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A Total Forest Management Plan
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This section is based primarily on the work leading to the MS thesis of Donald Lee Francis, Va Tech, March, 1980.
Most people in the wildland sciences concentrate on the plants and animals. Few select as their primary interest the so-called "abiotic" factors such as temperature, geology, land topography, or wind. Animals and plants can be perceived to be functions of these things, controlled and influenced by their magnitude and stability. These are some of the environmental factors (but of course other plants and animals are also factors of the environment.) Staff hold that mastering the abiotic factors can give profound control over the topics of great interest, the plants and animals. Not to understand them intimately is not to know the trees or animals well. These are the factors that shape the populations, limit them, or enable them to change past some current or named condition. One way to understand "control "is to think of an animal or forest population in a simple model such as
Population = f (Wind) or a little more specifically,
Population = a + b Wind
When the manager changes the wind, then the population will change at the specified rates. When the manager changes wind, the dust and mineral inputs to systems will change. Wind, with water, provides the dust on rocks into which primary succession begins. The average estimated wind erosion is 3.6 tons per acre per year. (Anderson 1994:130). Riparian forest management (as filter strips can prevent sediment delivery to aquatic systems.
This is very simplistic but it suggests that the manager might be able to change the wind (for example, with wind barriers or "windbreaks" or simply change stem density. By knowing about the wind, the manager gains knowledge about what factors vary and by how much. Knowledge of variance is a type of control. The statistician will often express ability to model or to predict things in terms of how much control his or her models give over the variability within a system.
The manager is looking for knowledge as control, for understanding of system variance as control, and over the procedures for changing wind (or other abiotic forces) to get the managed population to change in desired ways, to reduce the gap between the desired state and the current state.
Eventually, the manager tends to believe that with knowledge of several of the abiotic forces, greater explanatory or predictive power can be gained for a wildland system. Perhaps it might fit into some equation such as
Population = f (wind, temperature, evapotranspiration, land form, land texture, aspects, elevation, slope, storm occurrence, soil texture, liquid precipitation, snow)
The population is a function of all of these. Predictability will be low, but much better over the long run than a guess, at least by neophytes. Having a model that approximates conditions can lead to improvements and eventually to improvements in predictability by improving the model. Excellent predictability may never be gained because of the inherent variability of the many parts of the system and the millions of possible sequences in which these factors may occur. Managers look for the" big handles", for the controlling factors, the things to use first to get the system under control cost effectively. Wind is likely to be one such factor.
It may make little difference, but knowing that "weather" is the set of atmospheric conditions that exist in the current moment or some specified time can be useful. "Climate" is a summary or generalization about past conditions and usually area-specific.
Agriculturists have long known the importance of wind. The areas of importance and significant influence (with few notes because they are evident) are:
Wind is not a single factor and it needs to be studied along with other climatic factors such as temperature, soil conditions (e.g., wet or frozen), and leaf-on or -off conditions. It is described by
Studies of wind are nearly impossible for there are very few weather stations that collect and maintain consistent records over long periods (only about 20 in Virginia). Generalizing from a few stations (usually flat airports) is dangerous. Ryan (1978) found wind highly variable in mountains. Gross weather data may be useful for the daily weather forecasts but have little value for the micro-habitat work of the local land owner or resource manager. Conversely, much research about wind around buildings and snow fences may be too small-scale for relevance in typical land use decisions. A mixture of needs suggests the need for several scales of work. Some needs are for isolating potential problems, others are for explaining differences in populations within areas, others are for comparing populations and isolating factors (like wind) which may help explain the differences observed.
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| A 30 x 30- cell GIS map (27-acre cells) showing wind flow (direction and intensity) over an area near Lynchburg, Virginia developed by Francis (1980, p.67). Grid cells are shown in the East-West and North-South Direction. There are about 800 such map areas for Virginia. |
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Basics
We concentrate only on ground winds, those within the so-called friction-layer of Earth. There are other mid and high altitude winds that are influential, and all are a function of pressure-gradient, coriolis, and centrifugal forces (Miller and Thompson 1970).
Plants
Daubenmire (1970) listed the effects of wind on plants. These included: carbon dioxide replenishment, cooling (far more important for plants than generally recognized), dessication, transpiration, dwarfing, deformation, anatomical modifications, lodging (grasses blown over but not broken), breakage, abrasion, erosion, salt spray, snow cover, pollination, and seed dissemination. Physical bending of trees by wind can reduce height growth by 80% (Neel et al. 1971). Wind influences type communities (e.g., wind-resistant beech forests in high-velocity gaps high in the Smokey Mts. (Russell(1953).
For the manager, the wind influences are depleting soil moisture (depletion is proportional to wind speed), increasing transpiration rates, dispersing seeds, and influencing soil erosion. Wind effects on soil moisture are greatest on bare soils, thus the need to establish cover quickly. Windbreaks can decrease runoff and evaporation and create an even distribution of snow (i.e., not blown into ravines). Portable windbreaks may provide an excellent means to help establish vegetation in areas with limited moistur (e.g., surface mine reclamation).
Office, storage, and recreational structures need to be built to withstand local winds (McDonald 1975, Grillo, 1960, Yokel et al. 1976). Anemometers on site may modify the wind so broad scale mapped information may be more useful over the longrun than brief onsite measurements. Buldligs can be oriented to cause summer cooling winds to move through them; similarly in cold climates, they can be oriented to minimize air flow, thus heating costs (Olgyay 1963). A well protected structure (architectural design with wind breaks) can save a house fuel bill some 23%- 30%. See Stephens (1977) on design and location of industries. Wildlife managers can combine good nesting and food sources among the plants selected for the wind barriers and deflectors
Knowledge of wind is essential for the resource manager who, sooner or later, must fight wildfires. Fires create an upward draft that can throw sparks 200-300 meters up to a kilometer ahead of a fire (Stoddard 1968). A fire weather index may be improved with local estimates of probable winds (Fosberg 1978). Wind may dry an area and reduce its site index. Combining wind maps with site index estsimates may yield improved site maps. Cuitting practices in the forest influence edges, turbulence over the forest, dispersal of seeds, depth of wind penetration into the forest, and energy budgets of animals in forest edge volumes.
The more the wind, the more the transpiration or moisture loss. Under very humid conditions, wind no longer has this influence.
Wind is a major agent in tree seed dispersal. Wind speed at the time of seed fall ("seed rain") can suggest to foresters the likely sources of seed for clearcuts areas or placing harvests to assure re-seeding.
New GIS maps of soil erodability by wind can be readily created and should be used to rank areas for protection, funds allocated for restoration, and risks of cultivation (Carreker 1966).
Windbreaks are effective in reducing wind erosion and serve other functions for wildlife, esthetics, and energy budgets as well. Damage to protected fields is far below than of areas without breaks (Budyko 1974). Large-scale mechanized farming has caused removal of many winbreaks (Radley 1967). Wind erosion is a slow, unseen enemy and major steps need to be taken to control it ( simple things like the cross-wind orientation of corn rows as well as creating elaborate well-designed windbreaks.)
Windbreaks are essential for effective reclamation of Appalachian mines and stabilizing other areas. They reduce evaporation, act as mulch and water barriers, provide shade, reduce temperatures, and enhance wildlife and esthetic benefits.
The following table presents relative costs and the benefits (wind-protection coverage) for types of windbreaks.
| Type of Windbreak | Cost | Benefit | B/C Ratio |
| Loose Shelterbelt | 6 | 406 | 67.67 |
| Medium Dense Shelterbelt | 10 | 477 | 47.40 |
| Very Dense Shelterbelt | 15 | 447 | 29.80 |
| 33% Woor Barrier | 10 | 261 | 26.10 |
| Triple Wood Barrier | 30 | 577 | 19.23 |
Wind knowledge will suggest air pollution dispersal, both the probability of it and well as directions and timing.
The "wind rose" a circular diagram can depict the frequency with which wind blows from every direction can be interesting and add a new dimemsion to understanding an area.
Wind patterns may suggest sites for future alternative electric power generators (the windier, the more efficient; Sorensen 1976, Aston 1977, Putnam 1948).
Fisheries and Winds
Wind aids in fall turnover of lakes and ponds, helping maintain proper oxygen levels. Windmills have been used to prevent ice forming in shallow lakes, thus reducing winter kill. Wind easily impacts fish that spawn in shallow water such as walleye and perch. Busch et al. (1975) found walleye reproduction well correlated with high winds. Perch eyys were dislodged and beached by high winds agitating shallow waters. Mean daily wind velocities were inversely correlated with perch survival. Winds can destroy large-mouth bass nests. Wind speed and direction influences fish movements and feeding habits (Holt et al. 1977). White bass (Morone chrysops engages in "frenzy feeding" in foam lines caused by wind-generated waves on Lake Mendota in Wisconsin (Pers. Comm. Dr. John Ney).
Perhaps windbreaks along the shores of ponds can be built to serve to protect the shallows where most damage occurs to nests and larval fish (and where beach erosion may be high).
Wind and Wildlife
Wind can be considered to move energy off the surface of an animal. It causes "convective heat loss". Moen (1973) quantified some of the influences of wind on deer and other animals. Food in the energy intake; wind the loss. Often losses may exceed intake. Surviving animals are those that can strike a good balance. Heat loss increases with wind velocity. Wind is more important that radiant energy in cold areas. "Cover" is often another expression for natural means for animals to reduce their heat losses, primarily from convection. Heyne (1968) found earthen windbreaks were excellent protection for cattle (suggesting similar roles for wildlife) in intensively managed areas. Clapper (1969) found windbreaks doubled the carrying capacity for cattle on a Nebraska ranch. Pronghorn antelope seek out bedding areas protected from high winds.
Built windbreaks have a zone of influence (width) about 10 times their height for excellent effect, 20 times the height for significant effects. Careful study and advice from experts on windbreaks should address porosity (density), spacing, height, and orientation (Caborn 1965). Good breaks filter the wind but do not block it completely (50-60% density is best). High breaks are good, but the higher, the more the shading effects and thus some cropping losses. Konstantinov(1969) calculated the orientations for windbreaks (rejecting the assumption of "right-angle is best."). Orientation is typically selected at right angles to the prevailing winds to achieve even distribution of snows.
Of possible use for transforming wind speeds : 0.447 meters per second = 1 mph
References
Francis, D.L. 1980. A computer-based wind information system for land use planning in Virginia, MS Thesis, VPI and SU, Blacksburg, Va.
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Last revision January 17, 2000.