Managing Forests for Increased
Water Yield in Florida
Daniel McLaughlin, Matthew Cohen, and David Kaplan
University of Florida, School of Forest Resources and Conservation
Water Yield = Precipitation - Evapotranspiration
Annual Precipitation
Annual ET
Oregon State University: www.prismclimate.org
Hobbins et al. (2010)
Modify “non-point source consumption”
 Can we manage forests for increased water yield?
Small Reductions in ET  Large Increase in Yield
ET ≈ 2.9 mm/day (Gholz and Clark, 2002)
ET ≈ 2.2 mm/day (Bracho et al., 2008)
18%
18%
Yield
ET
8%
Relative to Rain
92%
82%
71%
29%
Yield
ET
Caveats First! Land Use  Water Use
Agricultural Irrigation in FL
• 2800 MGD (Marella, 2009)
• 40% of all freshwater withdrawals
UF, IFAS
Silviculture in FL
• 0 MGD
• Water conservative land use
Production vs. Historic Pinelands
• Site preparation: bedding,
fertilization, weed control
• High tree density & basal area
• 15-20 m2/ha
www.sarracenia.com
• ~2 million ha (Brown, 2005)
• Reduced habitat value…
• Water use over 25-year rotation?
Production vs. Historic Pinelands
• Widely spaced trees
• Basal Area: ~8-10 m2/ha
(Freeman and Jose, 2009)
• Frequent fire (every 2-3 yr)
• Species-rich plant communities and
critical wildlife habitat (Peet and Allard, 1993;
Means, 2006)
• Only 2% remains due to
development and plantation forestry
USFWS
Managing Forests for Increased Water Yield
Overarching Idea: Decreasing biomass and leaf area in forested
uplands decreases evapotranspiration (ET), increasing water yield
to aquifers and surface water bodies
Challenge: Relate stand attributes to water use
Stand Attributes: Basal Area (BA), Leaf Area Index (LAI), Tree
Height, Tree Density, Stand Age
Water Use: Ratio of evapotranspiration to precipitation (ET/PPT)
Study
Knowles (1996)
Ewel and Gholz (1991)
Liu et al. (1998)
Liu et al. (1998)
Liu et al. (1998)
Riekerk (1985)
Powell et al. (2005)
Loc.
FL
FL
FL
FL
FL
FL
FL
Bidlake et al. (1996)
Sumner (2001)
Gholz and Clark (2002)
Gholz and Clark (2002)
Gholz and Clark (2002)
Liu (1996)
Amatya et al. (1996)
Sun et al. (2010)
Sun et al. (2010)
FL
FL
FL
FL
FL
FL
NC
NC
NC
Landuse Dominant Sp. Age (yrs) Tree Ht (m) Density (trees/ha) LAI (m2/m2) BA (m2/ha) ET (mm/yr) PPT (mm/yr) ET/PPT Method
PP
Slash
5
1.5
3000
2.3
813
1270
0.64
EC
PP
Slash
29
17.0
1150
6.5
27.2
1168
1187
0.98
MS
PP
Slash
30
5.0
1020
1276
0.80
EC+MS
PP
Slash
30
6.0
1109
1276
0.87
EC+MS
PP
Slash
30
7.0
1178
1276
0.92
EC+MS
PP
Slash
5
1000
1006
1254
0.80
LM
NR
Slash, Longleaf
60
22.0
325
4.7
18.0
754
884
0.85
EC
Overstory
3.6
415
884
0.47
EC
Understory
1.1
339
884
0.38
EC
NR
Slash
7.8
96
< 20% Canopy Coverage
1060
1440
0.74
EC
PP
Slash, Cypress
30
1048
1245
0.84
EC
PP
Slash
1
1.0
3000
3.0
959
1127
0.85
EC
PP
Slash
10
11.0
2075
5.1
15.7
1058
1062
1.00
EC
PP
Slash
25
19.2
1184
6.5
31.4
1194
1288
0.93
EC
PP
Slash
30
17.5
544
3.7
14.2
800
1333
0.60
EC+MS
PP
Loblolly
17
9
16.1
1060
1515
0.70
WB
PP
Loblolly
5
1040
838
1274
0.66
EC
PP
Loblolly
14
12.9
1660
11.0
25
1087
1238
0.88
EC
McLaughlin et al. (in press)
Water Yield Model
Pine Plantation (PP)
Low Basal Area (LBA 8-14)
Stand Age  LAI
Basal Area  LAI
Leaf Area Index  ET/PPT
3-yr fire return frequency
æ
ET ö
Water Yield = ç1÷ * MAP
è PPT ø
Relating stand attributes to water use
• Leaf area index (LAI)  water use (ET/PPT)
Photo by S.B. Weiss
McLaughlin et al. (in press)
Relating stand attributes to water use
• Basal Area  Leaf Area Index (LAI)
Center for Longleaf Pine Ecosystems
McLaughlin et al. (in press)
Relating stand attributes to water use
• Stand Age  Leaf Area Index (LAI)
www.sarracenia.com
McLaughlin et al. (in press)
Water Yield Model
Pine Plantation (PP-High/Low)
Stand Age  LAI
Low Basal Area (LBA 8-14)
Basal Area  LAI
Leaf Area Index  ET/PPT
3-yr fire return frequency
æ
ET ö
Water Yield = ç1÷ * MAP
è PPT ø
Results: Annual Water Yield
• Pine plantations (PP) vs. systems managed for low basal area (LBA)
McLaughlin et al. (in press)
Results: Cumulative Water Yield
• Pine plantations (PP) vs. systems managed for low basal area (LBA)
McLaughlin et al. (in press)
Results: Increased Regional Water Yield
SouthernForests
Forests
©©Southern
Uncertainty and Need for Future Research
Sources of uncertainty:
• Climatic variation and site differences
• Water use in young stands
• Fire effects
Opportunity for Dual-Benefit Management
• Habitat and Water Yield – upland forests, cypress domes,
herbaceous-dominated systems.....FIRE!!!
• Support current land management on public lands
• Hydrologic Easements for management on private lands
• Caveat Redux: “Non-point source consumption” vs. withdrawels
– One element of broader water conservation strategy
SW Florida Water Mgmt. District
City of Titusville
Managing Forests for Increased
Water Yield in Florida
Proposed Research
Research Goals:
1) Measure forest biomass and water use in differently managed forests
2) Quantify the relationship between forest management and water yield
3) Scale up to determine benefits of forest management to regional water
availability
Budget for 15 Sites
Total Personnel
Research Scientist (0.33 FTE)
Fringe (23.5%)
Field Technician
Fringe (33.5%)
Equipment
Groundwater Wells
Soil Moisture Probes
Weather Stations
LAI Meter Rental
Other
Materials and Supplies
Field travel and logistics
Subtotal
Overhead (UF 25%) (MTDC)
TOTAL
Year 1
Year 2
Year 3
Year 4
Total
$21,450
$5,041
$11,250
$3,769
$22,094
$5,192
$11,588
$3,882
$22,756
$5,348
$11,935
$3,998
$23,439
$5,508
$12,293
$4,118
$43,544
$10,233
$22,838
$7,651
$20,750
$77,250
$5,000
$0
$0
$0
$0
$1,200
$0
$0
$0
$1,200
$0
$0
$0
$1,200
$20,750
$77,250
$5,000
$1,200
$4,000
$3,500
$152,010
$38,002
$190,012
$1,000
$3,500
$48,455
$12,114
$60,568
$1,000
$3,500
$49,737
$12,434
$62,172
$1,000
$3,500
$51,059
$12,765
$63,823
$5,000
$7,000
$200,464
$50,116
$250,580