Mechanisms of fire‐maintained plant species diversity in species‐rich wet pine savannas

Abstract

Temperate savannas and grasslands maintained by frequent, low‐intensity disturbances such as fire contain among the most species‐rich plant communities in the world. Precisely how these disturbances maintain such high fine‐scale diversity is poorly understood. This study examined the effects of the frequency of simulated fire (clipping combined with litter removal) and the relative importance of recruitment and survival on species diversity and trait and species composition at each of two pine savannas in southeastern Mississippi (USA) that had not been recently burned. Ten 2 × 2 m plots at each site were clipped/cleared annually from 2014 to 2019 and again in spring 2021 (annual frequency). The other 10 clipping plots were not clipped from 2018 to 2020 (reduced frequency). Vegetation in small subplots in annual frequency and reduced frequency plots was compared in August 2021 to test the effects of a short period without clipping on diversity and composition. To test the relative importance of recruitment and survival on diversity and composition, four 0.25 × 0.25 m quarter plots were established within each of 10 annual frequency plots per site following a clipping treatment in fall 2019 and assigned a 2 × 2 factorial arrangement of transplantation of sods from long‐unburned areas and herbicide application. Reducing the frequency of clipping reduced plant diversity and altered composition at both sites. A comparison of diversity and trait composition responses to transplant and herbicide treatments revealed how recruitment and survival combined to affect species diversity. Partial or complete recovery of diversity following clipping and litter removal at both sites was driven by rapid increases in short‐lived, resilient species that show fire‐stimulated emergence from a seed bank and the persistence of long‐lived species capable of surviving the prolonged period without fire or clipping. Species with reduced resilience and persistence were more likely to be lost in the reduced frequency treatment. Results are consistent with a model of short‐term coexistence of maximum species diversity maintained by the most frequent fire regime fuels will permit.

Pine trees structure plant biodiversity patterns in savannas

“…Most species that were significant in our analyses had higher abundances in open plots where there was greater light availability, which has been suggested as a key mechanism for differences in vegetation composition in other similar studies (e.g., Brewer, 1998 ; Lavoie et al., 2012 ). Although previous research at these sites did not detect differences in some fire‐related characteristics of basal and open locations after one fire (Kreye et al., 2020 ), the occurrence of certain species close to and away from pines could reflect the long‐term fire history at each point (Brewer, 2023 ). In addition, they could result from spatial patterns of pine litter deposition, which has been shown to vary with time since fire, decomposition rate, stand structure, and direction of prevailing winds (Blaydes et al., 2023 ; Sánchez‐López et al., 2023 ).…”

Examining changes in woody vegetation cover in a human-modified temperate savanna in Central Texas between 1996 and 2022 using remote sensing

“…Woody plant encroachment significantly influences the hydrological cycle by altering various components of the water budget equation, including precipitation, runoff, groundwater recharge, and evapotranspiration (Bonan, 2008;Eldridge et al, 2011Eldridge et al, , 2015Wine et al, 2012;Leite et al, 2020;Zhou et al, 2023). Additionally, the frequency of fires has a significant impact on the ecological diversity of open-canopy savannas undergoing WPE (Brewer, 2023). During the initial phase of encroachment, there is a rapid decline in grassland dependent herbaceous species (Fuhlendorf et al, 2002;Lautenbach et al, 2016), although certain species may tolerate up to 15% coverage of woody plants (Archer, 2009).…”

Fostering biodiversity in Neotropical savannahs: fire as a diversity driver for fruit-feeding butterfly assemblages in the Brazilian Cerrado

“…However, some animals might bene t from re, when they are able to use recently burned habitats or the more available resources after wild res, leading to a local increase in their populations (Pausas & Parr 2018). Fire may also affect animals indirectly by altering plant and soil microbial communities, as well as soil nutrients, and increasing habitat heterogeneity, which usually helps maintaining higher levels of biodiversity (Dell et al 2017;Nelson et al 2022;Brewer 2023).…”