Things to keep in mind when managing your suger bush
How can you tell which maples have the best yield? Producers are using fewer buckets in their sugar bushes, so they’ve started to lose touch with the amount of sap one tree can produce. However, even without buckets, there are plenty of ways to estimate yield.
The first and probably most reliable clue is diameter. Sap yield and Brix levels tend to increase significantly with diameter. For example, the most recent studies available say that a maple tree that’s 32 in. in diameter at chest height (4 ft from the ground) will yield around 21 gallons of sap per season, while a 12 in. tree at the same height will yield only 7 gallons. The Brix level of the sap also generally increases with diameter, but to a much lesser extent; you can expect an average 0.1°Brix increase for every 4 in. increase in diameter.
Diameter isn’t the only indicator of yield, though. Growth in recent years, total height, and crown size also factor into the equation. The important thing to remember here is that it has been proven that the productivity of maple trees increases with their growth and size. This means that in your sugar bush, some maples will yield ½ pound of syrup per tap, while others will yield more than 10.
Wich maples are most likely to die during the next tubing rotation?
It was long thought that cankers and decay fungi were the biggest signs that a tree was likely to die in the short term. However, recent research has shown that crown dieback is by far the best indicator of impending tree death. More precisely, the likelihood of mortality appears to increase when a tree’s dieback is over 15% greater than the average dieback of the other trees. After crown dieback, the best indicators are cankers, then decay fungi, then defects (mechanical injuries, cracks) accompanied by rot.
But what is “dieback,” anyway? Crown dieback is characterized by the progressive death of twigs, starting from their tips. It can be caused by many different things, including unsuitable location, natural causes (drought, disease, insect infestation), or injury. Fortunately, once you know the main cause of the dieback, it can slowly be reversed. For instance, if the trees are dying because the soil is low in calcium, applying the right amount of lime can not only halt the dieback, but also increase the crown size.
When is the best time to clean a maple tree?
Maples aged 50 and under grow better when their crowns are cleaned. After the age of 50, the reaction is generally weaker. That said, cleaning a maple too early and too intensively will encourage forks and large branches to appear early. Those forks and branches are prone to breakage, especially during icy spells, which can provide an entry point for cankers and decay fungi. When developing a maple grove, you want to try to clear stems between 2 in. and 12 in. in diameter. Of course, you only want to do this on healthy trees whose crowns won’t die back.
How much should I clear to encourage regeneration?
Now that you know which stems to clean and which to cut, roughly how much of the bush should you clear to support the growth of the remaining stems and encourage regeneration? In terms of wood volume, it appears to be best to clear between 10 and 25% of the bush per 15- to 25-year period, depending on forest growth. This can be done all at once during tubing rotations, or gradually over the years. It’s best to avoid creating gaps whose diameter is greater than the height of the dominant trees (50 ft to 80 ft). Larger openings in the canopy will encourage competitive and even invasive species, to the detriment of the maples and other desirable companion species. At the same time, keeping too many trees will limit growth.
Wich species should I favour?
It’s generally agreed that it is preferable to favour sugar maple over red maple, and maples over other tree species in sugar bushes. What you need to know is that each tree species is adapted to specific climatic and edaphic (soil) conditions. For example, sugar maple thrives in rich (especially calcium-rich), well-drained soils. Red maple thrives in rich, well-drained soils as well, but also in wetter, poorer soils. A tree that grows outside its ideal environment will have poor growth and be more sensitive to disturbances like drought, insect infestations, or late frost.
The more diverse the sugar bush, the more resilient it will be to disturbances. That said, some companion species are better suited to sugar bushes than others. More specifically, yellow birch, basswood, hickory, oak, ash, black cherry, and chokecherry are good hardwood species to keep in your sugar bush. As for softwoods, spruce, pine, eastern hemlock, eastern white cedar, and tamarack are good companions for maples.
There are currently no studies indicating how many companion species should be kept in a sugar bush. However, it’s recommended that at least 15% of the site consist of companion species. On wet or very dry sites, it’s better to keep more, since they tend to be better suited to the conditions than maples.
In conclusion, by keeping an eye on diameter and crown health, and by controlling the surrounding species, maple producers can identify the most productive trees, maximize their yield, and keep their sugar bushes healthy in the long run.
About the APBB:
Founded in 1962, the Association des propriétaires de boisés de la Beauce (APBB) plays a leading role in the commercialization of wood from private forests. It represents 11,000 forest owners spread across 62 municipalities in 7 RCMs, and offers them training and information, as well as a wide range of consulting services in forest and sugar bush management. The Association is affiliated with the Fédération des producteurs forestiers du Québec (UPA).
In 2022, the APBB launched the Guide d’aménagement des érablières, written by two experts from its sugar bush department: Michaël Cliche, F.Eng. and Anne Boutin, F.Eng. The French-language guide is a compendium of up-to-date, easy-to-understand scientific information for maple producers. The APBB is also a member of the Créneau Acéricole and supported the creation of the PPAQ’s La Station acéricole podcast, to which it occasionally contributes.
Visit www.apbb.ca for more content.
