降雨格局变化对内蒙古典型草原优势种大针茅幼苗的影响

Effects of changing precipitation patterns on seedlings of Stipa grandis,a dominant plant of typical grassland of Inner Mongolia,China

大针茅(Stipa grandis)是内蒙古草原的优势物种,研究其幼苗在不同降雨格局下的响应特征,可以为进一步研究降雨格局变化下内蒙古典型草原的响应特征提供科学依据。在中国科学院内蒙古草原生态系统定位研究站,利用开顶式生长室进行控制试验模拟降雨格局变化,研究了大针茅幼苗对总降雨量和降雨间隔时间变化的响应。结果表明:1)总降雨量增加50%使大针茅幼苗生长季末的地上生物量平均增加23%(p<0.05),而降雨间隔时间由5天增长为15天使地上生物量平均增加48.8%(p<0.001)。2)总降雨量对大针茅幼苗的地下生物量没有显著影响;而在低降雨量条件下,降雨间隔时间增长使地下生物量增加56.2%(p<0.001),在高降雨量条件下作用不显著。3)总降雨量和降雨间隔时间对根冠比的效应都依赖于对方水平的高低,总降雨量增大只在较长降雨间隔条件下使根冠比发生改变(-28.4%,p<0.05),降雨间隔时间增长只在高降雨量条件下使根冠比发生改变(-28.8%,p<0.05)。4)处理期间,在处理时间分别为30天和45天时,大针茅幼苗地上生物量、地下生物量和总生物量的差异都主要取决于总降雨量;而在处理时间为75天时,其差异则都主要取决于降雨间隔时间。该研究得到以下主要结论:1)降雨间隔时间与总降雨量一样,是影响大针茅幼苗生长的关键因素之一。2)总降雨量对大针茅幼苗生长的效应与降雨间隔时间的长短紧密相关。3)降雨格局对大针茅幼苗生长的影响机制随着幼苗的生长期不同而改变。

Aims Stipa grandis is a dominant species of Inner Mongolia typical grassland.Our objective is to explore the responses of S.grandis seedlings to changed precipitation patterns to provide insight into responses of Inner Mongolia grassland to future global climate change.Methods A simulated experiment was conducted in 2009 to examine the effects of precipitation quantity and interval on S.grandis seedlings in open-top chambers at the Inner Mongolia Grassland Ecosystem Research Station of the Chinese Academy of Sciences.Important findings At final harvest,aboveground biomass of S.grandis seedlings was significantly increased by an average of 23%（p 〈0.05） by increased precipitation quantity（＋50%） and by an average of 48.8%（p 〈0.001） by extending the precipitation interval from 5 to 15 days.Precipitation quantity had no significant effect on belowground biomass.When compared with that under regular precipitation interval with same precipitation quantity,belowground biomass was significantly increased 56.2%（p 〈0.001） with extended precipitation interval under low precipitation quantity,but was not significantly affected by extended precipitation interval under high precipitation quantity.The effect of precipitation quantity and interval on root/shoot ratio depended greatly on each other.Root/shoot ratio was significantly decreased by 28.4%（p 〈0.05） by increased precipitation quantity only under the extended precipitation interval level and significantly decreased by 28.8%（p 〈0.05） by extended precipitation interval only under increased precipitation quantity.During the whole treatment period,differences in aboveground,belowground and total biomass of seedlings between treatments for seedlings treated for 30 days and 45 days were determined by total precipitation quantity,and biomass differences for seedlings treated for 75 days were determined by precipitation interval.Therefore,precipitation interval could be as important as precipitation quantity on growth of S.grandis seedlings.Effects of precipitation patterns could be complex since the effects of precipitation quantity and precipitation interval interacted greatly and changed with seedling growth period.