Victoria C. Guerrero, Ph.D. 2
The Anacostia Kenilworth Marsh, although a fragile ecosystem, provided a prototype study for marsh restoration efforts in the utilization of dredge materials from the Anacostia River estuary. In the Spring of 1993 approximately 150,000 cubic yards of dredge material from other areas of the Anacostia were placed in the marsh using booms and berms to create fill areas of higher elevation separated by tidal guts (Syphax and Hammerschlag, 1995).
The mass fills were planted with 350,000 plants of 18 species to re-establish marsh vegetation as part of the restoration effort. Mass Fill 1 (10 acres) was four inches higher than the other mass fills. Leersia oryzoides (cutgrass) was the dominant species, covering 59% of the area. Sagittaria latifolia (arrowhead), Bidens sp. (beggar's tick), and Cyperus sp. (red root) were the dominant species in MF2. MF2 (18.5 acres) remained wet throughout the extensive flats in July and August. Grasses and sedges were not as abundant. It appeared that the gradient and water levels and reduced competition from cutgrass were the determining factors for the abundance of the broadleaf arrowhead. The dominant species in MF2-A were Sagittaria sp. (broadleaf arrowhead), Leersia oryzoides (cutgrass), and Cyperus sp. (redroot). Although this area is a subsample of MF2 the results from the transect and quadrat survey showed an entirely different vegetation composition of the site. Mass fill site 3 (Fringe Marsh, 5 acres) was inaccessible and sparsely planted; MF2-A, located along the edge of MF2, was used in the study instead of MF3.
Phase I of this study was conducted in July and August 1993 and used transects, quadrats, and biomass determination of dry and ash weights to analyze the first year vegetation composition of two mass fill areas of the restored Kenilworth Marsh (Guerrero and Hille, 1994). This study was conducted at mass fill site 1 (MF1), site 2 (MF2), and site 2-A (MF2-A). Overall, the three mass fill study sites (MF1, MF2, and MF2-A) could be described as a "sea of grass." Leersia oryzoides (rice cutgrass) was the species that produced the maximum amount of biomass (oven-dried) as well as the highest amount of decomposed material. The widespread, horizontal and weed-like growth of cutgrass obliterated the growth and success of species such as Eleocharis sp (spikerush), Pontederia cordata (pickerelweed), Sagittaria latifolia (arrowhead), Alisma subcordatum (water plantain), Juncus sp.(rush), Scirpus sp. (bulrush), Echinocloa sp.(millet), Hibiscus moschuetos (mallow), and others.
Phase II of the study was conducted from August 1 to September 25, 1994 using transects, quadrats, and biomass determination (dry and ash weights) of harvested material at all the three sites MF1, MF2, and MF3 including a Control site. Leersia, Typha spp. Lythrum, and Sagittaria were the dominant species in MF1; Leersia, Typha, Sagittaria and Pontederia in MF2; Cyperus sp. in MF3; and Carex and Hibiscus in the Control. Lythrum and Typha appeared to outcompete and dominate Leersia. Results obtained in Phase II will be presented and discussed in this paper.
