In an earlier post, Why and When to Cultivate Your Forest, we included handy information from one of our favourite resources, and promised to follow up with future posts outlining specific stand tending treatments. Always ones to keep our word, here’s the latest addition to our Stand Tending 101 series.
Brushing is the first, and in some ways most important, stand treatment you’ll carry out. If you’re not familiar with the term: brushing describes the removal of unwanted vegetation (brush) from the immediate area surrounding your seedlings.
Competition for light, nutrients and water from other vegetation at the early stage in a tree’s life (2 to 5 years after regeneration) can pose a real threat to growth and survival. By reducing competition at the beginning of the crop cycle you can help your trees become firmly established.
Like most of your management planning, your brush control strategy begins long before stands are harvested and the brush actually appears. Prior to logging, a silviculture assessment is carried out to determine the appropriate silvicultural system by which the stand will be harvested, reforested and tended. The assessment predicts, among other things, the potential for brush.
Sites that are ‘good’ for growing trees are also ‘good’ for growing brush; as a result, brush may be a bigger problem on your better sites. A combination of site preparation followed by the planting of large seedling stock is generally recommended for sites where extreme brush problems are anticipated.
The best form of brushing is no brushing at all.
With careful planning and a few simple practices you can significantly minimize the amount of brush you have to manage. Here are a few suggestions:
- Plant trees as soon as practicable after harvesting – this gives seedlings a head-start on brush and dramatically increases their chances of survival, while decreasing the chance you’ll have to deal with competing vegetation.
- Remove the seed source of undesirable species (red alder and hemlock are particularly prolific seed-producers). If you’re not planning to reforest with these species, remove mature seed-producing trees to the fullest extent possible.
- Minimize ground disturbance. Seeds thrive in a ‘seed bed’. By using designated skid trails, harvesting on snow pack or working with equipment that minimizes ground disturbance you limit the amount of ‘seed bed’ you create for unwanted brush species.
What to do if brush problems arise?
Despite your best efforts to prevent brush problems before they arise, you should be prepared to carry out brushing if problems do develop. Remember: it’s important to treat your stands before brush competition starts to suppress seedling growth.
Brushing is achieved by a number of treatment methods and techniques, including:
- Manual — hand cutting, pulling, girdling, covering brush saws, chainsaws
- Biological — grazing
- Chemical — careful use of herbicides through aerial, backpack or roadside spraying, or individual stem injection
- Mechanical — site preparation or brushing using heavy equipment
Manual brushing is often selected for sensitive sites, like streams or recreation areas, or when brush is a problem only in specific areas of your woodland. It’s usually done during the spring or summer months when the brush species are most sensitive to treatment. Manual brushing is labour-intensive and can be expensive if you have a large area or need to repeat brushing treatments.
The primary purpose of manual brushing is to encourage light to reach seedlings. The goal is to assist the seedlings to grow strong, healthy root systems and stems that allow them to fend for themselves. Timing is crucial. You want to brush sufficiently early in the growing season to allow your tree seedlings time to respond.
Manual brushing also ensures your seedlings aren’t smothered by surrounding vegetation and snow as they head into the dormant season, and not buried by brush when the next growing season begins.
Studies show repeated manual cutting, especially of grasses, can actually retard tree seedling growth because competition for water and nutrients is increased. In such circumstances, on a small scale, mulching will give better results than repeated brushing treatments.
Remember: brush species are pioneer plants whose successional role is to quickly and extensively occupy sites cleared of vegetation. These plants and shrubs are hardy and though you may kill off one year’s growth or even individual plants, they are capable of sprouting, seeding, and re-establishing themselves on a site within a short period of time.
In some areas, the grazing of sheep is still used as a means of brush control and can be very effective. The keys to success include:
- Choose the right site: suitable to sheep grazing with appropriate forage, a slight to moderate slopes, minimal debris and a low threat of predators.
- Select the right sheep for the job and an experienced shepherd.
- Timing is crucial: the target vegetation must be palatable and in sufficient quantity.
During grazing animals should be moved frequently to avoid over grazing and increased seedling damage from browse damage and/or trampling. The smaller and weaker the seedling, the more vulnerable it is. For this reason, grazing should be delayed until three or four years after planting, when the seedlings are large enough to be seen (and hopefully avoided) and more able to withstand damage.
If you choose grazing as a brush control technique you should also consider:
- Wildlife concerns, either through displacement or predator conflict.
- Water contamination if livestock are allowed direct access to streams and lakes.
- Soil erosion, compaction or displacement due to overcrowding too many animals into one area for an extended period of time.
- Transfer of undesirable plant species to forest sites.
Where brush is widespread or persistent, herbicides are often chosen as the most effective control method. Herbicides are commonly applied by air or ground. The ground methods include:
- Foliar spraying backpack or vehicle-mounted sprayers with hand-held nozzles.
- Cut-surface application of herbicide to individual trees by injection (e.g. hack and squirt), or to the surface of freshly-cut stumps
- Soil application of granular or pellet herbicides over the root systems of target brush species
- Basal spraying
It’s important careful consideration be given to the choice of herbicide and the method and timing of application. Relatively few herbicides are available for forest use and registration changes from time to time. You’re advised to check with local silviculturists, as well as the district office of the Ministry of Forests when considering herbicide application.
Mechanical brushing methods are most commonly used during site preparation to remove brush prior to regeneration. Heavy equipment such as excavators (hoes), tractors or skidders are mounted with special plows or cutters to clear brush and prepare the seedbed.
How to know what method of brush control is right for your stands?
The selection of the best method for your woodland depends on site and stand conditions, as well as environmental factors. In assessing the situation be sure to look at both the brush species and crop tree species.
Consider things like:
- How fast does the brush grow? What’s the maximum height it will reach? Versus: How fast are your seedlings growing?
- What is your crop tree’s ability to withstand competition?
- Do you have enough seedlings to meet stocking standards, or should you carry out a whole site treatment and start the establishment phase (reforestation) over again?
Also think about:
- What are your treatment objectives? (e.g. complete control, increase light to understorey conifers, decrease competition for moisture)
- What are your site constraints? (e.g. slope, accessibility, streamside)
- What species do you want to remove and where they are located? (e.g. trouble spots, sensitive areas, everywhere)
- Cost alternatives (especially labour if you’re not doing the work yourself)
- Other management considerations (e.g. domestic stock, wildlife and fish habitat, recreation and watershed values)
Thanks again to the creators of Managing Your Woodland: A Non-forester’s Guide to Small-scale Forestry in British Columbia for the information we’ve excerpted above.
Keep on the look out for future posts outlining the specifics of stand tending treatments—brushing, spacing, thinning, fertilizing and more. If you can’t wait, the complete resource is available online.