Suitable Distribution Area Of Stipa Species And The Correlation With Climatic Factors In The Mongolian Plateau And Qinghai-Tibet Plateau

Stipa species are the major constructive and dominant species of steppes in China. From south to north, from east to west, and from high altitude to low altitude, forming a series of alternative distribution. Especially in the Mongolian Plateau and Qinghai-Tibet Plateau, stipa species are adapted to arid and alpine climate through differentiating, and constitute distinctive and unique stipa steppe series. In this paper, 10 widely distributed stipa species in the Mongolian Plateau and Qinghai-Tibet Plateau are selected as research subjects. Different levels of climate suitable distribution areas of these stipa species are built by Maxent and ArcGIS with 20 environmental factors. In addition, factors whose cumulative contribution percent are more than 90% are screened as the dominant factors, and a detailed quantitative description of their value ranges are given. This study has theoretical significance in further revealing alternative distribution of stipa species, formation and adaptive mechanism of stipa steppes; And a certain value in grasslands protecting, restoration and rational utilization, as well. The main conclusions are drawn as follows:1) The suitable distribution areas of 10 stipa species in the Qinghai-Tibet and Mongolian Plateau have obvious regional characteristics. There are large differences in the area of suitable distribution regions. The percentage of each stipa species occupying the total area of the study region is glareosa stipa (51.38%), baicalensis stipa (33.90%), grandis stipa (30.37%), krylovii stipa (29.98%), purpurea stipa (26.16%), klemenzii stipa (14.16%), roborowskyi stipa (13.84%), breviflora stipa (13.28%), capillacea stipa (10.55%) and basiplumosa stipa (8.65%), respectively. High suitable distribution areas of krylovii stipa, grandis stipa and baicalensis stipa are located in northeastern and eastern part of the Mongolian Plateau; High suitable distribution areas of breviflora stipa and klemenzii stipa are located in southwestern and south-central part of the Mongolian Plateau; And high suitable distribution areas of purpurea stipa, basiplumosa stipa, roborowskyi stipa, capillacea stipa and glareosa stipa are located in the alpine region of the Qinghai-Tibet Plateau.2) The common dominant factors affecting distribution of 10 stipa species are annual mean temperature (-5.7～7.5℃), precipitation of warmest quarter (60～290 mm), mean temperature of warmest quarter (5.5～22℃) and mean temperature of driest quarter (-21～-2.5℃).3) Compared with precipitation, temperature has greater impacts on purpurea stipa, basiplumosa stipa, roborowskyi stipa, capillacea stipa and glareosa stipa. The range of contribution percent and suitable value of annual mean temperature is 62.2% ～95.5% and-6.25～5.5℃, respectively. The dominant temperature factors affecting distribution of purpurea stipa are mean temperature of warmest quarter and isothermality, contribution percent of these two factors is 43.5% and 29.7%, respectively. Isothermality and mean temperature of warmest quarter as dominant factors have an impact on distribution of basiplumosa stipa, and contribution percent of these two factors is 27.6% and 24.8%, respectively. Roborowskyi stipa are largely affected by mean temperature of warmest quarter and isothermality, contribution percent of these two factors is 20.7% and 29.9%, respectively.Dominant factor which has effect on distribution of capillacea stipa is isothermality, and contribution percent of isothermality is 43.4%. While mean temperature of warmest quarteris playing an important role in distribution of glareosa stipa, and the contribution percent is 22.9%.4) With respect to temperature, kylovii stipa, grandis stipa, baicalensis stipa, breviflora stipa and klemenzii stipa are mainly influenced by precipitation. The range of contribution percent and suitable value of annual precipitation is 57.1%～70.5% and 125～460 mm, respectively. The dominant factor affecting distribution of hylovii stipa is precipitation of warmest quarter, and the contribution percent is 26.5%. Grandis stipa and baicalensis stipa are largely affected by annual precipitation, and the contribution percent is 28.0% and 27.1%, respectively. While breviflora stipa and klemenzii stipa are mainly influenced by precipitation of wettest month and precipitation of warmest quarter, and contribution percent of these two factors is 21.1% and 28.9%, respectively.5) Stipa species:purpurea stipa, basiplumosa stipa, roborowskyi stipa, capillacea stipa and glareosa stipa which are principally affected by temperature, working as constructive or dominant species, constitute alpine steppe. Topographical factor:altitude which has an indirect impact on temperature influences these five stipa species seriously. Stipa species:krylovii stipa, grandis stipa, baicalensis stipa, breviflora stipa and klemenzii stipa largely impacted by precipitation form constructive and dominant species of temperate steppe. And the resulting large-scale spatial differentiation of stipa species in the Qinghai-Tibet and Mongolian Plateau is generated.