Environmental change impacts on the C- and N-cycle of European forests: a model comparison study

[摘要] Forests are important components of the greenhouse gas balance of Europe.There is considerable uncertainty about how predicted changes to climate andnitrogen deposition will perturb the carbon and nitrogen cycles of Europeanforests and thereby alter forest growth, carbon sequestration and N₂Oemission. The present study aimed to quantify the carbon and nitrogenbalance, including the exchange of greenhouse gases, of European forests overthe period 2010–2030, with a particular emphasis on the spatial variabilityof change. The analysis was carried out for two tree species: European beechand Scots pine. For this purpose, four different dynamic models were used:BASFOR, DailyDayCent, INTEGRATOR and Landscape-DNDC. These models span arange from semi-empirical to complex mechanistic. Comparison of these modelsallowed assessment of the extent to which model predictions depended ondifferences in model inputs and structure. We found a European average carbonsink of 0.160 ± 0.020 kgC m⁻² yr⁻¹ (pine) and0.138 ± 0.062 kgC m⁻² yr⁻¹ (beech) and N₂O source of0.285 ± 0.125 kgN ha⁻¹ yr⁻¹ (pine) and0.575 ± 0.105 kgN ha⁻¹ yr⁻¹ (beech). The European averagegreenhouse gas potential of the carbon sink was 18 (pine) and 8 (beech) timesthat of the N₂O source. Carbon sequestration was larger in the trees thanin the soil. Carbon sequestration and forest growth were largest in centralEurope and lowest in northern Sweden and Finland, N. Poland and S. Spain. Nosingle driver was found to dominate change across Europe. Forests were foundto be most sensitive to change in environmental drivers where the driverswere limiting growth, where changes were particularly large or where changesacted in concert. The models disagreed as to which environmental changes weremost significant for the geographical variation in forest growth and as towhich tree species showed the largest rate of carbon sequestration. Pine andbeech forests were found to have differing sensitivities to environmentalchange, in particular the response to changes in nitrogen and precipitation,with beech forest more vulnerable to drought. There was considerableuncertainty about the geographical location of N₂O emissions. Two of themodels BASFOR and LandscapeDNDC had largest emissions in central Europe wherenitrogen deposition and soil nitrogen were largest, whereas the two othermodels identified different regions with large N₂O emission. N₂Oemissions were found to be larger from beech than pine forests and were foundto be particularly sensitive to forest growth.

[学科分类] 地球化学与岩石