Quantifying the effects of disturbance and subsequent successional processes on the exchange of energy, water, and nutrients between the land surface and atmosphere is central to many disciplines in ecology. The importance of such studies will only increase as the human population increases and disturbances increase in frequency (Vitousek et al. 1997). Boreal forests are the second largest forest biome in the world and contain approximately the same amount of carbon in the soils and vegetation as carbon in the atmosphere. About 5 million hectares of boreal forest burn each year, however, and in recent years this value exceeded 18.5 million hectares (Goldammer and Furyaev 1997). A mechanistic understanding of the effects of fire on the structure and function of boreal forests does not exist, prohibiting even a precursory use of ecosystem process models to quantify the effects of fire on the carbon budget of boreal forests.

The three major objectives of this study are as follows. (1) Quantify the effects of wildfires on the microclimate, structure, and function of successional boreal black spruce forests in northern Manitoba, Canada, and compare these results to other boreal forest age-sequence studies. We will use integrated ecophysiological, biogeochemical, isotopic, and micrometeorological field measurements to improve our understanding how individual processes change during succession, and the eddy flux approach to quantify how whole-system energy, water and carbon dioxide (CO2) exchange between a black spruce ecosystem and the atmosphere change during succession following fire. The suite of measurements will be replicated in seven different-aged black spruce stands comprising an age-sequence distributed across the former BOReal Ecosystem Atmosphere Northern Study Area (BOREAS NSA) near Thompson, Manitoba. (2) Quantify active and past aerial extent of wildfires for North American boreal forests using current (AVHRR, Landsat-7) and future (MODIS) satellite-borne sensors, and determine if hypothesized earlier growing season "green-up" by vegetation caused by warmer soil temperature in recently disturbed forest can be detected using MODIS. (3) Use two terrestrial ecosystem models (IBIS and TEM) and spatially explicit fire extent values obtained from satellite-borne sensors to examine the possible effects of fire on exchange of CO2 between the North American boreal forest and the atmosphere. Model simulations will be compared to field data at a range of temporal and spatial scales.

The proposed study qualifies as an integrative research challenge in environmental biology research for several reasons: (1) it uses past and ongoing field measurements made by PI's during BOREAS to address a critical, and unanswered, ecological question (2) uses complementary measurements from many disciplines (ecophysiology, ecosystem ecology, meteorology, soils, geosciences, landscape ecology, atmospheric science, and global ecology) to address a fundamental question in ecology that is relevant to global change; (3) it employs a suite of measurements that will enable us to simultaneously determine the effects of disturbance on individual carbon cycling processes and whole ecosystem net exchange which will provide standardized, independent estimates of NEE; (4) it establishes critical linkages with other scientists measuring the effects of fire on select components of the carbon budget of boreal forests of contrasting climate, dominant vegetation and importance of permafrost; (5) it establishes collaboration with scientists creating historic fire record and monitoring current fire status; and (6) it contributes to the development and implementation of fire mitigation strategies for land managers, (7) it will facilitate the training of undergraduate and graduate students in boreal ecology, and provide very badly needed basic forest ecology and management training to the Nelson House First Nation Cree Indians.