Temporal patterns of ground flora response to fire in thinned Pinus–Quercus stands

Abstract

The ground flora stratum affects stand structure, resource acquisition, nutrient cycling, and taxonomic richness in forest ecosystems. Disturbances such as thinning and prescribed fire alter forest understory growing conditions that generally increase ground flora cover and richness. We studied annual changes in ground flora assemblages over three growing seasons after fire in thinned and frequently burned (3-year rotation) Pinus-Quercus stands. Our results corroborated trends from other studies that indicated greater ground flora richness and cover after thinning and burning compared with thin-only treatments. We also found that the stratum experienced relatively rapid succession between growing seasons that complimented the tolerance succession model. Forbs had reduced cover and richness from increasingly difficult growing conditions over time and were replaced by woody plants, shrubs, and seedlings. This likely occurred from changing competition dynamics that favored quick growth in the first growing season and long-term investment in vertical growth in the third growing season. The successful regeneration pathways also fit ground flora regeneration models and added a unique pathway to strengthen the predictive power of these models. As many stand management goals are focused towards improving biodiversity, prescribed fire and thinning may be used to increase understory richness in Pinus-Quercus stands.Résumé : La strate composée de la flore du sol influence la structure du peuplement, l'acquisition des ressources, le recyclage des nutriments et la richesse taxonomique dans les écosystèmes forestiers. Les perturbations, telles que l'éclaircie et le brûlage dirigé, modifient les conditions de croissance dans le sous-bois des forêts et augmentent généralement la richesse et le couvert de la flore du sol. Nous avons étudié les variations annuelles dans les assemblages de la flore du sol pendant trois saisons de croissance après feu dans des peuplements éclaircis et fréquemment brûlés (à tous les 3 ans) de pin et de chêne (Pinus et Quercus, respectivement). Nos résultats corroborent les tendances rapportées dans d'autres études indiquant que la richesse et le couvert de la flore du sol augmentent après une éclaircie et un brûlage comparativement à une éclaircie seule. Nous avons également trouvé que la strate connaissait une succession relativement rapide entre les saisons de croissance, ce qui va dans le sens du modèle de succession basé sur la tolérance. Le couvert et la richesse des plantes herbacées non graminoïdes ont diminué avec le temps à cause des conditions de croissance de plus en plus difficiles et elles étaient remplacées par des plantes ligneuses, des arbustes et des semis. Cela est survenu vraisemblablement à cause du changement dans la dynamique de la compétition qui a favorisé une croissance rapide durant la première saison de croissance et un investissement à long terme dans la croissance verticale durant la troisième saison de croissance. Les trajectoires qui favorisent la régénération correspon...

Understory Vegetation Responses to 15 Years of Repeated Fuel Reduction Treatments in the Southern Appalachian Mountains, USA

“…Nonetheless, our results contradict much existing research that report decreases in red maple stem density following one or two prescribed burn treatments [35,60,61]. This may be because most red maple regeneration occurred from basal resprouts, resprout clumps insulated inner stems from fire damage, fires were not hot enough, or frequent dormant season burning may be creating more favorable microsite conditions for red maple by decreasing the litter and duff layers and allowing root growth into mineral soil [38,62,63]. Red maple responded least-favorably to C and MB, suggesting slowed growth from competition of other understory hardwoods in C, as represented by the changes of IV, or mortality after repeated mechanical reductions and/or increased fire severity in MB which may facilitate adequate control of this species.…”

Eucalyptus Are Unlikely to Escape Plantations and Invade Surrounding Forests Managed with Prescribed Fire in Southeastern US

“…Our results corroborate with the ones found by Fernandes et al [52], who in the study of E. globulus seed germination after soil disturbances, found higher germination in raked (~34%) than in unraked areas (~19%). Although there may be times when leaf litter facilitates germination because of its ability to hold moisture [32,53], the relationships we observed between germination rates and light availability (both canopy and litter light penetration) suggest that leaf litter is more of a hindrance to seed germination.…”

“…Agricultural land uses include heavy land management tactics, such as herbicide application and species control [30], that are not conducive to the establishment of non-native tree species. Forest-use lands and less extensively managed fields exhibit increased leaf litter and decreased light penetration [31,32], which are also not conducive to non-native tree establishment. Eucalyptus species are more likely to become invasive in lands that are managed with prescribed burns [33][34][35].…”

Season of burn has minimal effect on groundlayer community structure and composition in an Appalachian mixed‐oak forest

“…Vander Yacht et al (2017 b ) report that fire following light thinnings, where basal areas exceeded 15 m 2 /ha (>80% canopy closure), creates conditions that often maintain a woody‐dominated groundlayer, whereas heavy overstory removal to levels below that threshold followed by fire may stimulate the seed bank, which coupled with a higher light environment, facilitates an increase in the richness, diversity, and total cover of herbaceous and graminoid components. Burning after thinning can further promote and/or maintain the herbaceous (forb plus graminoid) component over time (Willson et al 2018; Barefoot et al 2019; Bassett et al 2020). In contrast, Oakman et al (2019) reported a negligible change in herbaceous or graminoid cover and diversity after thinning and four dormant season burns that together reduced overstory basal area (stems >10 cm dbh) to approximately 15 m 2 /ha in a mixed‐oak forest similar to and within proximity (approximately 60 km) to our study site.…”