Fingerprint

Just as fingerprints are unique for each individual, ecosystems have unique daily and yearly patterns of carbon dioxide uptake. This figure is a fingerprint plot of the carbon dioxide uptake at Griffin forest for a five-year period.

At any point in the fingerprint plot, the colour of the plot identifies the rate of carbon dioxide uptake at the time of year and time of day, which are read from the x and y axes.

There are several important features of the carbon dioxide flux at Griffin that should be noted:

There is always carbon dioxide uptake during the day.

Carbon dioxide loss at night (respiration) is largest after sunset in late summer.

Annual patterns

Net carbon exchange is a balance between uptake and loss. Carbon uptake (green curve in top figure - negative values indicate uptake) is the result of photosynthesis by the canopy which continues throughout the year. Carbon losses to respiration by the soil and canopy (black curve) also occur throughout the year. The peak in August reflects the control temperature has on respiration. The net uptake of the canopy (red curve) is the difference between uptake and losses. At Griffin the forest has a net uptake of carbon for 8 out of 12 months. It is only the combination of strong respiraiton and low light levels in the autumn that results in carbon loss from this site.

Althogh gross carbon uptake increases rapidly after January with increases in light levels, the growth of aboveground canopy biomass does not show increases until nearly mid-year. The bottom figure shows the annual change in canopy drag coefficient, which is consistent with observed increases in canopy height. However, the timing of the increase in canopy drag coefficient suggests that the canopy does not start to grow until May. It is believed that the strong gross photosynthesis occuring before May is being used to support below-ground biomass growth.

Diel pattern

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Light response

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Respiration

While photosynthesis is the process that results in carbon accumulation by the forest, respiration results in carbon loss by the forest. Respiration occurs continuously but, when using micrometeorological methods, it is only observable during the night when photosynthesis does not occur. Because respiraiton is a chemical reaction it is known to have an exponential relationship to temperature. The simple model of respiration (red dots in figure) used at Griffin incorporates soil and air temperatures and soil moiture, resulting in the scatter of the model with respect to increases in soil temperature.

Respiration underestimate

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Griffin Carbon Stocks

Biomass Distribution

The biomass distribution was measured in 1998. The measurement plots (10x10 m) were organized in a grid with a 100 m spacing between plots. Biomass was determined using allometric relations to DBH measurements.

The spatial distribution of the biomass was quite variable, in spite of the relatively homogeneous appearing forest cover presented from aerial photos.

Tree Ring Estimates of Biomass

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Soil Carbon sequestration

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Litterfall

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Chamber measurements

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Carbon budget

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