Eakin Park : Alluvial Forrest and Fresh Water Pond Community
Our second field trip led us to Eakin Park, located in east, central Fairfax County. Eakin Park is among several protected areas that collectively contribute to the Accotink Stream Valley Water Shed. There are two different ecological communities within the park, an alluvial forrest and a fresh waterpPond, which were the focus of Friday’s excursion.
An alluvial forest community is a type of wet land area that can be defined as a flat land area adjacent to a stream, composed of unconsolidated sedimentary deposits (alluvium), and subject to periodic inundation by a source of water, typically a stream. However, in the case with Eakin Park significant sized streams were not evident, but a small creek did exist. The entrance to the park appeared to be more open flood plain area with a random mix and dispersal of deciduous trees.
The trees in this area were Sweet Gums, Red Maple, and a few varieties of oaks especially as we arrived closer to the edge between the open area and the start of the forest. Some of the more notable trees along the edge were Black Gum, Mockernut Hickory and again some oaks. There were also several depressions filled with damp, dead and decaying leaf matter, and nothing else. Since no flora was present, these depressions may indicate an ephemeral body of water or vernal pool existed in the not too distant past.
Much of the water that flows into Eakin is derived locally from runoff, direct rain fall, and from the creek that traverses the park. Frequent inundations of water in this low lying area contribute to a soil content rich in clay. The clay rich sub soil at Eakin forms what is known as gleyed or hydric soils. This type of soil retains water easily. The water retaining properties of the hydric soil and the overflow and the transport of nutrient rich sediments from flooding in the region helps to perpetuate a diversity of deciduous hardwood and herbaceous plants. In one area of the park the soil retains water so well that a freshwater pond community has become established along with flora distinctly different than what we observed in the alluvial forest community.
The main feature of a fresh water pond community is obviously the fresh water pond.
There are several ways to describe a Freshwater Pond. Freshwater Ponds are ‘bodies of water where light penetrates to the bottom of the waterbody, or ‘bodies of water shallow enough for rooted water plants to grow throughout, or ‘bodies of water which lack wave action on the shoreline. Unlike the flora found within the alluvial forest community which dominates Eakin Park, the pond had its own distinct flora. These included mostly herbaceous plants of which broad leaf cat tails dominate. Other types of herbaceous plants were red clover, common plantain, path rush, deadford pinks, and cat briar.
Plant List Observed at Eakin Park
|Alluvial Forest Community|
|Open Field||sweet gum, *red maple,||None discussed||Non discussed|
|Edge||black gum, mokernut hickory, white oak, pin oak, box elder||horse nettle, red clover, water hemlock , pokeweed||cat briar, poison ivy, va creeper,honey suckle|
|Forest Area||sycamore, river birch, red maple, sweet gum||chickory, jap stiltweed,||cat briar, poison ivy, va creeper|
|Creek Riparian Zone||black willow, river birch||horse nettle, lesser clearweed, true nettle|
|Fresh Water Pond Community|
|Riparian zone||red clover, common plantain, deadford pink, chickory|
|Litoral zone||path rush, ** broadleaf cattail|
* Most dominant deciduous tree in alluvial forest community was Red Maple
** Most dominant plant in freshwater pond community
River birches are medium to large trees between 60-80 feet tall fully grown and are generally found in flood zone areas. They (especially the younger trees) can be distinguished by their reddish-gray, papery bark, and have triangular, short stalk, coarsely double toothed 3 inch leaves.
Two characteristics that appealed to me about this tree was its bark and how the tree responds to living in a wet environment by growing multiple trunks. My original thought when I saw trees like this was that they were diseased –especially looking at the bark. But I have since learned this is characteristics of the species, particularly with younger trees.
Future filed trips might entail looking at the transition zones between these two different communities. It would be interesting to see if there were an abrubt transition in flora unique only to the transition area or perhaps some sort of gradual zonation of floral species separating the two communities.