Joe Walker

Linking restoration and ecological succession

Preface Contributors List Glossary Forging a New Alliance Between Succession and Restoration.- Insights Gained from Succession for the Restoration of Landscape Structure and Function.- Aboveground-Belowground Linkages, Ecosystem Development and Ecosystem Restoration.- Retrogressive Succession and Restoration on Old Landscapes.- Succession and Restoration of Drained Fens: Perspectives from Northwestern Europe.- Manipulation of Succession.- Restoration as a Process of Assembly and Succession Mediated by Disturbance.- Integrating Restoration and Succession.- Index.

Forging a New Alliance Between Succession and Restoration

1. Succession and restoration are intrinsically linked because succession comprises species and substrate change over time and restoration is the purposeful manipulation of that change. 2. During succession both orderly and unpredictable patterns emerge but some general rules offer theoretical and practical insights for restoration activities. These insights are not often utilized due to inadequate communication and a misconception that because restoration is focused on shorter temporal scales and is more goal-oriented, then concepts from succession may not apply. 3. Restoration potentially offers succession practical insights into how communities assemble, but a dearth of scientific protocols in the conduct of restoration has hindered this linkage.

A physiologically based continuous-time Markov approach to plant growth modelling in semi-arid woodlands

Abstract A model for simulating the combined effects of water, light and nutrients on tree, shrub and grass growth in a semi-arid woodland is described. Continuous-time Markov (CTM) assumptions are used to derive a plant growth model based on general resource availability. Physiological interpretation of states and transitions facilitates the use of the abstract continuous-time Markov approaches. The model treats resources as an interacting group, and provides an approach by which a single equation can be used across all growth forms. Simulation results for a range of leaf areas and diameters for trees, shrubs and grasses agree with field observations. The poor relationship between leaf area and diameter of plants observed in intact semi-arid woodlands is interpreted as a consequence of competitive interactions for resources.

Simulation of two-dimensional point patterns: application of a lattice framework approach

Abstract Generating a spatial pattern of points is essential in many ecological studies. Succession models require initial spatial distributions as do models of radiation interception and reflection by vegetation canopies. Several methods are available in the literature for generating a range of point distributions, however, no single method presents a workable procedure for generating two-dimensional patterns along the continuum from regular to clumped. Here we present a simple model which is capable of generating a range of two-dimensional point patterns from regular through Poisson to clumped. In this study we use a density parameter λ in conjunction with a ‘randomness’ parameter η to generate point distribution about a regular lattice base. The randomness parameter, η, varies between Pλ = (e−λλλ)/λ! and ∞. As η increases above 1, a clumped point distribution is generated, while η = 1 generates a random (Poisson) distribution. As η approaches Pλ, increasingly regular pattern results. Displacement of points from the lattice base are modified for values of η The method is shown to produce the required range of point distribution from regular to clumped using the Clark and Evans test.

Soil wetness as an indicator of stream salinity: a landscape position index approach

Abstract Dryland salinity is a major environmental issue in much of Australia’s agricultural lands and is expressed as salt affected land or degraded stream water quality. Maps showing areas at risk of land and stream degradation are needed by regional, state and national management and planning authorities, as well as farmers. Part of the management involves establishing end-of-valley targets for water quality. Developing maps of salinity risk is limited by the availability of appropriate spatial data. Elevation data at appropriate scales are available for all Australia. This paper explores the potential to develop catchment and regional scale soil wetness maps, based only on elevation data, as a surrogate for stream salinity risk. Soil wetness indices were derived through the Fuzzy Landscape Analysis GIS (FLAG) model. While FLAG avoids the direct use of process models it uses process understanding. It does this through an index-based approach that requires a training set of areas of wetness, salinity or other attribute associated with position in the landscape. We test whether only one of the FLAG landscape position indices (UPNESS), that has been shown to characterise depositional zones, is correlated to baseflow stream salinity. UPNESS is the uphill area monotonically above each point in the landscape, and is a specialised form of contributing area, a measure of surface and sub-surface water accumulation. This measure characterises catchments as the ‘connectedness’ of drainage or prevalence of runoff sinks. It distinguishes, for example, between freely drained catchments and those with more extensive depositional zones that allow the accumulation and storage of salt and formation of preferential pathways in the system. FLAG analysis was applied over an area of ~12 000 km 2 in southeastern Australia where salinity research was being conducted by state agencies. Stream electrical conductivity measurements were obtained to compare with the UPNESS index. The results suggest that the model is useful for targeting further investigations in regional scale salinity management planning and research. FLAG is suggested as a first step for obtaining a highly visual rapid assessment of potential wetness, discharge and salinisation at catchment scales.