Tamar report land Capability Survey of Tasmania k e noble 1992 Tamar Report
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- Photo 1.
- BIOPHYSICAL FACTORS e.g Geology, Soil, Slope, Climate PHYSICAL LIMITATIONS eg. Drainage, Flooding, Stoniness, Erosion hazard
10 5. Methodology 5.1 Mapping Technique The land capability maps are produced from a combination of both field work and aerial photo- interpretation. Extensive field work along major roads has been carried out over the survey area to check soil types, soil depths, geological boundaries etc, and to assess the land capability classes. Slopes were measured in the field with an inclinometer to determine critical slopes for different soil types. Soil profiles were examined by augering or by examination of exposures along road cuttings and banks to determine depth of soil horizons and their properties. Exposures were also used to examine the underlying geology. Local agricultural advisory officers were taken in the field to assist with cropping and agricultural information. Land capability class boundaries were transferred onto aerial photographs where possible in the field, using the technique of stereoscopic interpretation (see Photo 1). In areas where access was not possible land capability boundaries were drawn after interpretation of aerial photos and other relevant available information (e.g. geology, soils and land systems maps). The land capability boundaries were then transferred onto the relevant topographic base map. Extensive field checking of the area has been carried out to check the accuracy of boundaries and the land capability assessment assigned to each area. 5.2 Aerial Photography Aerial photos used for this map have been 1982 Tamar and 1988 Central North surveys, at 1:42 000 scale.
Only Private Freehold and Leased Crown Land has been mapped (as shown on the Tasmap 1:100 000 Series). All other areas such as State Forests, State Reserves, Conservation Areas, Crown Land, and urban areas, etc., have been excluded from the mapping program. These excluded areas are indicated on the map by the letter E.
11 6. Land Capability Classification Land capability classification is an internationally recognised means of land classification, used to evaluate the capability of land to support a range of land uses, on a long-term sustainable basis. For the Tasmanian classification, agricultural land uses only are covered, and are defined as broadscale grazing and cropping uses. Land capability ratings for specific land uses are not evaluated, nor is the capability of land for forestry use incorporated into the classification system. Land capability may be defined as a rating of the ability of land to sustain a range of land uses without degradation of the land resource. It is an interpretive and somewhat subjective assessment based on the physical limitations and hazards of the land, potential cropping and pastoral productivity, and the versatility of the land to produce a range of agricultural goods (refer to Figure 1).
12 Land capability assessment takes into account the physical nature of the land (e.g. geology, soils, slope) plus other factors (e.g. climate, erosion hazard, land management practices) which determine how that land can be used without destroying its long-term potential for sustainable agricultural production. It also takes into account limitations that might affect agricultural use, e.g. stoniness, drainage, salinity or flooding. Land capability assessment is therefore based on the permanent biophysical features of the land (including climate), and does not take into account the economics of agricultural production, distance from markets, or social or political factors. Land capability assessment should not be confused with land suitability assessment which, in addition to the biophysical features, may take into account economic, social and/or political factors in evaluating the `best' use of a particular type of land. Land capability classification gives a grading of land for broadscale agricultural uses, whereas land suitability is applied to more specific, clearly defined land uses, such as land `suitable' for carrots. The land capability classification system for Tasmania gives an indication of the inherent capability of the land for general agricultural production and does not attempt to portray specific land uses, or rank the value of any particular agricultural land use above another. Neither does it attempt to give an indication of land values. The system of land capability classifies land into a number of classes according to the land's capability to produce agricultural goods (based on broadscale grazing and cropping uses). The system for Tasmania is based on the USDA (United States Department of Agriculture) approach to land capability. There are generally three levels to the land capability classification: - The land capability class - which gives an indication of the general degree of limitation to use - subclass - which identifies the dominant kind of limitation - and the unit - which groups land with similar management and conservation requirements, potential productivity, etc. The land capability system can be used and applied at various scales by mapping to the class, subclass and unit levels. The level at which the mapping is undertaken and presented depends on the purpose and scale of the survey. Yüklə 1,7 Mb. Dostları ilə paylaş:
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