Persistent effects of fire severity on ponderosa pine regeneration niches and seedling growth

Using wildfire as a management strategy to restore resiliency to ponderosa pine forests in the southwestern United States

“…When combined with business-as-usual (1Â) treatments, the RO alternative only had a slight increase in the count of large disjunct high-severity patches greater than 200 m from the forest edge, and these patches were more complex in shape making them more likely to receive ample seed dispersal from the adjacent forest. Large circular or blocky high-severity patches in ponderosa pine forests have been shown to have seed dispersal limitations (Owen et al, 2017(Owen et al, , 2020Singleton et al, 2021) capable of catalyzing transitions to grass and shrub ecotypes (Taranc on et al, 2014), and facilitating an invasion by non-native plant communities with high fire spread rates (Kerns et al, 2020). Large patches of high-severity fire can have the opposite effect in colder temperate forest systems, where ruderal serotinous conifers (e.g., lodgepole pine) mass regenerate over large areas, thus creating and perpetuating crown fire system in the place of mixed-conifer forests that prior to fire exclusion supported patchy mixed and low-severity fire activity (Churchill et al, 2017).…”

“…Future work with landscape models can help managers envision fire management scenarios to determine how to best minimize extreme events and will become increasingly important as ongoing climate change continues to influence wildfire activity (Abatzoglou et al, 2019;Abatzoglou & Brown, 2012;Abatzoglou & Williams, 2016;Westerling et al, 2006) and tree regeneration (Feddema et al, 2013;Owen et al, 2017Owen et al, , 2020. Future work with the LSim model will leverage climate-FVS to model species envelopes (Crookston, 2014;Crookston et al, 2010;Taranc on et al, 2014), and use statistically downscaled energy release components (Abatzoglou, 2013;Barros et al, 2021) to model wildfire using future climate ensembles.…”

“…High-severity patch shape and conversion potential were assessed with a count of disjunct core areas within high-severity patches at least 200 m from the forest edge, and with the averageweighted mean (AM) perimeter-to-area ratio to assess the roundness of the patch perimeter (Helzer & Jelinski, 1999). High-severity patches (defined as those with >75% tree mortality excluding seedlings and saplings with a diameter at breast height <13 cm [Barrett et al, 2010]) were analyzed to understand how restoration and wildfire scenarios might prevent the occurrence of large patches where delayed forest regeneration contributes to type conversion potential (e.g., ponderosa pine to grass or shrub) as reported by Owen et al (2017Owen et al ( , 2020 and Singleton et al (2021), as well as others. Patch metrics were calculated using functions in FRAGSTATS (McGarigal & Marks, 1995).…”

“…We hypothesized that RO wildfire will improve the resiliency of the ponderosa pine ecosystem of the southwestern United States by (1) reducing the relative occurrence of high‐severity wildfire, (2) enhancing wildlife habitat and foraging opportunities for goshawk and Mexican spotted owls by enhancing forest heterogeneity and old‐growth forest structure, and (3) reducing the need for contemporary restoration treatments. We measured resiliency with the presence of old‐growth forest structures and overall potential for high‐severity fire and associated patch dynamics, recognizing that the latter can have a significant deleterious effect on forest regeneration in southwest pine ecosystems and elsewhere (Owen et al, 2017, 2020; Singleton et al, 2021; Stevens‐Rumann et al, 2016; Stevens‐Rumann & Morgan, 2016). The effects of climate change on fire regimes and forest ecology, which have been found to be limited in northern Arizona when compared to land management actions (O'Donnell et al, 2018), are not examined in this study.…”

Influencing factors on regeneration and seedling survival prediction in Larix principis‐rupprechtii plantations in northern China

“…L. principis-rupprechtii is a light-loving species, and stands with lower density often have larger gaps, which are not conducive to seedling regeneration (Owen et al, 2020). To some extent, taller herbs can provide some shading function for the seedlings and protect them.…”