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BOTANICAL EVALUATION OF THE GOAT ISLAND COMPLEX, NIAGARA FALLS, NEW YORK |
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CLIMATE In the present century, the moderating influence of Lakes Erie and Ontario on the length of growing season in the lowlands adjacent to these lakes in New York State, and Ontario, produces long growing seasons that are only exceeded in New York in the south-eastern counties of the state in the vicinity of New York City, under the influence of the warm currents of the Gulf Stream. At Niagara Falls the average growing season is 160 to 170 days (Zenkert, 1934), the averages decreasing in the elevated areas in the Allegheny uplands in the southwestern portion of the state. The flora of lowland areas in the extreme western border of the state along the Niagara River are contiguous with elements of the Ontario flora across the river in the Niagara Peninsula. Some floristic elements (western) may be derived from Ontario and the north shore of Lake Erie, rather than from the south along the Lake Erie shoreline. Stations of rare taxa, such as Kalm's St. John's Wort (Hypericum kalmianum) seem to suggest this, as in Ontario it is "abundant at intervals along Lake Erie from Crescent Beach to Point Abino and westward" (Zenkert, 1934), and is known from no other locality in New York State. The elevations of the Allegheny Plateau may be an adequate barrier to further incursions of western taxa into New York State from southern regions. The special habitat of exposed or shallowly buried limestone bedrock of the Niagara Escarpment at Goat Island and the Niagara River gorge further contributes to warmer, drier and alkaline microhabitats giving the competitive edge of western taxa against species more typical of the region. The climate maps for New York State used by Zenkert (1934) generalized from Mordoff (1925) tend, as a result of the class limits selected, to show the Niagara Falls area in a series of climatic transition zones or zonal boundaries for characteristics such as length of growing season (boundary between 160-170 days and 170-180 days), mean precipitation for growing season (boundary between 14 inches and under, and between 14 and 16 inches), but unambiguously within the zone of mean annual snowfall (between 60 and 80 inches - a higher rank than the 40-60 inch rate of areas to the south, east and north. The relatively high snowfall in the Niagara Falls area contrasts with the very low amount of rainfall relative to the rest of the state (14-16 inches and under), such lows only being matched in the far northeastern corner of the state. The calcareous substrates of the Niagara Escarpment, especially at ecotonal boundaries such as the crest line or areas with little or no soil over the calcareous bedrock, tend to promote dryness and warmth which might intensify the impact on vegetation of low rainfall during the long growing season of summer. More water falls (as snow) during the winter months than summer within the study area, but the cold temperatures of winter deny the usefulness of this precipitation for plant growth. Climatic conditions in the immediate vicinity of the cataracts are very complex and it is beyond the scope of this project to provide details as to its character. The prevailing winds are from the west-southwest (NREP, 1972), and so would be expected, as a rule, to come across the crest of the Horseshoe Falls from the Canadian shore across Goat Island, bearing with it the burden of vaporized water from that cataract. Wind conditions at this place appear to be complex due to updrafts of ascending vapor and air displaced by the falling water. As is the common experience of visitors to the brink of the Horseshoe Falls, Ontario, far more atmospheric moisture is borne toward the west in gusts toward the Canadian shore than is borne onto Goat Island, although one would expect the reverse to be the case. Orientation of the wooded, sedimentary escarpment overlooking the cataract area on the Canadian side may shelter the Park below it, and distort the regional orientation of incoming wind, or produce a cell of quiet, moist air next to the slope. Moisture to the Canadian bank would be favored by southerly winds pushing the spray from the Falls onto the Niagara Moraine - the escarpment of sediments overlooking the Horseshoe Falls on the Canadian side of the river. Goat Island has no corresponding protection and is fully exposed to the prevailing winds. Frequently, one can feel intermittent descending moist air on Goat Island, even as far as its eastern end, especially when the wind is strong. Atmospheric moisture is sensibly strong on Goat Island in the vicinity of the Horseshoe Falls as also is evidenced by photographs of trees indicating heavy condensation (ice), and by the current winter condition of trees in that area, and less with distance from the cataracts. Heavy condensation on surfaces is general in the plunge pool area of both cataracts as may be seen in the early photographs of ice-bridges there in winter. Without actual data, it is difficult to draw conclusions based on the premises discussed above, but the wind appears to be generally stronger on Goat Island and the shore of the American mainland near Prospect Point due to crossing the open water, than elsewhere in the vicinity. Superintendent Harries in 1911 referred to "the high winds which prevail throughout the greater part of the summer" on Goat Island and the Riverway (27 Ann Rep Comm, 1911). The numerous reports of fallen trees due to winter gales suggest this may be the case, for example, the storm of January 9, 1889 (6 Ann Rep Comm, 1890) and that of 1847 ("which washed away Gull Island, about two acres in extent," Niagara Book, 1893). The 1889 "hurricane" blew down the "Monarch of the Isle," a large Sycamore. Another storm, of January 13, 1890, occurred whose violence "caused serious damage to the Reservation, washing away soil, gravel walks, endangering bridges and blowing down thirty-six trees. On May 23, 1893, a "severe gale" toppled "twenty-five large trees on Goat Island" (10 Ann Rep Comm, 1894). A storm in 1909, with winds of seventy miles per hour, the "most violent ever recorded for April by the weather bureau," damaged many trees on the Reservation, "many fine specimens being uprooted and many others torn down ... numbers of trees were destroyed which it will take long to replace." This storm felled 248 trees on Goat Island, and ten at its base (26 Ann Rep Comm, 1910). It should be borne in mind that weather records in western New York State only began in 1871 (by the United States Army Signal Corps, International Weather Service, public service information). These winter storms did not begin when Goat Island became state property, but were characteristic of winter conditions there in the nineteenth century. Tree loss by wind-throw is probably fundamental to the extraordinary diversity of the Goat Island flora (see discussion on the central woods). Exposure to strong winds would also contribute to more air in motion for a given length of time than would ordinarily be the case on the mainland where more opportunity for wind deflection would occur. Strong wind movement is often associated with a drying effect that is stressful to organisms. Air will continue to take up water molecules until equilibrium is reached with the source of moisture - even if that source is a plant or animal and water loss becomes life-threatening. Air is constantly in motion, generally due to rising when it gets warm. Warm air is more effective at holding moisture as well, so warm moist air ascends, and cooler, dry air takes its place. Moving air, then, typically tends to extract moisture from sources of water on the ground. Ordinarily, there should be more stress of desiccation in the Goat Island flora due to exposure to moving air (wind). Air, then, is an important vehicle for the distribution of atmospheric moisture, especially when turbulent, as an inducement to evaporation, and also in a mechanical sense. If there is a nearby source of abundant water mechanically reduced to droplets with a mechanism for bearing the droplets aloft, moving air could become abundantly charged with water and then distribute it in the direction of its movement. Far from desiccating, it would enrich the surfaces with which it comes in contact, providing a humid regime typical of still air but in a high energy environment. Not very many opportunities for such interactions occur in nature. They are rare as much as sources of air-borne moisture from cataracts is rare, and produce rare biological responses, such as an enhancement of species abundance. An abundance of water droplets is generated by the fall of water over the brinks at the Horseshoe and American Falls, and also along the fifty-foot descent of rapids or cascades within a mile upriver of the crest line. Originally, the water of these rapids "begins to rush with such a fearful velocity that in many places it turns as white as the strongest rapids, and shoots up into the air" (Kalm, 1770). The plume generated by the cataracts is famous, "we saw the vapor of the Falls rising high toward the sky like a thick cloud, and this could could be seen during our whole journey, gradually increasing in size as we approached the falls" (Kalm, 1770). "A large mass of vapors rise from the bottom of the falls that resemble a thick smoke rising high toward the sky. Caused by the violence of water contact these vapors [sic], if the weather is calm, rise straight up to a great height and look like the heaviest cloud. But if there is a wind they are blown about as in a driving storm, and anybody enveloped by them will get as wet as if he had been dragged out of the sea. A couple of the Frenchmen who accompanied me climbed down a short distance below the falls, to examine the spot. The wind drove the mist at them so turbulently that they stood as in an impenetrable fog and thought they would suffocate. They left at once, and when they came up they were so drenched they were forced to take off almost all their clothes and dry them in the sun ..." (Kalm, 1770). Goat Island is situated in the midst of this high energy system and exposed to the prevailing winds. Temperate areas of the world on the western margins of continents experiencing high rainfall - most spectacularly developed in the Olympic Peninsula in Washington state - are called "oceanic" areas, and lush vegetative growth is characteristic. The ecological optima provided in part by the perpetual mist or spray from the cataracts mimicked oceanic qualities in the early flora. Abundance of atmospheric water contributed to other biological effects also: "Two foliose species collected in the 1870's, Anaptychia setifera Raes. and Teloschistes chrysophthalmus (L.) Th. Fr., are recorded otherwise in New York only from Long Island, perhaps attesting to the originally very "oceanic" character of the immediate falls area" (Harris in adjoining report, lichen section). The spray from the cataracts is of a generally constant occurrence at the falls, the air growing less saturated with distance from the cataract. In summer the spray cools the area by providing moisture for evaporation, relieving the associated vegetation from the effects of drought in the region (Olmsted in Gardner, 1880). It is to the cooling effects of the mist that Zenkert (1934) partly attributed the presence of boreal species such as Paper Birch (Betula papyrifera) and Arbor Vitae (Thuja occidentalis) on Goat Island and the Niagara Gorge. Springs of cool water, such as existed on Goat Island's shaded north side may have supported populations of plants which find it more congenial in the cooler areas north of the Niagara Frontier Region. When the Reservation was first established the Commissioners lamented that the asphalted roads, "the driveways and paths are exposed, not only to the rain, but to the constantly falling spray which settles upon them, so that during a large part of the year [my emphasis] the passage of vehicles is impeded, and walking is most disagreeable,' (7 Ann Rep Comm, 1891). In the 6th report, 1890, "after rain the road through the woods on Goat Island is very heavy, and being shaded dries slowly." "Portions of the roads on Goat Island are so thickly shaded by the primitive forest that mud remains upon them, deep and black, long after the rain has ceased, to the obstruction of vehicles and the discomfort of visitors" (6 Ann Rep Comm, 1890). The roads are "exposed at certain points to the spray from the falls which, settling upon them, keeps them drenched for days and even weeks" (8 Ann Rep Comm, 1892). Of course, with draining or run-off blockage, the hydrology changed. In 1890 a gutter was established on the south side of Goat Island and "tile placed at intervals to carry off the surface water" (7 Ann Rep Comm, 1891). Again, the "evaporation of the rain and spray so hindered by the shade of the trees along the roads" frustrated road maintenance. Oceanic conditions may have deteriorated by a rate of fifty to seventy-five percent corresponding to the loss of available water in the river as a whole through diversion of similar percentages of the river volume. As the prevailing winds are from the west, southwest, the spray relative to Goat Island would derive from the Horseshoe Falls, more than the American. Since more water has been diverted from the Horseshoe to the American Falls, this additional decrease in the amount of atmospheric water available to Goat Island must be taken into consideration. Dense tree cover, inhibiting evaporation by insulation from the wind and heat stress from sunlight kept things wet. The dense forest and thickets received the burden of air-borne water (spray) and prevented to some extent, the wind carrying this moisture away. Loss of forest, perhaps never more rapid than in the past thirty-five years or so from management policies of "thinning" (Goat Island staff communication) contributes to the present more desiccating conditions. The energy to reduce masses of water to droplets or spray is proportional to the mass of falling water, the force of gravity being the engine driving this process. Some idea of the potential energy present in the pre-diversion Niagara River may be inferred from the magnitude of hydroelectric power derived from the present Sir Adam Beck and Robert Moses Power Generating Facilities downriver. Between them they generate more kilowatt-power than any hydroelectric facility in the world - and that with only half the present volume of the Niagara River in the summer months. Prior to this diversion, all of this energy was distributed in natural systems, including the ecological systems which produced the intriguing landscape written of so enthusiastically when the Niagara Reservation was established and before. Part of this energy was spent making air-borne water available to life on the river - part of it was spent eroding the bedrock lining the gorge walls. Calcareous bedrock underlies the Goat Island sediments and forms the bed of the river. It creates a micro-climate in itself by being impervious and riddled with systems of joints. Ordinarily, limestone substrates are drier and warmer than sandstone or shale-based rock because of higher run-off rates of surface water through these fractures, with little or no retention through absorption, etc. These substrates become drier, warmer quicker (Zenkert, 1934). Calcareous caprock along the top of the Niagara Gorge to Lewiston are typical, facing into the prevailing wind which increases evaporation. This substrate-related desiccation stress is modified by the presence of spray at the falls and contributes to a unique assemblage of plant species growing on "flats" areas of exposed, flat bedrock (south side of the island, etc.), periodically inundated, or in seepage, or within the spray zone (Terrapin Point). It is this copious and constant mist that generates rainbows when the light is right - so characteristic of the Falls that attempts have been made by the Porter family and others to change Goat Island to Iris Island (see Kalm, 1770, for descriptions of Niagara's rainbows and the 16 Ann Rep Comm, 1900 for use of Iris Island in the treaty ending the War of 1812). These rainbow features are characteristic of all waterfalls all over the world. The build-up of water in the vicinity of the cataracts in the form of ice in winter has already been discussed above. The effects of this ice accumulation must have contributed to a micro-climate at the falls that was unique to the region. One would expect the ice-mass would present a cooling mass in spring with a probable resulting delay in warming locally with the advance of the growing season. This delay is addressed by Frederick Law Olmsted (Gardner, 1880) "... the masses of ice, which, every winter are piled to a great height below the falls, and the great rushing body of ice-cold water from the northern lakes in the spring, prevent at the Niagara the hardship under which trees elsewhere often suffer through sudden checks to premature growth ..." due to premature warming, a consequence of keeping the environment at the falls in spring cooler longer. However, George W. Clinton, as a young man of nineteen and in the company of several distinguished naturalists, wrote in his diary that on Goat Island on May 20, 1826 "The Podophyllum peltatum [Mayapple] was in flower, and vegetation seemed to be more forward in the immediate vicinity of Niagara than at points more remote, owing probably to the continued moistness of the atmosphere. They say that they are exempt from late frosts which are so injurious to the agricultural interests of this section of the country." It is difficult to see a mechanism for the early growth conditions to which he was referring, except for the earlier dates for the last killing frost in the Erie-Ontario lowlands in general, which are as much as thirty days earlier than in the Allegheny uplands in the south-western part of the state (Zenkert, 1934). Whereas in the relatively primitive condition of the vegetation in the 1880's the wet conditions near the falls were correctly seen to favor a wild and luxurient vegetation, commented upon by Olmsted (Gardner, 1880). However, since State ownership, artificial and unnatural conditions in these areas have been present so long that the natural vegetational interactions cannot be observed and the false or erroneous conclusion, based on the performance of exposed plantings, regardless of species, is now drawn that "plant growth is inhibited by mist and ice accumulation, particularly at Prospect Point, Terrapin Point and Luna Island" (The Promontory Partnership, 1981; Otis, 1982). As discussed above, the energy of erosion within the bedrock is partly due to the degree of hydrostatic pressure from ground water flow throughout the jointed calcareous bedrock - particularly at the gorge face or brink of the falls (Krajewski & Liberty. 1981). Ground water percolates vertically through the joints and horizontally along joints in the bedding plane. Jointing in the Lockport dolostone increases with proximity to the falls crest line, as does hydrostatic pressure and hence ground water (Krajewski & Liberty, 1981). Atmospheric moisture, such as rain, etc., probably contributes much to ground water volume, perhaps not significant in modifications in the bedrock as it is in erosion features such as slumping and landslides. Loss of volume in the river, fifty percent in summer, seventy five in winter (Bastedo, 1981), curtails much of this subsurface water pressure, hence the diminution of erosion by sapping and joint-block dislocations at the Horseshoe Falls, although perhaps initiating new sources of erosion by freeze-thawing (see section on ice above). Elements of diversion may have affected the water table on Goat Island: lowering the degree of hydrostatic pressure, reducing water in the horizontal joint systems underlying and feeding the Goat Island sediments, and lowering the level of the river itself. |