Dipl.-Geogr. Markus Tum D-82234 WesslingGerman Aerospace Center GermanyGerman Remote Sensing Data Center Tel. +49 8153 28-1292Land Surface Dynamics Fax +49 8153 28-1363

E-Mail markus.tum@dlr.de

Modelling and Validating Agricultural Biomass Potentialsin Germany and Austria using BETHY/DLR

M. Tum1, M. Niklaus1, K.P. Günther1, M. Kappas2 1German Aerospace Center (DLR), German Remote Sensing Data Center (DFD), Land Surface Dynamics

2Department of Cartography, GIS & Remote Sensing, Institute of Geography, Georg-August-University Goettingen, Germany

Statistical yield data do not represent biomass or accumulated carbon and therefore cannot be compared directly with the modelled yearly NPP sum (figure 1). Simple allocation schemes are used to calculate above and below ground biomass (table 1). Furthermore estimations of water and carbon contents of straw and yield are needed to estimate the carbon content from yield data (see formulas below).

Figure 1: Accumulated yearly sums of modelled carbon (NPP) for agricultural areas for the years 2000 and 2001. The spatial resolution is about 1km x 1km. White pixel represent areas which do not belong to the agricultural GLC2000 classes 16 or 18.

Model results (in Mt carbon): 2000: Germany: 76.4, Austria: 5.72001: Germany: 73.2, Austria: 8.0

Maximum NPP: 2000: 661 t carbon*km-2

2001: 547 t carbon*km-2

Figure 2: Correlations between modelled NPP (BETHY/DLR) and statistical yield data (Federal statistic bureaus) in kilo tons per NUTS-3 area.

underestimations for Germany (4% to 28%)

overestimations for Austria (8% to 51%)

coefficients of determination: - Germany:0.58 to 0.79

- Austria: 0.74 to 0.75

We are presenting a new approach to validate modelled Net Primary Production (NPP). Our NPP results are computed with the dynamic vegetation model BETHY/DLR (Biosphere Energy Transfer Hydrology Model). BETHY/DLR is a modification of the JSBACH model which computes the biosphere-atmosphere exchange within the ECHAM5 global climate model. Primarily the photosynthetic rate of vegetation types is computed with time steps of one hour and with a spatial resolution of about 1km². It includes modules for assessing the water balance and the radiative energy transfer between atmosphere, vegetation and soil.

The model is driven by remote sensing data sets (land cover / land use from GLC2000 and time series of Leaf Area Index (LAI)), derived from SPOT-VEGETATION, meteorological parameters provided by the European Center for Medium Range Weather Forecast (ECMWF) and soil type information by the Food and Agriculture Organisation (FAO). In order to validate the modelled NPP, crop yield estimates derived from national statistics are used to calculate above and below ground biomass by using conversion factors of corn to straw and leaf to beet relations (table 1). With this method we found coefficients of determination of up to 0.79 (figure 2).

Table 1: Corn to straw (leaf to beet) ratios and above ground to below ground ratios, carbon and water content for selected crops

yi: yield stw: strawH2O: Water content C: carbon contentagb: above ground biomass bgb:below ground biomassstw: conversion factor yi/stw agb: conversion factor agb/bgb