Pre-European estimate of mean annual store of mineral nitrogen (NMnl0.Base)

Of the plant-available nitrogen (N), only a small fraction is in mineral form. The rest is "in use" in biomass or "on return" through litter and soil organic matter. N storage maps strongly resemble the maps of C storage and Net Primary Production (NPP), because the N stores are coupled to C stores through well-defined (through not constant) N/C ratios in leaves, wood, roots, litter and soil organic matter. In particular, saturation deficit and temperature exert similar controls on N stores as they do on C stores, in the absence of agricultural inputs of N. Derived from the BiosEquil model by Raupach et al. (2001a; 2001b).

Soil nutrient outputs of the BiosEquil model
Nutrient status is one of the key limiting factors determining the productivity of Australian vegetation systems, but is only broadly represented by gross nutrient status an attribute compiled from the Atlas of Australian Soils (McKenzie et al. 2000). We therefore additionally compiled the 0.05°gridded pre-European (base) predictions of carbon, nitrogen and phosphorous distributions which are outputs of the BiosEquil model by Raupach et al. (2001a; 2001b). These data are available from the Australian Natural Resources Atlas at www.nlwra.gov.au/atlas. Inputs to the pre-European models included meteorological surfaces of daily gridded data at 0.05° spatial resolution (for Australia) (Jeffrey et al. 2001), soil characteristics for current conditions derived from the Atlas of Australian Soils (McKenzie et al. 2000), and vegetation characteristics (Leaf Area Index) (Lu et al. 2001). The 0.05° gridded data were resampled to 0.01° using the cubic algorithm with RESAMPLE in ARCINFO GRID. Zero values were assumed to represent NODATA values (e.g. lakes) and were iteratively filled using the DATA option of the FOCALMEAN command with a CIRCLE expand radius of 3 cells in ARCINFO GRID, as described above.