Global spatial heterogeneity of changes in vegetation resistance to compound drought and heat events during 2001–2020

: Vegetation resistance plays a vital role in sustaining ecosystem stability, but it is increasingly threatened by the rising frequency of compound drought and heat events (CDHEs). Despite the growing prevalence of these stressors, how vegetation resistance is changing and what mechanisms underlie these changes remain unclear, limiting our capacity to project future carbon sinks. This study examines the responses of leaf area index (LAI) and solar-induced chlorophyll fluorescence (SIF) to CDHEs. Using a geographic detector (GD) model, we explore underlying factors governing the spatial distribution of vegetation resistance changes globally during 2001–2020. The results show that CDHEs occur every 2.92 years on average and approximately 80% of vegetation response times (RTs) fall within a 2–4 mon window. Northern ecosystems generally exhibit longer RTs than southern ones. The spatial patterns of vegetation resistance, assessed through both LAI and SIF, are broadly consistent. However, SIF-based assessments indicate low resistance across a larger number of regions. Over 2001–2020, 52.1% of areas show a decrease in LAI-based resistance, and 47.1% show a similar trend for SIF-based resistance. Some regions, such as central North America and southern South America demonstrate a notable decline in resistance, whereas western Australia and central China show an increase in resistance. GD analysis identifies key climate factors, such as vapor pressure deficit, temperature, and surface net solar radiation, as the primary drivers of vegetation resistance changes in most hotspot regions. These factors interact through nonlinear effects, further influencing vegetation resistance. Overall, this study offers a scientific foundation for improving ecosystem conservation and enhancing regional ecological resistance.