Partitioning Direct and Indirect Human-induced Carbon Sequestration in Managed Conifer Forests in Central Europe Using Model Simulations and Forest Inventories.
Abstract
Forest ecosystems have long been known to be an important sink in the global carbon budget. The factors responsible for the strength of the sinks and their permanence, however, are not so clear. To distinguish between direct and indirect impact on the carbon sequestration we have to work on spatial and temporal scales where humans have a major impact on the ecosystem. In this paper we contrast the effects of indirect human induced environmental changes and forest age on carbon sequestration as well as direct human induced effects on carbon accumulation such as forest management of coniferous forests in central Europe from the end of 19-th century until present. Ecosystem process model BIOME-BGC has been used to study these effects and results have been corroborated with forest inventories. We focused on conifer forests of Thuringia as a study case, because these forests are representative of central European forests and good forest inventories were available. Grouping the forests in three different strata differing in annual average temperatures and precipitation allowed us also to study the effect of elevation on carbon sequestration. Forests in all elevational strata showed an increase in vegetation carbon accumulation in all age classes as a result of environmental changes in the last 20 years (1982-2001). Young and old trees had the highest annual changes in the vegetation carbon during this period. Under pre-industrial conditions, trees older than 80 years showed almost no annual increase in vegetation C carbon accumulation. With industrial climate scenario those trees were still carbon sinks. Trees older than 100 years in the low elevations were an atmospheric carbon source in the pre-industrial case, but carbon sinks in the industrial case. Nitrogen-deposition had the highest impact on the net ecosystem production (NEP) for the high and middle elevations, whereas CO2 fertilization was most responsible for NEP changes in the low elevations. Under current environmental conditions, the total modeled carbon accumulation in the coniferous forests of Thuringia was estimated at 2.09 t C ha-1y-1 with an averaged annual NEP of 1.78 t C ha-1y{-1} and net biome production (NBP) of 1.12 t C ha-1y-1. Once corrected with the actual forest harvest statistics, the modeled NBP estimate was reduced to 0.83 t C ha-1y-1. Under pre-industrial conditions the NBP estimates were 0.43 and 0.15 t C ha-1 y-1 respectively. The environmental changes led to the sink strength of 62% or 82% depending on how the harvest was estimated. Based on the estimates of annual accumulated vegetation carbon (NBPVEG), the forest inventory data gave NBPVEG varying from 0.45 to 2.6 t C ha-1y-1 depending on the method used for estimating the wood increments. The modeled NBPVEG was estimated at 1.42 t C ha-1y-1. Environmental changes or indirect human impact resulted in 44% increase in modeled vegetation carbon accumulation of conifer forest in Thuringia. From the forest inventory data we estimated the effect of changing area of the forest age classes, or the direct human impact on the carbon sequestration, to be approximately 37%.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2003
- Bibcode:
- 2003AGUFM.B52D..02V
- Keywords:
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- 0315 Biosphere/atmosphere interactions;
- 0400 Biogeosciences;
- 1615 Biogeochemical processes (4805);
- 9335 Europe