Applying a land systems approach to describe and partition soil and forest variablility, Southern Mamaku Plateau, part of Kinleith Forest, New Zealand

• Main Author: Hill, Reece B
• Format: Dissertation
• Language: English

Content Partner: Lincoln University. Kinleith Forest is a P. radiata dominated plantation forest situated on the edge of the Taupo Volcanic Zone in the central North Island, New Zealand. Approximately 35 000 ha of the forest is situated on the southern Mamaku Plateau. The aim of this study was to determine the spatial structure of soil variability and integrate an analysis of the growth, productivity and nutrient variables for P. radiata to ascertain the detail of soil information appropriate for plantation forestry. A land systems approach, using generic and specific soil-landscape models and hierarchical landscape analysis, provides the framework for soil mapping. The approach is scale-flexible and lends itself to implementation of site specific forest soil, nutrient and health management practices. The southern Mamaku Plateau consists of five superimposed Late Quaternary welded ignimbrites with the Mamaku Ignimbrite (c. 220 ± 10 ka) being the uppermost. Aeolian coverbeds consisting of predominantly loess and rhyolitic tephras mantle erosional surfaces formed in ignimbrite bedrock. Four episodes of strath cutting and valley incision into ignimbrite are recognised from the sequence of overlying loess and tephra coverbeds. The basal loess and/or tephra on the erosion surfaces denoting the cessation of each episode of strath cutting and valley incision are: (a) pre-Rotoehu loess, (b) pre-Kawakawa loess, (c) Rotorua Tephra, and (d) Taupo Ignimbrite. The four episodes of strath cutting and valley incision can be synthesised into five topographically recognised stages of landform evolution. Landform evolution stage (I) is represented on the upper Mamaku terrain and stage (V) on the lower Mamaku terrain. In a revised coverbed distribution model the oldest coverbed sequence is recognised on hill and terrace land components on the upper and lower Mamaku terrain. The coverbed stratigraphy together with its soil stratigraphic interpretation and soil-landform relationships has been used to map nine land systems. Soil-landscape relationships and forest variability are described and analysed within the U3 complex land system. The U3 complex land system comprises Oruanui and Mamaku simple land systems, each with a common recurring pattern of hillock, ridge, flat and ravine land components, situated on the upper Mamaku terrain. Soil and regolith variables were partitioned at progressively finer levels of hierarchical landscape subdivision to ascertain spatial variabilit