Abstract

Drought is a global issue that is exacerbated by climate change and increasing anthropogenic
water demands. The recent occurrence of drought in California provides an important opportunity
to examine drought response across ecosystem classes (forests, shrublands, grasslands, and wetlands),
which is essential to understand how climate influences ecosystem structure and function. We quantified
ecosystem resistance to drought by comparing changes in satellite-derived estimates of water-use efficiency
(WUE = net primary productivity [NPP]/evapotranspiration [ET]) under normal (i.e., baseline) and
drought conditions (ΔWUE = WUE2014 − baseline WUE). With this method, areas with increasing WUE
under drought conditions are considered more resilient than systems with declining WUE. Baseline WUE
varied across California (0.08 to 3.85 g C/mm H2O) and WUE generally increased under severe drought
conditions in 2014. Strong correlations between ΔWUE, precipitation, and leaf area index (LAI) indicate
that ecosystems with a lower average LAI (i.e., grasslands) also had greater C-uptake rates when water
was limiting and higher rates of carbon-uptake efficiency (CUE = NPP/LAI) under drought conditions. We
also found that systems with a baseline WUE ≤ 0.4 exhibited a decline in WUE under drought conditions,
suggesting that a baseline WUE ≤ 0.4 might be indicative of low drought resistance. Drought severity,
precipitation, and WUE were identified as important drivers of shifts in ecosystem classes over the study
period. These findings have important implications for understanding climate change effects on primary
productivity and C sequestration across ecosystems and how this may influence ecosystem resistance in
the future.

Citation

S.L. Malone, M.G. Tulbure, A.J. PérezLuque, T.J. Assal, L.L. Bremer, D.P. Drucker, V. Hillis, S. Varela, M.L. Goulden (2016): Drought resistance across California ecosystems: evaluating changes in carbon dynamics using satellite imagery. Ecosphere. 7 (11), e01561.. DOI: 10.1002/ecs2.1561

This Paper/Book acknowledges NSF CZO grant support.