Landscape age and soil fertility, climatic stability, and fire regime predictability: beyond the OCBIL framework

Hopper (Plant Soil 322:49-86, 2009) introduced landscape age, climate buffering, and soil nutrient status as descriptors for a continuum between old, climatically buffered landscapes characterised by low soil fertility (OCBIL) and young, often disturbed landscapes characterised by fertile soils (YODFEL). Hopper (Plant Soil 322:49-86, 2009) provided an important framework for biodiversity and conservation. We argue that Hopper's (Plant Soil 322:49-86, 2009) conceptual framework includes five areas worthy of further consideration. These include: (1) The appropriateness of the original three dimensions; (2) The need for deeper consideration of rejuvenation and disturbance within OCBILs. (3) Broadening the globally relevant range of environments. (4) Operationalising the definitions or dimensions. (5) Revisiting the scale and compatibility of the predictions. Here, we address the first four of these areas and offer an alternative conceptual framework based on the idea of Old Stable Landscapes (OSLs). We redefine Hopper's climate buffering as a dimension of climate stability, identify soil-impoverishment as a function of landscape age, and recognise fire regime predictability as a large-scale, long-term evolutionarily important dimension. In so doing, we construct a globally-relevant, qualitative template to enable the testing of evolutionary-ecological hypotheses concerning biodiversity (e.g. species diversity, diversity gradients, endemism, speciation and extinction rates, cladogenesis, persistence of old lineages, refugial phenomena). Our template is characterised by having operationally defined dimensions, which can be used to design surveys and experiments to address the issues of biodiversity conservation, recovery, and restoration under variations in landscape age, climatic stability and fire regime.