Effects of fire disturbance on alpha and beta diversity and on beta diversity components of soil seed banks and aboveground vegetation

Background and aims - Although an understanding of the effects of fire severity on diversity components of the soil seed bank (SSB) and aboveground vegetation (AGV) is important to inform conservation and restoration practices of biodiversity, the effects of fire severity on alpha- and beta-diversity of SSB and AGV are poorly understood. While beta-diversity is shaped by spatial turnover and nestedness, research on the effects of fire severity on these components of beta-diversity is limited. We aimed to determine the effects of low and high fire severity on species richness and alpha- (within sample) and beta-(among sample) diversity components on the relationship between the SSB and AGV. Since turnover and nestedness are components of beta-diversity, we assessed their patterns of change after different fire intensities in the SSB and AGV. Methods - Soil seed bank samples were collected from the same 180 sample points used for measurement of AGV in semi-arid Quercus persica woodlands. Additive partitioning diversity was used to divide total diversity into a- and beta-diversity of the SSB and the AGV. Total beta-diversity of the SSB and AGV was additively partitioned into spatial turnover and nestedness. Key results - Fire severity had significant effects on alpha- and beta- diversity of both the SSB and AGV. The highest and lowest richness and alpha- and beta-diversity in both the SSB and AGV were found in low and high severity fire sites, respectively. Partitioning beta- diversity of the SSB and the AGV into turnover and nestedness components revealed that spatial turnover was the main contributor to beta-diversity. High fire severity significantly increased similarity between SSB and AGV. Conclusions - Low, but not high, severity fire can increase species diversity in the AGV and SSB, and it has the potential to serve as a tool for management and restoration of semi-arid Mediterranean regions, thereby enhancing plant diversity and structural heterogeneity. However, high severity fire may lead to loss of many species in both the SSB and the AGV resulting in loss of biodiversity.