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Changes in Soil Stability in the Waikato Region from 2002 to 2007

TR 2009/30

Report: TR 2009/30
Author:  A B Thompson, Thelton Environmental Ltd and D. L. Hicks

Executive summary

This report compares surveys of soil stability (intactness and disturbance) undertaken for Environment Waikato (EW) in 2003 and 2009.   Data were point-sampled from aerial photographic cover of the region in 2002 and 2007 respectively.   Both surveys were undertaken primarily to provide information about soil stability (intactness and disturbance) for state of environment reporting.

The monitoring was defined by the boundaries of the area that EW has statutory responsibility for.   Within this area, soil stability was assessed at 6122 sample points, distributed at 2 kilometre intervals on the map grid, using digital orthophotos taken for EW in 2002 and 2007.   Data recorded were land use, associated vegetation, soil stability, soil disturbance (if present), and area freshly disturbed (where present).

Changes in Soil Stability in the Waikato Region from 2002 to 2007
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Table of contents

  Acknowledgements i
  Executive summary v
1 Introduction 1
2 Methods 1
3 Report structure 4
4 Regional changes 2002 - 2007 5
4.1 Soil stability 5
4.1.1 Stable surfaces 5
4.1.2 Erosion- prone surfaces 5
4.1.3 Eroded and eroding surfaces 6
4.1.4 Extensively disturbed Surfaces 6
4.1.5 Other surfaces 6
4.2 Soil disturbance 6
4.2.1 Land-use related disturbance 7
4.2.2 Disturbance by natural processes 8
4.2.3 Other disturbance 8
4.3 Land use 9
5 Rural land-use changes 2002 - 2007 11
5.1 Cropping and horticulture changes 11
5.1.1 Soil stability amongst cropping and horticulture 11
5.1.2 Soil disturbance amongst cropping and horticulture 12
5.1.3 Contribution to regional change, 2002 - 2007 13
5.2 Dairy pasture changes 13
5.2.1 Soil stability amongst dairy pasture 13
5.2.2 Soil disturbance amongst dairy pasture 14
5.2.3 Contribution to regional change, 2002 - 2007 15
5.3 Dry-stock pasture changes 17
5.3.1 Soil stability amongst dry-stock pasture 17
5.3.2 Soil disturbance amongst dry-stock pasture 17
5.3.3 Contribution to regional change, 2002 - 2007 19
5.4 Exotic forest plantation changes 19
5.4.1 Soil stability amongst exotic forest plantations 19
5.4.2 Soil disturbance amongst exotic forest plantations 20
5.4.3 Contribution to regional change, 2002 - 2007 21
5.5 Natural forest changes 22
5.5.1 Soil stability amongst natural forest 22
5.5.2 Soil disturbance amongst natural forest 23
5.5.3 Contribution to regional change, 2002 - 2007 24
5.6 Natural scrub changes 24
5.6.1 Soil stability amongst natural scrub 24
5.6.2 Soil disturbance amongst natural scrub 25
5.6.3 Contribution to regional change, 2002 - 2007 26
5.7 Exotic scrub changes 26
5.7.1 Soil stability amongst exotic scrub 26
5.7.2 Soil disturbance amongst exotic scrub 27
5.7.3 Contribution to regional change, 2002 - 2007 28
5.8 Tussock and mountain vegetation changes 29
5.8.1 Soil stability amongst tussock and mountain vegetation 29
5.8.2 Soil disturbance amongst tussock and mountain vegetation 30
5.8.3 Contribution to regional change, 2002 - 2007 31
5.9 Wetland and coastal vegetation changes 32
5.9.1 Soil stability amongst wetland and coastal vegetation 32
5.9.2 Soil disturbance amongst wetland and coastal vegetation 33
5.9.3 Contribution to regional change, 2002 - 2007 34
6 Summary 34
6.1 Region-wide changes 34
6.1.1 Soil stability 35
6.1.2 Soil disturbance 35
6.1.3 Bare soil 36
6.2 Changes for each land use 37
  References  40