Research Report #36 — Shawangunk Plant Species : Decreases and Increases During 100 Years
A note from Director of Conservation Science Dr. Elizabeth Long: For many years scientists and naturalists have been studying and observing the flora and fauna of the Shawangunk Ridge. Foremost among them was Daniel Smiley, for whom Mohonk Preserve’s Daniel Smiley Research Center is named. Dan wrote numerous reports summarizing his observations on various topics. This regularly occurring series will feature some of these reports; some hold tremendous scientific value today and just await an interested researcher to follow up, others showcase a quirky sense of humor or highlight an oddity of nature.
A Note from Paul C. Huth, Director of Research Emeritus:
In the late 1970’s and early 1980’s, as Daniel Smiley and I were assembling information on the flora of the Northern Shawangunk Mountains, we became aware of notable changes in some populations of both native and introduced plant species. This was made possible in large part because of Dan’s nearly lifelong field observations and resulting detailed written records, and from his gathering of local reports and documents made by family and other botanists. In this context, we were also looking into how the vegetation changed over the last 300 years or so, due mostly to the major impacts resulting from European settlement and subsequent anthropogenic causes, and how that affected species populations and distribution over time.
In this Research Report, we selected 39 native and introduced plant species that showed notable changes over time in the Shawangunk Study Area. Of the 24 species where we could see a decline, 21 of them were native and 3 were non-native. Of the 15 species where an increase could be demonstrated, only 2 were native and 13 were non-native. The breakdown by species groups was also of interest. There were 21 herbaceous species, including one fern and two grasses, 12 shrubs and vines, and 6 species of trees. As we said then, we were only presenting “possible factors that were suggested to us by the available records.” In many cases, more than one reason for a species increase or decrease was likely. Of note for readers is the fact that for some species nomenclature and familial orientation has changed in the 66 years since the reference we used then was published.
Looking at the groups, the only fern was the Ostrich Fern. Dan had documented one station in 1940, which was gone when checked in 1981. While we thought then it might be related to pH of both precipitation and related soil, it could have been related to local canopy closure and affects of droughty times.
The two grasses we selected were Orchard Grass and the Old World Reed Grass (Phragmites australis). Both are not native. Orchard Grass was planted on Mohonk Farms in the 1920’s for hay. Dan remembered it becoming common in Mohonk hayfields by the 1940’s where it was considered a problem, since it matured earlier and became “tough and woody before its companion, Timothy, was ready to be harvested”. Today, it is a wide spread and common grass.
Old World Reed Grass, or Common Reed (Phragmites australis), is the species of Phragmites we find in this area. Recent taxonomic research shows there is a native species (Phragmites americanus) which is quite “rare in the northeastern states,” and a possible hybrid between the two (Phragmites americanus X P. australis). This large introduced grass has now become very common in some of our wetland areas, like the Humpo Marsh, and once established, spreads rapidly and widely by aggressive rhizomes. It has frequently been observed appearing in wet spots after work by excavation equipment that has been moved between job sites, carrying soil, and likely both seeds and rhizome parts.
Of the 18 other herbaceous species that had detectable changes in status, 10 were native and 8 were introduced. The native species were Pink Lady-slipper, Yellow Lady-slipper, Orange Jewelweed, Yellow Jewelweed, Closed Gentian, Broad-leaved Cattail, Agueweed, White Snakeroot, Whorled Pogonia, and Pennyroyal. The introduced and naturalized species, include Knapweed (spp.), Fall Dandelion, White Sweet Clover, Bugleweed, Bird’s-foot Trefoil, Wild Madder, Vipers Bugloss, and Purple Loosestrife. Localized changes in the size of stands and populations in most of the native species can now mostly be related to changes in land use, competition from other species, canopy closure, and deer browse. Except for the native species White Snakeroot, which has showed a remarkable increase in distribution and a continuing spread into open woodlands. For some of the introduced species, like the Knapweeds, Birds-foot Trefoil, Bugleweed, Wild Madder, Purple Loosestrife, and Fall Dandelion, there is quite good documentation as to time and location of their introduction and change over time.
One species of note here is the Purple Loosestrife, which at the time of our Research Report, had increased to the point of general wetland dominance. But, we were able, over a period of less than a decade, to document the major broad decline in its overall population. It’s beginning of bloom in early July and it’s “sea of purple” peak of bloom in mid-August had been documented for decades as part of our annual phenological record, along with more than 200 other plant species, that we watch and record. In 1997, we learned that as many as four species of American-propagated Eurasian Loosestrife root weevils and leaf-feeding beetles were released into Purple Loosestrife-dominated wetlands throughout the area. Some, to local areas where we, unfortunately, had no records of release. In one the largest local wetlands, the Humpo Marsh, in August of 2006, I noted there was very little bloom on the Purple Loosestrife plants, and that most of the plants had uncharacteristic terminal tufts of leaves. On 14 August 2007, in the same wetland, where there should have been heavy bloom, I instead found the whole wetland full of dead woody Purple Loosestrife stems and only a few scattered live plants that really stood out. Since then, about 98% of the Purple Loosestrife plants have disappeared there, and other vegetation, like the Common Reed, Broad-leaved Cattail, and some native shrubs and rushes now dominate the wetland. So here, the change in population of Purple Loosestrife precipitously downward has been as a result of direct human intervention.
Of the 12 shrub and vine species, 10 are native and two are introduced. Of particular note are three of the species. One, is the Garden Red Current, an introduced species long in cultivation, and widely escaped and spread, especially from subsistence farm gardens, and as documented from the former “berry patch” planted in the Mohonk Garden. Dan noted that the currents “were probably planted about 1901.” This current’s claim to fame was that it was discovered to be the host, with other members of its genus Ribes, of another introduced species, this a rust fungus, Cronartium ribicola, which caused White Pine Blister Rust. After the rusts discovery about 1900, apparently introduced on Pine seedlings propagated in European nurseries, and the realization of its potential economic impact, major national quarantines were enacted. One, prohibiting the movement of current and gooseberries west of the Mississippi River, including an authorization for removal of all cultivated currents and gooseberries, a major loss for fruit farmers. It also required removal of wild growing plants, since the rust’s spread only comes from Ribes to pine and not from pine to pine . The effort to remove wild currents was greatly enhanced at the time of the Great Depression, when government unemployment programs like the Civilian Conservation Corps, along with individual land owners, concentrated on the task.
At Mohonk, from the 1920s to 1952, Dan Smiley “regularly eradicated currents as patches were found” in woods surrounding Mohonk. Dan noted that “between 1943 and 1952, he recorded pulling 74 plants and patches….”. A field trip with Dan to one of the slopes where he had conducted this removal, some 30 years later, found Red Current plants still persisting. Over the years, “little progress has been made in slowing the disease.” Today, planting disease resistant Ribes cultivars is recommended.
The other two species are vines are the two Bittersweets we find here, the native American Bittersweet, Celastrus scandens, and the introduced Oriental Bittersweet, Celastrus orbiculatus. Decades ago the only Bittersweet found was the native one, usually a small vine trailing over sunny farm hedgerows. In 1975, as a result of a Torrey Botanical Club field trip to Mohonk and discussion about Oriental Bittersweet spread in the area of New York City and its suburbs, we began to look at our Bittersweets more carefully. In fact, we did have the non-native one here too. It had a somewhat different growth form, being more aggressive, and commonly reaching to tree top height. Looking back in old Mohonk Garden purchase order records, we found that in fact the native one had been ordered, but we don’t know what arrived and was planted. But we can, I think, likely conclude which one it probably was. It is still a problem with orders for the native species even today. The Oriental Bittersweet is now quite widely spread around the area, and the native Bittersweet vines are far fewer and much harder to find than they used to be. The two species can sometimes be quite difficult to tell apart, except in the fall, where we have noted that the arils, enclosing the seeds, are mostly orange/red in the native species, and bright yellow in the non-native species.
Changes in some tree populations over the decades have been quite dramatic. One that in recent years has become of major importance as an invasive, and is well documented, is the Ailanthus, or Tree of Heaven, from temperate China. Unfortunately, it was imported into Europe and the United States in the 18th century as an ornamental. At Mohonk, it showed up in 1932 at two locations “beside a building and probably not planted” there. Over the years it has been found spreading aggressively along highway rights of way. Once established, mature trees produce large numbers of seeds that are spread by runoff, mowing, and earthmoving and road maintenance. For example, in February, 1982, I found cut limbs of Ailanthus with dried fruits, or samaras, still clinging dumped over a roadside bank. Passing the site just two years later, I found Ailanthus seedlings 6 feet tall! Today, they are canopy sized trees. We are concerned, as forest changes occur, related to the ongoing major loss of Hemlock, of potential interior forest Ailanthus invasion.