ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

if the forest floor is completely consumed (Campbell 1961 ), and "fuel reduction
fires" of low intensity substantially reduce populations of forest floor fauna (Leo-
nard 1977). In African soils, burning destroys populations of termites and results
in impoverishment of these tropical soils (Reichert and Reeder 1972).
Although most groups of macrofauna are reduced by fire, in some instances, prescribed
burning, often in prairies and grassland, increases arthropod density and
biomass. Following a prescribed burn in a grassland area (formerly a pine-hardwood
forest), populations of herbivores (phytophagous) increased, presumably as a result
of an increase in the food supply; at the same time, other groups such as predaceous
spiders, flies, and scavengers showed less response to burn ing (Hurst 1970).
There are at least three reports of grasshoppers being more numerous in burned
than unburned areas. In the northern Rockies, Clayton (1975) found the orthopteran
family Acrididae to be more numerous in burned than in unburned coniferous forests,
and Hurst (1970) reports grasshoppers to have increased in numbers after prairie and
grassland fires. In a northern Minnesota jack pine burn, grasshoppers increased
after a fire, possibly due to recolonization from adjacent unburned forests or from
survival in patches of unburned ground (Ah1 gren 1974). This recolonization from
without or repopulation from within burned areas could be a very significant behavioral
mechanism regarding the long-term effects of fire on forest floor macrofauna.
There are some interesting evol utionary adaptations and imp1 ications among some
groups of insects surviving fires or inhabiting or recolonizing burned areas. In
Montana, Clayton (1 975) coll ected grasshoppers from burned and unburned areas, ranked
them from dark to light and determined that out of 60 specimens, the 20 most darkest
were from the burned area. Several investigators have reported melanistic forms of
grasshoppers and other orthopterans, pentatomid bugs and noctuid larvae to inhabit
burned areas in African savannas (Reichert and Reeder 1972). Many species of rodents
and birds in grassland fire environments have color patterns that harmonize with
burned or partially burned yegetation. Such camouflage is useful to these species,
since some predators seem a1 so to be adapted to fires, and will congregate at fires
to feed on prey animals previously out of sight in the grass (Stoddqrd 1963; Komarak
1969).
RESEARCH ON IMPORTANT ARTHROPOD GROUPS
Of the fprest floor macrofauna influenced by hqrvesting residue and fire management
practices, at least three orders of arthr~pods deserve special attention because
of their feeding behavior or their response to silvicultural or residue treatment.
They are: Coleoptera (beetles), Hymenoptera (.main7y ants), and Arqneida (spiders).
Col eoptera
Of a11 the forest floor rnacrofauna, the beetles are probably the most abundant.
Two to four families usually predominate. In a study of soil invertebrates in two
aspen forests in northern Minnesota, Wagner and others (-1 977 1 c ~ 1 ected l 22 famil ies
of beetles in the soil 1 itter environment. The numerically dominant taxa were rove
beetles (Sta hyl idnidae), ground beetles (~arabidqe) , cl ick beetles (Elateridae) ,
and soldier g eetles (Cantharidae). In a recent study in Montana (Fellin 1980b),
carabids apd staphyl inids were the predominant fami 1 ies.