Largest outcrop • Three large trees • Tree bark young and old (A0.3)
Right behind this station marker is the largest outcrop of the underlying bedrock at Salter Grove. Designated gray metamorphosed sandstone by geologists, it was formed from sediments deposited 300 million years ago by processes discussed in Geology under Sedimentation.
The component particle size of a sedimentary rock is related to the flow rate of water over the area of deposition. Larger sediments such as small stones and gravel would settle out earlier than smaller sediments along a slowing stream of water. The deposition of sediments that eventually led to the formation of this outcrop must have occurred in a large expanse of very slow moving, if not still, water because it consists of a mass of homogenous, small particles.
The three large trees across the way (beyond the outcrop) provide deep shade in summer. Because their leaves are way up in the canopy and not always present, bark and branching characteristics help distinguish the three species.
Directly across, the tree with a bifurcated trunk is silver maple with long strappy bark. To the right is an American elm with thick spongy bark that has irregularly furrowed ridges, and limbs that continuously branch into Y's. Further south is a large black oak with thick bark marked by long, deep fissures. Its branches overhang the seasonally wet area.
The elm was a surprise. By the end of the 20th Century most American elms in North America were decimated by Dutch Elm disease, so naturally occurring trees are now quite rare throughout New England. It is thus a pleasant surprise as well as an interesting mystery as to how several reproductive individuals have survived at scattered locations in the park.
The very slender sapling (less than 1 inch in diameter) in the middle of the low lying area is a green ash. Its parent is probably the giant tree in the swale north of the parking lot.
The larger saplings (5-6 inches in diameter) between the outcrop and the three large trunks are offspring of one of the three species. Based on bark characteristics, which species is the parent?
This is an unfair question that is not possible to answer as is. Tree bark characteristics change with age. All three smaller stems have similarly smooth and light-colored bark that does not match any of the three species presented above. The trio are in fact young silver maples and were identified on the basis of leaves during the growing season.