Functional Group Representation Research Articles

Effects of Species Richness on Resident and Target Species Components in a Prairie Restoration

Abstract The ecological role of biodiversity in achieving successful restoration has been little explored in restoration ecology. We tested the prediction that we are more likely to create persistent, species‐rich plant communities by increasing the number of species sown, and, to some degree, by varying functional group representation, in experimental prairie plantings. There were 12 treatments consisting of 1‐, 2‐, 3‐, 4‐, 8‐, 12‐, and 16‐species mixtures of native perennials representing four functional groups (C4 grasses, C3 grasses, nitrogen‐fixing species, and late‐flowering composites) that predominate within Central Plains tallgrass prairies. In 2000, species were seeded into square plots (6 × 6 m), with five replicates per treatment, on former agricultural land. Annually, we measured total species richness and evenness, target species richness and cover, and richness and cover of resident species (i.e., those emerging from the seed bank). Both target species richness and rate of establishment of target communities were highest in the most species‐rich mixtures, but there was no additional benefit for treatments that contained more than eight species. Richness of resident species did not vary with target species richness; however, cover by resident species was lower in the higher target species treatments. Our results, indicating that establishment of species‐rich prairie mimics can be enhanced by starting with larger numbers of species at the outset, have implications for grassland restoration in which community biodiversity creation and maintenance are key goals.

Experimental Manipulation of Restoration Barriers in Abandoned Eucalypt Plantations

Abstract Expansion of the nature conservation estate in northeastern New South Wales, Australia, has captured weed‐infested timber plantations amid a mosaic of high conservation value lands. We adopted a state‐and‐transition approach to test the hypothesis that restoration barriers restrict the natural regeneration of native species in Eucalyptus grandis plantations infested by Lantana camara in Bongil Bongil National Park, New South Wales. Plantation tree thinning and weed control were applied in factorial combination at three sites (totaling to 4.5 ha). Topsoil chemistry responses to these interventions were attributable to the “ash bed” effect, with temporary increases in topsoil pHW and nitrate, particularly where canopy reduction was greatest. Other soil changes were minor, indicating that thinning and burning did not risk soil degradation. Plant species richness and functional group representation in the regenerating understorey were improved by the interventions. Regeneration of native potential canopy trees, understorey trees, shrubs and woody climbers, and perennial forbs all increased with canopy retention. Grass cover dominated the regeneration where canopy cover was less than 50%. In the absence of weed control, the cover of introduced shrubs increased with reduction in canopy cover, as did the rate of understorey regeneration generally. These responses indicate that thinning and weed control can reinstate succession, leading to structurally and compositionally diverse forest. Given the abundance of native woody regeneration under retained canopy, the lantana understorey was more important in inhibiting native regeneration. The experimental approach will promote efficient use of resources across the remaining 200 ha of low conservation value plantations in this national park.

Assembly rules for functional groups of North American shrews: effects of geographic range and habitat partitioning

We examined the representation of shrew species within assemblages at 197 sites in the southern Appalachian Mountains, USA. Assemblages were classified according to representation of functional groups, including fossorial, small epigeal, and large epigeal. Average (±SD) species richness was 2.9±1.0 and assemblages averaged 0.8 species in the fossorial and large epigeal groups and 1.3 species in the small epigeal group. Compliance with Fox's assembly rule (Fox 1987, Evol. Ecol. 1:201–213) was evaluated by dividing sites into those likely under the rule (favored) and those unlikely under the rule. The number of favored sites was compared to expected numbers of favored sites under three null models of community development, which variously incorporated observed characteristics of species in the regional pool. Number of favored sites (175 [89%]) exceeded the number found in each of 25,000 sets of assemblages simulated (P<0.00004) using algorithms that incorporated the observed species richness of each site and the observed incidences of each species. However, the number of favored sites did not differ (P=0.1054) from the number expected when patterns of allopatry and sympatry were preserved in the null model. Thus, the tendency for the equitable representation of functional groups in shrew assemblages was primarily due to the pattern of allopatry among similar species, and we believe that the striking compliance of these sites with Fox's assembly rule is largely due to structure within the regional species pool, rather than extant competitive interactions.

Atomistic Topological Indices Applied to Benzodiazepines using Various Regression Methods

The use of atomic positionally independent molecular representations of a set of benzodiazepines is shown to yield a comparable structure-activity model than the traditional physicochemical representations. The best model was produced using an artificial neural network; the results are compared with models produced by MLR, PCR and PLS. The atomistic representation compares favourably with a functional group representation and the idea of implicit information in such representations is discussed. It appears that the complex inter-relationships between elements of a simple molecular representation may be capable of encoding subtle molecular structural elements.

A Functional Group Database: A Charge Density – DARC Approach

The principle of the DARC approach of hierarchical organization is applied to a molecular electron density representation of functional groups, designed to represent some of the large-scale features of biomolecules, especially macromolecules important in biotechnology and bioinformatics. The proposed representation of the hierarchical structure of the interrelations among functional groups and other, chemically identifiable molecular moieties within a molecule, and a weighting scheme assigned to these local molecular components are justified by the internal structures of the actual fuzzy electron density distributions associated with these molecular moieties. These hierarchical relations serve as a basis for the organization of a functional group database, providing a tool for synthesis design and molecular engineering.

Longitudinal and temporal changes in functional organization of macroinvertebrate communities in the Lam Tsuen River, Hong Kong

The functional organization of macroinvertebrate communities along the Lam Tsuen River, New Territories, Hong Kong, was investigated in 1976 and 1978–79. Longitudinal changes in functional group representation in 1976 generally matched those predicted by the River Continuum hypothesis, although shredders were poorly represented in the headwaters. This could be attributed to a lack of shading and limited allochthonous inputs from the scrubland watershed.