Recent Studies in Dyke Marsh Preserve

In this section we discuss several studies that have taken place in Dyke Marsh since the early 1990s. This section will help us to understand the current knowledge that exists on Dyke Marsh, which can help us determine what still needs to be known. Some of the studies may also help provide insight into our primary concerns and fundamental questions for restoration in the discussion section.

Soils 17-19

Elevation 19-21

Bathymetry 22-23

Hydrology 22

Water Quality 24

Tidal Gauge 24-25

Vegetation 25-28

1991 25-26

2003 25-28

2004 26-28

Relationship of Vegetation & Elevation 28-29

Seed Germination 29-35

Seed Trawls 29

Seed Bank 30-35

Invertebrates 35-36

Fish 36

Breeding Bird Surveys 36-37

Marsh Wren 37

Literature Cited 38

16 RECENT FIELD STUDIES IN DYKE MARSH Soils size using the Hydrometer Method (Gee In August of 2003, an orthophoto of and Bauder 1986). Most samples had DMP was used to select five transects higher than 70% organic matter, and all that traversed a diversity of vegetation samples had higher than 60%. Samples communities and topographic positions were composed largely of silt and clay, within the marsh. Soil core samples with little, if any, sand. Soil types were collected at the start, middle and include silty clay, silty clay loam, clay, end of each transect in March 2004 silt loam, and clay loam, with the (Figure 10). A total of 15 samples, each majority of samples being silty clay and 10-cm long, were analyzed for particle silty clay loam (Table 1 and Figure 11).

Figure 10. Orthophoto of DMP with 5 transects used for soil cores and vegetation sampling.

17 Table 1. Particle-size analysis data of soil samples from DMP in March 2004. Organic Sample ID Location description Sand (%) Clay (%) Silt (%) matter (%) Soil Type near forest edge, dominated by TR1 B Impatiens and 0 46 54 89 silty clay middle of marsh/ edge of Typha, dominated by Peltandra, Nuphar and TR1 M Typha 0 44 56 70 silty clay near river, dominated by Acorus and TR1 E Peltandra 12 38 50 72 silty clay loam TR2 B near river, dominated by Impatiens 20 45 35 84 clay middle of marsh, dominated by TR2 M Peltandra and Nuphar 6 39 55 74 silty clay loam near forest edge, dominated by TR2 E Nuphar 0 36 64 81 silty clay loam TR3 B near river, dominated by Impatiens 0 56 44 86 silty clay middle of marsh, dominated by Typha, Impatiens, Peltandra and TR3 M Nuphar 0 49 51 76 silty clay near forest edge, dominated by Typha TR3 E and Acorus 0 45 55 78 silty clay middle of marsh, dominated by TR4 B Phragmites and Peltandra 4 41 55 73 silty clay middle of marsh, dominated by TR4 M Impatiens and Typha 7 44 50 70 silty clay near wood buffer of Haul road, dominated by S. fluviatilis, Typha, TR4 E and Impatiens 0 71 29 79 clay near forest edge, dominated by TR5 B Impatiens 25 34 41 76 clay loam middle of marsh, dominated by TR5 M Peltandra, Bidens, and Sagittaria 17 28 55 62 silt loam middle of marsh, dominated by TR5 E Impatiens and S. fluviatilis 8 27 64 84 silt loam

18 100

90

80

70

60 Sand (%) Clay (%) 50

cent (%) Silt (%) r e

P Organic matter (%) 40

30

20

10

0 TR1 B TR1 M TR1 E TR2 B TR2 M TR2 E TR3 B TR3 M TR3 E TR4 B TR4 M TR4 E TR5 B TR5 M TR5 E Sample ID

Figure 11. Distribution of percent sand, clay, silt, and organic matter for each soil sample.

Elevation were established, and from these Harper and Heliotis (1992) surveyed stations, 132 spot elevations were taken elevations of Dyke Marsh that they during low tide periods. incorporated into a hydrologic model of Elevation throughout the marsh was the marsh (see below). They surveyed found to be relatively flat with the spot elevations, using a Topcon exception of the tidal guts. Relatively Geodetic Total Station GTS-2 to flat areas of the main marsh occupy 93 establish horizontal and vertical control acres between elevations of 1.0 foot points in DMP. Four control stations (0.3 m) to 2.6 feet (0.8 m) (Figure 12).

4

3

2

1 Feet 0

-1

-2 0 20406080100120140 Acres Figure 12. Cumulative distribution of elevation at DMP (Harper and Heliotis 1992).

19

The Harper and Heliotis (1992) ft. included the spring tidal range of 0.0 hydrologic study also examined the to 3.0 ft. and extended from 2% to 99% elevations of 22 species along a of inundation time (Figure 13). These permanent transect throughout the results show that a variety of species marsh proper and along Hog Island Gut can coexist along an elevation gradient (Table 2). They found that the overall ranging from low marsh to high marsh. intertidal vegetation range of –0.5 to 3.3

Table 2. Elevation survey of DMP vegetation. Elevation range (ft) Elevation range (ft) Species (Harper and Heliotis 1992) (UMCES-AL unpublished) Acorus calamus 1.6 - 2.6 0.1 - 2.1 Amaranthus cannabinus 1.7 - 2.5 0.1 - 1.2 americana -- 0.9 - 2.0 Bidens sp. 1.4 - 2.7 0.6 - 1.6 cylindrica -- 1.1 - 1.6 Calystegia sepium 2.3 - 2.7 0.8 - 2.0 Cephalanthus occidentalis 2.0 -- grovonii -- 0.9 - 2.0 Fraxinus sp. -0.2 - 2.4 -- Hibiscus moscheutos -- 1.3 - 1.4 Hydrilla verticillata -- -1.1 - 0 1.7 - 2.8 0.5 - 2.1 Leersia oryzoides 1.7 - 2.7 0.9 - 1.7 Najas minor -- -0.4 - -0.1 Nuphar lutea -0.5 - 2.7 -1.1 - 1.6 Onoclea sensibilis -- 1.5 0.3 - 2.8 -0.3 - 1.8 Phragmites australis 1.2 - 2.1 -- Pilea pumilia -- 0.9 - 2.0 Polygonum arifolium 1.5 - 2.7 0.9 - 2.1 Polygonum persicaria -- 0.1 - 1.6 Polygonum punctatum 1.4 - 2.1 0.6 - 1.0 Polygonum sagittatum -- 1.1 - 1.6 Pontederia cordata 1.2 - 1.7 0.1 Sagittaria latifolia 2.0 - 2.7 0.1 - 1.6 Scirpus fluviatilus 2.1 - 2.7 0.1 - 2.0 Sicyos angulatis -- 1.9 Sparganium americanum 2.7 -- Thalictrum polygamum 2.1 -- Typha sp. 1.2 - 2.8 0.1 - 2.1 Vitas sp. -- 1.2 - 1.6 Zizania aquatica 0.6 - 3.3 0.1 - 0.9

20 120

100

80 on i 60 dat

nun 40 % I

20

0

-2 -1 0 1 2 3 4 5 E lev atio n (ft) Figure 13. Percent time of inundation for DMP elevations (Harper and Heliotis 1992).

The UMCES Appalachian Lab surveyed the emergent marsh in July 2004. Topcon GPS equipment was used to obtain 129 spot elevations. Vegetation data consisting of percent cover of each species in a 1-m2 plot was also obtained at each of the 129 points (Table 2). A total of 27 species were observed throughout the marsh. The majority of these species were found in a broad range of elevations. Points surveyed ranged from -0.33 to 0.64 m in elevation. The majority of the points sampled throughout the marsh were between 0.25 and 0.49 m (Figure 14). Percent inundation time may be derived using the elevation data that Harper and Heliotis (1992) modeled (Figure 13). Researchers at UMCES Appalachian Lab will continue to work with modeling the 2004 elevation data in the near future. Specifically, they will model the effects of inundation frequency on community structure and incorporate scenarios of sea level Figure 14. Elevation ranges from point rise and freshwater pulses from the elevation survey, July 2004. watershed.

21 Bathymetry of DMP. Consultation with the USACE Much of the emergent marsh at can help to determine the approximate DMP lies on a plateau 3-4 ft. above amount of fill needed for a complete mean low tide and is not inundated by restoration of dredged areas, and the the typical 3 ft. tidal cycle. This shelf of timing, location and volume of future shallow water formerly extended dredging operations that outward to the dredged shipping lane in match the fill needs of potential the middle of the Potomac River (NPS restoration projects at DMP. 1977). Two bathymetric surveys of DMP from 1974 and 1992 show the Hydrology underwater topographic pattern left by Harper and Heliotis (1992) designed sand and gravel dredging to be highly a hydrologic simulation model for Dyke variable with several deep holes (up to Marsh to enhance ecosystem 30 ft. below mean low tide) present monitoring and provide information for (Figure 15). Once past the dredged future restoration projects. They found area, the bottom contour apparently that the overall flushing rate per tidal recovers to a more shallow depth before cycle for the main marsh, based on reaching the 25-40 ft deep shipping values of mean low and high tide channel maintained by the U.S. Army volume was 0.92 m3/s. The highest Corps of Engineers (USACE). velocity was found along Hog Island Gut The 1992 bathymetric survey is now in the mid channel (21-35 cm/s), 12 years old and likely not entirely although tidal velocity was not observed accurate owing to natural causes such to be disruptive to inter-tidal vegetation. as sediment scouring and deposition Mean tide ranged between 0.2 and 2.8 over the years and also due to extensive feet, with an average of 1.5 feet. Dye post-processing, smoothing of lines and tests confirmed high flushing rate per over-generalization of actual curvature. tidal cycle in the marsh. The main A new bathymetric study completed marsh is primarily watered from the before restoration would be extremely south by Hog Island Gut, and beneficial. For example, the USACE secondarily from the north by an inlet (Palermo and Zeigler 1976) used DMP south of Haul Road (Figure 9). The bottom topography, proposed retaining narrow beach around the northeast dike alignment, the bulking factor corner of the main marsh, at an (volume expansion on movement and elevation of 2.8 feet, blocked Potomac resettlement) of potential dredge fill, and River waters except when tides dredge fill settlement rates to estimate exceeded mean highs (Harper and the amount of dredge material needed Heliotis 1992). to restore a 28-acre demonstration area

22 Figure 15. 1992 (white numbers and blue interpolated area) and 1974 (red numbers) bathymetric studies of DMP and the Potomac River. Note the dark blue areas around the perimeter of the marsh estimate where deep holes, predominantly caused by dredging, occur.

23 Water quality Tidal gauge Water samples were taken from six Although various tidal gauge different locations around DMP, stations exist along the Potomac River, including from the Potomac River and no tidal gauge existed within DMP. A tidal guts in summer 2004 (Figure 16). gauge was installed in May 2004 at the The water samples were analyzed for Belle Haven Marina. The gauge ammonia, nitrate+nitrite, nitrite, ortho- consists of a submersible full-scale phosphate, total suspended solids and pressure transducer with an accuracy of total fecal coliform (Table 3). 0.1%, and datalogger, which are powered by a solar panel and a 12 V battery. The gauge hangs 1 m above the river bottom, which is at an elevation of –2.52 m. The pressure transducer measures the surface water level. Changes in water level correspond to pressure changes on a strain gage bonded to a pressure-sensitive diaphragm. When a precision excitation voltage is applied, the electrical resistance varies with changing liquid pressure. Using the datalogger, surface water level measurements are taken every 5 minutes and averaged every 15 minutes. This data will allow us to examine and graph the changing water levels in DMP through time (Figure 17).

Figure 16. Six water samples were taken throughout DMP and analyzed.

Table 3. Water quality data from six samples throughout Dyke Marsh Preserve (2004). 1 2 3 4 5 6 Ammonia (mg/L) 0.0370 0.1162 0.0601 0.0545 0.0141 0.0384 Nitrite+nitrate 0.8212 0.4325 0.8026 0.7544 0.4014 0.7755 (mg/L) Nitrite (mg/L) 0.0357 0.0227 0.0288 0.0289 0.0183 0.0324 Ortho-phosphate 0.0327 0.0335 0.0270 0.0278 0.0197 0.0199 (mg/L) Total suspended 22.0 15.8 11.2 14.8 2.0 2.4 solids (mg/L) Fecal coliform 66.6 n/a n/a 0 0 0 (colonies/100 mL) Non-fecal coliforms 199.8 n/a n/a 233.1 1165.5 932.4 (colonies/100 mL)

24

Figure 17. Water level of Potomac River at Belle Haven marina 06/06/04-06/19/04 (2 wks). Elevation of the river bottom below the tidal gauge was surveyed as –2.52m.

Vegetation vegetative areas within Dyke Marsh 1991 (Table 4). Transects were run through Dr. Z. Xu, from George Mason the flood plain forests, swamp forests, University conducted an inventory of and marshes. plant species and communities in Dyke Marsh in 1991, sponsored by the 2003 National Park Service, George The UMCES Appalachian Lab (AL) Washington Memorial Parkway. The sampled the vegetative composition of purpose of the inventory was to DMP marsh areas in August 2003. document all existent plant species and Vegetative composition data will help plant communities in the Dyke Marsh determine what community types are area, and to try to reveal the status of the most abundant and how they are the biodiversity of the . related to tidal inundation, frequency, The inventory of plant species and duration. Using the same 5 resulted in a collection of 1,120 plant transects from the aforementioned soil specimens including 373 species from study, sampling stations were 93 different families of (see established at 25-m intervals along each Appendix A). Of these 373 species, 60 transect. Three 1-m2 subplots were are obligate wetland species. The sampled at each sampling station that investigators estimate that they were 10 m apart. With a total of 45 inventoried approximately 90% of all sampling stations, 135 subplots were specimens in the marsh. sampled within the marsh. The inventory of plant communities shows the distribution of different

25 Table 4. The distribution of plant communities in Dyke Marsh (Xu 1991).

Vegetation Types Area (acres) Area (% of total)

Flood plain forest 89 36 Secondary vegetation 13 5 Swamp forest 47 19 Nuphar-Peltandra 22 9 Typha (mixed) 49 19.5 Mixed-non-Typha 28 11 Wild Rice (mixed) 0.8 0.3 Phragmites (pure) 0.5 0.2 Totals 249.3 100

2004 virginica, Typha sp., and Impatiens Vegetative composition of DMP was capensis. Other recurring species also observed by UMCES-AL in July of observed include Nuphar lutea, Acorus 2004. The initial 5 transects from 2003 calamus, Scirpus fluviatilis, Polygonum were used along with 6 additional arifolium, and Leersia oryzoides (Table transects. Plots (but no subplots) were 6). established at 25-m intervals along each Cluster analyses of the percent cover transect totaling 92 plots. An additional observations were also performed on 38 plots were sampled throughout the the 2003 data. The analysis derived the marsh, resulting in a total of 129 plots. following six cover types: 1) P. virginica with N. lutea, 2) N. lutea, 3) Impatiens 2003&2004 capensis with Typha sp., and P. Geographic coordinates for each virginica, 4) Typha sp., 5) P. virginica, 6) subplot and plot were recorded using a I. capensis (Table 7). global positioning system. Cover was evaluated by species within each Table 5. Cover categories used for visual subplot, and voucher specimens taken percent cover estimation per species. for species not identified with certainty in Cover categories: the field. Percent cover was visually trace = 1 estimated using exact percentages, as 0-1% = 2 well as categories for each subplot 1-2% = 3 2-5% = 4 (Table 5). A total of 30 5-10% = 5 species were found in the vegetation 10-25% = 6 plots in 2003 and 31 species in 2004. 25-50% = 7 No species previously unknown to DMP 50-75% = 8 were found. All species averaged less 75-95% = 9 than 60% of cover per plot, both years. Prevalent species, found in over 50% of the plots sampled, include Peltandra

26 Table 6. Species frequency and percent cover in sampled plots. (* = non-native species, black numbers represent data from 2003, blue numbers represent data from 2004) % of all Average % # plots plots cover Relative % Species observed in observed in estimate cover estimate Typha sp. 105 101 78 78 33 22 19 13 Impatiens capensis 83 98 61 76 32 59 16 32 Peltranda virginica 116 90 86 70 34 24 23 0.2 Nuphar lutea 65 46 48 36 40 49 15 12 Cuscuta gronovii 2 45 1 35 1 17 0.1 4 Schoenoplectus fluviatilis 26 41 19 32 29 22 4 5 Acorus calamus 40 39 30 30 17 14 4 3 Polygonum arifolium 24 39 18 30 12 17 2 4 Open 19 29 14 22 18 28 2 4 Leerzia oryzoides 22 23 16 18 14 14 2 2 Sagittaria latifolia 11 14 8 11 19 16 1 1 Bidens laevis 17 13 13 10 13 10 1 0.7 Calystegia sepium* 11 12 8 9 13 16 0.8 1 Dead matter 67 9 50 7 19 20 8 1 Polygonum persicaria* 2 9 1 7 2 10 0.1 0.5 Amaranthus cannabinus 0 8 0 6 0 6 0.0 0.2 Zizania aquatica 7 6 5 5 14 19 0.6 0.6 Pilea pumila 2 5 1 4 14 10 0.2 0.3 1 5 1 4 25 24 0.1 0.6 Hydrilla verticillata* 3 4 2 3 10 8 0.2 0.2 Vitis spp. 0 4 0 3 0 31 0.0 0.7 Polygonum punctatum 2 3 1 2 18 10 0.2 0.1 Boehmeria cylindrica 0 3 0 2 0 8 0.0 0.1 Hibiscus moscheutos 2 2 1 2 23 49 0.3 0.5 Najas minor* 1 2 1 2 10 8 0.1 0.1 Polygonum sagittatum 0 2 0 2 0 0.5 0.0 0.1 Unknown 2 1 1 1 1 0.1 0.1 0.1 Onoclea sensibilis 0 1 0 1 0 60 0.1 0.3 Pontederia cordata 0 1 0 1 0 63 0.0 0.3 Sicyos angulatis 0 1 0 1 0 15 0.0 0.1 Phragmites australis* 3 0 2 0 17 0 0.3 0.0 Cornus amomum 2 0 1 0 32 0 0.4 0.0 Schoenoplectus tabernaemontani 2 0 1 0 25 0 0.3 0.0 Solanum dulcamara* 2 0 1 0 24 0 0.3 0.0 1 0 1 0 15 0 0.1 0.0 Sparganium eurycarpum 1 0 1 0 2 0 0.1 0.0 Ranunculus sceleratus 1 0 1 0 5 0 0.1 0.0 Ceratophyllum demersum 1 0 1 0 1 0 0.1 0.0

27 Table 7. Mean values for each species in each cluster. (dominant species for each cluster in bold) Typha Acorus Impatiens Peltandra Nuphar Schoenoplectus spp. calamus capensis virginica lutea fluviatilis Cluster 1 5.6 3.3 1.2 28.4 18.3 3.9 Cluster 2 5.2 0.6 1.1 7.6 81.1 0.0 Cluster 3 27.3 3.9 32.5 22.4 1.4 17.6 Cluster 4 60.0 0.1 14.0 28.1 20.7 0.0 Cluster 5 14.8 15.4 6.2 59.1 9.9 1.3 Cluster 6 19.1 7.4 85.7 15.7 5.0 9.4

Relationship of Vegetation & Elevation The data from the 2004 elevation survey (pg. 21) was analyzed with the 2004 standing vegetation data (pgs. 26- 28) using simple regression (Table 8). It was found that the dominant species in the marsh, annual and perennial, can occur on the majority of the marsh elevation gradient, but it is at the extremes of the elevation gradient that some species drop out. For example, Impatiens capensis does not occur at elevations lower than 0.15 m, and Nuphar lutea does not occur at elevations higher than 0.49 m for the points sampled. Non-metric multidimensional scaling was run to explore relationships between elevation and species distribution. Three axes explained 87% of the variation in species distribution, with axis 2 explaining 50% (Figure 18), suggesting that elevation is a good predictor of species distribution, with other factors related to dispersal of species, such as distance to the swamp forest or distance to tidal guts, probably explaining the rest.

Figure 18. Results of non-metric multidimensional scaling that relates the 2004 vegetation community matrix to marsh elevation. Axis 2 explains 50% of the variation in species distribution and is directly related to elevation.

28 Table 8. Significance of relationship that was towed by a boat, three trawls between dominant marsh species and were made along each transect to elevation and percent inundation. Red numbers signify α=0.01, and blue numbers sample the floating seed rain (Figure signify α=0.05. 19). ELEVATION Dominant species R2 p (y-int.) p (slope) Impatiens 0.0879 0.2381 0.0035 Typha 0.0049 0.0139 0.4903 Peltandra 0.1536 <0.0001 0.0002 Nuphar 0.1420 <0.0001 0.0098 INUNDATION Dominant species R2 p (y-int.) p (slope) Impatiens 0.0879 <0.0001 0.0035 Typha 0.0049 0.0116 0.4903 Peltandra 0.1610 0.1220 0.0001 Nuphar 0.1400 0.9149 0.0104

Figure 19. Seed trawl collection technique. Seed Germination Courtesy of Andy Baldwin, University of Seed Trawls Maryland. Seed trawls were conducted around DMP to study the quantity of seeds and All 15 samples from the 2003 trawl species of seeds floating into the marsh were cold stratified over the winter and due to tides, river currents, and storms. then germinated along with the 15 The information from these seed trawl March 2004 samples in the greenhouse. germinations may reflect seasonal An additional summer sampling took changes, and tell us more about the place in August 2004. regional and local seed supply that may A total of 7 species have germinated contribute to the revegetation of DMP by from all seed trawls thus far. Five both native and exotic species. species germinated from both years, In October 2003 and March 2004, with the dominants being Impatiens five 200-m transects were established capensis (63%) in 2003, and Pilea around the perimeter of the emergent pumila (83%) in 2004 (Table 9). marsh. Using a modified plankton net

Table 9. Number of germinated seedlings and abundance of each species for fall 2003 and spring 2004 seed trawls.

Impatiens Bidens Leersia Peltandra Ranunculus Amaranthus Pilea capensis laevis oryzoides virginica sceleratus cannabinus pumila TOTALS

20 3 7 1 1 2003 (63%) (9%) (22%) (3%) (3%) 0 0 32

3 1 1 1 30 2004 (8%) (3%) 0 0 (3%) (3%) (83%) 36

29 Seed Bank Seedlings emerging from each Seed bank work had not previously sample were identified as young as been carried out at DMP. The data from possible, and removed from the tray the seed bank germination study can when identified. Seedlings of unknown help us understand the number of species were transplanted and allowed species and quantities of individual to mature before identification. When seeds that comprise DMP’s seed bank. seedling emergence ceased in late fall Collectively with the seed trawl data and 2003, all trays were placed in cold the vegetation cover data, these studies storage for the winter to cold stratify any will help determine what planting remaining seeds; trays were then measures (if any) are needed to subjected to wet conditions in the spring reestablish diverse native plant of 2004 to continue germination. communities and to control the spread Germinated seedlings represent of non-native species into restored approximately 50 species (some areas. species have not been identified yet). Seed bank samples were collected The data indicates that the 2003 seed in August 2003 and March 2004 using bank was dominated by Typha sp., the aforementioned transects and plots. representing 88% of 2,239 seedlings, Within each subplot, three 3.8-cm and that the 2004 seed bank was diameter by 5-cm long sediment dominated by Typha sp. representing samples were collected using a PVC 60% and Impatiens capensis coring tube. The sediment from each representing 21% of 1,579 seedlings subplot was mixed, divided into two (Tables 10 & 11). Annuals made up a samples, and spread over vermiculite in significant portion of the species present bedding trays in a greenhouse for in the seed banks of both years. 2003 germination. The duplicate samples had 12 annual species out of 25 species were treated to two water conditions, total, and 2004 had 11 annual species saturated and inundated, to mimic the out of 32 total species. range of conditions for germination in Two things are important to consider the field (Figure 20). when examining this data. One, I. capensis needs to be cold stratified before germinating. Although, the fall 2003 seed bank samples were left over winter for cold stratification, no I. capensis seedlings emerged. This could mean either that the seeds did not successfully germinate or, more likely, that there were no I. capensis seeds in the samples. Because the seeds were collected in August, it is probable that few or no seeds were in the seed bank at that time, as I. capensis tends to disperse seeds in September and October. Figure 20. Seed bank germination set-up in greenhouse.

30 Table 10. 2003 seed bank germination data. spatially and temporally variable. A (* = non-native species) relationship between the standing % of total Number of seedlings vegetation and the seed bank was Species seedlings emerged expected because most seeds fall close Typha sp. 1989 88.83 to the parent plant. Thus, other factors Amaranthus cannabinus 58 2.59 besides seed dispersal must be Hydrilla verticillata* 38 1.70 contributing to the distribution of seeds Cuscuta gronovii 35 1.56 at Dyke Marsh, such as tidal flushing. Polygonum persicaria* 20 0.89 Leersia oryzoides 15 0.67 Table 11. 2004 Seed bank germination data. (* = non-native species) Ludwigia palustris 14 0.63 Bidens laevis 14 0.63 % of total No. seedlings Najas minor* 8 0.36 Species seedlings emerged Pilea pumila 7 0.31 Typha sp. 1042 60.23 Polygonum arifolium 5 0.22 Impatiens capensis 324 18.73 Carex sp. 3 0.13 Cuscuta gronovii 67 3.87 Rorippa palustris 3 0.13 Amaranthus cannabinus 44 2.54 Bidens cernua 3 0.13 Zizania aquatica 13 0.75 Juncus effusus 3 0.13 Ludwigia palustris 53 3.06 1 Dead 3 0.13 Leersia oryzoides 30 1.73 Echinochloa muricata 2 0.09 Najas minor* 41 2.37 Vallisneria americana 2 0.09 Polygonum arifolium 20 1.16 Solanum dulcamara* 2 0.09 Pilea pumila 22 1.27 Sagittaria latifolia 1 0.04 Bidens laevis 12 0.69 Boehmeria cylindrica 1 0.04 Mikania scandens 90.52 Cyperus sp. 1 0.04 Peltandra virginica 50.29 Mikania scandens 1 0.04 Ranunculus sceleratus 20.12 1 3 seedlings died before being identified. Rorippa palustris 20.12

Calystegia sepium* 10.06 The second item to consider when Trifolium repens* 10.06 interpreting this data is that this raw data Schoenoplectus tabernaemontani 50.29 may not represent the composition of Polygonum punctatum 50.29 vegetation growing in the marsh. For Schoenoplectus fluviatilis 20.12 example, Typha spp. produced far more Hibiscus moscheutos 10.06 seedlings in the greenhouse Lobelia cardinalis 10.06 germination experiment, yet is not as Juncus effusus 30.17 dominant in the field as this ratio Polygonum persicaria* 20.12 suggests (see vegetation 2003 and 2004 section). Dominant species in the 2003-2004 The relationship between the seed seed bank include Typha sp., Impatiens bank and the standing vegetation is capensis, and Amaranthus cannabinus, interesting and should be explored while dominant species of vegetation further. Using Mantel tests to compare cover also include Typha sp. and I. community matrices, no relationships capensis, along with Peltandra virginica were found between 2003 vegetation and Nuphar lutea. We evaluated the data and 2003 or 2004 seed bank data, similarity in species composition which suggests that the vegetation is

31 between the seed bank and vegetation dominant species; they are Typha sp. of the marsh using the Sørenson’s and Peltandra virginica (Table 13). quotient of similarity (qs) (Sørenson 1948). The qs index ranges from 0 (the Table 12. Quotient of similarity values for samples have no species in common) to DMP and other local marshes (Baldwin and 1 (the samples contain exactly the same DeRico 1999). species). It was found that the species Seed bank qs DMP 2003 vs. reference marsh 0.52 composition of the seed bank and DMP 2004 vs. reference marsh 0.53 vegetation are fairly similar. The DMP 2003 vs. restored marsh 0.47 relationship has a qs value of 0.48 for DMP 2004 vs. restored marsh 0.55 2003, and 0.60 for 2004. The 2003 Vegetation qs seed bank and vegetation share 17 out DMP 2003 vs. reference marsh 0.50 of a total of 40 species, and the 2004 DMP 2004 vs. reference marsh 0.51 data share 15 out of 48 different DMP 2003 vs. restored marsh 0.41 species. The most significant result is DMP 2004 vs. restored marsh 0.45 that the seed bank and vegetation share two of the most dominant species When comparing the seed bank (Typha sp. and I. capensis) (Tables 6, data of DMP (2003 & 2004) with 10, 11). Baldwin and DeRico’s (1999) (reference Baldwin and DeRico (1999) studied and restored) some similarities are the seed banks and vegetation of found. However, even though the two Kenilworth marsh (after it had been studies have reasonable qs values, they restored) and a nearby reference marsh share only one common dominant using similar methods and procedures species, Typha sp. (Table 14). as UMCES-AL. When comparing the It is important to examine the seed bank and vegetation of DMP to presence and significance of annual Baldwin and DeRico’s (1999) reference species in a marsh area and its seed marsh and restored marsh (Kenilworth), bank before it is restored. The number we find that DMP is fairly similar to both of annual species present in all of the the restored and reference marshes in cover studies is remarkably similar, yet respect to both the seed banks and the relative percent cover of annuals in vegetation. It does seem that DMP is a the marsh vegetation varies (Table 15). little more similar to the reference marsh When comparing annuals in the seed in respect to the seed bank and banks of these studies, we found especially the vegetation (Table 12). striking similarities in total number of DMP 2003 and 2004 vegetation species and the percent that the data and Baldwin and DeRico’s (1999) annuals represent of the total seed bank Kenilworth (restored) and reference study (Table 15). marsh data share 2 of the 5 most

32 Table 13. Percent cover of each species relative to total cover of all species. We compare the vegetation at Dyke Marsh Preserve (DMP) for 2003 & 2004, these values are also compared to the Baldwin and DeRico (1999) study that documents vegetation cover in a reference and restoration site nearby DMP. Bolded numbers signify “dominant” species, and * represents non-native species. DMP Baldwin and DeRico (1999) Species 2003 2004 Reference Restored Acorus calamus 3.87 3.13 1.26 -- Amaranthus cannabinus -- 0.24 1.43 0.15 Apios americana 0.15 0.65 1.60 -- Bidens frondosa ------0.03 Bidens laevis 1.24 0.72 -- 0.40 Bidens tripartita ------1.06 Boehmeria cylindrica -- 0.11 -- Bolboschoenus fluviatilis ------5.38 Calystegia sepium* 0.81 1.04 -- -- Ceratophyllum demersum 0.01 ------Cornus amomum 0.37 ------Cuscuta gronovii 0.01 4.15 0.08 -- Cyperus sp. -- -- 0.51 1.37 Echinochloa crus-galli* ------0.43 Hibiscus moscheutos 0.26 0.53 1.26 0.03 Hydrilla verticillata* 0.18 0.08 -- -- Impatiens capensis 15.57 31.92 4.38 1.73 Iris pseudacorus* -- -- 4.38 -- Juncus effusus -- -- 0.59 5.93 Laportea canadensis 0.09 ------Leerzia oryzoides 1.80 1.71 33.64 30.96 Lycopus virginicus -- -- 0.17 0.09 Lythrum salicaria -- -- 1.52 6.38 Mentha canadensis -- -- 0.40 Mikania scandens -- -- 0.08 0.94 Najas minor* 0.06 0.17 -- -- Nuphar lutea 15.04 12.45 -- -- Onoclea sensibilis 0.33 -- -- Peltandra virginica 22.69 12.26 15.18 4.53 Phragmites australis* 0.30 -- 1.35 2.73 Pilea pumila -- 0.26 -- -- Polygonum arifolium 1.62 3.72 5.82 0.24 Polygonum persicaria* 0.02 0.50 -- -- Polygonum punctatum 0.20 1.23 -- -- Polygonum sagittatum -- 0.01 7.00 0.09 Pontederia cordata -- 0.35 0.59 1.91 Ranunculus sceleratus 0.03 ------Rumex verticillatus ------0.18 Sagittaria latifolia 1.19 0.16 0.76 5.62 Salix sp. ------3.65 Saurus cernuus ------

33 Table 13. Continued. Schoenoplectus fluviatilis 4.35 4.92 -- 1.64 Schoenoplectus pungens -- -- 3.88 2.13 Schoenoplectus tabernaemontani 0.29 -- -- 0.03 Scirpus cyperinus ------1.64 Sicyos angulatis -- 0.08 -- -- Solanum dulcamara* 0.28 ------Sparganium eurycarpum -- 0.02 -- -- Typha sp. 19.28 12.58 5.14 14.04 Zizania aquatica 0.56 0.61 -- 0.18

Table 14. Percent density of seedlings from each species relative to total number of seedlings. We compare the vegetation at Dyke Marsh Preserve (DMP) for 2003 & 2004, these values are also compared to the Baldwin and DeRico (1999) study that documents vegetation cover in a reference and restoration site nearby DMP. Bolded numbers signify “dominant” species, and * represents non-native species. DMP Baldwin and DeRico (1999) Species 2003 2004 Reference Restored Amaranthus cannabinus 2.55 2.54 0.42 0.13 Aneilima keisak* 0.04 ------Apios americana ------1.12 Bidens cernua 0.13 ------Bidens frondosa ------0.01 Bidens laevis 0.61 0.69 -- -- Bidens tripartita -- -- 0.08 0.16 Boehmeria cylindrica 0.04 -- 0.08 -- Calystegia sepium* -- 0.06 -- -- Carex sp. 0.13 ------Cuscuta gronovii 1.54 3.87 0.17 0.01 Cyperus odoratus -- -- 17.39 24.56 Cyperus sp. 0.04 -- 4.49 0.78 Echinochloa crus-galli* -- -- 0.33 1.58 Echinochloa muricata 0.09 ------Eclipta prostrata ------0.02 Eleocharis obtusa -- -- 0.42 1.62 Hibiscus moscheutos -- 0.06 0.75 0.01 Hydrilla verticillata* 1.67 ------Impatiens capensis -- 18.73 -- -- Juncus effusus 0.26 0.17 31.86 23.47 Leersia oryzoides 0.66 1.73 12.48 9.89 Lindernia dubia -- -- 0.58 6.50 Lobelia cardinalis -- 0.06 -- -- Ludwigia palustris 0.79 3.06 -- 0.02 Ludwigia repens 0.04 ------Lycopus virginicus ------0.07 Lythrum salicaria -- -- 18.97 13.64 Mentha sp. ------0.03 Mikania scandens 0.04 0.52 0.75 0.06

34 Table 14. Continued. -- -- 0.08 -- Najas minor* 0.53 2.36 -- -- Peltandra virginica -- 0.29 -- 0.02 -- -- 0.17 0.05 Pilea pumila 0.31 1.27 -- -- Polygonum arifolium 0.22 1.16 0.08 -- Polygonum lapathifolium ------0.52 Polygonum persicaria* 0.88 0.12 -- -- Polygonum punctatum -- 0.29 -- 0.07 Polygonum sagittatum -- -- 0.25 0.01 Ranunculus sceleratus -- 0.12 0.17 0.06 Rorippa islandica -- -- 0.58 0.31 Rorippa palustris 0.13 0.12 -- -- Sagittaria latifolia 0.26 1.21 0.42 0.19 Schoenoplectus fluviatilis 0.13 0.12 -- -- Schoenoplectus tabernaemontani 0.04 0.29 0.08 0.06 Solanum dulcamara* 0.09 ------Trifolium repens -- 0.06 -- -- Typha sp. 88.48 60.23 6.24 8.83 Ulmus rubra -- -- 0.17 0.04 Vallisneria americana 0.09 ------Zizania aquatica 0.04 0.75 -- --

Table 15. Annual species significance in the Invertebrates vegetation and seed bank studies. In 2000, Dan Kjar along with Dr. No. of % of Relative % Edward Barrows, both from Georgetown annual total cover of University, inventoried terrestrial Location species species marsh Vegetation arthropod and alien plant diversity in the DMP 2003 10 30 11 forested areas of Dyke Marsh. Pitfall DMP 2004 12 38 24 traps were used to survey the Kenilworth marsh arthropods. They found 243 species (restored)* 12 40 30 and morphospecies from 7 classes, 28 Reference marsh* 7 30 9 orders, and 72 families (Barrows and

Seed Banks Kjar 2003). DMP 2003 11 34 n/a Arthropod population distributions DMP 2004 12 48 n/a across time can be highly variable; in Kenilworth marsh (restored)* 11 46 n/a fact, few species show any trend at all. Reference marsh* 14 47 n/a Kjar and Barrows found that the * signifies data from Baldwin and DeRico (1999). arthropod abundance did not vary significantly at phylum level among their sites, but they did find varying significance at some lower taxonomic levels. Small differences were found in species richness, evenness and diversity among sites, yet overall, few

35 patterns of abundance or diversity pertaining to arthropods were apparent. Kjar believes that differences in arthropod abundance may be the result of soil moisture, absence of exotic species, interaction of arthropods, variation between plots or a combination of these factors. Future work by Kjar involves a large-scale survey with replicate sites to determine if terrestrial arthropod diversity is associated with Figure 21. Bluegill sunfish (Lepomis the level of invasion by alien invasive macrochirus). plants (Barrows and Kjar 2003). The data from the surveys suggest Fish that Dyke Marsh provides habitat for a An inventory of the various fish large variety of juvenile and adult fish species found in and around the Dyke species. Specifically, it is an important Marsh area was conducted between nursery for sunfish, Alosa sapidissima 2001 and 2003. Mike Mangold, with the (American shad) (Figure 22), Alosa U.S. Fish and Wildlife Service headed aestivalis (blueback herring) and Alosa this three-year study. The goal of the pseudoharengus (alewife) (Mangold project was to provide a baseline 2004, pers. comm.). inventory of fish species that currently inhabit Dyke Marsh on the Potomac River. Specimens were collected through gillnetting, fykenetting, small minnow traps, large clover traps, eel pots and boat shocking. Over 15,000 specimens collected were separated into 37 fish species, and 3 turtle species. The three most Figure 22. American shad (Alosa common fish species identified were sapidissima). Lepomis macrochirus (bluegill sunfish) (Figure 21), Lepomis gibbosus Breeding Bird Surveys (pumpkinseed sunfish), and Fundulus Larry Cartwright and other members diaphanus (banded killifish). of Friends of Dyke Marsh completed the 2003 Dyke Marsh Breeding Bird Survey. 2003 was characterized as an unusually late breeding season. It is hypothesized that the extremely wet and chilly conditions in May and early June may have forced some birds to delay breeding until temperatures increased and the rains decreased. Evidence of high water washout of nests and second breeding attempts were found.

36 Regardless of the harsh conditions any significant habitat characteristics in early on, the survey documented a total breeding sites. of 95 species. 46 of the species were Reproductive success in 1998 confirmed breeders in Dyke Marsh, 6 consisted of 9 fledglings from 7 nests, species were probable breeders, 15 and 31 eggs (29%). In 1999, 11 species were possible breeders, and 25 fledglings from 20 nests and 80 eggs were present at some point during the (14%) were found. It was discovered survey period, but deemed not to be in that the majority of nests were lost to suitable breeding habitat (see Appendix predation by other birds, snakes, or G, Cartwright 2004). Cartwright and mice. Alternative vegetative species volunteers found osprey to be the first that nests were found attached to confirmed breeder, which is consistent include Acorus spp., Hibiscus with past years. They also think that moscheutos, Phragmites australis, marsh wrens appear to be recovering Amaranthus cannabinus, and Juncus from their population crash of 2001, and spp. An important finding was that all of are slowly reoccupying the south end of the successful breeding nests were the marsh (Cartwright unpublished data found attached only to Typha sp. 2004).

Marsh Wren Sandy Spencer completed a study of marsh wren (Cistothorus palustris) in Dyke Marsh Preserve from 1998-2000 with George Mason University (Figure 23). Objectives of the study were to establish the current abundance of population, determine important habitat characteristics, measure reproductive success, examine alternative types of Figure 23. Marsh wren (Cistothorus palustris) vegetation for nest sites, and verify if Dyke Marsh is the only suitable Comparisons were made at similar breeding habitat on the upper Potomac local sites to assess the importance of River. habitat at Dyke Marsh for marsh wrens. Spencer (2000) found 31 male Comparison sites visited include Great territories and 7 breeding territories in Marsh at Mason Neck National Wildlife 1998, resulting in a minimum population Refuge, Marumsco Creek at Occoquan of 38 wrens. In 1999, 34 male territories National Wildlife Refuge, Mattawoman and 14 breeding territories were found. River on the western shore of the The 34 male territories comprised 13.89 Potomac River, and Kenilworth Marsh acres (30%) of the total available habitat on the Anacostia River. Overall, in Dyke Marsh in 1999. Male marsh Spencer (2000) found the Typha at all wrens prefer dense and tall vegetation comparison sites to be less dense than near steeper sloped shorelines. the Typha stands at Dyke Marsh. This Spencer (2000) found male-defended is suggested to be the reason why very territories abandoned where Typha few numbers of marsh wren were seen density was below 50%, and did not find or heard at the comparison sites, as well

37 as why very few if any active nests were only suitable habitat for a breeding found. Therefore, Spencer (2000) marsh wren population in the upper tidal claims that Dyke Marsh provides the zone of the Potomac River.

LITERATURE CITED

Baldwin, A. H. and E. F. DeRico. 1999. The seed bank of a restored tidal freshwater marsh in Washington, DC. Urban Ecosystems 3:5-20.

Barrows, E. M. and D. S. Kjar. 2003. Biodiversity Database of the Washington, D.C. Area. Website. http://biodiversity.georgetown.edu (March 12, 2004).

Cartwright, L. 2004. Breeding Bird Survey for Dyke Marsh Preserve. Unpublished data.

Gee, G. W. and J. W. Bauder. 1986. Particle-size Analysis. P. 383-411. In A.L. Page (ed.) Methods of soil analysis, Part 1, Physical and mineralogical methods. Second Edition, Agronomy Monograph 9, American Society of Agronomy, Madison, WI.

Harper, J. D. and F. D. Heliotis. 1992. Dyke Marsh Hydrologic Model. George Mason University, Fairfax, VA. 109pp.

Palermo, M.R. and T.W. Zeigler. 1976. Feasibility study for Dyke Marsh demonstration area Potomac River, . U.S. Army Engineer Waterways Experiment Station Technical Report D-76-6.

Spencer, S.C. 2000. Population abundance and habitat requirements of the marsh wren (Cistothorus palustris) at Dyke Marsh National Wildlife Preserve. M.S. Thesis. George Mason University, Fairfax, VA.

Xu, Z. 1991. Final report on inventories of plant species and communities in Dyke Marsh, Alexandria, Virginia. George Mason University, Fairfax, VA. 67pp.

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