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