My talk will address the following questions • Why should we care about calcium (Ca) in the environment? • How are Ca levels in lakes, vegetation and soils changing? • What is causing the changes in Ca? • What will be the impact of timber harvesting on lake Ca levels? • What are the critical uncertainties?
Why should we care about calcium? Foliage: 1% Ca Wood: 0.1% Ca
Bark: 3% Ca Eggs: 30% Ca
Forest Floor 1%
More Ca: more snails (Skeldon et al. 2007)
Low Ca levels can stress trees
Calcium levels in soils of healthy and declining stands in Pennsylvania: Sharpe and Sunderland
Hallett et al. 2006
Link between soil and tree chemistry – in Ontario • soil Ca foliar Ca; 20000
20000 y = 1516Ln(x) + 12083 R2 = 0.58
18000
18000
14000
Foliar Ca (mg/kg)
foliar Ca (mg/kg)
16000 16000
14000
12000
12000 10000 8000 6000
10000
4000 8000
2000 0
6000 0
5
10
15
A-horizon Ca (meq/100g)
20
25
0
1
2
3
4
5
6
Soil Ca (meq/100g)
• as soil ex [Ca] increases, foliar [Ca] increases, to a point – most sites above the ‘critical thresholds’
7
Implications for surface waters
• ‘Canadian lakes suffering aquatic version of osteoporosis’ – Globe and Mail, 2008.
Calcium is an important nutrient for aquatic biota • Important for physiology (e.g. exoskeleton) • If Ca-demanding species are lost, declining Ca levels may affect lake community • May have other effects, such as reducing UV sensitivity
Loss of Daphnia pulex at Plastic Lake
Jeziorski, Yan, Paterson, Palmer, De Sellas, .. Smol, +10 others (Science)
Declining Ca will delay the chemical recovery of lakes! ANC = sum of base cations – acid anions
Sulphate Calcium ANC
140
150 125 100
130 75 120
50 110
100 1980
25
1985
1990
1995
Acid neutralising capacity (µeqL–1)
Lake concentration (µeq L–1)
150
0 2000
Plastic Lake: decrease in calcium and sulphate; no change ANC – NO CHEMICAL RECOVERY!
How are Ca levels in lakes, vegetation and soils changing? 4.0 79o00'
60
Study Area
Dorset 2
Port Sydney
3 4
3.5 BC CB CN HP HY PC RCE RCM
3.0
Dwight
5
35
9
Ca (mg/l)
1. Harp 2. Chub 3. Blue Chalk 1 4. Red Chalk 5. Red Chalk East 6. Dickie 7. Heney 8. Crosson Huntsville 9. Plastic
2.5 2.0 1.5
Baysville 6 117
Bracebridge
1.0
7
0.5
8 11 118
Carnarvon
OMOE A Lakes
2006
2003
2000
1997
1994
1991
1988
1985
1982
1979
Vankoughnet
1976
0.0
45o00'
18000 16000
Foliar Ca (mg/kg)
Mean change in foliar and soil Ca at 35 sugar maple stands in southern Ontario
14000 12000 10000 8000 6000 4000 2000 0
80°
1985
75°
2005 Year
18 #
#
N
# #
#
#
#
#
# #
# #
#
#
# #
#
#
44°
#
# # # #
#
#
## 44°
#
# # # #
A-horizon Ca (meq/100g)
#
16 14 12 10 8 6 4 2
#
0 1985 100
0
100
2005 Year
200 Kilometers CANADA
UNITED STATES
80°
75°
Miller and Watmough, 2009, Environmental Pollution
What is causing the changes in Ca? –acid deposition 350
300
Large Ca soil pool Ca (µeq/l)
250
F (0.8) F (0.4)
200
150
100
Small soil pool SoilCa acidification
Ca to lake
50 0
0
100
200
300
400
500
SO4 (µeq/l)
TIME Available Soil Ca
Available Soil Ca
2
1988-89
1990-91
1992-93
1994-95
1996-97
1988-89
1990-91
1992-93
1994-95
1996-97
1986-87
1984-85
1982-83
1980-81
1978-79
R = 0.70
1976-77
Si/Ca
1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7
RC-3
Year
1.3 2
1.2 Si/Ca
R = 0.61
1.1 1 0.9 0.8
BC-1
1986-87
1984-85
1982-83
1980-81
1978-79
0.7 1976-77
Elemental ratios (Si/Ca; Na/Ca) in many streams are indicative that decline in Ca is not due to changes (decreased) in mineral weathering.
Year
Calcium levels are currently higher than they were in the past
What will be the impact of timber harvesting on lake and soil Ca? Ca removed from site
Ca Deposition
Ca Deposition
Ca Weathering
Ca input to lake
Ca Weathering
Ca input to lake
Estimating the impact of timber harvesting on future lake Ca levels (Carolyn Reid’s MSc. thesis)
Approach for the Muskoka River Watershed
Tree Species (hardwood/softwood) + Stem, Bark, CWD Ca + Harvest Method + Rotation
Weathering from lake chemistry Ca:Na ratios (Watmough & Aherne, 2008)
FRI & FMP volume m3 Catchment Area ha
kg Calcium ha1yr-1 Deposition
Predict Lake Calcium mg/L
Muskoka River Watershed Study Area - 50.4 % Crown Land
Muskoka River Watershed Forest Resources Inventory (FRI)
Page  22
Muskoka River Watershed Lake Ca & Forestry Predicted Cuts Data
MRW lakes within Crown land with data - N=590 mg/L Ca (N=567) mg/L Ca (N=23)
Page  23
371 Lakes with Data in 283 Catchments with Predicted Cuts During 2009-2020
MRW lakes with data in catchments with cuts mg/L Ca (N= 371 of 567 on crown land) mg/L Ca (N= 0 of 23 on crown land)
Page  24
Distribution of MRW Lake Ca concentrations (mg/L) 590 lakes with data within crown land
371 (of 590) lakes located in catchments with cuts
Page  25
Note: 0 mg/L indicates undetectable levels
Calcium Deposition (Wet + Dry) Gradient Ca Deposition (kg/ha/yr) High 7.32
Low 4.52
Atmospheric Deposition from Environment Canada Page  26
Runoff Gradient
Page  27
Runoff annual average in mm from Global Runoff database 2012
Species type percentages by catchment Species % by catchment
Other Coniferous Deciduous
993 catchments in MRW 283 catchments with predicted cuts 371 lakes in those 283 catchments
Forest Resource Inventory data
Page  28
Just the mass balance to go!
A mass balance example: • A catchment where 30 m3/ha is removed every 25 years from 60% of its area. • Assumptions: – Wood concentration (1 g/kg) (90% biomass) – Bark concentration (30g/kg) (10% biomass) ~46 kg Ca ha-1 removed from 60% of catchment every 25 years = 1.1 kg Ca ha-1 yr-1
In this scenario, where lake runoff is 340 mm
Ca 0.3 mg/L
Answers to the questions • Why should we care about calcium (Ca) in the environment? – it is an essential nutrient required in large amounts by biota • How are Ca levels in lakes, vegetation and soils changing? – they are declining in many areas • What is causing the changes in Ca? – observed decline is primarily due to acid deposition changes • What will be the impact of timber harvesting on lake and soil Ca? – ultimately Ca levels will be lower than present or historical values
Critical Uncertainties • Sources of Ca to trees. • How much will Ca levels in tree wood/bark change? • Soil Ca weathering estimates • What are critical Ca levels in lakes?
• Time?
Acknowledgements • Thanks to all the students (Tyler, Diane, Ina, Colin, Carolyn) and technicians (Martina, Liana) who have made this work possible. • Funding from The Canadian Water Network. • Previous contributions from NSERC, OMOE, Environment Canada, CFS