Non-rainfall Moisture: A Key Driver of Microbial Respiration from Standing Litter in Arid, Semiarid, and Mesic Grassland
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Non-rainfall Moisture: A Key Driver of Microbial Respiration from Standing Litter in Arid, Semiarid, and Mesic Grasslands Sarah Evans,1,6* Katherine E. O. Todd-Brown,2,3,4 Kathryn Jacobson,5 and Peter Jacobson5 1
Kellogg Biological Station, Ecology, Evolutionary Biology, and Behavior Program, Department of Integrative Biology, Department of Microbiology and Molecular Genetics, Michigan State University, Hickory Corners, Michigan, USA; 2Pacific Northwest National Laboratory, Richland, Washington, USA; 3Wilfred Laurier University, Waterloo, Ontario, Canada; 4Engineering School of Sustainable Infrastructure and Environment, University of Florida, Gainesville, Florida, USA; 5Department of Biology, Grinnell College, Grinnell, Iowa, USA; 6Natural Resource Ecology Laboratory, Colorado State University, Campus Delivery 1499, Fort Collins, Colorado 80523, USA
ABSTRACT Models assume that rainfall is the major moisture source driving decomposition. Non-rainfall moisture (NRM: high humidity, dew, and fog) can also induce standing litter decomposition, but there have been few measurements of NRM-mediated decomposition across sites and no efforts to extrapolate the contribution of NRM to larger scales to assess whether this mechanism can improve model predictions. Here, we show that NRM is an important, year-round source of moisture in grassland sites with contrasting moisture regimes using field measurements and modeling. We first characterized NRM frequency and measured NRMmediated decomposition at two sites in the Namib Desert, Namibia (hyper-arid desert), and at one site in Iowa, USA (tallgrass prairie). NRM was frequent
Received 15 July 2019; accepted 26 October 2019 Electronic supplementary material: The online version of this article (https://doi.org/10.1007/s10021-019-00461-y) contains supplementary material, which is available to authorized users. Author’s Contributions KJ and PJ conceived the empirical study and collected data with assistance from SE. KTB and SE conceived and performed the meteorological analysis and modeling. SE was lead author, but all authors contributed to writing the paper. *Corresponding author; e-mail: [email protected]
at all sites (85–99% of hours that litter was likely to be wet were attributed to NRM) and tended to occur in cool, high-humidity periods for several hours or more at a time. NRM also resulted in CO2 release from microbes in standing litter at all sites when litter became sufficiently wet (> 5% gravimetric moisture for fine litter and > 13% for coarse), and significantly contributed to mass loss, particularly in the western Namib site that received almost no rain. When we modeled annual mass loss induced by NRM and rain and extrapolated our characterization of NRM decomposition to a final semiarid site (Sevilleta, New Mexico), we found that models driven by rainfall alone underestimated mass loss, while including NRM resulted in estimates within the range of observed mass loss. Together these findings suggest that NRM is an important missing component in quantitative and concep
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