My understanding is that trees (box elder and willow in particular) are removed to promote bank stability and to make the channel narrower and deeper. Box elder destabilize banks and result in erosion and a channel that becomes wider and shallower. Wide and shallow channels lack adequate trout habitat and are at risk of warming. While restored streams may lack tree shading and woody structure from fallen trees, they do have cover from riparian grasses and deeper channels.
I don't doubt that some people promote the removal of trees to increase primary productivity or to improve fishability of streams, but I think promoting bank stability and reducing erosion is the most important reason we do it.
I like the work that was done on Big Spring across from Spurgeon Vineyards. There are now a series of deep pools that seem to be getting deeper following flooding events. I've attached a picture of one of the many nice trout we caught there last week.
I recognize that tree removal does make for easier fly fishing. But anglers are not always accommodated. When Dave Vetrano directed restoration work on Coon Creek, lots of trees were removed (and a few were left standing), but many were left in the stream. I remember Dave saying he got lots of complaints from anglers snagging their hooks on the woody debris. His response was that his job was to create good trout habitat, not to make it easy to fish.
Ben Cross recently completed a Master's degree at UWSP with Mike Bozek, looking at influences of riparian vegetation (trees in particular) on trout. His work was focused on the central hardwoods region and showed how shading from trees could help promote cooler stream temperatures. So, there is support for managing for riparian trees in some regions of the state.
Matthew G. Mitro, Ph.D.
Coldwater Fisheries Research Scientist
Wisconsin Department of Natural Resources, Science Services
Science Operations Center, 2801 Progress Road
Madison, Wisconsin 53716
608 221 6366 phone
608 221 6353 firstname.lastname@example.org