Structural Complexity Enhancement

I was in Vermont for two days visiting Bill Keeton and Yurij Bihun to discuss my Fulbright project, and had the chance to visit Bill's Structural Complexity Enhancement (SCE) plots in the Mt. Mansfield State Forest. Bill developed this harvest method as a means of speeding the development of late-successional features in maturing stands. It uses variable density thinning to make small gaps, release midstory trees, and open up the crowns of canopy dominants, all while retaining the largest stems. Snags and CWD are deliberately 

created, and in some treatments trees are even pushed over to simulate windthow.

In adjacent plots there are traditional single-tree and group selection treatments, but with the residual

 basal area increased from normal and the max. diameter increased to 24 inches. This is meant to demonstrate how simply tweaking traditional harvest systems might enhance structural complexity, in comparison to the SCE method. 

I have to say, even the traditional treatments have some pretty impressive "big structure" (see right), but the vertical and horizontal diversity is noticeably lower. The SCE treatment is a jumble of small gaps, poletimber, snags and big canopy trees, arranged with none of the order and uniformity of selection. This is the point, and it is impressively "complex". Happily, Bill has found that sugar maple will regenerate in the tiny gaps created (and yellow birch will on the artificial tip-up mounds). Also, SCE actually benefits populations of late-successional herbs (they don't get overwhelmed by ruderals) and has boosted red-backed salamander populations due to more CWD. 

It is nice to see a couple of concrete biodiversity benefits from SCE. I have certainly seen how important old, complex stands can be for rare lichens. But the number of species that are actually dependent on such stands seems pretty low. For SCE and similar treatments to catch on, I think we would have to see how structural complexity benefits non-obligate species. Does it allow a greater breadth of successional guilds to use a stand at the same time? Could we effectively "pack in" more habitat value per stand by creating more structural diversity and more niches?