The increasing frequency and severity of extreme droughts pose a significant threat to the stability and health of terrestrial ecosystems, weakening the land carbon sink. A crucial aspect of ecosystem resilience is the time needed for recovery from severe drought – a process termed drought recovery. While single extreme drought event recovery within a growing season has been studied, the interaction between vegetation phenology (timing of growing season) and drought remains poorly understood. This study focuses on the mid- and high-latitudinal Northern Hemisphere, characterized by marked seasonality and drought susceptibility. The research hypothesizes that earlier spring phenology in the drought year will prolong recovery due to biophysical feedbacks, while delayed spring phenology in the subsequent year will postpone growth due to biological processes. The study aims to identify divergent drought recovery trajectories and quantify the impact of phenology, alongside other bioclimatic factors, on recovery.

Previous research has explored drought recovery from single extreme events within a growing season. However, the interaction of vegetation phenology with drought timing and intensity is understudied. Studies have shown that drought recovery is influenced by multiple factors including vegetation phenology, drought timing, and seasonal bioclimatic factors. These factors interact to determine the timing of recovery, which can be rapid (within a single growing season) or prolonged (extending to subsequent seasons). Spring phenology strongly influences vegetation growth and soil water consumption, impacting drought recovery. Additionally, non-growing season conditions (temperature and snow accumulation) affect spring phenology, further influencing recovery. The rapid impact of climate warming on vegetation phenology and shifting drought seasonality highlight the need to understand the complex feedbacks between phenology, drought, and recovery.

The study used multiple remotely sensed datasets to quantify vegetation phenology effects on drought recovery across the mid- and high-latitudinal Northern Hemisphere from 1982 to 2015. Three independent vegetation proxies were employed: Normalized Difference Vegetation Index (NDVI) from AVHRR (measuring vegetation greenness), contiguous sun-induced fluorescence (CSIF) from MODIS (measuring photosynthesis), and microwave-based vegetation optical depth (VOD) from AMSR (measuring canopy biomass). Extreme drought events were defined using the multiscalar Standardized Precipitation Evapotranspiration Index (SPEI). The study identified two drought recovery trajectories: recovery within a single growing season (*R*_SGS) and recovery extending to the subsequent growing season (*R*_MGS). Random forest (RF) models were used to attribute drought recovery to phenology, drought sensitivity, and multiple bioclimatic and soil factors. Separate models were built for *R*_SGS and *R*_MGS for four vegetation types (evergreen and deciduous forests, shrubs, and grasses). The RF models were used to analyze the relative importance of different factors in influencing drought recovery. Spatial analyses were conducted to examine the geographic patterns of drought recovery and the relationship between recovery time and factors such as aridity and latitude. The study also investigated the relationships between drought recovery and bioclimatic factors across different vegetation types and Köppen–Geiger climate zones.

The analysis revealed that approximately 50% of ecosystems failed to fully recover from early-growing season extreme droughts within a single growing season. This percentage increased to over 60% and 80% for mid- and late-growing season droughts, respectively. Longer drought recovery times were observed in central North America, the Mediterranean, and central Eurasia. Drought recovery time decreased with increasing latitude and aridity. Earlier spring phenology in the drought year prolonged recovery when droughts occurred mid-growing season, likely due to increased evapotranspiration and soil moisture depletion. Delayed spring phenology in the subsequent year consistently delayed drought recovery across all vegetation types (46–58% importance). RF models indicated that the impact of spring phenology on drought recovery was comparable to or larger than other climatic factors. Negative temperature anomalies during the dormant period and both positive and negative anomalies in snow water equivalent (SWE) also delayed recovery. Higher mean annual temperatures were associated with longer drought recovery times. Preceding growth conditions significantly influenced drought recovery, particularly for woody plants. Drought sensitivity and drought response lag did not have significant effects on recovery.

The findings strongly support the hypothesis that vegetation phenology significantly affects drought recovery, interacting with drought timing and vegetation type. Earlier spring phenology during the drought year can lead to increased evapotranspiration and soil moisture depletion, particularly when droughts occur mid-growing season, resulting in slower recovery. Conversely, earlier spring phenology in the subsequent year may improve recovery. Delayed spring phenology in the subsequent year predominantly slows down vegetation growth and prolongs recovery. The influence of climatic factors during the drought year on recovery extending to the subsequent growing season is less significant than the effect of spring phenology in the subsequent year. The results highlight the critical role of pre-drought growth conditions in determining drought resilience, particularly for woody plants. Higher mean annual temperatures exacerbate the impact of phenology on drought recovery. The study’s results suggest that interactions between phenology and drought must be accurately represented in Earth system models to improve predictions of ecosystem response to climate change.

This study demonstrates that vegetation phenology significantly influences drought recovery in Northern Hemisphere ecosystems, with effects comparable to or exceeding those of other climatic factors. The interplay between phenology, drought timing, and vegetation type is crucial. Earlier spring phenology during a drought year can hinder mid-growing season recovery, while delayed phenology in the subsequent year slows overall recovery. These findings underscore the need to incorporate these complex interactions into Earth system models to accurately project the future of terrestrial ecosystems under intensified droughts and climate change. Future research could focus on the physiological mechanisms underlying the observed phenological effects and further investigate regional variations in drought resilience.

The study relies on remotely sensed data, which may have limitations in accurately capturing fine-scale variations in vegetation dynamics. The analysis focused on single extreme drought events, potentially underestimating the effects of multiple or prolonged drought occurrences. Further research is needed to validate these findings using ground-based measurements and to explore the effects of other factors (e.g., land management practices) on drought recovery.