Roots Mediate the Effects of Snowpack Decline on Soil Bacteria, Fungi, and Nitrogen Cycling in a Northern Hardwood Forest

Photo: Root ingrowth cores were made out of nylon mesh (2-mm mesh size) which allowed roots to grow into and colonize the soil core. Root exclusion cores were made out of finer-sized nylon mesh (50-µm mesh size) that prevented root colonization.

Rising winter air temperatures are reducing seasonal snow cover in many temperate ecosystems, but the role of plant roots in moderating the impact of snowpack loss on bacterial or fungal communities remains poorly resolved. This study showed that declining winter snowpack and impacts to plant roots have direct effects on the diversity and abundance of soil bacteria and fungal communities with important consequences for N cycling in northern hardwood forests.

Summary

Impacts to soil biogeochemical processes have been investigated as they pertain to climate induced warming, with temperature increases having impacts on snow-dominated systems including reduced snowpack and early onset of melt. Little work to date has focused on the role that roots play in enhancing or moderating nutrient cycling in soils by bacteria and fungi. To address this gap in knowledge, root ingrowth and exclusion cores (216 cores total) were incubated in situ for 29 months at the Hubbard Brook Experimental Forest in central New Hampshire (USA) that has experienced winter snowpack decline over the past 50 years. Both a declining winter snowpack and its effect on plant roots each had a direct effect on the diversity and abundance of soil bacteria and fungal communities and interacted to reduce rates of soil N cycling in this northern hardwood forest. Such results are thought to be broadly relevant to other temperate ecosystems where climate change and climate disturbance are impacting snowpack, such as many mountainous regions worldwide.

Citation

Sorensen, P. O., J. M. Bhatnagar, L. Christenson, J. Duran, T. Fahey, M. C. Fisk, A. C. Finzi, P. M. Groffman, J. L. Morse, and P. H. Templer (2019), Roots Mediate the Effects of Snowpack Decline on Soil Bacteria, Fungi, and Nitrogen Cycling in a Northern Hardwood Forest, FRONTIERS IN MICROBIOLOGY, 10, DOI: 10.3389/fmicb.2019.00926.