Topographic position amplifies consequences of short-interval stand-replacing fires on postfire tree establishment in subalpine conifer forests

Hoecker, Tyler J.; Hansen, Winslow D.; Turner, Monica G.

doi:10.1016/j.foreco.2020.118523

Cited by 35 publications

(32 citation statements)

References 74 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Areas disproportionally at risk of losing resilience occurred where fires are not constrained by topography and can grow exceedingly large, such as the Yellowstone central plateau, and valleys aligned with predominant winds from the southwest, fueling fire spread. Areas that are already warm and dry, for which warming and increased aridity may limit tree regeneration (e.g., the low elevation northern reaches of the GYE; Hansen & Turner, 2019) or locations subject to sequential high‐severity fires (Hoecker et al, 2020) are also at risk. In contrast, cooler (e.g., north‐exposed) sites surrounded by complex mountain topography could serve as climate refugia for current forest types (Albrich et al, 2020; Serra‐Diaz et al, 2015; Turner et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

“…Analysis of regeneration failure at the level of forest types was based on their current spatial distribution and tallied as absolute area and percentage of current area lost. All analyses of simulation results were conducted with the R Project for Statistical Computing (R Core Development Team, 2019), specifically using the tidyverse (Wickham et al, 2019) and raster packages (Hijmans, 2019).…”

Section: Analysesmentioning

confidence: 99%

See 1 more Smart Citation

Widespread regeneration failure in forests of Greater Yellowstone under scenarios of future climate and fire

Rammer

Braziunas

Hansen

et al. 2021

Global Change Biology

Self Cite

View full text Add to dashboard Cite

Changing climate and disturbance regimes are increasingly challenging the resilience of forest ecosystems around the globe. A powerful indicator for the loss of resilience is regeneration failure, that is, the inability of the prevailing tree species to regenerate after disturbance. Regeneration failure can result from the interplay among disturbance changes (e.g., larger and more frequent fires), altered climate conditions (e.g., increased drought), and functional traits (e.g., method of seed dispersal). This complexity makes projections of regeneration failure challenging. Here we applied a novel simulation approach assimilating data‐driven fire projections with vegetation responses from process modeling by means of deep neural networks. We (i) quantified the future probability of regeneration failure; (ii) identified spatial hotspots of regeneration failure; and (iii) assessed how current forest types differ in their ability to regenerate under future climate and fire. We focused on the Greater Yellowstone Ecosystem (2.9 × 106 ha of forest) in the Rocky Mountains of the USA, which has experienced large wildfires in the past and is expected to undergo drastic changes in climate and fire in the future. We simulated four climate scenarios until 2100 at a fine spatial grain (100 m). Both wildfire activity and unstocked forest area increased substantially throughout the 21st century in all simulated scenarios. By 2100, between 28% and 59% of the forested area failed to regenerate, indicating considerable loss of resilience. Areas disproportionally at risk occurred where fires are not constrained by topography and in valleys aligned with predominant winds. High‐elevation forest types not adapted to fire (i.e., Picea engelmannii–Abies lasiocarpa as well as non‐serotinous Pinus contorta var. latifolia forests) were especially vulnerable to regeneration failure. We conclude that changing climate and fire could exceed the resilience of forests in a substantial portion of Greater Yellowstone, with profound implications for carbon, biodiversity, and recreation.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Analysesmentioning

confidence: 99%

Widespread regeneration failure in forests of Greater Yellowstone under scenarios of future climate and fire

Rammer

Braziunas

Hansen

et al. 2021

Global Change Biology

Self Cite

View full text Add to dashboard Cite

show abstract

“…After accounting for variability in total canopy cover, our final statistical models revealed no additional effect of variability in live vs. dead canopy cover among plots (represented by the Axis1 metric); this suggests that moderate‐ and high‐severity fire most strongly affected microclimate directly through the loss of canopy shading. Residual dead trees, including the fine branches that are retained for several years after fire, can thus contribute significantly to regulating near‐ground microclimates after fire (Fontaine et al 2010, Hoecker et al 2020), potentially increasing the likelihood of successful postfire tree regeneration where seed availability is not limiting.…”

Section: Discussionmentioning

confidence: 99%

“…Recently burned areas comprise a mosaic of varying fire effects, including tree mortality and impacts on understory cover, which in turn affect the degree to which shading, surface roughness, evapotranspiration, and albedo are altered relative to unburned forest (Liu 2005, Chambers 2005, Liu et al 2019). For example, structural features such as standing dead trees may lessen the impacts of canopy loss on microclimate in burned areas (Hoecker et al 2020), and changes in surface cover after fire affect land surface temperatures (Liu et al 2019). Anticipating the vulnerability of forest vegetation to the combined effects of changing climate and fire regimes thus requires understanding the impacts of wildfires on microclimatic buffering, and the degree to which these impacts vary across fire severity and biophysical gradients.…”

Section: Introductionmentioning

confidence: 99%

Wildfire impacts on forest microclimate vary with biophysical context

et al. 2021

View full text Add to dashboard Cite

Increasing wildfire activity in western North America has the potential to remove forest canopy cover over large areas, increasing the vulnerability of understory plants and juvenile trees to microclimatic extremes. To understand the impacts of wildfire on forest microclimatic buffering, we monitored daily temperature and vapor pressure deficit (VPD) in 33 plots over the first two growing seasons following two wildfires from 2017. The Lolo Peak and Sunrise fires occurred during a regionally extensive fire season, burning mixed-conifer and subalpine forests across complex mountainous topography in western Montana. Sensors were deployed from June to September in 2018 and 2019 in sites stratified by aspect, elevation, and fire severity (unburned, moderate, high) to capture a range of forest types, biophysical contexts, and fire effects. Loss of canopy and understory vegetation had marked effects on microclimate: On average, sites burned at high severity had 3.7°C higher daily maximum temperatures and 0.81 kPa higher daily maximum VPD relative to paired unburned sites. Differences between burned and unburned sites were most pronounced when ambient temperatures were high, across diurnal and seasonal time scales. Differences were also more pronounced at sites with less canopy cover, more bare ground postfire, and greater long-term water availability (i.e., low climatic water deficit). Our results reveal fire-caused changes in microclimate extremes that are biologically meaningful for the postfire establishment of tree seedlings and understory vegetation. These effects depend strongly on biophysical context, with cool-wet forests more vulnerable to fire-caused changes in microclimate compared with warm-dry settings. Our results further highlight the functional importance of standing dead trees for moderating surface temperature in postfire environments. Anticipating forest ecosystem responses to increased warming and wildfire activity, and the potential for fire to catalyze vegetation changes, thus requires considering the substantial impacts of fire on microclimate.

show abstract

“…Differences in tree regeneration could have important effects on local soil conditions, including temperature and moisture, as sparsely vegetated sites or sites with more seedlings than mature trees may be warmer and drier (Hoecker et al, 2020). This finding raises the question, are bacterial communities different because there was more regeneration, or was tree regeneration more successful because of the bacterial community?…”

Section: Shorter Fire-free Intervals Alter Bacterial Communities Reflecting Changes In Vegetation and Soil Propertiesmentioning

confidence: 99%

Short-interval reburns in the boreal forest alter soil bacterial communities, reflecting increased pH and poor conifer seedling establishment

Woolet

Whitman

Parisien

et al. 2021

Preprint

View full text Add to dashboard Cite

Increasing burn rates (percentage area burned annually) in some biomes are leading to fires burning in close succession, triggering rapid vegetation change as well as altering soil properties. Despite the importance of soil microbes for nutrient cycling and as plant symbionts, the effects of increased fire frequency on belowground microbial communities remain largely unknown. We present a study of the effects of short interval reburns (defined here as <20 years between fires) on soil bacterial communities in the boreal forest of northwestern Canada, using a paired site design that spans wetlands and uplands, with 50 sites total. We asked whether short interval reburns significantly alter soil bacterial community composition and richness, and which bacterial taxa are associated with greater or lower fire frequency. We found that, while short interval reburns had no significant effect on bacterial richness, there were significant changes in overall community composition. We did not find correlations between understory vegetation community dissimilarities and bacterial community dissimilarities, suggesting the primary drivers of changes induced by short interval reburns may differ between plants and microbes. We identified an abundant Blastococcus sp. that was consistently enriched in short interval reburns, in both wetlands and uplands, indicating its role as a strongly "pyrophilous" bacterium. We also identified an abundant Callaberonia sordidicola taxon as being consistently depleted in short interval reburns. This endophytic diazotrophic organism is a robust colonizer of pine and spruce seedlings and has the ability to increase seedling growth, due in part to large contributions of fixed nitrogen. Its depletion in short-interval reburn sites raises questions about whether this is contributing to - or merely reflects - poor conifer seedling recolonization post-fire at short-interval reburns.

show abstract

Topographic position amplifies consequences of short-interval stand-replacing fires on postfire tree establishment in subalpine conifer forests

Cited by 35 publications

References 74 publications

Widespread regeneration failure in forests of Greater Yellowstone under scenarios of future climate and fire

Widespread regeneration failure in forests of Greater Yellowstone under scenarios of future climate and fire

Wildfire impacts on forest microclimate vary with biophysical context

Short-interval reburns in the boreal forest alter soil bacterial communities, reflecting increased pH and poor conifer seedling establishment

Contact Info

Product

Resources

About