O.T. Helgerson WSUCE 10/0 2 Module 2 Forest Ecosystem structure and function
Dec 18, 2015
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