This ongoing podcast features interviews with researchers and educators about topics related to maple production and marketing.
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An examination of why and how maple sugarmakers can make their operations carbon-neutral.
Business is booming if you own a commercial sugar bush! As forest managers, this means more and more of us are hearing from landowners interested in starting or maintaining a sugar bush. Unfortunately, if you are like us, you did not learn about maple syrup in forestry school. This episode’s guest, Mark Isselhardt, Extension Maple Specialist with the University of Vermont, helps us unpack the fundamentals of sap production, sugar bush management, and how the industry has changed in the 21st century.
Guidelines for tapping maple trees have existed for well over 100 years. Early tapping guidelines came about when buckets (gravity collection) were the only technology available for harvesting sap. New tapping guidelines are based on years of research into maple tree growth, sap harvesting practices/technology and a recognition that tree diameter alone does not fully explain all the factors that determine if tapping intensity in a given sugarbush is sustainable. This fact sheet presents sustainable tapping guidelines.
Without a freeze, the flow of sap will continue to slow and eventually stop because there is no longer a difference between the pressure inside and outside of the tree. However, producers often observe an uptick in sap flow during the daytime over a few days. Why does this occur? Where did the extra sap come from? Typically, these short bursts of increased sap flow happen when the temperature warms over the next few days. The warm temperature causes gas bubbles in the wood fibers to expand and squeeze more water from the wood tissues, where it flows into the vessels and out through the taphole. This might occur for a couple of days, and eventually turn into slow weeping flows before ceasing entirely.
Vacuum and gravity “pull” sap down lateral lines. Friction “uses up” energy. The energy that is lost in this case is vacuum (gravity is constant). Reducing friction in the tubing system preserves energy and preserves vacuum further up the line. If making tubing larger or smoother due to cost or implementation issues, the next best way to reduce friction in tubing is to reduce turbulence, especially at fittings. This can be readily achieved through two simple modifications. The first method is to incorporate a bevel into the entrance and exit of all fittings. The second modification is to incorporate an arc where sap streams meet.
While there are both good and bad impacts on maple syrup producers due to climate change, overall, the effects will be negative. On the plus side, longer summers mean longer growing seasons for maple trees. However, regionally this longer growing season will increasingly be accompanied by periods of extended drought – particularly in more southern latitudes. This in turn may hinder root growth and performance. As maple syrup producers we are aware that anything which negatively effects maple tree roots is a concern because the roots are the origin for sap movement in the spring.
The area of stained sapwood associated with tapping or other wounds in maple trunks has long been interpreted to represent the area of wood that is compartmentalized, and thus unavailable for sap flow. We tested this interpretation by passing dye through maple stems that had been tapped and observing the area that was blocked. Our results indicate that the blocked portion of the trunk associated with a wound taphole is somewhat larger than the area which is visually compartmentalized (stained).
Over the past five years we have examined several different approaches to reducing the restriction in sap flow from shallow tree rings in an attempt to increase sap yield and sugar content of collected sap. After exploratory research in 2018 and 2019, we settled upon a basic design starting in 2020 that in continued testing has proved successful. The two main features of this new spout include a shorter barrel and barbs.
Ten years ago, 3/16” diameter tubing was introduced to the marketplace as an alternative tubing to 5/16” diameter tubing. However, recent research shows that sap production in 3/16” tubing drops off as soon as the second year after installation due to microbial growth. A replacement for 3/16” diameter tubing in gravity systems could be 1/4” tubing. With almost twice the aperture of 3/16” tubing (0.049 sq inches compared to 0.0275 sq inches), 1/4″ inch tubing is less likely to plug from microbes yet is still able to create a full column of sap for gravity vacuum. Quarter-inch tubing is currently not available for maple producers but can be procured from other industries and, with modifications, will work for maple production.