Wetland & Sub baqueous Soils NRE M 665 Coastal & Wetland Ecology & Management 1
2 Soil Drainage Classes (USDA) Well Drained = Seasonal high water table (SHWT) not w/i root zone long enough to affect yield; gray colors below 48 in. Moderately Well Drained = SHWT w/i root zone long enough to affect some crops unless drained d; gray bet. 24-4848 in. Somewhat Poorly Drained = SHWT table near surface for long enough to effect yield unless drai ned; gray bet. 12-24 in. Poorly Drained = SHWT @ or near surface for large part of year; gray @ 10 in. Very Poorly Drained = SHWT @ surface for most of year; surface horizon thick, dark gray or black
3 Root zone WD MWD SPD PD VPD Dry Wet
4 Taxonomic Moisture Regimes (USDA) Aquic: groundwater near soil surface for at least a few days of the growing season Peraquic: ground water always at or very close to soil surface during the growing season
5 Soil Color Color is a useful property for soil classification Munsell soil color syste em classifies color based on HUE, VALUE, & CHROMA
Hue: Spectral or rainbow color; 5 gradations per hue 6
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8 Value: Darkness or lightness of color; 10 = pure white All light reflected 5 = gray 0 = pure black No light reflected
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Chroma: Strength or concentration of hue 10
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Reading Soil Colors Optimal Conditions Natural light Clear, sunny day Not dawn or dusk Light at right angles Soil field moist 12
Soil Colors Matrix: predominant color Mottles: spots of color that differ from matrix Mottling occurs wheree 13
Abundance & Size of Mottles Abundance: Few: < 2% Common: 2-20% 20% Many: > 20% Size: Fine: < 5 mm Medium: 5-15 mm Coarse: > 15 mm 14
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Soil Color Chromas 2, w/ values > 4 appear gray, are characteristic of mineral hydric soils Soils dominated d by bi bright reds, browns, yellows, oranges are usu. non-hydric 16
Organic vs Mineral Soils Soil Taxonomy separates organic from mineral based on OC & clay OC (%) 12 5 0 30 Clay (%) 60 17
Hydric Soils Soils formed under conditions of saturation, flooding, ponding long enough during growing season to develop anaerobic conditions in upper part (NRCS 1998) Once hydric, always hydric 18
Development of Hydric Soils Inundation or saturation Anaerobic conditions Reducing environment Lower redox potential Chemical red duction Distinctive soil characteristics 19
Organic Soils Fibrists: fibers compose > 2/3 of mass of soils, not very decomposed (peats, Sphagnum bogs) Hemists: fibers compose 1/3 to 2/3 of mass, somewhat decomposed, (mucky peat) Saprists: fibers compose decomposed < 1/3 of mass, well- Folists: freely drained Histosols, i.e. OM filling cracks in bedrock (NOT HYDRIC); 20
Organic 21
Mineral Hydric Soils Mineral soils, when flooded for long periods, develop unique charac cteristics, called REDOXIMORPHIC FEATURES (RF) Development of RFs mediated by microbiological proces ses. Formation rate depends on: (1) anaerobic condi tions, (2) soil temperature, (3) organic matter 22
Mineral 23
Redoximorphic Features Concentrations = high chroma areas where eefe e& Mn are concentrated Depletions = high h chrom ma areas where Fe & Mn have moved out Reduced matrix = soil matrix that changes color when exposed to air 24
Identification of Hydric Soils Search NRCS Hyd di dric Soil Databases or Hydric Soils Lists Field inspection fo or hydric soil indicators (accurate); if indicator(s) present, it s hydric & vice versa 25
Indicators of Hydric Soils: All Soils Histosols: 16 in. (40 cm) or >ofupper 32 in. (80 cm) as organic material Histic Epipedon: surface ho rizons 8 in. (20 cm) or > thick of organic soil material SulfidicS Material: evolution of fhs 2 w/i 12 in. (30 cm) Layers of Muck: layers < 8 in. (20 cm) thick, must be Oa horizons 26
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Indicators of Hyd dric Soils: Sands Dark Surface: layer of black or dark gray color, w/ value=3, chroma 1. Layer below must be gray w/ value=4, chroma 2 Sandy Redox: gray layer w/ reddish colored mottles, matrix chroma 2,, mottles occ cupy > 2 % Stripped Matrix: similar to sandy redox except red mottles absent 28
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Indicators of Hydric Soils: Loams, Clays Depleted Matrix: gray layer below A horizon that may or may not have reddish mottles Redox Dark Surface: blacka horizon that contains red mottles in the form of Fe masses or pore linings UmbricU b i Surface: black layer chroma 1 6i in. thick w/ value 3 and 30
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Comparison of Mineral Organic matter <20-35% Miner ral ph usu. circumneutra al Bulk density 1-2 g/cm 3 Porosity ~45-55% Hydraulic conductivity Water holding capacity Nutrient availability high (sand, silt); low (clay) low (sand, silt); high (clay) high (cations, P); & Organic Hydric Soils low (C, N) > 20-35% Organic acidic (bogs) circumneutral (Evgs.) <0.3 03g/cm 3 >80% high high low (bogs) moderate (Evgs.) CEC low (sand, silt); high (clays) high 32
Subaque ous Soils George Demas, NRCS Noted that sediments in met definition iti of soil by: Ches. Bay 1) supporting rooted plan nt growth go 2) forming soil horizons 3) undergoing pedogenic processes 33
(Rabenhorst 2010) 34
Subaqueou us Soil Defs. Subaqueous soil: formed under continuous water column (<2.5 m), capable of supporting rooted vegetation Submerged soil: form ed in upland env., became submerged as result of water table, flooding (beaver dam), SL rise 35
Soil vs. SA Soil Formation 5 Soil Forming Factors S = ƒ (C, (Dokuchaiev 1883, Jenny 1941): O, R, P, T) 8 SA Soil Forming Facto ors (Demas & Rabenhorst 2001): Ss = ƒ (C, O, B, F, P, T, W, E) 36
Subaqueous Soil Map From Rabenhorst 37
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Uses of subaqueous soil mapping Seagrass bed restoration Pathogen residence site identification Benthic preservation site identification Wildlife management Aquaculture Management of clam, oyster, scallop production & location of new sites Acid-sulfate weathering hazard mapping Dune maintenance/replenishment Baseline condition monitoring Resource inventory Dredging considerations Habitat assessment for wading shore birds, migratory waterfowl, fisheries, & spawning grounds 40
(Stolt 2010) 41