Future Forests. Sustainable strategies under uncertainty and risk
THE LONGLONG-TERM SUPPLY OF BASE CATIONS IN SWEDISH FORESTS: EVALUATING MODELS WITH EMPIRICAL DATA Richard Lucas Ryan Sponseller Hjalmar Laudon Dept. ...
THE LONGLONG-TERM SUPPLY OF BASE CATIONS IN SWEDISH FORESTS: EVALUATING MODELS WITH EMPIRICAL DATA Richard Lucas Ryan Sponseller Hjalmar Laudon Dept. of Forest Ecology and Management SLU Umeå Umeå
Future Forests Sustainable strategies under uncertainty and risk
Sufficient Base Cation Supply?
Future Forests Sustainable strategies under uncertainty and risk
Leakage
• Problem: large removals of base cations out of watersheds • From tree harvest and hydrological export
Photo: K. Lucas (Laudon et al. 2011)
Patterns of Base Cation Concentrations in Swedish Waters 2.0
z score of [Mg] in streams
1.5 1.0 0.5 0.0 -0.5 -1.0
r2 = 0.625 inflection = 1992
North Middle South
-1.5 -2.0 1980
1985
1990
1995
2000
2005
2010
2015
Year
z=
xi − xwatershed swatersged
Future Forests Sustainable strategies under uncertainty and risk
Data Source: Swedish National Monitoring Data & Svenska Miljöinstitutet
Questions • Is the long-term decrease in base cation concentrations a result of acid deposition? • What are possible covariates and mechanisms driving the observed pattern? • How is long-term tree growth affected?
Future Forests Sustainable strategies under uncertainty and risk
Recovery from Acid Deposition? Sulfur
Stream Waters of Whole Country
Deposition by Region
Nitrogen
Future Forests Sustainable strategies under uncertainty and risk
Data Source: Swedish National Monitoring Data & Svenska Miljöinstitutet
Relationship Between Base Cations and Acid Deposition? Calcium median [Ca] (z score)
1.0 0.5 0.0 -0.5 OLS r2 = 0.24 p-value = 0.01
-1.0 -1.5 -1.0
-0.5
0.0
0.5
1.0
median [NO2 + NO3] (z scores)
median [Ca] (z score)
1.5
S Deposition
Still a great deal of variance to be explained, must be something more
N Deposition
1.5
1.0 0.5 0.0 -0.5 OLS r2 = 0.34 p-value = 0.00
-1.0 -1.5 -1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
median [SO4] (z scores)
Future Forests Sustainable strategies under uncertainty and risk
Data Source: Swedish National Monitoring Data & Svenska Miljöinstitutet
Are NO3- and DOC Drivers of BC? • Concurrent with [BC] decrease is a decrease in [NO3-], and an increase in [DOC] in streams • When [NO3-] and [DOC] are used as covariates to explain [base cations], r2 = 0.71 • This implies a relationship
r2 = 0.62
r2 = 0.52
Future Forests Sustainable strategies under uncertainty and risk
Future Forests Sustainable strategies under uncertainty and risk
After Lindahl et al. 2005
C Allocation Belowground N-limited forest, Abundant mycorrhizal community
N-rich forest, Less abundant mycorrhizal community
Litter
Litter
More soil fungi
Less soil fungi More C allocated belowground
Organic Soil Pool
Auto/Heterotrophs Mineralization Production of organic acids
Temperature Atmospheric CO2 pH
DOC
NO3-
Base Cations
Future Forests Sustainable strategies under uncertainty and risk
Less C allocated belowground
Organic Soil Pool
Auto/Heterotrophs Mineralization Production of organic acids
DOC
NO3-
Base Cations
N addition treatments in Exp. 55 at Norrliden, N. Sweden
Cumulative Total N added (kg N ha-1)
3000 2500 2000 1500
Future Forests Sustainable strategies under uncertainty and risk
30 kg N ha-1
1000 500
0 kg N ha-1
0
1970
(Laudon et al. 2011)
60 kg ha-1 90 kg N ha-1
low medium high
1980
1990 Year
2000
2010
Exchangeable base cations, % of control (N0)
Rapid recovery of soil base saturation (at 5-15 cm soil depth) after termination of high N load 120
N0 - control
100
80
N3 – 90 kg N ha-1 yr-1
60
N1 – 30 kg N ha-1 yr-1
40
N2 – 60 kg N ha-1 yr-1
20
*termination of N3 0 1970
1980
Future Forests Sustainable strategies under uncertainty and risk
1990
2000
2010
Year (Tamm et al. 1999; Aaronsson et al. 1999; Högberg et al. 2006)
Sporocarp Recovery at Norrliden Biomass
Lucas et al. (unpublished data)
Future Forests Sustainable strategies under uncertainty and risk
N15 of current needles
Högberg et al. (2011)
Two lines of Evidence Suggesting No Growth Decrease 4000 3500 3000
Standing Tree Volume (million m3sk)
2500 2000 1000 1500
800
N Norrland S Norrland Svealand Götaland Whole country
600
400
1920
Lucas et al. (2011)
Future Forests Sustainable strategies under uncertainty and risk
1940
1960
1980
2000
Year
Data : Swedish National Forest Inventory 2010
2020
Conclusions • Acid deposition is only one important covariate explaining long-term decrease in base cation concentrations • Functioning of soil biota is critically important • Current models explaining the availability of base cations do not include biology • Long-term supply?? Future Forests Sustainable strategies under uncertainty and risk
Questions?
Future Forests Sustainable strategies under uncertainty and risk
