ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

What is the significance of 54,000 years? In that time span, there will be
geologic change, speciation, glaciation, climatic change, migration and a host of
other dynamic events which no land manager can anticipate. We cannot manage forest
much beyond 1 or 2 rotatians, so that a remaining Biological Life of 50,000 years,
although statistically significant, is of no concern to a land manager except where
the remaining life is less than 200 years on some poor tropical soils. Measurement on
site of the surface downslope movement of solids using land weirs showed that it would
take about 50,000 years to erode away the present root zone through microerosion
associated with 50-year burns on this coarse-textured soil ,
Rutrient shock or temporary nutrient depletion is a more realistic concern on
these Montana soils than is the loss of long-term productive capabilities. The soils
studied are low in total calcium, and relative to the total Ca content, calcium losses
below the root zone of the maturing forest are quite high. The north slope is cold
and decay is slow. Too much burnlng, or too much harvest could deplete the soil-plant
system of its readily available calcium producing nutrient shock, or temporary loss of
the ability of this soil to grow trees. Nutrient shock can be recognized by low
available levels of 1 or more biologically essential nutrients in the soil, and
stunted seedlings or brush fields. It does occur in the Rocky Mountains and should be
a major concern to land managers in planning harvest and regeneration strategies.
There should be at least 8,000-10,000 meq/m2 of calcium to grow the next forest, and
3 x that much to avoid drawing on nutrients released through weathering. Understand-
ing hob/ much nutrient one soil can store after fire was not enough.
Out of this study came a study of the nutrient retention capabilities of a wide
range of texturally different soils. It was the intention of this study to develop a
system to predict how much of each nutrient in ash could be held by the root zone
before massive nutrient losses would occur below the root zone. Such losses in a
mature forest below the root zone are permanent and irreversible. A land manager who
is uncertain of the ability of a soil to hold biologically essential nutrients should
be able, wlth 1-6 simple measurements to predict how many total cations in meq/m2 of
surface area can be added through ash (or fertilizer) before substantive losses will
occur. If the storage capacity of the soil is low, and the available or total nutri-
ent storage is low, the land manager may want to select fuel loadings, air tempera-
tures, fuel moisture, and wind conditions which will affect a 50% fuel reduction or
other appropriate fuel reduction to avoid overloading the soil , A1 ternatively , this
method will allow the land manager to select an appropriate fertil izer level to avoid
excessive cost and losses to ground water or streams (Stark, in press)
i'
This study on nutrient retention is 'ust in completion. The storage capacity for
most of 8 cations can be predicted with R values of 0.7 to 0.9 using 1 to 6 independent
variables. Total cation storage can be predicted with R2 of 0.69-0.96 and %
standard error of the Y of 12.5-28.7 % for 28 soils. With the perfection of the
prediction of fire behavior in different fuel types, weather conditions, and fuel
moisture contents, it will soon be possible to couple these two approaches and use
fire in a more dependable and ecologically sound manner.
THF INFLUENCE OF FIRE AND LOGGING ON NUTRIENT CYCLING
These studies in Douglas-fjr/western larch forests at 1,219 m (4,000 ft, ) elevation
on slopes of >4.OX were desl'gned to deternine if logging and slash disposal would
result in nutrient losses below the root zone or to the stream, and through harvest.
Several habitat types occurred in the areas, but the predominant one was PSMEIVACA
(Pfister, et al. 1977). The soSls are 40-50 cm (15.7-19.6 in) deep, often underlain
by low-qua~t~limestone or argillite, and in places they are andeptic. The annual
precipitation is 763 mm (30 in), with approximately one-half coming as snow.