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Forest insect outbreaks cause large changes in ecosystem structure, composition, and function. Humans often respond to insect outbreaks by conducting salvage logging, which can amplify the immediate effects, but it is unclear whether logging will result in lasting differences in forest structure and dynamics when compared with forests affected only by insect outbreaks. We used 15 years of data from an experimental removal of Tsuga canadensis (L.) Carr. (Eastern hemlock), a foundation tree species within eastern North American forests, and contrasted the rate, magnitude, and persistence of response trajectories between girdling (emulating mortality from insect outbreak) and timber harvest treatments. Girdling and logging were equally likely to lead to large changes in forest structure and dynamics, but logging resulted in faster rates of change. Understory light increases and community composition changes were larger and more rapid in the logged plots. Tree seedling and understory vegetation abundance increased more in the girdled plots; this likely occurred because seedlings grew rapidly into the sapling‐ and tree‐size classes after logging and quickly shaded out plants on the forest floor. Downed deadwood pools increased more after logging but standing deadwood pools increased dramatically after girdling. Understory light levels remained elevated for a longer time after girdling. Perhaps because the window of opportunity for understory species to establish was longer in the girdled plots, total species richness increased more in the girdled than logged plots. Despite the potential for greater diversity in the girdled plots, Betula lenta L. (black birch) was the most abundant tree species recruited into the sapling‐ and tree‐size classes in both the girdled and logged plots and is poised to dominate the new forest canopy. The largest difference between the girdling and logging treatments—deadwood structure and quantity—will persist and continue to bolster aboveground carbon storage and structural and habitat diversity in the girdled plots. Human responses to insect outbreaks hasten forest reorganization and remove structural resources that may further alter forest response to ongoing climate stress and future disturbances. [ABSTRACT FROM AUTHOR]

Mean fire interval (MFI) is the average time between successive fires, influenced by environmental factors such as latitude, elevation, and vegetation type. This study evaluated the relationship between MFI and latitude in conifer forests of western North America. First, we obtained pre-fire-disruption MFI data from dendrochronology-based fire history studies in western Canada, the United States, and Mexico montane ranges. Then, we used generalized additive models (GAMs) to evaluate the relationship between MFI and latitude, considering elevation and conifer forest type as covariables. In addition, we mapped the spatial mean fire intervals (SMFIs) through inverse distance weighting (IDW). MFI increased significantly at higher latitudes, influenced by elevation and conifer forest type (R2 = 0.7). Furthermore, we found longer MFI in high elevations of the Madrean Archipelago, the Rocky Mountains, and the Alaska Range. Fire frequency also decreased in the boreal, Douglas-fir, and subalpine forests, with MFI longer than 20 yr. Moreover, the shortest SMFIs were found in the Mexican sierras and the Madrean Archipelago, with fire intervals between 4.1 and 5.6 yr. Our results showed a latitudinal gradient of MFI in conifer forests of western North America, which provides valuable information for fire management and the restoration of natural fire regimes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Despite widespread concerns about the anthropogenic drivers of global pollinator declines, little information is available about the impacts of land management practices on wild bees outside of agricultural systems, including in forests managed intensively for wood production. We assessed changes in wild bee communities with time since harvest in 60 intensively managed Douglas‐fir (Pseudotsuga menziesii) stands across a gradient in stand ages spanning a typical harvest rotation. We measured bee abundance, species richness, and alpha and beta diversity, as well as habitat characteristics (i.e., floral resources, nesting substrates, understory vegetation, and early seral forest in the surrounding landscape) during the spring and summer of 2018 and 2019. We found that bee abundance and species richness declined rapidly with stand age, decreasing by 61% and 48%, respectively, for every 5 years since timber harvest. Asymptotic estimates of Shannon and Simpson diversity were highest in stands 6–10 years post‐harvest and lowest after the forest canopy had closed, ~11 years post‐harvest. Bee communities in older stands were nested subsets of bee communities found in younger stands, indicating that changes were due to species loss rather than turnover as the stands aged. Bee abundance—but not species richness—was positively associated with floral resource density, and neither metric was associated with floral richness. The amount of early seral forest in the surrounding landscape seemed to enhance bee species richness in older, closed‐canopy stands, but otherwise had little effect. Changes in the relative abundance of bee species did not relate to bee functional characteristics such as sociality, diet breadth, or nesting substrate. Our study demonstrates that Douglas‐fir plantations develop diverse communities of wild bees shortly after harvest, but those communities erode rapidly over time as forest canopies close. Therefore, stand‐scale management activities that prolong the precanopy closure period and enhance floral resources during the initial stage of stand regeneration will provide the greatest opportunity to enhance bee diversity in landscapes dominated by intensively managed conifer forests. [ABSTRACT FROM AUTHOR]

Frequent‐fire forests were once heterogeneous at multiple spatial scales, which contributed to their resilience to severe fire. While many studies have characterized historical spatial patterns in frequent‐fire forests, fewer studies have investigated their temporal dynamics. We investigated the influences of fire and climate on the timing of conifer recruitment in old‐growth Jeffrey pine‐mixed conifer forests in the Sierra San Pedro Martir (SSPM) and the eastern slope of the Sierra Nevada. Additionally, we evaluated the impacts of fire exclusion and recent climate change on recruitment levels using statistical models with realized as well as fire suppression and climate change‐free counterfactual scenarios. Excessive soil drying from anthropogenic climate change resulted in diminished recruitment in the SSPM but not in the Sierra Nevada. Longer fire‐free intervals attributable to fire suppression and exclusion resulted in greater rates of recruitment across all sites but was particularly pronounced in the Sierra Nevada, where suppression began >100 years ago and recruitment was 28 times higher than the historical fire return interval scenario. This demonstrates the profound impact of fire's removal on tree recruitment in Sierra Nevada forests even in the context of recent climate change. Tree recruitment at the SSPM coincided with the early‐20th‐century North American pluvial, as well as a fire‐quiescent period in the late 18th and early 19th centuries. Episodic recruitment occurred in the SSPM with no "average" recruitment over the last three centuries. We found that temporal heterogeneity, in conjunction with spatial heterogeneity, are critical components of frequent‐fire‐adapted forests. Episodic recruitment could be a desirable characteristic of frequent‐fire‐adapted forests, and this might be more amenable to climate change impacts that forecast more variable precipitation patterns in the future. One key to this outcome would be for frequent fire to continue to shape these forests versus continued emphasis on fire suppression in California. [ABSTRACT FROM AUTHOR]

Trophic rewilding aims to promote biodiverse self‐sustaining ecosystems through the restoration of ecologically important taxa and the trophic interactions and cascades they propagate. How rewilding effects manifest across broad temporal scales will determine ecosystem states; however, our understanding of post‐rewilding dynamics across longer time periods is limited. Here we show that the restoration of a megaherbivore, the African savannah elephant (Loxodonta africana), promotes landscape openness (i.e., various measures of vegetation composition/complexity) and modifies fauna habitat and that these effects continue to manifest up to 92 years after reintroduction. We conducted a space‐for‐time floristic survey and assessment of 17 habitat attributes (e.g., floristic diversity and cover, ground wood, tree hollows) across five comparable nature reserves in South African savannah, where elephants were reintroduced between 1927 and 2003, finding that elephant reintroduction time was positively correlated with landscape openness and some habitat attributes (e.g., large‐sized tree hollows) but negatively associated with others (e.g., large‐sized coarse woody debris). We then indexed elephant site occurrence between 2006 and 2018 using telemetry data and found positive associations between site occurrence and woody plant densities. Taken alongside the longer‐term space‐for‐time survey, this suggests that elephants are attracted to dense vegetation in the short term and that this behavior increases landscape openness in the long term. Our results suggest that trophic rewilding with elephants helps promote a semi‐open ecosystem structure of high importance for African biodiversity. More generally, our results suggest that megafauna restoration represents a promising tool to curb Earth's recent ecological losses and highlights the importance of considering long‐term ecological responses when designing and managing rewilding projects. [ABSTRACT FROM AUTHOR]

A key uncertainty of empirical models of post‐fire tree mortality is understanding the drivers of elevated post‐fire mortality several years following fire, known as delayed mortality. Delayed mortality can represent a substantial fraction of mortality, particularly for large trees that are a conservation focus in western US coniferous forests. Current post‐fire tree mortality models have undergone limited evaluation of how injury level and time since fire interact to influence model accuracy and predictor variable importance. Less severe injuries potentially serve as an indicator for vulnerability to additional stressors such as bark beetle attack or moisture stress. We used a collection of 164,293 individual tree records to examine post‐fire tree mortality in eight western USA conifers: Abies concolor, Abies grandis, Calocedrus decurrens, Larix occidentalis, Pinus contorta, Pinus lambertiana, Pinus ponderosa, and Pseudotsuga menziesii. We evaluated the importance of fire injury predictors on discriminating between surviving trees versus immediate and delayed post‐fire mortality. We fit balanced random forest models for each species using cumulative tree mortality from 1 to 5‐years post‐fire. We compared these results to multi‐class random forest models using first‐year mortality, 2–5‐year mortality, and survival 5‐years post‐fire as a response variable. Crown volume scorched, diameter at breast height, and relative bark char height, were used as predictor variables. The cumulative mortality models all predicted trees that died within 1‐year of fire with high accuracy but failed to predict 2–5‐year mortality. The multi‐class models were an improvement but had lower accuracy for predicting 2–5‐year mortality. Multi‐class model accuracies ranged from 85% to 95% across all species for predicting 1‐year post‐fire mortality, 42%–71% for predicting 2–5‐year mortality, and 64%–85% for predicting trees that lived past 5‐years. Our study highlights the differences in tree species tolerance to fire injury and suggests that including second‐order predictors such as beetle attack or climatic water stress before and after fire will be critical to improve accuracy and better understand the mechanisms and patterns of fire‐caused tree death. Random forest models have potential for management applications such as post‐fire harvesting and simulating future stand dynamics. [ABSTRACT FROM AUTHOR]

We investigated the use of nesting resources in a landbird community in the arid zone near Peery Lake, northwestern New South Wales. Over a 3.5-year period (1990-1994), which encompassed pre-drought, drought and post-drought conditions, we recorded 504 active nests and 51 breeding species, including open-(45% of all breeding species), hollow-(27%), mud-(8%), ground-(8%) and tunnel-nesters (4%), and species that nested both in the open and in hollows (8%). Almost 90% of observed nests were located in run-on habitats - major creeklines and minor creeklines. Forty-two species nested in, and 24 species nested only in, run-on habitats. Only 23 species nested in the much more extensive surrounding run-off habitats, but the nests of six species were located only in run-off areas. Most nests (90%) were located in plants, all of which were perennials, with 408 nests in live plants and 47 nests in dead plants. The live plants included 20 tree and shrub species =0.5 m tall and 4 subshrub and grass species <0.5 m tall. Most (88%) nests in perennial plants were in trees >4 m tall but often low down in the tree (only 47% of all nests in perennial plants were at heights >4 m). Different bird species favoured different plant species. Favoured trees included River Red Gum Eucalyptus camaldulensis for hollow-nesters, and Whitewood Atalaya hemiglauca and Black Box Eucalyptus largiflorens for open- and mud-nesters. Though fewer nests were located in plants <4 m tall, they were in a wider variety of plant species (16 species) than the larger number of nests in plants >4 m tall (14 plant species). Some nomadic species nested in low vegetation which, though perennial, died back and was unavailable in dry times. To support the nesting requirements of all birds, and to retain the diversity of arid-zone birds, the floristic and structural diversity of perennial plants needs to be maintained. This will be difficult to achieve if the current pattern of ongoing, incremental loss of trees and shrubs continues in the arid zone, particularly as the rate of loss is likely to be exacerbated by the impacts of climate change. [ABSTRACT FROM AUTHOR]

Decline in the amount of dead wood deteriorates habitats for saproxylic organisms globally. This could be compensated by restoration, but it is poorly understood how created dead wood corresponds to the habitat requirements of saproxylic species. Using a large-scale field experiment of 30 restoration sites across Finland, we studied the long-term (5–15 years) effects of dead wood creation on wood-decomposing fungi (polypores) in Norway spruce and Scots pine dominated forests. All studied conservation areas had been used for timber production prior to conservation. The average amount and diversity of woody debris was higher on the restoration treatments than on the non-restored controls. Altogether, 56 polypore species were recorded. Restoration treatments had 1.4 and 8 times more species and observations than controls. Eight red-listed polypore species were observed, six on the restored plots (four only from the created dead wood) and two on the controls. Species composition of polypore assemblages differed between the restoration and control treatments, as well as between the spruce- and pine-dominated forests. Following restoration, temporal changes in the polypore assemblages were clear but only partly related to dead wood creation. Unlike previous short-term studies, our results show that dead wood creation by felling and ring-barking trees benefits not only common but also indicator and red-listed polypore species; indeed, 15 years after restoration all red-listed species occurred on created dead wood. As some red-listed species occurred solely on naturally fallen trees five to ten years after restoration, created dead wood alone cannot substitute for natural dead wood. • Large-scale and long-term field experiment reveals restoration benefits for polypores. • Dead wood creation increases abundance of common and red-listed polypores. • Dead wood creation changes polypore community composition. • Felling and ring barking trees is an ecologically sound restoration measure. [ABSTRACT FROM AUTHOR]

The history of forestry in Fennoscandia spans five centuries, with clear-cutting being the dominant practice since the mid-20th century. This has led to a significant transformation of the forest landscape. In this study we investigated long-term effects of clear-cutting on forest structure and dead wood volumes. We established twelve pairs of spruce forest sites in southeastern Norway, each pair constituting of a mature, previously clear-cut stand and its near-natural counterpart with similar edaphic factors. The near-natural stands had 2.8 times higher volumes of dead wood and a larger proportion of dead wood in late stages of decay. The near-natural stands had on average 36.8 ± 9.1 m3 ha−1 of downed dead wood and 24.1 ± 6.2 m3 ha−1 of standing dead wood. Corresponding numbers for the previously clear-cut stands were 10.2 ± 2.8 m3 ha−1 and 11.9 ± 3.7 m3 ha−1. Forests with lower volumes of dead wood often also had lower connectivity of old spruce forests, which potentially have further negative effects on biodiversity. Furthermore, near-natural stands displayed greater tree size heterogeneity, resulting in a wider variation in light conditions. While no difference was observed in living tree volume, we found only weak evidence for higher basal area in the previously clear-cut stands, which had a higher stem density with more slender stems and shorter crowns. Our findings suggest that managed forests do not develop structures typical of near-natural forests before they become mature for logging. We stress the importance of a thorough site selection for studies of management effects, as forest management history may be confounded with productivity and other edaphic factors. Experimental designs like ours are vital for testing how differences in structure and deadwood volumes, driven by forest management, translate into variations in biodiversity, carbon sequestration and ecosystem functioning in future studies. [Display omitted] • Different forest management is rarely found at otherwise similar site conditions. • We have established 12 pairs of mature forests differing primarily in clear-cutting history. • Forest management changed structural heterogeneity and tree size. • Dead wood volume in never clear-cut forests were low relative to similar forests in the region. [ABSTRACT FROM AUTHOR]

Managing for structural complexity to enhance forest health and resiliency is increasingly incorporated in silvicultural treatments. High spatial variability in stands managed for structural complexity could obscure forest management effects on surface soils. Yet few studies have assessed how within-stand variation in forest structure and other local controls influence the effects of timber harvesting on surface soil organic matter dynamics over time. We used a stratified random sampling design to capture variation in stand age, legacy structure, soil type, and topography in a second-growth, oak-hardwood forest in the northeastern U.S. We compared surface soil carbon and nitrogen content and availability in 15 harvested stands managed to promote tree regeneration (n = 144 plots) and five unharvested controls (n = 48 plots). We also examined changes over time since harvest in just the harvested stands using a 25-year chronosequence. Timber harvesting strongly influenced surface soil carbon and nitrogen dynamics. The harvested stands had lower soil carbon and nitrogen, microbial biomass, and carbon mineralization but higher nitrogen mineralization. These differences were more pronounced in the drier soil type with higher organic matter content than in the more moist soil type. Across the 25-year chronosequence, elevation, soil type, and downed woody material density dictated the direction of changes in surface soil carbon and nitrogen over time. Soil carbon and nitrogen accrued over time at drier, higher elevation (∼300 m) sites and was positively associated with higher densities of fine woody material but declined at lower elevations (∼180 m). Proximity to legacy trees was associated with higher soil carbon and nitrogen concentrations and availability. Our findings underscore the importance of silvicultural practices that retain structural legacies in shaping surface soil carbon and nitrogen dynamics over time. Our results also highlight how accounting for spatial variation in local controls on soil carbon and nitrogen, such as topography, can improve detection of changes from forest management practices that increase spatial heterogeneity within stands, such as irregular shelterwood and seed tree regeneration methods. • We test the impacts of timber harvesting on surface soil carbon and nitrogen. • Potential impacts are often obscured by local controls, such as forest structure. • Timber harvests reduced surface soil carbon but legacy trees increased carbon. • Topography and downed wood were associated with altered trajectories over time. • Accounting for local variation within stands allows detection of harvest effects. [ABSTRACT FROM AUTHOR]

In the introduced range, the successful establishment of an invasive species may be influenced by positive plant-plant interactions. Pre-existing vegetation, particularly conspecific mature trees, can shape the availability and attributes of microsites, thus potentially creating favorable conditions for the establishment of conspecific seedlings through facilitation. Pines are widely introduced in the Southern Hemisphere primarily as forestry plantations; these pines can become invasive, causing detrimental effects on local ecosystems and economies. In the high-elevation grasslands of the Sierras de Córdoba , Central Argentina, pines have begun to invade the native grassland as a result of improper (or lack of) management of pine plantations. During early pine invasion in this semi-arid grassland, we aimed to quantify the influence of adult live pines and on congeneric pine seedling recruitment and survival. For this, 48,000 seeds of Pinus elliottii and P. taeda were sown in three consecutive field trials, under different tree status treatments: live pines, dead pines, and no pines (i.e., open grassland). Seed were sown with and without irrigation and seeded microsites were oriented to the north and south of the live and dead trees. We also considered the hillslope aspect where the sites were located. Our results show that pine seedling recruitment was 57 % higher under live pines compared to dead pines and no pines treatment, but only in the trials that were not irrigated. Microsites south of the live pine trees, more shaded from direct sunlight in the Southern hemisphere, presented 36 % more pine seed germination than those to the north. In terms of topography, hillslope aspects with lower solar incidence (wetter hillslopes) also showed higher pine seedling recruitment. Our results suggest that moisture availability is a dominant factor driving further invasion, and that adult pines may be facilitating the invasion process by creating moister microsites for germination and pine seedling establishment. Thus, the early removal of adult pines is important to consider in the management of pine invasions. They do not only serve as a source of propagules, but also positively affect the establishment of their congeneric seedlings. [Display omitted] • Recruitment of congeneric seedlings was greater in microsites under live pines. • Recruitment is greater in microsites found to the south of the live pines (more shade). • South-facing hillslopes (wetter) had greater number of microsites with pine seedlings. • Water availability is a main factor influencing pine seedling establishment in the mountain grassland. • Adult pine trees may facilitate seedling establishment by improving moisture availability. [ABSTRACT FROM AUTHOR]

Retention forestry has become increasingly popular in recent decades. Although retained trees have a high post-harvest mortality rate, little is known about the role of dead retention trees in the conservation of lichen and bryophyte species. In this study, species composition and richness of bryophytes and lichens on living trees, and snags and logs of dead retention trees was assessed in 20 young stands in Latvia. The goal was to compare how the species richness and composition differ between retention tree structure types (living trees, snags, and logs). The results showed that higher bryophyte and lichen species richness per tree was found on logs and snags compared to living trees. Species composition significantly differed between retention tree structure types. Snags and logs hosted a higher number of woodland key habitat species than living trees. Retention tree species had a significant effect on bryophyte species richness on living trees, while tree species and diameter at breast height were important for bryophyte diversity on snags, and stage of decay on logs. In contrast, the number of lichen species on snags and logs was affected only by retention tree species while none of these factors had a significant effect on lichen species on living trees. As a conclusion, the conservation of bryophyte and lichen diversity on retention trees needs to consider also their role as deadwood substrates after their death. • Bryophyte and lichen richness were compared on snags, logs and living retention trees. • Logs and snags had more bryophyte and lichen species than living retention trees. • More woodland key habitat species were on snags and logs compared to living trees. • Factors influencing species richness differ between living and dead retention trees. • Dead retention trees are valuable substrate for bryophyte and lichen conservation. [ABSTRACT FROM AUTHOR]

Most years in the period from 2018 to 2022 have been exceptionally dry in Central Europe. In Germany's forests, this long-lasting drought has caused unprecedented tree mortality. Systematic ground-based surveys, such as the annual Crown Condition Survey, provide information on the vitality status of the different tree species and their mortality rates. However, models are needed to be able to map the spatial patterns of mortality for each tree species based on cause-effect relationships derived from field observations. In this study, logistic regression models were used to identify the most important drivers of mortality for the most important tree species in Germany. For this purpose, the dead and surviving trees from the Crown Condition Survey were combined with a large set of potential predictor variables from the domains of climate, topography, soil, land cover and deposition. After feature selection, the models were evaluated using the area under the curve (AUC) statistic. Norway spruce (Picea abies ; AUC = 0.9) showed by far the greatest increase in mortality, with the country-wide average observed and predicted rates approaching almost 10% per year from 2020 to 2022, and much higher predicted rates at the regional level. Much of the spruce mortality was explained by the climatic water balance of the driest summer in previous years. The other main tree species also showed clear mortality responses to the drought conditions. However, in the case of European beech (Fagus sylvatica ; AUC = 0.94) and Pedunculate and Sessile oak (Quercus robur and petraea ; AUC = 0.88), the peaks in the time series of the country-wide mortality rates stayed below 1%. For these broadleaved species, mortality was more dependent on a range of site conditions, i.e., soil and topography. For Scots pine (Pinus sylvestris ; AUC = 0.76), for which the observed mortality rate peaked at 1.2% in 2020, the given drivers could explain mortality only to a lesser degree than for the other species. The regression models were used for spatial prediction to produce country-wide maps of species-specific mortality rates at annual temporal and 100-m spatial resolution, covering all years from 1998 to 2022. The maps visualize the spatial patterns of mortality over time. The regions in western and central Germany, which were most seriously affected by spruce dieback can clearly be identified. The models and maps presented can be used for risk assessment, forest planning, and tree species selection, providing decision support for forest practitioners. • Logistic regression models for predicting tree mortality. • Maps showing regions of high mortality in Germany for the years 1998–2022. • Drought from 2018 to 2022 impacted all main species, but to a varying degree. • High prediction accuracies for Norway spruce, European beech and oak species. • Importance rankings of the main environmental drivers of mortality. [ABSTRACT FROM AUTHOR]

Litterfall is a major pathway for transferring aboveground biomass to the forest floor and thus plays an important role in building forest soil carbon stocks. However, inter- and intra-annual variability of litterfall remains poorly documented, especially in North American temperate and boreal forests, due to the lack of recent long-term studies at high sampling frequencies. This potentially creates uncertainties in estimates of forest carbon budget models. The objectives of the present study were to 1) quantify the mean annual flux, interannual variability, and seasonality of litterfall in three sites (dominated respectively by sugar maple (Acer saccharum Marsh.), balsam fir (Abies balsamea (L.) Mill. 1768), and black spruce (Picea mariana (Mill.) B.S.P.)) in eastern Canada over a period of 22–32 years, 2) relate the litterfall amounts and temporal variations to the changes in the size of major organic matter pools in these ecosystems, and 3) compare our litterfall estimates with reference values used in national greenhouse gas inventories. Litterfall production decreased from the sugar maple to the balsam fir and black spruce sites, preponderantly due to species composition. Litterfall evolution was related to the aboveground biomass of live trees in both conifer sites; in contrast, in the broadleaf site, changes in forest composition and structure were apparently the main drivers. The litterfall seasonality varied between broadleaf and conifer sites and could be explained by a sigmoidal model. Substantial departures from the seasonality for some given years were likely due to important climatic anomalies. Forest floor biomass remained stable over time at all three sites despite the increase in litterfall at the balsam fir and sugar maple sites and rapid forest floor turnover at the latter site. Our analyses of litterfall suggest that reference values from the literature used for national greenhouse gas inventories underestimate annual litterfall and forest floor carbon stocks for temperate and boreal forests. [Display omitted] • Litterfall evolution was related to aboveground biomass only in conifer sites • Mean annual flux and seasonality of litterfall varied by forest type • Climatic anomalies altered annual litterfall production and seasonality • Carbon budget model underestimated carbon stock of litterfall and forest floor [ABSTRACT FROM AUTHOR]

Tree mortality events across the globe have been associated with rising temperatures and altered disturbance regimes. Using fire scars, stand age structure, and tree-ring data, we evaluate changes in fire regimes, stand conditions, and climate to identify causes of mortality of a keystone species, whitebark pine, (WBP, Pinus albicaulis Engelm.) in a mixed subalpine forest in the Soldier Mountains, Idaho, at the lower elevation, low precipitation end, or trailing edge, of its range. Historically, the mean fire return interval was 66 years (±SD 34.1) until the late 19th century. Most fires were small, patchy, and of low to moderate severity consistent with grassy surface fuels. Climate synchronized fire disturbance, and larger fires burned across lower elevations and into WBP subalpine forests during very dry years. This occurred last in 1889 during a multi-year drought with fires documented across northwestern US. In the decades following, WBP establishment peaked and then declined, while subalpine fir (Abies labsiocarpa (Hook.) Nutt.) establishment peaked thirty years later and is ongoing. During global change-type or megadrought in the 2000s, WBP deaths per decade were 28-fold higher than the average since the early 20th century. Annual WBP mortality was positively associated with maximum summer temperature and negatively with summer precipitation. Ten years prior to the period of high WBP mortality, WBP annual radial growth fell below average and drought stress may have increased susceptibility to mountain pine beetle (Dendroctonus ponderosae Hopkins). Most dead WBP (90 %) showed signs of beetle attack. WBP mortality increased with fir basal area suggesting cumulative competition with subalpine fir likely contributed to mortality. Subalpine fir regeneration is three-fold more abundant than WBP and increased in areas with greater WBP mortality. We found a late 19th century drought concluded with a fire and subsequent WBP regeneration, whereas a 21st century fire-free megadrought accelerated WBP mortality and a forest shift towards subalpine fir dominance. Restoration using fire or thinning is imperative in trailing edge WBP forest given predictions of more frequent global-change-type megadrought. • Recent whitebark pine (WBP) mortality accelerated succession towards subalpine fir • Fire was a recurring disturbance in edge WBP forest over 5 centuries, until 1889 • Fire favored WBP regeneration and fire exclusion favors subalpine fir • In dry years, fires in lower elevations burned into WBP forests • During a 21st century long hot drought, WBP growth declined, and beetle kill spiked [ABSTRACT FROM AUTHOR]

In plantations, nutrient extraction is likely to be higher with shorter rotations. This is because thinner stems have a higher proportion of nutrient-rich bark, and sapwood contains more nutrients than hardwood. Annual willow plantations may extract even more nutrients than long rotation forests. In short rotation forest systems, the diameter of the harvested stems may affect the amount of nutrients exported with the wood. The present study investigated the effect of stem diameter distribution on nutrient extraction and nutrient use efficiency (UE). Two Salix clones were planted at low or high densities, and irrigated or left rainfed. Stems were harvested annually, and three years after planting, N, P, K, and Ca concentrations in small, medium, and big stems were determined, as well as the proportion of each stem diameter class at harvest. N extraction was the highest, followed by Ca, K, and P extraction. Nutrient extraction and nitrogen use efficiency were influenced by the proportion of small, medium, and big stems. The clones showed differences in nutrient concentration and stem diameter distribution, and irrigation increased the proportion of large stems and nitrogen concentration. Although the NUE and PUE were not linearly related to yield, they were related to the distribution of stem diameter and nutrient concentration. Higher yield resulted in higher CaUE and KUE, but the extraction of these nutrients during harvest was fine-tuned by stem diameter distribution and tissue concentration. This highlights the significance of stem diameter distribution in assessing the nutrient costs of wood production for bioenergy. [Display omitted] • In annual willow coppice nutrient extraction is N>Ca>K>P. • Nutrient extraction is related to the proportion of small, medium and large stems. • Clones differ in stem diameter distribution and nutrient concentration. • Irrigation increases the proportion and N concentration of large stems. • It is possible to increase nutrient use efficiency through silvicultural practices. [ABSTRACT FROM AUTHOR]

Long-term research and monitoring programs can provide important insights into biodiversity patterns to inform sustainable management of multi-use forest ecosystems. This study investigated biodiversity patterns in two forest ecosystems in the southwest region of Australia, as part of a long-term monitoring program, Forestcheck , established to track changes and trends in forest biodiversity associated with management activities. We assessed the effects of forest ecosystem, silvicultural treatment types (gap release and shelterwood/selective harvesting) and time since fire, on taxonomic richness and assemblage patterns across six taxonomic groups (terrestrial vertebrates, birds, macro-invertebrates, vascular plants, macro-fungi and cryptogams). Further, temporal comparisons in taxonomic richness and assemblage were completed for vascular plants and terrestrial vertebrates using data collected in a second round of monitoring. There was a low-level effect of harvesting and prescribed burning disturbance on combined community assemblage, but forest ecosystem had a greater influence on biodiversity patterns. Plant assemblages changed significantly according to ecosystem, silvicultural treatment type and monitoring round when two rounds of monitoring data were considered. These findings support previous assessments of Forestcheck sites, in that the strongest determinant of biodiversity patterns was forest ecosystem, and the greatest effects of disturbance were on assemblage patterns. These results provide some insight into post disturbance patterns and may assist with decision-making in relation to silviculture and prescribed burning regimes, and post-silviculture management, to provide increased opportunity for restoration of diversity. • Biodiversity patterns for six taxonomic groups were examined in response to silviculture and prescribed burning. • Data were across 16 sites in two jarrah (Eucalyptus marginata) forest ecosystems in the southwest of Western Australia. • Jarrah forest ecosystem had the greatest influence on biodiversity patterns. • General disturbance from harvesting and fire affected combined taxonomic assemblages. • Harvesting and fire disturbance affected individual groups only when considering multiple survey rounds. [ABSTRACT FROM AUTHOR]

Widespread afforestation is a crucial component of climate mitigation strategies worldwide. This presents a significant opportunity for biodiversity conservation if forests are appropriately managed. Within forests, structural and habitat diversity are known to be critical for biodiversity but pragmatic management recommendations are lacking. We make a comprehensive assessment of the effects of habitat variables on bird populations using data from over 4000 ha of forested landscape. We combine high‐resolution remote sensing data with comprehensive management databases to classify habitat attributes and measure the response of six taxonomic and functional diversity metrics: species richness, Shannon diversity, functional richness, functional evenness, functional divergence, and functional dispersion. We use a novel approach that combines hierarchical partitioning analysis with linear models to determine the relative importance of different habitat variables for each bird diversity metric. The age class of forest stands was consistently the most important variable across all bird diversity metrics, outperforming other structural measures such as horizontal and vertical heterogeneity and canopy density. Shrub density and gap fraction were each significantly associated with one bird diversity metric. In contrast, variables describing within‐stand structural heterogeneity (vertical and horizontal) were generally less important while tree species identity (e.g., conifer or broadleaved) was not significant for any bird diversity metric. Each of the six bird diversity metrics had different patterns of independent variable importance and significance, emphasizing the need to consider multiple diversity metrics in biodiversity assessments. Similarly, the optimal resolution for remote sensing metrics varied between structural variables and bird diversity metrics, suggesting that the use of remote sensing data in biodiversity studies could be greatly improved by first exploring different resolutions and data aggregations. Based on the results from this comprehensive study, we recommend that managers focus on creating habitat diversity at the between‐, rather than exclusively within‐stand scale, such as by creating a matrix of different age classes, to maximize bird diversity. This recommendation for forest managers is powerful yet pragmatic in its simplicity. [ABSTRACT FROM AUTHOR]

Estimating tree leaf biomass can be challenging in applications where predictions for multiple tree species is required. This is especially evident where there is limited or no data available for some of the species of interest. Here we use an extensive national database of observations (61 species, 3628 trees) and formulate models of varying complexity, ranging from a simple model with diameter at breast height (DBH) as the only predictor to more complex models with up to 8 predictors (DBH, leaf longevity, live crown ratio, wood specific gravity, shade tolerance, mean annual temperature, and mean annual precipitation), to estimate tree leaf biomass for any species across the continental United States. The most complex with all eight predictors was the best and explained 74%–86% of the variation in leaf mass. Consideration was given to the difficulty of measuring all of these predictor variables for model application, but many are easily obtained or already widely collected. Because most of the model variables are independent of species and key species‐level variables are available from published values, our results show that leaf biomass can be estimated for new species not included in the data used to fit the model. The latter assertion was evaluated using a novel "leave‐one‐species‐out" cross‐validation approach, which showed that our chosen model performs similarly for species used to calibrate the model, as well as those not used to develop it. The models exhibited a strong bias toward overestimation for a relatively small subset of the trees. Despite these limitations, the models presented here can provide leaf biomass estimates for multiple species over large spatial scales and can be applied to new species or species with limited leaf biomass data available. [ABSTRACT FROM AUTHOR]

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In Europe, forest management has controlled forest dynamics to sustain commodity production over multiple centuries. Yet over‐regulation for growth and yield diminishes resilience to environmental stress as well as threatens biodiversity, leading to increasing forest susceptibility to an array of disturbances. These trends have stimulated interest in alternative management systems, including natural dynamics silviculture (NDS). NDS aims to emulate natural disturbance dynamics at stand and landscape scales through silvicultural manipulations of forest structure and landscape patterns. We adapted a "Comparability Index" (CI) to assess convergence/divergence between natural disturbances and forest management effects. We extended the original CI concept based on disturbance size and frequency by adding the residual structure of canopy trees after a disturbance as a third dimension. We populated the model by compiling data on natural disturbance dynamics and management from 13 countries in Europe, covering four major forest types (i.e., spruce, beech, oak, and pine‐dominated forests). We found that natural disturbances are highly variable in size, frequency, and residual structure, but European forest management fails to encompass this complexity. Silviculture in Europe is skewed toward even‐aged systems, used predominately (72.9% of management) across the countries assessed. The residual structure proved crucial in the comparison of natural disturbances and silvicultural systems. CI indicated the highest congruence between uneven‐aged silvicultural systems and key natural disturbance attributes. Even so, uneven‐aged practices emulated only a portion of the complexity associated with natural disturbance effects. The remaining silvicultural systems perform poorly in terms of retention compared to tree survivorship after natural disturbances. We suggest that NDS can enrich Europe's portfolio of management systems, for example where wood production is not the primary objective. NDS is especially relevant to forests managed for habitat quality, risk reduction, and a variety of ecosystem services. We suggest a holistic approach integrating NDS with more conventional practices. [ABSTRACT FROM AUTHOR]

• Forest experiences are shaped by the environment, activities and personal resources. • Fires create potent environments through changes to enclosure, colour, dead trees. • Main types of experience in burnt forests are aesthetic, restorative and loss/recovery. • Connection to nature draws attention to loss/recovery, leading to sadness and hope. • Thought-based adaptions to fire include belief forests are dynamic and a fire aesthetic. Natural environments are changing with shifts in fire regimes. A little-understood impact is change to the interactions people have with forests. Generally, forests invoke positive feelings, but wildfire changes both forests and people's experiences of them. These were investigated with attention to the ever-changing physical characteristics of fire-adapted forests. In a mixed method approach, interviews were used to explore the subjective experiences of 57 adults in forests at different times since fire. A photo-based survey with 529 responses enabled further analysis of forest characteristics in experience. The Human-Environment Interaction (HEI) model guided analysis of experience events on four factors which shape them: the physical environment, activities undertaken, personal resources and social support. We found that bushfires create potent environments by changing the sense of enclosure, colours and dead trees in forests. Different levels of environmental potency combine with activities and personal resources to invoke different types of experience, the main ones being aesthetic (feelings of pleasure) restorative (relaxation) and loss/recovery (sadness mixed with hope). Personal resources are particularly important in the loss/recovery type. People who are connected to nature (one such resource), feel the loss of forest elements, but also notice forest recovery, which inspires hope. As fire frequency increases with climate change, experiences can be expected to become more negative overall. However, thought-based adaptations may be occurring in the spread of beliefs that forests are inherently dynamic and in the emergence of a fire aesthetic. Forest managers can assist people to come to terms with wildfires by providing access to forests postfire and by engagement to encourage adaptation. [ABSTRACT FROM AUTHOR]

An upsurge of invasive forest pathogens (IFPs) has been causing widespread damage to forest ecosystems worldwide. Modelling future forest loss caused by IFPs is challenging, as it requires a sophisticated understanding of the pathogen-hosts-surrounding interactions. We developed a complexity-appropriate model using an evidence-based approach to predict the decline of the European ash (Fraxinus excelsior L.) population caused by ash dieback (Hymenoscyphus fraxineus) in a British deciduous woodland. Our model predicts that (1) the ash population will decline by ∼26 % in the next 10 year; (2) an ±10 % relative error in mortality survey would cause a ∼8 % bias in 10-year population decline; and (3) a 5 % increase in resistant trees would save ∼3 % population over 10 years. Our research demonstrates the merit of systematic reviews in balancing model complexity against generalisation. By scaling up the methodology to other IFPs, it is possible to forecast forest health with various management scenarios. • A complexity-appropriate model was developed to forecast an invasive forest disease • If 15 % of trees are resistant they create an efficient buffer against population decline • Our modelling framework helps prediction, error assessment, and scenario building [ABSTRACT FROM AUTHOR]

Tropical montane forests are diverse ecosystems often affected by uncontrolled human-induced fires causing tree mortality and creating large deforested areas. After fires, Pteridium spp. ferns (bracken) often dominate, and forest regeneration in these areas is slow. In this study, we evaluated the effects of bracken fronds and litter, as well as the micro-environmental conditions created by the fern, on the density and species diversity of naturally recruiting seedlings. At eight sites, 120 experimental plots were established among forest and bracken-dominated areas with the following treatments: (a) fronds and litter intact (F+L+); (b) fronds intact and litter removed (F+L-); (c) fronds removed and litter intact (F-L+); and (d) fronds and litter removed (F-L-). After one year, all seedlings were registered, identified and classified according to their life-form (tree, shrub, herb, vine), dispersal vector (wind- or animal-dispersed) and successional status (early-, mid-, and late-successional). For all treatments we assessed 12 micro-environmental variables. We identified 3649 naturally-recruiting seedlings corresponding to 278 species from 70 families. We found positive effects of bracken fronds particularly on tree seedling recruitment: treatments with fronds had greater densities of both animal- and wind-dispersed tree seedlings, 1.8 and 1.4 fold higher, respectively, compared to treatments without fronds. Similarly, the density of early-, mid- and late-successional tree species was 1.3, 1.7 and 1.9 times higher in treatments with than without fronds. Furthermore, species diversity of early-, mid- and late-successional tree species was higher in the treatments with fronds. The environmental conditions generated by bracken presence, such as photosynthetically active radiation, soil temperature, live bracken biomass and litter depth, had positive effects on seedling density of all, animal-dispersed and early-successional tree species, and negative effects on seedling recruitment of other life-forms, notably from early successional stages. To promote forest regeneration in bracken-dominated areas, active restoration measures such as direct seed addition and transplants of nursery-raised seedlings of mid- and late-successional species should be considered. Since bracken can hinder the establishment of some life forms and species but favor others, it is recommended to include a trait-based approach to understand species responses to environmental factors and select species that are optimally adapted to bracken-dominated habitat conditions to promote forest regeneration. [Display omitted] • Bracken facilitates seedling recruitment of mid- and late-successional tree species. • Bracken fronds' shade increases species diversity of tree seedlings. • Bracken litter decreases natural recruitment of herbs. • Animal-dispersed species have higher recruitment under bracken fronds and litter. [ABSTRACT FROM AUTHOR]

Forests provide critical habitats for pollinating insects, including forest-dependent and habitat generalist species, yet it is unknown how these assemblages are shaped by overstory tree composition. We sampled bees in closed canopy plots in the southeastern United States representing a continuum of forest age and tree composition, from younger conifer-dominated forests to older forests dominated by deciduous broadleaf trees. Species-specific responses of bees to forest composition, and the influence of their traits on responses, were estimated using a joint species distribution model. Additionally, we investigated species richness trends of nesting, sociality, and phenological trait groups. Forest composition greatly influenced bee species occurrence: 48 % of species had positive relationships with the diversity of insect-pollinated broadleaf trees and 46 % had negative relationships with the proportion of conifer basal area. Bee species with early phenological activity drove these responses and richness patterns supported these trends. Our results indicate that phenology is an important factor determining bee species' forest dependency and sensitivity to forest composition in this region. We conclude that diverse broadleaf forests are crucial to maintaining bee diversity by providing floral resources that support forest-dependent species even in closed canopy conditions. Conifer forests can also provide valuable habitat to bee pollinators when restored to open canopy conditions. However, because no traits are indicative of conifer forest dependency and bee species respond to understory flora rather than tree attributes, open conifer forests may more strongly favor habitat generalists than forest specialists. • 48 % of bee species had positive relationships with insect-pollinated tree diversity. • 46 % of bee species had negative relationships with the proportion of conifer trees. • Bees species responding to tree composition had early phenological activity. [ABSTRACT FROM AUTHOR]

In Fennoscandian forests, evidence on the effects of variable tree retention, prescribed burning and deadwood creation on deadwood quantity and quality is still scarce. We studied the effects of prescribed burning, tree retention and downed wood creation on the deadwood profile in managed boreal Norway spruce forest stands over a 16-year period. The stand scale treatments of the experiment included cuttings with a constant volume of dispersed retention trees (50 m3 ha-1, ca. 200 trees per ha), and three levels of downed deadwood creation (5, 30 and 60 m3 ha-1), in both upland and paludified biotopes of Myrtillus site type, with or without prescribed burning, with three replicates each. After 16 years since the treatments, the diverse deadwood profiles with varying distribution by decay class were formed. The volume of deadwood varied from 9 to 107 m3 ha-1 with a mean of 65 m3 ha-1. The index of deadwood diversity was positively influenced by prescribed burning and negatively influenced by deadwood creation. The volume of all deadwood and coarse woody debris (CWD), volume and number of logs, as well as dead to live volume ratio increased after prescribed burning and with the level of deadwood creation. The positive effect of deadwood creation on the total CWD volume was higher in the upland biotopes than in the paludified ones. The highest amounts of all deadwood, CWD and logs were recorded in the upland biotopes after prescribed burning without deadwood creation. Our findings highlight the impact of tree retention with prescribed burning and deadwood creation in diversifying deadwood profile and maintaining deadwood continuum for decades. [Display omitted] • Prescribed burning ensures continuity and diversity of deadwood in the long term. • The highest amounts of deadwood were found in burned stands without cuttings. • More highly decomposed wood was found after higher deadwood creation level. • The results can be applied in developing deadwood enrichment strategies. [ABSTRACT FROM AUTHOR]

Erannis jacobsoni Djak. (EJD), a typical pest of coniferous forests in Mongolia, has severely threatened forest areas in recent years owing to its rapid development and spread. EJD feeds on needles and leaves, killing many trees and causing severe damage to forest ecosystems，which results in substantial local economic losses. The rapid and effective monitoring of forest pests is crucial for preventing or controlling infestations in a timely manner. To this end, in this study, we calculated spectral vegetation indices using UAV multispectral data, assessed ground survey data to determine the degree of pest damage, and conducted sensitivity analysis on the spectral vegetation indices. Nine sensitive spectral vegetation indices were selected to analyze the intramonthly and intermonthly variations in the spectral vegetation indices of forests during EJD infestation: the chlorophyll red-edge parameter index (CIreg), corrected NIR/IR simple ratio (GMSR), intensity index (Int and Int2), improved NIR/red-edge simple ratio (MSRreg), normalized difference NIR vegetation index (NDSI), soil adjusted vegetation index (SAVI), and salinity index (SI2reg and SI3). The results demonstrated that the variance F values of the sensitive spectral vegetation indices after screening using the successive projection algorithm were highly significant at the α = 10 − 10 level, suggesting that these indices are highly sensitive to the level of pest damage. The intramonthly results were as follows: in June, CIreg, GMSR, Int, Int2, MSRreg, SAVI, SI2reg, and SI3 decreased with increasing pest damage, whereas NDSI increased; in August, the difference in index values between light, medium, and heavy damage and healthy stands was not significant; and in September, most of the index differences changed to mild > moderate > severe. Regarding the intermonthly results, the magnitude of the vegetation index values for each sensitive spectrum at different hazard levels was ranked as June > September > August, and the overall difference varied as δ 3 > δ 2 > δ 1. The spectral vegetation indices apparently responded to different levels of pest damage, making them suitable for quickly and accurately monitoring the occurrence and development of forest pests. These results provide a reference for the monitoring of forest pests at spatial and temporal scales. • SPA extracted nine spectral indices sensitive to EJD. • Analyzed intramonthly index changes across varying EJD damage levels. • Intermonthly index variations examined for varying EJD impacts. [ABSTRACT FROM AUTHOR]

The 2012–2016 California drought was the most severe in the state's recorded history, contributing to the death of millions of trees. Through sampling 54 (0.25 ha) plots in northern California and employing standard dendrochronological techniques this study compared tree mortality and regeneration patterns before, during, and after California's recent record-setting drought in both montane and costal environments. This study evaluated 1) the influence of habitat and competitive covariates on mortality and regeneration trends using ridge regression analysis; and 2) tree death and seedling/sapling establishment dates using dendrochronology and Superposed Epoch Analysis to explore the influence of climate on forest demographics. Results showed two trends related to climatic patterns in montane environments: (1) years with high rates of mortality were positively associated with climatic water deficit (CWD) in the 1–2 years preceding and during tree death dates; and (2) regeneration dates were significantly associated with below-average CWD in the preceding year. In montane sites, pre-drought mortality was greater at wet sites than dry sites, and drought-related mortality was positively related to canopy openness. In coastal environments, drought-related tree mortality was positively associated with maximum temperature and topographic position (e.g., greater on upper slope sites). Drought-related tree mortality occurred primarily in trees smaller than 40 cm diameter at breast height (DBH, 1.37 m) in montane forests, and exclusively in trees 80 cm DBH or smaller in coastal environments. Our findings also indicate that current demographic trends will likely reduce forest diversity in the future, especially in montane environments. For example, in montane environments mortality was greater in white pine species (Pinus lambertiana and P. monticola) than other species and regeneration was weighted towards advanced regeneration of shade-tolerant fir (Abies) species (median age of 34 years). These findings highlight the effects of fire exclusion, and the need for targeted management, including reducing tree density and returning fire process, aimed at decreasing drought related mortality, and increasing regeneration of shade-intolerant species (e.g., pines). Management should also preferentially retain medium to large trees, which demonstrated less vulnerability to mortality, to enhance the resilience and diversity of northern California forests. • Montane tree mortality was associated with high climatic water deficit (CWD). • Montane tree regeneration was associated with low CWD in the preceding year. • Drought-related mortality was more frequent in small trees than large trees. • Mortality was highest in Pinus ; regeneration was dominated by shade-tolerant taxa. [ABSTRACT FROM AUTHOR]

Ununiform, excessive, and prolonged understory vegetation feeding by overpopulated ungulates (over-browsing) leads to heterogeneous stand structural alterations at the landscape level. However, it is not yet clear how changes in various types of stand structural alterations affect total carbon (C) stocks in forest ecosystems as the sum of aboveground C stocks (AGC) and belowground C stocks (BGC). We aimed to fill this gap in a cool temperate broadleaf–conifer mixed forest in southern Kyushu, Japan, where over-browsing of sika deer has occurred since 1980. Four replicate survey plots were established in four stand types, namely, stands with presence of understory vegetation (PU), stands with no understory vegetation (NU), stands dominated by unpalatable shrubs (SR), and stands with canopy gap areas with a lack of regeneration (CG). Using PU as a baseline, alterations in stand structure (e.g., stem density) and C stocks were evaluated for each stand type. We measured C stocks of overstory trees (height > 2 m), understory vegetation, leaf litter, fine woody debris (FWD), and coarse woody debris (CWD) as AGC. C stocks of fine roots, coarse roots, and soil organic matter (SOM) at 0–30 cm depths were measured as BGC. We also separated overstory trees according to the palatability of the deer diet. The alteration from PU to NU did not reduce AGC, BGC, or total C stocks. The alteration from PU to SR and CG was found to potentially reduce total C stocks and AGC by up to 49% and 59%, respectively. These reductions in SR and CG were mainly driven by the decreased C stock of palatable overstory trees. There were dense unpalatable shrubs in SR and large amounts of CWD in CG. However, neither was sufficient to offset the loss of palatable overstory trees in SR and CG. We also found a reduction in the C stock of leaf litter and SOM at 0–10 cm depth in NU, SR, and CG. These reductions were likely caused by reduced litterfall and increased soil erosion, implying future reductions in BGC. Our results suggest that stand structure conservation is a key guideline for C stock retention when implementing forest management strategies to prevent over-browsing. The failure to conserve palatable juvenile trees could lead to a lack of more palatable overstory trees in the future, causing irreversible changes in AGC and BGC. [Display omitted] • We evaluated reductions in carbon stock from stand structural alterations by deer. • Total- and aboveground-carbon stocks reduced by up to 49% and 59%, respectively. • These reductions were mainly due to the inhibition of tree renewal after tree death. • Reduced tree and understory biomass subsequently reduced surface organic matters. • Unpalatable shrubs and coarse woody debris did not offset carbon stock reductions. [ABSTRACT FROM AUTHOR]

The Amazon basin strongly influences the global carbon cycle, storing billions of tonnes of carbon in a relatively small number of 'hyperdominant' tree species. However, the Amazon carbon stock is threatened by land-use change. In the remaining forest patches, trees close to the forest border bear various physical and biotic edge effects that alter plant growth and survival. To assess how edge effects influence tree mortality and carbon storage, we investigated the occurrence of hyperdominant tree species in the Brazilian Amazon between 1988 and 2021. Evaluating tree records from a network of permanent plots and herbarium collections, we found that 22 % of tree occurrence records were in deforested areas, 35% within 1 km of the forest edge, and 43 % in continuous forest. At the local scale in Central Amazonia, tree monitoring data over 30 years revealed that forest fragments hyperdominant trees had twice the mortality rate of continuous forest ones due to edge effects during the 15 years following edge establishment. Although trees in fragments had higher initial growth, this pattern declined over the years and eventually resulted in significant carbon loss, mainly from tree mortality. Edge effects have led to annual declines in the biomass of forest remnants, suggesting that hyperdominant species are also susceptible to disturbances that lead to degradation and forest losses. Conservation of the Amazon forests requires an approach that considers the effects of local disturbances on carbon stocks in the region. • In recent decades, deforestation has lost 22 % of historical records of hyperdominant tree species in the Brazilian Amazon. • 35 % of occurrence data are on forest edges, susceptible to the negative impacts caused by fragmentation and deforestation. • Hyperdominant populations in Central Amazon edges showed twice the mortality rate in the first 15 years after edge creation. • The unbalanced tree mortality directly affects the Carbon cycle, representing losses, even in forested areas. [ABSTRACT FROM AUTHOR]

Interactions between species influence ecosystem functions and are sensitive to reintroductions. Our understanding of interactions between naturally co-occurring large herbivores, such as Eurasian beaver (Castor fiber) that are now re-establishing throughout their range, and well-established native ungulates, is limited, despite the potential implications for riparian woodlands. Observations in Scotland indicate that roe deer (Capreolus capreolus) readily exploit the regenerative secondary shoots produced after tree felling by beaver. Our study, based in eastern Scotland, investigates the role of beaver herbivory in riparian woodland regeneration and asks whether deer are attracted to this novel resource because it is either a) more readily available, b) nutritionally superior, or c) morphologically more appealing than accessible browse on unfelled (standing) trees. We firstly quantified the secondary shoots available to browsing deer at different heights on felled and standing birch (Betula spp.) trees in twenty riparian woodland plots across five well-established beaver territories (occupancy ten years). Shoots from birch and willow (Salix spp.) trees with contrasting levels and combinations of beaver and deer browsing were then analysed for nutritional content (nitrogen and carbon) and morphological characteristics (number of buds and lateral branches). We found that 62% of beaver-felled trees produced secondary shoots available to browsing deer. Compared to standing trees, regenerating beaver-felled trees had 18% more secondary shoots. These shoots were significantly higher in nitrogen content (+13%), but similar in carbon content and concentrated closer to the ground. Our results show that beaver herbivory can promote riparian woodland regeneration and heterogeneity by creating a mosaic of mature and multi-stemmed coppiced trees. The addition of a common, readily available, and nutritious resource through beaver browsing could, however, also enhance habitat quality for browsing deer, with the potential to affect deer distribution and feeding habits. • Tree felling by beaver promotes riparian woodland regeneration. • Among beaver-felled trees 62 % produced secondary shoots accessible to deer. • Beaver-felled trees yielded more shoots (+18 %) that were richer in nitrogen (+13 %). • Tree felling by beaver could influence deer feeding and distribution. • Beaver-deer interactions have implications for riparian woodland conservation. [ABSTRACT FROM AUTHOR]

Ecological forestry experiments typicaly use large treatment units and silvicultural prescriptions that commonly increase within-unit heterogeneity in structural complexity and species composition in large treatment units. Increased heterogeneity influences processes affecting tree responses (e.g., competition) that operate at the neighborhood-level, posing challenges to analysis and interpretation. To investigate whether examining within-unit heterogeneity offers a more meaningful evaluation of project success than comparing categorical treatment effects, we used 20-year data from the Goosenest Adaptive Management Area (AMA) ecological forestry experiment in northern California, U.S. Designed to evaluate management alternatives for reducing fuels and accelerating development of late-seral forest characteristics in ponderosa pine (Pinus ponderosa)/white fir (Abies concolor) mixed-conifer forests, the Goosenest AMA study consists of (1) an untreated Control, (2) a Big Tree treatment using thinning from below to favor retention of large trees of any species, (3) a Pine Emphasis treatment combining thinning from below with radial thinning to favor percent ponderosa pine while increasing structural complexity, and (4) a Pine Emphasis with Fire treatment with added post-thinning prescribed burns. Our objectives were to evaluate 1) how treatments affect within-unit variation in neighborhood competition, structural complexity, and tree species composition, and 2) whether categorical treatment effects versus within-unit variation in competition, complexity, and composition influence individual-tree basal area increment (BAI), vigor as indicated by live crown ratio (ΔLCR), and tree mortality. To accomplish this, we developed and compared a series of generalized linear mixed models. Our analysis included the first investigation into whether fuel-reduction treatments alter tree species mixture-effects in ponderosa pine/white fir mixed-conifer forests. We found that all treatments similarly reduced neighborhood competition relative to the Control. The two Pine Emphasis treatments promoted greater variation in neighborhood competition and higher Percent pine relative to the Big Tree treatment, consistent with restoration objectives. Reduced neighborhood competition improved both ponderosa pine and white fir BAI. Reduced neighborhood competition helped to offset or reverse crown vigor decline in ponderosa pine and white fir, respectively. Species-mixture effects were negative for both small and large ponderosa pine BAI. For white-fir, trees grew faster in neighborhoods with a higher percentage of pine but the probability of mortality increased. Categorical treatment differences consistently reduced ponderosa pine and white fir mortality, except for the Pine Emphasis with Fire treatment, which increased white fir mortality. Our findings suggest that restoring historical ponderosa-pine forest reference conditions could accelerate the development of fire-resistant ponderosa pine tree sizes and sustain large pine growth. • Fuel reduction treatments foster fine-scale variation in structure and composition. • Local competition influences tree growth and vigor in California mixed-conifers. • Tree size and competition modify species mixture effects on growth. • Tree mortality varies with unit-level treatment and local species composition. • Restoration can benefit disturbance resistance and alter species-mixture effects. [ABSTRACT FROM AUTHOR]

Natural disturbances play an important role in shaping the dynamics of mountain forests, yet their effects on essential ecosystem services, such as protection against natural hazards, can be significant. With the challenges posed by climate change and increasing disturbances, as well as the complexities of salvage logging, there is a growing interest in understanding post-disturbance development in unsalvaged mountain forests, alongside the advancement of decision support systems aimed at ensuring sustained provision of ecosystem services. In this study, we combined a space-for-time substitution approach with long-term monitoring data to evaluate regeneration processes and development of deadwood decay following three distinct windthrow events in Central European mountain forests that were locally unsalvaged (specifically Vaia in 2018, Kyrill in 2007, and Vivian in 1990). Our unique dataset additionally provided insights into the long-term effects of disturbance legacies and tree regeneration on protection against natural hazards. Deadwood cover gradually decreased with time since disturbance, from an average of 50% two years after Vaia to 25% twelve years after Kyrill and 15% thirty years after Vivian. Similarly, deadwood height above ground significantly decreased over time, with median values dropping from 1 to 2 m immediately after the disturbance to 25–30 cm three decades later. The decay stage and diameter of deadwood significantly influenced tree regeneration, with larger diameters of logs and deadwood in more advanced decay stage (especially less solid/soft to very loose stage), facilitating seedling establishment, thus a second wave of tree regeneration. About a quarter of saplings grew on deadwood thirty years after disturbance. The analysis of post-windthrow stand development showed an increase in tree cover and height with time since disturbance, with distinct patterns observed across different windthrow events and sites. Three decades post-disturbance, the number of trees had notably increased, with tree cover reaching 50%. Although Norway spruce remained the dominant species, the forest composition had shifted towards a predominance of broadleaves, particularly evident at lower elevations and areas with moderate browsing pressure. Our findings underscore the critical role of post-disturbance forest recovery and deadwood dynamics in promoting uneven-aged mixed forest structures, thereby enhancing forest regeneration, structural diversity, and protection against natural hazards. Emphasizing the vital importance of retaining deadwood, our study suggests that its role as a valuable substrate for enhancing resilience and ecosystem services is likely to grow in the future. • Deadwood cover and height above ground decreased with time since windthrow. • Decay stage and diameter of deadwood significantly influenced tree regeneration. • At lower elevations, windthrow led to higher shares of broadleaves. • Deadwood supports tree establishment and heterogeneity of forest structure. • Avoiding salvage logging enhanced forest recovery and avalanche protection. [ABSTRACT FROM AUTHOR]

Biological invasions are one of the most relevant factors of biodiversity loss, especially after fire disturbances. Wildfires can accelerate invasions of fire-prone species, like Pinus radiata, and dramatically alter ecosystems. However, how to assess the main impacts of this invasion process on the composition, structure, and functionality of ecosystems, including the post-fire revegetation processes, has not been fully resolved. This study aimed to evaluate the impacts of P. radiata invasion on fire-damaged forest ecosystems using combined remote sensing and in situ data, focusing particularly on changes in biodiversity, ecosystem structure, and functionality. The recovery of forest leaf area index (LAI) and the fraction of photosynthetically active radiation (FPAR) were monitored using Sentinel-2 time series products. Then the pre- and post-fire native community composition and the relationships of invasion and biodiversity with biotic and abiotic components were characterized using structural equation modeling (SEM). The postfire P. radiata density was mapped to quantify invasion intensity in three burned native forest fragments using generalized additive modeling (GAM) regressions based on UAS multispectral data. Biophysical metrics indicate that all forest fragments impacted by high, medium-high, and medium-low severity fires achieved a partial recovery of their canopy. The SEM model showed that microtopographic features and vegetation height explain native species diversity under pre-fire conditions due to their close relationship with favorable microclimatic conditions for species establishment. Vegetation height determined the abundance of P. radiata in post-fire conditions, and it negatively impacted diversity by promoting the homogenization of vegetation cover and altering diversity patterns. The general composition and abundance metrics also showed a substantial modification associated with the heavy (significant) invasion of P. radiata species. Predictive mapping of P. radiata density showed high accuracies (R2 =0.73 and explained deviation of 80%). The maps depicted an intense concentration of the invasive tree with a mean density of 76,217 individuals per ha−1 and high invasion spots with more than 176,000 individuals per ha−1. The quantification of invasion and mapping is a fundamental input for prioritizing areas and resources for a large-scale restoration program, and is a priority to avoid the loss of these highly threatened forest ecosystems. • Multiscale remote sensing allows understanding post-fire pine invasion. • Post-fire pine invasion alters forest ecosystem attributes. • UAV data can be used to predict pine invasion in burned forests. [ABSTRACT FROM AUTHOR]

Contemporary fire regimes in Californian forests are shifting, with fires becoming larger, more frequent, and increasingly severe. As landscapes transition back to active fire regimes, understanding how the physical environment and biological legacies of past disturbance interact with and determine forest development becomes an increasingly important management concern. We surveyed post-fire regeneration in a wilderness area of Lassen Volcanic National Park (LAVO) with a three-decade history of fires. We tallied conifer seedlings , and measured shrub and ground cover and mature trees in the field, and used geospatial data and water balance models to account for the possible effects of , terrain, live seed sources, vegetation characteristics, and immediate post-fire climate as measured by water balance on conifer regeneration. We used a Random Forest machine learning technique to model how landscape and local factors affect post-fire regeneration stocking and species regeneration occurrence. Post-fire conifer regeneration in LAVO was common: Median post-fire seedling density was close to desired stocking density, 73% of our plots had at least one conifer seedling, and only 16% of plots lacked tree regeneration or mature trees. Likelihood of stocking and individual species' occurrence was most strongly related to time since fire, distance to forest, elevation, and species of nearest seed source. Tree regeneration increased with time since fire, but this effect was more pronounced at high elevation suggesting an interaction between terrain and time since fire on regeneration. Stocking was most likely on cooler (northeastern) slopes and at lower (<1950 m) elevations, nearer (within 200 m) to live forest patches, and where shrub cover was present but low (<20%). Climatic conditions as represented by water balance for the first five years after a fire did not influence likelihood of stocking but it did influence species occurrence. Distance to conspecific trees was important for species' regeneration occurrence, and the landscape pattern of species occurrence was consistent with the elevational zonation of forest dominants in LAVO. Adequate tree regeneration of forests with an active fire regime in LAVO indicate that California montane forests are resilient to prescribed fire and managed wildfire and that expanded use of fire to reduce potential for severe fire promotes resilience in California forest landscapes. • Regeneration was surveyed in conifer forests 7–25 years post-fire. • Half the plots were stocked and 27% had no regeneration. • Time since fire, distance to forest, and elevation controlled regeneration. • Post-fire water balance had no discernable effect on stocking. [ABSTRACT FROM AUTHOR]

The timber producing forest land-base in Alberta, Canada, is decreasing due to the increase in allocation of land to other uses such as agriculture, infrastructure, energy development and conservation areas, while the demand for forest products continues to increase. Tree improvement, first implemented in Alberta in 1975, is one strategy used for increasing forest productivity to meet an increasing demand for fibre and forest products. To quantify the operational impact of tree improvement on white spruce productivity, we collected data from 15-year-old white spruce stands in Alberta: 11 stands planted with seedlings from improved (seed orchard) seedlots and seven stands planted with seedlings from wild (unimproved) seedlots. Eight plots (100 m2 circular plots) within each stand were randomly established for measurement (18 × 8 = 144 plots). Diameter at breast height (DBH), tree height, crown width, and branch diameter for each tree inside the plots were measured. Mixed effects models, with site and plot considered random, were used to evaluate the effect of tree improvement on the growth of white spruce. Basal area per ha of competitor species was used to develop a non-spatial competition index, and to compare the growth of improved and unimproved white spruce response to competition. Individual trees from improved stands showed 17% greater DBH and height compared to individual trees from unimproved stands. Individual trees of improved stands also had a greater height and smaller branch diameter for a given DBH than the trees grown in unimproved stands. Overall, tree improvement increased the site index of white spruce by 2 m while both improved and unimproved stands were similarly, and negatively, affected by competition. The application of tree improvement in white spruce resulted in an increase in growth rate, site index, and quality of timber, which will help offset the increasing demand for forest products. • Impact of tree improvement on white spruce was assessed operationally. • 17% greater growth in DBH and height was observed in improved white spruce. • Site index of improved white spruce was increased by 2 m. • Improved and unimproved stands were similarly affected by competition. [ABSTRACT FROM AUTHOR]

In an emerging era of megadisturbance, bolstering forest resilience to wildfire, insects, and drought has become a central objective in many western forests. Climate has received considerable attention as a driver of these disturbances, but few studies have examined the complexities of climate–vegetation–disturbance interactions. Current strategies for creating resilient forests often rely on retrospective approaches, seeking to impart resilience by restoring historical conditions to contemporary landscapes, but historical conditions are becoming increasingly unattainable amidst modern bioclimatic conditions. What becomes an appropriate benchmark for resilience when we have novel forests, rapidly changing climate, and unprecedented disturbance regimes? We combined two longitudinal datasets—each representing some of the most comprehensive spatially explicit, annual tree mortality data in existence—in a post‐hoc factorial design to examine the nonlinear relationships between fire, climate, forest spatial structure, and bark beetles. We found that while prefire drought elevated mortality risk, advantageous local neighborhoods could offset these effects. Surprisingly, mortality risk (Pm) was higher in crowded local neighborhoods that burned in wet years (Pm = 42%) compared with sparse neighborhoods that burned during drought (Pm = 30%). Risk of beetle attack was also increased by drought, but lower conspecific crowding impeded the otherwise positive interaction between fire and beetle attack. Antecedent fire increased drought‐related mortality over short timespans (<7 years) but reduced mortality over longer intervals. These results clarify interacting disturbance dynamics and provide a mechanistic underpinning for forest restoration strategies. Importantly, they demonstrate the potential for managed fire and silvicultural strategies to offset climate effects and bolster resilience to fire, beetles, and drought. [ABSTRACT FROM AUTHOR]

Copyright of SHILAP Revista de Lepidopterologia is the property of Sociedad Hispano-Luso-Americana de Lepidopterologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Promoting ecological resilience to increasing disturbance activity is a key management priority under warming climate. Across the Northern Hemisphere, tree mortality from widespread bark beetle outbreaks raises concerns for how forest management can foster resilience to future outbreaks. Density reduction (i.e., thinning) treatments can increase vigor of remaining trees, but the longevity of treatment efficacy for reducing susceptibility to future disturbance remains a key knowledge gap. Using one of the longest‐running replicated experiments in old‐growth subalpine forests, we measured stand structure following a recent (early 2000s) severe mountain pine beetle (MPB; Dendroctonus ponderosae) outbreak to examine the legacy of historical (1940s) thinning treatments on two components of resilience. We asked: 'How did historical thinning intensity affect (1) tree‐scale survival probability and stand‐scale survival proportion (collectively "resistance" to outbreak) for susceptible trees (lodgepole pine [Pinus contorta] ≥ 12 cm diameter) and (2) post‐outbreak stand successional trajectories?' Overall outbreak severity was high (MPB killed 59% of susceptible individuals and 78% of susceptible basal area), and historical thinning had little effect on tree‐scale and stand‐scale resistance. Tree‐scale survival probability decreased sharply with increasing tree diameter and did not differ from the control (uncut stands) in the historical thinning treatments. Stand‐scale proportion of surviving susceptible trees and basal area did not differ from the control in historically thinned stands, except for treatments that removed nearly all susceptible trees, in which survival proportion approximately doubled. Despite limited effects on resistance to MPB outbreak, the legacy of historical treatments shifted dominance from large‐diameter to small‐diameter lodgepole pine by the time of outbreak, resulting in historically thinned stands with ~2× greater post‐outbreak live basal area than control stands. MPB‐driven mortality of large‐diameter lodgepole pine in control stands and density‐dependent mortality of small‐diameter trees in historically thinned stands led to convergence in post‐outbreak live tree stand structure. One exception was the heaviest historical thinning treatments (59–77% basal area removed), for which sapling dominance of shade‐tolerant, unsusceptible conifers was lower than control stands. After six decades, thinning treatments have had minimal effect on resistance to bark beetle outbreaks, but leave persistent legacies in shaping post‐outbreak successional trajectories. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cavities provide suitable microhabitats for various organisms. Therefore, cavity excavators are important species in forest environments. We observed large differences in both persistence and occupancy of the cavities of Grey-headed Woodpecker Picus canus monitored during the whole cavity lifespan in a 33-year study in southern Finland. Of a total of 80 cavities studied, the median persistence time was 17 years, but this varied from a median lifespan of 29 years for cavities in living trees to only 9 years for cavities in dead trees. The expected number of life-span nests of forest bird species per old cavity was 4.2 in living, and only 1.6 in dead trees. Ten bird species utilised the old cavities (most frequently Great Tit Parus major, Grey-headed Woodpecker and Pied Flycatcher Ficedula hypoleuca). The results show that both suitable living and dead trees should be available for cavity excavators such as the Grey-headed Woodpecker, and that living and dead trees may have different, but important ecological roles for cavity-nesting birds in boreal forests. [ABSTRACT FROM AUTHOR]