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Macrophyte species distribution, indices of biotic integrity and sampling intensity in isolated Florida marshes
Citation:
Murray-Hudson, M., C. R. LANE, S. North, AND M. Brown. Macrophyte species distribution, indices of biotic integrity and sampling intensity in isolated Florida marshes. WETLANDS. The Society of Wetland Scientists, McLean, VA, 32(3):449-460, (2012).
Impact/Purpose:
The EPA Office of Water has recognized a critical need for states and federal agencies to be able to quantitatively assess the condition of the Nation’s wetland resources. Currently, >85% of states, tribes, and territories are lacking even rudimentary biological assessment methodologies for wetlands. Additional important needs identified include obtaining base line nutrient and physical/chemical conditions to aid in understanding the role of wetland systems (isolated wetlands in particular) in ensuring aquatic life and beneficial uses of lakes, rivers, and streams in the watershed. To address these challenges, the following research on isolated wetlands is proposed: Within a region, 1) Develop a probabilistic sampling design that stratifies isolated wetlands by type and size (also targeting reference conditions); 2) Collect biotic data using macroinvertebrates, macrophytes, and diatoms; 3) Collect abiotic (water and soil chemistry) data to establish base line conditions, quantify wetland contribution to landscape nutrient dynamics, and establish a spectral library for future rapid assessment of nutrient sequestration abilities of isolated wetlands; 4) Assess wetland condition with Level 1 (geographic information systems - GIS) and Level 2 (rapid assessment) characterization methods; 5) Develop metrics and correlate biotic signature to local and landscape assessments; 6) Report on the condition of systems across region and recommend assessment methods to states and tribes; 7) Model isolated wetland contribution to landscape nutrient dynamics based on analyses using visual and near-infrared spectrometer (VNIRS) data. Key outputs for regions and states from the proposed research include: tools for remote GIS-based assessment, tools for rapid on-site assessment, and tools for intensive biological assessment of isolated wetlands; comparison between local and landscape assessment measures; functional assessment of isolated wetland contribution to landscape nutrient dynamics (using VNIRS); baseline water and soil physical/chemical conditions; baseline flora and fauna of isolated wetland systems; and a fuller understanding of watershed condition and regional environmental health.
Description:
This study tested macrophyte condition metrics calculated after decreasing the effort and area of sampling by 33% to 66%, as tested in 74 emergent isolated wetlands. Four belted transects from wetland edge to center were established and rooted macrophytes were identified. The effort took approximately 2-3 hours per site, not including identification of unknown macrophytes. Five indicator metrics of biotic integrity were calculated: percent exotic species, percent sensitive species, percent tolerant species, mean coefficient of conservatism, and ratio of annuals to perennial species. Zonal distribution of indicator metrics was investigated using sampled presence data aggregated into three concentric zones: (1) an outer, (2) an intermediate, and (3) an inner zone, each comprising 33% of each wetland. An additional two zones were developed, an outer plus intermediate zone and an intermediate plus inner zone, each representing 66% of the sampled areas of each wetland. All zones were contrasted versus original metrics derived from the four belted transects . While a highly significant decrease in mean species richness from wetland exterior to interior was observed, there were no significant differences between metric values derived from sampling site metrics and those derived from decreasing the area by either 33% or 66%. In addition, linear correlation strength decreased between metrics derived from site data and outer, intermediate, and inner zones, respectively, for all metrics. Linear correlations between metrics from just the outer zone and site data were all R2 > 0.94 and highly significant. Thus, macrophyte-based indicators of biological integrity can be most efficiently assessed by sampling the outer third, representing a large (66%) reduction in the area and effort required to monitor isolated wetland condition.
