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Combining nutrient balance models and site maps as a basis for sustainable forest biomass production

Project Leader

Katzensteiner Klaus, BOKU Project Leader

Duration:

01.05.2009-01.05.2010

Type of Research

Applied Research

Staff

BOKU Research Units

Institute of Forest Ecology

Funded by

Stiftung 120 Jahre Universität für Bodenkultur, Gregor Mendel-Strasse 33, A-1180 Wien, Austria

Abstract

The demand for forest biomass as an energy source is increasingly met by the utilization of harvesting residues. Usually, nutrient losses via harvesting of timber may be compensated by weathering of minerals and by atmospheric inputs as long as residues will remain on site. The extraction of marginal biomass dimensions: branches, twigs and leaves, both in thinning and final harvest, leads to an excessive loss of nutrients from the site. Concerns about sustainability arise, considering these additional nutrient losses by the removal of residues. Field experiments show an increment decrease of up to 20 percent in the first decades after harvesting compared to the control, where only timber had been removed. The productivity and thus the amount of nutrient removal with biomass is site dependent. The resilience of the site will be a function of the nutrient balance. Nutrient balance models are a way to assess the sustainability of forest production. Due to the high demand for input parameters to calibrate these models, their application has usually been restricted to long term monitoring and research sites. Within the proposed project, the applicability of the approach for a forest management district should be tested. A nutrient balance approach will be applied for selected site units of the BOKU-school forest at Rosalia. Basic soil analytical data are available for the site units. They will be complemented by additional analytics, in particular mineralogy of selected soil profiles. Forest growth and harvesting scenarios will be simulated by using a normal forest model based upon inventory data of the school forest. Biomass expansion factors and nutrient allocation functions will be taken from the literature and own data bases. Deposition and leaching rates will be estimated based upon ‘historic’ measurements in the school forest and time trends taken from ICP Forest Level II measurements. Mineral weathering rates will be simulated by the PROFILE model. The modeling results will be used for a vulnerability classification of forest sites and compared to less demanding classification approaches. The project will provide new approaches which should be applied in the ‘Field Course on Forest Site Classification and Yield Sciences (912 110)’ and extended for different site conditions and utilization scenarios.

Keywords

soil science; renewable resources;