%0 Journal Article %J Earth-Science Reviews %D 2022 %T Embracing the dynamic nature of soil structure: A paradigm illuminating the role of life in critical zones of the Anthropocene %A Sullivan, P.L. %A Billings, S.A. %A Hirmas, D. %A Li, L. %A Zhang, X. %A Ziegler, S. %A Murenbeeld, K. %A Ajami, H. %A Guthrie, A. %A Singha, K. %A Gimenez, D. %A Duro, A. %A Moreno, V. %A Flores, A. %A Cueva, A. %A Koop, A. %A Aronson, E.L. %A Barnard, H.R. %A Banwart, S.A. %A Keen, R.M. %A Nemes, A. %A Nikolaidis, N.P. %A Nippert, J.B. %A Richter, D. %A Robinson, D.A. %A Sadayappan, K. %A de Souza, L.F.T. %A Unruh, M. %A Wen, H. %B Earth-Science Reviews %V 225 %P 103873 %G eng %U https://linkinghub.elsevier.com/retrieve/pii/S0012825221003743 %N 91 %R 10.1016/j.earscirev.2021.103873 %0 Journal Article %J Biogeosciences %D 2021 %T Deepening roots can enhance carbonate weathering by amplifying CO2-rich recharge %A Wen, H. %A Sullivan, P.L. %A Macpherson, G.L. %A Billings, S.A. %A Li, L. %B Biogeosciences %V 18 %P 55-75 %G eng %U https://bg.copernicus.org/articles/18/55/2021/ %R 10.5194/bg-18-55-2021 %0 Journal Article %J Soil Biology & Biochemistry %D 2012 %T Tracking C and N flows through microbial biomass with increased soil moisture variability %A Tiemann, L.K. %A Billings, S.A. %K Carbon use efficiency %K Climate change %K grassland %K Precipitation regime %K Soil carbon %K Soil moisture variability %K Soil nitrogen %X

Changes in soil moisture with cycles of soil wetting and drying are associated with shifts in osmotic potentials that can induce physiological stress for microbial communities. These instances of soil moisture stress can be of sufficient magnitude to alter flows of C and N at an ecosystem scale. In this study we manipulated the duration and severity of soil moisture stress and disturbance in grassland soils from four sites along a precipitation gradient. After subjecting soils to a two-month long incubation under two different wetting-drying regimes, one of high and one of low stress and disturbance, we moistened soils with 13C- and 15N-labeled glycine solution to trace C and N though the soil and its microbial communities as they dried. Contrary to our predictions, we found evidence for preferential use of N-free osmolytes with increased soil moisture stress in soils from the mesic end of the precipitation gradient. Soils from the western, semi-arid end of the gradient were less sensitive to soil moisture stress and did not differ in N demand under high and low stress. Specific respiration rates were higher in all soils under greater soil moisture stress immediately after re-wetting, then returned to levels equal to or below rates in soils under low soil moisture stress regimes. Nitrification outpaced denitrification processes in soils under the highest levels of soil moisture stress. These results suggest increases in both soil CO2 release and N losses as stress induced by greater soil moisture variability increases in relatively mesic grassland systems, a predicted consequence of climate change in this region.

%B Soil Biology & Biochemistry %V 49 %P 11 -22 %G eng %U https://www.sciencedirect.com/science/article/abs/pii/S0038071712000521?via%3Dihub %M KNZ001506 %R 10.1016/j.soilbio.2012.01.030 %0 Journal Article %J Soil Biology and Biochemistry %D 2011 %T Changes in variability of soil moisture alter microbial community C and N resource use %A Tiemann, L.K. %A Billings, S.A. %X

Grassland ecosystems contain ~12% of global soil organic carbon (C) stocks and are located in regions where global climate change will likely alter the timing and size of precipitation events, increasing soil moisture variability. In response to increased soil moisture variability and other forms of stress, microorganisms can induce ecosystem-scale alterations in C and N cycling processes through alterations in their function. We explored the influence of physiological stress on microbial communities by manipulating moisture variability in soils from four grassland sites in the Great Plains, representing a precipitation gradient of 485-1003 mm y-1. Keeping water totals constant, we manipulated the frequency and size of water additions and dry down periods in these soils by applying water in two different, two-week long wetting-drying cycles in a 72-day laboratory incubation. To assess the effects of the treatments on microbial community function, we measured C mineralization, N dynamics, extracellular enzyme activities (EEA) and a proxy for substrate use efficiency. In soils from all four sites undergoing a long interval (LI) treatment for which added water was applied once at the beginning of each two-week cycle, 1.4-2.0 times more C was mineralized compared to soils undergoing a short interval (SI) treatment, for which four wetting events were evenly distributed over each two-week cycle. A proxy for carbon use efficiency (CUE) suggests declines in this parameter with the greater soil moisture stress imposed in LI soils from all four different native soil moisture regimes. A decline in CUE in LI soils may have been related to an increased effort by microbes to obtain N-rich organic substrates for use as protection against osmotic shock, consistent with EEA data. These results contrast with similar in situ studies of response to increased soil moisture variability and may indicate divergent autotrophic vs. heterotrophic responses to increased moisture variability. Increases in microbial N demand and decreases in microbial CUE with increased moisture variability observed in this study, regardless of the soils' site of origin, imply that these systems may experience enhanced heterotrophic CO2 release and declines in plant-available N with climate change. This has particularly important implications for C budgets in these grasslands when coupled with the declines in net primary productivity reported in other studies as a result of increases in precipitation variability across the region.

%B Soil Biology and Biochemistry %V 43 %P 1837 - 1847 %G eng %U https://www.sciencedirect.com/science/article/abs/pii/S0038071711001787?via%3Dihub %N 9 %M KNZ001757 %R 10.1016/j.soilbio.2011.04.020