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A study of microorganisms in soils of the Cragieburn Range

Nordmeyer, A. H.
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ANZSRC::050302 Land Capability and Soil Degradation , ANZSRC::0503 Soil Sciences
The romance associated with mountain sports such as shooting and skiing, and the rigours of stock-management in the high-country, often clouds the fact that many mountain soils in the South Island of New Zealand are in a state of marked and widespread deterioration. The most critical problems in mountain land management exist in the area of the east of the main divide, between the Waitaki River in the south and the Wairau River in the north. This area has soils, developed on greywacke rock, which exist under a cover of (1) alpine grassland, dominated by Chionochloa pallens, Ch. rigida or Ch. australis, at over 4,000 ft above sea level (a.s.l.), (2) mountain beech (Nothofagus solandri var. cliffortioides) forest between 2,000 – 5,000 ft a.s.l., and (3) low-tussock grassland between 1,500 – 3,500 ft a.s.l. In the past, little attention has been given to the management of this mountain country as a lasting resource. It has value for grazing, water retention, forestry, and recreation but what is lacking is objective data on methods of managing the soils and the associate flora. For the plant, the mountain environment can be harsh, in terms of climate, physical soil movement and soil fertility, but from the management aspect, the only condition that can be easily modified is that of soil fertility. It is this latter aspect which impinges directly on the field of soil microbiology. If mountain soils are to be managed cheaply, and the most effective use made of the resources available, the microbiological processes going on in these soils must first be understood and then related to the ecosystem as a whole. Knowledge of the microbiology of these mountain soils is entirely lacking and yet processes of nitrogen fixation (both symbiotic and no-symbiotic), weathering, and organic-matter mineralisation could be the most important factors limiting plant growth in such soils. This study is aimed at the elucidation of the role of soil micro-organisms in the dynamics in some typical mountain soils. In Part I, an attempt is made to relate the numbers and types of bacteria to the known chemical and physical conditions of the soil; in Part II, the possible effect of micro-organisms in releasing available phosphate is considered; in Part III a study is made of some micro-organisms responsible for fixing atmospheric nitrogen in mountain soils. The following sections will include a description of the study area, its vegetation, soils, and climate and an attempt will be made to relate past studies of soil microbiology to the conditions in these mountain soils.
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