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 2012Annual 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

Organic carbon content (%) in topsoils (0–30cm) in Europe. Peatlands are those with organic content of greater than 25% (Montanarella et al. (2006).

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.

Glenamong sub-catchment

GG Rain Gauge

GG Rain Gauge

GG Rain Gauge

GG Rain Gauge GG Rain Gauge

ARMS (Temperature, Conductivity, pH,

DO, CDOM fluorometer, nephelometer) and water level

recorder

•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?

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Global anomaly Furnace anomaly10 year moving average(Global) 10 year moving average(Furnace)10 year moving average(Ireland)

Air temperature trends globally, in Ireland and in Burrishoole

Fealy et al. RESCALE project final report 2010

Mean annual air temperature in Burrishoole increased significantly by 1.48 oC

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

After the autumn DOC flux, DOC concentrations remain comparatively low irrelevant to storm events

Precipitation

Seasonality of DOC export may result in an over estimation of DOC fluxes during winter/spring load estimates.

Glenamong Janurary 2010

Glenamong September 2010

Glenamong June 2010

Glenamong August 2010

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.

CDOM Fluorometers, under estimate the carbon exported from the catchment.

Full excitation emission plotsBlack square = where field

instrument measures370 – 440nm