New Zealand Land Resource Inventory (NZLRI)
Summary
The NZLRI is a spatial database containing similar information to that in the NZLRI worksheets. There are about 100,000 polygons (map units) within the NZLRI, each of which describes a parcel of land in terms of five characteristics or attributes (rock, soil, slope, erosion, vegetation). These are contained on about 400 worksheets or maps covering the whole of New Zealand. Scientists at Landcare Research are upgrading the vegetation component of the NZLRI using satellite images to identify where changes have occurred during the past 20 years or so. The NZLRI also contains very useful Land Use Capability (LUC) assessments for each of the polygons described.
Computerised Resource
New Zealand is fortunate in having access to the computerised New Zealand Land Resource Inventory (NZLRI). It is a powerful tool for managing land, planning resource use, or environmental research. The foundation layers of Landcare Research’s GIS consist of physical resource information derived from the NZLRI.
The main features are:
- An inventory of five physical factors controlling land use—rock, soil, slope, erosion and vegetation
- Land Use Capability (LUC) assessments. These are shown as map units or land ‘parcels’ that are essentially uniform with respect to physical characteristics (i.e., the factors described in 1.).
- Fundamental data layers (FDLs) which contain data for 16 key soil attributes for all New Zealand soils.
- Pastoral and forestry production parameters, plus administrative and natural boundaries.
These allow comparative land use studies within a wide range of national or regional areas.
Compiling the NZLRI Worksheets
Resource mapping begins with stereoscopic analysis of aerial photographs and satellite images. Land considered to have uniform rock, soil and slope characteristics is delineated according to surface geology, geomorphology and soils. Erosion and vegetation categories are used to further subdivide units. Extensive field work and consultation with land managers follows to check all delineated units. Following field work, the final map unit boundaries, inventory codes and LUC assessments are compiled onto a base map. Adjacent units differ in one or more inventory factors. Completed, checked maps are published as NZLRI worksheets.
Land Resource Inventory Information
NZLRI maps (or worksheets) for the North and South Islands were completed in 1979, and have since been revised and documented. The five physical factors on which Land Use Capability assessments were made are:
Rock Type - mapped using a classification that groups rock types on the basis of common physical characteristics relevant to soil conservation and land use planning.
Soil - information adapted from publicly available soil surveys produced by Landcare Research(and its predecessor organisations).
Slope - slope is recorded as seven different classes from A–G, G being all land >35°. Erosion - mapped using 14 erosion types together with an assessment severity on a scale of 0–5.
Vegetation - vegetative cover recorded as sub division of five main groups: croplands, grassland, forest, scrub, miscellaneous.
Within each map unit the five inventory factors are set out as a code:
| For example: | Gw - 124 - F 1sSl - PIMI |
Rock - Soil - Slope Erosion degree and type - Vegetation |
||
Gw 124 F 1sSl PIMI |
= = = = = |
Greywacke (indurated sandstone) Ruahine stony silt loam Slopes between 25° and 35° slight soil slip erosion (edition 2 code =1Ss) improved pasture with manuka scrub. |
||
Land Use Capability Assessments
In addition to the inventory code described above, each map unit also contains a coded Land Use Capability (LUC) assessment of the land’s capacity for sustained productive use taking into account physical limitations, soil conservation needs and management requirements. Land Use Capability assessment, while being extremely versatile in its applications, is only one of many interpretations that could be based on the land inventory information. This assessment should not be confused with recommended land use or present land use. The Land Use Capability assessment has three basic components—class, subclass and unit. Class is the most general, classifying land from I (the most versatile and productive class) to VIII (the class with most limitations to use). Subclass groups units with the same kind of limitation or hazard. Only the dominant limitation is recorded in symbol form on the worksheets, but other limitations are recorded in the land use capability extended legend.The four kinds of limitations recognised are
| e | erodibility | c | climate |
| w | wetness | s | soil limitation within the rooting zone |
The Unit, which is represented by a number, indicates the particular LUC and denotes similar management and conservation requirements.
Extended Legends and Descriptive Publications
LUC Extended legends for each of the LUC Regions, published after completion of the maps, provide interpretive data relating to the key physical characteristics, present and potential use for cropping, grazing and forestry, fertiliser requirements, erosion potential, and soil conservation and water management requirements. These extended legends make the worksheets very useful as a wide-ranging land management tool. A number of descriptive publications describing the rock type, erosion, and vegetation classifications used in the NZLRI useful supplements to data users. These are available through Manaaki Whenua Press (see below).
Computer Database
Information on the worksheets is also recorded in a computer database from which data can be retrieved as tables, graphs, or maps. The location, shape, area and inventory code and LUC for each of the 107,000 map units is stored along with selected data from the extended legend. The database allows rapid access to, and manipulation of , the data. For example, the 46,000 map units described in the South island can be examined for a particular class of land falling within a certain slope range, in just four seconds.
Soil Fundamental Data Layers (FDLs)
Through a consultation process with stakeholders, 16 key soil attributes were selected to be included in the FDLs. The attributes generally fall into three groups: soil fertility/toxicity; soil physical properties—particularly those related to soil moisture; and topography or climate and 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,profile total available water, profile readily available water, drainage , and macro-pores (shallow and deep).
Regional soil databases were the key to generating the soil FDLs. New Zealand was subdivided into several geographic regions and soil scientists were allocated a region for which they developed a “regional legend” (regional database). The task of building the FDLs was done in three steps: correlating soil units within regions using the New Zealand Soil Classification (NZSC) and assigning all soils identified in the NZLRI to soilforms; relating site, physical, and chemical attributes to each soilform by referencing the National Soils Database and other relevant data sources; linking the soilforms and their attached attributes to the soil polygons in the NZLRI.
How can NZLRI be used?
Inventory, land-use capability or legend information can be used in planning at national, regional, district and catchment levels. On a national level, for example, Electricorp via a consortium of consultants, used the NZLRI to plan a corridor for routeing new transmission lines. NZLRI was used because it was the only complete computerised land database for New Zealand. Planning the corridor required accessing NZLRI information on potential erosion, rock type, LUC class, slope and vegetation cover for 10 million hectares, from Otago to Auckland. Thousands of work hours were saved using NZLRI.
At a regional level, an innovative study of Taranaki sustainable land used for land-use monitoring purposes was developed from the NZLRI and LUC information. Slope and aspect were identified as key factors determining sustainability. Many district councils have incorporated NZLRI data into their district scheme. Remapping at more detailed scale of 1:50,000 is making the material even more useful to local authorities.
For data or technical information:
 | Peter Newsome Email  |
Landcare Research | |
Phone: +64 6 353 4800 |
 | Ian Lynn Email |
Landcare Research | |
Phone: +64 3 321 9999 |
 | James Barringer Email |
Landcare Research | |
Phone: +64 3 321 9999 |
For copies of worksheets and related publications:
Manaaki Whenua Press
c/- Landcare Research
PO Box 40, Lincoln 8152
Ph (03) 325 6700 fax (06) 325 2127
Email
http://www.mwpress.co.nz