The dynamics of vegetation in the Rocky Mountains have been altered in the past century by interruption of natural disturbance processes and management treatments. Consequently, many physical and chemical processes (e.g., water, nitrogen, carbon) have been changed due to these practices. For example, fire exclusion generally increased stand density, canopy cover and leaf area index (LAI), which resulted in changes in the water balance, including increased stand-level transpiration and decreased soil water availability, consequent long-term desiccation of forest fuels. Also, there were increases in the magnitude of insect and disease infestation, which when combined with decreased resource availability (water and nitrogen), resulted in increased fuel buildup and in-creased the probability of high-intensity wildfires. Existing measurements of ecosystem condition have failed or been limited in application because they do not incorporate basic metabolic relationships into the evaluation. Here we ask which factors can adequately, reliably and efficiently be used in the development of a risk assessment index to predict the probability of adverse ecosystem functioning and, consequently, increased susceptibility to insect infestation; both factors that lead to undesirable fuel levels? How can managers develop scenarios of vegetation dynamics taking into account ecosystem condition and the potential consequences of management decisions, including inaction?

The objectives of this study are two-tiered; one tier for the site or landscape level and the other for the stand or forest community level. The first objective is to develop a classification system that can be used to estimate and model the biophysical growth potential across the site/landscape level. The biophysical growth potential (BGP) will be based on physical site attributes such as slope, aspect, elevation, and soil morphology; those attributes that affect the site water balance and consequently, the carbon discrimination of the tree species that are growing at the site. The second objective is to develop an index of metabolic functioning that can be used to capture the species differences in assimilation and growth following a disturbance, including restoration management. The index of metabolic functioning (IMF) includes the physiological growth and maintenance of the species, incorporating species-specific photosynthetic strategies.

Research results and data will be incorporated into process-based models of fuel loading (e.g. FIRESUM) and successional state models (e.g. LANDSUM, SIMPPLLE) so that trends in forest function and fuel build-up over time and after management practices and/or fire (prescribed and natural) will be available.

• Tree-ring stable carbon isotopes of Siberian larch as indicators of changing atmospheric CO2 and humidity (PDF)
  
  
• About radiocarbon
  
  
• Stable Isotopes
  
  
• Nearctica - Native Conifers of North America

• Tenderfoot Creek Experimental Forest
• Coram Experimental Forest
• Reimel Creek in Bitterroot National Forest near Sula
• Pleasant Valley in Kootenai National Forest on Plum Creek Land

Click on each thumbnail photograph for an enlarged version.

A typical site used in our research; this site was disturbed 25 years ago by logging.

The distant mountains depict a mosaic of different stands.

The site at Coram Experimental Forest; the western larch trees are clearly visible as the lighter green trees.

Field technicians using the Li-Cor 6400 to determine physiological variables such as photosynthesis, vapor pressure deficit, and stomatal conductance.

Using the Li-cor in a more open forest, due to a fire disturbance several years before.

A stand containing several study sites.

A field technician using a gun to detach branch samples from the trees.