18.02.2016
What is Sphagnum moss and peat ?
Facts:
Photosynthetic activity at capitula
Water supply: rain and capillarity
Water storage in hyaline cells
Abundance: ~ 1.5x106 km²
Dynamic non-equilibrium water flow in
Sphagnum moss and peat
Tobias KD Weber (1),(3), E Diamantopoulos (2), W Durner (1), JS Price (3)
(1)
(2)
(3)
Soil Science and Soil Physics, Institute of Geoecology, TU Braunschweig, Germany
Land, Air and Water Resources, Plant and Environmental Sciences, UC Davis, CA
Department of Geography and Environmental Management, University of Waterloo, Canada
(left) CC BY-SA 3.0
Indication of DNE in Sphagnum moss and peat
1
2
Monotonic variation of pressure head boundary condition at LB
1.00
0.95
0.90
0.80
0.85
L = 5 cm
h0.80L (t)
0.75
vol. water content [ - ]
10 cm
qL0(t) = 0
hLB (t)
0.70
2.0
1.5
1.0
0.5
0.0
0
cum. evaporation [ cm ]
0
-10
-15
-20
-25
-35
-30
pressure head [ cm ]
-5
pressure head at 1.25 cm
pressure head at 3.75 cm
cum. evaporation
2
Multi Step Outflow Experiments
Retention Curve
Laboratory measurements
(right) Weber, 2014
Weber et al. | Dynamic nonequilibrium in Sphagnum moss and peat | SSSA Annual Meeting, 16 Nov 2015
ASA, CSSA, & SSSA International Annual Meeting, Nov 15-18, Minneapolis, MN
3
0.0
time [ d ]
0.5
1.0
qLB (t)
1.5
pF [ - ]
Weber, unpublished data, 2013
Weber et al. | Dynamic nonequilibrium in Sphagnum moss and peat | SSSA Annual Meeting, 16 Nov 2015
3
Results: Observations
Weber et al. | Dynamic nonequilibrium in Sphagnum moss and peat | SSSA Annual Meeting, 16 Nov 2015
4
Results: Observations + Simulation Richards
time [ min ]
Weber et al. | Dynamic nonequilibrium in Sphagnum moss and peat | SSSA Annual Meeting, 16 Nov 2015
time [ min ]
5
Weber et al. | Dynamic nonequilibrium in Sphagnum moss and peat | SSSA Annual Meeting, 16 Nov 2015
6
1
18.02.2016
The Conceptual Model
Results: Observations + Simulation Richards + Simulation DNE
Dual-Fraction DNE Model [Diamantopoulos et al. (2012), WRR]
equilibrium
water flow
nonequilibrium
water flow
1  f ne
f ne
time [ min ]
Weber et al. | Dynamic nonequilibrium in Sphagnum moss and peat | SSSA Annual Meeting, 16 Nov 2015
7
Weber et al. | Dynamic nonequilibrium in Sphagnum moss and peat | SSSA Annual Meeting, 16 Nov 2015
8
Conclusions
 DNE is observable in peat under 2 boundary conditions.
 The Dual-Fraction model cannot describe all of the DNE in our case.
 The effective model approach better than Richards.
Cheers !
Thanks to:
Dr. Sascha Iden, TU Braunschweig
Weber et al. | Dynamic nonequilibrium in Sphagnum moss and peat | SSSA Annual Meeting, 16 Nov 2015
9
ASA, CSSA, & SSSA International Annual Meeting, Nov 15-18, Minneapolis, MN
2