All methods may be judged according to whether they succeed in meeting the ecological requirements of the proposed crop. Each method is good where it is properly used, and poor where it doesn't solve the entire set of problems. Any can result in having to use follow-up treatment. The set of practices discussed will not be described in sufficient detail to recommend without first making a specific environmental analysis of need. A professional recommends a method only after evaluating each alternative in the context of the set of circumstances involving the brush or slash problem, available planting stock, animal problems, and so forth. The choice of method is only a small part of the prescription and is of interest only when discussed along with the rest of the problem set.

Site preparation methods for brush or slash include machine scarification and variations of machinery, fire, herbicides plus fire, hand slashing, and various combinations of fire, hand, and chemical procedures. They do different jobs; given the same problem, they produce different results. Often several will produce surviving trees but will differ in subsequent maintenance, or in soil damage, or in watershed protection. Some are used for combining wildlife damage protection with vegetation control, etc. You must think through exactly what is actually accomplished, including the invisible; you must project the plant community that will result through the years when it will be competing.

As a general principle, species differ in their requirements for seedbed; some prefer disturbance and others undisturbed forest floor. Breaking the soil surface invites immigrants. Fire invites others. Complete chemical control of vegetation is slower to recolonize. These differences are attributable to physical differences in procedure, except where herbicides with long residual activities are used. The different approaches, therefore, lead to different successional patterns that can be anticipated and adapted to the species being regenerated.

Take a look at mehcanical site prep using a VH Mulcher

For purposes of this course, mechanical site preparation may be defined as treatment of the site with powered machinery to:

a) remove dead debris or living plant cover to facilitate planting;
b) create drainage to lower excessively high water tables;
c) create raised areas or mounds in regions with cold soils to provide rooting media with more favorable temperatures for root growth;
d) create depressions in regions with summer drought to permit seedling roots to be planted in lower soil horizons.

To the extent that the chosen equipment is capable of any or all of the above, it may be considered a potentially valuable adjunct to a reforestation project. However, the forester should be aware that while proper use of powered equipment may greatly facilitate reforestation, improper use may create more problems than it solves. For example:

a) use of scarification devices in areas supporting aggressive competing vegetation characterized by light, wind-blown seeds will create a seed bed favorable not only for the desired coniferous seedlings but also for the competitors. And since most "weed" species have much greater growth potential than that of tree seedlings, the end result of such practices is a plantation which is either lost to competing vegetation or which must be "released," probably through the use of chemicals;
b) use of brush rakes or other ripping devices in a community of "sprouters." Again, the short term result may be a very favorable site for a coniferous seedling, but such equipment frequently breaks roots into small pieces which greatly increases the potential competition as a result of sprouting;
c) any soil movement in an area which has supported a vegetative community characterized by long-lived seeds. Soil movement in such a case will bring to the surface dormant seeds which will germinate and compete strongly with tree seedlings. Communities dominated by manzanita or ceanothus species or thimbleberry are examples of this response;
d) use of heavy equipment on soils with a high potential for compaction, or on any soils with a high water content, may well create very unfavorable conditions for future seedling growth. Use of heavy equipment during the harvest of black spruce in eastern Canada is considered by many to have greatly reduced the occurrence of natural regeneration.

Coastal British Columbia (Vancouver Forest Region and Coastal Prince Rupert Forest Region). By far the most commonly used site preparation technique in coastal British Columbia is fire. In the period 1985-87, 85% of the area which received site preparation, 5,700 ha, was burned at an average cost of $309/ha.

Only 9% of the area which received site preparation (2.5% of area harvested) was treated by mechanical equipment at an average cost of $532/ha. Equipment used varied with the timber harvested. On old growth settings which commonly had heavy slash loadings, small excavators mounted on caterpillar 205 or 215 (or equivalents of other manufacturers) were used to create small cleared planting spots. Production rates varied from 0.75 to 2.5 ha per eight hour shift at costs ranging from $350 to over $600 per hectare. Second growth settings, which generally had lower slash loadings, were cleared with brush blades. However, this treatment frequently stimulated subsequent brush invasion which required further treatment after planting.

Northern Interior (Interior Prince Rupert and Prince George Forest Regions). As in coastal British Columbia, burning was the most commonly used site preparation technique in the interior with 48% of the areas which received site preparation being burned at an average cost of about $130/ha. However, mechanical site preparation was much more widely used in the interior than on the coast with 33% of the area site prepared (27% of area harvested). A number of different machines were employed, with the choice dependent upon the modification of the planting microsite, i.e., soil temperature, moisture or aeration, soil structure, vegetation control, desired.

a) Mounders. A range of mounders, Bracke, Sinkkila, Ministry, were employed. All these machines create raised mounds consisting of mineral soil over a single or double layer of organic material. The goal is twofold: control competing vegetation and prepare a planting spot which has elevated soil temperatures and, in areas with high water tables, improved drainage. Mounds warm up faster in the spring and have higher temperatures during the day, but cool down more than untreated areas at night an during the fall. Mounds dry out more than unmounded soils so to prevent excess drying, they should have a low profile and large top surface. Cost of mounding is about $200/ha.

There are three basic mound types: inverted humus mound (Figure 14); mineral mounds, Figure 15, created by first removing the organic layer and placing a mound of mineral soil directly on the exposed soil; and mixed mounds (Figure 15) formed from intermingled mineral soil and organic materials. This mixed

FIGURE 14 Stylized inverted humus mound.

FIGURE 15 Stylized mineral and mixed mounds. (After Haeussler, 1989)

material may be deposited either on top of the residual organic layer or on mineral soil exposed by scalping.

The inverted humus mounds are best for nutritionally poor sites because this configuration concentrates nutrients present in the organic layers. This type of mound is not recommended for droughty sites, as they have no capillary connection with the soil matrix and hence dry rapidly, or for sites with deep, loose duff. The mineral mounds are recommended for cold but slightly drought-prone sites and are not recommended for nutrient poor areas. The mixed mounds are best for slightly drought-prone, nutrient poor sites but are not recommended for sites with abundant competing vegetation because the capping of the mound is a favorable medium for growth and contains inoculum (i.e., roots, rhizomes) which can re-establish the competing plants. Care should be taken during the mounding process to avoid creating large chunks of organic matter which could result in air pockets. Because construction of mounds disrupts the normal movement of moisture through soil capillaries, none of the above mounds is recommended for droughty sites.

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Figure 16 summarizes the possible planting positions in a mounded area. a) Planting at "1" will maximize the benefits derived from increased soil temperature but will also be the most droughty microsite. In areas with high water tables, it is favored because of the increased aeration produced by the construction of a mound. b) Planting at "2" affords the seedling the maximum release from competing vegetation but does not provide increased soil temperature or aeration. c) Planting at "3" is recommended only in coarse soils in a droughty site.

Current costs of mounding in the northern interior where slash accumulations have been windrowed are approximately $200 per hectare. It should be recognized, however, that in the case of mounding and other mechanical site preparation treatments, at least part and possibly all of the site preparation costs may be recovered by the decreased planting costs associated with such micro-site preparation. Further, planters have commented that well prepared sites reduce planter fatigue and permit uniformly high planting quality.

FIGURE 16 Planting positions on a mounded area: 1) top of overturn; 2) base of overturn (hinge); 3) bottom of scalp; 4) control. (After Konowalyk and Fast, 1989)

Material on the following six pages is from a draft of FRDA Memo No. 100, July 1989 compiled by S. Haeussler, R.P.F., Skeena Forestry Consultants, Smithers, B.C. (I have retained this material because while in detail it may not be pertinent to Oregon practice, the principles illustrated are universal.)

b) Drag-scarification. Least expensive type of mechanical site preparation ($70-$175/ha). This technique is used primarily in lodgepole pine types in the Prince George region. The concept is to drag equipment capable of surface scarification , i.e., sharkfin barrels, spiked anchor chain, worn out tractor pads, etc., behind a prime mover to expose a mineral seed bed. Technique is primarily designed to foster natural regeneration of lodgepole pine and may not be successful in areas such as the interior of the Prince Rupert Region where soil temperatures are seldom high enough to stimulate the opening of lodgepole pine serotinous cones. However, the technique does maximize the likelihood of pine regeneration by exposing a favorable seed bed and by crushing down slash so that the cones are in intimate contact with the soil surface, usually the hottest microsite.

c) Patch scarifiers (Bracker, Leno). These machines are pulled behind a prime mover, often a skidder. The mattock tines of these machines are intermittently dragged through the upper soil to remove the organic layer and thus expose the mineral soil (Figure 17). The scarifiers provide a flexible site preparation system and are relatively inexpensive to operate ($70-$140/ha). Their disadvantages are that they may not penetrate compacted soil, cannot be used effectively in ares of heavy slash (although the skidder can be fitted with a blade to move slash) and the patches created do not provide effective long term vegetation control, particularly in moist rich sites with aggressive competing vegetation.

FIGURE 17 Stylized diagram of a patch created by a Bracke Badger. (After Konowalyk and Fast, 1989)

Research in British Columbia has demonstrated that if mounds are to be effective, they should be constructed with 10-15 cm of mineral soil topping. The "mound" associated with the Bracke patch shown in Figure 17 has no such capping but is composed largely of the organic layer removed from the patch. None-the-less, studies over six to eight years in Alberta show that while seedlings planted in position 3 made the best early growth, seedlings planted at position 1 were generally superior. The explanation offered is that early in the seedling's establishment period, access to water was the critical factor, whereas in subsequent years the higher temperatures and greater nutrient resources available in the "mound" permitted greater seedling growth. In trials which are now 2-3 years old in British Columbia, seedlings planted in the Bracke scarified trials made better relative growth in the relatively dry SBSdw3 subzone than they did in the wetter SBSj2 variant.

d) Disc Trenchers. These machines produce furrows which provide a continuous range of planting sites suitable for site specific prescriptions. Planting spots at position 2 (Figure 18) are suitable for well-drained xeric to submesic sites but may become waterlogged on subhygric to hygric sites. Planting at position 1 provides a somewhat raised micro-site with increased soil temperatures, and the seedlings have access to the nutrients in the overturned surface material in the berm. However, the partially mixed nature of the berms can stimulate luxuriant plant growth on the sites prone to competing vegetation. There are three types of disc trencher available in British Columbia: a) passive; weight of discs provides the only downward force; b) variable down-pressure discs; although these discs are freewheeling, the operator has a hydraulic control which may be utilized to force the discs down; c) variable pressure,

FIGURE 18 Stylized diagram of the site preparation created by a Donaren disc trencher (after Konowalyk and Fast, 1989). The figure represents effect of a single disc. Commonly the discs are employed in pairs which create a berm on each side of the trench.

powered discs; this machine has both hydraulic control of the down pressure and independently controlled power to turn the discs so that they are not dependent upon the forward motion of the prime mover. In general, the passive discs should be confined to the less demanding sites while the variable pressure powered discs are capable of creating good microsites on difficult terrain. Operational costs of the discs are similar ($70-$140/ha) to the patch scarifiers, but planters indicate that the much easier planting conditions created by the discs compared to untreated ground results in reduced planting costs which may compensate for the majority of the costs incurred in the operation of the discs. And, as in the case with the mounds, the greater ease of planting provided by the disced area results in generally superior planting quality.

The following three pages are from a draft of FRDA Memo No. 099 compiles by Laing and McCulloch Forest Management Services, Smithers, B.C. (1989).

e) Plows. A range of plows has been employed in site preparation projects (front mounted plows such as the C. & H. or Balco, a breaking plow, Eden Relief Bedding plow, rear mounted ripper plow). Such equipment is generally more expensive to operate ($210-$450/ha) than the previously described machines and probably has a more severe effect upon the site.

Data from Alberta demonstrate that seedlings planted in areas prepared by the Marttinni plow (Figure 19) had the best growth if planted on the top of the berm (no. 1) where soil temperature and nutrient regime were highest. Seedling growth was least at position no. 3, the slop of the trench, but seedling microsite did not affect seedling survival significantly.

FIGURE 19 Stylized diagram of site preparation treatment with the Marttinni plow. (After Konowalyk & Fast, 1989).

Figure 20 illustrates the effects of a ripper plow alone and with subsequent treatment by an Eden Relief Bedding plow. The ripping plow is best employed to improve soil drainage, aeration, and porosity and to increase the available rooting depth in areas characterized by impermeable sub-surface soil horizons (lodgepole pine black spruce types which make up about 30% of the Prince George region). The bedding plow was used to provide a raised planting spot and to provide a mixed mineral/organic matter seed bed with better aeration and higher temperatures.

FIGURE 20 Stylized diagram of site preparation with a rear mounted ripper plow alone and followed by an Eden Reliefe Bedding Plow. Channels resulting from the ripping which appear empty are actually full of fractured soil. The plows generally require more power than other site preparation equipment so are used with crawler tractors as prime movers.

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f) Rotary cultivators. The Madge Rotoclear consists of a heavy rotor and power pack mounted on a wheeled trailer and towed by a large crawler tractor. It can chop up to about 10 cm in diameter and mix it into the soil in a layer about 15 cm deep. The resulting seed bed is ideal for planting, and the treatment affords the best control of competing vegetation of any mechanical site preparation technique employed in the interior of British Columbia. Disadvantages associated with this equipment are that it is not effective in rocky areas or where there are numerous large stumps, and it might stimulate too rapid breakdown of organic materials which could result in nutrient deficiencies later in the rotation. A final drawback is that the Madge is the most expensive of the mechanical site preparation equipment to operate with costs ranging from $400 to $500/ha. If only strips are prepared rather than the entire area, costs may be reduced to about $200/ha.

Southern Interior (Caribou, Kamploops, Nelson Forest Regions). Compared to the northern interior region, the southern interior is characterized by a higher proportion of steep slopes, a greater number of commercial tree species and a greater proportion of partial cut harvest methods. The area is generally warmer and drier than the northern region, although the higher elevation spruce types are characterized by cold soils. A smaller proportion of the areas harvested each year receive some type of site preparation (60%) than in the north, but, as in the remainder of British Columbia, fire is the most common site preparation technique employed with about 60% of the site prepared areas being burned. Mechanical site preparation accounts for about 37% of the total area prepared with chemical techniques accounting for the remainder. Equipment used for site preparation in the southern interior is generally the same as described for the north. However, the greater incidence of slopes mandates greater use of V-plows, ripper plows, and drags with crawler tractors as the prime movers. Consequently, there is much less use of mounders, patch scarifiers, or disc trenchers, all of which are best adapted to relatively level ground. Costs are similar to those discussed for the northern interior save that site preparation on slopes is more expensive and therefore equipment used with crawler tractors may cost as much as $600 to site prepare a hectare. The southern interior is the only part of the province where consideration must be taken for conservation of moisture; accordingly seedlings are commonly planted in the depressions or furrows created by equipment rather than on the berms.

The foregoing descriptions of site preparation techniques has addressed them as individual alternatives for achieving optimum conditions for coniferous seedling survival and growth. In actuality, they are frequently used in association with other forms of environmental management such as fire, chemicals, or even manual techniques. When this is true in British Columbia, such combinations of site preparation methodologies are generally employed in series, i.e., burn, mechanically site prep, chemical vegetation management. In contrast, in Sweden, as Figure 21 illustrates, a single setting may be treated with a range of site preparation and planting procedures. If foresters in British Columbia wish to achieve maximum efficiency in the regeneration phase of silviculture, they would be wise to follow the Swedish example, where appropriate, in the preparation of preharvest silvicultural prescriptions.

FIGURE 21 Multiple regeneration strategies for a single forest opening. (After Fryck, 1986) as cited by Hunt and McMinn, 1988.

In addition to the above, the following equipment has been frequently used in other parts of North America.

1) In Pacific Northwest states.
a) Trac-Mac, hydro-ax, flail machines. This equipment is used to masticate slash or woody brush. Generally limited to slopes of 30% or less.
b) Dishpanner, Tomahawk and other spot site preparation equipment.
c) High-lead scarifier, limited to knocking down brush on steep slopes.

2) In South
a) K-G blade - shears stumps, piles debris.
b) Tree crusher. Crushes slash down, facilitates either burning or decomposition. Also employed on the K.C. Irving holdings in New Brunswick.
c) Anchor chains. Pulled by prime movers. Effective in light slash, duff. Also used in Alberta for scarification in lodgepole pine, jack pine types.

1. Limitations
a) Where grass is a problem, machines aggravate it.
b) Where pocket gophers are a problem, disturbance may increase levels of activity.
c) Where fertility is locked up in surface few inches, removal of surface soil to slash piles will reduce effective site quality.
d) Where suckering brush species abound, they continue to abound with little reduction in vigor.
e) Should not be done except when soils are very dry. Particularly true in areas of the South and Canada characterized by high water tables.

2. Suitability
a) Effective in clearing and improving plantability.
b) Effective in crushing slash, vegetation without removing it, offering protection from browsers (this can backfire in presence of rodents).
c) Easiest of all programs to administer, because operator is able to judge the quality of job he's doing.
d) Has not yet been identified as "controversial."

In British Columbia there are four general problems in seedling establishment which have been addressed with mechanical site preparation methods:

1. Excessive quantities of slash such that only a minimum number of planting sites are available without moving some of the slash. This problem obtains primarily in coastal British Columbia where Feric currently has a program of development and testing suitable machinery.

2. Hot, dry slopes primarily in the southern interior where some trials of patch scarifiers to create small depressions with seedlings planted at the low point of such excavations have been conducted.

3. Cold soils with high water tables, primarily in the northern interior. A number of patch scarifying machines which create small mounds and plows which produce raised berms between furrows have been tested. Such techniques are designed to produce rooting zones with warmer, drier soils than those on untreated sites. Long term effects of such treatments are not known. It is possible that plantations planted in such raised spots may be unstable if the roots do not extend to the less favorable rooting zones below the mounds or berms.

4. In lodgepole pine stands where various intensities of soil surface scarification have been employed to facilitate natural regeneration.

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