3.seed plants have wood producing tissue well developed for water conduction and support. this...
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3. Seed plants have wood producing tissue well developed for water conduction and support. This enables plants to grow tall and out-compete neighbors
Vegetative
Conifer adaptations for drier environments
Conducting tissue
Water from roots
Xylem tissue
Trachieds
Parenchyma
Sugars from leaves
Phloem tissue
The secondary phloem in Pinus has sieve and albuminous cells and parenchyma with dark contents.
Conducting tissue is composed of xylem and phloem tissues
In conifers it consists of:
tracheids that conduct water upwards, are long in the vertical direction, and have bordered pits
parenchyma, thin walled cells
ray cells running horizontally through the xylem and are composed mainly of parenchyma and some tracheids
Secondary xylem is a complex tissue
Cross secction of a young pine stem
Cambium and secondary xylem of a coniferCambium and secondary xylem of a conifer
Cambium
Ray initials
Late wood
Early wood
Rays
Tracheids with bordered pits
Parenchyma
Esau 1965
Cambium and secondary xylem of a conifer
Direction of growth
http://www.uri.edu/artsci/bio/plant_anatomy/43.html
Tangential longitudinal section
Pits
Tracheids and rays, pine
Craig Aumann
Cavitation and
recovery from cavitationin Douglas-fir wood
Radial longitudinal section
Tracheids with bordered pits, pine
Bordered pits
as seen in face view (left) and in side view (right).
http://www.uri.edu/artsci/bio/plant_anatomy/images.html
The torus at the center of the bordered pit moves and seals the pit when a tracheid aspirates
Circular bordered pits of pine tracheids
Transverse section
Ray
Epithelial cell
Tracheid
Xylary resin duct in Pinus
Terminate cartoon
1. Plants accumulate matter and make growth
2. Plant growth is an organized process following rules of anatomy and morphology
3. Plants actively maintain their heat and water balance
4. Plants have a life cycle with reproduction and dispersal
5. Evolution is a constant process
How can we characterize conifers?Enduring, specialists at slow sustained growth sometimes with fast young stages
Many anatomical and morphological adaptations, including shade tolearnce
Stomatal control, and possibly avoidance of high radiation loads by foliage. Endurance is still the prime characteristic
Not dependent upon a water film – but the characteristic is wind pollination (wasteful?). Seeds
There are many specialists and there are local races (known as provenances in forestry)
How the ecology of conifers determines an environmental issue
Forest fires in natural ecosystems
Yellowstone National Park 1988
Many conifer species are adapted to withstand fire and/or regenerate following fire
Forest fire can occur naturally
Examples?
Conifer species in the western USA form largely ‘dry’ land forests
Forest Fires in the United States
Note the frequency and distribution of lightning caused fires
An estimated 16 million thunderstorms occur each year on earth, causing some 100 lightning strokes to the ground per second.
Between 50 and 80 percent of forest fires in western North America are lightning caused. There are some 4,871 lightning fires per year on federally-owned land in the US.
Lightning never strikes twice?
http://www.chaseday.com/lightning.htm
Why are forest fires a problem?
Fire suppression has resulted in the accumulation of high fuel loads
Satellite photograph of the Biscuit Fir, S.W. Oregon August 14, 2002
The Biscuit Fire started as a result of a series of lightning strikes on July 13, 2002 on the Siskiyou National Forest
It cost an estimated $135m to suppress at the date of containment. The fire grew to 499,570 acres over two months
On July 11, 2002, a Red Flag Warning was issued for dry lightning across southwestern Oregon beginning July 12.
There were a number of lightening strikes from the same lightening cell and a number of fires were started on hill tops with no road access. Some fire staff had already been sent to New Mexico and Colorado fires.
There was difficult, i.e., not safe access, and initially the fire had low regional priority.
Forest fires frequently start when lightening strikes on hill tops and may produce multiple small fires. There are at least 4 in this picture This type of location can be difficult for firefighters to reach
Icicle fire,Washington State,2001
Fire in ponderosa pine forest
Prior to 1900 low elevation ponderosa pine forests burned every 5 to 30 years Most fires burned only the forest floor reducing fuel and killing small trees
This produced open stands of large trees with grassy understories, some shrubs and occasional thickets of young trees.
After fire in Ponderosa pine
The “natural” size of a fire is very small (less than an acre) when the forest has a variable structure
Effects of fire exclusion in Ponderosa pine
Fire exclusion has produced a dense understory of young Douglas fir
Deep woody debris and duff give hotter longer lasting fires and poor germination
Since the advent of fire fighting some forests have missed 8 to 10 fire rotations
These photos were taken at Lick Creek in the Bitterroot Valley of Montana over an eighty-year period. Notice how the old growth ponderosa pine stand is replaced by dense Douglas-fir after fire suppression begins in the 1920s.
The consequences of fire protection in Ponderosa pine
Exit PowerPoint
Controlled burning
Ground fire
What conditions of fuel load, moisture content, temperature and wind produce a fire that burns the excess undergrowth and small trees without burning the dominant trees?
East side of the Cascades set in late fall
The effect of a controlled burn
Before
AfterThe effect of a controlled burn
Has sufficient material been removed to prevent a major conflagration?
in a Pinus ponderosa forest
Crater Lake, lower elevation forest burnt in early spring
Is there such a thing as a “natural” forest?
wherever there has been an effective fire suppression policy is it reasonable to conclude that forests there are not natural?
If we define “natural” as not influenced by humans
then
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