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NA90AA-D-CZ795 Task 8 @<ASSESSMENT OF THE ENCROACHMENT OF WOODY VEGETATION INTO FIVE UNFORESTED DELMARVA BAYS AND FIVE COASTAL PLAIN BOGS BY ANALYSIS OF AERIAL PHOTOGRAPHY Submitted to the Coa@;tal Resources Division Tidewater Administration NI& by the Maryland Natural Heritage Program Resource Conservation Service Prepared by: Katharine A. McCarthy Judith R. Modlin April 1992 INTRODUCTION Delmarva bays and bogs are the most significant nontidal wetland habitats for rare plant species on Maryland's Coastal Plain. These two habitattypes harbor more rare species than all other nontidal wetland types of coastal Maryland. In both bays and bogs, the majority of rare species occur within non-forested, herbaceous openings,.. Bogs also characteristically support low shrubs scattered throughout the herbaceous openings. Field observations by local naturalists and Natural Heritage Program Staff in the 1980s indicated that saplings and tall shrubs were encroaching on these openings and may threaten the rare, shade- intolerant, herbaceous species. To address this concern, this study was undertaken to determine,the extent of change in size of herbaceous openings for five bays and f 'ive bogs known to harbor high concentrations of rare species (Appendix I). Vegetation cover was assessed from aerial photographs dating from the 1930s to the 1980s. The results of the analysis of woody plant succession in bogs will assist in determining which bogs-are to be studied in further detail in the field beginning in summer 1992. Knowledge gained from the field study and the study of historical change in bog size will be incorporated in the development of management plans for selected.bogs. As with all wetlands, hydrology influences the composition of vegetation in Delmarva bays-. The duration of flooding appears to be the major influence limiting the establishment of trees in the herbaceous openings of Delmarva bays. Fire and grazing have been suggested as historical influences limiting woody encroachment; however, data has not substantiated these theories for Maryland's bays. Maintenance of the hydrologic regime therefore appears essential to the maintenance of the herbaceous openings that support rare plant species. Because land use practices influence hydrology, we initiated a study of surrounding land use in conjunction with the assessment of change in size of herbaceous openings for five Delmarva bays. METHODS A set of three historical aerial photographs was'obtained for all Coastal Plain bogs and Delmarva bays that are listed as Geographical Areas of Particular Concern (GAPC's) in Maryland. The earliest available aerial photograph for each site (1930s- 1940s) was obtained to serve as a baseline against which to compare vegetation changes in later photographs. These early photographs were U.S. Soil Conservation Service photos obtained in person fromthe National Archives and Records Administration in Alexandria, Virginia. We reviewed photographic reels, selecting the frame that offered the best resolution for each bay or bog. The most recent aerial photography available commercially was generally at too small a scale to adequately resolve differences in vegetation type. Therefore we used the most recent photographs flown at an appropriate scale (1:24,000 or larger). These photographs were flown primarily in 1985 and were available in-house from the Water Resources Administration or the Natural Heritage Program (both Maryland Department of Natural Resources). A third set of photos of intermediate date (1957 - 1958) and appropriate scale, flown by SCS, were obtained by mail from the U.S. Department of Agriculture, Agricultural , .Stabilization and Conservation Service in Utah. For two sites, additional, larger-scale historical photographs were available from Anne Arundel County. These were used to better understand and describe the vegetation history at those sites, but were omitted from the analysis of changes in area because large differences in scale made it hard to consistently interpret vegetation changes. Based on the quality of available photos, site protection priorities, ownership patterns, and geographical distribution, five bays and five bogs were selected for analysis (Table I). Each photo was scanned using the Map and Image Processing system software (MIPS, by MicroImages, Inc., Lincoln, Nebraska, version 3.x). Scanning was done at 400 dpi using aHowtek Scanmaster 3, Hewlett-Packard (HP) Vectra 486/25T personal computer, an HP 1611 high-resolution UGA color monitor with Metheus 1228 UGA graphics board, and an HP VGA color monitor for text. The images were stored on optical disk using a Relax MO Plus, 600 MB Optical Drive. Each photograph was examined under magnification to determine the boundary between the herbaceous opening and woody cover (bays) or between herbaceous/low shrub cover and tall woody cover (bogs). Open water was included in the measurement of herbaceous openings because it fluctuates seasonally and areas covered.by open water in one season may support bay or bog 2 vegetation'observable at another time of year. The area of the opening was calculated for each site in each year using the'MIPS "planimeter" program. In order to assess the reliability of the results, each measurement was repeated a minimum of four times and the mean area was calculated. For each site, the significance of differences among mean areas in different years was assessed using the student's t-test. We noted that the stated scale of the photographs was not always accurate. To correct for minor scale inconsistencies or image distortion, each bog photograph was calibrated by using the MIPS "calipers" program to measure the distance@between two landmarks near the bog and common to all three photos. Differences in the measured distance were used to produce an area calibration factor for each photo, and area calculations were corrected accordingly. For bay sites, each photograph was registered against registered Land Sat spot imagery prior to analysis of surrounding land use patterns. Photo registration assisted in correcting for scale discrepancies and photo distortion. Surrounding land use was analyzed for-the five Delmarva bays at intervals of 30m, 60m, 100m, and 300m from the edge of the herbaceous opening outlined in the earliest available photo (1930s). For consistency, the 1930s herbaceous opening was used as the basis for these interval measurements for the 1950s and 1985 photos as well. The "vector buffer" function of MIPS was used to create polygons at these intervals around the herbaceous opening. Prints showing these polygons for Dorchester Pond were produced using an HP Paintjet XL printer and are included as Appendix II. Within each distance interval, area was measured for the following classes of land use: cultivated fields, old fields, forest, and recently logged. Area was calculated with the MIPS "planimeter" function. The length of roads and ditches occurring within each interval was measured with the MIPS "calipers" function. The number of buildings present was recorded for each interval. 3' RESULTS Coastal Plain Bogs The size of herbaceous/low shrub openings at all bog sites declined significantly (P < .005)between the 1930's or 40's and the 1980's (Tables II and III). The greatest proportional decrease in size occurred at Suitland Bog, where the size of the opening in 1981 was only 6% of its size in 1937 (Table IV), an average rate of decline of 2.1% per year. The opening at Suitland Bog was the largest of all sites studied in the 1930's and 1940's (4.1 ha in 1937) but the second smallest by the 1980's (0.26 ha in 1981).. Most of the loss occurred between 1937 and 1957, when opening size decreased by 81%. The next largest proportional declines in opening size occurred at the two Eastern Shore sites. At Horsebridge Creek Bog in 1985 the opening had decreased to 24% of its 1938 size- (1.6% decline per year). The total opening at Sharptown Bog had declined in 1985 to 31% of its 1938 size (1.5% per year). The real loss of bog vegetation at these two sites was probably even greater. At Horsebridge Creek Bog in 1938, a wide, herbaceous wetland opening surrounded both sides of Horsebridge Creek for more than 1/4 mile of its length. Between 1958 and 1985, the creek was channelized and a powerline right-of-way constructed across it; the only openings remaining in 1985 were the narrow stream channel and the artificially maintained right-of-way where the powerline crossed the bog. Most of this opening would not have been wet enough to support bog vegetation. All rare species reported in mid-1980's field surveys at this site were confined to two small boggy depressions under the powerline. Sharptown Bog was already traversed by a powerline in 1938, but the right-of-way had not been recently cleared and most of the 0.5 ha opening measured-in that year appeared to be a natural herbaceous opening along a stream. By 1958, the powerline right- of-way was cleared and the streamside opening was beginning to close in with woody vegetation. By 1985, the entire streamside opening outside of the powerline right-of-way had become forested. Patterns of vegetation change were observed more closely at the two Anne Arundel County bogs due to the availability of large-scale photographs from intermediate years. -In 1943, Gumbottom Wetland contained an apparently all-herbaceous opening of approximately .5 ha, clearly distinct from a very large adjacent shrub swamp. By 1952 and 1957 the.distinction was less. clear, as shrubs had begun to move into the herbaceous opening. By 1970, much of the opening was dominated by low shrubs, but it was still distinct from the taller shrub canopy of the shrub swamp. By 1984 and 1985,.the size of the opening had decreased 4 to less than 1/3 hectare (.28 ha in 1985), and tall shrubs had penetrated into the interior of theopening in some locations. Gumbottom Wetland showed the lowest proportional decline in area of opening among the bog sites. In 1985, the size of the opening was 53% of its 1943 size. The decrease occurred much more rapidly between 1943 and 1957 (2.3% per year) than between 1957 and 1985 (0.5% per year). North Gray's Bog had the largest herbaceous/shrub opening in 1985, with an area of 1.1 ha. Although it is known from field surveys that part of this opening is composed of an open water pond and emergent marsh, this portion is important because it represents area forpotential bog expansion. This is the only site studied where the bog appears to be in the early stages of formation, with a thick peat mat gradually growing gradually out over the still water. North Gray's Bog showed the second lowest' proportional decline in area, decreasing to 42% of its 1948 size by 1985. It was the only site in which the greater decline occurred between the 1950's and the 1980's (2.1% decline per year).@ The area of the opening at this site stayed the same between 1948 and 1957. Intermediate photos indicate that the decline had begun by 1970, when a tall shrub canopy had begun to penetrate the opening in the drier, eastern end of the site. ,Delmarva Bays Change in Area of Herbaceous Opening The area of herbaceous openings declined significantly (P < 0.01) from the 1930s through 1985 for all five bays studied (see Tables V and VI). For all sites, the-herbaceous openings consistently decreased in area from the 1930s to the 1950s and from the 1950s to the 1980s with one exception. Bridgetown Pond increased in area from 1958 to 1985; however, the herbaceous opening was significantly smaller in 1985 than it was in 1937 as a result of the significant decrease in area from 1937 to 1958. The largest proportional decrease in size of herbaceous opening occurred at Jackson Lane. The mean area of the opening in 1985 was 29% of the mean area in-1937. By 1985, the herbaceous opening at Golts Pond had decreased to 55% of its size in 1@37. By 19Z5 Black.Bottom Pond had decreased to 73% of its area in 1936. The smallest decreases in area of herbaceous opening were recorded for Bridgetown Pond and Dorchester Pond. By 1985, both of these sites declined to 91% of the areas recorded for 1937 and 1938 respectively. The decrease in area of herbac eous opening was larger from the 1930s to 1950s than in the subsequent period ending in 1985 for all sites with the exception of Dorchester Pond. 5 Land Use Analysis .Two. of the five sites, Black Bottom Pond and Bridgetown Pond, experienced little change in land use from the 1930s to 1985 (Table VII). Over 80% of the surrounding land remained forested within loom of the bays throughout the study period. Virtually no disturbance was evident within 60m of these bays during this period. of the four relatively small bays, Black Bottom and Bridgetown also experienced the least encroachment of woody species during the study period. The general trend in land usage observed from.the 1930s to 1985 was of farm fields reverting to forest. At Dorchester Pond, Golts Pond, and Jackson Lane, 1/3 to 1/2 of the land within loom of the bays was farmed in the 1930s. By 1985 all but 5% of this land had reverted to forest. In general, as fields reverted to forest, roads were abandoned so the length of roads present in all intervals generally declined during the study period. T 'he exceptions to this were at Golts Pond and Dorchester Pond. Numerous residences occur within 300m of Golts Pond and a few new roads were constructed to increase access to these properties. At Dorchester Pond, as fields were abandoned, roads were maintained at the field edges to provide access to nearby fields that remained in cultivation. This gave the appearance of an increase in road length in the.60-100m interval. No major ditches lie within 300m of the five bays studied. Field surveys revealed that small ditches are present at most of these bays, however, they are not visible in the aerial photographs. The forest-canopy conceals these ditches, so this is not an effective method to evaluate the position and effect of ditches. Logging was evident at both Dorchester Pond and Bridgetown Pond. At Dorchester, logging occurred in the 1930s in all intervals studied and beyond 300m to the south of the bay. At Bridgetown Pond, young irregular stands of pine along sand roads in the 1937 photo suggest that logging had recently occurred in the 100-300m interval. Areas of relatively open canopy in the 1958 photo suggest that logging occurred again in the 100-300m interval. I New powerlines were constructed between 1957 and 1985 crossing the 100-300m intervals at Golts Pond and Black Bottom Pond. Of the five bays studied, only Golts Pond had more than two buildings present within 300m of the bay. The bays occur in rural areas where lots tend to be large and houses widely dispersed. However Golts Pond lies near a small t 'own center. In 1936, 24 buildings were located within 300m of the bay. Half of these were abandoned and by 1985 just 11 buildings.remained. 6 DISCUSSION Coastal Plain Bogs The encroachment of woody species into Coastal Plain bogs is a natural process of vegetation succession in which unforested bogs slowly become dominated by trees. Historically, new,sites developed that were suitable for colonization by shade intolerant bog vegetation, such as the edges of beaver ponds, old stream meanders, and openings in swamps created by fire during dry years., Today, a large portion of the landscape has been converted to residential, industrial, commercial, or agricultural uses, and most of Maryland's Coastal Plain bogs, many of which were located in counties now heavily urbanized, have been destroyed. Potential sites for new bog formation have also been destroyed, and the disturbances which created them, such as fire and flooding, have been suppressed. Because the natural development of new sites for bog formation can no longer keep pace with the accelerated loss of Maryland's few remaining bogs, the natural succession of woody species into those bogs threatens the survival of this unusual habitat. If unique Coastal Plain bog plant communities are to survive, active management to curtail woody encroachment into bogs may be required at some sites. Potential methods of woody species control include prescribed burns, flooding by blocking drainage ditches or reconstructing old dams, selective herbicide use, and removing tree saplings by hand. Each method has advantages and drawbacks. Burning and flooding may best mimic natural disturbances that maintained bog openings, but fire may not be feasible in .urban/suburban landscapes and flooding may-have direct,negative impacts on existing rare species. Herbicide use would have to be planned and executed with extreme caution to avoid damaging rare species or contaminating water or soil. Hand removal may be the most prudent and conservative choice, but even this choice requires caution and careful timing of work to minimize trampling fragile bog habitats. Decisions regarding vegetation management should be made after on-site research to evaluate such factors as the rate of woody encroachment into the bog, surrounding land use, and hydrology. The Maryland Natural Heritage Program has contracted to establish permanent plots at two bogs to measure the rate of tree. sapling encroachment over time and to provide management plans to control woody invasion at these sites. Together with a knowledge of ownership patterns and management history, the analyses of historical aerial photos provided information useful in determining which sites can profit most from on-site evaluation and control of woody encroachment. 7 Of the five bogs examined, Suitland Bog exhibited the highest rate of decline in size of opening. However, it may be least in need of intervention by the Natural Heritage Program because the site is owned and managed by the Maryland-National Capital Park and Planning Commission, which is actively working to protect it. The site's hydrology has been studied and the aquifer that feeds it has been purchased to protect the source of water. Berms, a boardwalk and a chain link fence around the major bog opening have been constructed to curtail erosion, trampling and dirt bike use. Efforts are underway by park staff to educate the public and to control woody encroachment manually. Thus Suitland Bog already receives the greatest degree of protection and management of any of the.five sites studied. Since the only openings remaining at Sharptown Bog and Horsebridge Creek Bog are within powerline rights-of-way, power company officials have instituted their own programs to control woody encroachment. At these sites, the Natural Heritage Progr,am's most profitable role will be maintaining continued landowner contact, particularly continued involvement in the development of management plans for the sites. We have provided the owners with maps and rare species reports and they have agreed to omit the bogs from broadcast herbicide application. Continued contact is essential to ensure that this agreement is followed. We also need to work with adjacent owners to preserve a forested buffer and to avoid repetition of the disastrous dragging of timber through the powerline opening that destroyed much of Sharptown Bog in the 1980s. At both Sharptown and Horsebridge Creek Bogs, monitoring of rare species and of exotic species is needed. The two sites with the greatest potential to benefit from tracking the encroachment of woody species and developing vegetation management plans are Gumbottom Wetland and North Gray's Bog. These sites currently support the largest herbaceous openings and they experienced the smallest decrease in area over the study period. (The total opening at Horsebridge Creek is larger.than at Gumbottom, but only'a small portion of it supports bog vegetation.) They have the largest forested buffers,- the least deleterious land use in the immediate vicinity and probably the lowest rate.of invasion by non-native, weedy species. Permission to study and eventually manage both sites, if needed, should be easier to obtain at thesetwo sites than at most bogs. Gumbottom Wetland is owned by the Maryland Department of Natural Resources. The homeowner's association that owns North Grayls Bog has registered the bog and its buffer, encouraged--scientific research by the Natural Heritage Program, and requested that Natural Heritage develop a management plan for the,site. Lastly, woody vegetation that is likely to eventually threaten bog species has been observed on site at both Gumbottom and North Gray's Bog,.so both sites would benefit from the monitoring and control of woody encroachment. 8 Delmarva Bays The two bays experiencing the greatest decr 'ease in size of herbaceous opening, Golts Pond and Jackson Lane, were both nearly surrounded by agricultural fields in the 1930's that reverted to forest by the 1950s. This suggests that agricultural activity may have contributed to maintaining the herbaceous opening at these sites. For example,,these areas may have been maintained for grazing. It is also possible that the decrease in the herbaceous openings is associated with natural succession of the abandoned agricultural fields. Evapotranspiration is particularly high in the early years of succession*when young trees of colonizing species grow most rapidly. This high rate of evapotranspiration may have reduced the water available to the bays and shortened the duration of flooding along the bay perimeter. With less flooding, woody species would establish more readily. This scenario is further supported by the slower decrease in size of herbaceous opening that occurred from the 1950s to 1985, when both the growth rate and evaporatranspiration of the young forest would have slowed. Of the five bays, Dorchester Pond was-the exception in experiencing a more rapid decrease in the herbaceous opening from the 1950s to 1985 despite extensive logging in the 1930s and its proximity to reverting agricultural fields. According to recent findings of the U.S. Geological Survey (Pat Phillips, personal communication), the four smaller bays in Caroline and Kent Counties lie in the same hydrogeologic region, meaning they share similar patterns of groundwater and surface water movement due to similarities in elevational gradient, soil type, and geology. However, Dorchester Pond is in a different region with different hydrological characteristics and therefore may respond differently to changes in land use. It may-also be of significance that a large portion of forested land within loom of Dorchester Pond was converted to pine plantation between the 1950s and 1985. 'These evergreens have a higher total annual transpiration rate than deciduous trees. The presence of a high density of pine close to the bay may reduce the available water and thus shorten the duration of flooding in the bay and promote woody succession.along the bay perimeter. Field observations indicate that the slight increase in size of the herbaceous opening at Bridgetown Pond may be the result of oaks dying from gypsy moth defoliation, Additional bays must be studied so that the sample size is larger in order to develop conclusive evidence of the effects of land use practices on Delmarva bays. However, the results of this study suggest that maintenance of mature, natural forest cover, especially within loom of a bay, may contribute to maintaining the herbaceous openings and the rare species they harbors. 9 The bays experiencing the most rapid decrease in size of herbaceous opening, Jackson Lane and Golts Pond should be carefully monitored to determine the status of rare species populations. While monitoring of plant communities is underway at Jackson Lane, there has been no effort to monitor the rare plant populations at either site. Removal of woody vegetation from the Jackson Lane bay should be seriously considered. At the present rate of succession, this bay will be completely forested in 30 years. It is likely that the rare species would be lost much sooner as they are gradually shaded. It is likely that land use activities be yond 300m from the bays influence the flora of the bays. For example, large tax ditches may draw down water over 1000 ft from the ditch. In addition, this study of aerial photographs proved ineffective in locating ditches. Information concerning the location and time of construction of ditches should be sought from the Soil Conservation Service. If 6ossible, this information should'be mapped and included in further analyses of land use around Delmarva bays. Further analyses should explore land use up to 600m from bays and should include at least 20 bays to obtain more conclusive results., 10 Table 1. Inventory of aerial photography used to assess size of herbaceous/shrub opening. Le gend for photographic sources: AACo = Anne Arundel County Planning and Zoning Department; hMNUP Maryland Natural Heritage Program, Departmeni of Natural Resources; SCS = U.S. Soil Conservation Service; WRA C C, Water Resources Administration, Maryland Department of Natural Resources. A. COASTAL PIAIN BOGS Site Year Source Scale Gumbottom Wetiand Anne Arundel County USGS Quad: Round Bay 1943 SCS 1:20,000 1952 AACo 1:48001 1957 SCS 1:20,000 1970 AACo 1:12,0001 1984 AACo 1:24001 1985 WRA 1:12,000 Horsebridge Creek Bog Wicomico County USGS Quad: Wango 1938 SCS 1:20,000 1958 SCS 1:20,000 1985 WRA 1:12,000 North Gray's Bog Anne Arundel County USGS Quad: Gibson Island 1948 SCS 1:20,000 1952 AACo(SCS) 1:48001 1957 SCS -1:20,000 1970 AACo 1:12,0001 1984 AACo 1:24001 1985 WRA 1:12,000 Sharptown Bog Wicomico County USGS Quads: Hebron, Sharptown 1938 SCS 1:20,000 1958 SCS 1:20,000 1985 WRA 1-12000 Suitland Bog Prince George's County C, USGS Quad: Anacostia 1937 SCS 1:20,000 1957 SCS 1:20,000 1981 MNHP 1:24,000 Used to assist in interpretation of the three primary photos; area calculaiions were not based on these photos. B. DELMARVA BAYS Site Year Source Scale Black Bottom Pond Kent County USGS Quad. Millington 1936 SCS 1:20,000 1957 SCS 1:20,000 1985 WRA 1:12,000 Bridgetown Pond Caroline County USGS Quad: Goldsboro 1937 SCS 1:20,000 1958 SCS J:20,000 1985 WRA 1:12,000 Dorchester Pond Dorchester County USGS Quad: East New Market 1938 SCS 1:20,000 1958 SCS 1:20,000 1985 WRA 1:12,000 Golts Pond Kent County USGS Quad: Millington 1936 SCS 1:20,000 1957 SCS 1:20,000 1985 WRA 1:12,000 Jackson Lane Caroline County USGS Quad: Goldsboro 1937 SCS 1:20,000 1958 SCS 1:20,000 1985 WRA 1:12,000 12 TABLE 11. Area of herbaceous and/or low shrub opening in each Coastal Plain bog site for each year, reported as 0 mean + standard error of repeated measurements. Means for a site with the same superscript are not statistically different according to Students two-sample t-test values in Table IV. AREA OF OPENING (hectares) SITE MOfYR MEAN STANDARD ERROR Gumbottom Wetland 4/1943 0.527a + 0.067 8/1957 0.362b + 0.060 0.280c + 0.051 Horsebridge Creek Bog 6/1938 2.800a + 0.161 6/1958 0.497b + 0.070 9/19851 0.678c + 0.098 North Gray's Bog 12/1948 2.592a + 0.117 7/1957 2.596a + 0.158 9/1985 1.090b + 0.054 Suitlarid Bog 5/1937 4.148a + 0.155 6/1957 0.800b + 0.070 4/1981 0.257c + 0.035 Sharptown Bog Natural Herbaceous Wetland Opening 5/1938 0.491a + 0.078 7/1958 0. 176b + 0.050 9/1985 0C Opening Under Powerline Right-of-way 5/1938 0.030a + 0.028 7/1958 0.171b + 0.044 9/1985 0. 164b + 0.040 Total Opening2 5/1938 0.521 7/1958 0.347 9/1985 0.164 'The stream at this site had been channelized by 1985. The only openinog remaining is that maintained artificially for a powerline right-of-way; most of opening is probably not wettand, and thus is incapable of supporting bog vegetation. 2Total area of opening at Sharptown Bog is not a mean but rather the sum of means of two @omponent measurements; thus no standard error is given. 13 Table M. Student's two-sample t-test for comparisons of mean area of herbaceous openings between years at Coastal Plain Bogs. p, < 0.005. No asterisk indicates means are not statistically different. Site Years Compared df Common Variance t Value Gumbottorn 1943 & 1957 8 0.020, 12.89*** Wettand 1957 & 1985 8 0.016 8.25*** Horsebridge 1958 & 1985 13 0.019 -16.45*** Creek Bog 1938 & 1985 7 0.102 80.60* North Gray's 1948 & 1957 7 0.100 0.07 Bog 1948 & 1985 6 0.037 56.66*** Suitland Bog 1937 & 1957 6 0.070 67.62*** 1957 & 1981 7 0.014 59.95*** Sharptown Bog Natural Opening 1938 & 1958 t2 0.025 21.03 Powerline Opening 1938 & 19S8 7 0.008 -27.43 1958 & 1985 9 0.009 1.24 1938 & 1985 8 0.007 -28.55*** 14 TABLE IV. Percentage of historical opening remaining open, as compared to the size of the opening in the earliest year examined. SITE YEAR PROPORTION OF HISTORICAL OPENING REMAINING OPEN Gumbottom Wetland 1943 100% 1957 67% 1985 53% Horsebridge Creek Bog 1938 100% 1958 18% 1985 24%1 North Gray's Bog 1948 100% 1957 100% 1985 42% Suitland Bog 1937 100% 1957 19% 1981 6% Sharptown Bog Natural Opening 1938 100% 1958 36% 1985 0% Opening Under Powerline Right-of-way 1938 too% 1958 585% 1985 547% Total Opening 1938 100% 1958 66% 1985 31% 'Only opening remaining in 1985 was that maintained artificially for powerline right-of-way; most of opening was probably not wedand and thus would not be expected to support bog vegetation. 15 Table V. Area of herbaceous opening for Delmarva bays as calculated from aerial photos. Mean Area Variance Standard Site Name Mo[Yr X (M2) S Error (SE) Black Bottom Pond 8/36 1,054 31 13 8/57 761 36 15 9/85 766 3 1 Bridgetown Pond 10/37 4,532 83 34 5/58 3,905 52 21 8/85 4,106 64 26 Dorchester Pond 5/38 64,972 136 56 5/58 62,281 239 98 9/85 58,755 46 19 Golts Pond 10/36 6,172 102 42 8/57 4,551 99 40 9/85 3,396 83 34 Jackson Lane 10/37 11,516 96 39 5/58 5,247 88 36 9/85 3,295 32 13 Table VI. Student's t test for difference between mean area of openings of Delmarva bays. Common df=10. Years Common Significant Site Name Compared Variance T Value difference p=0.01 Bridgetown Pond 1937 & 1958 76 14.3 Yes 1958 & 1985 64 5.4 Yes 1937 & 1985 81 9.1 Yes Black Bottom Pond 1936 & 1957 37 13.7 Yes 1957 & 1985 28 0.5 No Dorchester Pond 1938 & 1958 213 21.9 Yes 1958 & 1985 188 32.0 Yes Golts Pond 1936 & 1957 110 25.5 Yes 1957 & 1985 too 20.0 Yes Jackson Lane 1937 & 1958 101 108 Yes 1958 & 1985 73 46 Yes 16 'rabic VIL Land usacTe within four intervals of distance from the herbaceous openings of five Delmarva bays. Proportion of area within each interval for each land use is identified by percent area in use within the interval. 'rhe length (m) of roads and ditches within each interval is given. BIACK BOTTOM POND Bay Edge-30m 30-60m 60-100m 100-300m 1936 1957 1985 1936 1957 1985 1936 1957 1985 1936 1957 1985 farmed --- --- --- - --- --- --- --- --- --- 11 10 14 oldfield --- --- --- 5 --- --- 9 --- --- 8 5 --- forested 100 100 too 95 100 100 91 100 too 80 85 81 powerline --- --- --- --- --- --- --- --- --- --- --- 5 roads (m) --- --- --- - --- --- --- --- --- --- --- --- ditches (m) --- --- --- - --- --- --- --- --- --- --- --- --- BRIDGETOWN POND Bay Edge-30m 30-60m 60-100m 100-300m 1937 1958 1985 1937 1958 1985 1937 1958 1985 1937 1958 1985 farmed --- --- --- --- --- --- 6 6 --- 18 15 13 oldfield --- --- --- --- --- --- 12 --- --- 18 1 --- forested too too 160 100 100 100 82 94 100 61 75 83 roads (m) --- --- --- --- --- --- --- --- --- 694 430 --- ditches (m) --- ---- --- --- --- --- --- --- --- 159 173 105 other bays --- --- --- --- --- --- --- 3 4 4 logged --- --- --- --- --- --- --- --- --- --- 4 --- DORCEMSTER POND Bay Edge-30m 30-60m 60-100m 100-300m 1938 1958 1985 1938 1958 1985 1938 1958 1985 1938 1958 1985 farmed --- --- --- 34 19 --- 29 21 2 36 22 17 logged 8 --- --- 49 --- --- 27 --- --- 17 --- --- forested 92 100 100 17 81 100 43 79 98 48 78 83 roads (m) --- --- --- --- --- 244 272 435 533 1437 1137 881 ditches (m) --- --- --- --- --- --- --- --- --- --- --- --- GOLISPOND Bay Edge-30m 30-60m 60- 1 00m 100-300m 1936 1957 1985 1936 1957 1985 1936 -1957 1985 1936 1957 1985 farmed 4 1 --- 35 30 3 40 22 3 60 45 40 oldfield 96 --- --- 51 --- --- 39 --- 15 25 5 2 forested --- 99 100 14 70 97 21 78 82 5 55 55 *roads (m) --- --- --- 26 26 --- 302 302 345 2046 2046 2472 ditches (m) --- --- --- --- --- --- --- --- --- --- --- - --- powerline (%) --- --- --- --- --- --- --- --- --- --- --- 3 *includes railroad JACKSON LANE Bay Edge-30m. 30-60rn 60-100m 100-300m 1937 1958 1985 1937 1958 1985 1937 1958 1985 1937 1958 1985 farmed 25 --- --- 58 --- --- 41 3 --- 30 5 --- oldfield --- --- --- --- --- --- --- 5 --- 7 15 --- forested 75 100 100 42 100 100' 59 92 100 63 80 96 other bays --- --- --- - --- --- --- --- --- --- 4 4 4 roads (m) --- --- --- 40 40 --- --- 40 --- 1035 412 101 ditches (m) --- --- --- --- --- --- --- --- --- --- --- --- 17 APPENDIX I. Rare species occurring at each Coastal Plain bog and Delmarva bay site studied. RARE SPECIES SUMMARY TABLE Site Name: Gumbottom.Wetland County: Anne Arundel USGS Quad: Round Bay Scientfic Name Common Name Status Carex exilis Coast Sedge Endangered Carex bullata Button Sedge Threatened Chamaedaphne calVculata Leatherleaf Threatened Platanthera ciliaris Yellow-fringed Orchid- Threatened Sarracenia Purpurea Northern Pitcher Plant Threatened Bartonia paniculata Twining Bartonia Watch List Carex atlantica Eastern Sedge Watch List' Drosera rotundifolia Round-leaved Sundew Watch List Eriophorum virginicum Tawny Cottongrass Watch List Rhynchospora alba White Beakrush Watch List Vaccinium macrocarpon Large Cranberry Watch List RARE SPECIES SUMMARY TABLE SITE NAME: Horsebridge Creek Bog COUNTY: Wicomico USGS QUAD: Wango scientific name Common name Status Sclerolepis uniflora Pink.Bog-button Endangered Sarracenia purpurea Northern Pitcher-plant Threatened Sagittaria engelmanniana Engelmann's Arrowhead Threatened Eriocaulon compressum Flattened Pipewort Rare Drosera rotundifolia Round-leaved Sundew Watch List The following additional rare species were reported from this site in the early 1980's and may persist at the site: Amphicarpum purshii Bartonia paniculata Psilocarva scirpoides Utricularia fibrosa Xyris fimbriata Xyris smalliana RARE SPECIES SUMMARY TABLE SITE NAME: North Gray's Bog COUNTY: Anne Arundel USGS QUAD: Gibson Island Scientific name Common name Status Carex exilis Coast Sedge Endangered Arundinaria gigantea Giant Cane Threatened Chamaedaphne calvculata Leatherleaf Threatened Eleocharis olivacea Green Spikerush Watch List Eriophorum virginicum Tawny Cottongrass Watch List Rhynchospora alba White Beakrush Watch List Vaccinium macrocarpon Large Cranberry Watch List RARE SPECIES SUMMARY TABLE SITE NAME: Sharptown Bog COUNTY: Wicomico USGS QUAD: Sharptown, Hebron Scientific name Common name Status Cleistes divaricata Spreading Pogonia Endangered Eleocharis robbinsii Robbins' Spikerush Endangered Fuirena pumila Smooth Fuirena Endangered PolVgala cruciata Cross-leaved Milkwort Endangered Psilocarya nitens Short-beaked Baldrush Endangered Rhynchospora glomerata Clustered Beakrush Endangered Sciryus subterminalis Water Clubrush Endangered Sclerolepis uniflora Pink Bog-button Endangered Sarracenia purpurea Northern Pitcher-plant Threatened Drosera rotundifolia Round-leaved Sundew Watch List Pogonia ophioglossoides Rose Pogonia Watch List Utricularia radiata Small Swollen Watch List Bladderwort RARE SPECIES SUMMARY TABLE SITE NAME: Suitland Bog COUNTY: Prince George's USGS QUAD: Anacostia Scientific name Common name Status Asclepias rubra Red Milkweed Endangered Polvqala cruciata Cross-leaved Milkwort Endangered Rhynchospora glomerata Clustered Beakrush Endangered Sarracenia purpurea Northern Pitcher-plant Threatened' Thelypteris simulata Bog Fern Threatened Eleocharis tortilis Twisted Spikerush State Rare Eriocaulon decangulare Ten-angled Pipewort State Rare Aronia prunifolia - Purple Chokeberry Watch List Eriorhorum virginicum Tawny Cottongrass Watch List Melanthium virainicum Virginia Bunchflower Watch Li st Pogonia ophioglossoides Rose Pogonia Watch List Quercus prinoides Dwarf Chestnut Oak Watch List Rhododendron atlanticum Dwarf Azalea Watch List Rhynchospora alba White Beakrush Watch List Senecio pauperculus Balsam Ragwort Watch List Utricularia subulata Zig-zag Bladderwort Watch List In addition, the following rare crustacean may occur here (because hybrids of this species with Stvqobromus tenuis [Watch List species] have been reported historically from "near Suitland"): .Stygobromus havi Hay's Spring Amphipod Federally Endangered 4r, RARE SPECIES SUMMARY TABLE SITE NAME: Black Bottom Pond COUNTY: Kent USGS QUAD: Millington Scientific name Common name Status Bidens discoidea Small Beggar-ticks Endangered Carex gicrantea Giant Sedge Endangered Fimbristylis ye@yusilla Harper's Fimbristylis Endangered Hottonia inflata Featherfoil Endangered Rhynchospora corniculata Short-bristled Endangered Hornedrush Oldenlandia uniflora Clustered Bluets State Rare SITE NAME: Bridgetown Pond COUNTY: Caroline USGS QUAD: Goldsboro Scientific name Common name Status Ambystoma tigrinum Eastern Tiger Salamander Endangered Hyla gratiosa Barking Treefrog Endangered Psilocarva scirpo ides Long-beaked Baldrush Endangered Carex bullata Button Sedge Threatened Sagitaria,engelmanniana Engelmann's Arrowhead Threatened' Scleria reticularis 'Reticulated Nutrush Rare Rana virgatipes Carpenter Frog In Need of Conservation Panicum hemitomon Maidencane Watch List. RARE SPECIES SUM14ARY TABLE SITE NAME: Dorchester Pond COUNTY: 'Dorchester USGS QUAD: East New Market scientific name Common name Status Eleocharis robbinsii Robbins' Spikerush Endangered i Hypericum adpressum Creeping'St. John's- Endangered wort Lachnanthes caroliniana Red-root Endangered Psilodarya scirpoides Long-beaked Baldrush Endangered Rhynchospora inundata Drowned Hornedrush Endangered xyris smalliana Small's Yelloweyed-grass Endangered Utricularia purpurea Purple Bladderwort Threatened Podilymbus podiceps Pied-bill Grebe Rare Scleria reticularis Reticulated Nutrush Rare Rana virgitipes Carpenter Frog In,Need of Conservation RARE SPECIES SUMMARY TABLE SITE NAME: Golts Pond COUNTY: Kent USGS QUAD: Millington Scientific name Common name Status Carex gigantea Giant Sedge Endangered Fimbristylis perpusilla Harper's Fimbristylis Endangered Bartonia paniculata Twining Bartonia Watch List SITE NAME: Jackson Lane COUNTY: Caroline USGS QUAD: Goldsboro @Scientific name Common name Status Fimbristylis perpusilla Dwarf Fimbristylis State Endangered; Federal Candidate (C-2) Eleocharis melanocarpa Black-fruited Endangered Spike-rush Hottonia inflata Featherfoil Endangered Panicum hemitomon Maidencane Watch List APPENDIX II. Dorchester Pond 1938 (a), 1958 (b), and 1985 (c) aerial images produced by MIPS at approximate scale 1:6000 with 1938 herbaceous opening, 60m, 100m, and 300m buffers shown in white. .. .... . ow, 'g tr- Appendix II a. Dorchester Pond 1938 aerial image. Approximate scalit 1:6000, with herbaceous opening, 60m, 100m, and 300m buffers in white. .l WRI _kR WERE ERM WE V-P., -.44 02. Appendix II b. Dorchester Pond 1958 aerial image. Approximate scale 1:6000 with herbaceous opening, 60m, 100m, and 300m buffers in white. owl* Appendix II c. Dorchester Pond-1985 aerial image. Approximate scale 1:6000 with 1938 herbaceous opening, 60P, 100m, and 300m buffers in white. NOA,A COASTAL SERVICES CTFI LIBRARY 3 6668 14111734 3