TY - JOUR T1 - State changes: insights from the U.S. Long Term Ecological Research Network JF - Ecosphere Y1 - 2021 A1 - Zinnert, Julie C. A1 - Nippert, J.B. A1 - Rudgers, Jennifer A. A1 - Pennings, Steven C. A1 - González, Grizelle A1 - Alber, Merryl A1 - S.G. Baer A1 - J. M. Blair A1 - Burd, Adrian A1 - S L Collins A1 - Craft, Christopher A1 - Di Iorio, Daniela A1 - Dodds, Walter K. A1 - Groffman, Peter M. A1 - Herbert, Ellen A1 - Hladik, Christine A1 - Li, Fan A1 - Litvak, Marcy E. A1 - Newsome, Seth A1 - O’Donnell, John A1 - Pockman, William T. A1 - Schalles, John A1 - Young, Donald R. VL - 12 UR - https://onlinelibrary.wiley.com/toc/21508925/12/5 IS - 5 ER - TY - JOUR T1 - Drought consistently alters the composition of soil fungal and bacterial communities in grasslands from two continents JF - Global Change Biology Y1 - 2018 A1 - Ochoa-Hueso, Raúl A1 - Scott. L. Collins A1 - Delgado-Baquerizo, Manuel A1 - Hamonts, Kelly A1 - Pockman, William T. A1 - Sinsabaugh, Robert L. A1 - M.D. Smith A1 - Alan K. Knapp A1 - Power, Sally A. AB -

The effects of short‐term drought on soil microbial communities remain largely unexplored, particularly at large scales and under field conditions. We used seven experimental sites from two continents (North America and Australia) to evaluate the impacts of imposed extreme drought on the abundance, community composition, richness, and function of soil bacterial and fungal communities. The sites encompassed different grassland ecosystems spanning a wide range of climatic and soil properties. Drought significantly altered the community composition of soil bacteria and, to a lesser extent, fungi in grasslands from two continents. The magnitude of the fungal community change was directly proportional to the precipitation gradient. This greater fungal sensitivity to drought at more mesic sites contrasts with the generally observed pattern of greater drought sensitivity of plant communities in more arid grasslands, suggesting that plant and microbial communities may respond differently along precipitation gradients. Actinobateria, and Chloroflexi, bacterial phyla typically dominant in dry environments, increased their relative abundance in response to drought, whereas Glomeromycetes, a fungal class regarded as widely symbiotic, decreased in relative abundance. The response of Chlamydiae and Tenericutes, two phyla of mostly pathogenic species, decreased and increased along the precipitation gradient, respectively. Soil enzyme activity consistently increased under drought, a response that was attributed to drought‐induced changes in microbial community structure rather than to changes in abundance and diversity. Our results provide evidence that drought has a widespread effect on the assembly of microbial communities, one of the major drivers of soil function in terrestrial ecosystems. Such responses may have important implications for the provision of key ecosystem services, including nutrient cycling, and may result in the weakening of plant–microbial interactions and a greater incidence of certain soil‐borne diseases.

VL - 24 UR - http://doi.wiley.com/10.1111/gcb.2018.24.issue-7 IS - 7 ER - TY - JOUR T1 - Asymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments JF - Global Change Biology Y1 - 2017 A1 - K.R. Wilcox A1 - Shi, Zheng A1 - Gherardi, Laureano A. A1 - Lemoine, Nathan P. A1 - Koerner, Sally E. A1 - Hoover, David L. A1 - Bork, Edward A1 - Byrne, Kerry M. A1 - Cahill, James A1 - Scott. L. Collins A1 - Evans, Sarah A1 - Gilgen, Anna K. A1 - Holub, Petr A1 - Jiang, Lifen A1 - Alan K. Knapp A1 - LeCain, Daniel A1 - Liang, Junyi A1 - Garcia-Palacios, Pablo A1 - Peñuelas, Josep A1 - Pockman, William T. A1 - M.D. Smith A1 - Sun, Shanghua A1 - White, Shannon R. A1 - Yahdjian, Laura A1 - Zhu, Kai A1 - Luo, Yiqi AB -

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.

VL - 23 UR - https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13706 IS - 10 JO - Glob Change Biol ER -