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Does National Wetland Inventory class consistently identify vegetation and edaphic differences in Oregon tidal wetlands?
Citation:
Janousek, C. AND C. Folger. Does National Wetland Inventory class consistently identify vegetation and edaphic differences in Oregon tidal wetlands? Wetlands Ecology and Management. Springer Science and Business Media B.V;Formerly Kluwer Academic Publishers B.V., , Germany, 26(3):315-329, (2018).
Impact/Purpose:
National habitat classifications systems are valuable tools for mapping and analyzing coastal wetlands, but it is unclear if they convey accurate and consistent information about the biological and environmental structure of coastal wetlands. We used data from tidal marshes in four Oregon estuaries to assess the degree to which National Wetlands Inventory (NWI) habitat classes accurately describe differences in vegetation and soil properties in the Pacific Northwest. Our findings suggest mixed accuracy for NWI marsh habitat classes. NWI classes had clearly differing soil salinities and fairly well-described differences in soil carbon and nitrogen pools and the abundance of common marsh plant species. However, tidal elevation, soil texture, plant composition and plant diversity were less well differentiated among marsh classes. High marsh had the largest species pools. Non-indigenous (NIS) plant species cover was highest in palustrine and high marshes. Common plant assemblages sampled in the survey differed in elevation, soil salinity, other edaphic variables, plant richness, and NIS cover, suggesting they may be a better indicator of wetland structure and function than the NWI habitat classification used in the region. .
Description:
Accurately mapping, modeling, and managing the diversity of wetlands present in estuaries often relies on habitat classification systems that consistently identify differences in biotic structure or other ecosystem characteristics between classes. We used field data from four Oregon estuaries to test for differences in vegetation structure and edaphic characteristics among three tidal emergent marsh classes derived from National Wetlands Inventory (NWI) data: low marsh, high marsh, and palustrine tidal marsh. Independently of NWI class, we also evaluated the number and types of plant assemblages present and how edaphic variables, non-native plant cover, and plant species richness varied among them. Pore water salinity varied most strongly across marsh classes, with sediment carbon and nitrogen content, grain size and marsh surface elevation showing smaller differences. Cover of common vascular plant species differed between marsh classes and overall vegetation composition was somewhat distinct among marsh types. High marsh had the largest species pools. However, plot-level plant diversity was similar among marsh classes. Non-native species cover was highest in palustrine and high marshes. The marshes in the study contained a large number of plant assemblages with most occurring across more than one marsh class. The more common assemblages occurred along a continuum of tidal elevation, soil salinity, and edaphic characteristics, with varying plant richness and non-native cover. Our data suggest that NWI classes are useful for differentiating several general features of Oregon tidal marsh structure, but that more detailed information on plant assemblages found within those wetland classes would allow more precise characterization of additional wetland features such as edaphic conditions and plant diversity.
