内蒙古草原羊草物候与气象因子的关系

Relationships between Leymus chinensis phenology and meteorological factors in Inner Mongolia grasslands

研究温带草原植物物候与气象因子变化的关系,对于提高草原净初级生产量和碳收支估算的精度,掌握放牧的时宜及其区域差异,具有重要的科学意义和实践价值。该文利用内蒙古草原7个牧业气象试验站1983～2002年的羊草物候观测数据,对返青和黄枯日期与气温和降水量的关系进行了统计分析。结果表明:(1)所有站点的年平均气温均呈显著升高的趋势,多数站点的年降水量呈不显著减少的趋势;同时,各站羊草返青期和黄枯期均以显著提前的趋势占优势,多数站点的生长季节(返青到黄枯的期间)呈缩短的趋势。(2)在区域尺度上,羊草返青日期与返青前一个月均温的负相关最为显著,气温每升高1℃,返青期约提前2.4d;在站点尺度上,森林草原区站点的羊草返青期早晚主要受返青前一个月均温(负相关)的影响,典型草原区站点的羊草返青期早晚主要受前一年10月或11月到返青期累积降水量(负相关)的影响,森林草原区最北部额尔古纳右旗的返青期早晚受返青前一个月均温和前一年10月到返青期累积降水量的共同影响。(3)在区域尺度上,羊草黄枯日期与黄枯前一个月均温的负相关最为显著,气温每升高1℃,黄枯期约提前3.7d;在站点尺度上,羊草黄枯期早晚与前期气温以负相关为主,与前期降水量以正相关为主。

Studying grassland phenology and its relation to meteorological factors is crucial for enhancing the accuracy of net primary production and carbon sequestration estimate,and identifying appropriate grazing and harvesting times.Grasslands of Leymus chinensis are an endemic and dominant formation in the eastern part of Eurasia.Many studies have focused on physiological characteristics but few on phenological performances of Leymus chinensis in Inner Mongolia.Therefore,we used phenological observation data of Leymus chinensis and corresponding meteorological data from seven stations of Inner Mongolia during 1983 to 2002 to reveal statistical relationships between the greenup/brownoff date of Leymus chinensis and mean air temperature/precipitation,and find out principal factors influencing greenup and brownoff dates of Leymus chinensis at regional and local scales. Annual mean air temperature showed a significant increase trend at all seven stations,whereas annual mean precipitation indicated an insignificant decrease trend at most of the stations.At the same time,both greenup and brownoff dates of Leymus chinensis represented a dominantly significant advancement,and the growing season（period from greenup to brownoff） was shortened at most of the stations.So,the response of Leymus chinensis growing season length to climate change was different from that of woody plants,namely,a temperature increase may not induce a growing season lengthening of Leymus chinensis.At regional scales,the most significantly negative correlation appeared between the Leymus chinensis greenup date and mean air temperature over the previous one month,namely,if the mean air temperature increased 1℃,the greenup date advanced about 2.4 days.At local scales,Leymus chinensis greenup at stations of the forest steppe area was influenced mainly by the mean air temperature over the previous one month（negative correlation）,whereas Leymus chinensis greenup at stations of the typical steppe area was influenced primarily by the cumulative precipitation from the last October or November to the greenup date（negative correlation）.A special case occurred at Eerguna station located in the most northern part of the forest steppe area,there Leymus chinensis greenup was affected by both mean air temperature over the previous one month and cumulative precipitation from the last October to the greenup date.In terms of relationships between the Leymus chinensis brownoff date and meteorological factors,at regional scales,the most significantly negative correlation occurred between the Leymus chinensis brownoff date and mean air temperature over the previous one month,namely,if the mean air temperature increased 1℃,the brownoff date advanced about 3.7 days.By contrast,the correlation between the Leymus chinensis brownoff date and precipitation was less significant.At local scales,a negative correlation dominated between the brownoff date and the previous air temperature,whereas a positive correlation dominated between the brownoff date and the previous precipitation.