Cooperative Institute for Research in Environmental Sciences

Russell K. Monson

Research Interests

Carbon balance of forest ecosystems; biological controls over the emission of reactive volatile organic compounds from plants and their influence on atmospheric chemistry

Current Research: Forest Carbon Cycle Studies

For the past 11 years, we have been studying carbon fluxes between forest ecosystems and the atmosphere in the mountains of Colorado. Our aim is to understand the principal controls over, and magnitude of, the exchange of carbon dioxide from trees and soils in forest ecosystems, and their response to interannual climate variation. In the past few years, we have combined tower flux measurement systems and aircraft sampling to conduct these studies. We have shown that these forest ecosystems are highly affected by year-to-year variation in the winter snowpack, which has been diminishing over the past 50 years throughout the western United States. Lower snowpacks cause the forests to be water stressed during the middle of the summer, reducing their productivity, and thus reducing their potential to extract CO2 from the atmosphere. The influence of reduced snowpack is a systematic component of climate change in the western United States, and is expected to continue in the face of future warming trends.

In the past year, we noticed that mountain pine beetles have infected our experimental forest near Niwot Ridge, CO. The beetles have the potential to further stress the forest, and even further reduce the rate by which the forest extracts CO2 from the atmosphere. We have initiated studies of the impact of beetle infection on the cycling of carbon within the soil, and the potential for beetle infections to increase the rate of CO2 loss from the ecosystem. This increased CO2 loss will likely be due to increased death of trees and their associated needles, which will increase the deposition of litter to the soil. We are conducting a series of studies using the stable isotopes of carbon (13C and 12C), to discern rates of soil carbon cycling and its coupling to climate change, and we are using one of the radioactive isotopes of carbon (14C) to determine shifts in the mean age of soil carbon as a result of the beetle infection.

Given the widespread distribution of mountain forests in the western United States, their dominant role in sequestering atmospheric carbon in this part of the country, and stresses such as winter warming accompanied by reduced snow and mountain pine beetle outbreaks, we can expect the terrestrial carbon sink in the western United States to continue to weaken in the future. We are currently trying to adopt methods of model-data assimilation, combined with predictions of regional climate change using general circulation models, to better understand the connections between these stresses and CO2 uptake by these forest ecosystems.

Publications

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Honors and Awards

• Humboldt Fellowship (1990)
• Guggenheim Fellowship (1998)

Russ Monson is a professor at the University of Colorado Boulder.