Soil Maps of Cadmium in New Zealand
3. Results and Discussion - 3.4 Representiveness of the Data
The data in the database was tested for representativeness by comparing topsoil total-cadmium concentrations and associated metadata with LCDB2 vegetation class and the number of sites per 100 square km calculated (Table 8, Figure 22).
High-producing introduced grassland had the highest number of samples (930). Short-rotation cropland was next (345) but had the highest number of sites per 100 square km (10.34). Afforestation, orchard and other perennial crops, surface mine, urban parkland/ open space and vineyard are also relatively well represented with more than 1 site per 100 square km. Depleted tussock grassland, tall tussock grassland and sub alpine shrubland are relatively poorly represented with less than 0.04 sites per 100 square km. Further sampling based on vegetation class is not required as the main farming vegetation classes are adequately covered.
Table 8: Number of sites and number of sites per 100 square km according to LCDB2 vegetation class
| LCDB2 vegetation class | Number of sites | Number of sites/100 km sq |
|---|---|---|
| Afforestation (imaged, post LCDB 1) | 9 | 1.06 |
| Broadleaved Indigenous Hardwoods | 25 | 0.46 |
| Built-up Area | 16 | 0.98 |
| Deciduous Hardwoods | 4 | 0.48 |
| Depleted Tussock Grassland | 1 | 0.04 |
| Estuarine Open Water | 2 | 0.22 |
| Forest Harvested | 7 | 0.30 |
| Gorse and Broom | 4 | 0.20 |
| Grey Scrub | 1 | 0.14 |
| Herbaceous Freshwater Vegetation | 2 | 0.23 |
| High-producing Exotic Grassland | 930 | 1.05 |
| Indigenous Forest | 79 | 0.12 |
| Low-producing Grassland | 30 | 0.18 |
| Mangroves | 1 | 0.38 |
| Manuka and or Kanuka | 26 | 0.22 |
| Matagouri | 2 | 0.68 |
| Orchard and Other Perennial Crops | 38 | 6.52 |
| Other Exotic Forest | 13 | 0.98 |
| Pine Forest – Closed Canopy | 28 | 0.29 |
| Pine Forest – Open Canopy | 6 | 0.12 |
| Short-rotation Cropland | 345 | 10.34 |
| Sub Alpine Shrubland | 1 | 0.03 |
| Surface Mine | 2 | 2.05 |
| Tall Tussock Grassland | 4 | 0.02 |
| Urban Parkland/Open Space | 8 | 1.99 |
| Vineyard | 9 | 3.54 |
Figure 22: Number of site sampled per 100 square km according to LCDB2 vegetation
Larger image [90KB JPG]
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