BOTANICAL EVALUATION OF THE GOAT ISLAND COMPLEX, NIAGARA FALLS, NEW YORK
Agassiz's "native weeds" would be pioneering, colonizing and opportunistic species taking advantage of recent disturbance, such as clearings, river margins, etc. - habitats that in the aboriginal forest were relatively uncommon. Such native "weeds" in the Goat Island complex today include shrubs such as Staghorn Sumac, and the Panicled and Red Osier Dogwoods, and many species in the Composite or Daisy family, Thistles, Goldenrods and Asters, and especially White Snakeroot (Eupatorium rugosum) on the Three Sisters. These herbs must have once been abundant on the upper end of Goat Island, which had been cleared and was undergoing stages of succession. Sumac, in fact, grew in great clonal thickets.
Goat Island's weed flora became significant with the apparent first major disturbance event in its history - the clearing of extensive portions of its eastern boundary in the eighteenth century. With every disturbance of the original ecosystem by the addition of a road, a lawn, parkage or grading throughout the two centuries by two administrations, would come increased area in which species associated with disturbance could displace native vegetation. Many exotic species from Eurasia (honeysuckles), South America (Galinsoga), west and southwestern United States (Black Locust) are opportunistic species, much as our native Asters and Goldenrods.
These kinds of plants would disappear over the years if the native ecosystem was not suppressed by intensive maintenance practices such as mowing, spreading of herbicides, soil disturbance by grading, thinning and otherwise disrupting native conditions on the islands.
Weeds do not exist in nature. This is a word representing a value judgment, even if reference is made to a "biology" of weeds in reference to their opportunistic life strategies and their place in the earliest stages of succession in an ecosystem. A weed is commonly defined as any plant growing where someone does not want it to grow. A botanist who cherishes the native flora for scientific reasons will consider exotic species as weeds, while a horticulturist, intending to impose a designed landscape over the native one will consider any plant, native or exotic, a weed if not planted intentionally. A weed is considered by agriculturists to be species in financial competition with food and other crop species for the nutrients, sunlight, space and handling of the harvest.
In terms of a historically and scientifically significant natural ecosystem such as the Goat Island flora is and has been, "weed" shall be used here to represent any species of plant inappropriately growing in the flora of the Goat Island complex, and, by extension, in the Niagara Reservation as a whole. "Appropriate" means, any species not contributing to the historic and scientific value of the property, for which it was purchased from its private owners and maintained for over a century at great expense, and for which it has been placed on the list of Historic National Landmarks by the United States Department of the Interior.
Classes of weeds in the Complex
1) Any species not native to the area of western New York and the eastern end of southern Ontario (the Niagara Frontier Region). This includes any and all exotic ornamental species.
In the past century horticultural species were added to the aboriginal flora of the Goat Island complex to beautify, or because they were available in nurseries on the mainland, or because maintenance personnel knew how to maintain them. These include the established thickets of Japanese Barberry (Berberis thunbergii) in 1909 on Luna Island and elsewhere (see species catalogue). Today, there are dense infestations of old shrub plantings - of Lilac (Syringa vulgaris) on the tops of the southern banks, of an alien species of Dogwood (Cornus sanguinea), Wayfaring Tree and Guelder Rose (Viburnum lantana and V. opulus var. opulus), and Acanthopanax cf. sieboldianus on the top of the northern slope of Goat Island. The Buckthorn (Rhamnus cathartica) and Tartarian or Eurasian Honeysuckles and Privet (Ligustrum vulgare) form extensive thickets on the island margins.
Thomas Welch, first Superintendent of the Niagara Reservation, noted non-indigenous plant taxa growing in the Goat Island forest in the 1880's: barberry, coralberry, lilac and weeping willow. These plants were either placed there by the Porters during the previous decades or they may represent escapes from the mainland areas in New York and Ontario into disturbed areas in the complex. Berberis vulgaris (Barberry) was reported on the Island by Day (1888), but the only Symphoricarpos species noted by him in the Niagara area was the native one (Coralberry is an ornamental member of this group). Lilac was considered capable of escaping into the wild, as was weeping willow. The big exotic willows seen today, White and Crack Willows and their hybrids (Salix alba and S. fragilis) are extremely old - as their ability to stabilize riverbanks and affect drainage to some extent was early recognized.
There is another aspect of the term "weed" that makes it synonymous with the term "disease." Many diseases are caused by an organism invading the body of another organism with the result that the invaded body is weakened or dies. Some of the most disastrous of these diseases are caused when a foreign organism is introduced into that of an organism which has evolved in a different region, and against which it has evolved no defense. Entire species can be wiped out with profound regional ecological consequences such as the present virtual extinction of the American Chestnut (Castanea dentata) from the Asiatic fungus Endothia parasitica, and the withering of populations of American Elm (Ulmus americana) from the fungus Cerastomella ulmi and an introduced bark-beetle Scolytus multistriatus. Both trees are important components of native American forests.
Another biological invader which has caused ecological havoc is the economic disruption of the Great Lakes fishing industry by introduction of the predatory and parasitic sea lamprey (Petromyzon marinus). It has been said that the Niagara River is not a river but a strait. More than a simple distinction, the fact that the Niagara is a strait means it has a fundamental connection between two great bodies of water - it is an avenue between them, and so serves a different biological role than a river with its land-bound source, or head. The Niagara strait connects the lake ecology of Lake Erie with that of Ontario. The hundred and sixty or so feet of the cataract at Niagara Falls had been an effective ecological barrier to certain organisms originating downstream in the Atlantic Ocean, or escaping from trans-ocean freight unloaded at Montreal or other port connections in the lower St. Lawrence Seaway (Elton, 1958). Apparently, with the navigational bypass in 1829 with the opening of the Welland Ship Canal, the lamprey proceeded into the upper lakes with the result that "in ten years after the lamprey invasion began to take effect, the numbers of lake trout (Salvelinus namaycush) taken in the American waters of Lake Huron and Lake Michigan fell from 8,600,000 lb. to only 26,000 lb." with additional depletion of burbot, suckers and lake whitefish (Elton, 1958).
Although species may be destroyed by direct attacks on their physical integrity, as in the examples cited above, another way species may be attacked is as they are out competed for the resources (sunlight, soil nutrients, moisture) on which they depend for survival, or if their young cannot become established and the species is in existence only as long as the parents survive. Normal or natural plant communities are heterogeneous associations of a diversity of plant species and other organisms and the destructive processes of competition are a natural component of these communities, which are always changing. Species rich plant communities in the Goat Island complex include those on the island margins in wet soil, the deep central forested area, limestone pavement covered with shallow patches of soil, etc. The species diversity, due to the heterogeneity of habitat on the islands, was historically, and is, quite high - the area was noted for this characteristic among botanists and those that appreciated natural environments in the nineteenth century.
Exotic organisms, however, can be introduced into a diverse plant community which are so aggressive that they out compete every other plant organism in the community, with the resulting degradation of the community structure and extirpation of species diversity within the community. Communities overrun by what may be seen as essentially disease organisms are said to present monocultures of the invading species and become ecologically barren.
The plants that the word weed implies in this case are those that tend to form monocultures: that is areas totally dominated by a species to the exclusion of the establishment of anything else. One of the advantages noxious weeds have is their ability to establish themselves before other species can. They either germinate quicker, produce more seed, keep photosynthetic leaves active throughout the winter or possess some other physiological advantage over the assemblage of species they ultimately replace.
Naturally, in high energy environments such as the cataracts at Niagara Falls and the Niagara River gorge, there is a great deal of natural disturbance by the direct energy of water, or indirectly by collapsing or spalling/sapping of the bedrock. It is this disturbance that contributed and contributes to the unusual community characteristics noted historically in these areas. Exotic monoculture species thrive on disturbance, for they establish themselves more quickly than native species that had evolved within the checks and balances provided by other species with which they had been environmentally associated for centuries or millennia.
Consequently, in the patchy, discontinuous floral assemblages throughout the gorge and the islands and river margins in the vicinity of the cataracts, there are large areas of complex native tree, shrub and herbaceous assemblages reflecting centuries of community development in place. Interspersed with these are areas composed almost totally of exotic tree species, which have seeded themselves from plantings along the urban streets along the gorge rim above: primarily Norway Maple (Acer platanoides) and, on the Canadian side by the Maid-of-the-Mist landing, Sycamore Maple (Acer pseudoplatanus). Another Maple species spreading rapidly throughout the gorge is Box Elder (also known as Manitoba Maple, Acer negundo). These species are probably so successful because their tolerances are close to that of the climax Maple for the region: Sugar Maple (Acer saccharum). There is no reason to suppose that the native maple will ever replace the exotic maples once they have dominated the areas in which they have become established.
Another serious monoculture-forming species is the shrub Tartarian Honeysuckle (Lonicera tartarica), although other species of Lonicera have also become noxious, such as Lonicera morrowii, or Morrow's Honeysuckle. The planting of Tartarian honeysuckle has had disastrous consequences in one area of the Niagara Gorge north of Whirlpool State Park where picnic tables and stairs have been built. It was probably planted there decades ago. Species diversity here has dropped substantially, compared to similar areas above and below this station.
Ours is not the only area under siege by these species. Symptoms of deterioration of Illinois prairie lands are indicated by "infestations of European Buckthorn (Rhamnus catharticus) Tartarian honeysuckle (Lonicera tartartica) and garlic mustard (Alliaria officinalis). These aliens create thickets so dense, green up so early in spring, and hang on so late in fall, that they often drive out everything else. An especially sad (and common) landscape features forlorn, aristocratic old oaks in an unbroken sea of buckthorn - the understory kept so dark by the dense, alien shrubbery that not one young oak, not one spring trillium, not one native grass can be found ...." "In some places you can explore the preserves only by crawling for long stretches on bare dirt under the dead, thorny lower branches of buckthorn." In the Illinois area just mentioned, controlled burns killed "most of the buckthorn and Tartarian honeysuckle" (Packard, 1988).
For example, along the gorge crest is a scientifically and historically interesting suite of species. A Lonicera-dominated monoculture is what is replacing this community. Some examples of species existing and known from the crest habitat and which cannot compete with the Honeysuckle are given below.
A second component of the definition of weed used here, then, is:
2) Any exotic species tending to form a monoculture in the plant community in which it has become established.
The second major disturbance regime on Goat Island, other than the one produced by the river, is generated by intensive maintenance practices where the natural order of plant succession and spontaneous species establishment is suppressed by activities such as mowing, weeding, the application of herbicides and sowing of purchased seed. Such practices favor permanent weed populations and artificial monocultures of a few species of grass bearing no relationship to the native ecosystem.
In Woodland communities, the herbaceous crucifer Garlic Mustard (Alliaria officinalis) overwhelms the complex spring ephemeral assemblages and persists to compete with subsequently emerging native woodland species. In a "Natural Regeneration" area maintained by the park on the Canadian side, this early, quick growing weed may be seen to overtop Jack-in-the-Pulpit (Arisaema triphyllum), Trillium (Trillium spp.), Toothwort (Dentaria laciniata), the False Solomon's Seal (Smilacina spp.), Adder's Tongue (Erythronium spp.). Since Garlic Mustard is non-mycorrhizal, and plants of the lily family, which dominate the spring flora, are richly mycorrhizal, not only is the diversity of the conspicuous subaerial flora threatened by this plant, but there may exist a serious threat to the integrity of the microscopic soil flora which contributes to the vigor and success of the entire plant community.
In the same Canadian woodland noted above, one entire sector of the regenerating woods was composed of Celandine (Chelidonium majus) in the herb layer. Although Celandine has not yet been established on Goat Island, it does occur on the adjacent mainland on a wooded slope continually stripped of its native vine cover - another reason the development of vines should not be suppressed.
On the woods borders and areas where thickets are developing several shrubs, including Tartarian Honeysuckle, the following species were established and are continuing to increase their area: Buckthorn (Rhamnus cathartica), Wayfaring Tree (Viburnum lantana) and Privet (Ligustrum vulgare). Some of these, such as Lilac (Syringa vulgaris), have spread clonally. Another species to watch is Acanthopanax (Acanthopanax sieboldiana). None of these invasive species has any relevance to the historical and scientific value of the Niagara Reservation, and their presence in fact degrades that value.
The recent establishment of Daffodil (Narcissus pseudo-narcissus) on Goat Island has caused the escape of this plant into the central woods where its conspicuous presence conflicts with the appearance of the native wildflower flora there. Care must be taken that Star-of-Bethlehem (Ornithogallum umbellatum or O. nutans) which has been established and is spreading vigorously on the mainland in an old homestead by the bridge to Goat Island not be introduced into the Goat Island flora.
In must also be born in mind that a process of climatic warming has been developing since the weather began to be monitored in the latter half of the nineteenth century. Since one of the principal reasons species are limited in their range is due to seasonal temperature restrictions on some aspect of their physiology, it stands to reason than certain species marginally intolerant of the length of growing season or the extent of frost typical of our area would not be able to reproduce themselves here, although individuals, once horticulturally established, survive the winter season and attain great maturity. These species might produce viable seed each year, but these cannot germinate because of unsuitable temperature regimes. As climate ameliorates, as it appears to have been doing throughout the twentieth century, there will probably come critical climatic moments when various species will be able to establish themselves without intervention. A blanket of seeds, once shed and resident in the seed bank, and previously without an instance of germination due to climatic suppression, germinate when amelioration reaches a stage where germination becomes possible. A succession of ensuing warmer years, or warmth plus additional moisture or dryness or some such meteorological combination would ensure the survival of the seedlings. With apparent suddenness, a species once unknown to have established surviving offspring appears to have "exploded" into the flora.
The problem with planting exotics which do not appear to be spreading, such as Honey Locust (Gleditsia triacanthos) and Catalpa (Catalpa bignonioides) is that they do produce seeds in quantity every year. Presumably their seeds do not set for climatic reasons. No evidence for their spread into the flora has appeared until recently. In the Niagara River gorge both Black Locust (Robinia pseudoacacia) and both of the species just named have been found to have established themselves in the basal forest of the gorge. Young Black Locust seedlings and saplings have been recently found on the flats area on the south side of Goat Island. The interesting thing is that the members of all these species appear to have become established only within the past several decades, as though a triggering mechanism existed and their germination has been "desuppressed." Such exotics may become overwhelming elements in the native flora as climate continues to warm, as is evident of other tree introductions, such as the Bird Cherry (Prunus avium), whose crowns, white with flowers in the spring, may be seen the length of the gorge forest, White Mulberry (Morus alba), and the Maples mentioned above. Tree ring studies of these species correlated with records of their horticultural establishment might reveal the historic decade or so when they became fully functioning members of the flora of the vicinity of Niagara Falls.
Any exotic shrub planted in the gorge area, including the islands and river margins, might become able to set seed and become noxious over time if allowed to exist adjacent to native ecosystems.
In the wet habitats on the island margins, the complex community of native species is threatened by Purple Loosestrife (Lythrum salicaria) which can severely disrupt wetland communities. Giant Hogweed (Heracleum mantegazzianum) produces dense thickets, as can be seen upriver at Buckhorn Island State Park, has established itself in two places on the islands.
Another refinement to the definition of weed used here would include:
3) Exotic species associated with the urban landscape: Chickweed (Cerastium spp.), Ox-eye Daisy (Chrysanthemum leucanthemum), Dandelion (Taraxacum officinale), Burdock (Arctium lappa, A. minor), Bitter Nightshade (Solanum dulcamara), Chickory (Cichorium intybus), Queen-anne's Lace (Daucus carota).
The above species confine themselves mostly to the margins of disturbed areas such as lawns, gardens, asphalt roads and paths. Where there is a congestion of these maintained areas, such as at the west end of the island, unless actively removed, and in the Three Sisters where native communities interact with small patches of lawn along asphalt paths, these urban weeds are most conspicuous. According to the experience of the present writer, most visitors dislike seeing these species in what they had expected to be a natural setting. These plants are what ordinary people, who confine themselves to tending their personal lawns, consider to be true weeds. They remind the visitor of carelessness and neglect.
Native weeds which benefit from disturbance and do tend to form monocultures to some extent, but which is appropriate within certain limits include Staghorn Sumac (Rhus typhina), note the references to its behavior in the eastern meadow before modified (see species catalogue); Slippery Elm (Ulmus rubra); Common Milkweed (Asclepias syriaca); White Snakeroot (Eupatorium rugosum); Canadian Goldenrod (Solidago canadensis); New England Aster (Aster novae-angliae); Starved Aster and Calico Aster (A. simplex and A. lateriflorus), and various thistles (Cirsium species).
Not all exotic species that have established themselves in the complex are to be considered weeds. These in themselves have scientific value: they are rare in the area (Cerastium semidecandrum, Poa chapmaniana, Sagina procumbens, Tripsacum dactyloides, etc.), or have cultural and historic value in themselves, such as the "rock garden" types of minute plants, some of which can be demonstrated to have been introduced a century ago, mostly in conjunction with activities by David F. Day. These species include Whitlow Grass (Draba verna), Small-flowered Crane's-bill (Geranium pusillum) and a tiny Buttercup found in the course of the present study and which cannot as yet be identified, but may be a Eurasian-Himalayan species new to the flora of New York State.
Inconspicuous, non-invasive but persistent species of both introduced and "spontaneous" establishment have scientific or biological value either in themselves because they are interesting, or because their presence as rare species in the wild distinguishes the Goat Island flora from typical floras in the region. They also reveal areas of biological importance in the complex, as they tend to cluster at habitat boundaries and other localized areas. The fact that they occur in the same general areas as the most rare native species sheds interesting light on the distribution of rare plants in general.
One species of grass which has not been reported before for the Niagara Frontier Region, Poa nemoralis, may reveal historic landscaping practices no longer in use (see species catalogue). Although, with the sudden rise in interest in historic gardens and landscapes, old garden lists of the eighteenth and nineteenth centuries have been investigated (Leighton, 1987), there has been little exploration of graminoid species used in the history of lawn-making. Lawns, although present everywhere, have received little biological attention by urban ecologists and landscape historians, although they support numerous plant species peculiar to lawns alone - primarily species growing below the height of mowing blades: on Goat Island including English Daisy (Bellis perennis), Purslane (Portulaca oleraceus), Common Knotweed (Polygonum aviculare), at the lawn margins Homeless Knotweed (Polygonum achoreum), various species of Clover (Trifolium spp.) and Veronica (Veronica spp.) and so forth.