Tapping and collecting sap from birch
trees (Betula, sp.) for the
production of beverages and syrup is gaining increased levels of interest. Although
the practice of tapping birch trees and collecting sap has been ongoing for
millennia across the world, there remain some critical data needed in order to
make science-based decisions about the production practices required to
optimize yields and ensure sustainable outcomes are achieved in the long-term.
In this study, experiments
were conducted to determine two pieces of information essential to identify
practices necessary to ensure tapping trees for birch sap collection were both
sustainable and profitable—the selection of the time to initiate tapping birch
trees to obtain maximum yields, and the volume of nonconductive wood (NCW)
associated with taphole wounds in birch trees.
The yields obtained
from various timing treatments varied between sapflow seasons, but indicated
that using test tapholes to choose the appropriate time to initiate tapping was
likely to result in optimum yields from birch trees. The volume of NCW
associated with taphole wounds in birch trees was highly variable and generally
quite large, averaging 220 times the volume of the taphole drilled, and requiring
relatively high radial growth rates to maintain NCW at sustainable levels over
the long-term. However, more conservative tapping practices, including reduced
taphole depth and increased dropline length, as well as thinning and other
stand management practices, can be used to reduce the minimum growth rates
required.
In conclusion, producers should evaluate the growth rates of birch trees to be
tapped for sap collection to ensure sustainability of tapping practices, and,
if necessary, modify tapping practices to increase the likelihood of
sustainability—increasing dropline length and reducing tapping depth can reduce
the accumulation of NCW. And producers can
use the information to ensure that they use tapping practices that will result
in sustainable outcomes and obtain the maximum possible sap yields from their
trees.
Article by Abby
K. van den Berg, et al, from USA.
Full access: http://mrw.so/3fsD87
Image by benmillett, from Flickr-cc.
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