Drought Sensitivity and Trends of Riparian Vegetation Vigor in Nevada, USA (1985–2018)
Open Access
- 25 April 2020
- journal article
- research article
- Published by MDPI AG in Remote Sensing
- Vol. 12 (9), 1362
- https://doi.org/10.3390/rs12091362
Abstract
Dryland riparian areas are under increasing stress due to expanding human water demands and a warming climate. Quantifying responses of dryland riparian vegetation to these pressures is complicated by high climatic variability, which can create strong, transient changes in vegetation vigor that could mask other disturbance events. In this study, we utilize a 34-year archive of Landsat satellite data to (1) quantify the strength and timescales of vegetation responses to interannual variability in drought status and (2) isolate and remove this influence to assess resultant trends in vegetation vigor for riparian areas across the state of Nevada, the driest state in the USA. Correlations between annual late-summer Normalized Difference Vegetation Index (NDVI) and the Standardized Precipitation–Evapotranspiration Index (SPEI) were calculated across a range of time periods (varying timing and durations) for all riparian pixels within each of the 45 ecoregions, and the variability of these values across the study area is shown. We then applied a novel drought adjustment method that used the strongest SPEI–NDVI timescale relationships for each ecoregion to remove the influence of interannual drought status. Our key result is a 30 m resolution map of drought-adjusted riparian NDVI trends (1985–2018). We highlight and describe locations where impacts of invasive species biocontrol, mine water management, agriculture, changing water levels, and fire are readily visualized with our results. We found more negatively trending riparian areas in association with wide valley bottoms, low-intensity agricultural land uses, and private land ownerships and more positive trends in association with narrow drainages, public lands, and surrounding perennial water bodies (an indication of declining water levels allowing increased vegetative cover). The drought-adjusted NDVI improved the statistical significance of trend estimates, thereby improving the ability to detect such changes. Results from this study provide insight into the strength and timescales of riparian vegetation responses to drought and can provide important information for managing riparian areas within the study area. The novel approach to drought adjustment is readily transferrable to other regions.This publication has 67 references indexed in Scilit:
- Natural and managed watersheds show similar responses to recent climate changeProceedings of the National Academy of Sciences of the United States of America, 2018
- Influence of atmospheric rivers on vegetation productivity and fire patterns in the southwestern U.S.Journal of Geophysical Research: Biogeosciences, 2017
- Assessing the role of climate and resource management on groundwater dependent ecosystem changes in arid environments with the Landsat archiveRemote Sensing of Environment, 2016
- The Inland Penetration of Atmospheric Rivers over Western North America: A Lagrangian AnalysisMonthly Weather Review, 2015
- Atmospheric Rivers as Drought Busters on the U.S. West CoastJournal of Hydrometeorology, 2013
- Response of vegetation to drought time-scales across global land biomesProceedings of the National Academy of Sciences of the United States of America, 2012
- Atmospheric Rivers, Floods and the Water Resources of CaliforniaWater, 2011
- Riverine flood plains: present state and future trendsEnvironmental Conservation, 2002
- Riparian ecosytems of semi-arid North America: Diversity and human impactsWetlands, 1998
- The Ecology of Interfaces: Riparian ZonesAnnual Review of Ecology and Systematics, 1997