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Biogeochemistry-3 Biogeochem in prespective carbon

Biogeochemistry-3 Biogeochem in prespective carbon -...

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Unformatted text preview: Wetland Biogeochemistry in Perspective Carbon Linkages Among Biomass Production, Decomposition, and Vegetative Substrate Quality in Maintaining Ridge and Slough Communities, Florida Everglades (Thesis Findings Chris Lewis) Regional Extent of Ridge Slough Community 1 Ridge and Slough Vegetative Structure Ridge Slough Slough Ridge Community Characteristics Vegetation: Cladium jamaicense Soils: Organic hemic (partially decomposed) Hydrology: Depths: -15cm to +30cm Hydroperiod: <6 months Slough and Wet Prairie Community Characteristics Vegetation Slough: Nymphaea sp., Nymphoides sp., Eleocharis spp., Rhynchospora spp. Utricularia spp., Periphyton Wet Prairie: Eleocharis spp., Panicum sp., Sagittaria sp., Rhynchospora spp. Soil Organic sapric (well decomposed) Mineral (carbonate - marl) Slough Hydrology: Depth: +30cm to +75cm Hydroperiod: Inter annual exposure Wet Prairie Depth: 0 cm to +45cm Hydroperiod: 10-12 months 10- 2 What Differentiates Vegetative Communities? longer Duration of inundation - Hydroperiod shorter Slough lower Wet Prairie Ridge higher Relative elevation ? Soil Elevation determines duration of flooding, Flooding duration determines vegetative composition R S R S R What determines differences in soil elevation? Different input rates Different removal rates Hypothesized Mechanisms that Differentiate Soil Topography in Ridge from Slough Surface soil topography related to underlying bedrock topography. No correlation topographic relief derived from organic matter and marl deposition. Particulate transport out of sloughs possibly to ridges. No resolution Differences in vegetative litter production rates and decomposition rates due to litter quality. 3 Carbon Cycle in Wetlands CO2 Decomposition/leaching Decomposition/leaching CO2 CH4 Litter Microbial biomass DOC HCO3- Peat Decomposition leaching Microbial biomass DOC HCO3CH4 Decomposition/leaching Relative Biodegradability of Substrates [Aerobic] [Time - half life, days] Sugars Hemicellulose Cellulose Lignin 0.6 days 7 days 14 days 365 days Fire Hydrology Stage & flow External N&P Water level Relative elevation Dissolved and Particulate Export External Particulates Organic Decomposition Interstitial Nutrients N Temperature Water column P Light (Ca+2) (CO3-2) Algal Above and belowground primary production Marl Dissolution Stable Peat 5-20 cm - labile organic matter Active Peat, 0-5 cm - refractory organic matter - live-roots organic matter labile - mineral matter organic matter - refractory Litter - pore live-roots organic matter - space labile - mineral matter organic matter - refractory - pore live roots - space - mineral matter - pore space Compaction Ridge or Slough community within Shark River Slough Complex: Conceptual Model 4 Litter Quality and Quantity Study Objective Contrast Ridge vs. Slough Community Vegetation litter quality Carbon : Nitrogen Residual fiber content Vegetation production rates Corroborate findings using litter bag decomposition Methods Litter Quality 3A1 3A2 Seasonal harvest of representative species Quantify Tissue Carbon : Nitrogen Residual fiber ENP1 ENP2 Productivity Leaf turnover rate Area shoot density Sampled quarterly Ridge Slough Ridge 5 Harvest Slough and Wet Prairie Biomass (0.25 m2) Harvest Ridge Biomass (1 m2) Fiber Quality Analysis (Residual Fiber Method) Percent residual fiber was determined using an Ankom 200 Fiber Analyzer and determined for each Starch vegetation sample as follows: Dried and Dried and Ground Ground Vegetation Vegetation Sample Sample Hemicellulose 24 Normal 24Normal H2SO4 H SO 2 4 Digestion Digestion Neutral Neutral Detergent Detergent Fiber Fiber Digestion Digestion Acid Acid Detergent Detergent Fiber Fiber Digestion Digestion Cellulose Percent Percent Residual Residual Fiber Fiber "Lignin" Increasing Recalcitrant Fiber Content 6 Tissue Quality 120% Lignin Cellulose Hemicellulose Starches % of Plant Tissue 100% 80% 60% 40% 20% 0% Cladium Panicum Eleocharis Rhyncospera Sagitaria Periphyton Utricularia Nymphoides Nymphaea Bacopa Crinum R S Results Vegetation Litter Quality % Residual Fiber 15 Ridge Species 10 % residual = 10.4 + 4.1 % C:N = 78 + 26 5 0 120 100 80 Wet Prairie Species % residual = 4.5 + 2.5 % C:N = 42 + 28 C:N 60 40 20 0 Cladium Panicum Eleocharis Rhyncospera Sagitaria Periphyton Utricularia Nymphoides Nymphaea Bacopa Crinum Slough Species % residual = 5.0 + 8.2% C:N = 25 + 15 Ridge Wet Prairie Slough Avg. C:N: 78 Avg. Residual: 10.4% of plant tissue Biomass Quality Avg. C:N: 33 Avg. Residual: 5.0% of plant tissue R S 7 Results Vegetation Productivity (Biomass Quantity) ridge wet prairie slough 7000 6000 B io m a s s g /m 2 /y r 5000 4000 3000 2000 1000 0 3A1 3A2 ENP1 ENP2 Sampling Location Summary Results Slough Wet Prairie Biomass Production, g m-2 yr-1 Ridge 867 261 g m-2 yr-1 1734 356 g m-2 yr-1 Carbon Content, g m-2 yr-1 3255 556 g m-2 yr-1 423 92 g m-2 yr-1 723 169 g m-2 yr-1 Residual Fiber, g m-2 yr-1 1643 265 g m-2 yr-1 45.0 10 g m-2 yr-1 127 29 g m-2 yr-1 237 38 g m-2 yr-1 Corroboration Study (Litter Decomposition) Litter bags Litter from dominant species: C. jamaicense and Eleocharis spp. Litterbag cross transplant in communities Quantified Litter mass loss 8 Litter Bag Recovery Litter Decomposition Study 120 100 % Mass Remaining y = 94.922e -0.0007x 2 y = 95.755e -0.0008x R = 0.88 R2 = 0.92 80 60 40 20 0 0 100 Slough Cladium Ridge Cladium Slough Eleocharis Ridge Eleocharis y = 98.032e R2 = 0.99 -0.0018x y = 98.079e 2 R = 0.99 -0.0021x 200 Exposure Time (d) 300 400 9 Avg. C:N: 78 Avg. % residual fiber: 10.4% Total production: 3255 g/m2/yr Cladium remaining after 1 yr: 2509 g/m2/yr Long term residual: 237 g/m2/yr Soil Accretion Rates Avg. C:N: 33 Avg. % residual fiber: 5.0% Total production: 867 g/m2/yr Eleocharis remaining after 1 yr: 567 g/m2/yr Long-term residual 45 g/m2/yr R S 10 ...
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