Burton Lab Warming
Soil Warming in Northern Hardwood Forests
The responses of roots and soil microbes to a warmer environment will impact aboveground productivity and feedbacks to the global C cycle and climatic system.
We are assessing the degree to which temperature acclimation occurs in root systems of a variety of woody plants and determining if such acclimation is a short-term, direct physiological adjustment to warmer temperatures (days to months) or a longer term response to changes in nutrient, moisture and C availability and mycorrhizal status as the ecosystem adjusts to long-term warming (years). Specific questions we are addressing include: Does rapid temperature acclimation occur in roots of large perennial woody plants? How do root biomass, root N concentration, and root respiration rates adjust to long-term changes in soil temperature and moisture and concomitant changes in N availability? How are rates of mycorrhizal infection influenced by the effects of warmer soil temperatures on host C balance and soil N availability? How do the short- and long-term responses of roots and mycorrhizae to warming and associated changes in soil nutrient cycling affect soil CO2 efflux and C availability for aboveground NPP? Are the interrelationships between warmer soil temperature regimes and C fluxes to and from roots and mycorrhizae adequately described by current ecophysiological models? To understand both immediate and long-term effects, plots with 0 to 16 years of warming will be utilized. These include northern hardwood forests at the Ford Forestry Center in Michigan, with warming initiated in September 2010 after a year of pre-treatment measurements and mixed hardwoods at Harvard Forest that have been warmed since 1991, 2003 and 2006.
We are measuring specific root respiration, root N concentration, root biomass, N mineralization, root N uptake, litter inputs, aboveground biomass increment, soil C content and mycorrhizal abundance, community composition and respiration. Treatments at the Michigan location include both soil warming and moisture manipulations, allowing us to examine the interaction of these two important global change factors. During the initial warming in the fall of 2010, it appeared that rapid, physiological acclimation of root respiration did not occur, although drier soil associated with warming did reduce respiration rates. What will be of more importance are the amounts of C allocated to root respiration and mycorrhizal symbiosis that will exist in the ecosystem after N cycling, aboveground productivity, litter quantity, quality and decomposition, and microbial community composition and function have equilibrated to the altered climatic regime. During the next several years we will assess the interrelationships that exist between such processes and determine the factors that will ultimately control soil CO2 efflux and aboveground growth in the altered climate.