浙江省不同植被类型植被碳利用率(CUE)对高温和干旱的响应特征OA

High temperatures and drought affect the carbon sequestration capacity of vegetation.Investigating their impacts on carbon use efficiency(CUE)is crucial for addressing climate change and achieving carbon neutrality goals.Based on the standardized temperature index(STI)and the standardized precipitation evapotranspiration index(SPEI),this study identified high-temperature and drought events in Zhejiang Province from 2001 to 2022 during summer(June to August)and autumn(September to November).The Blended Dry and Hot Events Index(BDHI)was calculated,and the response characteristics of CUE across different vegetation types to high temperatures,droughts,and their compound events were analyzed using MODIS data.The results showed that during the study period,high-temperature events in Zhejiang were dominated by mild to moderate heat,while drought events were primarily moderate and mild.The multi-year mean CUE values from June to November were 0.43,0.35,0.37,0.49,0.60,and 0.64,respectively,with the lowest CUE values(0‒0.2)being most widespread in July and August.The standardized CUE(ZCUE)anomaly showed a significant negative correlation with STI in both summer and autumn(r=-0.600 and-0.620,p<0.01).Notably,the strongest negative correlation for cropland ZCUE occurred in July(r=-0.735).The response of CUE to drought exhibited seasonal variations:a non-significant positive correlation was observed in summer(r=0.161,p>0.05),whereas a significant negative correlation appeared in autumn(r=-0.454,p<0.05).Different vegetation types showed similar partial correlation coefficients with SPEI in the concurrent month.Under compound dry-hot events,the decline in ZCUE became more pronounced with increasing BDHI intensity in July and August.Within the 95%confidence interval,the strongest correlations between ZCUE and STI,SPEI,and BDHI for all vegetation types occurred in the concurrent month.In summary,vegetation CUE is more sensitive to high temperatures than to drought,showing no time lag and decreasing efficiency with increasing heat intensity.The response to drought showed seasonal differences(negligible impact in summer,but an inhibitory effect in autumn).Compared with single-factor events,compound events had a stronger dominant effect in summer.Forests were more sensitive to these compound events than grasslands and croplands.This study improves the understanding of ecosystem vulnerability to compound climatic extremes and provides empirical evidence for refining regional vegetation restoration strategies under climate change.