Wildfire Disturbance Research Articles

An integrated dataset of ground hydrothermal regimes and soil nutrients monitored in some previously burned areas in hemiboreal forests in Northeast China during 2016–2022

Abstract. Under a warming climate, the occurrence of wildfires has been becoming increasingly more frequent in boreal forests and Arctic tundra over the last few decades. Wildfires can cause radical changes in forest ecosystems and the permafrost environment, such as the irreversible degradation of permafrost, succession of boreal forests, rapid and massive losses of soil carbon stock, and increased periglacial geohazards. Since 2016, we have gradually and more systematically established a network for studying soil nutrients and monitoring the hydrothermal state of the active layer and near-surface permafrost in the northern Da Xing'anling Mountains in Northeast China. Soil moisture content (depth of 0–9.4 m), soil organic carbon content (0–3.6 m), total nitrogen content (0–3.6 m), and total phosphorus and potassium content (0–3.6 m) datasets were obtained in 2016 via field sampling and subsequent laboratory tests. Ground temperature (0–20 m) and active layer thickness (2017–2022) datasets were obtained using thermistor cables that were permanently installed in boreholes or interpolated with these temperatures. The present data can be used to simulate changes in permafrost features under a changing climate and wildfire disturbances and to explore the changing interactive mechanisms of the fire–permafrost–carbon system in hemiboreal forests. Furthermore, they can provide baseline data for studies and action plans to support the carbon neutralization initiative and assessment of the ecological safety and management of the permafrost environment. These datasets can be easily accessed via the National Tibetan Plateau/Third Pole Environment Data Center (https://doi.org/10.11888/Cryos.tpdc.300933, Li and Jin, 2024).

The effect of postfire regeneration pattern on soil respiration in the boreal forest of China

BackgroundAs the second largest carbon flux between the atmosphere and terrestrial ecosystems, soil respiration involves multiple components of ecosystem production. Revealing soil respiration in forests with different postfire regeneration patterns is critical for determining appropriate restoration strategies in response to increasing wildfire disturbances. Here, we examined the influence of five postfire regeneration patterns (L: Larix gmelinii monocultures, LB: L. gmelinii and Betula platyphylla mixed plantations, P: Pinus sylvestris var. mongolica monocultures, PB: P. sylvestris var. mongolica and B. platyphylla mixed plantations, N: naturally regenerated forests) on soil heterotrophic respiration (Rh) and total respiration (Rs).MethodsTrenching was implemented to monitor soil heterotrophic respiration. We used partial least squares path modeling methods to estimate the different environmental factors regulating soil respiration across forest types.ResultsThe results showed that forest type and season had significant effects on Rs and Rh. Rh was the dominant part of Rs for all forest types (68.84 ~ 90.20%). Compared to naturally regenerated forests, Rs and Rh under L, LB, and PB had higher rates (P < 0.05), while Rs and Rh under P had lower rates (P < 0.05). The temperature sensitivities of Rs under different forest types were 2.316 (L), 1.840 (LB), 1.716 (P), 1.665 (PB), and 2.096 (N).ConclusionsForests regenerated with artificial participation established their plant communities visibly faster than naturally regenerated forests. Mixed species plantation regeneration demonstrated an improvement in soil respiration compared to naturally regenerated forests but had a lower temperature sensitivity of soil respiration than their respective monocultures. Soil temperature and moisture dominated the influence factors on soil respiration throughout the broader seasonal shifts. However, for a single season, forest productivity and soil properties have a greater impact on soil respiration. This study extends our knowledge of the interaction mechanism between soil respiration and environmental variables in boreal forests and contributes to improving confidence in global carbon cycling model predictions.

Geomorphic characteristics influencing post-fire river response in mountain streams

As wildfires increase in frequency and severity, there is a growing interest in understanding river response to the wildfire disturbance cascade. Numerous headwater mountain catchments within the Cache la Poudre (Poudre) River basin in the Colorado Front Range, USA burned severely and extensively during the 2020 Cameron Peak fire. Debris flows and flash floods occurred in many of these catchments triggered by convective storms after the fire. The downstream effects of the floods and sediment varied along a continuum from attenuated and largely contained within the catchment, to releasing substantial volumes of water and sediment to the Poudre River. We conceptualize these catchments as exhibiting decreasing absorbance of post-fire disturbance along the continuum described above based on the geomorphic evidence of relative sediment export. We conceptualize characteristics on different spatial scales as driving or resisting response to disturbance and therefore impacting the absorbing capacity (ability to attenuate post-fire fluxes) of the catchment. As the magnitude of resisting characteristics increases at the catchment, inter- and intra- reach scales, we hypothesize that a catchment will increasingly absorb the impacts of the wildfire disturbance cascade. We conducted longitudinally continuous surveys to measure reach-scale characteristics within each study catchment. We focus on the catchment- and reach-scale geomorphic, vegetation, and burn characteristics. The floods observed at the study catchments illustrate fire influencing the elevation above which rainfall-induced flooding occurs due to the efficient conveyance of water from hillslopes to channels after wildfire. Results suggest that inter- and intra-reach spatial heterogeneity are better aligned with absorbance capacity than catchment-scale characteristics: greater absorbing capacity is associated with greater longitudinal variations in floodplain/channel width and more reaches with wide floodplains, low channel gradients, beaver-modified topography, and multi-stem deciduous vegetation. We connect the capacity to absorb the impacts of disturbance as informing the catchment response to wildfire disturbance.

Principle, structure and application progress of the forest landscape model FireBGCv2.

Forest landscape model can quantitatively simulate the spatiotemporal variations in forest structure and function at the landscape scale based on traditional field survey data and mathematical models, providing a reference for the formulation of scientific forest management strategies. FireBGCv2 is one of the representative models currently used in the research area of forest landscape changes. It can simulate ecological processes at various scales, including trees scale (tree growth, establishment, and mortality), stand scale (carbon and nitrogen pools, fuel treatment, decomposition), site scale (resource competition and species phenology), and landscape scale (seed dispersal and wildfire disturbances), and the effects of those processes on forest landscape structure and function. The advantage of this model lies in its ability to simulate multiple ecological processes while considering the diversity and complexity of ecosystems. However, it also has drawbacks, such as high computational demands and complexity of use. We summarized the basic principles and structure of FireBGCv2 and introduced its application progress in forest landscape research and management. Currently, the application of the FireBGCv2 model, both domestically and internationally, mainly focused on exploring the interactions between fire, climate, and vegetation, quantifying the spatial and temporal dynamics of fires, and describing potential fire dynamics under future climate scenarios and land management strategies. With the in-depth development of forest landscape model theories and applications, the future prospects of FireBGCv2 include improving and updating the model's algorithms, adding new functional modules to explore fire management issues, and meeting the needs of different users.

Longitudinal propagation of aquatic disturbances following the largest wildfire recorded in New Mexico, USA

Wildfire disturbance propagation along fluvial networks remains poorly understood. We use incident, atmospheric, and water-quality data from the largest wildfire in New Mexico’s history to quantify how this gigafire affected surface runoff processes and mobilized wildfire disturbances into fluvial networks after burning 1382 km2. Surface runoff post-fire increased compared to pre-fire conditions, and precipitation events that are frequently observed in the affected watershed (<2-year recurrence) and fell during the post-fire first rainy season resulted in uncorrelated, less frequently observed runoff events (10-year recurrence). Besides these shifts in runoff generation, the magnitude and fluctuation of daily water quality parameters and relevant ecosystem processes also shifted over multiple months, even at sites located >160 km downstream of the burn perimeter. Our findings emphasize the need to incorporate spatially resolved longitudinal sampling designs into wildfire water quality research and highlight the spatiotemporal co-dependency among atmospheric, terrestrial, and aquatic processes in defining the net outcome of wildfire disturbance propagation along impacted fluvial networks.

Holocene vegetation and wildfire disturbance in boreal central Yukon, Canada

Sediment cores were collected from Wrong (WL) and Lenore (LL) lakes in boreal central Yukon Territory, Canada, spanning circa 6000 years. Analyses of pollen, charcoal, magnetic susceptibility, levoglucosan, and down-scaled paleoclimatic data reveal the vegetation history and character/drivers of Holocene fire disturbance. Boreal forest has persisted in the region for millennia, with a regional mid-Holocene expansion of Picea mariana followed by expansion of Pinus contorta in the latest Holocene. The shortest reconstructed fire return intervals (FRI; ca. 110-125 years) occurred in the mid-Holocene, coincident with the development of highly flammable Picea-dominated forest and warm, dry summers that were characterized by elevated JJA Z500 anomalies and associated with an eastward/intense Aleutian Low. In the late-Holocene, FRI increased to ca. 240 years at WL and 280 years LL. Drivers of this change include regional cooling and increased precipitation, with a westward/weaker Aleutian Low position delivering more moisture to interior Yukon. Longer FRIs allowed for greater fuel accumulation between fires, enhancing fire size/severity. While higher fire frequency is noted in the mid-Holocene and increased fire size/severity in the late-Holocene, recent changes in Yukon fire disturbance suggest that the fire regime may soon lie outside the natural range of mid- and late-Holocene variability.

Soundscape mapping: understanding regional spatial and temporal patterns of soundscapes incorporating remotely-sensed predictors and wildfire disturbance

Increased environmental threats require proper monitoring of animal communities to understand where and when changes occur. Ecoacoustic tools that quantify natural acoustic environments use a combination of biophony (animal sound) and geophony (wind, rain, and other natural phenomena) to represent the natural soundscape and, in comparison to anthropophony (technological human sound) can highlight valuable landscapes to both human and animal communities. However, recording these sounds requires intensive deployment of recording devices and storage and interpretation of large amounts of data, resulting in large data gaps across the landscape and periods in which recordings are absent. Interpolating ecoacoustic metrics like biophony, geophony, anthropophony, and acoustic indices can bridge these gaps in observations and provide insight across larger spatial extents and during periods of interest. Here, we use seven ecoacoustic metrics and acoustically-derived bird species richness across a heterogeneous landscape composed of densely urbanized, suburban, rural, protected, and recently burned lands in Sonoma County, California, U.S.A., to explore spatiotemporal patterns in ecoacoustic measurements. Predictive models of ecoacoustic metrics driven by land-use/land-cover, remotely-sensed vegetation structure, anthropogenic impact, climate, geomorphology, and phenology variables capture landscape and daily differences in ecoacoustic patterns with varying performance (avg. R 2 = 0.38 ± 0.11) depending on metric and period-of-day and provide interpretable patterns in sound related to human activity, weather phenomena, and animal activity. We also offer a case study on the use of the data-driven prediction of biophony to capture changes in soniferous species activity before (1–2 years prior) and after (1–2 years post) wildfires in our study area and find that biophony may depict the reorganization of acoustic communities following wildfires. This is demonstrated by an upward trend in activity 1–2 years post-wildfire, particularly in more severely burned areas. Overall, we provide evidence of the importance of climate, spaceborne-lidar-derived forest structure, and phenological time series characteristics when modeling ecoacoustic metrics to upscale site observations and map ecoacoustic biodiversity in areas without prior acoustic data collection. Resulting maps can identify areas of attention where changes in animal communities occur at the edge of human and natural disturbances.

Composition of Stream Dissolved Organic Matter Across Canadian Forested Ecozones Varies in Three Dimensions Linked to Landscape and Climate

AbstractDissolved organic matter (DOM) is a key variable influencing aquatic ecosystem processes. The concentration and composition of DOM in streams depend on both the delivery of DOM from terrestrial sources and on aquatic DOM production and degradation. However, there is limited understanding of the variability of stream DOM composition at continental scales and the influence of landscape characteristics and disturbances on DOM across different regions. We assessed DOM composition in 52 streams at seven research sites across six forested ecozones in Canada in 2019–2022 using 26 indices derived from five analytical approaches: absorbance and fluorescence spectroscopy, liquid chromatography—organic carbon detection, Fourier‐transform ion cyclotron resonance mass spectrometry, and asymmetric flow field‐flow fractionation. Combined analyses showed clear clustering and redundancy across analytical techniques, and indicated that compositional variations were primarily related to three axes of DOM composition: (a) aromaticity, which was greater in low‐relief, wetland‐dominated catchments, (b) oxygenation, which was greater in colder and drier ecozones, and (c) biopolymer content, which was greater in lake‐influenced catchments. Variability in DOM composition among research sites was greater than variability of streams within a site and variability over time within a stream. Forest harvesting and wildfire disturbances had no common influence on DOM composition across research sites, emphasizing the need for regional studies. Our study provides a broad understanding of the variability of stream DOM composition and its associations with landscape and catchment characteristics at a subcontinental scale, and provides key insights for the choice and interpretation of DOM indices from various analytical approaches.

The grain size of sediments delivered to steep debris‐flow prone channels prior to and following wildfire

AbstractDebris flows are powered by sediment supplied from steep hillslopes where soils are often patchy and interrupted by bare‐bedrock cliffs. The role of patchy soils and cliffs in supplying sediment to channels remains unclear, particularly surrounding wildfire disturbances that heighten debris‐flow hazards by increasing sediment supply to channels. Here, we examine how variation in soil cover on hillslopes affects sediment sizes in channels surrounding the 2020 El Dorado wildfire, which burned debris‐flow prone slopes in the San Bernardino Mountains, California. We focus on six headwater catchments (&lt;0.1 km2) where hillslope sources ranged from a continuous soil mantle to 95% bare‐bedrock cliffs. At each site, we measured sediment grain size distributions at the same channel locations before and immediately following the wildfire. We compared results to a mixing model that accounts for three distinct hillslope sediment sources distinguished by local slope thresholds. We find that channel sediment in fully soil‐mantled catchments reflects hillslope soils (D50 = 0.1–0.2 cm) both before and after the wildfire. In steeper catchments with cliffs, channel sediment is consistently coarse prior to fire (D50 = 6–32 cm) and reflects bedrock fracture spacing, despite cliffs representing anywhere from 5% to 95% of the sediment source area. Following the fire, channel sediment size reduces most (5‐ to 20‐fold) in catchments where hillslope sources are predominantly soil covered but with patches of cliffs. The abrupt fining of channel sediment is thought to facilitate postfire debris‐flow initiation, and our results imply that this effect is greatest where bare‐bedrock cliffs are present but not dominant. A patchwork of bare‐bedrock cliffs is common in steeplands where hillslopes respond to channel incision by landsliding. We show how local slope thresholds applied to such terrain aid in estimating sediment supply conditions before two destructive debris flows that eventually nucleated in these study catchments in 2022.

Valuation of forest‐management and wildfire disturbance on water and carbon fluxes in mountain headwaters

AbstractRecent drought, wildfires and rising temperatures in the western US highlight the urgency of increasing resiliency in overstocked forests. However, limited valuation information hinders the broader participation of beneficiaries in forest management. We assessed how historical disturbances in California's Central Sierra Nevada affected live biomass, forest water use and carbon uptake and estimated marginal values of these changes. On average, low‐severity wildfire caused greater declines in forest evapotranspiration (ET), gross primary productivity (GPP) and live biomass than did commercial thinning. Low‐severity wildfires represent proxies for prescribed burns and both function as biomass removal to alleviate overstocked conditions. Increases in potential runoff over 15 years post‐disturbance were valued at $108,000/km2 for commercial thinning versus $234,000/km2 for low‐severity wildfire, based on historical water prices. Respective declines in GPP were valued at −$305,000 and −$1,317,000/km2, based on an average social cost of carbon. Considering biomass levels created by commercial thinning and low‐severity fire as more‐sustainable management baselines for overstocked forests, carbon uptake over 15 years post‐disturbance can be viewed as a benefit rather than loss. Realizing this benefit upon management re‐entry may require sequestering thinned material. High‐severity wildfire and clearcutting resulted in greater declines in ET and thus greater potential water benefits but also substantial declines in GPP and live carbon. These lessons from historical disturbances indicate what benefit ranges from fuels treatments can be expected from more‐sustainable management of mixed‐conifer forests and the importance of setting an appropriate baseline.

Low‐head dam fragmentation, habitat alteration, and invasive predators degrade a Western United States stream fish assemblage

AbstractDams fragment streams, alter hydrology and habitat, and facilitate establishment of nonnative species worldwide to the detriment of native biota. Understanding and mitigating these effects to conserve and restore stream fish assemblages has relied on short‐ and long‐term datasets to assess acute and chronic change through time, craft management strategies, and measure remediation success. We used sampling records collected over a 29‐year period (1993–2021) to examine likely causes of fish assemblage change in the Cache la Poudre River, Colorado, USA. Numerous low‐head dams have reduced connectivity and altered flow, temperature, and habitat in the transition zone, a reach that historically supported rare and sensitive taxa valuable to regional biodiversity. We found diversity, distribution, and abundance of native species declined since the early 1990s, with formerly rare taxa extirpated and some common species becoming rare. Native taxa remained numerically dominant in warmer downstream reaches most affected by streamflow diversion but were incrementally reduced in richness and abundance upstream of low‐head dams without fishways. Concurrently, nonnative Brown Trout Salmo trutta increased in distribution and abundance, dominating upstream reaches that receive cooler and more stable flows, and expanding into downstream reaches where they were formerly absent, with likely negative consequences for native fishes. In the absence of mitigation, these collective effects, plus recent wildfire disturbance and future water development, will continue to degrade stream fish assemblages in our study area, and worldwide, where resource managers face the often‐competing interests of conserving native species, providing recreational fisheries, and meeting increasing water demands.

Fuel build-up promotes an increase in fire severity of reburned areas in fire-prone ecosystems of the western Mediterranean Basin

BackgroundFire-vegetation feedbacks can modulate the global change effects conducive to extreme fire behavior and high fire severity of subsequent wildfires in reburn areas by altering the composition, flammability traits, and spatial arrangement of fuels. Repeated, high-severity wildfires at short return intervals may trigger long-term vegetation state transitions. However, empirical evidence about these feedbacks is absent in fire-prone ecosystems of the western Mediterranean Basin, where the response of fire activity has been enhanced by contemporary socioeconomic and land-use changes. Here, we evaluated whether fire severity differs between initial burns and subsequent wildfires in reburn areas (fire-free periods = 10–15 years) of maritime pine and Aleppo pine forests, holm oak woodlands, and shrublands in the western Mediterranean Basin, and whether there is a relationship between the severity of such interactive wildfire disturbances. We also tested how the type of ecosystem and changes in vegetation structure after the initial wildfires influence these relationships. We leveraged Landsat-based fire severity estimates for initial and last wildfires using the Relativized Burn Ratio (RBR) and Light Detection and Ranging (LiDAR) data acquired before the last wildfire.ResultsFire severity of the last wildfire was significantly higher than that of the initial wildfire for each dominant ecosystem type in reburn areas. These differences were very pronounced in maritime pine forests and shrublands. For consistency, the same patterns were evidenced for the fire severity in reburn and first-entry areas of the last wildfire for each dominant ecosystem type. Fire severity of the last wildfire in forests and woodlands (particularly maritime pine-dominated) raised with increasing severity of the previous wildfire to a greater extent than in shrublands. Pre-fire fuel density in the lower vegetation strata (up to 4 m high in maritime and Aleppo pine forests, as well as in shrublands, and up to 2 m high in holm oak forests) was significantly higher in reburn than in first-entry areas of the last wildfire.ConclusionsOur results suggest that land managers should promote more fire-resistant landscapes to high fire severity by minimizing fuel build-up and thus fire hazard through pre-fire fuel reduction treatments such as prescribed burning.

Oil sands restoration with warm‐adapted trees improves outcomes under moderate but not severe warming scenarios

AbstractSuccessful restoration of human‐disturbed landscapes and ecosystems will be increasingly compromised by the impacts of climate warming. Assisted migration and climate‐informed restoration, in which populations and species adapted to future climates are selected for restoration planting, have emerged as management tools to mitigate climate change effects. However, it is unclear whether climate‐informed restoration could offset the negative effects of climate change and enable successful restoration. We used a forest landscape model to evaluate the potential for reclamation activities to restore western Canadian boreal forest landscapes severely degraded by oil sands mining. We parametrized tree populations adapted to growing in warmer climates and then simulated the planting of local or southern tree populations under different climate change, mining, and wildfire disturbance scenarios. We found that planting trees better adapted to a warmer climate mitigated climate‐change and wildfire‐caused decreases in biomass across the landscape, but only under moderate climate change scenarios. The compensatory effect of planting populations adapted to warmer southern climates disappeared under a more severe climate change scenario. The advantage of planting southern populations also disappeared under wildfire scenarios, generally doubling the biomass loss compared with scenarios without wildfire. With wildfire and strong climate change effects, forest cover disappeared from much of the landscape, regardless of the planting scenario, causing it to change markedly from present‐day continuous boreal forest cover. We argue that such conditions would have large ecological and economic consequences. Scenario modeling with forest landscape models could be used as a tool to identify the long‐term success of restoration actions and to understand possible consequences of climate‐informed restoration.

Development of The Navigator: A Lagrangian sensing system to characterize surface freshwater ecosystems

Most freshwater aquatic studies rely on Eulerian monitoring, i.e., water quality and quantity are monitored using grab samples or semi-continuous sensors deployed at fixed cross-sections. While Eulerian monitoring is practical, it provides a limited understanding of spatial and temporal heterogeneity. We designed and built The Navigator, a Lagrangian (i.e., along a flow path) monitoring system that offers cost-effective solutions for in-situ, real-time data collection in surface freshwater ecosystems. The Navigator features a suite of technologies, including an autonomous surface vehicle with GPS and LTE connectivity, water quality sensors, a depth sonar, a camera, and a webpage dashboard to visualize real-time data. With these technologies, The Navigator provides insight into where, how, and why water quality and quantity change over time and space as it moves with the current or follows user-specified pathways. We tested The Navigator monitoring water quality parameters at high spatial-temporal resolution in multiple surface water bodies in New Mexico (USA) to: (1) identify water quality changes associated with land use changes along a 7th-order reach in the Rio Grande, (2) identify the fate of wildfire disturbances ∼175 km downstream of a burned watershed affected by the largest wildfire ever recorded in the state, (3) monitor the water quality of a recreational fishing pond in the City of Albuquerque. Our three successful tests confirm that The Navigator is an affordable (USD 5,101 in 2023) monitoring system that can be used to address questions involving mass and energy balances in surface waters.

Forest resilience and regeneration dynamics following wildfire disturbance

AbstractSpecies that are adapted to specific disturbance regimes may be sensitive to changes such as severity, frequency, and extent of ecosystem perturbation. Along range margins, these sensitivities may be exacerbated by concurrent changes in climate resulting in loss of resilience and shifts to alternative ecosystem states. Pinus banksiana (jack pine) is a serotinous species dependent on fire disturbance to open cones, release seed, reduce understory competition, and expose mineral soil. The Altona Flat Rock in northern New York is a globally rare sandstone pine barrens, at the southern edge of jack pine's range. In the summer of 2018, a wildfire burned approximately 200 ha of the Flat Rock barrens, providing the opportunity to study post‐disturbance jack pine and understory resilience. We aimed to establish if jack pine regeneration would occur, and if so, would it be influenced by fire severity, pre‐fire stand characteristics, and competition. We predicted that higher seedling densities would be associated with higher burn severity, higher pre‐fire jack pine stand density, and lesser understory competition. We collected seedling density and understory composition data annually from 2019 to 2022 across 45 plots spanning the disturbed and adjacent undisturbed barrens. In 2021 and 2022, seedling heights were also collected. Seedling densities following the disturbance ranged from 275,385 to 390,513 ha−1; = 357,821 ha−1. Jack pine seedling density was positively associated with fire severity and moss abundance for all years. Pre‐fire stand density along with ericaceous shrub, grass, and duff abundance were also positively associated with seedling density in some years. Seedling height was positively associated with fire severity along with grass and blueberry abundance. These factors, for both establishment/survival and growth, point to the importance of seed supply, microsite conditions, and facilitation in jack pine regeneration success. At this point, it does not appear that the interaction of disturbance with changing climate has shifted enough to prevent the recovery of this ecosystem to its pre‐disturbance jack pine‐dominated state. However, ongoing climate change may still have an impact on seedlings/saplings as this forest continues to mature.

A multi-benefit framework for funding forest management in fire-driven ecosystems across the Western U.S.

Forests across the Western U.S. face unprecedented risk due to historic fire exclusion, environmental degradation, and climate change. Forest management activities like ecological thinning, prescribed burning, and meadow restoration can improve landscape resilience. Resilient forests are at a lower risk of high-intensity wildfires, drought, insects, and other disturbances and provide a wide range of benefits to ecosystems and communities. However, insufficient funding limits implementation of critically needed management. To address this challenge, we propose a multi-benefit framework that leverages the diverse benefits of forest management to engage a suite of stakeholders in sharing project costs. We take a three-pronged approach to develop our conceptual model: examining existing frameworks for environmental project implementation, conducting a literature review of forest management benefits, and evaluating case studies. Through our framework, we describe the steps to engage partners, starting by identifying benefits that could accrue to potential public and private beneficiaries, and moving through an iterative and collaborative process of valuing benefits, which can accrue over different spatial and temporal scales, in close consultation with potential beneficiaries themselves. The aim of this approach is to stack funding streams associated with each valued benefit to fully fund a given forest management project. The multi-benefit framework has the potential to unlock new sources of funding to meet the exceptional challenges of climate and wildfire disturbances. We apply the framework to dry forests of the Western U.S., but opportunities exist for expanding and modifying this approach to any geography or ecosystem where management provides multiple benefits.

Wildfire facilitates upslope advance in a shade-intolerant but not a shade-tolerant conifer.

Wildfires may facilitate climate tracking of forest species moving upslope or north in latitude. For subalpine tree species, for which higher elevation habitat is limited, accelerated replacement by lower elevation montane tree species following fire may hasten extinction risk. We used a dataset of postfire tree regeneration spanning a broad geographic range to ask whether the fire facilitated upslope movement of montane tree species at the montane-to-subalpine ecotone. We sampled tree seedling occurrence in 248 plots across a fire severity gradient (unburned to >90% basal area mortality) and spanning ~500 km of latitude in Mediterranean-type subalpine forest in California, USA. We used logistic regression to quantify differences in postfire regeneration between resident subalpine species and the seedling-only range (interpreted as climate-induced range extension) of montane species. We tested our assumption of increasing climatic suitability for montane species in subalpine forest using the predicted difference in habitat suitability at study plots between 1990 and 2030. We found that postfire regeneration of resident subalpine species was uncorrelated or weakly positively correlated with fire severity. Regeneration of montane species, however, was roughly four times greater in unburned relative to burned subalpine forest. Although our overall results contrast with theoretical predictions of disturbance-facilitated range shifts, we found opposing postfire regeneration responses for montane species with distinct regeneration niches. Recruitment of shade-tolerant red fir declined with fire severity and recruitment of shade-intolerant Jeffrey pine increased with fire severity. Predicted climatic suitability increased by 5% for red fir and 34% for Jeffrey pine. Differing postfire responses in newly climatically available habitats indicate that wildfire disturbance may only facilitate range extensions for species whose preferred regeneration conditions align with increased light and/or other postfire landscape characteristics.

Effects of wildfire disturbance on forest soil microbes and colonization of ericoid mycorrhizal fungi in northern China

Wildfires affect forest succession and restoration by changing the community structure of soil microorganisms. Mycorrhizal formation is essential for plant growth and development. However, the driving mechanism of their natural succession after wildfire is still unclear. In this study, we examined the community structure of soil bacteria and fungi along a time series of natural recovery after wildfires in the Greater Khingan Range of China (2020 fires, 2017 fires, 2012 fires, 2004 fires, 1991 fires, and unburned). By exploring the effects of wildfire on plant traits, fruit nutrition, colonization of mycorrhizal fungi and its influencing mechanism. The results show that natural succession after wildfires significantly changed the community composition of bacteria and fungi, with β diversity having a greater impact but less impact on the α diversity of microorganisms. Wildfires significantly changed plant traits and fruit nutrient content. The changes in colonization rate and customization intensity of mycorrhizal fungi were caused by increased MDA content and soluble sugar content and increased MADS-box gene and DREB1 gene expression in lingonberry (Vaccinium vitis-idaea L.). Our results showed that the soil bacterial and fungal communities in the boreal forest ecosystem changed significantly during wildfire recovery and changed the colonization rate of lingonberry mycorrhizal fungi. This study provides a theoretical basis for the restoration of forest ecosystems after wildfires.

Implications of fire-induced evapotranspiration shifts for recharge-runoff generation and vegetation conversion in the western United States

Wildfire has been shown to increase, decrease, or have no detectable effect on actual evapotranspiration (ETa) fluxes in the western United States. Where disturbance-induced shifts are significant, source-water hydrology may be impacted as ETa constitutes the largest outgoing water flux in much of the arid West. We conducted pixel-scale analysis of 30-m ETa data and various meteorologic and landscape variables at 13 burn scars to understand how wildfire disturbance impacted hillslope-to-burn scar-scale hydrology and vegetation conversion. Significant fire-induced ETa reductions (between approximately −15 to −50%) were detected at nine burn scars through the tenth post-fire year, while ETa recovery rate varied substantially by ecoregion and pre-fire vegetation type. Along elevation gradients, both climate and land disturbance influenced the location of runoff/recharge generation zones, and more net water was generated from a snow-dominated burn scar in dry post-fire years than in wet pre-fire years. However, especially in arid locations where ETa is water-limited, compensatory ETa pathways may be more likely to dampen fire effects on total basin water yield where intact vegetation is located between the disturbance footprint and the basin outlet. Relationships between post-fire ETa shifts and early-successional vegetation conversion were also tracked. The majority of burn scars with significant fire-induced ETa reductions experienced conversion patterns typical of the western United States following stand-replacing disturbance, with forests converting to shrub/scrub and/or grassland/herbaceous cover through at least the end of the study period (eight to 15 years depending on date of the fire event). This could have important implications for high-elevation, snow-dominated watersheds – some of the most critical source water areas - as previous research indicates that wildfire activity is moving upslope and into vegetation communities that have not evolved to withstand fire. Finally, we show that much of the Colorado River Basin’s high-yield source water areas are vulnerable to the fire-induced ETa reductions and vegetation conversion observed herein. As such, water managers in the Colorado River Basin can anticipate changes in burn scar hydrology and snowpack mechanics following fire disturbance.

Wildfire promotes the invasion of Robinia pseudoacacia in the unmanaged Mediterranean Castanea sativa coppice forests

In the Mediterranean region of southern Europe, Castanea sativa Mill. (Castanea) coppice stands are being invaded by non-native pioneer tree species due to recurrent coppicing and wildfire disturbances. There is a need to control the spread of non-native tree species in Castanea coppices due to their pivotal socio-economic role, however, to facilitate this, further research into invasive strategies and their interactions with disturbances is required. The non-native Robinia pseudoacacia L. (Robinia) has widely colonized the overaged and unmanaged Castanea coppice forests in Vesuvius National Park, which were disturbed by the low-severity fires in the summer of 2017. Here, we aimed to assess the functional traits conferring a competitive advantage to the Robinia over Castanea and the changes in spatial stand patterns driven by wildfire disturbance. To achieve this we assessed the spatial stem patterns, regeneration strategies, and conducted field-assessments and remote sensing of the spring leaf phenology of both Castanea and Robinia in five 300–600 m2 plots. After the 2017 wildfire, root suckers constituted 72% (±12) of the Robinia vegetative living sprouts and occurred up to a distance of 10 m from the adult parent trees under the canopy of the Castanea trees. NDVI-based estimates at the start of the growing season (sos) in Castanea occurred over a 7 day period, from DOY 118–124, increasing at a rate (rsp) of 0.10–0.16, in agreement with the field-based assessment of spring leaf phenology. In Robinia, the sos estimated at DOY 109 from the NDVI seasonal trajectory disagreed with the field-based observations, which started later than Castanea, after approximately DOY 133. Here, the high percentage cover (∼90%) of the understory species influenced NDVI-based estimates of Robinia leaf spring phenology. The results suggest that low-severity wildfires increased the invasiveness of Robinia, and that vegetative regeneration strategies, rather than earlier spring phenology, conferred a competitive advantage in the fire-disturbed Castanea coppice stands. The results thus suggest that appropriate management of invasive Robinia trees to conserve the continuous canopy cover of Castanea stands should guide nature-based solutions to control the spread of non-native tree species.