Early greenup impact on seasonal streamflow and soil moisture dynamics in humid, temperate forests
Abstract
Ongoing warming due to climate change has generally led to lengthened growing seasons and subsequent changes in evapotranspiration (ET) and streamflow seasonality. This has been well studied in seasonally dry, snowmelt dominated watersheds, but not in humid, temperate forested watersheds without significant seasonal snowmelt. In this study, we investigate how seasonal streamflow patterns have responded to variability in vegetation phenology in the southern Appalachians over the last four decades. We characterize low-frequency seasonal shifts in streamflow peaks using 50th percentiles of cumulative daily precipitation, streamflow and soil moisture measurements, and investigate interactions with remotely-sensed, long-term greenup anomalies in deciduous tree species-dominated watersheds. After removing a dominant precipitation control, the greenup anomalies show significant correlations with spring flow peak timing at the low-elevation broadleaf deciduous catchment. This indicates that the strong dependency of seasonal flow regimes on precipitation is mediated by warming-induced extended growing season, especially by early greenup. At a plot scale, similar correlations of cumulative soil moisture were found only at an upslope topographic position, which occupies most of the forest landscapes within the catchment. This suggests that early greenup in deciduous forests leading to early ET increase, in turn results in early soil moisture dry-down patterned by hillslope positions, and earlier seasonal streamflow peaks and subsequent declines. However, we find less significant correlations of the greenup anomalies on flow percentiles of an adjacent evergreen and a high-elevation deciduous catchment. Our study suggests that it is likely that spring flow peaks will continue to shift earlier by warming-induced early greenup even in snow-free regions, which would have great implications for future freshwater availability in the southeastern US.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H52D..01H