Wetland & Estuarine Formation & Development NREM 665

Transcription

1 Wetland & Estuarine Formation & Development NREM 665 1

2 I. Wetland Formation & Development A. Favorable climate (PPT > ET), temperature 1. don t get WTLs in B. Favorable geol/substrate 1. high H 2 O holding capacity & C. Hydrologic factors & WTL dvpt 1. H 2 O source effects what types of WTL dvp 2

3 General model of hydrologic inputs which control wetland development 3

4 II. Estuary Formation A. Estuary Def: semi-enclosed coastal body of H 2 O which is connected w/ open sea & in which SW diluted d w/ FW derived d from land drainage (Pritchard 1967) 4

5 B. 2 Main Physical Processes in Estuaries 1. Stratification (Layering): FW lighter than SW a. tides & winds mix layers 2. Settling: Rivers bring susp. sediment to estuary a. Aggregation/flocculation as FW hits SW 5

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7 C. Estuary Formation: 5 Main patterns based on geomorphology (Day et al. 1989, Mann 2000) 1. Drowned river valleys (or coastal plain estuaries) a. SW progressively extends into river valleys w/ SL rise i. SL rise occ in most places since last glaciations b. Common in temperate climates w/ TSMs c. Broad vs narrow dep on size of cont shelf d. Classic example? 7

8 Estuary formation via river valley drowning 8

9 Drowned river valley or coastal plain estuary Chesapeake and Delaware bays 9

10 2. Fjords formed by glacial erosion a. form in river valley scoured by Pleistocene glaciers b. U-shaped, typically very deep i. Ex: c. little sediment, dom by plankton, temperate climates 10

11 Fjord Gulf of St. Lawrence 11

12 Fjord Puget Sound 12

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14 3. Bar Built a. Form where deposition of sediment kept pace w/ rising SL, creating spits or barrier islands b. Common in subtrops & trops, dom by TSM & MGs 14

15 Bar built estuary Laguna de Terminos, Campeche, Mexico 15

16 4. Tectonic a. coastal indentations formed by faulting or subsidence b. What is the classic example?? 16

17 Tectonic estuary San Francisco Bay, California Bay&title=&imgType=1993&Map =1&dev=0 17

18 5. Deltaic (land deposition) a. produced by river processes b. characterized by silty sediments from terrestrial runoff (Day et al. 1989) c. 3 types: fluvial, tide-dominated, & wave dominated 18

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20 Fluvial deltaic estuary Mississippi River delta, LA 20

21 Atchafalaya delta Fluvial deltaic estuary 21

22 Mississippi Ouflow 22

23 Tide-dominated d i d deltaic estuary 23

24 Wave-dominated deltaic estuary Sao Francisco delta, Brazil 24

25 Wave-dominated deltaic estuary Chilean Coast ygg y 20Class/Sedstrat6/slideshow_6_12.htm 25

26 D. Estuarine Mixing Classification 1. Salt wedge (stratified): minimal mixing bet FW & SW a. moves up & down seasonally, Q: Classic ex? 2. Partially-mixed: more vertical mixing & resuspension via winds & tides 3. Well-mixed (Vertically homogeneous/fully-mixed): strong mixing forces break down stratification 26

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28 III. WTL Dvpt & Succession A. Auto vs. Allo 1. Autogenic: linear succession from shallow lake to climax forest 2. Allogenic: plant community ing in resp to ing env. no climax, nonlinear 3. WTLs are ecotones bet. aquatic & terr envs., w/ allogenic forcing from both dirs 28

29 Early wetland succession models: Presumed linear trajectory among plant communities in England (Chapman 1960) 29

30 Gulf Coast wetland succession models: linearity & climax (Penfound & Hathaway 1938) 30

31 More recent wetland successional models Successional sequence from stratigraphic & paleoecological data in British peatlands (Walker 1970). Thicker lines = more common transitions. 31

32 IV. Models of Wetland Development A. Functional Guild 1. describes comm. in terms of functional groups defined by specific traits a. enables prediction of guilds based on various env. conds. ~ assembly rules 32

33 Functional Guild 33

34 B. Env. Sieve 1. pres & abun of spp ƒ(life history & adaption to env. conds.) a. env. conds = sieve, as env. s, so does sieve, & spp. present b. 34

35 Environmental Sieve 35

36 C. Centrifugal Org. 1. describes plant comms. along gradients of env. constraints a. gradients radiate outward from single core habitat to periphery p where spp. adapted to constraint(s) outcompete core spp. 36

37 Centrifugal Organization 37

38 V. WTL as hybrids bet young & mature systems A. Young Systems 1. high prim prod. (as in most immature systems) s) 2. open mineral cycling 3. short life cycles 38

39 B. Mature Systems 1. High detrital processing (nutrient demand satisfied by recycling even in open TSMs, MG) 2. Spatial heterogeneity 3. Complex life cycles 39

40 Mature: Spatial Heterogeneity Aerial view of Everglades tree islands & Cladium (sawgrass) 40

41 Mature: Spatial Heterogeneity 41 Ground view of tree islands and slough in the Everglades

42 Mature: Complex Food Webs 42

43 VI. Pulse Stability Concept A. Ecosys pulse even after reaching carrying cap (Odum et al. 95) 1. paradigm of repeating oscillation poised on edge of chaos 2. TSMs, MGs resist short-term env. s via spp. div, nutr. storage, recycling B. Physical energy pulses circ of inputs & waste removal, prod C. WTLs org. to receive pulses from & impose pulses on environment 43

44 Pulsed Stability 44

45 VII. Ecosystem Engineers A. Organisms can have strong autogenic effect on WTLs 1. Plant Example: Mangroves: roots trap debris, sediments 2. Wildlife Examples: Beaver, Muskrat: dam, burrow spp comp, hydrol Canada Geese, Nutria: herbivory, eat outs prod, structure Manatee, Dugong: herbivory prod, flow paths Alligators: gator holes hydrology, spp comp. 45

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