宁夏云雾山典型草原休眠期气候变化对生产力的影响

Effects of Climate Variability during the Dormancy Period on Productivity in Typical Grassland at Yunwushan in Ningxia

基于1992-2011年黄土高原典型草原长期生产力观测数据及相应气候资料,分析了近20a来宁夏云雾山地区休眠期(11月-翌年3月)温度及降水变化趋势,利用简单线性回归及偏最小二乘回归法(Partial Least Squares regression-PLS)探究了休眠期月和日不同尺度温度和降水变化对草地生产力的影响特征,以揭示黄土高原典型草原生产力对休眠期气候变化的响应规律。结果表明:(1)近20a来研究区休眠期平均气温以0.09℃·a-1的速率极显著升高(P<0.01),其中1月和3月升温最为显著(P<0.01);(2)休眠期降水量较少,且年际间变异较大,各月降水变化趋势亦不显著;(3)休眠期内不同阶段温度变化对草地生产力具有不同影响,但整体呈现抑制效应,降水变化对生产力影响不显著;(4)休眠期温度升高抑制草地生产力发展,其作用机制可能与温度升高引起的地表积雪减少、冻融交替频繁及土壤微环境变化有关。休眠期降雨较少,降雨与草地生产力并不存在显著作用关系。降雪作为降水的固态形式,其对生产力的影响特点及作用机制尚待深入探究。

Based on long-term records of grassland productivity and the corresponding climatic data on the Loess Plateau during 1992-2011, the change trends of temperature and precipitation during the dormancy period （November to next March） in Yunwushan area were analyzed. To reveal the response patterns of grassland productivity to dormancy climate change on the Loess Plateau, the effects of variation in climatic factors at monthly and daily scale on grassland productivity were investigated by using simple linear regression and Partial Least Squares （PLS） regression, respectively. The results indicated that： （1） in the past 20 years, mean temperature during the dormancy period in the study area has increased significantly （P〈0.01）, with a rate of 0.09℃·y-1, while the strongest increasing trend occurred in January and March. （2） The precipitation during the dormancy period was few, but its inter-annual variation was large. The change trend of monthly precipitation was also not significant. （3） Different impacts of temperature during different periods on productivity were found. However, overall, increased temperature during the dormancy period was negatively correlated with grassland productivity. Impacts of precipitation were negligible. （4） The negative correlations between increased dormancy temperature and grassland productivity could be properly explained by decreased snow depth, increased freezing and thawing processes, and variations in soil micro-environment caused by winter warming. The rare precipitation during the dormancy period did not exert significant effects on productivity. However, snow, as a solid form of winter precipitation, its impacts on grassland productivity need further investigations.