Transcript Document
Module 2 Forest Ecosystem structure and function O.T. Helgerson WSUCE 10/02 FOREST ECOLOGY Just how does it pertain to forest stewardship planning… Forest ecology effects: All Resource Categories • Forest health • T&E species, cultural resources • Timber and wood products • Esthetics & recreation • Soils • Agro-forestry & • Water spl. forest prod. • Fish & wildlife 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…. Diesel + O2 in Exhaust out Animate object in cab Trees in External interactions & interdependencies Internal interacting & interdependent systems Logs out Ecosystems vary in scale…. Depends on what we’re interested in…. Harvest setting or stand cull log 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: • Function – How is it put together? – What does it do Different structures… Different functions…. Ecosystem structure (sizes and arrangement of plants, animals, dead stuff et al.) Op. Env. Ecosystem function (the operational environment, exchange of matter and energy) 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) Physiographic and geologic provinces of Washington (Franklin and Dyrness 1973) BLUE MOUNTAINS 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 II F Pre-settlement fire intensity and frequency Adapted from USDA Forest Service, Dr. James Agee UW COF 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. Photo courtesy Bureau of Land Management Due to air quality regulations and loss of trained agency personnel, prescribed fire, as shown here, is used less frequently. Forest succession community 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 Where is your forest headed? Mostly shade intolerant plant species Figure from Washington State University Cooperative Extension Conversion to shade tolerant tree 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? PHOTOSYNTHESIS 100 PHOTOSYNTH % ESIS 2.46% 2% Foliage Boles & branches Below ground LOW SITE HIGH SITE Photosynthate allocation and site quality (Perry 1994) HEAT 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 Trophic levels T1 Producers T2 Herbivores T3 Primary Carnivores T4 Secondary Carnivores T5 Decomposers 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 the T1 level The environmental drivers determining species location also determine productivity. Soils management is very important. 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 Photo: Natural Resources Canada, Canadian Forest Service, http://www.pfc.cfs.nrcan.gc.ca/entomology/defoliators/budworms/west_spruce_e.html 20041119 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 mycorrhizal hyphae Photo: Dr. R. Molina, Oregon State University What happens within and around a primary root…? Fungi infect this blue layer of cells Water, dissolved nutrients and hormones carried up to needles in xylem cells (wood) Photo: Dr. R. Molina, Oregon State University Fungal hyphae connect root with water and nutrients on soil particles Root hairs also help 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