Proper microsite placement of seedlings depends on a number of factors, some of which are: site preparation method, soil texture, soil moisture and drainage, soil temperature, soil nutrients, competing vegetation, wind exposure and solar radiation. Placement of seedlings on the microsite that best promotes establishment and growth, varies from site to site and between species.
Root growth in the spruces (white spruce - all sites, black spruce upland sites), characterized by lateral root development, is best at the mineral soil/organic interface. Jack pine root development requires temperatures above 4.4° C in the upper 10 centimetres of soil. Jack pine typically produce deeper rooting systems than black spruce, white spruce and balsam fir.
Planting areas in Manitoba are usually site prepared to produce trenches or patches to facilitate easier planting, or otherwise left unprepared (see also: Site Preparation). On site prepared planting areas, there are a number of microsite placements associated with trenches or patches. These include:
All these spots have distinct advantages and disadvantages, and must be chosen based on the conditions existing on the site.
Table 1. Comparison of Planting Spots
(adapted from British Columbia FROA Memo No 099)
|Providing plantable spots||Poor||Good||Good|
|Increasing soil temperature||Moderate||Moderate||Good|
|Improving soil aeration||Good||n/a||Poor|
|Improving soil drainage||Good||n/a||Moderate|
|Increasing soil moisture availability||n/a||Moderate||Poor|
|Improving nutrient availability||Moderate||n/a||Moderate|
Preferred planting spots for black spruce on lowland sites consist of feathermoss, partly decomposed sphagnum peat, or live sphagnum moss, on fine mineral soils, site preparation should be designed to leave a layer of organic material over the mineral soil that the seedling is to be planted in. This practice reduces the risk of frost heaving (on silty and fine loamy soils), prevents desiccation (on silty and clayey soils), and retains nutrients (all soil textures). On coarse loamy soils, preferred planting spots include exposed mineral soil and mineral/organic mixtures. However, severe site preparation should be avoided.
Planting unprepared sites may be the only suitable option in some instances. Areas which are considered for this treatment should be amalgamated with larger planting contracts that include SIP areas. Including unprepared areas with prepared areas on planting contracts will reduce the overall costs of planting unprepared sites. Some examples of situations where this treatment may be useful are:
One of the most important considerations with unprepared sites is the planting spot or micro-site placement of seedlings. Planting spots must have the following attributes; mineral soil base, or mineral soil mixed with duff, or well decomposed duff that has lost its original structure, and clear of competing vegetation. Screefing or scalping duff and/or debris off a circular spot can achieve good micro-sites, approximately thirty centimetres in diameter, down to the preferred planting medium. Scalping or screefing can be done by hand using a planting shovel or mechanically with various scarifying tools mounted on a clearing saw. Additional time is required for scalping or screefing and these procedures increase the overall planting costs.
Planting unprepared sites does lead to difficulties in controlling planting quality and spacing. Special attention on planting quality is recommended on unprepared sites to ensure that seedlings have every possible advantage. Established natural, advanced or planted seedlings are often present on unprepared sites or plantations requiring refill and contribute to the sites stocking. Planting contracts which include unprepared or refill sites must define the spacing procedures to be taken by contractors and planters when established seedlings (natural or planted) are encountered. Planting on unprepared sites should be carried out shortly following harvest (less than one year). Planting spot conditions to be avoided are; rotten wood, logs, stumps, flooded depression, hummocks of loose soil, landings or compacted areas, and any plantable micro-site which is closer to established seedlings than what is allowed in the spacing requirements for the plantation.
In Manitoba, the recommendation is to keep the size of unprepared sites small (less than 10 hectares) and amalgamate these sites with larger SIP areas within planting contracts. Planting unprepared areas requires more supervision and time during the planting season, when both may be in short supply. This does not suggest that planting unprepared areas be avoided; rather that these areas not be a large proportion of regional planting programs.
Choosing stock type for planting programs depends on a number of factors. Selecting the stock type and species is done from five-year plans (harvesting plans, stock forecast plans) and when the site prescriptions are made.
Container Seedlings (both frozen overwinter and current crop are the two types of stock grown at the Pineland Forest Nursery in Manitoba) are used in all of Manitoba Conservation's Forest Renewal Programs. Up until 2001 a wide variety of bareroot seedlings were also used. Bareroot seedlings presented a number of problems from a planning perspective, for example, due to the likelihood of weather related mortality and seedling damage in exposed conditions over the bare- root stocks 3 or 4 years in outside nursery beds, and nursery inventory techniques it was difficult to know exactly how many seedlings (and of what quality) would actually be available. If shortfalls occurred there were limited opportunities for additional stock and areas would have to go unplanted for a year or more. The wide variety of container stock types, sizes and special characteristics have allowed for more choice and the opportunity to more precisely match the seedling to the site.
Site characteristics are important to consider when selecting species and stock type. Typically, these include:
Soil depth, texture, moisture, drainage, and rockiness is important when matching species silvics and stock type characteristics to the site. For example, sites with shallow soil or excessive rocks restrict planting depth, and it may be necessary to use container stock with short plugs or mini-plugs.
Plants compete for light, moisture and nutrients with each other and with planted stock. The amount and type of competition has a bearing on species and size of stock selected. Light shrub competition may be beneficial during initial establishment periods. This competition can protect stock from drought and desiccation damage as well as reducing initial grass competition. However, only shade tolerant species will persist through long term levels of light to moderate competition. Moderate to heavy grass competition can severely damage seedlings during the winter when the grass is flattened by snow, thus flattening planted stock. Larger stock is able to withstand winter loading better than smaller stock. As a general rule of thumb, larger stock performs better than smaller stock in competition. The composition of competing vegetation can be viewed as having long or short term effects, and will have an effect on the selection of species, stock type, and subsequent treatments.
Sites which are difficult to access may be better suited to frozen stock kept in a snow cache, for logistical reasons. Transportation problems during the planting season are avoided, and prompt execution of planting while stock is in an optimum physiological state is maintained.
Stock handling in the field has a significant effect on stock condition. A critical factor is the way the stock is stored after lifting and prior to planting. Some methods of stock storage are: refrigeration units, snow cache, heeling in, covering with tarp, and placing stock down in shade near a water source. The storage technique or combination of storage techniques depends on the characteristics of the planting program, the site, and the type of stock being planted.
Cold storage in the field is designed to keep stock at optimum physiological condition prior to planting. Presently, there are two cold storage techniques used in the field, these are:
The latter method is used when the planting sites that would be hard to access with large trucks during the planting. The snow cache techniques is described below.
Other factors concerning stock care and handling in the field are:
Shipment of stock from the nurseries to the field is mostly undertaken by refrigerated trailers (reefer units). The temperature in reefer units is kept between 1° to 3° C until stock has been removed for placement in a snow cache, cold storage facility or for planting. Reefer units can hold up to 300,000 seedlings depending on stock type and packaging. There may be some situations when reefer units serve as temporary cold storage facilities. When this occurs, condition of the stock should be checked every few days for mould and/or over-heating.
Short Haul Transport
Stock which must be hauled for short distances (less than 10 kilometres) should be covered by tarps to avoid wind damage which can cause excessive drying of shoots and lead to seedling mortality.
Stock (current container) which is not kept in cold storage prior to planting must be kept moist at all times. Container plugs should always drip water when it is squeezed by hand (sample plugs at the edge of container tray for dryness because the edges dry out first). Water only till water percolates from bottom of containers (plug saturation point). Overwatering is not serious, but watch for mould and cool weather. Water dipping the roots or wet moss in planting bags is more highly recommended than root dipping using gels to hold moisture.
The use of snow caches has been increasing as an alternative for truck based seedling delivery during planting. Snow caches use snow cover and an insulating layer to provide minimum temperature fluctuations (from -1° to +1° C) and high humidity conditions which are essential in maintaining physiological quality of the stock.
Snow caches are conveniently located at the planting site. Caches should be used where spring accessibility is greatly restricted (winter cuts areas) in order to maintain stock quality and reduce the cost of tree delivery during the planting program. Additionally, snow caches can be used to reduce the demand on cold storage facilities and refrigerated mobile trailers during the planting season.
One snow cache will store a reefer load (recommended size) of container stock, and can be completed in one day. Construction of the snow cache should take place from early to mid February when there is adequate snow available and temperatures are more moderate (-15° to -5° Celsius).
Align snow cache so that the opening of the cache will be facing north, and locate preferably on high ground to avoid spring flooding. Clear access to the site and a 3 metre corridor, at least one day prior to construction, in order to allow the reefer to back into the snow cache area for unloading and allow the ground directly beneath the cache to freeze. If the ground is not frozen, temperatures within the cache may fluctuate causing mould problems.
The reefer is backed-in to the end of the corridor where it is unloaded and moved forward as the boxes or bags are stacked. There should be at least 1 to 2 meters of snow between caches. Different types of stock must be kept separate and their location mapped with the amount indicated on the maps to assist when opening the caches for the planting program.
The bottom of the cache is lined with pallets or poles, otherwise if the ground is extremely frozen, 2 to 3 inches of sawdust can be placed over the ground to act as insulation. Bags or boxes are placed up to 6 wide and 3 high with a flat top (no plywood on top). Poles or stakes should be placed at the ends of the snow cache and to mark where the stock types are within the cache.
Cover the tops and sides (not bottom) with 6 millimetre plastic sheets, about 10 metres wide and 30 metres long. Staple the plastic to the pallets or poles. Cover the plastic with snow as soon as possible (definitely the day stock is placed out). Powdery snow must be used and piled to 1.2 metres (4 feet) on the sides and 0.6 metres (2 feet) on top.
Careful attention should be given to the corners and edges of the cache. Frozen or clumpy snow will cause crushing and air pockets, therefore should not be used to cover snow cache. Snow is covered with 15 centimetres (6 inches) of sawdust, woodchips, shavings or flax straw. Avoid leaving sawdust in truck overnight as it may clump up. Snow may be placed over sawdust to prevent blowing.
Building a snow cache will require about 4 to 7 workers to complete the unloading and construction.
Opening of the snow cache should take place at the north end and proceed inwards. The opening must always be marked. Container stock is removed at least one week prior to planting and set in a cool shaded location to thaw. Boxes used to package container stock can be opened while thawing, as long as they are placed out of direct sunlight. Openings are recovered immediately following the removal of stock to protect remaining stock left in the cache.
The planting methods and tools which are commonly used in Manitoba are described in the following paragraphs. Successful planting depends on the ability of the roots of planted trees to regain contact with the soil so that the uptake of water and nutrients can resume. Equipment and planting methods are directly related to the stock type and ground conditions where planting is taking place.
The treeplanter spade and the planting spear (modified spade) are recommended for container stock because they are less expensive to purchase, more dependable (less repairs), suitable for all soil types, and it avoids glazing or compaction to soil cavity (as evident with pottiputki and dibble). Other tools available are: shovels, planting mattock, for container stock - pottiputki, and planting bar. To find out where to order these planting tools consult the several equipment catalogues available from forestry equipment distributors.
The majority of planting in Manitoba is implemented through contractual agreements with tree planting specialists administered through the Forestry Branch Head Office and supervised by Regional Operations staff. To maintain provincial planting quality standards, an assessment procedure has been developed by the Forestry Branch. A detailed description of this type of assessment is included in Schedule D of the Planting Contract itself. (See: Information for Tree Planting Contractors.)
Planting quality assessments (PQA) are carried out systematically on the areas planted, usually at the intensity of one plot for every thousand trees planted. The field assessment form is filled out at every plot and includes: planting and assessment date, number of planted trees, planting quality codes for each planted tree appraised, and a spacing evaluation. Planting quality takes into account some basic planting principles, which are; planting spot selection, seedling placement, firmness, position of stem, exposed roots, and scalping or screefing if required.
The quality assessments are important and must be implemented correctly, as the results are used for calculating payments and subsequently invoices for contractors.