Monthly Archives: December 2019

Metal Detectors Provide Clues to Old Ways of Life in Fairfax County

 

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Figure 1: Metal Detecting and Mapping Finds at Patriot Park North Site.

There was a slave quarters at one time where Patriot Park North now sits. Fairfax County Park Authority archaeologists found some of its features the same way some beach walkers find things – with a metal detector.

During recent excavations, archaeologists identified the site where enslaved persons lived from approximately 1760 to 1820. They discovered features indicating there was a cellar, a storage pit and something else they are still trying to characterize. There were gaps where relatively few artifacts were recovered during a process called tight interval shovel testing or unit excavation. These methods generally are very effective at finding larger, domestic structures where there are substantial amounts of material left behind by the people who lived there. However, one goal of this investigation was to learn more about the built landscape, including all the man-made structures within the site and secondary structures, such as a smokehouse or corncrib. Those usually leave a relatively light archaeological signature and can be hard to find with standard practices. So out came the metal detectors.

Archaeologists have long used metal detection when working on certain sites, such as military sites. Other archaeological programs, including those at James Madison’s Montpelier, have proven that metal detection helps identify secondary structures at domestic sites. With the help of Montpelier-trained volunteers, Park Authority archaeologists went metal-detecting in two areas where little had been found. The areas were divided into 10-meter square blocks. Within each block, metal detectorists would walk rows spaced approximately two meters apart. When all the rows in a block were scanned in one direction, it would be investigated again in perpendicular rows.

Metal detector hits were marked with non-metallic flags. Each hit was then excavated, and anything found was bagged according to its location. The location of an

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Figure 2: Bagging Finds.

archaeological find is critical to learning its use, and moving a find greatly diminishes its historic value and the lessons it can teach us. When multiple finds at Patriot Park North were identified within a half-meter of each other, they were placed in the same bag. FCPA archaeologists then mapped the location of the discoveries using surveyor tools, logged the bags, and collected them for transport and analysis in the lab.

Once the metal detection finds were cataloged, archaeologists needed a meaningful way to interpret the data. They turned to a Geographic Information System project. Because they were looking for structures, they only considered nails in their analyses. They started with methods commonly used (Kriging and Inverse Distance Weighted (IDW) analyses) to create nail distribution maps. The system maps areas according to the number of artifacts found, and then it projects expected results across areas from which there are no data. Of the two methods, the IDW analysis is more visually appealing and seemingly more useful (Figure 3). However, staff immediately discovered that these tools

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Figure 3: Inverse Distance Weight (IDW) Analysis of Nails Found During Metal Detection.

didn’t answer the questions they were asking. Even lumping artifacts found within a half-meter of each other, the maximum number of nails recovered from any single location was four. FCPA archaeologists wanted to know if there were any significant clusters of nails in the area.

Onwards to another analysis, Nearest Neighbor 5 (NN5) function within the Optimized Hot Spot. This approach considers not only the number of artifacts (nails) recovered during metal detection but also the proximity of hits to each other. Using both of these factors, the analysis looks for meaningful clusters. This analysis revealed one cluster west of the storage pit features with another, less intense cluster northwest of the main cluster and, possibly, another minor cluster east of a cellar feature (Figure 4). It is possible that these clusters represent the locations of support structures.

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Figure 4: Nearest Neighbor 5 (NN5) Analysis of Nails Found During Metal Detection. (Note: The number generated by NN5 analysis reflects the strength of relationship rather than the number of finds.)

The next step will be to look at the artifacts recovered from excavations near the clusters. These data may help archaeologists pinpoint how certain structures were used. Hopefully, this will lead to better reconstruction of the cultural landscape and

Author Christopher Sperling is the Senior Archaeologist with the Fairfax County Park Authority.

The Holly and the Ivy

 

There is a time for everything, including a time for removing invasive plants. Spring and early summer are good times to remove invasives like Japanese stiltgrass and garlic mustard, before they produce seeds and die back for the year. Late fall and early winter can be convenient times of the year to remove evergreen vines like English Ivy and Wintercreeper. These vines are easily visible when other plants near them drop leaves or die back. Native plants like American holly and Christmas fern are better alternatives for evergreen foliage through the winter.

Invasive Plants

Invasive plants are not just nonnative; they are invasive because they spread out of control and disrupt ecosystems. The adaptations that allow them to spread also make them difficult to remove. They produce many seeds that persist in the soil for years, or if cut down they regrow from roots left in the ground.

The following are tips for removing English ivy and wintercreeper.

English IvyEnglish Ivy

English ivy is an invasive vine. It grows over the ground and climbs trees. The ivy weakens and kills trees by blocking tree leaves from sunlight and by harboring bacteria. Weakened trees can fall in storms from the weight of the ivy. Ivy also provides damp breeding grounds for mosquitos and dense groundcover for rodents.

To control ivy growing up trees, cut the stems of the vine around the trunk of the tree, and then cut the stems again about a foot higher or lower. The cut vines do not need to be pulled off the tree. The roots may be pulled up or cut to the ground when they regrow. Rake ivy that is growing on the ground, and cut the stems close to the ground.

WintercreeperWintercreeper

Like English ivy, wintercreeper is a vine that covers the ground and grows up trees. Its evergreen leaves cause wintercreeper to stand out in winter. Wintercreeper should be cut and pulled like English ivy.

Periwinkle and Japanese honeysuckle are semi-evergreen invasive vines that are similar in appearance to wintercreeper and may also be removed through pulling or repeated cutting.

Dispose of invasive plants in plastic bags with the regular trash. Prevent spreading invasive plants. Do not mix invasive plants with yard waste or dump it in the woods.

Native Plants

Native plants are those that have long been growing in an area without being brought there by people. Local wildlife is adapted to eating native plants. You can help expand wildlife habitat by planting native plants in your yard.

Here are some native plants that retain color in the winter.

american-holly.pngAmerican Holly

American holly has broad evergreen leaves, and the female trees bear red berries in winter. The trees are deer resistant and are a source of winter food for birds.

christmas-fern.pngWinterberry Holly

Winterberry is a deciduous native holly. While it sheds leaves in the fall, it retains red berries on its branches through the winter. The bright berries on bare branches provide visual interest and food for birds. Both American Holly and Winterberry Holly have male and female shrubs. Only female shrubs will produce berries, but a male shrub nearby is necessary for pollination.

Christmas Fern 1Christmas Fern

Christmas fern is a native, evergreen fern that can be planted as groundcover in shady areas. Its pinnae, or little leaflike segments, are shaped like holiday stockings with a long toes and small heels.

PartridgeberryPartridgeberry

Partridgeberry forms a delicate groundcover under trees. It provides winter color with evergreen leaves and red berries. White flowers bloom in summer.
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Have you removed invasive plants or planted native plants in your yard? Record your green actions on the Watch the Green Grow map at www.fairfaxcounty.gov/parks/nature-history/watch-green-grow.

Author Tami Sheiffer is the Fairfax County Park Authority’s Watch the Green Grow Coordinator.

 

Evicting the Invaders

Before

Before: Part of approximately 5,000 square feet of invasive plants on the Gerry Connolly Cross County Trail.

This picture looks like simple greenery. You may not even notice these plants as you walk your dog or jog along the trail. But untouched, these simple plants quickly become invaders. They spread rapidly and cause ecological or economic harm by degrading our natural ecosystem. They choke out the native plants in their path.

The Fairfax County Park Authority’s Invasive Management Area (IMA) Program fights these invasive plants in an effort to prevent them from taking over our parkland. The Park Authority can’t do it alone! Many hands are needed to clear a project site. IMA often partners with organizations like businesses, school groups, Scouts BSA and Girl Scouts to battle these invasive plants.

Scout Invasive Project Along Difficult Run 2Here’s one example. Every Saturday and Sunday in October 2019, Boy Scouts, Girl Scouts, Fairfax County Public School students, college students and neighborhood homeowners gathered to pull invasive plants, primarily pachysandra, from a section of the Gerry Connolly Cross County Trail off Miller Heights Road in Oakton. I am a Scout in BSA Troop 987, and I led the project with support from Hornaday Badge Advisor Sara Holtz and with sponsorship from the Invasive Management Area program.

Scout Invasive Project Along Difficult Run 1During 210 volunteer hours, 99 volunteers removed 85 bags of invasive plants from the parkland. The goal was to replace the pachysandra with native plants and trees. Volunteers planted white wood aster, hairy bush clover, American alumroot, trailing bush clover, dwarf cinquefoil, pussytoes, arrowleaf violet, common wood rush, Pennsylvania sedge, bluestem, goldenrod, arrowwood viburnum, witch hazel, hazelnut trees, ironwood trees, and redbud trees.

After

After: Invasive plants replaced with 110 native plants and trees.

I created the plan for this project in order to earn the BSA Hornaday Badge, an award created by conservationist Dr. William T. Hornaday. It is a prestigious award that requires a scout to lead a conservation project, complete several merit badges, and meet rank requirements. By successfully completing this project, I am one step closer to earning the Boy Scout Hornaday Badge, and the Gerry Connolly Cross County Trail is a step closer to being free of invasive plants.

Author Eli Edwards is a Scouts BSA Hornaday Badge candidate in BSA Troop 987.

If you’d like to volunteer on future projects, visit https://www.fairfaxcounty.gov/parks/invasive-management-area.