The costs of monitoring changes in forest soil carbon stocks

The forest soil carbon sink is of potentially great monetary value under subsequent climate conventions, but the costs of reliable monitoring have never been analysed. Our study aimed at evaluating (1) costs and precision of varied sampling intensities at the plot level, (2) sample size, and (3) costs needed to detect a change in soil carbon at the national scale. Organic layer carbon measurements cost 520 euros per plot if 10 samples are analysed. At plot scale, the precision obtained with such sampling allows detection of a large change > 860 g C m -2 . At the national scale, two measurement rounds on a minimum of 3000 plots are needed to detect an expected change of 11 g C m -2 yr -1 in the organic layer of upland forest soils with a 10-year sampling interval. Measuring such a network once costs approximately 4 million euros, which is about 8% of the value of the annual CO 2 sequestration of 2.57 x 10 6 t CO 2 of upland forest soils in Finland.