Lack of soil seedbank change with time since fire: relevance to seed supply after prescribed burns

Abstract

Soil seedbanks play a key role in the post-fire recruitment of many plant species. Seedbank diversity can be influenced by spatial variability (e.g. geographic location), environmental variability (e.g. soils) and temporal disturbance heterogeneity (e.g. time since fire, TSF) across the landscape. Unlike for aboveground vegetation, relationships between these factors and soil seedbank diversity remain largely unknown. Partitioning the influence of spatial and environmental variability from that of TSF, and explaining how these factors interact with seedbank diversity, will assist conservation managers in their application of prescribed burning. We germinated soil seedbank samples from sites ranging from 1 to 75 years since fire in a heathy-woodland ecosystem across the Otway Ranges in Victoria, Australia. We also measured spatial and environmental variability across sites to partition the influence of these variables and TSF on propagules available for recruitment. We found weak positive relationships between seedbank richness and TSF; however, these relationships varied across the landscape. We found composition did not change considerably over time, suggesting, in this ecosystem, pre-fire age is not strongly influencing propagules available for recruitment post-fire. Our results suggest that spatial and environmental variability influence seedbank composition more than TSF.