O.T. Helgerson WSUCE 10/02

Module 2

Forest Ecosystem structure and function

FOREST ECOLOGYJust how does it pertain to forest stewardship planning…

Forest ecology effects:All Resource Categories

• Forest health

• Timber and wood products

• Soils

• Water

• Fish & wildlife

• T&E species, cultural resources

• Esthetics & recreation

• Agro-forestry & spl. forest prod.

Ecosystems consist of…• Communities of animate (living) things:

plants, animals, microbes, et al.

• Inanimate stuff (rocks, soils, gasses, chemicals)

• Exchange matter and energy – Within the system– Between systems

• Systems interact and are interdependent

Another example ecosystem….Exhaust

out

Animate object in cab

Trees in

Logs out

Diesel+ O2 in

External interactions & interdependencies

Internal interacting & interdependent systems

Ecosystems vary in scale…. Depends on what we’re interested in….

Harvest setting or stand

culllog

Douglas-fir needle

Ecosystems on a landscape scale…

watersheds, timbersheds, spotted owl sma’s

Photo: Oregon State University College of Forestry

Until interplanetary travel becomes cost effective…..

Photo: Oregon State University College of Forestry

Ecosystems have: Structure & Function

• Structure: – How is it put together?

• Function– What does it do

Different structures…

Different functions….

Ecosystem structure

(sizes and arrangement of plants, animals, dead stuff

et al.)

Ecosystem function

(the operational environment, exchange of matter and energy)

Op.

Env.

operational environment: the physical environment around a living

organism; governs how ecosystems interact and function

light

heat

mechanical

chemical

Operational environment affects everything

• Growth

• Disease

• Insects

• Reforestation

• Distribution of plant and animal species

Operational environment

• BIG drivers– climate– elevation, slope, aspect– geology & soils– land conversion– fire policy– floods– biota

• Not so big drivers– timber harvest– silviculture– land conversion– microclimate– landslides– floods– plants & animals

which leads to…

why are plant species found where they are found?

Answer: its evolved adaptation to its surrounding operational environment

SO, HOW DO I KNOW WHAT MY TREES ARE?

and….

Ecological communities• Plants and animals occurring together in a

coherent group because of their adaptations to each other and the surrounding environment

• (Communities become ecosystems when we include processes behind interaction and interdependency)

BLUE MOUNTAINS

Physiographic and geologic provinces of Washington (Franklin and Dyrness 1973)

COAST RANGE

BLUE MOUNTAINS

Temperature and water availability are the two big drivers in determining forest type

Fire is important…

Geology, e.g. serpentine soils, may be locally important

Figure: USDA forest Service

How does your forest type affect your forest management

goals?

• ______________________________

• ______________________________

• ______________________________

• ______________________________

Let’s take a closer look at some natural forces…..

Natural forces (disturbances) modifying the operational

environment…• wind throw

• root disease

• global climate change

• volcanoes

• landslides

• floods

• and…

Fire, natural and human caused, is a major force driving plant succession in North American forests…

Some trees and shrubs are adapted to fire, while others are not

Photo courtesy Bureau of Land Management

Adapted from USDA Forest Service, Dr. James Agee UW COF

Pre-settlement fire intensity and frequency

FII

Photo courtesy Bureau of Land Management

Before fire suppression, east-side fires were typically low intensity and fairly frequent ground fires, leading to open stands of ponderosa pine and larch over much of the landscape.

Photo courtesy Bureau of Land Management

West-side fires tended to be infrequent, catastrophic stand replacing fires….

Due to fire suppression and fuels buildups, atypical catastrophic fires now occur on the east-side….

Timber harvesting is one way to reduce fuel loads in east-side stands to less damaging levels.

Due to air quality regulations and loss of trained agency personnel, prescribed fire, as shown here, is used less frequently.

Forest successioncommunity changes because

plants change the operational environment

See: Forest Ecology in Washington handout

Forest succession

• Primary succession follows big disturbance

• Early seral plant species

• Best in full sunlight conditions

• Secondary succession after initial plant community

• Late seral species• Best tolerate shade and

other understory conditions

See: Forest Ecology in Washington handout

The intense shade under this salmon berry seems to prevent even shade tolerant species from getting established here without some kind of disturbance

Shade is less intense under red alder, favoring slow natural establishment of western red cedar and western hemlock over Douglas-fir

Forest succession

• the changed operational environment may help perpetuate the existing plant community, OR, set the stage for the next community….

Shasta red fir seedling

Succession in an even-aged Douglas-fir forest

Figure from Washington State University Cooperative Extension

Where is your forest headed?

Conversion to shade tolerant tree species

Mostly shade intolerant plant

species

Succession may have many end points

• 45-year-old Douglas-fir stand (Idaho)

• Root disease and bark beetles affected outcome

• Susan K Hagle, USDA Forest Service, Western Forester, 2002

How does succession affect your forest management goals?

• ______________________________

• ______________________________

• ______________________________

• ______________________________

What about human induced ecosystem changes?

Harvesting affects the operational environment. Here…greatly increased light, heat, water, chemical turnover;

soil compaction?, mycorrhizal effects?

forest succession is restarted…

Thinning effects: less increase in light, heat, water, nutrient turnover;

mechanical damage to leave trees?, soil compaction?

forest succession may be accelerated…

Productivity…what makes the whole works run?

LOW SITE HIGH SITE

Photosynthate allocation and site quality (Perry 1994)

%

100

Boles & branches

Below ground

Foliage

2.46%

Leaf Area Index

An acre of highly productive forest may have 12 or more acres

of leaves over it;

where’s there most available water and good temperatures, there’s greatest productivity

Energy flows are like log processing: there’s an attempt to maintain maximum value at every step, or ecologically, nature tends to fill all niches with communities

Trophic levelsT1 Producers

T2 HerbivoresT3 Primary Carnivores

T4 Secondary Carnivores

T5 Decomposers

the T1 levelThe environmental drivers determining species location also determine productivity. Soils management is very important.

Photo: Natural Resources Canada, Canadian Forest Service, http://www.pfc.cfs.nrcan.gc.ca/entomology/defoliators/budworms/west_spruce_e.html 20041119

Nice little T2 Herbivores at work…

The western spruce budworm is a serious pest on east-side forests overstocked with true firs and Douglas-fir

Decomposers (T5) are essential within a forest ecosystem for nutrient cycling…

Decomposers include larger insects, and a fantastic variety of microscopic insects, bacteria, fungi and actinomycetes

Photo: Dr. A. Moldenke, Oregon State University

Photo: Dr. A. Moldenke, Oregon State University

Mycorrhizae: Symbiotic fungi that infect tree roots

• Mutual benefits– Greatly expanded root

network (increased water, nutrients)

– Essential hormones– Pathogen protection– Attracts microscopic

insects for bug poop near roots

– Fungi get food from tree

White stuff is

mycorrhizalhyphae

Photo: Dr. R. Molina, Oregon State University

Fungi infect this blue

layer of cells

Fungal hyphae connect root

with water and nutrients on soil particles

Water, dissolved nutrients and

hormones carried up to needles in

xylem cells (wood)

What happens within and around a primary root…?

Root hairs also help

Photo: Dr. R. Molina, Oregon State University

Which critters at which trophic levels affect your forest

management goals?• ______________________________

• ______________________________

• ______________________________

• ______________________________

Ecosystem resilience & sustainability

Our Pacific Northwest forest ecosystems are adapted to various types of natural disturbances. Photo: Washington DNR

Understanding Resiliency: disturbance does not exceed system

ability to recover :self healing

• redundancy

• genetic diversity within & between species

• refugia

Sustainability

• Sustainability is meeting present needs without compromising the future.

• Not pushing an ecosystem beyond its ability to recover

Practices that drastically alter the operational environment, such as terracing for site preparation, can be successful, though not politically acceptable

Legacies (the local spare parts bin)

As long as enough undisturbed ecosystem pieces remain, the system will recover

Photo: Oregon State University College of Forestry

Sustainability is like good equipment operation & maintenance…. Even better, with good harvesting practices, forest ecosystems can quickly repair themselves.

The right machinery and a knowledgeable operator are very important…

…as is leaving enough of the right pieces intact.

Trees and forests are a renewable and sustainable resource

These logs are the first commercial thinning of a stand planted by the logger when he was in high school on a brushfield cleared by his father.

Within stands or across landscapes, sustainability takes human ingenuity working with Mother Nature