昼夜不对称增温对大兴安岭森林净初级生产力的影响

Effects of different changes in daytime and nighttime temperatures on forest net primary productivity in the Greater Khingan Mountains

【目的】大兴安岭森林分布广袤,是我国东北地区重要的林木基地和生态屏障。本研究旨在探讨昼夜不对称增温背景下大兴安岭森林净初级生产力(NPP)的变化及其对气候变化的响应,为当地林业生态管理提供科学依据。【方法】利用MODIS NPP数据及降水、气温数据,应用趋势分析法分析气候和NPP的变化,用相关分析方法分析大兴安岭森林2000—2019年NPP与各气候因子的相关性。【结果】1)2000—2019年大兴安岭森林NPP总体上以6.26 g·C·m^(-2)·a^(-1)的速率显著增加,空间上大多数像元均呈显著增加趋势(P<0.10),仅5.60%的像元呈不显著变化或显著下降的趋势,主要集中在中北部区域;2)大兴安岭森林NPP主要受夏季气候条件的影响,NPP与夏季降水呈显著正相关;夏季最高气温和最低气温对NPP的影响不同,NPP与最高气温呈显著负相关,而与最低气温呈正相关;南部区域对气候的敏感性相较于北部区域更强;3)大兴安岭森林区域夏季降水和最低气温呈显著增加趋势,最高气温呈降低趋势,均有助于促进NPP增加;空间上南部和中部降水变化较为强烈,最低气温变化明显的区域主要集中在中部和北部。【结论】2000—2019年大兴安岭森林NPP呈增加趋势,主要由夏季降水增加及夜晚气温上升导致;夏季白天和夜晚气温变化不对称,同时NPP与白天和夜晚温度响应特征存在差异,导致昼夜温度对大兴安岭森林NPP变化存在不对称影响。

【Objective】The vast forest zone in the Greater Khingan Mountains is an important forest base and ecological barrier of northeast China.In this paper,the change of net primary productivity(NPP)and its response to climate change in the Greater Khingan Mountains was studied under the background of diurnal asymmetric warming in order to provide a scientific basis for forestry ecological management.【Method】Based on MODIS NPP,the precipitation and temperature data,the trend analysis method was used to analyze the climate and NPP change character,the coefficient correlation analysis method was applied to investigate the correlation between NPP and climate factors in the Greater Khingan Mountains from 2000 to 2019.【Result】1)From 2000 to 2019,the forest NPP in the Greater Khingan Mountains generally showed a significant increasing trend with a growth rate of 6.26 g·C·m^(-2)/a.Most pixels in space showed a significant increasing trend(P<0.05),and only 5.60%of the pixels showed an insignificant or significant declining trend,mainly concentrated in the central and northern regions;2)The NPP of forests in the Greater Khingan Mountains was mainly affected by climate conditions in summer,and there was a significantly positive correlation between NPP and summer precipitation.The maximum and minimum temperatures in summer had different effects on NPP.NPP was significantly negatively correlated with the maximum temperature,and positively correlated with the minimum temperature.The NPP in the southern region was more sensitive to climate than that in the northern region;3)On the whole,the precipitation and minimum temperature in summer in the forest region of the Greater Khingan Mountains showed a significantly increasing trend,while the maximum temperature showed a decreasing trend,which contributed to the increase of NPP.In space,the precipitation change was more intense in the south and central regions,and the minimum temperature changes were mainly concentrated in the central and northern regions.【Conclusion】From 2000 to 2019,the NPP of forests in the Greater Khingan Mountains has been increasing,and it is mainly caused by the increase of summer precipitation and nighttime temperatures.The daytime and nighttime temperature changes are asymmetric in summer,and the response characteristics of NPP to daytime and nighttime temperatures are different,leading to the asymmetric influence of diurnal temperature on the NPP of forests in the Greater Khingan Mountains.