Characterising and understanding swampy meadows in the NSW Central Tablelands region: a prerequisite for their restoration

Abstract

This thesis was a multidisciplinary examination of the swampy meadow landform system with particular relevance to the New South Wales Central Tablelands. The research investigated the swampy meadow on many scalar and modal levels, from global scale systematics, through to regional historic reconstruction and prediction of their distribution, and finally to a valley-scale examination of the geomorphic, hydrogeological, and ecological attributes of a near natural spring-fed swampy meadow. The research was premised on the likelihood that the findings would be pivotal to swampy meadow restoration theory and practice. Swampy meadows, characterised by non-incised, discontinuous channels vegetated with dense tussock grass, sedges and rushes, were once common in the region. The impacts of European land-use have, however, contributed significantly to their widespread and rapid degradation. The detrimental affects of swampy meadow degradation are increasingly being recognised by scientists and resource managers and have led to a heightened sense of the need for their restoration, management and conservation. While swampy meadow evolution, form and function are relatively well understood geomorphically, there is a paucity of multi-disciplinary knowledge, particularly in relation to their ecology and hydrology. The research undertaken in this study followed many lines of enquiry. First, an examination of the systematics and nomenclature used to describe the swampy meadow found that the use of many different terms creates confusion, and the lack of a precise definition very likely limits knowledge transfer. The inadequate definitional status of swampy meadows also hinders our ability to protect and restore these landforms within the current legislative framework. A more precise taxonomic definition of the swampy meadow was constructed by considering their geomorphic, hydrologic, ecologic and evolutionary characteristics. An attempt was also made to reconstruct the distribution and characteristics of the swampy meadow in the Central Tablelands using both historic documentation and a gradsect sampling of 70 swampy meadows. It became evident that, at the time of early European settlement, problems with landform recognition and a general lack of a perceived necessity to record swampy meadow-type features, resulted in scant and often unreliable recordings. The contemporary analyses of the swampy meadows sampled indicated there is a high variance in environments suitable for their development, and a high degree of swampy meadow heterogeneity in the region. Therefore, based on these data, predicting where swampy meadows are likely to occur or would have occurred prior to European settlement remains a very imprecise science. What swampy meadows all have in common, however, is that they develop in a low energy environment and one which maintains permanent or periodically high soil moisture. Further, to test theories, provide descriptions and generate theories of how swampy meadows may function in a natural landscape, a natural spring-fed swampy meadow was used as a case study. Based on piezometer readings, soil logs and vegetation transects, a major finding to emerge was the high degree of heterogeneity and complexity observed in the spring-fed system in relation to its hydrogeological, ecological and physical characteristics. The small scale variability of groundwater movement, coupled with the complexity of valley sediments and their differential permeabilities, makes any spatio-temporal prediction of groundwater behaviour and soil water status difficult. Another major finding which is important for our understanding of ecosystem resilience and recovery is that the plant communities in this swampy meadow are dominated by only a few species that are both abundant and have high constancy. It is reasoned that plant life-form and function contribute more towards ecosystem stability, organic matter accumulation, and sediment aggradation than do species diversity. Finally, in a time of climate uncertainty and shortages of available water, restoring the hydrological functioning of swampy meadows is imperative. It is suggested that for the effective and appropriate restoration of swampy meadows, a review and an amendment of the current policies and legislation is warranted. As well, due recognition of the hydro-biophysical characteristics of the swampy meadow needs to be given in the definition, and a greater multi-disciplinary understanding of the complexity and heterogeneity of the landform is required.