Walnut Creek

Dave Knorr and I were investigating a site for suitability as an area for compensatory wetland creation.  Important for consideration are non-forested locations that have positive hydrology indicators.

Arriving to the site in Howard County, Maryland, our first impression was the vastness of sod-forming tall fescue, Schedonorus arundinaceus (FACU), being a near monoculture in the landscape.  Tall fescue is allelopathic and inhibits the growth of woody plants and can persist as a clumpy old-field dominant for upwards of 20 years.  It’s not all that palatable for most herbivores, and its chemical properties act as an abortifacient in rabbits.  Livestock, deer and horses only graze on fescue after its gone into winter dormancy.

I’ve written an article on the problems with using tall fescue in ecological restoration, which is attached as a PDF for downloading.

As we walked downslope and closer to the Walnut Creek floodplain, we began to observe species patchiness, where other aggregates were being expressed, and based on soil saturation.  Reed canarygrass, Phalaris arundinacea (FACW), in the center of this photo,  is a native that likes moist soils and is an indicator species of possible wetlands, or at least seasonal soil saturation.

We were seeing ecotone zonation, where aggregate patches were showing areas of either hydric, wetland soil, or vegetation stress in the fields, where seasonal high groundwater, flips the species from upland tall fescue, to hydrophytic species more tolerant of wetland conditions.  This photo shows a depression within the field with a near monoculture of spikerush, Eleocharis sp. (OBL), mixed with a few water plantain, Alisma subcordatum (OBL).

Hidden within the fescue were patches of Longleaf Starwort, Stellaria longifolia (FACW), a wetland native.

Close-up, the Starwort created thick mats, in some of the wettest of the field depressions.

Another equally “obligated” native, was the Bog Yellow Cress, Roippa palustris (OBL).

This mustard plant is also a Maryland native.

Working our way down to the perennial stream, we noted some nice pools, loaded with endemic fisheries, with what looked like fallfish, other minnow species and most likely chubs, shiners and dace.  Heron were nearby, as well as king birds feeding over the stream for insects.  These swallowtails were licking minerals and salts from the in-channel, wet sand bars.

If I had my DJI Mavic drone with me, I could have photographed the meadows from above, and better discerned the aggregate patchwork that helped to ground-truth the wettest areas of the fields, which were more or less confined enough to one particular area, where we might be able to pull off a few non-forested acres with seasonal high groundwater.

The next course of action would be to consider a series of wells, where we would install automated HOBO readers, to monitor seasonal groundwater elevations, and determine how much shallow excavation, would get us to near saturated soils at the surface, to support viable wetlands through ecological time.