Agriculture Reference
In-Depth Information
invertebrates such as fleas that would invest homes, weevils that would attack
acorn crops, or grasshoppers, which were too hard to capture without fire.
Landscape-level impacts were produced by their management goal of wanting to
open up, or entirely type convert, dense shrublands to annual forbs and grasses.
This landscape change increased seed resources and created a major food source in
many parts of the region. This change also improved travel and reduced attacks
from grizzly bears and competing Native Americans. Ideally, total elimination of
shrublands may not have been a goal since retention of some wood resources
would have been desirable for cooking fires. However, these native shrublands by
and large are not resilient to the continuous onslaught of fires and eventually are
type converted to annual herbaceous associations.
Although use of repeated burning to convert shrublands to grasslands was a
well-developed management technique in Spain, there are relatively few reports of
this practice by European colonists in California. Possibly the prior burning by
Native Americans had opened up much of the landscape to grasslands and thus
there was less incentive for further type conversion of shrublands and woodlands.
However, this eventually changed as resource competition by the burgeoning
California population experienced increasing limitations to livestock grazing and
need for more rangeland in the late nineteenth century (Burcham
1957
).
Contemporary Management
The chaparral crown fire regime and the montane forest surface fire regime have
very different characteristics and require very different fire management appro-
aches. Despite the fact that both have been managed under the same fire suppres-
sion policy for the last century, the outcome has been radically different. Fire
suppression policy has been highly successful at excluding fire in forests but
largely unsuccessful at excluding fire in chaparral.
Fire suppression has been highly effective at excluding fire in forests because the
surface fire regime is conducive to rapid fire suppression. Surface fuels generate
shorter flame lengths that can be effectively suppressed by fire fighters. Many of
these fires are ignited by lightning during moderate weather conditions not con-
ducive to rapid fire spread and the wind resistance created by dense forests reduces
rates of spread. As a consequence, fire management agencies have been extraor-
dinarily successful at excluding fires from these environments for over a century.
One consequence of fire suppression is that surface fuels as well as ladder fuels
have accumulated to levels far in excess of historical conditions. The primary
concern is that higher fuel loads will spread fire from the surface to the canopy and
will lead to crown fires of much greater extent than historically occurred. In other
words the gap size to be expected by mixed surface and crown fires will become
much larger as a result of historic fire suppression and buildup of fuels (
Fig. 5.9
).
This not only increases fire hazard but has negative resource impacts such as the
reduction of parent seed trees, making regeneration more precarious.
