Growth And Reproductive Characteristics Of Thermopsis Lanceolata And Its Responses To Management Practices In Alpine Meadow Of The Qinghai-tibetan Plateau

As a kind of typical indicator species in degraded grassland of noxious and miscellaneous grass type, Thermopsis lanceolata has a very important effect on the restoration of degenerated grassland. Studies on Thermopsis lanceolata with 4 elevation gradient(3000m, 3075 m, 3145 m, 3220m) and 3 management measures(grazing, fencing and comprehensive cultivations) were carried out to analyze the leaf functional traits, characteristic of individual traits, biomass distribution of various organs and characteristic of resource allocation, the effect of different management measures on community structure and composition, spatial distribution pattern, and then compare the growth and reproductive characteristics of Thermopsis lanceolata in different condition aiming at reveal the impact of elevation gradient and grassland management measures on the reproductive module and ecological control effectiveness of Thermopsis lanceolata.The results indicated that:1) With the increasing of elevation, the soil water content, soil total N content and soil total organic matter increased, the leaf size(leaf length, leaf width, leaf area and leaf perimeter) decreased; the leaf thickness in 3000 m was significantly greater than the other three elevations(P<0.05); the width of the midrib vascular bundle and thickness of leaf upper and lower epidermis cell declined; the Thermopsis lanceolata in high elevation(3220m) had fewer branches and leaves, lesser root, stem and leaf biomasses, while more flower and pod biomasses than the other elevations; the Thermopsis lanceolata took measures of decreasing root, stem and leaf investment and increasing the reproductive investment to adapt the environment change of high elevtion; there were obvious correlation among different characters of various organs(P<0.05).2) Compared with the grazing treatment, comprehensive cultivations treatment can significantly decrease the leaf size(leaf length, width and area)(P<0.05), fencing and comprehensive cultivations treatment, especially comprehensive cultivations treatment reduced the height of reproductive and vegetative branches, number of branches, flowers and pods per plant(P<0.05). Compared with the grazing treatment, fencing treatment significantly increased root biomass and reproductive investment(P<0.05), significantly reduced stem and leaf investment(P<0.05); compared with the fencing treatment, comprehensive cultivation treatment significantly decreased total biomass, over-ground biomass, flower and pod biomass and reproductive investment(P<0.05). Stem and leaf biomass of Thermopsis lanceolata was extremely correlated with total biomass under different restoration measures(R2>0.93)(P<0.01).3)There exited allometric relationship among the leaf length, leaf width and leaf area, and the SMA slopes of allometric growth equation were slightly effected with the rising of the elevation. The SMA slopes of allometric growth equation between leaf length and leaf area changed from 0.466 to 0.556, the SMA slopes between leaf length and leaf area changed from 0.503 to 0.618. Thermopsis lanceolata adjusted the resourse allocation strategy to adapt the elevation changes by reducing the leaf investment and increasing the stem investment. The SMA slopes among stem biomass, total leaf biomass and total biomass increased with the elevation increased. Different grassland management measures had different affection on stems and leaf traits of Thermopsis lanceolata. There were allometric relationship among the leaf length, leaf width and leaf area under all the three treatments. The highest SMA slopes between leaf length and leaf area was found under fencing treatment(R2=0.889,P<0.01); The highest SMA slopes between leaf width and leaf area was comprehensive cultivation treatment(R2=0.918,P<0.01). While, approximate isometric growth was found between total leaf biomass and stem biomass. There were simple allometric relationship between the specific leaf weight and stem biomass and the range of SMA was 0.473~0.629. The highest SMA between the specific leaf weight and stem biomass was under comprehensive cultivation treatment.4) Fecing and comprehensive cultivations treatment increased the amount of graminaceous, decresed the amount of fobs such as Thermopsis lanceolata in the community. The Margelef index(16.574) under fencing treatment was obviously high than grazing and comprehensive cultivations treatment; the Shannon-wiener index(3.433) and Pielou index(0.906) under comprehensive cultivations treatment were significant high than grazing and fencing treatments(P<0.05). In the 0~10m scales, the spatial distribution pattern under fecing and comprehensive cultivations treatments was aggregated distribution; while in the grazing area, because of the selective diet of livestock, the competition pressure that Thermopsis lanceolata facing was small and the relationship between individuals of Thermopsis lanceolata changed from asylum to compative, and then then spatial distribution pattern changed from aggregated distribution to uniform distribution.5) Thermopsis lanceolata can adjust the growth and reproductive strategy to adapt environmental changes by adjusting the leaf morphological characteristics, individual characters, resourse allocation strategy and spatial distribution pattern. It is found that fencing treatment cannot control the noxious weed effectively, so the comprehensive cultivations treatment would be a better solution to control the noxious weed.