Fire Disturbance Research Articles

Siberian carbon sink reduced by forest disturbances

Siberian forests are generally thought to have acted as an important carbon sink over recent decades, but exposure to severe droughts and fire disturbances may have impacted their carbon dynamics. Limited available forest inventories mean the carbon balance remains uncertain. Here we analyse annual live and dead above-ground carbon changes derived from low-frequency passive microwave observations from 2010 to 2019. We find that during this period, the carbon balance of Siberian forests was close to neutral, with the forests acting as a small carbon sink of $$+ 0.02_{ + 0.01}^{ + 0.03}$$ PgC yr−1. Carbon storage in dead wood increased, but this was largely offset by a decrease in live biomass. Substantial losses of live above-ground carbon are attributed to fire and drought, such as the widespread fires in northern Siberia in 2012 and extreme drought in eastern Siberia in 2015. These live above-ground carbon losses contrast with ‘greening’ trends seen in leaf area index over the same period, a decoupling explained by faster post-disturbance recovery of leaf area than live above-ground carbon. Our study highlights the vulnerability of large forest carbon stores in Siberia to climate-induced disturbances, challenging the persistence of the carbon sink in this region of the globe. Carbon sequestration by Siberian forests has been low over the past decade due to disturbances that have decreased live biomass and increased dead wood, according to passive microwave observations.

Spatiotemporal Assessment of Forest Fire Vulnerability in China Using Automated Machine Learning

Frequent forest fires cause air pollution, threaten biodiversity and spoil forest ecosystems. Forest fire vulnerability assessment is a potential way to improve the ability of forests to resist climate disasters and help formulate appropriate forest management countermeasures. Here, we developed an automated hybrid machine learning algorithm by selecting the optimal model from 24 models to map potential forest fire vulnerability over China during the period 2001–2020. The results showed forest aboveground biomass (AGB) had a vulnerability of 26%, indicating that approximately 2.32 Gt C/year of forest AGB could be affected by fire disturbances. The spatiotemporal patterns of forest fire vulnerability were dominated by both forest characteristics and climate conditions. Hotspot regions for vulnerability were mainly located in arid areas in western China, mountainous areas in southwestern China, and edges of vegetation zones. The overall forest fire vulnerability across China was insignificant. The forest fire vulnerability of boreal and temperate coniferous forests and mixed forests showed obviously decreasing trends, and cultivated forests showed an increasing trend. The results of this study are expected to provide important support for the forest ecosystem management in China.

Impact of wildfire on soil carbon and nitrogen storage and vegetation succession in the Nanweng'he National Natural Wetlands Reserve, Northeast China

In boreal regions, wildfires have a major impact on vegetation and permafrost. The ecosystem-protected Xing’an permafrost is sensitive to warming climate and wildfires, particularly on the southern margin of boreal coniferous forest and patchy permafrost zone. However, it remains unclear how fire disturbances are linked with changes in ecosystem composition and soil nutrients in the permafrost zones of Northeast China. Here, 13 years after the fire in the Yile’huli mountain knots, we investigated the parameters like vegetation cover, ground temperatures, active layer thickness, and soil carbon and nitrogen storage at burned and unburned sites of shrub wetlands. The fire resulted in ground warming of 0.1–5.0 °C at depths of 1.0–20.0 m and active layer deepening of 0.5 m, and gravimetric soil moisture content increasing of 26%-266%. Fire also increased the number of herbs and tall shrubs. After the fire, graminoids and tall shrubs increased significantly, and the species of herbs increased by five species. However, dwarf shrubs like Ledum palustre and Vaccinium uliginosum were missing from the burned site. A massive loss of total organic carbon (TOC) (248.40 t C/hm2) and nitrogen (TN) (11.87 t N/hm2) was observed by comparing their storage at burned and unburned sites. These results highlighted that the post-fire responses of vegetation cover and TOC and TN storage were dependent on the thermal regimes of near-surface permafrost and active layer, recovery of vegetation and organic layer, and soil moisture content. This study can provide an important reference for carbon storage and emission in boreal shrub wetlands under a warming climate and increasing fire disturbances.

Season and prey identity mediate the effect of predators on parasites in rodents: a test of the healthy herds hypothesis.

The healthy herds hypothesis (HHH) suggests that predators decrease parasitism in their prey. Repeated tests of this hypothesis across a range of taxa and ecosystems have revealed significant variation in the effect of predators on parasites in prey. Differences in the response to predators (1) between prey taxa, (2) between seasons, and (3) before and after catastrophic disturbance are common in natural systems, but typically ignored in empirical tests of the HHH. We used a predator exclusion experiment to measure the effect of these heterogeneities on the tri-trophic interaction among predators, parasites and prey. We experimentally excluded mammalian predators from the habitats of hispid cotton rats (Sigmodon hispidus) and cotton mice (Peromyscus gossypinus) and measured the effect of exclusion on gastrointestinal parasites in these rodents. Our experiment spanned multiple seasons and before and after a prescribed burn. We found that the exclusion of the same predators had opposite effects on the parasites of small mammal prey species. Additionally, we found that the effect of mammal exclusion on parasitism differed before versus after fire disturbance. Finally, we saw that the effect of predator exclusion was highly dependent on prey capture season. Significant effects of exclusion emerged primarily in the fall and winter months. The presence of so many different effects in one relatively simple system suggests that predator effects on parasites in prey are highly context dependent.

Wildfire affects boreal forest resilience through post-fire recruitment in Northeastern China

Climate change has increased the severity, frequency, and impact of fire disturbance on boreal forests worldwide. Unusual fire events can trigger a shift from needle-leaf dominated forests to broad-leaf dominated forests, altering the original succession trajectory. Thus, it is necessary to identify how altered fire regimes affect boreal forest resilience or capacity to recover after fire disturbance. In this study, we used the post-fire tree recruitment density, the aboveground biomass, the understory shrub cover, and the herb cover as indicators of forest resilience. We explored the links between patterns of resilience and burn severity across topographic positions in two post-fire forests with different time since fire. We quantified how burn severity, time since fire, and topographic position affect resilience indicators related to post-fire overstory and understory recruitment in the Great Xing’an Mountains of Northeastern China. We found that burn severity and topographic position exhibited strong influences on post-fire overstory tree recruitment and aboveground biomass. Severe fire promoted deciduous needle-leaf tree (larch) recruitment in lowland sites by removing a thick organic layer. In contrast, severe fire promoted broad-leaf tree (birch and aspen) recruitment in south-facing upland sites with relatively warmer and drier microclimates. Therefore, severe fire disturbance may trigger a post-fire species shift from larch dominated forest to broad-leaf forest, especially in south-facing upland sties. We also found that the understory may be more resilient to high severity fire than the overstory, because severity had short-term effects on post-fire understory recruitment. Our study suggested that burn severity was a crucial factor that affects boreal forest resilience through substantially altering resilience indicators related to post-fire overstory tree recruitment.

Multi-scale quantification of anthropogenic, fire, and drought-associated forest disturbances across the continental U.S., 2000–2014

Our understanding of broad-scale forest disturbances under climatic extremes remains incomplete. Drought, as a typical extreme event, is a key driver of forest mortality but there have been no reports on continental-scale quantification of its impact on forest mortality or how it compares to other natural or anthropogenic drivers. Thus, our ability to understand and predict broad-scale carbon cycling in response to changing climate and extreme events is limited. In this study, we applied an attribution approach based on different sources of data to quantify the area and potential carbon loss/transfer in continental U.S. (CONUS) from four types of disturbance: (1) anthropogenic (especially timber harvest); (2) fire; (3) drought-associated; and (4) other from 2000 to 2014. Our results showed that anthropogenic disturbances, fire, drought-associated disturbances, and other disturbances accounted for 54.3, 10.7, 12.7, and 22.3% of total canopy area loss, respectively. Anthropogenic disturbance was the most important driver contributing to 58.1% potential carbon loss/transfer in CONUS for 2000–2014. The potential carbon loss/transfer from natural disturbances (fire, drought, and other) for the same study period accounted for approximately 41.9% of the total loss/transfer from all agents, suggesting that natural disturbances also played a very important role in forest carbon turnover. Potential carbon loss/transfer associated with drought accounted for approximately 11.6% of the total loss/transfer in CONUS, which was of similar magnitude to potential carbon loss/transfer from fire (∼11.0%). The other natural disturbance accounted for 19.3% of potential carbon loss/transfer. Our results demonstrated the importance of the impacts of various disturbances on forest carbon stocks at the continental scale, and the drought-associated carbon loss/transfer data developed here could be used for evaluating the performance of predictive models of tree mortality under droughts.

Contrasting effects of low-severity fire on stemflow production between coexisting pine and oak trees

As climate change intensifies, fires events are predicted to increase in forest ecosystems. Fire alters the ecosystem structure and consequently, the hydrological cycle. However, little is known about the impacts of forest fire on stemflow. A field experiment was conducted to evaluate the short-term response of stemflow production to low-severity fire in a coniferous and broadleaved mixed forest. Results demonstrated low-severity fire changed stemflow yield and had insignificant effect on the correlation between stemflow efficiency and rainfall or plant morphological variables. In unburned site Quercus acutissima and Pinus massoniana and in burned site Q. acutissima and P. massoniana, stemflow percentage averaged 3.86, 0.37, 1.20, and 0.47 %, whereas funneling ratio averaged 38.8, 4.2, 11.4, and 5.1, respectively. Fire substantially decreased the stemflow percentage and funneling ratio of Q. acutissima (P < 0.05) and slightly enhanced P. massoniana (P > 0.05). The responses of stemflow production to fire differed significantly between oak and pine trees. Fire made Q. acutissima become less effective in funneling rain to the forest ground, which is attributed to that the scaly bark was burned to highly furrowed bark that delivers less water to tree base. Burned P. massoniana was more productive in draining stemflow relative to unburned trees and is attributed to the bark which was still flaky regardless of. Additionally, the higher canopy openness allows more rain to funnel to the trunk. Stemflow efficiency was reduced in response to fire and limited the transfer of water and nutrients from canopy to soil and can reduce the competitiveness of Q. acutissima after fire disturbance.

Plant functional type aboveground biomass change within Alaska and northwest Canada mapped using a 35-year satellite time series from 1985 to 2020

Changes in vegetation distribution are underway in Arctic and boreal regions due to climate warming and associated fire disturbance. These changes have wide ranging downstream impacts—affecting wildlife habitat, nutrient cycling, climate feedbacks and fire regimes. It is thus critical to understand where these changes are occurring and what types of vegetation are affected, and to quantify the magnitude of the changes. In this study, we mapped live aboveground biomass for five common plant functional types (PFTs; deciduous shrubs, evergreen shrubs, forbs, graminoids and lichens) within Alaska and northwest Canada, every five years from 1985 to 2020. We employed a multi-scale approach, scaling from field harvest data and unmanned aerial vehicle-based biomass predictions to produce wall-to-wall maps based on climatological, topographic, phenological and Landsat spectral predictors. We found deciduous shrub and graminoid biomass were predicted best among PFTs. Our time-series analyses show increases in deciduous (37%) and evergreen shrub (7%) biomass, and decreases in graminoid (14%) and lichen (13%) biomass over a study area of approximately 500 000 km2. Fire was an important driver of recent changes in the study area, with the largest changes in biomass associated with historic fire perimeters. Decreases in lichen and graminoid biomass often corresponded with increasing shrub biomass. These findings illustrate the driving trends in vegetation change within the Arctic/boreal region. Understanding these changes and the impacts they in turn will have on Arctic and boreal ecosystems will be critical to understanding the trajectory of climate change in the region.

Community Responses to Fire: A Global Meta-Analysis Unravels the Contrasting Responses of Fauna to Fire

Globally, wildfires and prescribed fires are becoming more prevalent and are known to affect plant and animals in diverse ecosystems. Understanding the responses of animal communities to fire is a central issue in conservation and a panacea to predicting how fire regimes may affect communities and food webs. Here, a global meta-analysis of 2581 observations extracted from 208 empirical studies were used to investigate the effect of fire on aboveground and belowground fauna (e.g., bacteria, fungi, small mammals, arthropods). Overall, results revealed that fire had a negative effect on biomass, abundance, richness, evenness, and diversity of all faunas. Similarly, when considering wildfires and prescribed fires the data revealed that both fire regimes have negative effects on fauna. Similarly, fire had negative impacts on aboveground and aboveground fauna across most biomes and continents of the world. Moreover, there was little evidence of changes in pH, moisture and soil depth on soil organisms suggesting that other factors may drive community changes following a fire disturbance. Future research in fire ecology should consider the effects of fire across several species and across larger geospatial scales. In addition, fire effects on faunal community structure must be studied under contrasting global fire regimes and in light of the effects of climate change.

Short-term effects of wildfire on soil arthropods in a semi-arid grassland on the Loess Plateau.

Fires lead to dramatic shifts in ecosystems and have a large impact on the biota. Soil organisms, especially soil fauna, are often used as indicators of environmental change. At present, minimal attention has been paid to using soil fauna as an indicator of environmental change after a fire. Here, a field survey of burnt herbaceous vegetation in semi-arid areas was conducted to determine the response of soil arthropods to fire and their short-term recovery after fire. Overall, the abundance and biomass of soil arthropods was more sensitive to fire than the number of groups. The number of soil arthropod groups, especially the dominant groups (mites and springtails), was not significantly affected by wildfires. At the unburned site, soil arthropod abundance showed significant seasonal shifts that may be related to the vegetation properties, temperature, and precipitation caused by seasonal changes. In contrast, soil arthropods at the burnt sites showed a delayed recovery and had only reached 56%-82%, 17%-54%, and 91%-190% of the biomass in the unburnt forest at the 3, 6, and 9 months after the burning event. Our findings of soil arthropod abundance changes in the present study suggest that fire-induced changes in soil and vegetation properties (e.g., AN, LT, and VC) were crucial factors for the changes in soil arthropod abundance in this semi-arid grassland. We conclude that fire disturbance reduces the seasonal sensitivity of soil arthropods by altering their habitat. This study furthers our understanding of wildfire impact recovery by documenting the short-term temporal dynamics of soil arthropods.

Effects of topography and historical human disturbance on the current-day distribution of Betula davurica in a secondary deciduous forest in central Japan

ABSTRACT Betula davurica is a relict species in Japan of which distribution is influenced by topography at local scale. This species may also be dependent on disturbance for regeneration. However, no studies found that estimate and compare the effects of topography and human disturbance on abundance of this species. Focusing on abandoned charcoal kilns and charcoals in the surface soil as proxies for historical disturbance, we assessed the status of B. davurica in a secondary deciduous broad-leaved stand in central Japan. Although B. davurica was once a dominant species in the study area, its regeneration has stagnated after decline of charcoal production. The oldest individual was 90 years of age, suggesting that the current-day population established following a period of grassland dominance 100 years ago. We found multiple abandoned kilns, as well as widespread charcoal fragments in the surface soils of the study area. Both individuals, that had established prior to and following the decline of charcoal production, tended to be distributed at sites with other tree species with smaller DBH and at gentle slope. Location of charcoal kilns did not significantly affect the distribution of this species. It is possible that B. davurica prefers to gentle slope at the sites where historical logging for charcoal production and fire disturbance had influenced at the whole. Cessation of logging and fire disturbance have likely inhibited the regeneration of B. davurica. Logging of other tree species around at gentle slope may be necessary for the survival of this species.

Research progress on the influence of forest fire on the eco-stoichiometric characteristics of carbon, nitrogen and phosphorus in forest ecosystem

Forest fire can change the eco-stoichiometric characteristics of forest ecosystem elements, reflect the biogeochemical cycle change mode of forest ecosystem environment after fire, and clarify the eco-stoichiometric characteristics of carbon (C), nitrogen (N), phosphorus (P) in forest ecosystem under forest fire disturbance, which is very important for understanding the response mechanism of forest ecosystem to forest fire disturbance. By consulting a large number of relevant literatures, the author summarized and analyzed the impact mode of forest fire disturbance on the C–N–P eco-stoichiometric characteristics of forest ecosystem, as well as the impact of forest fire disturbance on the C–N–P eco-stoichiometric characteristics of plants, C–N–P eco-stoichiometric characteristics of litter, and C–N–P eco-stoichiometric characteristics of soil. It is considered that the C–N–P eco-stoichiometric characteristics of forest ecosystem are mainly affected by fire factors (fire intensity, fire frequency, recovery time after fire), vegetation types and soil properties. In view of the scientific problems that forest fire urgently needs to be solved in the study of forest ecosystem eco-stoichiometry, three aspects: the impact mechanism of forest fire disturbance on the homeostasis of plant eco-stoichiometry, the study of multi-element eco-stoichiometry under forest fire disturbance, the establishment of the eco-chemometrics relationship of the plant–litter–soil composite system under the interference of forest fire are proposed, in order to deeply understand the plant regulation strategy under the interference of forest fire, clarify the mutual coupling mechanism between multiple chemical elements after the interference of forest fire, and improve the relationship between the input and output of aboveground and underground nutrients with the plant–litter–soil as a composite whole, which is of great significance for a deep understanding of the nutrient cycle and balance of the forest ecosystem under the background of global climate change, and reasonable formulation of forest fire management measures.

Post‐fire restoration of Sphagnum bogs in the Tasmanian Wilderness World Heritage Area, Australia

Sphagnum bogs in Australia are small, with a limited distribution, but of high conservation value. They are restricted to cool, wet environments that are typically fire free and are poorly adapted to recover from fire disturbance, unlike most Australian flora. Increased fire activity due to anthropogenic climate change is threatening Sphagnum bogs. This increased threat has stimulated interest in their restoration. Compared with the northern hemisphere, there have been few studies of the ecology of Sphagnum restoration in the southern hemisphere. Here, we report on a field experiment in Tasmania, in an area burned by an extensive fire in 2016. We investigated the role of shade, fertilizer and transplants, factors demonstrated to be important in the restoration of burnt bogs on the Australian mainland. Treatments commenced three to 4 years after the fire. Overall, we found that fire‐damaged Sphagnum recovers very slowly, and that there was no recovery in severely burned areas. The addition of shade increased recovery of damaged Sphagnum, but fertilizer was harmful, even to healthy Sphagnum. Transplants in fire‐killed Sphagnum grew poorly in both moderately and severely burnt Sphagnum areas. Our findings support the use of shading in post‐fire Sphagnum recovery projects, although further work is required to determine the optimal approach and duration of providing shade.

Effects of fire disturbance on Larix gmelinii growth-climate relationship

• The reduction in larch growth after the fire lasts for 3–5 years. • Fire disturbance can cause changes in the radial growth-climate relationship of trees before and after a fire. • Moisture plays a role in promoting tree growth after a fire. Wildfire is a widespread phenomenon on the earth that has affected most ecosystems and is responsible for enormous economic and environmental damage. The Greater Khingan Mountains, the south boundary of the boreal forest, are a fire-prone area. However, the effect of fire disturbance on tree growth in response to climate warming is unknown. To predict the future dynamics of boreal forests after fire disturbance and their feedback on climate change, we analyzed Larix gmelinii growth-climate relationships in burned areas at six sites. The result showed a significant decline in the growth of burned trees in all locations except CY1 during the fire years. There was a growth release 3–5 years after the fire disturbance. The result of growth-climate relationships found that the response of CY1 and GH burned and unburned trees to mean temperature changed from a positive to a negative correlation before and after the fire year. Changes in tree growth response to PDSI were significant for both burned and unburned trees, suggesting that this change in response is related to fire disturbance and influenced by climate warming and drying in recent decades. The resistance of larch to fire showed that in the three years before and after the fire year, there was a significant reduction in the growth of burned larch, except for CY1. Our findings suggested that burned and unburned larch respond differently to climate change. Wildfires change the relationship between the radial growth of trees and climate factors. It may also alter the structural composition and biodiversity of boreal forests.

Hibbertia subvillosa (Dilleniaceae), a new Western Australian species segregated from H. striata

The south-west Western Australian species Hibbertia striata (Steud.) K.R.Thiele was reinstated in 2017, segregated from the historically misunderstood H. huegelii (Endl.) F.Muell. Since that time, field work has shown that H. striata comprises two distinctly different morphotypes. Plants from the eastern (drier) edge of the range are consistently single-stemmed at the base and are obligate reseeders after fire and other disturbances, in contrast to a more widespread morphotype (which includes the type of H. striata), that is abundantly multi-stemmed from the base and is a resprouter after fire. The difference in habit is consistent, has been observed at multiple locations and is consistently associated with distinct (though subtle) differences in leaf indumentum and morphology. The two morphotypes have not been found growing in mixed populations, due to habitat differences. Field work has shown that they are narrowly sympatric and do not intergrade where they approach each other; for this reason, and the consistency of both morphotypes over a wide range, they are regarded here as distinct species. The reseeding taxon has a validly published name, H. huegelii (Endl.) F.Muell. var. subvillosa Domin, and this is raised here to species rank as Hibbertia subvillosa (Domin) K.R.Thiele &amp; T.Hammer.

Evaluating hydrologic impact from concurrent insect and fire disturbances

Study RegionRio Grande Headwaters Study FocusIn the western US wildfires are increasing in duration and frequency, insect inducted forest mortality is widespread, and both wildfires and forest mortality are exacerbated by drought. These forest disturbances have hydrologic implications that are not always evident in the post-disturbance water budget – especially at the watershed outlet. In this study we evaluate two snow dominated paired catchment systems in the forested Rio Grande headwaters – where each impacted site was severely burned by the 2013 West Fork Complex (WFC) fire, and all sites (including control sites) were severely impacted by spruce beetle induced forest mortality from approximately 2005 to 2010. A combination of observed runoff, reanalysis precipitation, and remotely sensed evapotranspiration and vegetation metrics are used to evaluate the post-fire surface water budget (runoff and evapotranspiration) in paired catchments. New hydrological insights for the regionSignificant changes in post-fire surface water budget partitioning are not detectable, which is likely the result of decreased evapotranspiration due to insect-induced vegetation change in all study catchments prior to the fire. Our findings highlight the importance of considering overlapping disturbances, especially in paired catchment studies, and in alpine and subalpine forest regions like the Rio Grande headwaters that are increasingly prone to drought, insect mortality and wildfire. Our results also illustrate that insect induced forest mortality has significant implications for post-fire hydrology studies that rely on control-impact or before-and-after comparisons.

Millennial land use explains modern high‐elevation vegetation in the submediterranean mountains of Southern Europe

AbstractAimPinewood decline and scrubland expansion are major features of Late Holocene vegetation history in the Cantabrian Range. However, the drivers of this remarkable vegetation shift remain to be investigated. Here, we aim at disentangling the role of past land use and climate in shaping the high‐elevation Cantabrian landscape during the past two millennia.LocationCantabrian Range (northern Iberia).TaxaPinus sylvestris, Betula, Ericaceae, Juniperus, Poaceae.MethodsWe conducted high‐resolution multiproxy palaeoecological analyses (pollen, plant macrofossils, microscopic charcoal and dung fungi) on lake sediments from Lago del Ausente to reconstruct vegetation, fire occurrence and grazing through time. The chronology is based on 14C (terrestrial plant macrofossils) and 210Pb dating, and Bayesian age‐depth modelling (‘rbacon’). We carried out cross‐correlation analysis to quantify vegetation responses to fire.ResultsBetween 250 and 900 CE, the vegetation above 1700 m a.s.l. consisted of subalpine scrubland and scattered P. sylvestris trees/stands. Pinewoods with Betula were widespread at slightly lower elevation. This vegetation was resilient to moderate fire disturbance associated with limited pastoral activities. In contrast, enhanced fire occurrence alongside heavier pastoralism led to the demise of pinewoods and their replacement with Betula stands, subalpine scrublands, and meadows between 900 and 1100 CE. Later, the subalpine scrubland‐birch tree line did not respond to Little Ice Age cooling. However, further intensification of transhumant herding between 1300 and 1860 CE (‘La Mesta’) triggered birch decline and the establishment of the modern treeless landscape.Main conclusionsThe extant high‐elevation vegetation of the Cantabrian Range is largely the legacy of intensive land use starting more than one millennium ago. Recurrent and severe fires to promote pasturelands led to the regional extirpation of the previously widespread Pinus sylvestris. Future management should aim at preserving the valuable cultural open landscape of mountain scrubland and meadows and also at restoring patches of ancient pine‐birch woodlands.

Radar and multispectral remote sensing data accurately estimate vegetation vertical structure diversity as a fire resilience indicator

AbstractThe structural complexity of plant communities contributes to maintaining the ecosystem functioning in fire‐prone landscapes and plays a crucial role in driving ecological resilience to fire. The objective of this study was to evaluate the resilience to fire off several plant communities with reference to the temporal evolution of their vertical structural diversity (VSD) estimated from the data fusion of C‐band synthetic aperture radar (SAR) backscatter (Sentinel‐1) and multispectral remote sensing reflectance (Sentinel‐2) in a burned landscape of the western Mediterranean Basin. We estimated VSD in the field 1 and 2 years after fire using Shannon's index as a measure of vertical heterogeneity in vegetation structure from the vegetation cover in several strata, both in burned and unburned control plots. Random forest (RF) was used to model VSD in the control (analogous to prefire scenario) and burned plots (1 year after fire) using as predictors (i) Sentinel‐1 VV and VH backscatter coefficients and (ii) surface reflectance of Sentinel‐2 bands. The transferability of the RF model from 1 to 2 years after wildfire was also evaluated. We generated VSD prediction maps across the study site for the prefire scenario and 1 to 4 years postfire. RF models accurately explained VSD in unburned control plots (R2 = 87.68; RMSE = 0.16) and burned plots 1 year after fire (R2 = 80.48; RMSE = 0.13). RF model transferability only involved a reduction in the VSD predictive capacity from 0.13 to 0.20 in terms of RMSE. The VSD of each plant community 4 years after the fire disturbance was significantly lower than in the prefire scenario. Plant communities dominated by resprouter species featured significantly higher VSD recovery values than communities dominated by facultative or obligate seeders. Our results support the applicability of SAR and multispectral data fusion for monitoring VSD as a generalizable resilience indicator in fire‐prone landscapes.

Development and wildfire dynamics of dry coastal temperate forests, BC, Canada

The vegetation and fire history at the Coastal Douglas-fir (CDF) and Coastal Western Hemlock (CWH) boundary on east-central Vancouver Island was reconstructed. A basal non-arboreal assemblage at the most inland site likely represents an open parkland community during the cold early late-glacial interval. Widespread Pinus woodland followed under cold, dry climate, yielding to closed-canopy mixed conifer forest as climate moistened. While fire disturbance was initially rare, it increased in the late-glacial mixed conifer forest. In the early-Holocene, dry coastal temperate forest replaced the mixed-conifer assemblage. Fire disturbance was widespread, characterized by frequent, possibly lower severity burns. These CDF-like forests expanded northward and westward under warm, dry conditions, attaining maximum extent 9500 – 10 500 calendar years before present, retreating thereafter towards the modern CDF–CWH boundary, which established ∼6000 years ago as climate moistened. Quercus garryana communities were scattered along the coast at this time, maintained by surface fire. Throughout the remainder of the record, the forest canopy closed as modern forests developed and a mixed-severity fire regime developed. The extended early-Holocene range of CDF-like forest suggests that the existing CWHxm biogeoclimatic subzone may be replaced by CDF stands with climate change.

Trends analysis of rangeland condition monitoring assessment and projection (RCMAP) fractional component time series (1985–2020)

ABSTRACT : Rangelands have a dynamic response to climate change, fire, and other anthropogenic disturbances. The Rangeland Condition, Monitoring, Assessment, and Projection (RCMAP) product aims to capture this response by quantifying the percent cover of eight rangeland components, associated error, and trends across the western United States using Landsat from 1985 to 2020. The current generation of RCMAP has been improved with more training data, regional-scale Landsat composites, and more robust change detection. We assess the temporal patterns in each component with a linear model and a structural change method that determines break points using an 8-year temporal moving window. The linear and structural change methods generally agreed on patterns of change, but the latter found breaks more often, with at least one break point in most pixels. The structural change model provides more robust statistics on the significant minority of pixels with non-monotonic trends, while detrending some interannual signal potentially superfluous from a long-term perspective. Although break point density within one year of fire and vegetation treatments was ~10× and ~4× that of unburned areas, respectively, break point detection in the correct year of fire was only moderately accurate. Climate responses in break points proved more robust, with strong spatiotemporal relation in break point density with both aridity index values and aridity index change. Break point density strongly responds to both increased and decreased aridity and is reflective of ecosystem resilience. Data provide spatiotemporal information on the occurrence of breaks, but even more importantly, attribute those change events to specific component(s).