Asymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments

TitleAsymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments
Publication TypeJournal Article
Year of Publication2017
AuthorsWilcox KR, Shi Z, Gherardi LA, Lemoine NP, Koerner SE, Hoover DL, Bork E, Byrne KM, Cahill J, Collins SL, Evans S, Gilgen AK, Holub P, Jiang L, Knapp AK, LeCain D, Liang J, Garcia-Palacios P, Peñuelas J, Pockman WT, Smith MD, Sun S, White SR, Yahdjian L, Zhu K, Luo Y
JournalGlobal Change Biology
Volume23
Issue10
Start Page4376
Date Published10/2017
Accession NumberSEV.773
Abstract

Climatic changes are altering Earth’s hydrological cycle, resulting in altered precipitation
amounts, increased interannual variability of precipitation, and more frequent
extreme precipitation events. These trends will likely continue into the future, having
substantial impacts on net primary productivity (NPP) and associated ecosystem
services such as food production and carbon sequestration. Frequently, experimental
manipulations of precipitation have linked altered precipitation regimes to changes
in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds
generalities describing patterns of ecosystem sensitivity to altered precipitation.
Additionally, we do not know whether previously observed correlations between
NPP and precipitation remain accurate when precipitation changes become extreme.
We synthesized results from 83 case studies of experimental precipitation manipulations
in grasslands worldwide. We used meta-analytical techniques to search for
generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP
(BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity
(i.e., productivity response standardized by the amount of precipitation
change) of BNPP was similar under precipitation additions and reductions, but
ANPP was more sensitive to precipitation additions than reductions; this was especially
evident in drier ecosystems. Additionally, overall relationships between the
magnitude of productivity responses and the magnitude of precipitation change
were saturating in form. The saturating form of this relationship was likely driven by
ANPP responses to very extreme precipitation increases, although there were limited
studies imposing extreme precipitation change, and there was considerable variation
among experiments. This highlights the importance of incorporating gradients
of manipulations, ranging from extreme drought to extreme precipitation increases
into future climate change experiments. Additionally, policy and land management
decisions related to global change scenarios should consider how ANPP and BNPP
responses may differ, and that ecosystem responses to extreme events might not
be predicted from relationships found under moderate environmental changes.