Spatial contingency in restoration targets - suppose where an ecosystem is affects how it can perform?
Findlay, Stuart*,1, Arrigoni, Alicia2, Nieder, William3, Tockner, Klement2, 1 Institute of Ecosystem Studies, Millbrook, NY2 EAWAG/ETH, Dubendorf, Switzerland3 HRNERR, Annandale, NY
ABSTRACT- One of the major steps in restoration planning is quantification of targets and subsequent measurement of success. In general, controls on performance of a reference or restored site are only considered in the small scale without consideration of whether factors operating at larger spatial scales might influence the capability of specific sites. For two types of aquatic habitats in the Hudson River (submersed aquatic vegetation and tidal wetlands) we see evidence that neighborhood and larger spatial contingencies affect functional performance. For instance, the capacity of a SAV bed to ameliorate poor water clarity is weakly related to patch size but also affected by the proximity to deeper water areas presumably due to greater potential for sediment resuspension events. Tidal wetlands in the Hudson show a general capability to improve water quality by removing nitrate from tidal waters and the performance of individual sites is not predictable by local site characteristics. The capability of these wetlands to remove suspended sediments from inwelling water masses is largely dependent on sediment loads in flooding waters rather than patch-scale characteristics. Restoration planning can benefit from information on local or larger scale control on performance in at least two ways. In opportunistic restoration where a potential site is pre-determined, understanding constraints on performance will help set achievable targets. In whole-system restoration planning, sites could be selected where the combination of local and larger scale factors will lead to maximal performance. For instance, any plans to restore SAV beds in the Hudson should dictate a minimum setback from deeper water to allow maximum opportunity for good light penetration at the restoration site. If sites are constrained to be near deeper water, target values for plant cover should be reduced to amounts known to occur at such sites.
Key words: restoration, tidal wetland, submersed vegetation
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