In a novel look at managing both the future's timber harvest while
being mindful of the impact on key songbirds in Michigan's Upper
Peninsula, Michigan State University researchers use a new forest
simulation model for the first time to look at what timber-friendly
hardwood regeneration can mean to bird habitat. And it's a long-range
look, given that the time lag between forest management decisions and
impact are generations.
The results are reported online in the journal Forest Ecology and Management.
"Foresters are farmers -- but instead of sowing and harvesting in six
months, they need to think 50 years in the future," said James
Millington, the paper's lead author and former post-doctoral researcher
at Michigan State University's Center for Systems Integration and
Sustainability (CSIS). "If you are worried about the state of the forest
in 100 years time, you need to think about it now and you'll need good
models like we're developing."
Michigan's Upper Peninsula is home not only to a thriving timber
industry, but also is an important breeding ground to many songbird
species of conservation concern. Birds, Millington explained, are
particular about their neighborhoods -- having specific preferences for
how open the forest canopy is and how high and sturdy branches are. If a
forest changes considerably as it is harvested and regrows, birds won't
be as successful at nesting and reproducing.
Paper coauthors are Michael Walters, associate professor of forestry;
Megan Matonis, who recently earned a master's degree in forestry while a
CSIS member; Edward Laurent, a former CSIS doctoral student now science
coordinator at the American Bird Conservancy; Kimberly Hall, climate
change scientist at The Nature Conservancy; and Jianguo "Jack" Liu,
Rachel Carson Chair in Sustainability and director of the center.
The group engaged in a complicated birds-eye view of the forest,
seeking to understand how four key songbirds -- the black-throated green
warbler, eastern wood-pewee, least flycatcher and rose-breasted
grosbeak -- dealt with neighborhood upheaval. The study area stretches
over some 3,000 square miles of public and private land from Crystal
Falls to the west, east and south to Escanaba and north of Marquette.
For two years, the team examined the harvest gaps left in forests when
hardwoods are cut down.
Logging changes a forest's composition -- creating gaps in the canopy
that can take years to fill. Matonis, Millington's colleague, recently
reported that the current popular way of encouraging regeneration of
hardwoods, called gap harvesting, isn't always successful. Sometimes it
appears deer are chowing on the maple seedling trying to grow in the
sunny gaps left by harvest.
The four songbird species the team picked all are fussy about their
canopy. For example, the warbler likes its canopy dense with lots of
branches about 50 feet high. The flycatcher, however, digs more open
expanses.
"If all the birds like the same thing -- understanding consequences
of logging and differences in tree regeneration would be easier,"
Millington said.
The analysis is ambitious and complicated. The team seeks to create
models that show how a forest shapes up at different rates of
regeneration, both in timber-centric and bird-centric points of view.
The bottom line: Regeneration in harvest gaps of species that become
large canopy dominant trees such as sugar maple is crucial for forest
managers to have choices. If trees aren't growing back well, there's no
opportunity to even start watching out for the forest's residents.
"Essentially for birds in these forests it's the density of sugar
maple regeneration that has the biggest effect on their future habitat,"
Millington said. "These birds are picky about their overstory -- and if
regeneration is changing the forest now, in 100 years times your canopy
is going to be very different.
"We know how to grow trees pretty well and we can get timber, but
people who manage timber need to talk to people who manage for wildlife,
and they all need information to make decisions."
The research is funded by the U.S. Department of Agriculture, the
Michigan Department of Natural Resources and MSU's AgBioResearch.
Millington is now a Leverhulme Early Career Fellow at King's College in
London, UK.