Indigenous pyrodiversity promotes plant diversity

Pyrodiversity (temporally and spatially diverse fire histories) is thought to promote biodiversity by increasing environmental heterogeneity and replicating Indigenous fire regimes, yet studies of pyrodiversity-biodiversity relationships from areas under active Indigenous fire stewardship are rare. Here, we explored whether Indigenous pyrodiversity promoted plant richness and diversity in an arid ecosystem from north-western Australia. We selected landscapes that ranged from highly pyrodiverse and under active Indigenous burning to more coarse-scale and less diverse mosaics under lightning fire regimes. We modelled how the visible (time-since-fire diversity and proportion of post-fire successional stages) and invisible fire mosaic (fire frequency diversity and maximum proportion of landscape burnt) influenced plant richness and diversity, including edible plants. We found evidence that pyrodiversity maintained by Indigenous people increases the richness and diversity of some plant groups: time-since-fire diversity was associated with higher total plant richness and diversity; fire frequency diversity was associated with higher total plant diversity; and total plant diversity decreased with increasing the maximum proportion of a landscape that had burnt. Additionally, we found that some plant groups, including culturally important edible plants, were sensitive to the spatial extent of specific fire ages. By linking our previous work that shows Indigenous burning promotes pyrodiversity and reduces fire size, we find evidence for the notion that Indigenous fire stewardship, through the provision of pyrodiversity, promotes plant richness and diversity. Our work highlights the importance of Indigenous burning for maintaining and promoting plant diversity in fire-prone ecosystems.