草甸化草原优势牧草冷地早熟禾生长发育对气候变化的响应

利用青海湖北岸天然草地中冷地早熟禾(Poa crymophila)定位观测资料,应用数理统计方法,分析了该地区气候变化特征及其对牧草生长发育和产量形成的影响。结果表明:研究区年平均气温呈极显著上升趋势,升幅为0.512℃·10a-1,秋冬季气温上升幅度大于春夏季;年降水量增加主要是由春秋季降水增加所贡献的,年降水量有一个9年左右的周期;牧草生长季的干燥指数呈上升趋势,20世纪90年代末至2010年明显趋于暖干化;冷地早熟禾返青期、抽穗期、开花期和种子成熟期提前,黄枯期推迟,从而使冷地早熟禾整个生育期延长;Logistic模拟结果表明,冷地早熟禾返青后的第72天,其生长速度达到最大,为0.29cm·d-1;从返青后49d开始,由缓慢生长转为迅速生长阶段,从返青后第95天开始,其生长从迅速生长又转为缓慢生长,迅速生长期为46d;冷地早熟禾高度和地上生物量年际变化呈逐年增加趋势;热量对冷地早熟禾产量变化敏感期为5月,旬平均气温升高1℃,产量增加20～30kg·hm-2;抽穗开花期是冷地早熟禾需水敏感期,降水量增大,牧草产量增加。

Effects of climate change on Poa crymophila phenology in alpine meadow grassland in northern region of Qinghai Lake, Northwest China

Based on the field observation and meteorological data in the northern region of Qinghai Lake,this paper analyzed the annual fluctuation of air temperature,precipitation,and aridity index as well as the effects of this fluctuation on the phenology and aboveground production of Poa crymophila,a dominant grass species in this region’s alpine meadow grassland.In the region,the mean annual air temperature increased significantly at a rate of 0.512 ℃·10 a-1,with much higher increment in autumn and winter than in spring and summer.The annual precipitation increased,mainly in spring and autumn and with an about 9-year cycle.The aridity index in the growth season of P.crymophila had an increasing trend,and from the late 1990s to 2010,it was obviously getting warmer and drier.The stages of turning green,heading,flowering,and seed maturing of P.crymophila were in advance,yellowing stage delayed,and thus,the whole growth period of this grass prolonged.The simulated results with Logistic model indicated that the growth speed of the grass was the maximum on the 72nd after turning green,being 0.29 cm plant height per day.The growth speed turned from slow to rapid from the 49th day after turning green,and turned from rapid to slow from the 95th day after turning green,with a rapid growth period of 46 days.The plant height and aboveground biomass of P.crymophila increased year by year.The production of P.crymophila was most sensitive to the heat in May.With a 1 ℃ average ten-day temperature increase,the production would be increased by 20-30 kg·hm-2.Water availability was crucial for P.crymophila during its heading and flowering stages.The production of the grass would be increased with the increase of precipitation.