Bob, River islands are interesting in many ways. Perhaps the forests on some of these islands are a type of sub-climax old growth. By that I mean that frequent flooding prevents the establishment of what would be considered a normal old-growth forest on the islands. Because of the flooding the tree ages are variable and of mixed ages. The species composition is different from the forests on the shore. In low islands and lower areas on higher islands the species are limited to those that are flood tolerant. Less flood tolerant species are found only in areas that are rarely flooded. Even the species that reach the island for colonization is affected by the presence of a river to cross. The forest colonizers and dominant species are those that have seeds that can easily be spread by water and survive the process. The second tier are those that can be carried to the island by birds or animals and be viable. The third and least frequent type of species present are those that must be carried by the wind a long distance, or other unusual circumstance, AND must land in a place suitable for sprouting, AND must be growing in a area where they can can survive the regular flooding.
The species distributions are therefore quite different from the adjacent shore. Along the Allegheny River they are dominated in low areas primarily by cottonwoods and silver maples. In slightly higher areas there are basswoods and hawthorns. On higher areas there are some pignut hickories and red oaks. Other trees are present only on the highest. These boundaries are not distinct and sharp for the lower areas, but essentially trees like white pine are found only on the highest islands. The thing to look for on most of these is whether or not the silvers and cottonwoods are reproducing or are they being overwhelmed by invasive plants. Here in PA the big problems are Japanese knotweed, reed canary grass, and multiflora roses. Other invasives are also a problem. The character of the trees is also different than is found in a standard forest setting. Because of the patchy nature of the tree cover and open areas on islands often flooded many of the largest trees have the characteristics of open grown specimens. You should probably swim over and check it out (before it freezes over this winter.) Ed “To the attentive eye, each moment of the year has its own beauty, and in the same field, it beholds, every hour, a picture which was never seen before, and which shall never be seen again” - Ralph Waldo Emerson ----- Original Message ----- From: [email protected] To: [email protected] Sent: Sunday, September 20, 2009 8:40 AM Subject: [ENTS] Skinner State Park Lee, I don't know if any of these images from Mount Holyoke will be of further help in illustrating patterns of land use and their impact on the forest cover, but here are 5 more images. Use them as you see fit. The visibility wasn't that good, so they aren't as clear as the images from Sugar Loaf. These images were taken from slopes and summit of 878-foot Mount Holyoke. The summit of Mount Holyoke is about 770 feet above the Connecticut River . Mount Holyoke is a few miles south of Sugar Loaf. It is the mountain you see with the white house (old inn) when traveling south from Northampton toward Holyoke on I91 or Route 5. The first image shows some of the grasses growing among the basalt outcroppings on the spine of the ridge. Image #2 looks southwest toward the Berkshires. The 3rd image looks more directly west. The island in the Connecticut River was the primary subject of interest when I took the shot. These islands do get partially flooded in the spring, but can support surprisingly mature forests of silver maple, eastern cottonwood, hackberry, red maple, etc. The 4th image shows what the forest often looks like where the terrain favors the establishment of slightly larger trees on the ridge-line where the land that isn't so vertical. However, descending from the top, the trees are never really large until the lower slopes are reached. The last image shows part of the basalt outcropping that form the charismatic little mountains. On the crest of the Holyoke Range, hemlocks, red, white, and black oaks often dominate with a significant component of black birch. Pignut and shagbark hickories, white ash, and white pine are conspicuous, but not abundant. At spots chestnut oak makes an appearance, but doesn't dominate. American beech makes establishes its presence in colonies as to be expected. One sees an occasional eastern red cedar. On the lower slopes with more soil, sugar maple makes its presence known. There is some, but not a lot of white birch. I think Larry from Hampshire College has dated northern red oaks on Mt Holyoke to around 275 years. Hemlocks have been dated to the mid to high twos. Black birch to the lower twos. Bob --~--~---------~--~----~------------~-------~--~----~ Eastern Native Tree Society http://www.nativetreesociety.org Send email to [email protected] Visit this group at http://groups.google.com/group/entstrees?hl=en To unsubscribe send email to [email protected] -~----------~----~----~----~------~----~------~--~---
