大兴安岭植被变绿速率对霜冻的响应研究

Response of velocity of vegetation greenup to frost in the Greater Khingan Mountains

气候变暖降低了霜冻发生的频率,但生长季延长使植被更容易暴露在霜冻中。同时,植被物候和光合初级生产力的变化导致植被变绿速率发生改变。大兴安岭是中国对气候变化最为敏感和最早做出响应的地区之一,该区域霜冻对不同植被变绿速率的影响还未得到充分研究。论文使用NOAA气候数据记录归一化植被指数数据,分析了1982—2019年大兴安岭地区植被变绿速率的时空变化特征。以霜冻天数和霜冻强度为指标,探讨从春季开始到植被生长季旺季开始的时间段内霜冻对植被变绿速率的影响。结果表明:研究时段内霜冻天数与强度均呈下降趋势,平均下降速率分别为-0.24±0.07 d/a和-0.036±0.015℃/(d·a)。霜冻天数的减少和霜冻强度的减弱加速了森林生态系统的植被变绿速率,却也同时减缓了草原生态系统的植被变绿速率。不同生态分区的植被变绿速率对霜冻响应不同,大兴安岭北段山地落叶针叶林区和北段西侧森林草原区的植被变绿速率与霜冻天数的偏相关系数分别为-0.42(P<0.05)和-0.48(P<0.01),与霜冻强度的偏相关系数分别为-0.49(P<0.01)和-0.36(P<0.05),霜冻对植被变绿速率的影响显著。研究突出了霜冻对植被变绿速率的影响,结果可为理解区域植被对气候变化的响应提供有用参考。

Although climate warming reduces the frequency of frost,the longer growing season increases the vulnerability of plants to frost.At the same time,changes of vegetation phenology and primary photosynthetic productivity lead to changes in the vegetation greenup rate.The Greater Khingan Mountains is one of the most sensitive and earliest responding regions to climate change in China.Further study of the impacts of frost on vegetation greenup rates in this region is insufficient.This study reconstructed the vegetation greenup rate in the Greater Khingan Mountains,following which the responses of vegetation greenup rate to frost were analyzed in detail.National Oceanic and Atmospheric Administration(NOAA)Climate Data Record(CDR)Normalized Difference Vegetation Index(NDVI)data were used to study the spatiotemporal variations in vegetation greenup rates in the Greater Khingan Mountains from 1982 to 2019.This study used frost days and intensity indices to analyze the effect of frost on the rates of vegetation greenup from the beginning of the spring to the beginning of the peak vegetation growth season.The results show that during the study period,the frost days and intensity showed a downward trend,and the average decline rates were -0.24±0.07 d/a and -0.036±0.015℃/(d·a),respectively.Although decreases in frost days and frost intensity resulted in the acceleration of the greenup of forest ecosystems,the grassland ecosystem greenup rate was reduced at the same time.The response of vegetation greenup rate to frost differed among the different ecological regions.The response of vegetation greenup rate to frost events is obvious in the western forest grassland area(IIB3)and mountain deciduous and coniferous forest area(IA1)in northern Greater Khingan Mountains,and the partial correlation coefficients between the vegetation greenup rate and frost days were -0.42(P<0.05)and -0.48(P<0.01),respectively;and the partial correlation coefficients between the vegetation greenup rate and frost intensity were -0.49(P<0.01)and -0.36(P<0.05),respectively.This study highlights the effect of frost on vegetation greenup rate,and the results can provide a useful reference for understanding the response of regional vegetation to climate change.