|
|
Woodland NOTES
- Vol. 15, No. 1 - Fall/Winter, 2003-2004
In this issue:
 |
|
|
|
Woodland
NOTES Celebrates 15th Year in Production
Woodland NOTES, which began as a one-page mimeographed
handout, is now an award winning peer-reviewed publication enjoyed by
over 10,000 readers per issue. Over the years we have written about all
aspects of forestry and forest management, stewardship, wildlife, soils,
and water. We have given you information on how and when to plant a
tree, fertilize, thin, prune, or burn your forest, keep fish or birds
alive over the winter, measure a log, control weeds, wildlife, and water
quality, sell your forest products, and identify, prevent, and control
insect and disease problems. And we still haven’t told it all!
This year we will continue to address a wide variety of
topics, from fire to fungi. We thank you for readership and hope you
continue to enjoy Woodland NOTES for another 15 years!
|
Mycorrhizae – the friendly forest fungi
Chris Schnepf
Many forest owners do not immediately see fungi as a
beneficial organism. If you have seen patches of fir dying cancerously
from root disease or learned about the profound effect white pine
blister rust has had on north Idaho’s forest ecology, it may be easy to
forget that the majority of forest fungi do not kill trees.
You probably know that microbes inhabit your stomach and
other parts of your body, performing beneficial roles (e.g., helping you
to digest food). Most of us could not name any of these if asked. There
are also a whole host of relatively unknown microbes and fungi that help
trees by recycling forest nutrients, decomposing slash, and improving
soil, to list a few of their positive functions. Some suggest that even
tree-killing fungi (the native ones, at least) perform a positive role
by taking out trees that are poorly adapted to a forest site.
One of the groups of fungi that most directly benefit
tree growth is called mycorrhizal fungi. Mycorrhiza is translated
from Latin as "fungus root". These fungi enter the roots of trees and
other plants and form a symbiotic relationship (a relationship in which
both the host and the fungi benefit). Mycorrhizal fungi get carbon (the
product of photosynthesis) from trees and the trees get a larger
effective absorbing root surface (more nutrients and moisture) from the
hyphae (the fungus equivalent to roots) and mycelia (matted hyphae) of
mycorrhizal fungi. In addition to rooting capacity, mycorrhizae can
also:
-
provide reservoirs for nutrients that might
otherwise be leached from the soil;
-
physically block pathogenic fungi access to tree roots;
-
help "unlock" soil nutrients (convert them into forms that can be
used by plants);
-
exude or decay into substances that act as "organic glues", helping
to aggregate soil particles and improve soil structure;
-
move nutrients and photosynthate (carbon) between trees (they can
even move materials between different tree species, where the same
fungus is capable of associating with multiple tree and shrub
species);
-
exude antibiotic substances that deter root pathogens; and
-
provide food for "fungivores", organisms ranging from ants to deer,
that feed on mycelia or fruiting bodies of forest fungi.
Mycorrhizae
are essential for good growth on many tree species, particularly on
nutrient-poor or droughty sites.
Mycorrhizal
fungi form relationships with over 95% of the plants on earth, and there
are many, many different species. Over 2,000 fungi have been reported to
form mycorrhizal relationships with Douglas-fir alone! Mycorrhizae are
separated into two general types. Ectomycorrhizae cover the
outside of rootlets, just penetrating the rootlets’ outer cells.
Endomycorrhizae do not form a sheath over rootlets. Instead their
filaments grow deeper into the rootlets and out into the soil.
Ectomycorrhizal fungi are the most common. If you have ever seen plants
grown hydroponically, you may have been struck by the many small root
hairs. If you dig up seedlings in the forest, you may notice that the
roots look a little thicker than those hydroponic roots – that is
because they are covered, to some degree, by ectomycorrhizal fungi.
Mycorrhizal fungi produce many different kinds of
fruiting bodies. Some are above-ground mushrooms. For example, golden
chanterelles (Cantharellus cibarius) are the fruiting body of a
mycorrhizal fungus. Other fruiting bodies are underground (e.g.,
truffles).
There has been a large amount of research on forest
fungi that kill trees. There has been much less research on forest
mycorrhizal fungi (even less on fungi that decay downed logs, etc). The
amorphous nature of forest fungi often makes them difficult to pin down
and do precise experimental research in a forest setting. So, with the
standard academic caveat of "we need more research", here are a few
general principles you can apply on your forest regarding mycorrhizal
fungi:
There is usually no need to add mycorrhizae to
well-established forest sites. Native forests are usually
well-stocked with native mycorrhizal species. However, trees planted
to non-forested areas such as agricultural fields or dramatically
altered sites (e.g., a reclaimed mining area) may very well benefit
from mycorrhizal inoculation. Some hardwood nurseries in the eastern
U.S. have actually inoculated seedlings with mycorrhizae in
anticipation of their being planted in farm fields.
Leave more coarse woody debris distributed
across the site. Coarse woody debris (wood larger than 3 inches
in diameter) helps mycorrhizae because as it decays into the soil it
provides better soil moisture for the fungi, particularly during
drought periods. Ideally, woody debris from Douglas-fir, pines and
larch is best because it decays with ‘brown rots", leaving debris
products that last longer than those left by "white rots" which
typically decay true firs or hemlock. You don’t have to leave a lot
of material — typically 1-2 cull logs left per acre are adequate (to
estimate how many tons of coarse woody debris you have, see a
previous Woodland Notes article entitled Tons of Slash,
available online at www.cnr.uidaho.edu/extforest/Vol14,No1.htm.)
Minimize compaction and soil disturbance.
Compaction reduces pore space in soils. Pore space provides the air
that tree roots need to draw the moisture out of the soil. Many
scientists also believe that compaction and excessive soil
disturbance impairs the growth of beneficial forest fungi, including
mycorrhizal fungi. Soil compaction can be quite variable by the type
of soil, time of the year, type of equipment, and care of the
operator using the equipment. Operating on snow or when soils are
dry and limiting equipment to designated trails will help minimize
soil compaction. For more information, see an Oregon State
University Extension publication titled Soil compaction on
woodland properties (OSU EC 1109).
Mycorrhizal fungi play a fascinating role in our
forests. If you would like to learn more about these fungi and research
being conducted on them, check the web site of the USFS mycological
research team at http://www.fs.fed.us/pnw/mycology. In addition
to useful links to ongoing research on mycorrhizal fungi, the web site
also includes photos of mycorrhizal fungi and their fruiting bodies,
publications on mycorrhizal fungi, and links to other sites on these
fungi.
|
Do I
still believe in landscaping for fire prevention?
Ron Mahoney
On July 30, 2003, our Moscow Mountain home, shop, and
5-acre forest property burned to the ground in a human-caused wildfire
that covered 200 acres and consumed 4 other homes. It was 98 degrees
that day, with about 5% humidity and a 10 mph wind when the fire
started. We had done many of the things we advise in our popular
publication Landscaping for Fire Prevention. We had a
large area of gravel and grass around the home, a circular turnaround
that could accommodate large trucks and fire engines, and had thinned
and maintained most of our timbered 5-acres. Since the fire, I have been
asked many times if I still believed in these practices. My answer is an
absolute YES. Here is why.
It gave us a chance. Initially, the fire approached
our property burning into the wind. We were able to stop and hold it at
the line along the lawn and gravel areas, using only a garden hose.
Likely, the fire would have stopped on its own at those boundaries, as
there was no additional fuel for over 100 feet and the light winds were
blowing the heat back into the fire. At this point, a rural fire truck
was also on site and the driver told me he would come back because he
had adequate space to turn around quickly and escape if necessary.
It helped slow down the fire and gave firefighters and
our neighbors a chance to save other homes and properties. When the
fire stopped at the edge of our defensible space, we thought we were
safe. Then, just as the fire truck ran out of water, we heard a roar.
The fire had jumped the road below us, and now came charging up the
slope, this time with the wind. Trees, including some large pines pruned
up to 30 feet, were exploding into flame eighty feet or so in front of
the rapidly advancing fire. The heat was so intense that the fire
ignited our buildings without any flame reaching them first. As this
happened, I could see the fire-retardant tanker planes and helicopters
suspending large bags of water approaching on the horizon. We were
defensible, but the conditions that day didn’t give the defenders enough
time to save our home. However, our open spaces, thinned and pruned
trees, and ability to halt the fire on its initial front, may have
helped save our neighbor’s home. I also believe that it gave the superb
group of firefighters the small edge they needed to stop the fire at
only 200 acres. We all feared it would consume all of Moscow Mountain
and perhaps thousands of additional acres east of our area.
Under less severe conditions, I believe the fire hazard
reduction measures we took would have saved our home. Under the
conditions that day, the potential fire damage was only thwarted by the
well-trained and equipped firefighters from local and state agencies,
private forest industry, and logging companies that responded with
incredible courage and skill.
|
Wildfire and Wildlife: Living in Fire-Based Ecosystems
Yvonne Barkley
Many people believe that all wildlife flee before the
flames of a fire like the animated characters in the movie Bambi.
Contrary to this belief, during the 1988 burns around Yellowstone Park,
animal behavioral scientists didn’t observe large animals fleeing the
fire; to the contrary, most seemed completely indifferent even to
crowning fires. Bison, elk, and other ungulates grazed and rested within
sight of flames, often 100 yards or less from burning trees. Smaller
mammals and most birds that left their habitat while it was burning
returned within hours or days.
An animals ability to survive a fire depends on their
mobility and on the fire’s uniformity, severity, size, and duration.
Large animals die most often in very large, active fires with wide
flaming fronts, active crown fires, and thick ground smoke. For example,
most of the large animals killed in the Yellowstone fires of 1988 died
of smoke inhalation. Animals with limited mobility living above ground
are most vulnerable to fire-caused injury and mortality. Animals that
live in moist habitats, such as amphibians, are least likely to be
affected. Season is also important with burning during the nesting
season being the most damaging.
Fire most commonly affects wildlife by modifying the
proportions and arrangements of habitats across a landscape. Wildlife
habitats are not static, but evolve in response to fire and the
subsequent changes in vegetation and structure that follow a fire.
Immediately after a fire food and shelter are temporarily lost. Hidden
runways and burrow openings become exposed and predation increases.
Particular successional stages or structures are
important to many wildlife species when looking for a place to hide,
escape to, or reproduce in. Species will immigrate to new areas when the
food and cover they require are not available after a burn. The time it
takes for a particular species to return to an area will depend on how
much fire altered the habitat structure and food supply. Wildlife
populations can shift from species that require cool, moist conditions,
such as warblers and wood mice, to species that require warm, dry
conditions, such as ground squirrels and quail. Unburned areas adjacent
to burned areas create a mosaic, increasing wildlife choices from a
range of habitat structures and conditions. Herbivores and species that
prefer herbaceous vegetation for cover prefer early successional, grass/forb
habitats or broad-leafed seedlings that establish after a burn.
Depending on the vegetation type, burning often increases or improves
wildlife forage from a few years to as long as 100 years. Sometimes, the
nutritional content and digestibility of plants increases for a few
years. Dead wildlife becomes food for scavengers, including grizzly and
black bears, wolves, coyotes, bald and golden eagles, crows, and ravens,
and fire-killed trees become food for millions of insect larvae (and the
animals that feed on them) and provide perches for raptors.
As succession continues, conifers succeed broad-leafed
trees, which become snags and add to dead wood accumulating on the
ground. Snags and downed logs provide important habitat for cavity
nesters, small mammals, and even large mammals like bears. Openings
created by downed and dead trees are invaded by shrubs and saplings.
When interspersed with dense patches of shrubs and trees in
long-unburned areas, openings provide excellent food and cover for deer
and elk. By suppressing fire, this mosaic of disturbance-born habitats
succeed to forests, and wildlife species dependent on early and
mid-successional stages move away.
Invertebrate populations tend to decrease after a fire
because eggs, food supplies, and/or shelter are destroyed. Flying
insects are especially vulnerable because they are attracted to fire by
heat or smoke and are incinerated in great numbers. Surface insect
populations, such as grasshoppers, also tend to decrease. Other insect
populations, especially bark beetles and wood borers, increase after a
fire, as trees damaged or killed provide large amounts of suitable
habitat. Ants also tend to increase after fires and can eat large
amounts of seed. Soil dwelling and aquatic invertebrates generally
suffer little immediate damage, though indirect and long term effects
are less understood or unknown. Earthworms generally live 4-8 inches
under the soil surface and are probably protected from the direct
effects of heating. Amphibians and reptiles avoid direct effects of fire
by either moving away from it or burrowing into the soil.
Wetlands are less likely to burn, and when they do, are
burned less severely than upland sites. Wetlands provide a refuge from
fires for many wildlife species and activities such as breeding by
aquatic species may be carried out with little interruption. Although
fire in wetland areas usually increases open water and stimulates
vegetation favored by many aquatic and semiaquatic species, removing
adjacent riparian habitat can cause problems. Riparian vegetation shades
wetland habitats and vegetative root systems hold the soil and prevent
or decrease deposition of sediment into the water. When riparian plants
are removed, water temperatures usually increase and dissolved oxygen
content decreases, which can increase fish diseases and reduce spawning
efficiency. Fine sediment can also clog fish gills, suffocate eggs and
aquatic larvae on the bottom of the stream, fill in the spaces between
bottom cobbles where fish lay eggs.
From the elk browsing in the meadows to the trout
swimming in the streams, western wildlife has evolved and adapted to
living with fire.
|
Cultural
Methods to Stimulate Conifer Seed Production
Randy Brooks
Private forest owners rarely have access to genetically
superior tree seedlings. Tree seed for reforestation of private lands is
frequently collected with inadequate attention to seed tree quality,
particularly if the focus is in getting cones.
Once a forest owner has identified superior trees based
on phenotype (observable characteristics) these trees can be cultured in
several different ways to help stimulate seed cone production. Cultural
methods are typically practices that will improve tree growth or
stimulate flowering and subsequent growth of flowers and fruits/cones.
Cultural methods can be very effective for promoting seed cone
production, but there are many external and internal factors that can
affect results. Some external factors include climate and pests.
Internal factors can include seed cone cycles (one good crop every few
years) and genetics (how a tree will respond to cultural practices).
Forest owners can use plant growth regulators,
fertilizers, root raking, pruning and/or thinning, irrigation and/or
moisture stress, girdling, or some combination of the above methods to
improve conifer seed production.
Plant growth regulators are hormone-like substances that
have a chemical-like control over plant growth processes. Gibberellins
are naturally occurring hormones that affect cell enlargement and cell
division. Gibberellic acid (GA 4/7) has been used successfully to
promote flowering and seed production in conifers (specifically larch).
Gibberellic acid is mixed in a 95% solution of ethanol (ethyl alcohol)
and then injected into the tree when lateral shoot elongation reaches
about 70%, but before bud differentiation begins. Trees less than 12
inches DBH receive a 50 cc injection, while trees greater than 12 inches
DBH receive a 100 cc injection of the mixture. A hole can be drilled
about ¼ inch into the tree and the mixture poured into the hole, or the
mixture can be applied with a hypo-hatchet.
Mineral requirements of reproductive tissues are high.
Limited nutrients can effect conifer seed cone production. Nitrogen (N)
and phosphorous (P) promotes flowering in conifers. Specifically, N
produces vegetative growth while P produces flower buds, fruit, and root
development. Potassium (K) helps build strong healthy plants. Fertilizer
application timing is critical. It must be applied before initiation of
floral buds if immediate increased flowering is to result. For pines
that require 2 years for cones to mature, spring application influences
flowering in the subsequent year, and cones in the 2 nd
year. Application rates vary, but the average is about 100 pounds actual
N per acre (typically ammonium nitrate), and about 250 pounds P (as P2O5)
and 100 pounds per acre K (as K2O).
Fertilization can keep trees healthy while maximizing
growth and vigor. However, it is recommended that a soil test be taken
first to assess nutrient levels and perhaps take foliar samples as well
to assess tree nutritional status. If adequate nutrient levels exist,
the money spent on fertilizers may be wasted. Fertilizer applications in
north Idaho can be difficult, depending on terrain and accessibility. If
you are only interested in seed production, consider choosing a few
phenotypically superior trees and fertilize those trees. Fertilization
can have other benefits such as increased tree health, growth, and
vigor. When used with a combination of crown release or irrigation, the
results are often better than when fertilizers are used alone.
Traumatic stress often induces heavier flowering and
cone production. Increased flowering of woody plants has been stimulated
by root raking (or root pruning). This is accomplished by dragging sharp
tines through the soil and cutting/severing the roots. This process can
be accomplished on one or two sides of the tree, not necessarily all the
way around a tree. The drawbacks are that heavy equipment is needed, and
terrain may be limiting. Root raking can also kill smaller trees if
damage is severe enough. Another drawback is that soil disturbance can
lead to other problems such as soil erosion. The Idaho Forest Practices
Act says that sediment must be kept out of streams.
Vigorous, dominant trees produce more seed than
intermediate or suppressed trees, and when competition is severe,
suppressed trees fail to produce any seed. Residual trees left after
thinning generally show increased flower and seed crops. Reasons for the
increase are thought to be from more exposure to sunlight and less
competition for resources such as moisture and nutrients.
Suppressed basal branches with only a few leaves/needles
often consume more carbohydrates in respiration than they produce in
photosynthesis for stem or fruit growth. Research has shown that within
a tree crown the vigor of individual branches also influences fruit and
cone development. Larger cones containing more seed tend to be produced
on branches in the upper one-third of a tree.
When used in conjunction with each other, thinning and
pruning select trees should be a cultural practice that is practical for
any landowner looking to produce more seed.
Girdling involves removing, excising, or cutting a
small, thin strip of bark containing the cambium and phloem from the
around the stem, branch, limb, or scaffold of a tree. Doing so often
stimulates reproductive growth because it impedes the translocation of
carbohydrates and growth regulators in the phloem. Phloem transports
materials down, while the xylem transports materials upwards. When
downward transport of carbohydrates is blocked, they tend to diffuse
back into the xylem and are translocated back up to, and concentrate in
the leaves and tissues involved in reproduction. Girdling trees in years
when cone production is high does not increase overall numbers of cones.
Girdling can increase cone production on individually treated branches.
However, one must gain access to the upper third of the tree and this is
often times difficult to do.
Girdling can be accomplished with a variety of tools,
ranging from chainsaws, pruning saws, handsaws, or knives. Larger saws
make it more difficult to control the cut, and care must be exercised in
order to avoid cutting into the xylem, which would disrupt the flow of
water upward, thus killing the tree. Special girdling knives are
available that allow cutting between the bark and the xylem. Smaller
wounds heal much faster than larger wounds.
Girdle the tree at breast height as the needles emerge.
Only girdle about 60% around the tree, and on the opposite side as high
as the diameter is wide. In other words, you will have two girdles on
each side of the tree, one higher than the other, and barely
overlapping. Do not girdle around the entire bole or the tree will be
killed.
There are a number of effects of different cultural
practices to stimulate conifer reproductive growth. Some measures are
more destructive than others, and may be better served on trees that are
intended for harvest. A combination of practices may work better than an
individual practice. Economics (cost/benefit ratio) must be examined, as
well as damage to the tree.
Applied Forest Tree Improvement, Zobel, Bruce and John
Talbert. 1984. John Wiley and Sons, Inc., Publishers. 505 pages. ISBN
0-471-09682-2
|
|
