Fungal Response to Multiple Global Change Stressors: Evidence from Long-Term Manipulations and Environmental Gradients
Stephanie N. Kivlin1,2* (firstname.lastname@example.org), Aimee Classen2,3, Lara Souza2,4, Jennifer Rudgers2,5, Hannah Shulman1,2, Jessica A. M. Moore2,6, Ruth Simberloff1,2, Marissa Huber1,2, Diane Campbell2,7, David W. Inouye2, Heide Steltzer2, Patrick Sorensen2,8, Eoin Brodie2,8, Benjamin Sulman2,9
1University of Tennessee, Knoxville, TN; 2Rocky Mountain Biological Laboratory, Gothic, CO; 3University of Michigan, Ann Arbor, MI; 4University of Oklahoma, Norman, OK; 5University of New Mexico, Albuquerque, NM; 6Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN; 7University of California, Irvine, CA; 8Earth and Environmental Sciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA; 9Biological and Environmental Systems Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN
Global change is affecting terrestrial ecosystems in multiple ways. In mountain ecosystems, direct effects (i.e., raised soil temperatures) and indirect effects (i.e., early snowmelt, decrease in snowpack) of warming are co-occurring. The ability to forecast belowground responses to these complex global change drivers has been hindered by a lack of long-term studies. Yet, these belowground studies are vital as soil fungi are key decomposers in terrestrial ecosystems, potentially flipping soils from carbon sinks to carbon sources. Here researchers examined soil fungal responses (composition and abundance) to a 29-year-long warming experiment and a 4-year-long early snowmelt manipulation at the Rocky Mountain Biological Laboratory in Gothic, CO in 2019 to 2021. The team used complementary approaches by pairing experimental data with those collected the same year from nearby environmental gradients in temperature (i.e., elevation) and snowmelt date (i.e., at different slopes and aspects). Environmental gradients capture long-term ecological and evolutionary variation but can be confounded by many covarying abiotic and biotic factors. Experiments allow researchers to understand the role of a specific global change driver but may not occur over long enough time periods to capture both ecological and evolutionary responses.
Soil fungal communities varied substantially in response to abiotic environmental gradients. Up to 8% of the variation in fungal composition was explained by elevation (a long-term proxy for temperature) and 15% of variation in fungal composition was explained by aspect (a long-term proxy for snowmelt date). Snowmelt date in the collection year explained an additional 10% of variation in fungal composition. Experimental treatments affected fungal communities less.
Experimental early snowmelt explained 6% of the variation in fungal communities whereas warming only explained 4% of the variation in fungal communities. Fungal abundance followed similar trends with hyphal lengths varying the most by elevation and aspect and the least in experimental manipulations. Overall, the results suggest that fungi are more sensitive to historical and contemporary snowmelt date (which varies by 56 days since 1975) than the direct effects of warming per se. Because fungal response to snowmelt is strong, and snowpack and melt dates are highly variable, future ecosystem models may be improved by including fungal functions across the transition in snow cover. Future research in the group is focused on comparing plant, fungal, and biogeochemical phenology in response to snowmelt date.