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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Rangeland Resources & Systems Research » Research » Publications at this Location » Publication #341089
Title: Experimental droughts with rainout shelters: A methodological review

Author
item Hoover, David
item WILCOX, KEVIN - University Of Oklahoma
item YOUNG, KRISTINA - Northern Arizona University

Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2017
Publication Date: 1/19/2018
Citation: Hoover, D.L., Wilcox, K., Young, K. 2018. Experimental droughts with rainout shelters: A methodological review. Ecosphere. 9(1):1-14.

Interpretive Summary: Droughts are predicted to become more frequent and intense with climate change, which may have large impacts on ecosystems. Over the past two decades, experimental droughts have become the dominant method to assess ecosystem sensitivity to drought worldwide, yet ecological responses have been highly variable. In this study, we examined the methods of 89 published drought experiments and then used long-term precipitation records to place the experimental droughts in a historical perspective. Overall we found that drought experiments were mostly short-term, extreme droughts in water-limited ecosystems such as grasslands. Therefore many ecosystem types and drought scenarios were underrepresented in the literature. Furthermore, we determined that variability in natural rainfall may have had large and underappreciated impacts on the drought experiments. The results from this study can inform the design and interpretation of experimental droughts and highlight critical gaps in our knowledge on ecological sensitivity to drought.

Technical Abstract: Forecast increases in the frequency, intensity and duration of droughts with climate change may have extreme and extensive ecological consequences. There are currently hundreds of published, ongoing and new drought experiments worldwide aimed to assess ecosystem sensitivities to drought and identify the mechanisms governing ecological resistance and resilience. To date, the results from these experiments have varied widely, and thus patterns of drought sensitivities and the underlying mechanisms have been difficult to discern. Here we examined 89 published drought experiments, along with their associated historical precipitation records to (1) identify where and how drought experiments have been imposed, (2) determine the extremity of the drought treatments in the context of historical climate, and (3) assess the influence of ambient precipitation variability on drought experiments. In general, drought experiments were biased towards water-limited ecosystems with short-statured vegetation and were often short-term, as 80% were 1-4 years in duration. When placed in the historical context, the majority of drought experiments imposed extreme drought, with 61% below the 5th, and 43% below the 1st percentile of the 50-year annual precipitation distribution. We also determined that interannual precipitation variability had a large and potentially underappreciated effect on drought experiments due to the co-varying nature of control and drought treatments. Thus detecting significant ecological effects in drought experiments is strongly influenced by the interaction between drought treatment magnitude, precipitation variability and key ecological thresholds. The patterns that emerged from this study have important implications for the design and interpretation of drought experiments and also highlight critical gaps in our understanding of the ecological effects of drought.