A Guest Post by Dr. Zander Evans
JFSP recently released the latest
in its series of fuel treatment syntheses that covers the mixed conifer forests
of California, Central and Southern Rockies, and the Southwest. The southern
mixed conifer fuel treatment syntheses uses nearly 380 scientific articles,
agency reports, and other references to answer questions about historic
conditions, fire regimes, the impact of altered fire regimes, fuels treatment effectiveness,
and treatment impacts. A central goal for the guide is to combine existing
peer-reviewed literature and information gathered from dozens of interviews
with managers.
The synthesis highlights the
importance of heterogeneity in mixed conifer forests. Pre-settlement fires in
mixed conifer forests burned on intervals that averaged between eight and 25
years for the Sierra Nevada, Southern Rockies, and Southwestern mixed conifer.
Low-severity fires were more frequent in some mixed conifer forests; but, in
general, mixed conifer forests have historically tended to be heterogeneous
mixtures in which species composition, forest structure, and fuel loads change
over short distances. Since the late 1800s, logging, fire suppression, road
building, and livestock grazing have reduced the frequency of fire and increased
tree densities-resulting
in more homogeneous forests.
Currently, many fuel treatments
seek to restore heterogeneity, i.e., the mosaic of openings and stands of
varying densities across the landscape. Rather than just removing trees to
create evenly spaced crowns, managers are experimenting with creating gaps and
openings to change fire behavior. Innovative managers are creating more
landscape heterogeneity by implementing prescribed burns across large mixed
conifer forests, such as early season prescriptions using aerial ignition to
burn upslope where remaining snow can control the fire. Of course fuel
treatments are also designed to reduced wildfire hazard and in most mixed
conifer forests, thinning that treats both the canopy and understory (crown and
low thinnings) combined with prescribed fire is the most effective way to do
that.
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| Stephens Lab | University of California Berkeley |
However, land management objectives or external constraints can make
other tools, such as mastication or prescribed fire alone, more appropriate. Treatments
must be maintained for their fuel reduction effect to be sustained, and no
single treatment will reverse a long history of fire exclusion. The synthesis also discusses numerous
complications and barriers to implementing fuels treatments in mixed conifer
forests such as smoke management, wildlife habitat protections and retirement
of experts, that can make these treatments more complicated, though not
impossible.
We hope you find this guide
useful, and look forward to your feedback.
