[MAIPC] invasives on narrow ridges on the AT in central PA

[Richard Gardner]

Heather and I have been walking the Appalachian Trail andother trails searching for American Chestnuts (@ 2900 so far).  While doing so we observed an interestingsegregation of plants by seed type.  Thenarrow ridges with steep cliff-like sides have a different assortment ofplants, native and non-native invasive than the nearby less steep sided andbroader parts of the ridges.  The seedbearing plants are in 3 distinct groups: hitchhikers, berries and windblownsamaras.  There are apparently no nutbearing trees such as oaks, walnuts and American chestnuts.

The hitchhikers appear to be mostly the non-natives garlic mustardand Japanese stilt grass with similar native plants which stick to the shoes ofhikers and animals.  Berries areapparently eaten by birds and carried up the ridges before being defecated asthey leave roosts and perches.  Thenon-natives are Japanese barberry, mile-a-minute, Russian olive, autumn olive,the bush honeysuckles (primarily L.morrowii) and some Japanese honeysuckle. The most common native is poison ivy. The windblown samaras are mostly the native maples and non-nativeTree-of-heaven.  The latter I saw atTucquan Glen in Lancaster County, PA at the top of a cliff.   My guess is that an occasional strongupdraft develops on the mountains with cliffs which blow seeds to the top ofthese ridges.

Admittedly the soils are poor, thin and often dry.  However, that does not account for all themissing plants such as oaks, hickories and similar which can be found close by onbroader parts of the ridges and the fact that all of the invaders are found in othersituations.  My thinking is that nuts aretoo heavy to be carried by the birds and mammals which normally travel throughand inhabit these narrow steep sided parts of the ridges with trails.

What really made this obvious is that yesterday as weascended the AT north from I-81 near Swatara State Park, there were AmericanChestnut trees scattered along the trail until we reached the top of the ridge.  Then there were no more trees until westarted following a creek with a gentle slope and broad valley down themountain a few miles later.  At that timewe found a small cluster within a couple hundred yards of the ridge.

What really made this obvious is that yesterday as weascended the AT north from I-81 near Swatara State Park, there were AmericanChestnut trees scattered along the trail until we reached the top of the ridge.  Then there were no more trees until westarted following a creek with a gentle slope and broad valley down themountain a few miles later.  At that timewe found a small cluster within a couple hundred yards of the ridge.

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