Mapping risk to plant populations from short fire intervals via relationships between maturation period and environmental productivity

Short fire intervals potentially drive declines in plant populations through immaturity risk—when the interval between two fires is too short to allow a plant population to develop the capacity to persist through the second fire. Through quantifying the period of time after fire for obligate-seeding species to become reproductively mature (the juvenile period), the risk of population decline under specific fire intervals can be delineated. Juvenile periods vary across space and time. We developed a model to estimate juvenile period based on environmental productivity that is applicable at a regional scale and over time with changes in climate. We compiled juvenile period data of serotinous obligate-seeder taxa across the breadth of the Southwest Australian Floristic Region (SWAFR). Environmental productivity models explained up to 76% of the variation in maximum juvenile period length. Juvenile period increased with lower precipitation, lower mean annual temperature and lower gross primary productivity, allowing spatial predictions of minimum tolerable fire intervals to conserve slow-maturing serotinous obligate-seeders across an entire floristic region. Applying juvenile period-productivity relationships to future climate scenarios indicated that for much of the SWAFR, juvenile period length is predicted to increase substantially, indicating high risk of short fire interval impacts with continuation of historic fire intervals. Using a case study of the Stirling Range National Park, we use historic fire interval data to identify locations having experienced short fire interval risk