Closing the carbon budget of a Scots pine forest in the Netherlands

The aim of this study was to close the carbon budget and reduce uncertainty in annual C balances for Scots pine (Pinus sylvestris) forests in The Netherlands. This was done by comparing estimates of the Net Ecosystem Exchange (NEE) as assessed by two different methods. The inventory based carbon budgeting method estimated the average NEE for 1997 – 2001 at 202 g C m–2 yr–1 (a sink) with a confidence interval of 138 – 271 g C m–2 yr–1. The estimate obtained by the eddy covariance method was 295 g C m–2 yr–1 on average for the same period, with a confidence interval of 224 – 366 g C m–2 yr–1. Uncertainties in the eddy covariance method were mostly related to gap filling of the data. Main uncertainties in the inventory-based method are related to the soil and the root compartment. The difference in NEE as obtained by two independent methods indicates that it is not straightforward to design a sound National System for monitoring and reporting of the total land area and for accounting of changes in forest area under the Kyoto Protocol, and that more effort is required in this field.