Lee Belbin

Compositional dissimilarity as a robust measure of ecological distance

The robustness of quantitative measures of compositional dissimilarity between sites was evaluated using extensive computer simulations of species’ abundance patterns over one and two dimensional configurations of sample sites in ecological space. Robustness was equated with the strength, over a range of models, of the linear and monotonic (rank-order) relationship between the compositional dissimilarities and the corresponding Euclidean distances between sites measured in the ecological space. The range of models reflected different assumptions about species’ response curve shape, sampling pattern of sites, noise level of the data, species’ interactions, trends in total site abundance, and beta diversity of gradients.

Environmental representativeness: Regional partitioning and reserve selection

Abstract There is a need to identify and reserve representative areas of national ecosystems. Biological databases available at such a broad scale may be inadequate for this purpose. The success of climatic and edaphic factors in modelling a range of species distributions suggests that these variables may be effective in identifying ecosystems. A classification procedure is proposed that results in an environmental regionalisation and the assignment of values of environmental representatives. These values can be mapped to establish or evaluate reserve networks.

Semi-strong Hybrid Scaling, a new ordination algorithm

. There is a small group of association measures that appear optimal for comparing sites on the basis of their species composition. These measures can accurately estimate affinity between sites when they are ecologically similar. Once sites share few or no species, these measures always under-estimate the ‘ecological distance’ between them. A new ordination algorithm called Semi-strong Hybrid Scaling, SHS, uses these features in an attempt to provide a better configuration of the sites. The new method is evaluated by a direct comparison of the structure in simulated data with the Hybrid method of Faith, Minchin & Belbin (1987). To evaluate SHS and compare it with Hybrid Scaling, 3240 datasets were generated using the COMPAS simulator (Minchin 1987). The data were designed to simulate as closely as possible, what is known of the distribution of species on environmental gradients. The factors included the dimensionality of the data, the number of sites and species, the shape of the species response surfaces, positioning of the sites in the simulation space, carrying capacity and level of noise. Recovery of the simulated site positions by SHS and Hybrid Scaling was evaluated using Procrustes rotation. SHS produced a better recovery in 88% of the datasets.

Comparing three classification strategies for use in ecology

We compare three common types of clustering algorithms for use with community data. TWINSPAN is divi- sive hierarchical, flexible-UPGMA is agglomerative and hierarchical, and ALOC is non-hierarchical. A balanced de- sign six-factor model was used to generate 480 data sets of known characteristics. Recovery of the embedded clusters suggests that both flexible UPGMA and ALOC are signifi- cantly better than TWINSPAN. No significant difference existed between flexible UPGMA and ALOC.

Selecting representative reserve systems in remote areas: A case study in the Nullarbor region, Australia

Abstract We present a procedure for the selection of a network of reserves representing the biological diversity of a large and biologically poorly known region. The quantitative analysis gives equal weighting to a wide array of different species: mobile and sessile, long-lived and ephemeral, heterothermic and homeothermic, etc. Sampling was based on quadrats that were positioned through the region using a stratified random strategy. This provided a presence-absence matrix of the species composition at each quadrat. Numerical pattern analysis was used to identify 14 species assemblages and to re-order the sites and species in the data matrix. The geographic pattern of each assemblage throughout the region was described by contouring assemblage richness, the isolines being the proportion of the number of species in each assemblage. The data matrix was re-examined. Some assemblages exhibit several gradients in species composition. For example, a 0·1 isoline in the east may represent a different 10% of species than a 0·1 isoline in the west. Other assemblages exhibit only a single gradient in species composition. The results were used to select the optimum positions of reserves needed to represent the compositional diversity of each of the 14 species assemblages. Limited field checking confirmed the predicted isolines in assemblage compositional richness to a satisfactory extent.

Integrating conservation and forestry production: exploring trade-offs between biodiversity and production in regional land-use assessment

Abstract Regional integration of biodiversity conservation and forestry production requires land-use allocations based on trade-offs that attempt to maximise long-term net benefits to society. In this context, effective surrogate information for biodiversity must be used in order estimate the complementarity value of each area—its unique contribution to biodiversity, given other already-protected areas. Net benefits will be maximised only when the complementarity value for each protected area exceeds its weighted cost or suitability for an alternative land use. This study explored this issue using one particular surrogacy approach, based on environmental data, combined with a recently-developed procedure that incorporates biodiversity assessment into a multi-criteria analysis framework. This procedure, as implemented in a software package DIVERSITY, allows the study of a range of relative weightings on biodiversity protection versus suitabilities for alternative land uses, identifying sets of protected areas that maximise total net benefit. A case study integrating biodiversity and forestry production in the Batemans Bay region of New South Wales, Australia, is presented, in which the suitabilities for forestry are estimated using a spatial decision-support package, LUPIS. LUPIS is linked to the DIVERSITY package in order to combine exploration of different weightings on various forestry-related criteria with weightings on biodiversity. The results demonstrate that, relative to biodiversity allocations that ignore competing land-uses, taking trade-offs into account can lead in principle to an allocation of protected areas that maintains a high degree of biodiversity representation while reducing conflict with forestry requirements.

A Comparison of Two Approaches to Beta-Flexible Clustering

We introduce a UPGMA based counterpart to the Lance and Williams (1966) p-flexible clustering strategy. This new method is compared with the original p-flexible technique based on WPGMA for a range of fl values from -0.8 to +0.1. Recovery of the known cluster structure from simulated data was evaluated using the Hubert and Arabie (1985) version of the Rand statistic. The algorithm used to generate the simulated clusters in the study included error-free data as well as three other error conditions. The simulated data also varied the number of clusters, the underlying dimensionality, and the density distribution of points to the clusters. Results showed that the flexible UPGMA gives the best recovery for all generated data configurations. Further, the flexible UPGMA method with a small negative β value performed better than the standard UPGMA method where β is set equal to zero. The flexible UPGMA strategy, employed with a narrow β range, is recommended based upon its ability to recover cluster structure over all error conditions.

Grassland dynamics under sheep grazing in an Australian Mediterranean type climate

Grassland dynamics in a degraded disclimax grassland dominated by Danthonia caespitosa Gaudich. are examined using both demographic and multivariate approaches in an experiment designed to determine the effect of grazing intensity and exclosure on pasture dynamics. The experiment ran for 20 years from 1949 to 1968, using permanent quadrats at 3 grazing intensities and within exclosures. Demographic studies of some perennial grass species demonstrated markedly different responses to grazing; Danthonia caespitosa was unaffected by grazing but responsive to seasonal rainfall differences. Enteropogon acicularis survived only on protected sites. Numerical classification of total species set (121 species) for six observation periods demonstrated that community types were sensitive to differences in winter rainfall, and time since the start of experiment. Principal component analysis of permanent quadrat observations for individual years demonstrates quadrat trajectories which confirm this and indicate progressive divergence of the successional trends of the grazed and ungrazed quadrats. Repeated analysis on grazed quadrats only, shows that three components of pasture dynamics can be recognized; these are trend (succession?) and seasonal differences, each of which account for about 20% of the variance, and differences due to soil heterogeneity in the experimental paddock (8% of variance accounted for). No effect of grazing intensity was detected. Multivariate techniques can provide a clear partitioning of types of dynamic behaviour present in grassland communities. It is concluded that partitioning of environmental heterogeneity prior to demographic studies would increase their sensitivity.

A multivariate approach to the selection of biological reserves

Multivariate analysis provides an effective context for the examination of some significant aspects of biodiversity and conservation. The framework is a multidimensional space that integrates sample sites, taxa and environments. This approach enables terms such as representativeness, complementarity and irreplaceability to be integrated within an intuitive and practical framework for reserve design. Cluster analysis is proposed to determine ‘what is there’ by defining a set of complementary clusters. These clusters are sampled in a representative manner; from the core outward. The degree of irreplaceability of a site is defined as the multivariate distance of each potential reserve site to its nearest neighbour.

Land use allocation and biological conservation in the Batemans Bay Forests of New South Wales

Summary Data on native forest cover within a 3500 km2 area of the Batemans Bay region, south-east New South Wales, were analysed in relation to a number of factors: land tenure, site productivity, accessibility (distance to nearest human habitation), the distribution of 31 forest tree (predominantly eucalypt) associations, and the extent of disturbance from logging and clearing activities. There were 11 tenure classes. To simplify analyses and presentation the tenure classes were lumped to three tenure categories that reflect likely forest management or land use practice: National Park (19.3% by area—preserved or protected forest), State Forest (47.5%—forest allocated to timber production), Freehold (33.2%—forest potentially available for clearing for agricultural, pastoral, semi-urban, etc. land use). Tree associations that characterised the most productive sites and, on average, the most accessible land were; (i) well represented in Freehold tenure, (ii) least represented in National Park and, (iii) mos...