Can we get an operational indicator of forest carbon sequestration? A case study from two forest regions in Spain

Indicators for sustainable forest management are considered to be key tools for the implementation of regional, national and international forest policies. The Montreal process identified the “maintenance of forest contribution to global carbon cycles” as an essential component in sustainable management of forest ecosystems. Carbon sink evaluations provide reference information to policy-makers, stakeholders, resource managers and concerned citizens about the sustainable use of our forests for present and future generations. Two forest areas in northern and central Spain (‘Páramos y Valles’ and Central Mountain Range) were chosen as pilot areas to test the use of the National Forest Inventory to calculate carbon biomass forest sink at operational level. Data from the Second and Third National Forest Inventory (2NFI and 3NFI, respectively), together with biomass equations were used. Total carbon biomass sink was calculated as a balance between carbon dioxide inputs and outputs in forest biomass. Tree growth between 2NFI and 3NFI, new plots and ingrowth (recruitment and upgrowth) biomass were considered as inputs, while forest harvesting and natural mortality were considered as outputs. In ‘Páramos y Valles’, 2.46MgCO₂ha⁻¹year⁻¹ was fixed in the tree biomass of forest ecosystems from 2NFI to 3NFI, whereas in the Central Mountain Range the fixation was 0.72MgCO₂ha⁻¹year⁻¹ in the period between inventories. The balance of CO₂ in the two areas was positive in 3NFI, with more than four million Mg of CO₂ accumulated in ‘Páramos y Valles’ and more than 72 million Mg of CO₂ fixed in the Central Mountain Range. Forest ecosystems are carbon sinks in the tree biomass in the two areas considered.