Fire exclusion and suppression policies across western landscapes in the United States and Canada over the last 70 years have resulted in excessive accumulations of surface fuels. Without a heterogeneous pattern of lower-intensity fires occurring over regular historical intervals, these surface fuels build up and increase the likelihood of uncharacteristic, very large, and potentially severe wildland fires. Government land management agencies are advocating extensive fuel treatments and ecosystem restoration activities to reduce the possibility of severe and intense wildfire that could damage ecosystems, destroy property, and take human life.
Knowledge of fuel litterfall and decomposition rates before and after fuel treatments could help managers prioritize, design, and implement more effective fuel treatment programs. However, these litterfall and decomposition rates remain relatively unknown for many ecosystems.
In this study, the rates of deposition and decomposition were quantified for six surface fuel components across major forest types in the Northern Rocky Mountains. These rates were used to estimate fuel dynamics parameters in complex landscape models of fire and vegetation dynamics.
Fuel litterfall was measured for more than 10 years with semi-annual collections of fallen biomass sorted into six fuel components (fallen foliage, twigs, branches, large branches, logs, and all other material). This litterfall was collected using a network of seven to nine, 1 m2 litter traps installed at 28 plots established on seven sites with four plots per site. Decomposition was measured using litter bags installed in three sets of three bags each on five of the seven sites and the bags were monitored for biomass loss each year for 3 years.
Deposition and decomposition rates weresummarized by plot, cover type, and habitat type series. Foliage litterfall rates ranged from 0.057 kg m2 on the dry Pinus ponderosa stands to 0.144 kg m2 on mesic Thuja plicata stands, while foliage decomposition k values ranged from 0.085 to 0.283 along a moisture gradient. Fallen foliage and fine woody fuel (twigs, branches) tended to be more homogeneously distributed than large woody fuel (large branches, logs) across the traps and across each year of the 10+ year study.
Spatial and temporal properties of both litterfall and decomposition were also evaluated.
Data product available through the Forest Service Data Archive, including 11 years of surface fuel litterfall and decomposition from 28 plots that represent a number of major forest types that span a wide range of biophysical environments in the northern Rocky Mountains.
Todd Carlson, Kirsten Schmidt, Wayne Lynholm, Courtney Couch, Laurie Dickinson, Myron Holland, Curtis Johnson, Micha Krebs, Eric Apland, Daniel Covington, Amy Rollins, and Ben McShan, and Ceci McNicoll.