The Effects of Disturbance History on Ground-Layer Plant Community Composition in British Columbia

Abstract

Plant communities are sensitive to perturbations and may display alternative recovery pathways depending on disturbance history. In sub-boreal lodgepole pine forests of central interior British Columbia, Canada, fire and logging are two widespread landscape disturbances that overlap in many regions. We asked whether cumulative, short-interval disturbance from logging and fire resulted in different ground-layer plant communities than resulted from fire alone. Using field-collected data, we compared the taxonomic composition and functional traits of 3-year old plant communities that were either harvested 6-to-13 years prior, or not harvested prior to being burned in a large stand-replacing fire. The taxonomic composition diverged between the two treatments, driven primarily by differences in a few key indicator species such as Petasites frigidus and Vaccinium membranaceum. Analysis of individual species' morphological traits indicated that only a few species vary in size in relation to disturbance history. Our data suggest that a history of forest harvest leaves a subtle footprint on post-fire ground-layer plant communities at early stages of succession.

Effects of a large wildfire on vegetation structure in a variable fire mosaic

“…, Romme et al. , Ton and Krawchuk ). Many legacy effects are likely to be related to previous fire history (the invisible mosaic), meaning that wildfires do not necessarily erase the effects of a previously established fire mosaic on vegetation structure.…”

“…However, even very severe wildfires are usually heterogeneous, with different areas burning at different severities (Turner and Romme 1994, Perry et al 2011, Berry et al 2015, Tingley et al 2016, meaning that while large wildfires can homogenize fire age, there may not be a coincident reduction in the variability of vegetation structures within a landscape. Moreover, even in areas that are severely burned by wildfires, legacy effects of previous vegetation on post-fire vegetation structure can be substantial (Franklin et al 2000, Fontaine et al 2009, Johnstone et al 2016, Romme et al 2016, Ton and Krawchuk 2016. Many legacy effects are likely to be related to previous fire history (the invisible mosaic), meaning that wildfires do not necessarily erase the effects of a previously established fire mosaic on vegetation structure.…”

Ecological consequences of compound disturbances in forest ecosystems: a systematic review

“…Although Coleman et al (2008) reported that logged sites exhibited comparable postfire plant assemblages and successional trajectories to unlogged sites, subtle species-specific and structural differences were observed. Altered recovery trajectories were also indicated by a reduction in postfire P. contorta seedling densities, attributed to clear-cut-mediated seed source reductions (Ton and Krawchuk 2016). Altered recovery trajectories were also indicated by a reduction in postfire P. contorta seedling densities, attributed to clear-cut-mediated seed source reductions (Ton and Krawchuk 2016).…”

“…For instance, reduced postfire regeneration was attributed to seed source reduction by a preceding fire (Taboada et al 2018), bark beetle outbreak (Harvey et al 2013), and clearcut logging operation (Ton and Krawchuk 2016). For instance, reduced postfire regeneration was attributed to seed source reduction by a preceding fire (Taboada et al 2018), bark beetle outbreak (Harvey et al 2013), and clearcut logging operation (Ton and Krawchuk 2016).…”

“…In contrast, Cobb et al (2007) documented conspicuous differences in beetle assemblages, characterized by reduced compositional variability, and Ton and Krawchuk (2016) documented distinct differences in plant assemblages, characterized by increased representation of disturbance-adapted species. Altered recovery trajectories were also indicated by a reduction in postfire P. contorta seedling densities, attributed to clear-cut-mediated seed source reductions (Ton and Krawchuk 2016).…”