The Forest Ecosystem - Mountains and Plains: The Ecology of Wyoming Landscapes - page 213

Fig. 12.13. Predicted long-term trends
in coarse wood after natural fire (top)
or clearcutting (bottom) in lodgepole
pine forests. time progresses from left
to right in these diagrams. natural
fires have occurred at centuries-long
intervals in these forests. thus, only a
single disturbance is shown in the top
panel. the bottom panel depicts a 100-
year clearcutting rotation, illustrating
how repeated harvest leads to a gradual
depletion of large pieces of wood (more
than 3 inches in diameter) and possibly
to changes in the amount and charac-
teristics of soil organic matter. Adapted
from tinker and Knight (2004).

Fire

Coarse wood created
by disturbance

Pre-disturbance
Coarse wood

Coarse wood added
by developing stand

Initial Clearcut

Coarse wood created
by disturbance

Pre-disturbance
Coarse wood Subsequent clearcuts

shrubs and forbs, which usually takes 1-4 years . 49 A fter
a fire, many nutrients formerly tied up in the living and
dead biomass exist in the form of ash, which can be car-
ried away by water and wind; some are lost in smoke as
well. Warmer daytime soil temperatures resulting from
removal by fire of the cover of insulating litter also
stimulates soil microbial activity, including the bacteria
and fungi that decompose dead roots and other organic
matter, thereby accelerating nutrient release. thus, the
potential exists for considerable nutrient loss after a fire.
in contrast, aside from nutrients lost by erosion along
roads, the nutrient loss from harvesting is more likely
to be less than that following an intense fire, simply
because the harvested wood has surprisingly little nutri-
ent content compared to the slash that is left behind.
Unless the slash is piled and burned, the nutrients in

the slash are released slowly during decomposition,
reducing the likelihood of nutrient losses to streamflow.
Some of the most important differences between
clearcutting and fire have to do with the dead trees left
by fire—the same trees that would have been harvested.
Dead standing trees provide habitat for many organisms
long after the fire.50 . 50 A lso, over the long term, the addi-
tion of wood fragments to the soil enhances nutrient
availability and water-holding capacity and creates an
important substrate for microbial organisms. As com-
monly noted, the character of forest soils today is par-
tially the result of organic matter additions from wood
and leaves over the past 10,000 years or more (fig. 12.13).
Some wood is lost to periodic forest fires, but between
fires wood-derived organic matter gradually accumu-
lates. clearcutting interrupts these inputs, especially if