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• Long-term responses to commercial thinning (CT) in spruce-fir stands assessed. • Delaying CT in young spruce-fir stands did not enhance total yield and stand value. • Low and crown thinning enhanced average tree size and sawlog production. • Thinning from above had detrimental effects on tree size and total yield. • Similar cumulative volume after light crown or low thin and in unthinned stand. Pre-commercial (PCT) and commercial thinning (CT) are important silvicultural tools applied to spruce-fir (Picea - Abies) forests, a key forest type in the northeastern portion of North America. However, the long-term influences of CT, particularly when combined with PCT, are relatively unknown, except for a few specific locations in the region. Utilizing the repeated measurements from replicated experimental research sites (n = 15) initiated in the early 2000s throughout Maine, we quantified the influence of contrasting thinning treatments on spruce-fir stands with prior PCT and without a prior PCT (NoPCT). Thinning treatments at the nine sites with a prior PCT were a combination of multiple entry timings (immediate, 5-, and 10-year delay) and removal intensities (0, 33, and 50 % relative density reduction). At the six NoPCT sites, the CT treatments were a combination of thinning methods (dominant, crown, and low) and removal intensities (0, 33, and 50 %). The most effective CT in terms of large tree response, sawlog volume, and stand value were immediate CT rather than delayed treatments after PCT, and low thinning in NoPCT stands. Dominant thinning in NoPCT showed detrimental effects on residual stand conditions leading to the lowest yield and generated product values. In general, the earlier CT entry in PCT stands led to greater long-term benefits of the treatment in terms of tree size, merchantable volume, and financial value of the stand. No thinning treatment significantly enhanced cumulative total volume or merchantable volume or financial value compared to unthinned controls because even though thinning enhanced sawlog production, unthinned stands produced more pulpwood and studwood. Although we did not find significant economic benefits of CT in stands with or without PCT, light low thinning in NoPCT, and light crown thinning without delay in PCT could be an optimal strategy to maximize the average merchantable stem size without compromising the total stand value, while providing additional benefits to stand composition and generating mid-rotation revenue. Overall, the findings highlight some complexities and challenges with effective thinning regimes in highly shade-tolerant conifer species. [ABSTRACT FROM AUTHOR]

• Optimising restoration by using spatial patterns is increasing in demand. • Dune plant assemblages were most influenced by landscape context and urbanisation. • Mixed plantings of key tree and understorey species result in optimal restoration. • Provides a framework for setting dynamic restoration targets across landscapes. The extent, condition and connectedness of ecosystems has been significantly impacted by human activities globally, leading to a widespread appeal of and demand for ecological restoration. Maximising the ecological outcomes and cost effectiveness of restoration requires that plans be optimised by indexing the distribution, abundance and condition of habitat-forming species, and that target ecosystem conditions be developed in concert with restoration site attributes. This type of quantitative approach for creating malleable ecological targets which are informed by local environmental conditions is, however, uncommon. In this study, we surveyed the composition and coverage of understorey plants, and the composition and size of trees in coastal dunes at five transects at each of 20 sites (for n = 100) on the Sunshine Coast, central eastern Australia, and use this information to prioritise restoration sites and create optimised planting regimes for degraded sites. Each of the identified indicator species (six understorey and four tree species) had unique preferred conditions and was affected by multiple environmental and spatial variables at varying spatial scales, with most species affected by urbanisation. Species distribution models (SDMs) were used to identify target/reference ecosystems and optimal planting mixes for potential restoration sites given the site's environmental attributes. Our approach of integrating data on the distribution, abundance and condition of habitat-forming species into multiple SDMs can be used to optimise planting regimes at restoration sites and provides a framework for setting dynamic restoration targets across landscapes. [ABSTRACT FROM AUTHOR]

• Monospecific stands were more resilient than intimate mixtures to spring drought. • P. sylvestris was more resistant and resilient than P. sitchensis to spring drought. • Neighbourhood competition was not associated with drought resistance, recovery or resilience. Understanding how we can increase the resilience of forest systems to future extreme drought events is increasingly important as these events become more frequent and intense. Diversifying production forests using intimate mixtures of trees with complementary functional traits is considered as one promising silvicultural approach that may increase drought resilience. However, the direction and magnitude of the drought response of mixed-species stands relative to monospecific stands of the same species can vary with species identity, relative abundance and levels of competition in a focal tree's immediate neighbourhood. Using a long-term experiment where tree-level mortality and the neighbourhood composition of each tree was known, we assessed the radial growth response of 24-year-old Scots pine (Pinus sylvestris) and Sitka spruce (Picea sitchensis) trees in intimately mixed and monospecific stands to a short-duration, high-intensity spring drought in Scotland. Mixing proportions included 25:75, 50:50 and 75:25 of P. sylvestris and P. sitchensis. At the species level, Scots pine was more drought resistant and resilient than Sitka spruce, while Sitka spruce showed higher recovery. Surprisingly, neither pre-drought tree size nor neighbourhood competition were significantly associated with resistance or resilience to drought, and trees of both species within monospecific stands showed higher recovery and resilience than trees growing in mixed stands. Our study suggests intimate mixtures of these two species may not be an effective way to mitigate the negative impacts of future extreme spring drought events. Given that these two species comprise almost 70% of coniferous forests in the UK, our results highlight the pressing need to better understand their vulnerability to drought and the conditions under which intimate mixtures of these species could be beneficial or detrimental. Such knowledge is essential if we are to enable forest managers to effectively plan how to adapt these forests to the challenges of a changing climate. [ABSTRACT FROM AUTHOR]

• Litter decomposition rates (k) ranged from 0.273 to 3.482 depend on litterbag mesh size and tree species. • Access of soil fauna significantly increased k by 92–265% depend on mycorrhizal association. • Tree species identity is the dominant factor controlling soil fauna effects on litter decomposition. Soil fauna is one of the key drivers of the litter decomposition at both local and global scales, yet the role of tree species in mediating the effects of soil fauna on litter decomposition remains elusive. We conducted a field experiment using litterbags with three different mesh sizes that allowed access of microfauna (0.1 mm), micro- and mesofauna (2 mm), and total soil fauna (5 mm) to evaluate the decomposition of foliar litter of two tree species associated with arbuscular mycorrhizal (AM) fungi and three tree species associated with ectomycorrhizal (ECM) fungi in six Danish common garden sites. We also assessed how differences in initial litter quality, soil properties, and microbial community composition among the tree species may affect litter decomposition as well as soil fauna effects on litter decomposition. Results showed that (1) litter mass loss varied significantly among different mesh sizes and tree species, with litter decomposition rates (k) ranging from 0.273 to 3.482; (2) the access of mesofauna significantly increased litter k of 0.658 for AM and 0.396 for ECM tree species with no access of soil fauna 255 and 92%, respectively, while the access of both meso- and macrofauna increased k by 265 and 108% for AM and ECM trees, respectively; (3) tree species identity, mycorrhizal association, initial litter quality, soil properties, microbial community composition, and ambient soil fauna biomass were all significantly influencing factors on litter decomposition, but tree species identity was the dominant factor regardless of litterbag mesh size; and (4) the effects of mesofauna on litter decomposition were predominantly controlled by tree species identity, initial litter Mg concentration and lignin:N ratio, while the small additional impact of macrofauna access was not well explained by any of the assessed factors. Overall, our results suggest that tree species affect litter decomposition via different stimulation of soil fauna functioning, and that AM and ECM associated tree species differ in the degree to which soil fauna stimulates litter decomposition. However, the pattern was not entirely consistent as litter decomposition rates for the ECM associated lime were stimulated to the same extent as rates for the AM associated tree species ash and maple. Overall, our results suggested that soil meso- and macrofauna communities may enhance tree species effects on litter decomposition as well as incorporation of litter C into mineral soil. [ABSTRACT FROM AUTHOR]

• Trees at canopy gap edges grow more than can be predicted with standard methods. • These effects last longer than the period immediately after exposition. • The growth reaction patterns are species specific. • A method for canopy gap detection given terrestrial forest data was developed. • Given the importance of gaps in practice tree growth models should be revised. The structure and dynamics of Central Europe's forests are increasingly characterized by canopy gaps which either result from disturbances or from planned silvicultural actions. It remains, however, unclear, whether the neighborhood to a gap has effects on tree growth which cannot be sufficiently covered by existing standard models so far. In order to test for such effects, we used data from a series of long term experiments in Southern German mixed mountain forests. In parallel, we developed a method for an automatized detection of canopy gaps and gap edge trees given such data. We found that the basal area growth of such trees amounted to about 15–30% more compared to what could be covered by a classic spatial competition index, with a plausible ranking of the main species. Our results suggest, in addition, that an exposition to a gap has a longer lasting effect on tree growth, even after the gap has closed again. With regard to such long-term effects, we found that tree size at the first exposition matters, with strong species-specific differentiation. We concluded that gap exposition effects on tree growth, given their order of magnitude, require being included in tree growth models which are used for planning purposes. [ABSTRACT FROM AUTHOR]

• We analyzed data from 685 FIA plots from Arizona and New Mexico ponderosa pine forests. • 26% of plots burned 1996–2017; over half of these burned at moderate-high severity. • Tree mortality increased with burn severity (predicted CBI) • High burn severity was associated with shifts to non-forest vegetation types. Land management legacies coupled with climate change have led to shifts in western ponderosa pine (Pinus ponderosa) forest structure and fire regimes. A growing body of evidence suggests that under increasing area burned at high-severity, warming and drought, ponderosa pine forests are vulnerable to conversion to alternate forest types or non-forest vegetation. However, the extent and direction of recent fire-induced changes in southwestern US ponderosa pine forests have not been subject to region-wide evaluation. Here, we assess recent fire effects in ponderosa pine forests using long-term repeated samples of stand composition and structure from the US Forest Service's Forest Inventory and Analysis (FIA) program, combined with metrics of satellite-derived burn severity (predicted Composite Burn Index, CBI; and differenced normalized burn ratio, dNBR). We compiled and analyzed FIA plots dominated by ponderosa pine and associated species within the southwestern states of Arizona and New Mexico to quantify regional trends for ponderosa pine (e.g., forest losses or gains), link changes to wildfire severity, and characterize vegetation shifts. Among 685 plots sampled three times between 1996 and 2017, 26% of plots burned at least once, with more than half of these burning at moderate to high severity. Plots that burned within the study period exhibited a net loss of 46% of ponderosa pine trees, but unburned plots also exhibited a net decline of 11%. While all tree size classes exhibited greater losses than gains, tree size was a positive predictor of post-fire survival. Satellite-derived burn severity (predicted CBI) was strongly related to tree mortality and shifts toward alternate post-fire vegetation types. Severely burned stands exhibited trajectories toward non-forest vegetation with high dominance by resprouting species, particularly Gambel oak (Quercus gambelii). These findings contribute to an emerging understanding of the potential ecological outcomes of growing forest vulnerability to changing climate and disturbance regimes. Methods employed herein offer scalable opportunities to quantify changes across forest biomes using long-term monitoring data. As importantly, our findings inform regional and local land management efforts to sustain these valued forest types in an era of change. We highlight two key themes for management to promote the long-term persistence of ponderosa pine forests in the southwestern US: restoration of low-severity fire regimes and retention of large, fire-resistant trees. [ABSTRACT FROM AUTHOR]

• Size-symmetric growth dominance was predominant. • Growth dominance did not consistently vary with treatment or site quality. • Structural complexity was lower on higher quality sites and under herbicide. • Structural complexity increased with fertilization on metasedimentary soils. • Growth of small-medium sized trees was lower on more structurally complex plots. During stand initiation, the influences of silvicultural practices such as competing vegetation control and fertilization have been primarily examined in terms of stand-level growth rather than structural complexity. Understanding how intensive silvicultural treatments alter the long-term trajectory of stand development may be critical to meeting management objectives, such as habitat restoration, minimizing ladder fuels, or carbon sequestration. Previous studies have found mixed evidence for an effect of vegetation control and fertilization on structural complexity. Investigating how early pulse treatments drive tree size differentiation in young stands, as indicated by growth dominance (GD), could potentially allow managers to anticipate or design treatments to alter the development of structural complexity later in stand development. We reanalyzed data from the Garden of Eden experiment, a full-factorial study investigating how competing vegetation and nutrients impact ponderosa pine growth and yield over a gradient of site quality in northern California, USA. Our goals were to determine whether these silvicultural practices alter GD and structural complexity, and whether GD and structural complexity created potential feedbacks to alter stand productivity. We examined data for the first 20 years of stand development across 6 study sites. For each site and observation period, we calculated the growth dominance coefficient of total cubic volume to represent GD and the Gini coefficient of inequality in basal area distribution (GC) to represent structural complexity. We created a series of competing generalized additive mixed models (GAMMs) to disentangle the roles of site, stand age, and treatment on GD and GC. We created a set of competing individual-tree GAMMs at age 20 to isolate the influences of GC and GD on volume increment, controlling for the effects of competition, tree size, site, and treatment influences. In agreement with previous research, we found that GD deviated little from size-symmetry (tree growth being roughly proportional to tree size) and did not vary consistently with treatment. Competing vegetation control and higher site quality promoted lower GC, indicative of lower structural complexity. Fertilization increased structural complexity relative to other treatments on two sites in particular, which may reflect unintentional increases in drought stress from fertilization on sites with metasedimentary soils. While GD had limited influence on individual-tree growth, GC interacted with tree size such that small-medium sized trees grew more rapidly on structurally simple plots. Our results have implications for balancing objectives such as fire risk, carbon sequestration, and habitat during reforestation projects. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that the effect of forest basal area on tree growth interacts with macro-ecological gradients of primary productivity, using a large dataset of eucalypt tree growth collected across temperate and sub- tropical mesic Australia. To do this, we derived an index of inter-tree competition based on stand basal area relative to the climatically determined potential basal area. Using linear mixed effects modeling, we found that the main effects of climatic productivity, tree size and competition explained 26.5% of the deviance in individual tree growth, but adding interactions to the model could explain a further 8.9%. The effect of competition on growth interacts with the gradient of climatic productivity, with negligible effect of competition in low productivity environments, but marked negative effects at the most productive sites. We also found a positive interaction between tree size and stand basal area, which was most pronounced in the most productive sites. We interpret these patterns as reflecting intense competition for light amongst maturing trees on more productive sites, and below ground moisture limitation at low productivity sites, which results in open stands with little competition for light. These trends are consistent with the life history and stand development of eucalypt forests: in cool moist environments, light is the most limiting resource, resulting in size-asymmetric competition, while in hot, low rainfall environments are open forests with little competition for light but where the amount of tree regeneration is limited by water availability.

(1) Background: leaf structure traits are closely related to leaf photosynthesis, reflecting the ability of trees to obtain external resources in the process of growth. (2) Methods: We studied the morphological, chemical, anatomical, stomatal traits and maximum net photosynthetic rate of six broad-leaf species in northern temperate mixed broad-leaved Korean pine ( Pinus koraiensis ) forest. (3) Aim: To investigate whether there are differences in leaf structural traits of trees with different shade tolerances and different sizes and the effects of these differences on leaf photosynthetic capacity. (4) Results: the effects of leaf structure traits on leaf photosynthesis were different among trees with different shade tolerances or different sizes. Under the condition of light saturation, the net photosynthetic rate, nitrogen use efficiency, phosphorus use efficiency and stomatal conductance of shade-intolerant trees or small trees were higher than those of shade-tolerant trees or large trees. (5) Conclusions: the shade tolerance of tree species or the size of trees affect the traits of leaf structure and indirectly affect the photosynthetic ability of plants. When constructing the leaf trait-photosynthesis model, the shade tolerance and tree size of tree species should be taken into account.

Neurons and glia are the two main cell classes in the nervous systems of most animals. Although functionally distinct, neurons and glia are both characterized by multiple branching arbors stemming from the cell bodies. Glial processes are generally known to form smaller trees than neuronal dendrites. However, the full extent of morphological differences between neurons and glia in multiple species and brain regions has not yet been characterized, nor is it known whether these cells can be reliably distinguished based on geometric features alone. Here, we show that multiple supervised learning algorithms deployed on a large database of morphological reconstructions can systematically classify neuronal and glial arbors with nearly perfect accuracy and precision. Moreover, we report multiple morphometric properties, both size related and size independent, that differ substantially between these cell types. In particular, we newly identify an individual morphometric measurement, Average Branch Euclidean Length that can robustly separate neurons from glia across multiple animal models, a broad diversity of experimental conditions, and anatomical areas, with the notable exception of the cerebellum. We discuss the practical utility and physiological interpretation of this discovery., (© 2022 The Authors. Journal of Neuroscience Research published by Wiley Periodicals LLC.)

Predicting tree biomass and growth increments via allometric equations is routine in forestry, but this approach is problematic in old-growth forests unless equations are derived from trees spanning the full size range. Using intensive measurements of 27 standing Eucalyptus regnans trees 61.1–99.8 m tall and 80–430 years old in Tasmania, Victoria, and New Zealand, we develop allometric equations to predict aboveground attributes, including biomass and annual growth increments, of trees >60 m tall using ground-based measurements. Power functions of diameter underestimate biomass growth increments unless measurements are made above buttressing on the lower trunk. Growth anomalies apparent in several trees suggest that wounded E. regnans expend considerable energy to outgrow decay fungi and prevent structural collapse. Despite declining growth efficiency – defined as biomass growth per unit mass of photosynthetic tissues – with increasing tree size and age, biomass growth increments of E. regnans increase as trees enlarge with age until extrinsic forces cause mortality. The largest living E. regnans has an aboveground biomass of 215 Mg and a growth increment of 0.784 Mg year −1 , not accounting for mass loss due to decay. An even larger E. regnans tree – killed by fire in 2003 – had an aboveground biomass of ∼270 Mg, an estimated growth increment of ∼1 Mg year −1 , and was ∼480 years old at the end of its life. Prior to a stand-replacing fire in 2009, Australia’s tallest forest had a maximum aboveground biomass of 1504 Mg ha −1 and a maximum aboveground carbon mass of 706 Mg ha −1 . [ABSTRACT FROM AUTHOR]

The IPCC previsions for the upcoming decades include an increase in frequency and intensity of drought events in several regions worldwide, including Northern Europe. Drought significantly affects forest ecosystems through decreased productivity, increased vulnerability to biotic disturbances and increased subsequent mortality. How forest ecosystems maintain resistance and resilience to drought events are important questions. Our study aimed to assess whether species mixture or an individual tree size within a stand alters a given tree’s resilience and resistance to drought. A retrospective study of tree-ring widths allowed us to calculate resistance, resilience and recovery indices for five recent drought events: 1976, the 1990–1992 period, 2003, 2006 and 2010. These drought events were selected based on the SPEI (Standardized Precipitation Evapotranspiration Index) drought index. Our study sample consisted of 108 individual sessile oak ( Quercus petraea (Matt.)) or Scots pine ( Pinus sylvestris L.) trees sampled in 2012 and 2013 (Orleans forest, central France) in pure and mixed stands, divided into three diameter classes corresponding to three sizes: large, medium and small trees. Scots pine performed better than sessile oak during the 1990–1992 and 2010 droughts while the contrary was observed for the 2003 and 2006 droughts. They performed equally in 1976. We suggest that the differing sensitivity of the two species to spring and summer drought explained this result. In our study, stand composition had no effect on resilience or resistance for either species. The size effect in oaks was unclear as small oaks displayed either a better performance or a worse performance than large oaks. Small pines displayed better resistance and resilience than pines of a larger size. This work stressed the importance of taking into account stand composition and trees size as well as soil and climatic conditions for each drought events to achieve a better understanding of the diversity of responses to climatic variations among forest ecosystems. [ABSTRACT FROM AUTHOR]

Seed production, seed dispersal, and seedling recruitment are integral to forest dynamics, especially in masting species. Often these are studied separately, yet scarcely ever for species with ballistic dispersal even though this mode of dispersal is common in legume trees of tropical African rain forests. Here, we studied two dominant main-canopy tree species, Microberlinia bisulcata and Tetraberlinia bifoliolata (Caesalpinioideae), in 25 ha of primary rain forest at Korup, Cameroon, during two successive masting events (2007/2010). In the vicinity of c. 100 and 130 trees of each species, 476/580 traps caught dispersed seeds and beneath their crowns c. 57,000 pod valves per species were inspected to estimate tree-level fecundity. Seed production of trees increased non-linearly and asymptotically with increasing stem diameters. It was unequal within the two species’ populations, and differed strongly between years to foster both spatial and temporal patchiness in seed rain. The M. bisulcata trees could begin seeding at 42–44 cm diameter: at a much larger size than could T. bifoliolata (25 cm). Nevertheless, per capita life-time reproductive capacity was c. five times greater in M. bisulcata than T. bifoliolata owing to former’s larger adult stature, lower mortality rate (despite a shorter life-time) and smaller seed mass. The two species displayed strong differences in their dispersal capabilities. Inverse modelling (IM) revealed that dispersal of M. bisulcata was best described by a lognormal kernel. Most seeds landed at 10–15 m from stems, with 1% of them going beyond 80 m (<100 m). The direct estimates of fecundity significantly improved the models fitted. The lognormal also described well the seedling recruitment distribution of this species in 121 ground plots. By contrast, the lower intensity of masting and more limited dispersal of the heavier-seeded T. bifoliolata prevented reliable IM. For this species, seed density as function of distance to traps suggested a maximum dispersal distance of 40–50 m, and a correspondingly more aggregated seedling recruitment pattern ensued than for M. bisulcata . From this integrated field study, we conclude that the reproductive traits of M. bisulcata give it a considerable advantage over T. bifoliolata by better dispersing more seeds per capita to reach more suitable establishment sites, and combined with other key traits they explain its local dominance in the forest. Understanding the linkages between size at onset of maturity, individual fecundity, and dispersal capability can better inform the life-history strategies, and hence management, of co-occurring tree species in tropical forests. [ABSTRACT FROM AUTHOR]

Background and Aims: Upscaling carbon allocation requires knowledge of the variability at the scales at which data are collected and applied. Trees exhibit different growth rates and timings of wood formation. However, the factors explaining these differences remain undetermined, making samplings and estimations of the growth dynamics a complicated task, habitually based on technical rather than statistical reasons. This study explored the variability in xylem phenology among 159 balsam firs [Abies balsamea (L.) Mill.]., Methods: Wood microcores were collected weekly from April to October 2018 in a natural stand in Quebec, Canada, to detect cambial activity and wood formation timings. We tested spatial autocorrelation, tree size and cell production rates as explanatory variables of xylem phenology. We assessed sample size and margin of error for wood phenology assessment at different confidence levels., Key Results: Xylem formation lasted between 40 and 110 d, producing between 12 and 93 cells. No effect of spatial proximity or size of individuals was detected on the timings of xylem phenology. Trees with larger cell production rates showed a longer growing season, starting xylem differentiation earlier and ending later. A sample size of 23 trees produced estimates of xylem phenology at a confidence level of 95 % with a margin of error of 1 week., Conclusions: This study highlighted the high variability in the timings of wood formation among trees within an area of 1 km2. The correlation between the number of new xylem cells and the growing season length suggests a close connection between the processes of wood formation and carbon sequestration. However, the causes of the observed differences in xylem phenology remain partially unresolved. We point out the need to carefully consider sample size when assessing xylem phenology to explore the reasons underlying this variability and to allow reliable upscaling of carbon allocation in forests., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Ongoing climate warming is increasing evapotranspiration, a process that reduces plant-available water and aggravates the impact of extreme droughts during the growing season. Such an exceptional hot drought occurred in Central Europe in 2018 and caused widespread defoliation in mid-summer in European beech (Fagus sylvatica L.) forests. Here, we recorded crown damage in 2021 in nine mature even-aged beech-dominated stands in northwestern Switzerland along a crown damage severity gradient (low, medium, high) and analyzed tree-ring widths of 21 mature trees per stand. We aimed at identifying predisposing factors responsible for differences in crown damage across and within stands such as tree growth characteristics (average growth rates and year-to-year variability) and site-level variables (mean canopy height, soil properties). We found that stand-level crown damage severity was strongly related to soil water availability, inferred from tree canopy height and plant available soil water storage capacity (AWC). Trees were shorter in drier stands, had higher year-to-year variability in radial growth, and showed higher growth sensitivity to moisture conditions of previous late summer than trees growing on soils with sufficient AWC, indicating that radial growth in these forests is principally limited by soil water availability. Within-stand variation of post-drought crown damage corresponded to growth rate and tree size (diameter at breast height, DBH), i.e., smaller and slower-growing trees that face more competition, were associated with increased crown damage after the 2018 drought. These findings point to tree vigor before the extreme 2018 drought (long-term relative growth rate) as an important driver of damage severity within and across stands. Our results suggest that European beech is less likely to be able to cope with future climate change-induced extreme droughts on shallow soils with limited water retention capacity., Competing Interests: Declaration of competing interest None declared., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

• A crown width model was developed for natural spruce-fir-broadleaf mixed forest. • Tree size ineqality and competition were included in the model. • Tree size inequality had significant positive effects on tree CW. • Intra-specific competition effects on CW was larger than inter-specific competition. Crown size is strongly correlated with tree growth. Crown width (CW) is affected by tree size, site quality and competition, but most CW models do not quantify the effects of stand structure, intra and inter-specific competition, especially in mixed-species forest. In this study, we quantified these effects by developing nonlinear mixed effects CW model for natural spruce-fir-broadleaf mixed forest in northeast China. Data from a total of 10,086 individual trees in the 192 plots were used for the purpose. Plot-level random effect parameters accounting for stand heterogeneity and randomness were included in the CW model. The results showed the optimal model could explain 63% of the variation of CW with no substantial residual heterogeneity. Gini coefficient by tree size (GC) was tested as a predictor denoting tree size inequality or stand structural diversity in the model. Among all predictor variables, diameter at breast height (DBH), GC, the cumulative basal area of trees larger than the subject tree (BAL) including intra-specific (BAL intra) and inter-specific (BAL inter) competition, and height to DBH ratio (HDR) contributed most significantly to the model. Tree CW increased with the increasing GC, but decreased with the increasing HDR, BAL intra and BAL inter. The effect of intra-specific competition on CW was greater than that of inter-specific competition. Our study highlighted the importance of tree size inequality in tree CW modelling for mixed forest. [ABSTRACT FROM AUTHOR]

• Many tree-killing bark beetles attack large old trees for reasons that are unclear. • Phloem and defence traits varied with size of young and old mature lodgepole pine. • Phloem quantity and quality were greater in young stands, increasing with tree size. • Tree defences were greater in young stands and tended to increase with tree size. • Phloem thickness may not be main reason that large old trees are attacked. Tree size often predicts the occurrence of bark beetles that breed in the inner bark (phloem) of trees. A notable example is mountain pine beetle, Dendroctonus ponderosae, which primarily kills large, old trees during outbreaks. The tree mortality pattern is often attributed to increasing phloem thickness with tree size, although tree size-dependent defences may also be important. Age effects may confound interpretations of tree size effects. We examined phloem and anatomical defence traits in single-cohort lodgepole pine, Pinus contorta , stands as a function of tree size and age within and across young mature stands (trees 25–45 years old) and old stands (115–140 years old). Phloem thickness increased linearly with tree size within and across stands, more strongly for trees in young stands that had thicker phloem than same-sized trees in old stands. Phloem nitrogen was greater in young stands and did not vary with tree size. Resin duct investment was generally greater in larger trees within stands, but young trees had more and larger ducts than old trees. These results are consistent with canopy dominance of larger trees within stands that can acquire more carbon for both growth and defence; relationships between tree size and both phloem and defence traits were weaker across stands of different ages. Greater defence in young trees may reflect greater risk and costs of herbivory that might be associated with higher phloem nitrogen in younger stands. Our results suggest that the best phloem resources (quantity and quality) are found in relatively large trees in young stands, which is a poor match for the pattern of attacks by mountain pine beetles that favour large trees in old stands. Lower defences in old stands may also explain the pattern of tree mortality by beetles. Other benefits of large trees merit more attention in understanding the importance of tree size to bark beetles. [ABSTRACT FROM AUTHOR]

Global change—particularly climate change, forest management, and atmospheric deposition—has significantly altered forest growing conditions in Europe. The influences of these changes on beech growth (Fagus sylvatica L.) were investigated for the past 80 years in Belgium, using non-linear mixed effects models on ring-width chronologies of 149 mature and dominant beech trees (87–186 years old). The effects of the developmental stage (i.e., increasing tree size) were filtered out in order to focus on time-dependent growth changes. Beech radial growth was divided into a low-frequency signal (=growth rate), mainly influenced by forest management and atmospheric deposition, and into a high-frequency variability (≈mean sensitivity), mainly influenced by climate change. Between 1930 and 2008, major long-term and time-dependent changes were highlighted. The beech growth rate has decreased by about 38% since the 1950–1960s, and growth variability has increased by about 45% since the 1970–1980s. Our results indicate that (1) before the 1980s, beech growth rate was not predominantly impacted by climate change but rather by soil alteration (i.e., soil compaction and/or nitrogen deposition); and (2) since the 1980s, climate change induced more frequent and intense yearly growth reductions that amplified the growth rate decrease. The highlighted changes were similar in the two ecoregions of Belgium, although more pronounced in the lowlands than in the uplands.

Trees in urban landscapes provide a range of ecosystem services, including habitat, refugia, food, and corridors for other fauna and flora. However, there is some debate whether the richness and abundance of other biodiversity supported is influenced by the provenance of trees, i.e., native or non-native. This study assessed the presence of mistletoes and birds (and nests) in 1261 street trees. There were marked differences between native and non-native street trees, with the former having a significantly higher prevalence of birds (and nests) and supporting more species and in greater densities, whilst the latter supported a higher prevalence of mistletoes. Additionally, for birds, the proximity to green space, tree size and species were also important, whilst for mistletoes, the proximity to green space, slope aspect, and tree species were significant. Preference ratios indicated that some tree species had a higher than random occurrence of birds or mistletoes, whilst others had a low abundance. The indigenous tree species, Acacia karroo Hayne was the only reasonably abundant street tree species that was important for birds, nests, and mistletoes. At the street scale, there was a positive relationship between street tree species richness and bird species richness. These results emphasise the importance of selecting appropriate tree species if biodiversity conservation is a core outcome.

Understanding how tropical trees coordinate fast growth with water consumption and carbon investment is of high relevance because climate warming may expose tropical forests to increasing stress. Thus, foresters require more information of native tree species envisaged for reforestation. This study examines the relationship between productivity and possibly growth-determining functional traits of xylem anatomy, hydraulic conductivity, foliar morphology and nutrient status in eight tree species in semi-dry Costa Rica; we further assessed the indicative value of wood density for growth rate and hydraulic efficiency. We tested the hypotheses that (i) wood density is related to both growth rate and hydraulic efficiency contrary to findings from moist tropical forests, and (ii) productivity is closely related to branch xylem properties as well as empirically determined hydraulic conductivity in these drought-adapted species. Growth rate was positively related to tree size, foliar nitrogen content, vessel diameter, specific conductivity and leaf water potential, and negatively to vessel density, wood density and δ 13 C, indicating that fast-growing tree species with light wood possessed a more efficient hydraulic system but closed their stomata relatively early to prevent xylem dysfunction. We conclude, that in tropical semi-dry climates, productivity is closely associated not only with foliar nitrogen but also with wood anatomical and hydraulic properties. Wood density proved to be a reliable indicator for growth-related, wood anatomical and hydraulic traits in these drought-adapted species. [ABSTRACT FROM AUTHOR]

Unlike many studies on the stand structure of European beech-dominated natural forests we explicitly examined the spatial variability of six general stand characteristics: density, basal area and volume of living trees, volume of deadwood, total volume and the proportion of deadwood in the total volume. We asked whether and how these stand characteristics are spatially organized and autocorrelated, and how their spatial autocorrelation varies among particular characteristics, study sites and observation scales. The study was conducted at three forest stands dominated by Fagus sylvatica L. and co-dominated by Picea abies (L.) Karsten and Abies alba Mill., which represent the few sizable remnants of beech-dominated natural forests in central Europe. Vector stem position maps of the three sites were examined by the computer-simulated placement of differently sized square sample plots (10 x 10; 20 x 20; 30 x 30; 50 x 50 and 70 x 70 m). The six general stand characteristics were calculated for every simulated sample plot. Experimental semivariograms were calculated for all sampling plot (grain) sizes, model semivariograms were only fitted for 20 x 20 m plots. The spatial variability of stand characteristics significantly changes with the scale of observation. At the finest grain the spatial autocorrelation is mostly quite low and usually very nearly approximate the nugget model. However, autocorrelation increases with increasing sampling plot size. A peak in the first lag of the semivariograms was observed only at the finest grains, documenting the competition of large trees, whereas a recurring pattern of patches with similar stand characteristics was identified at larger observation scales. Nested structures formed by the high nugget and relatively less distinct but still apparent sill/range and fluctuation signal were detected in most of the model semivariograms, indicating different sources of variability operating at multiple scales. Moreover, significant differences among particular stand variables were demonstrated. The relative nugget varied from 61% (stand density) to 96% (stand volume) at the 20 x 20 m sampling plots; the autocorrelation ranges varied from more than 320 m to 64 m, respectively. The irregular periodic patchiness found (usually 400-1100 m² in size) may serve as a model for close-to-nature forestry, which emulates the spatial structures of natural forests. The level of positive spatial autocorrelation acknowledged for stand density should be reflected in an effective sampling design. For better estimates of the variance in this variable, sampling in a regular grid or stratified sampling is suggested. [ABSTRACT FROM AUTHOR]

In many parts of the world, once large and continuous forests have been replaced by a mosaic of isolated forest fragments embedded in an agricultural or urban landscape matrix. At the same time, stand characteristics such as tree population size and tree density have been strongly modified as a result of anthropogenic activities. Because increased geographical isolation can impede gene flow among forest fragments, and because decreased population size and tree density may reduce the number of local mating partners, this can be expected to lower the opportunity to trees for outcrossing, and to result in increased inbreeding, negatively impacting the viability of fragmented tree populations. In this study, we examined eight isolated stands of the wind-pollinated tree species Q. robur that strongly differed in population size, tree density and spatial isolation. In the centre of each Q. robur stand, adult leaves and seeds were collected in a circular plot, in which we evaluated the diversity and differentiation of the local pollen pool, and examined mating patterns. Most forest stands showed high proportions of out-of-plot pollen flow (range: 0.24-0.77), which were positively correlated with the number and density of adult trees within the forest stands. Despite high outcrossing rates (>0.998), seeds within seed families were stronger related than what could be expected under panmixia, which could be attributed to small but significant levels of correlated paternity (0.018-0.107) and biparental inbreeding (0.025-0.118) within the study plots. Next to increased coancestry coefficients, deviations from random mating also resulted in significant pollen pool differentiation (0.008-0.059) among seed parents. We also found that stand population size and tree density were significantly correlated to the relatedness of the seedlings and the degree of pollen differentiation within the study plots. These results suggest that, in small and isolated low density forest stands, reduced mate availability may decrease local pollen pool diversity, increasing the likelihood of consanguineous mating and pollen pool differentiation in the next generations. We conclude that preserving high levels of pollen flow within and between forest fragments may be more important in wind-pollinated tree species than what was previously thought. [ABSTRACT FROM AUTHOR]

Wood growth in trees depends on the acquisition of resources, and can vary with tree size leading to a variety of stand dynamics. Typically, larger trees obtain more resources and grow faster than smaller trees, but while light has been addressed more often, few case studies have investigated the contributions of water use and water use efficiency (WUE) within stands to isolate the tree-size dominance effect. Our sites were located near the cities of Aracruz and Eunapolis in Northeastern Brazil. We measured tree biomass growth, water use and WUE to explore patterns of growth among dominant and non-dominant trees in rainfed (1350 mm yr-1) and irrigated experimental stands in two high productivity tropical clones of Eucalyptus grandis x urophylla growing in clayey Ultisol soils. During the study period, irrigation supplied an additional 607 mm and 171 mm at the Aracruz and Eunapolis sites respectively. We tested two hypotheses; (1) larger trees transpire more water, and produce more wood per water used (higher water use efficiency, WUE) than smaller trees of the same clone and; (2) this pattern also applies if a water surplus is added via irrigation to alleviate water stress. Across both sites, we measured stand water use using sap flow sensors from August to December, and quantified wood growth on a tree-basis and then derived WUE, in kg wood per m³ of water transpired. Dominant trees showed higher rates of tree growth, water use and WUE than dominated trees for the two sites-clones and under both water supply regimes. Using the rainfed trees at Aracruz as an example, 50-kg trees grew 1.0 kg month-1 compared with growth of 100-kg trees of 3.8 kg month-1. The smaller trees would use water in a rate of 2.1 m³ month-1, compared with 3.1 m³ month-1 for the larger trees, demonstrating a higher WUE for the larger tree (1.2 kg m-3 versus 0.5 kg m-3). Our results suggest that manipulating stand density on heterogeneous stands, e.g. thinning, has the potential to minimize the tradeoffs between wood growth and tree water use in Eucalyptus grandis x urophylla plantations, mainly in tropical regions with seasonal water deficit. However, more research is needed to discern the underlying mechanisms responsible for higher WUE exhibited by dominant trees and distinct clones. [ABSTRACT FROM AUTHOR]

Highlights: [•] Metabolic Scaling Theory (MST) utilitarian model for tree canopy and height allometry. [•] A variable area local maximum LiDAR algorithm for conifer tree canopy segmentation. [•] MST-based rules increase segmentation accuracy, reducing some commission errors. [•] LiDAR based segmentation facilitates accurate landscape-scale tree inventories. [ABSTRACT FROM AUTHOR]

Highlights: [•] Value loss was tracked on dimensional lumber sawn from fire-damaged red oak trees. [•] Fire-scar size, tree size, and time were important value loss predictors. [•] Threshold values for scar size and residence time were identified. [•] Pole-size trees are most vulnerable to fire-caused value loss. [ABSTRACT FROM AUTHOR]

Abstract: Urban conditions have been thought to affect tree growth, but there is little conclusive evidence as to the severity of those influences or how various species respond differentially to urban stress. Reduced growth expectations are important to understand, because they affect design choices for the urban tree canopy, particularly as required by legislative mandate. Five tree species (Acer rubrum, Prunus serrulata, Pyrus calleryana, Quercus pallustris and Zelkova serrata) grown in parking lots ranging from 18 to 23 years old in central and northern New Jersey, USA were studied. Tree height, diameter at breast height (DBH), and canopy radius were measured, as was apparent plant available soil (nonpaved planting zone area). Tree DBH, commonly recorded for many municipal inventories, was found to be a useful predictor of canopy area. Data were normalized within site, to facilitate multiple site analysis. Across different parking lots, reductions in tree size were consistently associated with reduced apparent soil access. A previous study from Florida, USA was used for comparison of regional data, permitting conclusions on canopy reductions, relative to specification of design space for tree establishment. [Copyright &y& Elsevier]

Abstract: Cities across North America are adopting ambitious goals to grow their urban forests. As existing trees and new planting opportunities are often located on private property, residents’ support and participation is needed in order to meet these goals. However, little research has examined support for municipal urban forestry efforts, including policies specifically targeting residential areas. The objectives of this research are to (1) assess resident’ level of support for common urban forestry policies and (2) determine if there are specific household characteristics associated with different levels of policy support. The objectives are addressed through a statistical analysis of survey responses and a qualitative examination of follow-up interviews with residents in four neighborhoods located in Mississauga (Ontario, Canada). The survey participants and their properties vary in their socioeconomic characteristics, age of development, and urban forest conditions. Our results found that the majority of residents had neutral to very positive attitudes toward common municipal policies encouraging planting and restricting removal of trees, but support levels were lower for the policies than for general statements about desired presence and size of urban trees. Several characteristics are significantly related to level of policy support, including age of household members, education-level, property-level tree density, recent tree planting activity and age of house. Interviews also highlighted residents’ apprehensions about living among tall trees and older resident's concerns with tree maintenance. The results suggest that most residents would be willing partners in urban forestry efforts, with many of these residents already actively planting and maintain trees. However, to increase support and participation rates, different types of trees – including those smaller in stature and ones that require relatively little maintenance – should be part of any planting program to meet the varying needs of households. [Copyright &y& Elsevier]

Abstract: In the United States, street tree management and planning occurs at regional, state, and local levels. However, state and federal officials charged with managing streets trees at the regional and state levels typically lack the comprehensive, detailed information available to local officials in a street tree inventory such as species composition and tree size distribution. Statewide street tree assessments employing a variety of methodologies have been conducted to fill this knowledge gap. This paper examines these past assessments and builds upon them in conducting a street tree assessment for New York State in which geographic variability in statewide street tree inventory data is accounted for through weighted averaging of estimates. [Copyright &y& Elsevier]

Stump sprouting is a widespread phenomenon in North American hardwood tree species following logging or severe crown damage from natural disturbances such as fire, wind, or insect attack. However, other than the effects of species and tree size, factors that influence the probability of sprouting are not well understood. Data from harvested stands in Pennsylvania and Connecticut, USA, were used to evaluate the effects of several variables on stump sprouting frequencies measured within the first year after cutting for several oak and other hardwood species. After adjusting for species and diameter of the "parent" tree (ortet), clearcut harvests were found to result in a higher frequency of sprouted stumps than shelterwood harvests or crop tree releases. In addition, the probability of sprouting was higher for trees in the Ridge and Valley province of Pennsylvania vs. the Appalachian Plateaus, and in general it was higher on dry vs. moist sites. After accounting for all measured variables, there remained statistically significant stand-to-stand differences in sprouting frequency that arose from unknown causes. Results should temper expectations of stump sprout contributions to regeneration stocking that are based on simple models derived from a small number of stands or a limited geographic area. On the stand-level basis at which most managers work, the actual contribution of sprouts to future stand development may vary widely from modeled expectations. [ABSTRACT FROM AUTHOR]

• Fire catalyzes climate-induced shifts in species composition and distribution. • Frequent small fires exert stronger effects on the shifts than infrequent large fires. • The results provide scientific basis for forest policymakers to understand tradeoffs among fire management strategies. Climate change is expected to increase fire activity, which has the potential to accelerate climate-induced shifts in species composition and distribution in the boreal-temperate ecotone. Wildfire can kill resident trees, and thus provide establishment opportunities for migrating tree species. However, the role of fire size and its interactions with tree species with varied life-history attributes in driving climate-induced shifts is not understood. Future fire regimes could be characterized by many small fires or a few large fires. Large and small fires create and regulate distinct burn patterns, which may influence tree-species responses and post-fire successional trajectories. Here we investigated the effects of future fire-regime variability on the boreal-temperate ecotone of northeastern China under climate change using a coupled forest dynamic model (LANDIS PRO) and ecosystem process model (LINKAGES). We simulated fire regimes using the LANDIS PRO fire module. We designed two fire scenarios (frequent, small fires and infrequent, large fires) to represent different fire regimes in terms of fire size. Results showed fire-catalyzed, climate-induced transitions from boreal to pioneer and temperate forest communities. Frequent, small fires resulted in 13% and 23% higher increases in pioneer and temperate species respectively, relative to infrequent, large fires. Therefore, species composition shifts were faster following frequent, small fires than infrequent, large fires. The results can help policymakers and forest managers determine tradeoffs among strategies to mitigate or adapt to climate change under altered fire regimes. [ABSTRACT FROM AUTHOR]

• Drought-induced tree mortality highlights need for climate mitigation treatments. • Thinning resulted in durable increases in tree growth, even during extreme drought. • Tree growth did not respond to prescribed burning. • Trees with declining growth trends responded strongly to thinning. • Tree size and local competition strongly influenced growth responses. An estimated 128 M trees died during the 2012–2016 California drought, largely in the southern Sierra Nevada Range. Prescribed burning and mechanical thinning are widely used to reduce fuels and restore ecosystem properties, but it is unclear if these treatments improve tree growth and vigor during extreme drought. This study examined tree growth responses after thinning, prescribed burning, and extreme drought at the Teakettle Experimental Forest, a historically frequent fire mixed-conifer forest in the southern Sierra Nevada of California, USA. Mechanical thinning (no thin, understory thin, and overstory thin) and prescribed burning (unburned, fall burning) were implemented in 2000–2001. Using annual growth data from increment cores, over 10,000 mapped and measured trees, and lidar-derived metrics of solar radiation and topographic wetness, we had two primary questions. First, what were the growth responses to thinning and prescribed burning treatments, and did these responses persist during the 2012–2016 drought? Second, what tree-level attributes and environmental conditions influenced growth responses to treatments and drought? Thinning increased residual tree growth and that response persisted through extreme drought 10–15 years after treatments. Growth responses were higher in overstory versus understory thinning, with differences between thinning types more pronounced during drought. Species-specific growth responses were strongest with overstory thinning, with sugar pine (Pinus lambertiana) and incense-cedar (Calocedrus decurrens) having higher growth responses compared to white fir (Abies concolor) and Jeffery pine (Pinus jeffreyi). For individual trees, factors associated with higher growth responses were declining pretreatment growth trend, smaller tree size, and post-treatment low neighborhood basal area. Growth responses were initially not influenced by topography, but topographic wetness became important during extreme drought. Mechanical thinning resulted in durable increases in residual tree growth rates during extreme drought over a decade after thinning occurred, indicating treatment longevity in mitigating drought stress. In contrast, tree growth did not improve after prescribed burning, likely due to fire effects that reduced surface fuels, but had little effect on reducing tree density. Thinning treatments promoted durable growth responses, but focusing on stand-level metrics may ignore important tree-level attributes such as localized competition and topography associated with higher water availability. Mechanical thinning was effective at improving growth in trees that had been experiencing declining growth trends, but was less effective in improving growth responses in large old trees of higher ecological importance. [ABSTRACT FROM AUTHOR]

• Study covered much of the global distributional range of mixed pine-oak forests. • Bark adaptation in Diploxylon pines has evolved effectively. • Relative bark thickness at an early age is a key fire adaptational feature. Pines (Pinus , with 120 species) and oaks (Quercus , with at least 400 species), the two principal forest forming genera of the Northern Hemisphere occur in fire affected landscapes over a large geographical area from 120°W to 150°E long, and from 10° to 60°N lat. We compiled studies of 116 such sites of which 75 sites had data of bark thickness. Taking a meta-analysis approach, here we have compared the absolute and relative bark thickness (bark thickness per unit stem diameter) of oak species sharing mixed stands to generalize adaptational significance of bark in relation to fire. For the meta-analysis we considered only natural forests with adequate evidences of fire history. We gave importance to relative bark thickness, which is less sensitive to tree size than absolute thickness while comparing species. At 100 cm girth the average absolute bark thickness was significantly higher for Diploxylon pines (3.65 cm) than for oaks (2.2 cm) and Haploxylon pines (1.65 cm). On an average, the relative bark thickness was higher for the fire adapted Diploxylon pines (6.3%) than for Quercus species, (4.4%). The resource allocation efficiency was higher in pine species than for oak species, emphasizing the importance of bark characters in their persistence and range expansion. The difference between species of two principal forest genera in relative bark thickness and hence success in fire affected landscapes across a wide geographical range strongly testifies its adaptational significance to fire. [ABSTRACT FROM AUTHOR]

• Larger resprouting eucalypts show resilience to severe drought and frequent fire. • Eucalypt mortality is highest in small trees with fire scars and thin, fibrous bark. • Eucalypt resprouting position varies with stem size, fire scarring and bark type. Increases in tree mortality linked to drought and fires have been reported across a range of forests globally over the last few decades. Forests that resprout epicormically/aerially should be the most resistant and resilient to changes in fire regime, yet they may be at risk of increased mortality, demographic shifts and changes to species composition due to the compounding effects of drought and fire. Despite this, the synergistic effects of drought and fire frequency on resprouters has received less attention than for obligate seeder tree species. Our study examined the effects of drought severity and fire frequency on the fire resistance of eucalypts (i.e., including Eucalyptus , Angophora and Corymbia) that can resprout epicormically. Following large-scale wildfires and drought in 2013, we conducted field surveys of temperate eucalypt forests in the Sydney Basin Bioregion, focusing on two major Eucalyptus forest assemblages: dry ridgetops and wet gullies. We measured tree size, previous fire damage (i.e., fire scars), bark type, mortality and resprouting position (e.g., canopy, stem, base) of reproductive-age trees. We used a Bayesian modelling approach to derive bounded estimates of response probabilities for trees sampled in each combination of drought severity (mild/moderate versus severe) and fire frequency (low versus high), as well as bounded estimates of differences between trees with and without fire scars, different bark types and drought/fire histories. Eucalypt populations in both vegetation types were resilient to increases in mortality and changes in resprouting position under severe drought and frequent fire, and mortality and resprouting position varied substantially with tree size, fire scar presence/absence and among bark types. Tree mortality and changes in resprouting position were considerably more likely in smaller trees with fire scars. Species with non-compact bark (e.g., fibrous, stringy, rough) were less resilient to lowering in resprouting position, e.g., from canopy to stem. Populations dominated by species that have small stem diameters, thin/non-compact bark and previous fire damage are likely at elevated risk of mortality and changes in resprouting position under future climate change. [ABSTRACT FROM AUTHOR]

• Whole-tree (trunk + branches) vertical volume profiles are studied across tropical species. • Vertical volume distribution is more variable across trees than across species. • Volume distribution depends on the height of attachment of the lowest branch. • Resulting models describe the volume contained up to any height in tropical trees. Tree volume equations including branches are scarce in forestry literature, especially in diverse tropical forests, where the variability in tree shapes hampers the development of overall volume descriptions. We present species-composite cumulative volume profile models that describe the volume contained up to a given height in the trunks and crowns of tropical trees. We use terrestrial laser scanning (TLS) and quantitative structure models to estimate the trunk and crown volume of 177 trees (49 species) in a lowland tropical forest in the Barro Colorado Island in Panamá. These models were fitted using multilevel mixed-effects models recognizing the diversity of architectures in tropical trees. We found that (1) the rate at which volume accumulated with height was much higher and variable in the whole tree (trunk + branches) than only in the trunk; (2) the variability in the rate of volume accumulation was three times higher in the trunk and nine times higher in the whole tree across individuals within species than between species; and (3) parameters describing the rate of volume accumulation significantly depended on the height of attachment of the lowest branch, but not on the tree size. The resulting equations can be used to estimate the proportion of volume contained up to any height in tropical trees. [ABSTRACT FROM AUTHOR]

• First quantitative analysis of seed production in temperate Eucalyptus species. • A new seed production model was developed using tree size and reproductive traits. • Fruit size was better than seed size for predicting mean annual seed production. • Quadratic mean diameter was used to estimate forest stand maturity. Quantifying mean annual tree seed production is important for conservation and forestry applications, but its estimation remains a substantial challenge. Interspecies variation in seed production is often expressed as a trade-off between seed size and seed number, forming a key component of established models of mean annual seed production in forest stands. In this study we improved on these models by quantifying additional effects from accessory costs and reproductive maturity status, using data from temperate-zone Eucalyptus species to assess model performance. Firstly, by evaluating a range of reproductive traits, we found that seed rain density was more closely associated with 'fruit cost per seed' measures than seed size measures. For the most common measure of seed rain density (based on direct observations of free seed fall), woody capsule surface area per viable seed explained 70% of observed variation, while seed mass explained only 28% (n = 16 species). Secondly, an existing model based on seed mass, tree size and tree density was extended to include a stand maturity function, and to use alternative reproductive traits. For a smaller dataset with long-term observations and detailed stand measurements, the proportion of variance explained by the extended model ranged from 81 to 98% depending on trait selection (mean = 93%), with published models explaining less variance (75–83%, mean = 80%). By reframing interspecies variation in seed production as a trade-off between seed cost and seed number, we found evidence that investment in heavy fruit structures may represent a substantial constraint on seed output among forest stands from a common genus and region, although our results must be considered somewhat preliminary, given the small number of species examined. We have also developed an enhanced predictive model, which could be used with stand-level models for tree size and tree density to improve predictions of mean annual forest seed production in landscape simulations. [ABSTRACT FROM AUTHOR]

Genetic Programming (GP) has been successfully applied to image classification and achieved promising results. However, most existing methods either address binary image classification tasks only or need a predefined classifier to perform multi-class image classification while using GP for feature extraction. This limits their flexibility since it is unknown which combinations of classifiers and features are the most effective for an image classification task. Furthermore, high image variations increase the difficulty of feature extraction and image classification. This paper proposes a GP approach with a new program representation, new functions, and new terminals. The new approach can conduct feature extraction, feature construction, and classification, automatically and simultaneously. It can extract and construct informative image features, select a suitable classification algorithm instead of relying on a predefined classifier, and perform classification for binary and multi-class image classification tasks. In addition, this paper develops a new mutation operator based on fitness of population for dynamically adjusting the size of the evolved GP programs. The experimental results on eight datasets with different variations and difficulties show that the proposed approach achieves higher classification accuracy than most of the benchmark methods. Further analysis shows that the GP evolved programs have appropriate tree sizes and potentially high interpretability. • A new GP representation to get an effective combination of features and classifiers. • A new feature extraction layer to effectively extracting various image features. • A new feature construction layer to producing high-level features. • A new mutation operator for dynamically adjusting GP program sizes. [ABSTRACT FROM AUTHOR]

Highlights: [•] We considered attributes of forests at fragment and landscape scales simultaneously. [•] The structure of the older age classes was not severely affected by fragmentation. [•] Different groups of species respond differently to the fragmentation process. [•] The recruitment of the species of the middle stratum is affected by fragment size. [•] The recruitment of the species of the upper stratum is affected by forest cover. [ABSTRACT FROM AUTHOR]

Highlights: [•] Competition, size and age effects on BAI response to prescribed fire and thinning studied. [•] Competition and size strongly influenced BAI across all treatments. [•] Competition and size effects strongest in thin-only and burn trees, respectively. [•] Growth response to competition was size-dependent; varied among species. [•] Competition more important for tree growth response to treatments than size and age. [ABSTRACT FROM AUTHOR]

Understanding tree growth as a function of tree size is important for a multitude of ecological and management applications. Determining what limits growth is of central interest, and forest inventory permanent plots are an abundant source of long-term information but are highly complex. Observation error and multiple sources of shared variation (spatial plot effects, temporal repeated measures, and a mosaic of sampling intervals) make these data challenging to use for growth estimation. We account for these complexities and incorporate potential limiting factors (tree size, competition, and resource supply) into a hierarchical state-space model. We estimate the diameter growth of white fir (Abies concolor) in the Sierra Nevada of California from forest inventory data, showing that estimating such a model is feasible in a Bayesian framework using readily available modeling tools. In this forest, white fir growth depends strongly on tree size, total plot basal area, and unexplained variation between individual trees. Plot-level resource supply variables (representing light, water, and nutrient availability) do not have a strong impact on inventory-size trees. This approach can be applied to other networks of permanent forest plots, leading to greater ecological insights on tree growth. [ABSTRACT FROM AUTHOR]

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Abstract: Understanding the dynamic relationships between seasonal water use, stand density, and tree size in semi-arid forests of the southwestern US is important for predicting climate change impacts and for tailoring forest restoration prescriptions to mitigate such impacts. Using hydrogen stable isotope ratio (δD) analyses of precipitation, soil water, and stem water over a 2-year sampling period, we found that winter precipitation was the dominant water source for ponderosa pines (Pinus ponderosa Dougl.) in northern Arizona in all seasons. Soil and stem waters were isotopically more enriched in high- than low-density stands. Isotopic analyses indicated large trees were more reliant on deep soil water than small trees. Our results indicate that management actions that maintain or create low-density stands of large deeply-rooted trees increase tree access to winter precipitation via deep soil storage and thus may help mitigate impacts of climate warming on tree health. Our findings provide new understanding of the complex relationships among seasonal water use, stand density, and tree size in a region where a drying climate puts increasing stress on forests. [Copyright &y& Elsevier]

Abstract: Root and butt rot from Heterobasidion parviporum on Norway spruce causes severe economic losses in northern Europe and stumps from commercial thinnings are regularly treated to prevent infection. Stumps created at precommercial thinnings are, due to their small size, believed to be unable to transfer the disease. The aims of this study were to investigate the ability of small-sized Norway spruce stumps to transfer infection to neighboring trees and to determine the lower size and age limit for disease transmission. Norway spruce trees, with diameters between 2 and 14cm at stump height, were felled at 14 sites in western Sweden. The resulting stumps were inoculated with H. parviporum and disease transfer recorded at stump height in the adjacent Norway spruce trees 5years later. Stumps covering the whole span of investigated sizes and ages could transfer infection of H. parviporum and consequently a lower limit under which transfer never occurred could not be determined. The probability of finding an inoculated infection in a tree increased with increasing diameter of both tree and stump. For a given stump size, the probability of infection in the nearby tree decreased with increasing age of the stump. It seems prudent to consider the risk of introducing H. parviporum during precommercial thinning in Norway spruce dominated stands. [Copyright &y& Elsevier]

Karst made up of limestone is widely considered a "Noah's ark" of biodiversity. Rock and soil substrates comprise two different site types in karst terrain, although both can support dense forests. However, it is unclear whether and how the presence of exposed rock affects forest diversity and tree size. We established a 2.2 ha plot (200 × 110 m) in an old-growth oak forest (> 300 years) in karst terrain in southwestern China. We classified the plot into rock and soil components; we analyzed plant diversity and tree size in each component using species diversity indices (richness, number of individuals, Shannon-Wiener index, and Pielou evenness index), stand spatial structure parameters, diameter at breast height (DBH), tree height (TH), and tree basal area (BA). We also analyzed the distributional patterns of species at the sites using non-metric multidimensional scaling, then assessed the effects of abiotic environmental variables on diversity and tree size using redundancy analysis. Our results indicated that both site types (i.e., rock and soil) had similar overall species diversity; trees and shrubs were largely distributed at random within the study site. Tree size was evenly differentiated in the community, and trees were dominant, particularly on soil. Trees on rock were in a status of medium mixture, whereas shrubs on rock were highly mixed. The opposite trend was observed for trees and shrubs growing on soil. The DBH, TH, and BA were smaller in trees growing on rock than in trees growing on soil. Abiotic environmental variables had varying effects on the diversity and size of trees at the two site types; they only explained 21.76 and 14.30% of total variation, respectively. These results suggest that exposed rock has the effect of reducing tree size, but not diversity, thus highlighting the important role of rock in maintaining diversity; moreover, the results imply that karst microhabitats may mitigate the impacts of topography on tree diversity and growth. Greater attention should be focused on exposed rock in the conservation and management of karst forests and the restoration of degraded forest ecosystems., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer YD declared a shared affiliation with the author LZ to the handling editor at the time of review., (Copyright © 2022 Li, Zhang and Li.)