Friday, February 03, 2012

In dry chert woods

Wednesday's bluebird skies were the perfect setting for going out to the woods, to the nice burned and slicked off woods where I do most of my sampling. These post oak-white oak-black oak woods have burned regularly for the past 5,000 years, actually, and while the grazing impacts can be seen in certain areas, walking through these woods doesn't involve climbing over barbed wire fences like it does in much of the Ozarks.

All the shrubs here have been topkilled by November's fire, so I couldn't really conduct any winter twig browse work. My winter bird surveys are complete for the area, with red-headed woodpeckers stealing the show this year with record numbers counted. Instead, we went on a mission that day to compare our field-tested natural community map to one made from the comfort of a computer modeling program 100 miles away.

Paint the screen in dry chert woodlands and make inclusions where the dry mesic comes into view, mostly in those steep dissections on north facing slopes, maybe in a creek bottom where the grazing impacts can be seen. Throw out the soils layer since it doesn't help at all in distinguishing dry from dry mesic woodlands in this country. When mapping natural communities in the Ozarks, think like a fire--these landscapes are shaped and maintained by fire. In a white oak-sugar maple setting with sedges and fewer prairie-loving forbs, you may be in dry mesic. But in a gama grass stand with stunted black oaks and post oaks, these areas where foresters would claim "you can't take a log," you're likely in dry.

Careers are made around modeling programs in the field of natural history. I've seen multimillion dollar end projects of models of where, for example, glades are located in the Ozarks--visit some of these areas and you'll find open woodlands and no trace of glade vegetation. Landscape models have been published without any ground truthing behind them. In the country I was in this week, if you spend an afternoon hiking through the woods, you'll have a pretty good idea of what most of the area looks like: dry chert woods with glades, small inclusions of dry mesic woods. The soils in ArcView won't tell you that, but walk a little way and you can see it too.

Natural communities are not based on soils and geology alone, and shouldn't be mapped simply using the soils and geology information. Natural communities are more complex, they are distinct assemblages of plants, animals and microorganisms that "occur in repeateable patterns across the landscape and through time. These assemblages of biota occupy definable physical environments, which in turn influence the structure and composition of natural communities." The father of natural communities in Missouri studied under Illinois' Jack White who concepted the idea roughly 40 years ago. These maps, the ones that show a distinct natural community for every soil series, are inaccurate. Just going to the woods one afternoon and studying the canopy composition, ground flora, site condition, slope, aspect, topography, and fire behavior in a given area will tell you much more than you'll ever learn sitting at a desk with a $7,000 computer program.

1 comment: