PARENT SESSION
Contributed Oral Session 51: Arid Land Management, Vegetation, and Nutrient Dynamics
Tuesday, August 9, 8:00 AM - 11:30 AM, Meeting Room 522 A, Level 5, Palais des congrès de Montréal
Predictive models of plant species richness from an Australian mountainous desert.
van Etten, Eddie 1, 1 Edith Cowan University, Perth, W.A., Australia
ABSTRACT- Local species richness can often varies widely across landscapes. The Hamersley Ranges, an arid mountain region of north-west Australia, is no exception with local richness of perennial plant species varying between 4 to 50 per 0.05 ha plot. Predictive modelling of such richness in relation to environmental variables may shed light on factors and processes controlling or otherwise influencing how many species can co-occupy small areas. This was attempted for the Hamersley Ranges using generalised linear modelling to link richness with 30 measured environmental variables relating to soil nutrients and structure, geomorphology, climate and fire history. Although many significant correlations were found between richness of various plant groups and environmental variables, stepwise selection narrowed these down to a few geomorphic and climatic variables. Models related to resource variables showed non-linear relationships with richness and significant interactions. Species richness of the study area is linked to a complex of environmental variables, with much variability not explained by models. In terms of resource variables, herbaceous species are related to a complex of factors linked to soil moisture, soil fertility and ambient temperature. However woody species richness is only significantly related to available phosphorus, with the negative trend between richness and phosphorus reversed on alkaline soils. Trends and environmental relationships of species richness are discussed in relation to intermediate resource availability and disturbance hypotheses, as well as to heterogeneity. Although this latter factor was not measured directly, landscape scale patterns in richness, stepped species-area curves and linear relationship between richness and life-form diversity all suggest this fine scale environmental heterogeneity may be a key factor in determining richness at such scales.
Key words: alpha diversity, species richness, arid environments, plant community ecology