In this study, the use of topographical attributes for the analysis of the spatial pattern and ecological cycle of kauri (Agathis australis) is evaluated. We try to interpret statistically the presence or absence of mature kauri in association with properties derived from elevation data. Furthermore we explore the possibilities of using terrain attributes for representing environmental conditions, relevant geomorphological processes and disturbance regimes.
Patterns of ecosystem structure, composition and function are controlled by landforms and geomorphic processes, because of their effect on environmental gradients and patterns and frequency of disturbance. Although landslides are recognized as an important mechanism of disturbance in steep terrain, digital terrain analysis to assess landsliding as a determinant of vegetation patterns has hardly been applied.
LAPSUS-LS is used to determine landslide risk in the study area. Results of this analysis are then combined with topographic attributes derived from a DEM to explain the occurence of kauri.
A topographically based landslide hazard index appears to be very useful in explaining the occurrence and ecological dynamics of kauri. It is shown that the combination of topographical, soil physical and hydrological parameters in the calculation of this single landslide hazard index, performs better in explaining presence of mature kauri than using topographical attributes calculated from the DEM alone. Moreover, this study demonstrates the possibilities of using terrain attributes for representing geomorphological processes and disturbance mechanisms, often indispensable in explaining a species’ ecological cycle. The results of this analysis support the ‘temporal stand replacement model’, involving disturbance as a dominant ecological process in forest regeneration, as an interpretation of the community dynamics of kauri. Furthermore a threshold maturity stage, in which trees become able to stabilize landslide prone sites and postpone a possible disturbance, together with great longevity are seen as major factors making kauri a ‘landscape engineer’.
Although not primarily intended for prediction of presence of kauri, the method used could be adopted to delineate favourable sites or areas for possible kauri forest regeneration and could accordingly be used for nature conservation planning in areas similar to the study area.
Claessens, L., Verburg, P.H., Schoorl, J.M., and Veldkamp, A., 2006, Contribution of topographical based landslide hazard Modelling to the analysis of the spatial distribution and ecology of Kauri (Agathis australis): Landscape Ecology 21, p. 63 - 76.
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