Soil intactness assessment of the Waikato region: 2003
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Report: TR 2003/14
Author: Dr Douglas Hicks, Ecological Research Associates
Waikato Regional Council commissioned a survey to assess soil intactness (soil disturbance and bare soil) in the Waikato region using a point sampling assessment of aerial photographs flown in 2002.
The survey and a final report were completed by September 2003. In August 2005 additional analysis of bare ground was carried out using an improved cluster sampling technique. The survey developed an innovative method to interpret orthophotos (aerial photographs rectified to fit a map grid) on-screen using a Geographic Information System (GIS) with direct entry of data to a GIS-linked database.
The survey estimates soil disturbance and bare soil from land use activities and natural erosion processes across the region. Additionally, measures of bare soil under naturally occurring and planted primary and secondary vegetation cover (including soil conservation) indicate land use pressures and responses to soil intactness.
The point sample is sufficiently representative to draw conclusions about soil intactness/disturbance region wide, for land uses within the region and for large subdivisions of the region such as districts. An additional analysis has been carried out for the Coromandel catchment management zone. This has enabled a procedure to be worked out for future sub-regional analyses. The results furnish some useful examples of what can be extracted from such surveys.
Soil Intactness Assessment of the Waikato Region: 2003
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|1.4||What has been recorded||13|
|1.5||Data storage, statistical analysis and data presentation||16|
|2||Survey results - soil intactness and disturbance||19|
|3||Survey results - land use impacts on soil||19|
|4||Survey results - secondary vegetation||26|
|5||Survey results - vegetative soil conservation measures||32|
|6||Conclusions about state of the Waikato's soil||39|
|Technical conclusions about survey method||44|
|Use of orthophotos||44|
|Representativeness of results||44|
|Calibration of data for sample point size and cluster analysis of bare soil||45|
|Procedure for extracting regional subsets||45|
|Appendix I: Field check of randomly selected sample points||49|
|Type of disturbance||50|
|Overall comments on photo-interpretation error||50|
|Appendix II: Calibration of data for sample point size||52|
|Appendix III: Cluster analysis of fresh soil disturbance under various soil conservation covers||56|
|Appendix IV: Procedure for extracting regional sub-sets||59|