Australian rainforest ecology on the basis of species traits
thesisposted on 2022-03-28, 02:09 authored by Robert Michael Kooyman
Objectives: Quantify the influence of species traits, functional and phylogenetic diversity, history, scale, and environmental gradients on community assembly in tropical and sub-tropical rainforests. Methods: Three datasets were used. Allometric relationships governing the economy of sapling height gain were investigated for 11,111 individuals from 75 species in sub-tropical rainforest. Trait-gradient analysis partitioned species trait values between alpha (within) and beta (among) components for 231 woody taxa in 216 sub-tropical rainforest assemblages. Community phylogenetic structure was quantified for 596 assemblages, 1137 taxa, four functional traits, and two latitude regions (tropical and sub-tropical). Taxonomic patterns, trait values and structures, phylogenetic structure, and species niche breadth were quantified and compared across selected gradients and scales. Results: Main-stem mass required to achieve a common height was the product of stem volume and wood density, and not significantly linked to other ecological traits. Correlation structures of species trait values differed across scales. Within sites, dispersal, habitat filtering, and competitive exclusion did not create strong linkages among traits. Across the landscape, abiotic drivers created strong linkages among leaf, stem, and seed traits. Within species height variation showed only a few species moved from lower to higher height ranking as site-mean-height declined. Most declined in unison with, or had a narrower range relative to site-mean-heights. Phylogenetic divergences in moist forest along the latitudinal gradient between the tropics and sub-tropics were older than those along the altitudinal gradient within. Assemblages of species were more phylogenetically clustered where the effects of historic climatic oscillations had been greater, and less clustered in long-term stable locations. Conclusions: Historic and recent rainforest contraction and re-expansion resulted in species within regions being more related than by chance. In recolonised areas within regions, species pools and trait ranges were reduced, and assemblages were dominated by widely dispersed species with greater niche breadth.