Drought recovery in terrestrial and riverine ecosystems of the CONUS:
Considering vegetation productivity and water quality
Abstract
Drought has severe impacts on the structure and functionality of
terrestrial and riverine ecosystems. The mechanism and duration of
drought recovery are critical subjects that can have crucial
ramifications for ecology, crop yield, carbon uptake, and ecosystem
services, and it has not been thoroughly investigated. This study
assesses drought recovery of terrestrial and riverine ecosystems for
agricultural and hydrological droughts, respectively. Soil moisture
simulations from Phase 2 of the North American Land Data Assimilation
System (NLDAS-2) are employed to characterize agricultural drought, and
streamflow data from the United States Geological Survey (USGS) are
utilized for assessing hydrological droughts. Drought recovery for
riverine ecosystems is studied considering both quantity and quality of
streamflow. Water temperature, dissolved oxygen, and turbidity are the
water quality variables considered in this study. Riverine drought
recovery is assessed using a multi-stage framework that is applied to
400 streamflow stations across the CONUS for the study period of
1950-2016. On the other hand, terrestrial drought recovery is
investigated utilizing ecosystem Gross Primary Productivity (GPP), a
metric of photosynthetic activity, for the regions impacted by
agricultural drought. GPP data is acquired from the Moderate resolution
Imaging Spectroradiometer (MODIS) sensor onboard Terra satellite at 1km
spatial resolution and 8-day temporal resolution across the CONUS during
2000 to 2015. The drought affected regions are assumed to be recovered
when the post-drought GPP reverts to its regional average value. Results
show that in general, riverine drought recovery takes about two months
when considering water quality variables, whereas terrestrial drought
recovery duration varies between 1 to 4 months depending on drought
severity. Additionally, results indicate that drought recovery duration
is positively correlated with drought severity.