest-grazing period in spring for alpine meadows.The main finding results were as follows:1.The trampling periods had the greatest influence on the phenotypic traits of K.humilis,followed by trampling livestock species.The interaction between trampling periods and trampling livestock species had only significant or extremely significant effects on partial phenotypic traits of K.humilis.2.Under the same trampling period,the negative effects of Tibetan sheep trampling on the sexual reproduction,different modular biomass and root growth of K.humilis were lower than that of yak trampling;the sexual reproduction effort and the storage growth effort of Tibetan sheep trampling were higher than yak trampling,and the vegetative reproductive effort was lower than yak trampling.3.In the same trampling treatment combination,compared with the prophase period of thawing,the seed yield,different modular biomass and the sexual reproduction effort of the K.humilis were significantly reduced,and reproductive growth and root growth of the K.humilis were significantly inhibited during the turning green period trampling treatment.Compared with the prophase period of thawing,the seed yield decreased in other periods between 44.0% and 89.7%.The turning green initial period significantly stimulated the number of buds and tillers per unit area of the K.humilis were produced.The vegetative reproduction effort was the largest in the middle period of thawing and the smallest in the initial period of thawing.The storage growth effort and root to shoot ratio were opposite to those of vegetative reproduction effort,and the peaks of each indicator was significantly different.Storage carbohydrates of K.humilis have different responses to trampling livestock species and trampling periods,and there are also large differences in carbohydrate content in different parts.Under different periods and livestock species trampling treatments,the different modular biomass of K.humilis were expressed as rhizome> root> leaf> stalk+panicle.4.There was a trade-off of resource allocation between K.humilis reproductive organs and storage organs.Under different periods and livestock species trampling treatments,the vegetative reproduction effort of K.humilis was much greater than the sexual reproduction effort.For the average of each indicator under different combination treatments,the vegetative reproductive effort was 11.1 times that of sexual reproduction effort.5.The comprehensive evaluation results show that the phenotypic comprehensive traits of K.humilis can be divided into excellent(prophase period of thawing,Tibetan sheep and yak trampling),good(middle period of thawing,Tibetan sheep and yak trampling),general(initial period of thawing,Tibetan sheep and yak trampling),inferior(turning green initial to turning green period,Tibetan sheep and yak trampling)four grades.In summary,the phenotypic comprehensive traits of K.humilis are different under trampling treatment of different periods and livestock species.Considering the growth and development,the completion of life history,the regeneration of population for K.humilis,the effective use of alpine K.humilis meadows and the economic income of herdsmans,etc.It is suggested that the actual grazing process in the cold season pastures of this alpine meadow should be fully utilized at the prophase of soil thawing,implement rest-grazing for grassland and confinedness feeding livestock at initial period of soil thawing to the forage turning green period,and appropriately increase the proportion of Tibetan sheep and reduce the number of yaks to avoid the high intensity of the grassland.This can not only make full use of the limited grassland resources,but also promote the recuperation of grassland.