Millennial Pre-settlement Stability of

Sedge Meadow Habitats in Two Piedmont River Valleys

William Hilgartner1, Dorothy Merritts2, Robert Walter2, Michael

Rahnis2, Christopher Berhardt3 , Jeff Hartranft4, Ali Neugebauer2,

Mark Voli2, Hanna Jantzi2, Amy Moser2, and Candace Grand Pre2

Carex stipata Carex stricta

Carex crinita Eleocharis ovata**

This presentation focuses on a paleoecological analysis of fossil seeds from core and river bank samples, combined with pollen

analysis, geomorphic data and land use history of two river sites in Maryland and Pennsylvania

First Site: Little Falls, northern Baltimore County, Maryland,

Little Falls, Baltimore Co., Maryland

Site of Core LFC1

Holocene hydric layer

Legacy Sediment

River Bank Stratigraphy

Post-settlement Silt & Clay Layer aka “Legacy Sediment”

Holocene Hydric Layer

Late Pleistocene Gravel Layer

Core LFC 1

C-14 Date Intercept Age = 4,970 yr BP

C-14 Date Intercept Age = 300 yr BP

56 cm

0 cm

Black clay & plant fragments 10 YR 2/1

RESULTS: Macrofossil Profile LFC1

Analyst: W. Hilgartner

Pollen Profile LFC1

Ragweed Increase ca. A.D. 1730

Increase in Alder

Analyst: C. Bernhardt

Oak decline

Ragweed Increase 6.0 cm = ca. A.D. 1730 Alder increase

0 cm = ca. A.D. 1775

C-14 = 4970 BP

Sorensen’s Index of Similarity

Note: Consistent indices > 40% from 4300 BP to 1775

Initial establishment of Carex stricta ~4300 BP

Results: A stable tussock sedge wetland

persisted from 4300 yr BP until A.D. 1775.

Hydrology of Prehistoric Wetland at

Little Falls …Absence of

paleo-channels

- springs from

Valley margin;

- ground water

table at 1.0 cm;

- saturated soil

Tussock Sedge Wetland, Great Marsh, Chester Co., PA

Initial habitat change began ca. A.D. 1730 when Carex stricta declined and Alder (Alnus serrulata) became

established

Burial between 1775 and 1835

The tussock sedge wetland (tsw) was rapidly buried within 60 years between ca. A.D. 1775 and 1835, when 1.0 – 2.0 m of silt and clay sediment (Legacy Sediment - LS) accumulated in a reservoir behind a downstream mill dam.

tsw

LS

5,000 BP

A.D. 1775

A.D. 1835

18th to 20th Century Dams at Little Falls

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8 10 12 14

So

ren

so

n's

In

de

x

Matrix Point

GRAPH 2: Sorensons Indices Comparing Seed Species in Pairs of Surface Samples

STUDY AREA

Mill Dam

Mill DamSaw Mill

Railroad Spur

Dam (?)

Grist & Saw Mill Dam

Paper Mill Dam(partly rebuilt)

Water surface

Reservoir fill terrace

Distance (ft)

Ele

va

tio

n (

ft)

20,000

400

350

300

10,000 0

LITTLE FALLS: Elevation Profile

Breach of the mill dam created an incised, high-banked

meandering river channel …..

This incision exposed the legacy sediment and underlying prehistoric

tussock sedge wetland, periglacial gravel, and bedrock.

LS

BW

VB

Lateral sediment samples show tussock sedge wetland extent (23 m)

Carex stricta

Carex stricta Alluvial Fan interrupts wetland

The Second Site:

Big Spring Run, Lancaster Co., PA

Holocene Hydric layer

Legacy Sediment

Big Spring Run, Lancaster Co., Pennsylvania

Macrofossil Sampling Site

Big Spring Run

160± 40

140± 40

90 ± 40

270 ± 40 230 ± 40

230 ± 40

850 ± 40

1220 ± 40

2860 ± 40 3000 ± 40

All but one date on single nut.

Big Spring Run, PA, Buried Wetland Soil Radiocarbon (AMS) Dates Dates and Paleo-seed Sampling

European settlement 1709

Macrofossil sample column

0 170 cm

C-14 dates and Depths of the Macrofossil Sampling Site

120 cm 72 cm

Pollen in upper layers of the sample column

(85 cm – 114 cm)

Ragweed increase

Decline in oak & hickory

Analyst: C. Bernhardt

O:R = A.D. 1730

160± 40

140± 40

90 ± 40

270 ± 40 230 ± 40

230 ± 40

850 ± 40

1220 ± 40

2860 ± 40 3000 ± 40

All but one date on single nut.

Big Spring Run, PA, Buried Wetland Soil Radiocarbon (AMS) Dates Dates and Paleo-seed Sampling

European settlement 1709

Macrofossil sample column

0 170 cm

Pollen Date Added (in red)

72 cm

A.D. 1730

Carex prasina type (n =165) -drooping sedge Obligate wetland perennial

0 5 10 15 20

72768084889296

100104108112116120124128132136141147157

Number of Seeds

De

pth

(cm

)

795 BP 1540 BP 3000 BP

Wet Meadow

72

80

88

96

104

112

120

128

136

144

152

160

De

pth

(cm

)

Dandelion seed at 106 cm

Oak:ragweed Horizon (Pollen Date)

ca. 1730 at 102 cm

Initial settlement 1709 at 120 cm?

Eleocharis obtusa (n = 125)- blunt spikerush (syn: E. ovata) Obligate wetland perennial

0 10 20 30 40 50 60 70 80

72

76

80

84

88

92

96

100

104

108

112

116

120

124

128

132

136

141

147

157

Number of Seeds

De

pth

(cm

)

795 BP 1540 BP 3000 BP

Mud Flat

72

80

88

96

104

112

120

128

136

144

152

160

De

pth

(cm

)

Wet Meadow

ca. 1730

Alisma plantago-aquatica (n =27)- water plantain

Obligate wetland, aquatic (up to 15-cm water depth)

0 1 2 3 4 5 6 7 8

72

76

80

84

88

92

96

100

104

108

112

116

120

124

128

132

136

141

147

157

Number of Seeds

De

pth

(cm

) 795 BP 1540 BP 3000 BP

Pond

Mud Flat

72

80

88

96

104

112

120

128

136

144

152

160

De

pth

, cm

Wet Meadow

ca. 1730

A.D. 1730

Pre-settlement Habitat Stability Based on the Continual Presence of C. stipata & C. prasina

Carex stipata (green bar)

Carex stipata (green bar)

Eleocharis

Alisma

Carex hystericina

Carex prasina type

Sorensen’s Similarity - BSR Samples

-20

0

20

40

60

80

100

120

0 20 40 60 80 100 120 140 160 180

Pe

rce

nt

Sim

ilari

ty

Depth (cm)

Pre-settlement Period Post-settlement Period

Summary….. Pre-settlement Wetland Stability…

…was maintained over millennia despite these disturbances: - a high charcoal/drought period, ca. 4,000 - 4200 BP, - presumed high abundance of beaver activity - tropical storms and flooding events - prehistoric human disturbance. This long-term wetland stability indicates… - a forested watershed (~100% forest cover) acted as a storm and erosion

buffer - low sedimentation rates entered the valley (0.01 cm/yr at both sites) - constant water table level and stable hydrology - no ponds from beavers in either valley - no main channel; instead low flow anastomosing system

Post-settlement Habitat Change

A sudden period of rapid sedimentation from deforestation combined with multiple mill ponds and dams during the 18th and 19th centuries was the first event in > 4,000 years to produce succession and decline in these wetlands.

Sedge meadow wetlands, especially tussock sedge

wetlands are the favored habitat of the endangered bog turtle (Glyptemys muhlenbergii) in Maryland and

Pennsylvania

Decline of Bog Turtle Habitat

The greater extent of prehistoric sedge meadow wetlands and their subsequent reduction by dams may help explain the modern disjunct distribution and decline of the bog turtle.

One solution to the decline in bog turtle habitat is restoration…removal of the legacy sediment to expose the

underlying sedge meadow wetland.

Acknowledgements: Funding: Franklin and Marshall College, PA Dept of Environmental Protection, PA Chesapeake Bay

Commission, EPA, and NSF (MRI and NCALM) Students of Franklin and Marshall College; John Hart-Smith of Johns Hopkins University Landowners at Big Spring: Joseph Sweeney (sold property in 2011); The Kirchner family (current owners) Great Marsh owners are Jim Moore and family

Affiliations: • 1 Contact Information: William Hilgartner, Johns Hopkins University and Friends School of Baltimore. Mailing (Home Office)

Address:137 Hopkins Rd, Baltimore, MD 21212. Cell: 443-834 -6116, Email: hilgartner@jhu.edu • 2Franklin and Marshall College, Lancaster, PA. • 3U.S. Geological Survey, Reston, VA. • 4 Department of Environmental Protection, Harrisburg, PA.