Appendix 1
Summary of riparian zone functions
| Key riparian zone functions | Explanatory notes |
| Stream bank stability | The root systems of trees and grasses strengthen streambanks and groundcover reduces surface erosion – provides habitat stability in the form of refuges during floods. |
| Filtering overland flow | Surface roughness provided by grassy vegetation, or litter, reduces the velocity of overland flow, enhancing settling of particles. High infiltration of uncompacted soils encourages subsurface flowpaths, with resulting particulate filtering and nutrient uptake by plants and microbes. |
| Fish spawning habitat and fish cover | Inanga spawn amongst herbs and grasses near the upper edge of the salt wedge (usually Jan-May). Tree roots, overhanging branches and woody debris provide key habitat (hiding & resting places) for a wide variety of fish and for crayfish. |
| Suitable habitat for adult phases of stream insects | Some stream insects spend extended periods (weeks – months) as adults in the terrestrial area. Riparian vegetation may be a key element of these species ability to persist in pastoral streams. (e.g., humidity, temperature, food resources) |
| Shade for stream temperature | Removal of shade can result in summer temperatures that can be lethal to some invertebrates and fish, or winter temperatures that are too warm for successful trout spawning. |
| Shade for instream plant control | Shade removal provides light for instream plant growth, sometimes resulting in streams becoming choked and/or variations in dissolved oxygen and pH that stress invertebrates and fish. |
| Woody debris and leaf litter input | Riparian trees add leaf litter and wood that are an important source of habitat diversity for invertebrates and fish, particularly in silt-bed streams. Leaf litter is also a food resource for stream invertebrates. |
| Plant nutrient uptake from groundwater | Roots of riparian plants intercept groundwater reducing nutrient input to streams. |
| Denitrification N Control | Denitrifying bacteria can remove substantial quantities of nitrate from groundwater passing through riparian wetlands, venting this to the atmosphere as nitrogen gases. |
| Control of direct animal waste input | Preventing direct access of stock to waterways prevents hoof-damage to streambanks and direct input of nutrients, organic matter and pathogens in dung and urine. |
| Downstream flood control | Well-developed riparian vegetation increases the roughness of stream margins, slowing down flood-flows. This reduces the peak flows downstream but may result in some local flooding. Riparian wetlands provide temporary storage of water during rain events. |
| Terrestrial biodiversity | Riparian zones contain a high diversity of soil and water conditions, resulting in correspondingly diverse terrestrial plant and animal communities |
Contact for Enquiries
MAF Information Services
Pastoral House
25 The Terrace
PO Box 2526
Wellington, NEW ZEALAND
Fax: +64 4 894 0721
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