Impact of climate on export of DOC
from a peatland catchment.
Elizabeth Ryder, Elvira de Eyto, Mary Dillane, Russell
Poole, Suzanne Linnane and Eleanor Jennings.
2nd of March 2012
Annual Meeting of Freshwater Biologists
Trinity College Dublin.
Introduction
• Sources of carbon
• Site Description
• Drivers of carbon
– Examples.
Sources of carbon
Two main sources of carbon, specifically dissolved
organic carbon (DOC) in aquatic ecosystems
1. Terrestrial (Allochthonous carbon)
2. Primary production (Autochthonous carbon).
Sources of carbon
Worldwide peatlands cover 500
million hectare of land.
Most extensive in Europe and North
America.
Peatlands or bogs are one of the
largest stores of carbon in the world.
Organic carbon content (%) in topsoils (0–30cm) in Europe.
Peatlands are those with organic content of greater than 25%
(Montanarella et al. (2006).
Glenamong sub-catchment
GG Rain Gauge
GG Rain Gauge
ARMS
(Temperature, Conductivity, pH,
DO, CDOM fluorometer,
nephelometer) and water level
recorder
GG Rain Gauge
GG Rain Gauge
GG Rain Gauge
•Catchment Area 1821 ha.
•Forested area 408 ha = 22%
•Annual rainfall = 2000mm
CDOM fluorometer: Chromophoric Dissolved Organic
Matter is the light absorbing component of dissolved
organic matter.
After initial corrections and calibrations
1. CDOM fluorescence (mV) temperature corrected.
2. CDOM fluorescence (mV) was converted into QSU
CDOM fluorescence can be used as a proxy for dissolved
organic carbon (DOC).
Water Colour is also a proxy for DOC.
Mean daily DOC export from the GG catchment
Annual DOC export
9.87 tC km2
DOC Drivers
1. Temperature
2. Soil moisture (Impact on decomposition processes)
3. Precipitation (variation in timing and intensity)
Glenamong DOC export 2010-2011
Temperature
•Soil organic matter decomposition in response to temperature
•Temperature effect on decomposition rates vary due to different soil
moisture content leading to differences in aerobic and anaerobic
decomposition
Temperature
How will global warming affect these carbon pools?
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1890
1900
1910
1920
1930
1940
Global anomaly
10 year moving average(Global)
10 year moving average(Ireland)
1950
1960
1970
1980
1990
2000
2010
Furnace anomaly
10 year moving average(Furnace)
Air temperature trends globally, in Ireland and in Burrishoole
Mean annual air temperature in Burrishoole
increased significantly by 1.48 oC
Fealy et al. RESCALE project final report 2010
Soil Moisture
• Production of DOC have been shown to be correlated with low
soil moisture over time.
• Decomposition rates of peatlands are very sensitive to
changes in soil moisture, particularly in soils that are generally
water logged.
• Decrease in water table, allowing oxygen into anoxic layers
and lead to increase in aerobic decomposition of peat
Precipitation
Low soil moisture + high precipitation
Drought/Precipitation event
Drought/Precipitation event
Precipitation
After the autumn DOC flux, DOC concentrations
remain comparatively low irrelevant to storm events
Seasonality of DOC export may result in an over
estimation of DOC fluxes during winter/spring
load estimates.
Emission-Excitation Matrix Scans (EEM’s) for Glenamong River.
The EEM scan enables a detailed characterisation of the organic matter and can
discriminate between humic and fulvic-like acid.
Glenamong Janurary 2010
Glenamong June 2010
Glenamong August 2010
Full excitation emission plots
Black square = where field
instrument measures
370 – 440nm
Glenamong September 2010
CDOM Fluorometers, under estimate the carbon exported from the catchment.