Temporal phytocoenosia and synusiae: should we consider temporal sampling in vegetation classification?

Vegetation classification requires the defining of a hierarchy of types based on a spatial and temporal dimensionality. Spatial variation is achieved by plots being placed across the landscape; however, temporal dimensionality is generally only inferred but not directly tested and is rarely incorporated within the circumscription of types. Here, 108 permanent plots are surveyed across 7 years within the Mulga Lands Bioregion of north-western New South Wales through a drought cycle to assist in incorporating temporal dimensionality within community definition. Herbaceous biomass and species density decreased significantly and species composition changed associated with increasing drought conditions, with a return to closer to original conditions by the end of the study. Here, nine temporal associations and 31 synusiae are defined. The changes noted have significant implications for current vegetation classification methods, benchmarking and threatened community listings. The use of permanent plots in vegetation classification is recommended at least for threatened communities and highly dynamic vegetation types associated with less predictable climates.