Summer of 2016 was a very dry season and excellent for forest harvesting in New England, and especially in New Hampshire. This is a good time to asses any positive impacts on our forests from current harvesting methods.
New England forestry appears to be most efficient when trees are removed in thinnings created by skidder trails alone. Once cutting equipment extends beyond the edge of the skidder trail edge, the reach of the equipment is limited and cutting is slowed by the care needed to harvest individual trees within stands. This reach is commonly used in all good forest harvesting systems.
Cut-to length contemporary systems are able to reach further into stands and thin stands of trees more efficiently than many other mechanical harvest methods. Regardless of the type of harvesting equipment, many non-overstory removal tree harvests in New England are made with a very high percentage of creation of skidder trails through the forests rather than removal of individual trees and small groups.
Changes in canopy cover from these methods increases light to the forest floor which can increase seedling germination and competition success for any intermediately shade tolerant or shade intolerant tree species. Effects may also include an increase in regeneration species diversity throughout each stand of timber. Additionally, standing timber may show a variety of responses to that type of treatment. Each tree species responds differently, and so this question is in relation to forest cover types most commonly found in New England.
Is creation primarily of skidder trails as a stand thinning treatment showing increase of residual timber basal area tree growth (including responses in forest health) within 10-acre or larger New England forest stands?
See: The Chapman-Richards Generalization of Von Bertalanffy's Growth Model for Basal Area Growth and Yield in Even - Aged Stands, Forest Science, Volume 19, Number 1, 1 March 1973, pp. 2-22(21).
This paper may help you to predict the basal area development of stands of different initial stocking and subsequent thinning regimes.
Thanks. Both comments and sources were helpful.
Mila
My thought is that testing this model would be difficult unless data was collected in a stand that was only partially harvested in the skidder-trails-only method, and that done long ago enough to show a measurable difference in growth. Otherwise its growth plots for years and years.
Second reply to Andrew: I have seen and even tried a growth model similar to this, but it seems to me things would differ from one specie to the next with these models. They seem too constraining without specie differences. And I have certainly known of stands managed with a growth prediction based on the expectations of the stand type. How do species differences in these models get considered?
Mila
Reply to Bruno: The trees I think of most for this question are slow-growth stands, so this is particularly interesting. Thanks.
Just an update to the question, rather than an answer: I was visiting a few oak stands this December where acorns were rolled into the soils in winter by harvesting equipment and skidders. A particularly good example, there are quite an amount of small oak seedlings where the increased light is sufficient.
This seems to have been the case in a summer pine harvest, all of which agrees with what I've been told about responses to use of harvest equipment in a forest that was had a high stem density before harvest.
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