The Keystone Value of Places like Arlington's Hill’s Hill
Hill’s Hill is a small wooded hill in Arlington sandwiched between lower Washington St. and a Park and Rec Department soccer field. In a shadier portion at the top, black swallow-wort (BSW) took hold some years back and spread, blanketing oak and hickory seedlings and blocking access to light. The Invasives ArMI chose this site for BSW removal and eventual renewal with native replacements. We are happy to report that the previously overrun tree seedlings have survived. https://www.inaturalist.org/observations/84479644
As we've worked each week on the Hill this summer, we gradually noticed its valuable assets, delineated here: https://drive.google.com/file/d/13Se57e89x_TuL9jtBZkkVxH9XhMPibNj/view?usp=sharing
By traditional standards for measuring old growth forests —a measure of girth at chest height (DBH)— Hill’s Hill does not compare with a large forest. But then Arlington is not in the middle of Maine either. We have to value what we have.
The value of an ecosystem goes beyond the number of mature trees. It includes its future potential, and the variety of species supported right now.
Numerous tree seedlings and saplings at Hill’s Hill, such as oak ( https://www.inaturalist.org/observations/135167983 ), cherry (top 2), aspen-poplar, and hickory, contribute to its future potential. Anything growing right now has already found a nourishing spot with the right mix of sun, soil, and water. Just because it’s little doesn’t mean we shouldn’t protect it. The root systems of these naturally sprouted trees have perhaps more value than what we see above ground... it's what's going to help these trees survive during a drought like the one just experienced, whereas a planted "replacement" tree will more likely die.
High value current habitat can be measured by the numbers of species supported. Trees, being large, tend to support the most. But certain shrubs are numbered among the top Keystone plants. For example, blueberry is the only shrub genus to make it into the top 10 Trees & Shrubs (at number 7) as researched by Doug Tallamy, entomologist at University of Delaware. Keystone plants support the pollinator/caterpillar base of Arlington's ecosystem. According to this zip-code-specific National Wildlife Federation database ( https://www.nwf.org/NativePlantFinder/Plants ), the genus Vaccinium (blueberries, cranberries) hosts a whopping 282 soft-bodied caterpillars and other insect larva that birds in Arlington depend on to feed their babies.
Fortunately, there's a substantial blueberry patch at Hill's Hill protecting a down slope at the edge of the meadow from erosion. ( https://www.inaturalist.org/observations/133465271 ) We can add this asset to the sumacs anchoring the remaining meadow edge. ( https://www.inaturalist.org/observations/127432733 ) And the blackberry patch that John Eastman (Forest and Thicket) characterizes as a natural tree nursery. (https://www.inaturalist.org/observations/127433059 )
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The National Wildlife Federation explains the importance of Keystone species, and offers a general list of Keystone Native Plants in the Eastern Temperate Region.
• "Native plants have formed symbiotic relationships with native wildlife over millions of years, creates the most productive and sustainable wildlife habitat.
• "Keystone plant genera are unique to local food webs within eco-regions. Remove keystone plants and the diversity and abundance of many essential insect species, which 96% of terrestrial birds rely on for food sources, will be diminished. The ecosystem collapses in a similar way that the removal of the “key” stone in ancient Roman arch will trigger its demise."
National Wildlife Federation Keystone (NWF) dbase by zipcode: https://www.nwf.org/NativePlantFinder/Plants
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