Soil type Layers

The soil fundamental data layers (FDLs) contain spatial information for 16 key attributes, each of which is measurable (i.e. is given a numeric value rather than being assigned to a descriptive class or category) and is recorded in appropriate units of measure. Since attributes have measurable values, FDLs are particularly useful in computer modelling and have enabled researchers and resource management decision-makers to make the most of rapid developments in GIS technology. Key soil attributes were selected through a consultation process with stakeholders, and generally fall into three groups: soil fertility/toxicity, soil physical properties (particularly those related to soil moisture), and topography/climate (T). Parameters include slope, potential rooting depth, topsoil gravel content, proportion of rock outcrop, pH, salinity, cation exchange capacity, total carbon, phosphorus retention, flood interval, soil temperature, total profile available water, profile readily available water, drainage, and macropores (shallow and deep).

Regional soil databases were the key to generating FDLs. New Zealand was subdivided into several geographic regions and soil scientists were allocated a region for which they developed a ‘regional legend’, i.e. database. Regional data were correlated using the New Zealand Soil Classification (NZSC), referenced to the National Soils Database (NSD) and other relevant data sources, and then linked to the soil polygons in the New Zealand Land Resource Inventory (NZLRI). This layer holds the NZSC data upon which the remaining FSLs were based.

The NZLRI is a spatial database containing about 100,000 polygons (map units), each of which describes a parcel of land in terms of five characteristics or attributes (rock, soil, slope, erosion, vegetation). This layer represents a GIS dissolve on the soil attribute of the NZLRI.