2000-2020年黄河流域植被生态质量变化及其对极端气候的响应

Dynamic changes of vegetation ecological quality in the Yellow River Basin and its response to extreme climate during 2000-2020

黄河流域处于我国生态保护和建设的重要战略地位,但流域生态环境脆弱,特别是在人类活动和气候变化等因素影响下,流域生态特征逐步发生变化,生态安全面临重大挑战。为了掌握极端气候变化对黄河流域植被生态特征影响,以植被生态质量指数(EQI)为评价指标,利用2000—2020年黄河流域气象数据和遥感数据,采用线性趋势分析、Hurst指数和相关分析等统计方法,分析了黄河流域植被生态质量的时空变化特征,探讨了气候变化背景下极端气温指标和极端降水指标与植被EQI变化关系。结果表明:(1)2000-2020年,黄河流域季尺度和年尺度植被生态质量指数均呈波动增加趋势(P<0.05),其中夏季增加趋势最大,平均每10年生态质量指数增加6.7;(2)2000年以来黄河流域有97.7%的地区植被生态质量指数呈上升趋势,其中趋势率>5/10a的面积占比为37.4%,且流域Hurst指数达到0.8,表明流域植被生态质量指数具有强持续性,未来大部分流域植被将持续改善。(3)流域植被生态质量指数与极端气温类指数以负相关为主,相关系数多介于-0.3-0.3之间,其中霜冻日数(FD0)和夏日日数(SU25)与植被生态质量具有负相关性的站点最多,占比达到78%。(4)流域植被生态质量指数与极端降水类指数多呈正相关,其站点比例平均达到85%,达到显著水平的站点比例平均为37%,且相关程度也要明显高于极端气温类指数。(5)2000年以来黄河流域降水和气温变化波动较大,但是总体上呈增加趋势,分别每10年增加31.8 mm、0.33℃,是流域植被生态质量改善的重要自然因素,其中降水影响更为显著。

The Yellow River Basin is in an important strategic position of ecological protection and construction in China,but the ecological environment of the basin is fragile.Especially under the influence of human activities and climate changes,the ecological characteristics of the Yellow River Basin have gradually changed,and ecological security is facing major challenges.In order to understand the impact of extreme climate change on ecological quality of vegetation in time,the vegetation ecological quality index(EQI)was constructed by net primary productivity(NPP)and fractional vegetation cover(FVC)as the evaluation index.By using MODIS and meteorological data from 2000 to 2020,this paper estimated the EQI and extreme climate indices in the Yellow River Basin.Based on the EQI and extreme climate indices,the aims of the present study analyzed the temporal and spatial variation characteristics of the EQI in the Yellow River Basin,and discussed the response characteristics of EQI to extreme temperature indices and extreme precipitation indices during 2000-2020,using methods of linear regression,the Hurst index,correlation analysis and other methods.The results showed that:(1)in the seasonal and annual scales,the EQI in the Yellow River Basin showed a volatility increasing trend from 2000 to 2020,which was the highest change rate of 6.7/10a in the summer.(2)In the trend analysis of EQI change,the area of increasing trend accounted for 97.7%of the basin area,of which 37.4%showed an increasing trend with the change rate>5/10a.The Hurst index of EQI in the past 21 years was 0.8,which indicated that the EQI would maintain the same trend of change in the future.(3)The EQI was negatively correlated with the extreme temperature indices,of which the correlation coefficients were mostly between-0.3 and 0.3.Among which,the number of observation stations with positive correlation between EQI and number of frost days(FD0)and number of summer days(SU25)was the largest,accounting for 78% of the total.(4)The EQI was positively correlated with the extreme precipitation indices,of which was higher than temperature indices.With positive correlation,the number of observation stations accounted for 78% of the total,which the percentage of stations that reached a significant level was 37% on average.(5)Since 2000,the variation of precipitation and temperature in the Yellow River Basin has fluctuated greatly,but generally showed an increasing trend with 31.8 mm and 0.33°C per 10 years.Warmer and wetter climate during 2000-2020 was the main driving force to promote vegetation EQI in the Yellow River Basin,which indicated that precipitation might be the key influencing factor for the vegetation EQI.