Mesoscopes for Hydropedology in the Critical Zone
Dept. of Ecosystem Science and Management The Pennsylvania State University
henrylin@psu.edu
Henry Lin
Photo Courtesy: John A. Kelley
Understanding Soils – Their Architecture & Functional Manifestations
• Heterogeneity differs from randomness: the former is associated with order while the latter is linked to disorder.
• Organized heterogeneity reflects underlying structure that governs the direction and efficiency of energy and matter transfer.
• Evolutionary processes have been made possible because of heterogeneity of all kinds leading to the flow of energy and mass that are driven by various gradients at different scales.
Complexity
Randomness
II. Unorganized complexity (aggregates)
I. Organized simplicity (machines)
III. Organized complexity (systems)
Analytical treatment
Statistical treatment
Scientific treatment?
Large number systems
Small number systems
Medium number systems
Pedon Mesoscopic
Macroscopic
Microscopic
Model Scale
i i+1 i+2 i+3 i+4
i-1
i-2
i-3
i-4 Upscaling
Downscaling Processes
& Parameters
Hillslope processes Watershed
processes Regional processes
Global processes
Pore & molecular processes Mineral-organic complex processes
Aggregate processes
Horizon processes
Zoom in Zoom out
Organized complexity: too complex for analytical treatment and too organized for statistics → This is the region of so-called medium number systems where large fluctuations, irregularities, and discrepancy with any theory occur regularly
Microscope ↔ Mesoscope ↔ Telescope
(Modified from: Weinberg, 1975)
Pattern
Variability
Fast Slow
Time
Space Systems
P
Clay Coating
0.001 m
Regional control
Soil structural units
Soil-landscape units
S I
S
P I
1 m 1 m 0.1 m 1 km
P S
I
S P
I
Soil distribution pattern viewed from space
Soil architecture under microscope Tertiary
peds
Local control
Cutans Primary
peds
Secondary peds Crayfish
biotube
(Lin, 2012, Hydropedology)
Soil Architecture Preferential Flow
(Lin, 2012, Hydropedology)
Stream Gauge
Sediment Fence
Dry (D1)
Moderately Dry (D2) Wet (W1)
Moderately Wet (W2) Subsoil Moisture Clusters of the Monitoring Sites
~100 m
N
1 E
2
3
4
5 6
9 8 7 10 11
14 13
12 15
A1 22
23
24
25
26
27
29 28
30 31
36 35
34 33 32
37 38
39 40
41
44 43
42 45
47 46 48
49
50 54
53
52 51 58 57
56 55 59
60
61 67
66 65
6364 62
71 70
69 68 73 72
A2
A3A4 A5 B2
B3B4
B5
B1
Automatic soil monitoring stations
128 15 22
40 5
68 92
162 122
(m)
Depth (cm)
Weikert Berks Rushtown Ernest Blairton
0
25
50
75 100
125
150
175
Inceptisols Ultisols
Soil Map
Site 53 right (Berks)
Date
10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00
Volumetric water content (m3 /m3 )
0.0 0.1 0.2 0.3 0.4 0.5
Rainfall (mm/10min)
0 10 20 30 40 50
11/16/06 11/17/06
Oe-A (5 cm) A (10 cm)
BC-C (88 cm) Bw2 (40cm)
C (103 cm)
14:03 14:12 13:52
14:06 13:53
Response time
Transient saturation
14:08 16:35
14:17 14:46
(Lin and Zhou, 2008, EJSS)
Controls and Frequency of Preferential Flow Occurrence: A 175-Event Analysis
• Preferential flow was common throughout the catchment, occurring during 17 to 54% of the 175 events at each of the 10 monitored sites along a hillslope. Preferential flow occurred in at least one site during 90% of the 175 events.
While the frequency of preferential flow appeared insensitive to topographic position, the controls on preferential flow initiation varied with landscape position. While the frequency of preferential flow can be determined from 1 yr of real-time monitoring, the controls on preferential flow require much longer (≥ 3 yr) monitoring to be reliably identified.
(Graham and Lin, VZJ, 2011)
(Liu and Lin, SSSAJ, 2014)
Preferential flow occurred during <1% to 70% (overall average 26%) of 323 events over 5.5 years (2006-2012) at each of 35 monitored sites, with 90% of the events generating preferential flow in at least one site.
Ridge Top Midslope Valley Floor
Seasonal profiles show strong isotopic attenuation with depth.
In winter, preferential flow occurs along soil-horizon and soil-bedrock interfaces.
In summer, preferential flow occurs vertically through macropores.
(Thomas et al., VZJ, 2013)
A) Complex slope
B) Planar slope
C) Swale cross-section
Weikert
Berks
Rushtown
Weikert
Berks
Rushtown
Weikert Berks
Weikert
C A B
(Lin, Hydropedology, 2012)
Weikert soil
Dry
Wet
Dry
Wet Bw
BC
C Rushtown soil
(Zhang et al., 2014)
Time-lapsed GPR in combination with real-time soil water monitoring have revealed flow paths in fractured shales and the impacts of soil layering on subsurface lateral flow
5, 15, 30, 45, 60 min
53 L 53 L
5, 15, 30 min
(Guo et al., WRR, in revision)
Time‐Lapsed GPR Radargram Interpretation After Water Infiltration into Soils
Oe and A: 0‐12 cm BW : 12‐45 cm
BC: 45‐90 cm
C: 90‐135 cm
Deep lateral macropore flow
Vertical macropore flow
Near‐surface lateral macropore flow and vertical finger flow
Subsurface flow network
(Guo et al., WRR, in revision)
Earth System Physiographic
Regions Watershed
Soils Soil
Landscapes Soil
Catenae Soil
Profiles Soil
Horizons Soil
Aggregates Soil
Particles Soil
Microbes
Global Model GIS
RS
RS GIS EMI
GPR GPR ERT PT
PT GPR CT TS
CT PCR
DNA SEM TEM Synchrotron
Microprobe
Geospatial Geophysics
Microscopy Spectroscopy
Spatial scale (m)
Molecular Structures
100
Catana/Soilscape Soil sequence/zone
10-2
10-6 10-4 102 104 106
Soil structural units (soil profile features)
Soil-landscape units (soil map units)
Particle/Pore/Aggregate Horizon/Pedon
Visual
Green water: Essential in combating looming global freshwater crisis
(P. Rogers, 2008)
Vadose zone
Ground water (fresh water)
Confining unit
Aquifer (saline water)
Leaching of fertilizers &
pesticides on farmlands Septic
tank
Leaking petroleum
tank Chemical
spill Landfill leaching
Water Table
Toxic waste dump
Pumping well
Shallow well
Abandoned well
Root zone
Inter- mediate
zone
Capillary fringe
(Modified from: Fetter, 1993)
..?
Sub-basin: 3D view 10 km
100 km
River basin: plan view
d.
(Modified from McClain et al., 2003)
Biogeochemical hot spots and hot moments in the landscape
While landform and vegetation can now be mapped with high resolution, we lack adequate tools and techniques for in situ, precision, continuous, and noninvasive mapping and sensing of the complex subsurface. Improved mesoscopes (i.e., devices or techniques that are between microscopes and telescopes) are needed to shed better light on the complex subsurface in the Critical Zone.
