Can sampling for vegetation characterisation surrogate for species richness? Case studies from the wet–dry tropics of northern Australia

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Understanding the distribution of plant species and vegetation communities is important for effective conservation planning and ecosystem management, but many parts of the world remain under-surveyed. The Top End of Australia’s Northern Territory is vast, remote, and sparsely populated; knowledge of the flora, in many areas, is limited to common or dominant species. Here, we describe and contrast the benefits and trade-offs between two approaches to botanical survey – vegetation sampling (assessment of structural attributes and species composition, fundamentally for mapping purposes) and hybrid floristic survey (an intensive, inventory approach considering seasonality) – as applied in each of four remote areas of the Australian wet–dry monsoonal tropics. Hybrid floristic survey effectively doubled the species richness recorded within each study area, largely due to improved detections of forbs and sedges. Species-sampling effort relationships predicted hybrid floristic survey to consistently out-perform vegetation sampling in maximum species richness and rate of species accumulation. Although vegetation sampling offers an efficient means of circumscribing vegetation communities over large areas, hybrid floristic survey improved detection of seasonal species and, potentially, those of conservation concern. Strategic, proactive investment in hybrid floristic surveys may offer improved conservation outcomes and potential efficiency dividends in biodiversity conservation planning.