Colored Leaves and Needles Means Fall in
Idaho
Yvonne C. Barkley
Come autumn, deciduous trees and shrubs turn color and
lose their leaves. Everyone expects this to happen in the fall. A tree’s
roots, branches, and twigs can endure freezing temperatures, but most
leaves cannot. Thin, tender leaves are made up of cells filled with
water sap, which freeze in winter. As the water in the cells expands as
it freezes, the cells burst and irreparable damage is done. Because of
this, any plant tissue unable to live through the winter must be sealed
off and shed to ensure the tree’s survival. As sunlight decreases in
autumn, the veins that carry sap into and out of a leaf gradually close.
A layer of cells, called the separation layer, forms at the base
of the leaf stem. When this layer is complete, the leaf is separated
from the tissue that connected it to the branch and it falls. Oak leaves
are the exception. The separation layer never fully detaches the dead
oak leaves, and they remain on the tree through winter and only fall in
the spring when they are "pushed off" by newly emerging leaves in the
spring.
Coniferous (often called evergreen) trees also lose
their leaves, they just do it a bit differently. Conifer leaves are
needles that are covered with a heavy wax coating and the fluids inside
the cells contain substances that resist freezing. Needles can live for
several years before they fall and are replaced by new growth. Natural
foliar shedding varies with the species of evergreen. Pines lose their
third year needles, those closest to the trunk. The needles turn brown
to red-brown (the dryer the year, the brighter the color) and are cast,
sometimes all in one day if there is a good wind. Arborvitae and related
species with scalelike leaves shed their oldest branchlets (those in the
interior). Spruce and fir bear several age classes of needles along
their branches and shedding is not restricted to the oldest age class,
although it is concentrated there. The foliage on a given branch segment
of these species may brown and thin progressively over 2 to 3 years.
And those deciduous trees and shrubs? Why do they change
color anyway? Leaf color comes from pigments, which are natural
substances produced by leaf cells. The three pigments that color leaves
are chlorophyll (green), carotenoid (yellow, orange, and brown), and
anthocyanins (red). Chlorophyll is the most important of the three.
Without the chlorophyll in leaves, trees wouldn’t be able to use
sunlight to produce food (photosynthesis). Carotenoids create bright
yellows and oranges in familiar fruits and vegetables, while
anthocyanins add the color red to plants. Chlorophyll and carotenoid are
in leaf cells all the time during the growing season. The green of the
pigment chlorophyll covers the yellows and oranges of the pigment
carotenoid during the summer, giving us green leaves. Not all trees can
make anthocyanins, and most anthocyanins are produced only under certain
conditions.
As the days get shorter and the temperatures start to
drop, trees respond by producing less chlorophyll. As chlorophyll levels
drop, the carotenoid already in the leaves can finally show through and
leaves become a bright rainbow of glowing yellows, sparkling oranges,
and warm browns. While the yellow, gold, and orange colors created by
carotenoid remain fairly constant from year to year, anthocyanins (which
give leaves the bright, brilliant shades of red, purple and crimson)
will vary. In some years, the red fall colors seem brighter and more
spectacular than in other years. Both temperature and cloud cover can
make a big difference in a tree’s red colors from year to year. A series
of warm, sunny autumn days and cool but not freezing nights provides the
perfect conditions for a fall with a lot of reds. This is because during
warm, sunny days leaves can produce lots of sugar, but cool nights
prevent the sugar sap from flowing through the leaf veins and down into
the branches and trunk, where it is used by the plant. Researchers have
found that anthocyanins are produced as a form of protection and allow
the plant to recover the "lost" nutrients from the leaves before they
fall off. This insures that the tree will have adequate nutrients for
the next growing season.
The amount of rain in a year also affects autumn leaf
color. A severe drought can delay the arrival of fall colors by a few
weeks, and sometimes the leaves just turn brown and drop without much
color. A warm, wet period during fall will lower the intensity, or
brightness, of autumn colors. A severe frost will kill the leaves,
turning them brown and causing them to drop early. The best autumn
colors occur when there’s been a warm, wet spring, a summer that’s not
too hot or dry, and a fall with plenty of warm sunny days and cool
nights.
Warm days and crisp nights. Apples and hunting. The
smell of those colored leaves and pine needles as you crunch them under
your feet. That’s fall in Idaho!
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Top 10 worst reasons to not prepare your home for forest fires
Chris Schnepf
When teaching landscaping for fire prevention workshops
and interacting with people who have read articles we have written on
the topic, I have heard a lot of excuses for not preparing homes for
fire. This topic has also been studied in surveys1 .
So with apologies to David Letterman, here are 10 of the more common
reasons for not doing defensible space, and some responses . . .
10. I’ve never seen a forest fire here in all my life.
Even prior to European settlement, moist forests in
northern Idaho could go 50 years between ground fires, so it is very
probable someone would not see a fire in their neighborhood for most of
their life, particularly with modern fire suppression efforts. However,
fire exclusion and selective cutting practices have changed the
structure and species composition of Idaho forests significantly,
resulting in a backlog of fuels. In many areas of Idaho, conditions are
riper than ever for a forest fire.
9. The problem is on my neighbor’s property.
Obviously you can’t control your neighbor’s landscape.
But high fire hazard on your neighbor’s property is all the more reason
to make extra efforts to reduce risks you can control on your property.
Recent research indicates features closest to the house (the home
ignition zone) are the most important factors in whether a home
burns down in a fire. So redouble efforts to reduce combustibles next to
your house (e.g., needles collected in the gutters, firewood stored near
the house). You can also share publications and other resources on this
topic with your neighbors – sometimes all it takes is additional
information from a third party to help people take action.
8. It’s not my job (I pay taxes to have my home
protected from forest fire).
Some folks believe preventing their home from burning
down in a fire is what they pay taxes for. And we do pay a lot of people
to keep fires from burning down homes – whether the fire starts inside
the house or in the woods. But fires do not always start and spread
predictably. In a really big fire, no amount of manpower will be enough
to protect all homes – especially homes that have not taken steps to
reduce the flammability of their home and surrounding landscape and made
their properties easily accessible to firefighters. You are more likely
to get assistance from firefighters to the extent they have a fighting
chance to survive defending your house.
7. I have no place to put the slash.
Disposing of trees, brush, and other organic materials
accumulated in a fire risk reduction effort can be daunting. The
standard method is to pile it and burn the piles. But that may not be
possible at all times of the year. You can sometimes haul it to a dump,
but that gets expensive, both for the landowner (if the dump charges
fees) or the taxpayer who is paying for that space in the landfill.
Another option is to have the material chipped and spread through the
surrounding forest. This approach has the added advantage of helping to
suppress the emergence of additional vegetation. Do not spread the
material right next to the house (fire will follow it to your house),
avoid piling it deeper than one inch (deeper accumulations interfere
with air and water movement in your soils), and do not mix it in with
soils (the microorganisms that decompose it will use up nitrogen in the
soil, making it less available for trees). Some recycling centers
provide a free drop for yard waste and chip it up to reduce landfill
volume or provide it to landscapers for mulch.
6. I don’t know what to do.
Extension offices have a wealth of publications,
workshops, videos, and assistance from master gardeners to help you to
prune, thin, control brush and otherwise reduce fire risk. Most
firefighting agencies also have information. Perhaps you’re not sure how
to apply that in your specific context. There are a growing number of
home landscaping services in Idaho who provide detailed on-site
assistance with this for a fee.
5. I don’t have the time or money.
Some of the activities to reduce home fire risk in a
forested setting can cost a lot of money (e.g., replacing a wood roof).
Other activities, (thinning, pruning, etc.) are less expensive but
require time and sweat equity. But think - how much is your home worth?
The old car mechanics adage applies ("you can pay me now or pay me -
more - later"). Thinning and pruning trees reduces fire risk and
improves your landscape’s health, and may increase real estate value.
Some Idaho communities now have grant funds available to help you hire
someone to help you with some of these tasks – check with your local
fire protection district about hazardous fuel treatment (HFT)
funds.
4. I want it to be natural.
People have different ideas, in different contexts, for
what is "natural". Historically, natural on many forested Idaho home
sites would have meant ground fires coming through every 10-30 years
killing small trees coming up in the understory (on medium to moist
forests there would have been crown fires too). By that standard, many
of our current forests are un-natural in both structure and species
composition. Unless you are prepared to allow fires to burn through (and
even then the results may not be natural, considering the historically
unprecedented volume and configuration of fuels that have accumulated in
the absence of fires), cutting excess small trees and shrubs in forest
understory is one way of mimicking the effects of natural fires.
3. How can I make any difference for something as huge
as a forest fire?
There are times when a fire is so powerful that all
efforts to keep a house from burning down fail. However, this is a bit
of a red herring. It is never a question of your home being at risk or
not. The question is how to reduce your home’s risk. The practices that
reduce ignition potential have saved a lot of homes. Unfortunately, you
don’t usually hear as much about homes that survived forest fires as
those which perish in them (seen any headlines to the effect of "dog
doesn’t bite man?").
2. I want my trees dense to screen my neighbors.
Many homeowners live in rural areas because they value
privacy. Frequently people want to leave trees dense to screen noise and
visuals (e.g., your neighbor’s "outdoor antique car collection"). Some
of this may be OK as long as the dense trees are at least 100 feet from
your house. But even there, overcrowded trees are ultimately doomed to
be killed by bark beetles, then present a greater fire risk. You are
going to lose a lot of the screening effects anyway, as the lower
branches of overcrowded trees die out from shade. Starting to thin them
earlier will keep the lower branches longer. Additional screening could
be provided by shrubs. If appropriate, earthen or other-non-organic
screens provide a safer alternative than leaving dense stands of
conifers.
1. It won’t look good.
The quick response to this is to ask how your landscape
and home will look after a forest fire comes through. But aside from
that, some folks fear that reducing their fire risk will result in their
landscape looking like a "bunker" or a "lunarscape". You can have a fire
resistive landscape that is still very green and naturalistic. In fact
one of the ways to keep your home more resistive to fires is to keep the
landscape well watered and green (e.g., the lawn). The primary focus on
reducing fire risk is to reduce the continuity of fuels (especially
closest to the house), not to remove vegetation from the landscape
entirely.
Conclusion
Fire risk reduction is not something you can or need to
complete perfectly at once. Indeed, you will never be completely done,
because it is important to maintain the risk reduction you have started.
But don’t let bad reasoning or uncertainty prevent you from taking the
steps necessary to protect your home and surrounding forest.
_________________________
1 Smith, E. and M Rebori. Factors
Affecting Property Owner Decisions about Defensible Space. 2001. In:
Forestry Extension: Assisting Forest Owner, Farmer and Stakeholder
Decision-Making. Proceedings, 5th IUFRO (International Union of Forestry
Research Organizations) Extension Working Party Symposium. D. Race and
R. Reid, editors. Australian National University & CRC for Sustainable
Production Forestry, Hobart Tasmania, Australia.
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Forest Soils versus Agricultural Soils
Randy Brooks
Soil or dirt? What’s the difference? My college
professor would get discombobulated when we called it dirt. So we posed
the same question to him – what’s the difference? He said that soil is
what plants grow in and dirt is what you get under your fingernails! Big
deal, we thought.
As a medium for plant growth, soil can best be described
as a complex natural material derived from disintegrated and decomposed
rocks and organic materials, which provides nutrients, moisture, and
anchorage for land plants. A soil can be considered a product of its
environment. Soils are formed from parent material (rocks, volcanic ash,
etc.), by the action of living organisms (plants, animals, and man),
climate, and topography over time. Soils consist of four basic
components: mineral materials, organic (living or once living) matter,
water, and air. These are combined in widely varying amounts in
different kinds of soil, and at different moisture levels, and can
change as the environment changes or is modified.
Forest soils differ from agricultural soils in many
respects. Agricultural soils were selected because of desirable chemical
and physical properties. Foresters may regard the physical properties of
soils as one of the more important factors. In agriculture soils
chemical properties may be most important. In most areas of America,
forest soils are those that were relatively undesirable for agriculture.
Historically, the better soils have been cultivated while the poorer
remained in native vegetation. Certain soil properties, such as rock
content, prevent or restrict agricultural activities. Forest soils tend
to be shallower with more rock than agricultural soils have. Since most
forest soils occur on sloped terrain (especially in the west), they tend
to be younger with more variability. Even so, some of these soil types
can be very productive from a foresters perspective.
 Fully
developed forest soils are natural bodies with vertical layers. At the
top is an organic surface layer or "forest floor" (O horizon) with
subdivisions of fresh, undecomposed plant debris (Oi horizon, formerly
called L); semi-decomposed, fragmented organic matter (Oe horizon,
formerly called F) and humus; and amorphous organic matter without
mineral material (Oa horizon, formerly called H). Below this surface
layer is a mineral surface horizon (A); a subsurface mineral horizon
often leached (E); a subsurface mineral horizon with features of
accumulation (B horizon); a mineral horizon penetrable by roots (C); and
locally hard bedrock (R). The E, B, C, and R horizon may be lacking, or
the B horizon may be modified by groundwater or stagnant water. Forest
soils usually are more shallow and rockier than agriculture soils. As a
result, they tend to be more variable in their physical and chemical
properties when compared to agricultural soils. The O horizon is usually
more important in forest soil, as it is a primary source of nutrients.
Agricultural soils associated with rangelands and
grasslands often have horizons similar to forested soils. However, if
they are being cultivated, or have been in the past, they usually lack
the organic (O horizon) layer. The A horizon usually has been mixed with
parts of the E and even the B horizon, resulting in an artificial plow
layer (Ap horizon). The B and/or C horizons may have been broken up by
deep cultivation or ripping. The soils may have been so degraded by past
human actions that they are no longer arable, as was the case in the
southern United States before the large-scale commercial production of
fertilizers. Such soils may still be classified as agricultural soils
and used, for example, for grazing or non-cropping production.
Agricultural soils are typically more uniform than their forested
counterpart due to cultivation.
Recall that soils are formed from parent material. The
nature of the parent material is of more importance in forest soils that
in agriculture soils. As discussed by Ron Mahoney in Good Rocks/Bad
Rocks, the Latest Piece of the Puzzle of Natural Forest Fertility
(Woodland Notes, Vol. 8, No. 2, Winter, 1997), natural forest fertility
can be traced to parent materials. More specifically, sedimentary rocks
appear to be lower in nutrient values compared to soils formed from
granites. In agriculture, fertilizers are added to amend any nutrient
deficiencies. Thus, differences between the two soils are enhanced by
the addition of agrichemicals and fertilizers.
Considering the natural landscape, you might wonder how
native prairies and forests function in the absence of tillage and
fertilizers. These soils are tilled by soil organisms, not machinery.
They are fertilized too, but the "fertilizers" are used again and again,
and never leave the site. Native soils are covered with a plant litter
(the "O" horizon) and/or growing plants throughout the year. Beneath the
surface litter layer, a rich complex of soil organisms decompose plant
residue and dead roots, then release their stored nutrients slowly over
time. In fact, topsoil is the most biologically diverse part of the
earth. Soil dwelling organisms release bound up minerals, converting
them into plant available forms that are then taken up by plants growing
on the site. The organisms recycle nutrients again and again from the
death and decay of each new generation of plants.
There are many different types of organisms that live in
the topsoil, each contributing in some form or fashion to soil fertility
and health. An acre of living topsoil typically contains approximately
900 pounds of earthworms, 2,400 pounds of fungi, 1,500 pounds of
bacteria, 133 pounds of protozoans, 890 pounds of arthropods and algae,
and even small animals, in some cases. Therefore, the soil can be viewed
as a living community rather than an inert body. These numbers,
especially for earthworms, can be reduced by farm tillage practices.
In conclusion, forest soils differ from agricultural
soils in many respects. Vegetation, rock content, well defined profiles,
chemical and physical properties, nature of parent materials, and
location/topography are just some of the factors that separates these
two types of soils. In either case, the soil can be managed to remain
sustainable, but that is another topic for another issue!
For more information on soil and soil organisms, browse
the following websites:
http://www.soilfoodweb.com/sfi_html/index.html
http://www.attra.org/attra-pub/soilmgmt.html
http://www.id.blm.gov/publications/crust/index.htm
http://www.liverpool.k12.ny.us/standards/lstandards/curriculum/sci/g3sci/soillayers.html
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Moisture Stress: What Does That Mean for Trees?
Yvonne C. Barkley
With below average precipitation over several seasons,
trees across Idaho, whether they are in your yard or out in the woods,
are moisture stressed. Trees vary in their ability to tolerate moisture
stress, with native trees having much more tolerance than planted trees
and shrubs. Moisture stressed trees are much more susceptible to
diseases, insect attacks, and injury by severe weather. Basically,
moisture stress occurs when the amount of water going out of a tree is
greater than the amount going in. All plants transpire, loosing water
through the foliage to help cool the plant and also help move water from
the roots to the leaves. When there is a shortage of water within the
plant, foliage wilts. As moisture stress continues, symptoms such as
browning of leaf margins and tips of leaves and needles occurs.
Deciduous trees and shrubs will drop some or all of their leaves. If a
severe shortage occurs over a period of several tears, branch and crown
dieback, and eventually death of the entire plant will occur.
Moisture stress continues to happen over the winter,
most notably in evergreen trees and shrubs, when water evaporates from
leaves and stems when the soil is cold or frozen. Roots extract little
moisture from cold soils and none from frozen soils and cannot replace
moisture lost. Trees and shrubs subjected to winter moisture stress will
show browned needles and may even die over the winter. This is commonly
referred to as winter death.
Moisture stress related to dry soil can be alleviated by
proper watering practices. Moisture stress is the primary cause of death
for newly planted trees and shrubs, which need supplemental water every
7-10 days if there is not adequate rainfall. For all practical purposes,
watering established trees and shrubs in times of drought will usually
be restricted to those plants that are within distance of your longest
hose.
It is very important that trees and shrubs receive
enough water before the soil freezes. Most of a tree’s roots are located
in the top two feet of soil. When watering, you want to soak the soil to
a depth of at least 12 inches. Short, frequent watering usually does not
penetrate much beyond the sod and organic matter layer of the soil
profile.
There are several methods of deep watering your trees.
The easiest way is to spiral a soaker hose around your trees and shrubs
let the hose run slowly for at least four hours. Move the hose around
the entire drip line of larger trees to ensure that all of the roots
receive water.
Mulch is another way to conserve moisture around your
trees and shrubs. Mulch is any material placed on the soil to cover and
protect it. Common mulches are bark, wood chips, ornamental gravel, and
landscape matting. Mulching will also help with weed and grass control
and protect the lower portions of your trees and shrubs from mechanical
injuries.
You can lessen the effects of drought on your forest
trees by thinning both the trees and shrubs so you have less plant
material per acre, leaving more moisture, light, and nutrients for those
that you leave.
When all else fails, and you lose a tree or shrub to
drought stress, take the time to replace the planting with a more
suitably drought tolerant species. If you lost a birch to drought
stress, do not replace it with another birch! Drought tolerant species
include bur oak, Gamble oak, blue oak, black and honey locust, Rocky
Mountain juniper, Austrian pine, and ponderosa pine. Drought intolerant
species include birches, cottonwoods, poplars, spruces, and firs.
Remember the old adage "an ounce of prevention is worth
a pound of cure"? In the case of deep watering your trees and shrubs
before winter it proves only too true.
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