Mosaic: Predictions from Alternative

Transcription

1 Flow and Pattern in the Ridge Slough Mosaic: Predictions from Alternative Mechanisms of Landform Development Matt Cohen, Danielle Watts, Todd Osborne University of Florida Jim Heffernan Florida International University Greater Everglades Ecosystem Research Conference Greater Everglades Ecosystem Research Conference Naples, Florida July 2010

2 Self Organized Patterned Landscapes Pattern emerges from coupled spatial feedbacks Local positive feedbacks Facilitation Distal negative feedbacks Inhibition Isotropic ~ round Anisotropic ~ oriented Ptt Patterned vs. Unpatterned stable states Management implications Rietkerk and van de Koppel (2008) TREE

3 Everglades Patterned Landscapes Biota control landform & nutrients (Cohenet et al. in press) Ridge slough: Productivity, peat accretion, hydrology Big Cypress: Productivity, dissolution, hydrology Tree Il Islands: Productivity, i nutrient gradients, hydrology

4 The Ridge Slough g Mosaic SCT (2003) report posed key questions that are at the heart of today s session whence the pattern? Vertical corrugation Longitudinal elongation Lateral wavelength What does get the water right mean? SCT (2003)

5 Get the Hydroperiod Right: A Point Scale Conceptual Model SLOUGH Feedback cartoons RIDGE Nominal Landscape Peat Accretion Rate ~ 1 mm/yr (Net Autotrophy, P>R) Ridges Respiration i Primary Production Ca arbon Flux Unstable Sloughs Peat Elevation

6 Watts et al. in press

7 Wu et al. (2006) Watts et al. in press

8 Point scale model cannot explain: Patch prevalence (50% R, 50% S) Patch size ( m wavelength) Patch geometry (anisotropic, elongated with flow) Pattern Formation

9 Local Facilitation, Distal Inhibition Au utocorrelat tion correlatio on Auto Local (+) Orthogonal Local Orthogonal Distal Site (increasing slough abundance) Distal ( ) Watts et al. in press

10 partial sill partial sill Q = nugget + partial sill Semi variance Q (%) nugget Minor range Semi varia nce Anisotropy Major range Distance AI = Major range Minor Range Drained Sta tabilized ENP Conse served 1 Conse served 2 Trans nsition 1 Trans nsition 2 Impo pounded D Watts et al. in press 1.0 Increasing Slough Abundance

11 Mechanisms of Flow Controls H1 Flow creates pattern via redistribution of sediments (differential vegetation resistance) Larsen et al. 2010, Larsen et al. in press H2 Flow creates pattern via patch geometry effects on discharge competence Cohen et al. in press, Watts et al H3 Flow creates pattern via lateral P redistribution (slough to ridge) Cheng et al in press Cheng et al. in press All 3 may operate, interacting to control the range of conditions over which pattern is stable

12 Flow Control of Pattern Alternative Conceptual Models Sediment redistribution Higher velocity insloughs entrains EPISODIC sediment VELOCITY Slower velocity in ridges deposits + sediment Flow Elongation Constriction occurs due to redistribution Lateral Ridge Water slope > Bed slope Lateral Slough Expansion Expansion Distal feedback via effect oflateralridge + ridge expansion on slough velocity Velocity/ Scour + Discharge competence 5xhigher specific discharge (m DISCHARGE 3 /m/d) in sloughs TO SUPPORT HYDROPERIOD More sloughs = better drainage Better drainage = Less sloughs Discharge + Competence Elongation lets sloughs connect indirectionof of regional flow Lateral Distal Ridge negative feedback Lateral Slough via Expansion Expansion effect of lateral ridge expansion ondischarge competence + Imagine Tamiami Trail going N S Hydroperiod instead of E W

13 Discrimination Presence/absence of distal inhibition Time domain? C accretion deficit at modern ridge edges, surplus at slough edges Incidence, duration and spatial domain of historical water slope excursions Natural systems model? Evidence of mass transfer to ridge edgesoils Recalcitrance of sediment/ floc post deposition Nutrient effects? Modeling Variable local water slope Displacement/hydroperiod effects Decomp Physical Model and Miami Canal Backfill

14 Evaluating Discharge Competence Do lateral changes in ridge prevalence meaningfully affect water depths? Manning s Equation: Q = [k R h 0.67 S 0.5 ]/n; n R = 0.5, n S = 0.4 Change %Ridge (10% 90%) and Q; Fixed S (3 cm/km) Solve for depth (R h ) and velocity (Q/A)

15 Simple Solutions to Landscape Discharge Competence

16 Self Organized P Enrichment Lateral P transport due to differential ET (ridge > slough) and flow oriented variation in hydraulic conductivity (Cheng et al. in press) + P Evapo concentration ti Lateral Ridge Expansion + Lateral Slough Expansion P Availability

17 TP vs. Water Depth

18 Self Organization of Landscape Nutrient Content

19 Synthesis and Today s Task Spatial pattern loss, but NOT everywhere Distal feedbacks significant in WCA3A & ENP Flow clearly matters Vl Velocity vs. discharge remains a key question Plausibly both Distinguishing i predictions (role, importance) are scientific priorities Hd Hydroperiod idrestoration ti is top priority it where landscape variance persists? Options where landform variance is gone?

20 Thanks! Funding: South Florida Water Management District, US Army Corps of Engineers, US National Park Service