Functional feedbacks by dwarf mistletoe of pine into global climate change in a Yellowstone forest ecosystem

Dwarf mistletoe is a defoliating, carbon-sink pathogen that significantly affects host physiology, and nutrient and water relations. This pathogen is forecast to increase in range and severity in response to global climate change due to effects on host tree physiology. Via impacts on host tree photosynthetic capacity, dwarf mistletoe could directly influence soil processes that that are responsible for the release one of the world’s greatest sources of atmospheric CO2. Despite the obvious ramifications for global climate change (GCC) and potential for feedbacks into the process, no studies have been put forth measuring effects on terrestrial ecology and carbon relations. In this study we investigated effects of dwarf mistletoe infection of pines in Yellowstone on soil fungal species and functional diversity, activities of soil enzymes actively involved in woody breakdown (hence having direct impact on carbon sequestration), and soil CO2 efflux. Despite the wealth of knowledge regarding primary effects of dwarf mistletoe on host physiological process, there is virtually no information regarding secondary effects, for example on the organisms that rely upon host photosynthate, and that in turn play pivotal roles in carbon cycling and terrestrial ecology. In this study we provide the first look at these impacts. Results: 1) direct genetic tests indicate significant decreases in soil fungal species diversity and richness; 2) culture-based methods (Fungilogs) indicate a significant increase in the number of carbon substrates utilized by soil fungi (see table); 3) direct measures of soil enzyme activity indicate significant increases in woody substrate breakdown (see table); 4) direct in situ measures of soil CO2 efflux indicate a doubling of CO2 flux from soils (P<0.02) in infected blocks. Together, these results indicate that there are tertiary and quaternary-level feedbacks into the GCC process that result from primary and secondary effects on disease distribution and forest tree physiology. These feedbacks are likely to have significant impact on global carbon budgets, and thus influence rate and magnitude of global climate change.Effects of dwarf mistletoe on soil enzyme activities and functional diversity