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Woodland NOTES - Vol. 14, No. 2 ~ Spring/Summer, 2003
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A. H. Winward, Range Ecologist (Retired), USDA Forest Service and Ron Mahoney, Extension Forester, University of Idaho I’ve (Ron) spent most of my 36 years as a forester studying and applying silviculture in primarily upland situations. Although some of my earliest experiences involved cruising the great swamps of Florida’s Appalachicola River and Georgia’s Okeefenokee, I really never paid much attention to riparian forests in Idaho during my 30 years here until the last five years when I began to teach in our LEAP (logger education) classes which include field exercises on stream protection zones. Like the uplands I am more familiar with, it became obvious to me that succession (the change in vegetation over time) in riparian settings also accelerates when these zones are protected from disturbance. It seemed to me that many riparian plant communities today might be as unprecedented as our vast, late-succession upland forests that challenge restoration advocates. I began to formulate questions about changes in soil and water chemistry, impacts on riparian fish and wildlife, erosion and other threats to water quality and formed a generalized notion that these changes need to be recognized, studied, and considered to effectively manage riparian ecosystems. When I bounced my ideas off the fish and wildlife professionals that I occasionally encountered, it didn’t seem to be an issue with them. The Forest Practices Act that governs timber harvest in Idaho, like similar laws in other states, is primarily geared towards reducing sedimentation and providing shade, and does not address species composition or tree density beyond a minimum. By this time, I thought I had formulated a revolutionary, albeit obvious, concept and that the sooner it was revealed the better. Everyone, it seemed, was focused on streams as the most critical habitat issue in the Pacific Northwest, and perhaps everywhere else. About a year ago, a recently retired Range Ecologist, Dr. Alva H. Winward (Ph.D. UI, 1970), was to visit our University, and I took advantage of his offer to meet with interested faculty. Here, I thought, was a chance to test my riparian concepts with someone that would have some background in the subject, since most range conservationists regularly deal with riparian impacts. Dr. Winward was gentle as he vigorously supported my concepts while revealing that they were hardly novel. In fact, he discussed and later provided me a paper he wrote in 1976 (of the same title as this article) and later presented and published in 1989 at a regional silviculture workshop while he was Regional Ecologist for the Intermountain Region of the Forest Service. What follows are his wise words, with a few parenthetical comments I provided for the Northern Rockies outside the drier forest types typical of the Intermountain Region. His message is timely, important, and to many is revolutionary. It is as true and applicable today as it was in 1976. In the USDA Forest Service Intermountain Region, approximately 20 to 30 percent of the riparian areas currently have a dominant tree canopy. Probably over 80 percent of our riparian areas potentially could support a dominant tree overstory if successional processes were allowed to proceed without some type of interference. Common riparian tree species in this region include: cottonwoods, aspen, maple, box elder, birch, alder, subalpine, grand and white fir, Engelmann and blue spruce, and in some settings lodgepole pine (and western redcedar, white pine, western and mountain hemlock in the north). Historical records and photographs indicate that fire played an important role in riparian species composition just as it did on our upland settings. The nature of historical wildfires logically suggests that burns did not necessarily stop at the upland/riparian interfaces. Instead, they often burned through these wetter areas too, removing or reducing the woody species. Most likely, many of the original tree species in riparian settings were comprised of deciduous, resprouting species such as cottonwoods, aspen, alder, birch and others. Later successional, nonsprouting species such as the firs, spruce, (cedar, hemlock) and certain pines were likely spotty, temporary dominants in riparian settings. Such is not necessarily the case now. Our successful efforts at controlling wildfires has not only allowed a proliferation of woody species on much of our uplands but has likewise allowed a gradual yet continual build up of coniferous trees in our riparian settings. For those who might emphasize wood production, this move toward conifers may seem positive. But, from an ecological standpoint, might these changes be disruptive? Many of our riparian systems that have live, moving surface water present, i.e., those associated with creeks or rivers, often require the presence of special hydric (water adapted) understory species in order to adequately withstand the erosive forces of moving water. As succession advances toward a conifer overstory, these understory hydric species are gradually shaded and crowded out of the composition. Unless there is a high percentage of boulders and cobbles in the stream bed and on the stream banks, the conifer roots alone, without additional backup from the roots of understory hydric species, will not provide the stability necessary to allow a balance between bank building and bank breakdown processes. In these kinds of settings, we can benefit from silvicultural practices that prevent such conifer dominance. (Evidence from soil/water chemistry studies suggests dramatic changes in pH (acidity), nutrient composition and cycling with these vegetation changes, which would greatly affect riparian organisms.) There is ample evidence of settings where dense conifer canopies exist with essentially no shrub or herbaceous understories present. In these settings, stability of banks has been critically reduced Mechanical forces of water eventually cut around root-clumps of the trees resulting in a deposition of the tree, root-clump, and soil into the stream system. While some of this is likely natural, accelerated (bank) cutting alters the stream channel too rapidly and adds abnormal amounts of sediments and woody debris into the stream. Under presettlement conditions it appears that the presence of small patches or scattered individual trees in our riparian ecosystems was likely a normal situation. Under the more open, scattered canopies other tree, shrub, and herbaceous species provided the required stability to the system while, at the same time, allowed some "normal" amounts of woody debris to become a natural part of riparian ecosystems. In addition to a higher degree of riparian stability with the mid-successional species, the deciduous overstory species, along with the properly adapted understory species, provides an ecological setting unmatched for diversity of plant and animal species. This is the natural setting and habitat for many of our native bird and mammal species. Scenery offered by this diversity is often favored by many of our recreating public as well. Many advocate no timber harvesting in riparian settings. Generally, this restriction is related to the extreme damage that can take place in the wet settings during the logging operation and to the potential detrimental effects on stream habitat and water quality. However, in the interest of ecological stability in riparian settings it gradually is becoming necessary to initiate some type of management process that will restrict dominance of later successional (conifers). Depending on the setting and on other special circumstances, the removal or thinning of these trees may be accomplished through either prescribed fire treatments or through appropriate timber harvesting practices. Any silvicultural practices will have to be done in a special and gentle way in which damage to the other vegetation and to the soil and water resources is minimized. Seldom will it involve a complete tree removal process. Instead, harvesting will have to be accomplished in a series of entries where all trees are not removed at once. Also, we will need to leave an appropriate amount of trees to live and die in the system; this apparently was nature’s way. Recent studies are providing information on the need for large woody debris in riparian systems. Now, we need to develop information that provides us a better feel for how much to leave in different riparian settings. (Much of this information has been gathered and incorporated into current riparian regulations, but without regard to composition, often emphasizing conifers and overlooking pre-fire reference conditions).
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Ron Mahoney Foresters of today, and in fact all natural resource managers, may feel the public questions their every move and motive. Some of those questions come from well informed individuals and organizations, and others from well-meaning folks that suspect a lot of information presented to them is not true. Current speakers on public relations tell us that the time of expert opinion finding a trusting audience is over. Perhaps they are recalling "good old days that never were". The following guide to "Foresters in Public Service" was written about 100 years ago by one of the first U.S. foresters and first Chief of the U.S. Forest Service, Gifford Pinchot, as part of his series "Lectures to guide the behavior of foresters in public office". Today, all natural resources managers are accountable to the public, including industry foresters and private consultants. I think these words will help us all maintain our credibility. The issues we confront are not new, but perhaps we can address them with less acrimony. Here is what Pinchot said: 1) A public official is there to serve the public and not to run them. 2) Public support of acts affecting public right is absolutely required. 3) It is more trouble to consult the public than to ignore them, but that is what you are hired for. 4) Find out in advance what the public will stand for; if it is right and they won’t stand for it, postpone action and educate them. 5) Use the press first, last, and all the time if you want to reach the public. 6) Get rid of the attitude of personal arrogance or pride of attainment of superior knowledge. 7) Don’t try any sly or foxy politics because a forester is not a politician. 8) Learn tact simply by being absolutely honest and sincere, and by learning to recognize the point of view of the other man and meet him with arguments he will understand. 9) Don’t be afraid to give credit to someone else even when it belongs to you: not to do so is the sure mark of a weak man, but to do so is the hardest lesson to learn; encourage others to do things; you may accomplish many things through others that you can’t get done on your single initiative. 10) Don’t be a knocker: use persuasion rather than force, when possible; plenty of knockers are to be had, your job is to promote unity. 11) Don’t make enemies unnecessarily and for trivial reasons; if you are any good you will make plenty of them on matters of straight honesty and public policy and will need all the support you can get.
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Steve Cook, Forest Entomologist, University of Idaho What are invasive species? A species is invasive when it is found beyond its natural range. In Idaho, an invasive species can be one that came from Europe or it can be one that came from Pennsylvania (as long as it is outside of its natural range). Why are invasive species important? Invasive species are a clear and present danger to our forest biodiversity. As a threat, invasive species rank second only to habitat loss as a threat to native biological diversity. Invasive species can devastate native tree species, alter ecosystems, and cause huge economic losses. For example, exotic insects may be more likely to outbreak then native forest insects and although exotic insects comprise approximately 2% of the total insect fauna of North America, they comprise approximately 40% of the forest insect pests of economic concern. How do invasive species arrive? Many forest insects arrive in wooden shipping containers. Of the approximately 14 million shipping containers from foreign sources that arrive in the United States annually, APHIS inspects approximately 2% of them and finds approximately 400 dangerous exotic insects on/in wood packing material annually. Other routes of entry include nursery/planting stock (i.e. citrus longhorned beetle) or transport on automobiles (i.e. gypsy moth). How do an invasive species become established? Most forest insects are controlled within their native ranges by: 1) the plant on which they feed, or 2) natural enemies that feed upon them. Successful invaders share several characteristics that release them from these normal controlling agents and help them to become established in the newly invaded area. These include: • finding hosts in the newly invaded area similar to hosts in its native range; • having these hosts not recognize the invasive species as a threat and not successfully defending themselves against the new species; • encountering little competition from native species and being able to ‘take over’ the newly found host; • arriving without its ‘normal’ component of natural enemies and having the potential natural enemies in the newly invaded area not recognizing it as a potential prey item; and/or • reproducing rapidly, even at low population densities (invasive species normally arrive in low numbers and then the population builds). Invasive species can alter ecosystems – An example from the eastern United States. American chestnut was one of the most important trees growing in the forests of the eastern United States. American chestnut originally occurred from Maine to Florida and from the east coast west to Ohio. American chestnuts dominated the region and were a keystone species on approximately nine million acres of eastern forests. The trees were among the largest in eastern North America, with mature chestnut trees averaging up to 5 feet in diameter and up to 100 feet tall. The trees grew straight and often self-pruned to 50 feet or more, making them a valuable timber species. In addition, along with humans, native wildlife from birds to bears depended upon the nut crop from these trees. Then, chestnut blight was introduced into New York City in 1904. The disease spread quickly through eastern forests, leaving only dead and dying chestnut trees in its wake. Within 50 years, American chestnut was virtually eliminated from its once dominant place in eastern forests, leaving a gap in these forest ecosystems that was filled by other tree species, including many oaks. Gypsy moth arrived in Massachusetts in the late 1860’s. When it escaped, it found itself in an area with plentiful food and no natural enemies capable of regulating its population growth. Gypsy moth caterpillars feed on over 100 species of plants, but their favorite host trees include oaks, poplars, and willows – some of the same species that replaced American chestnut. The moth has since spread southward as far as North Carolina and westward as far as Wisconsin. In areas where gypsy moth is well established, the insect is behaving much like a native insect, going through periodic outbreaks that are brought under control by natural enemies that include small mammals such as white footed mice, parasitic wasps, and naturally occurring diseases. Much of the effort to manage gypsy moth populations in the eastern United States is now aimed at slowing its range expansion into new areas. This tactic has been termed ‘slow-the-spread’ and has decreased the range expansion of the insect from 13 miles per year to about 4 miles per year. Outside of the generally infested area and beyond the ‘slow-the-spread’ boundaries, new infestations are actively controlled, usually with some type of insecticide application. Several gypsy moth introductions in Idaho have been similarly controlled. In some of the areas where gypsy moth has become established, the heavily defoliated oaks have become less abundant and another shift in forest tree composition is occurring. This shift in species composition may favor an increased presence of maples and poplars in some areas. Now, another invasive insect has arrived and may enter the forests in the eastern United States, the Asian longhorned beetle. Asian longhorned beetle has probably been in the United States for about 10 years. Currently, populations of the insect are located in both New York and Illinois. In its native range, Asian longhorned beetle is a serious pest of poplars. Attempts to grow plantations of North American maples in China have been abandoned because the trees are killed by these beetles. If this beetle escapes beyond its localized populations into the eastern hardwood forests, it, like its predecessors, has the potential to alter North American forest ecosystems. But what about invasive insect species in Idaho? We currently have two invasive forest insects of concern in Idaho – larch casebearer and balsam woolly adelgid. Larch casebearer is a tiny, silver-brown moth that was discovered feeding on western larch in northern Idaho in the late 1950’s and has since spread through much of the interior west. As caterpillars mature, they cut off a portion of a larch needle, hollow it out, line it with silk and then live, feed, and complete development within this ‘case’. The caterpillars feed on new foliage in the early spring and heavily infested trees become reddish in color. Repeated defoliations can weaken the trees and reduce tree growth. Two parasitic insect species have been introduced into the western states and effectively control populations of this moth. Balsam woolly adelgid is another tiny insect that was introduced into the western United States in the 1950’s. This European insect looks like a small patch of wool on the tree and is a pest of true firs in both eastern and western forests. In Idaho, subalpine fir appears to be most heavily impacted by this insect. The entire population of balsam woolly adelgid is female and infestations can be started by a single individual. In some low-lying areas such as frost pockets with subalpine firs, trees may be eliminated by this insect. Balsam woolly adelgid feeds on the stem, branches, and twigs of the attacked trees. Trees that have heavy infestations on the trunk can die within a few years. Gouting of the buds that progressively weakens the trees occurs on the trees that have branch/twig infestations. Balsam woolly adelgid can have up to four generations per year. At present, there is no effective natural control agent for this insect in Idaho. So, what’s to come? We do not know that any particular insect species will become established within our region or what economic and ecological consequences will be if a new invasive species does become established. However, we can be confident that we will continue to see new invasive species arrive and that some of these will have the potential to significantly alter our forests.
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Chris Schnepf, Area Extension Educator – Forestry, University of Idaho Tim Prather, Extension Specialist – Weed Ecology, University of Idaho Forest fire: not if, when. Forest fires are a natural part of Idaho’s ecology. Historically, many forested areas now occupied by homes had ground fires every 5-40 years and crown fires every 200-250 years. Forest fire suppression and other factors have made fires even more likely. The question isn’t if forest fires will occur but when! Rural Idaho residents should view wildfire the same way people in the Midwest view tornados -- a common natural phenomenon that can devastate property and life -- and prepare accordingly.
Many people have heeded the warning about fire in north Idaho landscapes and removed fuel ladders between their home and landscape and between trees in the surrounding landscape. However, maintaining a fire-resistant landscape is not a one time-effort . . . Nature abhors a vacuum. Creating more spaces between trees means more light will reach the forest floor. There will also be more moisture and nutrients available for plant growth. All of this means remaining understory plants and trees will grow larger and faster (especially younger trees), and new plants have a more favorable environment to germinate and grow.
To make matters worse, the tree species that tend to regenerate in these partially shaded environments tend to be shade tolerant species such as Douglas-fir and grand fir. Douglas-fir and grand fir are typically less resistant to insects, disease, drought, and fire than shade intolerant species such as pine or larch. To maintain a fire-resistive landscape, plants, and plant litter must be continually monitored and modified or removed as needed. Plant litter around structures. Research from the USFS Forest Sciences Lab in Missoula, indicates that fuels for a fire and other factors closest to the home have the greatest influence on whether a home burns down in a forest fire. Pay extra attention to flammable materials that contact the house. Keep the roof and gutters cleaned of needles and other debris. Don’t allow plant litter deposited by wind into corners or at the foundation of the house to accumulate - burning embers may easily collect in the same places! Trees. If trees have just a few branches within 10 feet of each other, prune them back. If adjacent trees have many branches crowding together, it may be time to thin out a few more trees. This will also improve the health of the remaining trees. Prune dead branches as needed. Cut seedlings periodically after they emerge in the understory.Grass. A green turf is very fire resistive, so if you can, keep your lawn well-watered through the summer. Longer watering cycles – 1-1.5” of water per week in 1-2 waterings will maintain a healthy sod for most soils. If you cannot keep the grass watered, keep it trimmed low, especially close to the house. At the edge of your landscape, establishing a low-maintenance, low-growing grass, such as sheep fescue or hard fescue (both of which are very competitive) will help reduce new tree or shrub establishment.Brush.Mechanical control. Fuel hazard from northern Idaho brush species can be reduced by cutting plants off at the base. Northern Idaho shrubs will frequently re-sprout vigorously from latent buds in the root crown (an adaptation to top removal by fire), especially on stems smaller than 2 inches thick. Repeated trimming is usually necessary to maintain reduced fire risk. Mid-summer is the best time to do this.
Depending on the job, a variety of tools can be used for mechanical control, ranging from loppers and pruning shears on smaller jobs, to chainsaws or clearing saws for multiple stems or stems larger than 1 inch. For smaller diameter stems, brush mowers, brush hogs, or similar devices may be used. Regardless of the tools used, take proper safety precautions (e.g., protective eyewear, chaps for chainsaw use, etc.)
Mulch. Mulch can help suppress understory plants but remember; bark, wood chips and other organic materials will burn -- keep them away from the base of structures (use rock or other non-flammable material instead). Do not make the mulch deeper than one inch, to avoid interference with root activity and tree health.
Livestock. Sheep or goats may also help maintain brush at a low level. Time grazing to late spring or early summer (not early spring) to minimize soil impacts. Later grazing also reduces plants’ ability to regenerate because of drier soils.Herbicides[i]. Herbicides control brush species efficiently, and if label directions are followed, the effects on other forest values (beyond removing the brush) are negligible. There are many methods of killing brush with herbicides, but the most common for landscape maintenance are stump treatments, basal bark treatments, and foliage treatments.
Herbicide Products. Several herbicide brands are sold to kill brush. Brush control herbicides available in local home & garden stores frequently include triclopyr (e.g., “Blackberry and Brush killer”, “Brush-B-Gon”) or glyphosate (e.g., “Round-up”). Brush control herbicides targeted to larger forest owners or commercial contractors for forest use are often packaged differently (e.g, in larger containers) and may have to be specially ordered. These herbicides include: imazpyr (e.g., “Arsenal”), glyphosate (e.g., “Accord”), 2,4-D, triclopyr (e.g., “Garlon”), picloram (e.g., “Tordon”), dicamba (“Banvel” or “Clarity”), or combinations of these (e.g., 2,4-D and triclopyr in “Crossbow”). Some of these herbicides have specific state regulations such as requiring an applicator’s license and restrictions on how close they can be applied to a home. The herbicide labels will list plants controlled by the herbicide.
Regardless of the herbicide, always read and precisely follow the label recommendations before purchasing and using it. For current recommendations for specific brush species, consult the Pacific Northwest (“PNW”) Weed Management Handbook, which is updated annually by Pacific Northwest Land Grant Universities and available online at: http://weeds.ippc.orst.edu/pnw/weeds.
[i] To simplify information, trade names have been used. No endorsement of named products is intended nor is criticism implied of similar products not mentioned. |
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What to look for this year. Yvonne C Barkley, Associate Extension Forester, University of Idaho
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