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IV. DISCUSSION |
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The Morton Centre property is a complex area affected by many factors, as illustrated by the results of this study. Data collected has been extremely valuable in preparing a preliminary evaluation of the state of the property. Overall the property appears to be in good health, ecologically, with a few exceptions. |
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Using GPS units to map boundaries resulted in the identification of several important areas. The first two areas are known to be ecologically important: the saltmarsh and the bog. Although not rigorously sampled, other examples of in our region have shown bogs to be areas of high biological diversity. Similarly, saltmarshes in Nova Scotia are known to be areas of high productivity as well as nursery areas for juvenile fish sspecies. As such, these areas must be protected. |
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GPS boundary mapping also revealed a large area of concern, the two significant forest windfalls (Area E in Figure 3.11). The windfalls constitute a significant portion of the forest that may be indicative of problems with adjacent land-use coupled with previous land-use history. An examination of previous air photos of the property (Figure 4.1) illustrates that large portions of the area were logged. Two large areas were left untouched, however, located on the high point of topography along the westernmost drumlin axis (Area A in Figure 4.1). In 2000, a commercial cranberry bog was constructed adjacent to the property, including the excavation of a large irrigation pond. It is probable that a synergistic effect occurred with that construction. Due to the formation of a high permeability void, water was pulled from the headlands surrounding the bog. The water table was subsequently most affected at the highest relative elevations. As such, mature stands of trees approaching natural senescence were subjected to increased stress with decreasing water supply. With shallow rooting tree species, the effect could be quite devastating and result in the windfall areas described. |
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Figure 4.1: Aerial photos depicting land-use history over five decades at the Morton Centre property |
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Other than the large windfall areas, the forest appears to be in good health. The species list developed for the property shows an abundance of flora. There appears to be sufficient vegetation along the coast to help anchor soils and slow erosion rates. Some trepidation does exist, however, concerning adjacent land use. Cottage construction has accelerated on the west side of the island in particular, with on house being constructed along the south-western portion of the property line. A large area of land along the property line has been deforested, with a large drainage ditch and seawall being constructed. Already some effect appears to be evident. |
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The deforested area now exposes trees to prevalent winds, causing windfall on the Morton Centre property line. Without these trees to anchor soil, erosion rates will most likely increase, exasperated by relief. Though normally seawalls redirect wave energy to the adjacent shoreline, this cottage appears to be built in an area of transportational coast. |
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No threatened or endangered floral species were identified in the floral survey. It should be noted, however, that at least two large patches of Cypripedium acaule Aiton (pink lady's slipper) were found. Although this species is not threatened, it is susceptible to disturbance and these areas should be avoided. |
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A concern does exist regarding a deficiency in terms of measured biodiversity. Although tree diversity is well documented, forest floor vegetation has been identified, but not quantified. Further studies are needed to better illustrate patterns of all flora, not just trees. In addition, there are several tree species with very few observed individuals. Eastern hemlock (Tsuga canadensis Carr.) for example appeared to be infrequent on the property. In depth distribution studies should be completed for species that appear to be infrequent. |
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The last area of concern in the forest is Area A in Figure 3.11. This are appears to be an important area of water recharge. As discussed previously, there is a propensity for overland flow to occur due to the low hydraulic conductivity. Water pools in this recharge area and whatever water does not evaporate slowly infiltrates through the soil and into the perched water table. This area must be left relatively undisturbed so as not to disrupt the natural hydrological cycle of the property. Although probably not susceptible to foot traffic, the area is not suitable for any larger scale developments in terms of structures. |
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Other important concerns exist regarding water supply in terms of development. Examining water chemistry revealed water from the perched aquifer met most standards of the Canadian Drinking Water Guidelines. It is not quality that is the issue with this source of water, but the overall supply. As discussed earlier, the recharge of the till becomes a significant problem due to the low hydraulic conductivity of the aquifer. Therefore, if water is removed in significant volumes, recharge will not be rapid enough to meet demand and the water table will be significantly lowered. |
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Similarly, water from the bedrock aquifer met most standards stated in the Canadian Drinking Water Guidelines. Although hydraulic conductivity values have not been calculated for the Halifax slates, a potential problem may exist associated with excessive water removal in the form of saltwater intrusion. Previous work (Morse, 1999) has suggested that excessive withdrawal from wells may initiate lateral and vertical saltwater intrusion (Figure 4.2). The closer the well is to the coastline, the greater the potential problem of saltwater intrusion becomes. |
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Figure 4.2: Schematic of Morton Centre water table with possible scenario of salt water intrusion (modified from Morse, 1999) |
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Again, a synergistic and cumulative effect is probable. With cottage development on the western side of the island increasing water use, the problem of drawdown in the bedrock aquifer is increased and salt water intrusion is exasperated. In addition if the potentiometric surface is lowered significantly, the aquifer skeleton could collapse and result in land subsidence. In order to avoid this possibility, detailed information must be collected about the bedrock aquifer before any plan is in place. |
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Water usage brings into focus the issue of human waste disposal. Since 1997, the septic system has not been stressed; the maximum number of occupants has been 4 for 4 months at a time. If the property is to see an increase in the number of occupants, a sustainability plan in terms of water resources must be in place. To accomplish this plan, however, detailed information must be collected about the yield of the aquifer. In addition, data must be collected concerning the water usage per person and then the projected water use can be modeled for specific projects. |
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