Hubbard Brook

Climate change and nutrient cycles in northern hardwood forests

P.I. Peter M. Groffman

This project uses a landscape-scale approach to evaluate three aspects of the effects of changes in snow depth on soil freezing, the processing of C, and N retention in the northern hardwood forest. First, it addresses uncertainty about the occurrence of colder soils in a warmer world, and whether this pattern will decrease N retention in the northern hardwood forest. Uncertainty about the extent and effects of soil freezing in a warmer world is rooted in the difficulty to unveil where snowpacks are too shallow to insulate the soil, and where air temperatures are too warm to freeze the soil. We measured and modeled snow depth, and soil climate across the Hubbard Brook Experimental Forest (HBEF), which encompasses the range of climate variability that has been predicted for the northeastern U.S. over the next 50 100 years. Measurements of soil temperature, moisture and frost, soil solution chemistry and transport and microbial biomass and activity are being made at these sites to explore critical uncertainties surrounding soil freezing events and their effects on C processing and N retention.

This project also addresses how winter climate change affects microbial and soil

invertebrate processes and resultant changes in C flow during winter by testing the hypothesis that C flow is the key integrative regulator of winter microbial activity and that winter climate change effects on this activity are mediated through effects on C flow in dissolved organic carbon (DOC) and particulate organic carbon (POC) derived from the partial decomposition of litter and soil organic matter.

Finally, the project also aims to understand how climate change will affect the soil:atmosphere greenhouse gases exchange, as a potential biological feedback to climate change.

Selected publications:

Durán J, Morse JL, Groffman PM (2012) Comparison of in situ methods to measure N mineralization rates in forest soils. Soil Biology and Biochemistry, 46, 145–147.
Durán J, Morse JL, Groffman PM et al. (2014) Winter climate change affects growing-season soil microbial biomass and activity in northern hardwood forests. Global Change Biology, 20, 3568–3577.

Durán J, Morse JL, Groffman PM et al. (2016) Climate change decreases nitrogen pools and mineralization rates in northern hardwood forests. Ecosphere.

Durán J, Morse JL, Rodríguez A et al. (2017) Differential sensitivity to climate change of C and N cycling processes across soil horizons in a northern hardwood forest. Soil Biology and Biochemistry, 107, 77–84.

Morillas L, Durán J, Rodríguez A, Roales J, Gallardo A, Lovett GM, Groffman PM (2015) Nitrogen supply modulates the effect of changes in drying-rewetting frequency on soil C and N cycling and greenhouse gas exchange. Global Change Biology.

Morse JL, Durán J, Groffman PM (2015b) Soil Denitrification Fluxes in a Northern Hardwood Forest: The Importance of Snowmelt and Implications for Ecosystem N Budgets. Ecosystems, 18, 520–532.

Sorensen PO, Templer PH, Christenson L et al. (2016) Reduced snow cover alters root‐microbe interactions and decreases nitrification rates in a northern hardwood forest. Ecology, 97, 3359–3368.