Quantification of biomass availability for wood harvesting and storage in the continental United States with a carbon cycle model.

BACKGROUND: Wood Harvesting and Storage (WHS) is a form of Biomass Carbon Removal and Storage (BiCRS) that utilizes a combined natural and engineered process to harvest woody biomass and put it into long term storage, most frequently in the form of subterranean burial. This paper aims to quantify the availability of woody biomass for the purposes of WHS in the continental United States using a carbon cycle modeling approach. Using a regional version of the VEGAS terrestrial carbon cycle model at 10 km resolution, this paper calculates the annual woody net primary production in the continental United States. It then applies a series of constraints to exclude woody biomass that is unavailable for WHS. These constraints include fine woody biomass, current land use, current wood utilization, land conservation, and topographical limitations. These results were then split into state by state and regional totals. RESULTS: In total, the model projects the continental United States could produce 1,274 MtCO2e (CO2 equivalent) worth of coarse woody biomass annually in a scenario with no anthropogenic land use or constraints. In a scenario with anthropogenic land use and constraints on wood availability, the model projects that 415 MtCO2e of coarse woody biomass is available for WHS annually. This is enough to offset 8.5% of the United States' 2020 greenhouse gas emissions. Of this potential, 20 MtCO2e is from the Pacific region, 77 MtCO2e is from the Western Interior, 91 MtCO2e is from the Northeast region, and 228 MtCO2e is from the Southeast region. CONCLUSION: There is enough coarse woody biomass available in the continental United States to make WHS a viable form of carbon removal and storage in the country. There is coarse woody biomass available across the continental United States. All four primary regions analyzed have enough coarse woody biomass available to justify investment in WHS projects.

Economic Evaluation of Conservation through Use of an Araucaria angustifolia Provenance and Progeny Test.

Araucaria angustifolia is a species known for its valuable wood and nuts, but it is threatened with extinction. The plantation of forests for genetic resource conservation is a complementary strategy designed to reduce the species' genetic variability loss. This study aimed to evaluate the technical and economic viability of A. angustifolia for genetic conservation through use. The analyzed provenance and progeny trial was established in 1982 in Itapeva, Brazil. It was structured using a compact family blocks design with 110 open-pollinated progenies from five natural populations, three replicates, ten plants per subplot, and 3.0 m × 2.0 m spacing. After 33 years, the trial was evaluated for total height, diameter at breast height, wood volume, and survival. The variance components and genetic parameter estimates were performed using Restricted Maximum Likelihood/Best Linear Unbiased Prediction methods (REML/BLUP) methods with the Selegen software (version 2014). The production and management scenarios were obtained using the SisAraucaria software (version 2003). Sensitivity analysis and economic parameter estimates were obtained through various economic evaluation methods using the Planin software (version 1995). In general, the genetic parameters indicated that the population has enough variability for both conservation and breeding purposes, suggesting technical viability for the establishment of a seed orchard. The economic parameters indicated that the commercialization of wood and araucaria nuts proved to be more profitable than wood production by itself. In conclusion, araucaria genetic conservation through use is a technically and economically viable ex situ conservation strategy.

Potential for large losses of carbon from non-native conifer plantations on deep peat over decadal timescales.

Peatland drainage is a large source of anthropogenic CO2 emissions. While conversion to agriculture is widely acknowledged to lead to "irrecoverable" carbon (C) losses, in contrast the C impacts of peatland forestry are poorly understood, especially in intensively managed plantations. Losses of C from peat oxidation are highly variable and can be compensated for by gains of C in trees, depending on the lifecycle of the timber and timescale considered. Here, we used ITRAX scanning to enable rapid detection of the Hekla 4 cryptotephra layer as a reliable chronological marker above which peat properties and C stocks could be compared between open and afforested blanket bog cores in the Flow Country of Northern Scotland. At one site, Bad a' Cheò, we combine replicated core pair comparisons (n = 19) with timber extraction data to derive net ecosystem C balance over the lifetime of the plantation. Here the reduction in peat C carbon storage above Hekla 4 in afforested samples (67 t C ha-1) is only partially compensated by tree C sequestration (47 t C ha-1), leading to a net ecosystem C balance indicating a loss of 20 t C ha-1 over the 50 years since the plantation was established. At that site, ∼65 % of tree C rapidly returned to the atmosphere, as it was primarily used for heat and power generation. Across the wider Flow country region, a simplified paired sampling method was adopted at eight further sites, finding a either a loss or negligible change in peat C storage above Hekla 4 in afforested samples with a mean loss of 86 t C ha-1 and median loss of 50 t C ha-1. This study suggests that potentially substantial C losses have been an unintended consequence of non-native conifer afforestation over deep blanket bogs.

Planning cost-effective operational forest inventories.

We address a Bayesian two-stage decision problem in operational forestry where the inner stage considers scheduling the harvesting to fulfill demand targets and the outer stage considers selecting the accuracy of pre-harvest inventories that are used to estimate the timber volumes of the forest tracts. The higher accuracy of the inventory enables better scheduling decisions but also implies higher costs. We focus on the outer stage, which we formulate as a maximization of the posterior value of the inventory decision under a budget constraint. The posterior value depends on the solution to the inner stage problem and its computation is analytically intractable, featuring an NP-hard binary optimization problem within a high-dimensional integral. In particular, the binary optimization problem is a special case of a generalized quadratic assignment problem. We present a practical method that solves the outer stage problem with an approximation which combines Monte Carlo sampling with a greedy, randomized method for the binary optimization problem. We derive inventory decisions for a dataset of 100 Swedish forest tracts across a range of inventory budgets and estimate the value of the information to be obtained.

A stringent failure: Regulators do not use available tools to protect aquatic ecosystems from clearcut forestry impacts in New Zealand.

Effective regulation of land-use activities in steepland areas is crucial to protect downstream ecologies and human life as intense rainfall disturbances become more frequent globally. In Aotearoa New Zealand extensive synchronous clear-cutting of Pinus radiata monocultures on steep convergent landforms, and associated earthworks, causes ongoing accelerated erosion, excessive sedimentation, and debris-laden landslides after adverse weather events. This study examines the implementation of national forestry regulations established in 2018, which also enable regional councils to create more stringent rules to protect aquatic ecosystems. All sixteen councils were surveyed in 2021 and 2022 for stringency in planning provisions; and four regions seriously affected by Cyclone Gabrielle in 2023 were resurveyed in 2024. The cyclone caused loss of human life and calamitous damage to housing, infrastructure, and productive land uses from floods exacerbated by clearcut logging debris. All councils had administratively adopted the national regulations into their existing freshwater and coastal resource management plans. Twelve councils retained existing rules that conflicted with the regulations, but these rules do not protect all regionally significant aquatic ecosystems nor minimise landslide risks. No council, except Gisborne, had instigated the expensive and lengthy statutory resource management plan change process, nor taken a 'strategic and principled' approach to develop more stringent regulations, such as tougher restrictions on clear-cutting, earthworks, and replanting on steep erosion-prone convergent landforms to protect aquatic ecosystems and vulnerable communities. The government did tighten the management of logging debris after the cyclone, but the national regulations remain ineffective in addressing clear-cut practices maladaptive to intense rainfall and continue to permit replanting on convergent landforms. The regulations need urgent amendment to require councils to develop and implement a strategic and principled approach to stringency to better protect aquatic ecosystems, human life, economic livelihoods, and public infrastructure. Water quality monitoring is also currently inadequate, as no council systematically monitors the effects of forestry activities on sedimentation rates, which inhibits the ability to compare across and between regions. Foresters are not required to monitor water quality, which also stymies assessments of compliance and policy effectiveness. Councils regularly monitor rivers, lakes, and estuaries, but rarely the effects of individual land uses. This means that sediment or other contaminants cannot be parsed to different land use activities, undermining attempts to set catchment limits. It can also take decades at current monitoring levels to defensibly show any water quality improvements after changes to land use regulations. The current environmental limits approach of setting individual water quality attribute targets is highly unlikely to drive changes to maladaptive and ecologically degrading land uses. A new environmental management approach is needed that prohibits or effectively constrains hazardous and adverse activities.

Cost-efficiency analysis of multiple ecosystem services across forest management regimes.

Forest management is at the crossroads of economic, environmental, and social goals, often requiring strategic trade-offs. As global demands surge, it's vital to employ management strategies fostering multifunctional landscapes, enabling ecosystem integrity while procuring resources. Historically, the boreal forest in Fennoscandia has been intensively managed for timber, causing environmental shifts and conflicts with biodiversity conservation and climate mitigation policies. Application of current management practices while increasing harvests are a threat to both biodiversity and carbon stocks. To explore this issue, we quantify the cost-efficiency of two forest management regimes: rotation forestry (RF) and continuous cover forestry (CCF), considering specific forest attributes like soil type (mineral and peat soils), site type (fertility classes) and tree stand age, which have been underexplored in previous research. We simulated 45,559 forest stands for 100 years in Northern boreal forests of Finland. We proposed two straightforward cost-efficiency indices (CEI) to evaluate the performance of these management regimes, specifically focusing on their impact on economic output, biodiversity conservation (measured as a biodiversity index for six forest vertebrates, including five bird species and one mammal) and carbon stock. Our findings suggest that continuous cover forestry holds the potential to deliver more cost-efficient ecosystem services and maintain greater biodiversity compared to rotation forestry approaches. Continuous cover forestry, however, is not optimal for all at management units, which calls for alternative management options depending on the stand characteristics. The cost-efficiency indices performance of rotation forestry and continuous cover forestry depend on the characteristics of the initial stand which is largely determined by the previous management of the stand. Our results contribute to guiding forest management towards enhanced sustainability and ecological balance. The great variation in stand characteristics suggest a need for diverse management strategies to create multifunctional landscapes. Our proposed cost-efficiency indices could serve as practical tools for decision-making.

Advancing forest carbon stocks' mapping using a hierarchical approach with machine learning and satellite imagery.

Remote sensing of forests is a powerful tool for monitoring the biodiversity of ecosystems, maintaining general planning, and accounting for resources. Various sensors bring together heterogeneous data, and advanced machine learning methods enable their automatic handling in wide territories. Key forest properties usually under consideration in environmental studies include dominant species, tree age, height, basal area and timber stock. Being proxies of stand productivity, they can be utilized for forest carbon stock estimation to analyze forests' status and proper climate change mitigation measures on a global scale. In this study, we aim to develop an effective machine learning-based pipeline for automatic carbon stock estimation using solely freely available and regularly updated satellite observations. We employed multispectral Sentinel-2 remote sensing data to predict forest structure characteristics and produce their detailed spatial maps. Using the Extreme Gradient Boosting (XGBoost) algorithm in classification and regression settings and management-level inventory data as reference measurements, we achieved quality of predictions of species equal to 0.75 according to the F1-score, and for stand age, height, and basal area, we achieved an accuracy of 0.75, 0.58 and 0.56, respectively, according to the R2. We focused on the growing stock volume as the main proxy to estimate forest carbon stocks on the example of the stem pool. We explored two approaches: a direct approach and a hierarchical approach. The direct approach leverages the remote sensing data to create the target maps, and the hierarchical approach calculates the target forest properties using predicted inventory characteristics and conversion equations. We estimated stem carbon stock based on the same approach: from Earth observation imagery directly and using biomass and conversion factors developed for the northern regions. Thus, our study proposes an end-to-end solution for carbon stock estimations based on the complexation of inventory data at the forest stand level, Earth observation imagery, machine learning predictions and conversion equations for the region. The presented approach enables more robust and accurate large-scale assessments using limited annotated datasets.

Genomic selection in western redcedar: from proof of concept to operational application.

Forests face many threats. While traditional breeding may be too slow to deliver well-adapted trees, genomic selection (GS) can accelerate the process. We describe a comprehensive study of GS from proof of concept to operational application in western redcedar (WRC, Thuja plicata). Using genomic data, we developed models on a training population (TrP) of trees to predict breeding values (BVs) in a target seedling population (TaP) for growth, heartwood chemistry, and foliar chemistry traits. We used cross-validation to assess prediction accuracy (PACC) in the TrP; we also validated models for early-expressed foliar traits in the TaP. Prediction accuracy was high across generations, environments, and ages. PACC was not reduced to zero among unrelated individuals in TrP and was only slightly reduced in the TaP, confirming strong linkage disequilibrium and the ability of the model to generate accurate predictions across breeding generations. Genomic BV predictions were correlated with those from pedigree but displayed a wider range of within-family variation due to the ability of GS to capture the Mendelian sampling term. Using predicted TaP BVs in multi-trait selection, we functionally implemented and integrated GS into an operational tree-breeding program.

Tree regeneration and ontogenetic strategies of northern European hemiboreal forests: transitioning towards closer-to-nature forest management.

Background: Tree ontogeny is the genetic trajectories of regenerative processes in trees, repeating in time and space, including both development and reproduction. Understanding the principles of tree ontogeny is a key priority in emulating natural ecological patterns and processes that fall within the calls for closer-to-nature forest management. By recognizing and respecting the growth and development of individual trees and forest stands, forest managers can implement strategies that align with the inherent dynamics of forest ecosystem. Therefore, this study aims to determine the ontogenetic characteristics of tree regeneration and growth in northern European hemiboreal forests. Methodology: We applied a three-step process to review i) the ontogenetic characteristics of forest trees, ii) ontogenetic strategies of trees for stand-forming species, and iii) summarise the review findings of points i and ii to propose a conceptual framework for transitioning towards closer-to-nature management of hemiboreal forest trees. To achieve this, we applied the super-organism approach to forest development as a holistic progression towards the establishment of natural stand forming ecosystems. Results: The review showed multiple aspects; first, there are unique growth and development characteristics of individual trees at the pre-generative and generative stages of ontogenesis under full and minimal light conditions. Second, there are four main modes of tree establishment, growth and development related to the light requirements of trees; they were described as ontogenetic strategies of stand-forming tree species: gap colonisers, gap successors, gap fillers and gap competitors. Third, the summary of our analysis of the ontogenetic characteristics of tree regeneration and growth in northern European hemiboreal forests shows that stand-forming species occupy multiple niche positions relative to forest dynamics modes. Conclusions: This study demonstrates the importance of understanding tree ontogeny under the pretext of closer-to-nature forest management, and its potential towards formulating sustainable forest management that emulates the natural dynamics of forest structure. We suggest that scientists and foresters can adapt closer-to-nature management strategies, such as assisted natural regeneration of trees, to improve the vitality of tree communities and overall forest health. The presented approach prioritizes ecological integrity and forest resilience, promoting assisted natural regeneration, and fostering adaptability and connectivity among plant populations in hemiboreal tree communities.

Soil drought sets site specific limits to stem radial growth and sap flow of Douglas-fir across Germany.

Introduction: Soil drought during summer in Central Europe has become more frequent and severe over the last decades. European forests are suffering increasing damage, particularly Norway spruce. Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco), a non-native tree species, is considered as a promising alternative to build drought-resilient forests. The main goal of this study was to investigate the intraannual radial stem growth and sap flow performance of Douglas-fir along a precipitation gradient across Germany under severe drought. Material and methods: Sap flow and stem radial changes of up to ten trees each at four sites with different precipitation regimes were measured in combination with volumetric soil water content during the growing season of 2022. Measurements of stem radial changes were used to calculate the trees' stem water deficit, a proxy for tree water status and drought stress. Results: The severe summer drought of 2022 led to an early growth cessation and a significant reduction in daily sap flow at all four sites monitored. We could identify a site-specific threshold in soil water availability ranging between 21.7 and 29.6% of relative extractable water (REW) under which stem water reserves cannot be replenished and thereby inhibiting radial growth. We could also demonstrate that at this threshold, sap flow is heavily reduced to between 43.5 and 53.3%, and for a REW below 50%, sap flow linearly decreases by 1.1-2.0% per 1% reduction in REW. This reduction tends to follow the humidity gradient, being more pronounced at the most oceanic characterized site and suggesting an adaptation to site conditions. Even though Douglas-fir is considered to be more drought stress resistant than Norway spruce, growth and sap flow are greatly reduced by severe summer drought, which became more frequent in recent years and their frequency and intensity is likely to increase. Conclusions: Our results suggest that timber production of Douglas-fir in Central Europe will decline considerably under projected climate change, and thus pointing to site specific growth constraints for a so far promising non-native tree species in Europe.

Optimal sway motion reduction in forestry cranes.

Introduction: The paper introduces a novel optimal feedforward controller for Hydraulic manipulators equipped with a passive grapple, addressing the issue of sway during and after movement. The controller is specifically applied to a forwarder machine used in forestry for log-loading tasks. Methods: The controller is designed for smooth operation, low computational demands, and efficient sway damping. Customizable parameters allow adjustments to suit operator preferences. The implementation was carried out using the Amesim model of a forwarder. Results: Simulation results indicate a significant reduction in sway motions, averaging a decrease of more than 60%. This performance was achieved without the need for additional sway-detection sensors, which simplifies the system design and reduces costs. Discussion: The proposed method demonstrates versatility and broad applicability, offering a new framework for anti-sway controllers in various fields such as construction cranes, forestry vehicles, aerial drones, and other robotic manipulators with passive end-effectors. This adaptability could lead to significant advances in safety and efficiency.

Potential migration pathways of broadleaved trees across the receding boreal biome under future climate change.

Climate change has triggered poleward expansions in the distributions of various taxonomic groups, including tree species. Given the ecological significance of trees as keystone species in forests and their socio-economic importance, projecting the potential future distributions of tree species is crucial for devising effective adaptation strategies for both biomass production and biodiversity conservation in future forest ecosystems. Here, we fitted physiographically informed habitat suitability models (HSMs) at 50-m resolution across Sweden (55-68° N) to estimate the potential northward expansion of seven broadleaved tree species within their leading-edge distributions in Europe under different future climate change scenarios and for different time periods. Overall, we observed that minimum temperature was the most crucial variable for comprehending the spatial distribution of broadleaved tree species at their cold limits. Our HSMs projected a complex range expansion pattern for 2100, with individualistic differences among species. However, a frequent and rather surprising pattern was a northward expansion along the east coast followed by narrow migration pathways along larger valleys towards edaphically suitable areas in the north-west, where most of the studied species were predicted to expand. The high-resolution maps generated in this study offer valuable insights for our understanding of range shift dynamics at the leading edge of southern tree species as they expand into the receding boreal biome. These maps suggest areas where broadleaved tree species could already be translocated to anticipate forest and biodiversity conservation adaptation efforts in the face of future climate change.

A comprehensive taxonomy for forest fire risk assessment: bridging methodological gaps and proposing future directions.

Forest fire risk assessment plays a crucial role in the environmental management of natural hazards, serving as a key tool in the prevention of forest fires and the protection of various species. As these risks continue to evolve with environmental changes, the pertinence of contemporary research in this field remains undiminished. This review constructs a comprehensive taxonomic framework for classifying the existing body of literature on forest fire risk assessment within forestry studies. The developed taxonomy categorizes existing studies into 8 primary categories and 23 subcategories, offering a structured perspective on the methodologies and focus areas prevalent in the domain. We categorize a sample of 170 articles to present recent trends and identify research gaps in forest fire risk assessment literature. The classification facilitates a critical evaluation of the current research landscape, identifying areas in need of further exploration. Particularly, our review identifies underrepresented methodologies such as optimization modeling and some advanced machine learning techniques, which present routes for future inquiry. Moreover, the review underscores the necessity for model development that is tailored to specific regional data sets but also adaptable to global data resources, striking a balance between local specificity and broad applicability. Emphasizing the dynamic nature of forest fire behavior, we advocate for models that integrate the burgeoning field of machine learning and multi-criteria decision analysis to refine predictive accuracy and operational effectiveness in fire risk assessment. This study highlights the great potential for new ideas in modeling techniques and emphasizes the need for increased collaboration among research communities to improve the effectiveness of assessing forest fire risks.

Soil carbon storage under different types of arid land use in Algeria.

This study aims to assess the amount of organic carbon stored in soils, as it is an intention of knowing the sustainable soil management, by using two common methods for determining soil organic matter (SOM), namely oxidation with acidified wet dichromate (Walkley-Black method-WB) and loss on ignition (LOI). The study was carried with soil samples collected from a depth of 0 to 30 cm in the Saharan arid region of Ghardaïa (Algeria), with different land uses: agricultural, forest and pastoral. The results obtained from the LOI and WB methods were subjected to statistical analysis, and the relations between both methods were tested to investigate their relationship. The mean percentage of SOM values were 1.86, 2.42, 1.54 by using LOI, but, lower values of 0.34, 0.33, 0.36 were determined by using WB method, for agricultural, forest and pastoral soils respectively. A weak linear relationship between the two analytical procedures was obtained (R2 of 0.19 and 0.13 for agricultural and forest soils), while a medium relationship (R2 = 0.65) was found for pastoral soils when using linear adjustment. However, the opposite behaviour was found when we use the logarithmic adjustment. The study outcomes indicated discrepancies in the measurements of SOM values between the two methods, been higher those estimated with LOI. Finally, in order to identify the best methodology to measure soil organic matter in arid soils, more research is required in these extreme arid regions as they are a gap in world soil organic matter maps.

The potential of non-native tree species to provide major ecosystem services in Austrian forests.

Forestry is facing an unprecedented challenging time. Due to climate change, major tree species, which until recently fulfilled major ecosystem services, are being lost and it is often unclear if forest conversion with other native or non-native tree species (NNT) are able to maintain or restore the endangered ecosystem services. Using data from the Austrian Forest Inventory, we analysed the current and future (2081-2100, RCP 4.5 and RCP 8.5) productivity of forests, as well as their protective function (avalanches and rockfall). Five different species change scenarios were considered for the replacement of a tree species failing in the future. We used seven native tree species (Picea abies, Abies alba, Pinus sylvestris, Larix decidua, Fagus sylvatica, Quercus robur and Quercus petraea) and nine NNT (Pseudotsuga menziesii, Abies grandis, Thuja plicata, Pinus radiata, Pinus contorta, Robinia pseudoacacia, Quercus rubra, Fraxinus pennsylvanica and Juglans nigra). The results show that no adaptation would lead to a loss of productivity and a decrease in tree species richness. The combined use of native and NNT is more favorable than purely using native species in terms of productivity and tree species richness. The impact of the different species change scenarios can vary greatly between the different environmental zones of Austria (Alpine south, Continental and Pannonian). The Pannonian zone would benefit from the use of NNT in terms of timber production. For the protection against avalanches or rockfall in alpine regions, NNT would not be an advantage, and it is more important if broadleaved or coniferous trees are used. Depending on whether timber production, protective function or tree species richness are considered, different tree species or species change scenarios can be recommended. Especially in protective forests, other aspects are essential compared to commercial forests. Our results provide a basis for forest owners/managers in three European environmental zones to make decisions on a sustainable selection of tree species to plant in the face of climate change.

Anti-Leptospira Seroprevalence and Associated Risk Factors among Forestry Workers in Lower Saxony, North-West Germany.

As leptospirosis is re-emerging, a seroprevalence study was conducted, assessing the prevalence of anti-Leptospira IgG antibodies and infection-associated risk factors among forestry workers (FWs) in Lower Saxony, Germany, to develop targeted public health measures. Sera of 877 FWs, sampled in 2016, were tested for anti-Leptospira seropositivity by commercial IgG-ELISA. Data on demographics and Leptospira-specific exposures, knowledge, sources of information, and preventive measures were collected by standardized, self-administered questionnaire. A subset of 244 sera was retested via in-house IgG-ELISA. Risk factors were assessed from the subset using multivariable logistic regression analysis. The commercial IgG-ELISA revealed a seroprevalence of 4.8% (95% confidence interval CI95 = 3.5-6.4). Of the 601 FWs who completed the questionnaire, 67.9% had been informed about leptospirosis and Leptospira spp., mainly by employers (55.2%) and peers (38.9%). Positive associations with seropositivity were observed for canoeing (adjusted odds ratio (aOR) = 2.35, p = 0.044), touching rodents (aOR = 2.4, p = 0.021), and living close to beech trees (aOR = 2.18, p = 0.075). Frequently cleaning animal stables was negatively associated (aOR = 0.20, p = 0.002). The unexpected positive association with wearing gloves when handling plants and soil (aOR = 2.16, p = 0.011) needs further discussion. Overall, seroprevalence was in the range of other studies in Germany. The identified factors will be used to develop targeted information reaching out to at-risk groups tapping various communication channels.

Retention forestry as a climate solution: Assessing biomass, soil carbon and albedo impacts in a northern temperate coniferous forest.

Forest management pathways for nature-based climate solutions, such as variable retention harvesting (VRH), have been gaining traction in recent years; however, their net biochemical and biophysical impacts remain unknown. Here, we use a combination of close-range and satellite remote sensing, eddy covariance technique, and ground-based biometric measurements to investigate forest thinning density and aggregation that maintain ecosystem nutrients, enhance tree growth and provide a negative feedback to the local climate in a northern temperate coniferous forest stand in Ontario, Canada. Our results showed that soil carbon (C) and nitrogen (N) in VRH plots were significantly lower (p < 0.05) for all VRH treatments compared to unharvested plots. On average, soil C was reduced by -0.64 ± 0.22 Δ% C and N by -0.023 ± 0.008 Δ% N in VRH plots. We also observed the largest loss of soil C and N in open areas of aggregate plots. Furthermore, the changes in albedo resulting from VRH treatment were equivalent to removing a large amount of C from the atmosphere, ranging from 1.3 ± 0.2 kg C yr-1 m-2 in aggregate 33 % crown retention plots to 3.4 ± 0.5 kg C yr-1 m-2 in dispersed 33 % crown retention plots. Our findings indicate that spatially dispersed VRH resulted in minimal loss of soil C and N and the highest understory growth and C uptake, while enhanced tree growth and local cooling through increased albedo were observed in dispersed VRH plots with the fewest residual trees. These findings suggest that using the harvested trees from VRH in a way that avoids releasing C into the atmosphere makes dispersed VRH the preferred forest management pathway for nature-based climate solutions.

Public safety considerations constraint the conservation of large old trees and their crucial ecological heritage in urban green spaces.

Large old trees in urban public green spaces deliver a diversity of values essential for human well-being, including biodiversity conservation. Yet, the conservation of large old trees bearing key wildlife microhabitats interferes with safety considerations. This intuitive notion, however, is backed by an insufficient and scattered body of evidence. Here, we empirically examined this process using data on 5974 trees across 510 sample plots, organized as quintuplets within 102 sample sites, including urban parks, cemeteries, recreational forests, and historic reserves in the urban agglomeration of Kraków, Poland. Our analyses demonstrate that trees situated in areas frequently visited by people, or those near walking paths, benches, or playgrounds, have elevated accident hazards and, therefore, necessitate intensive tree surgeries (pruning and logging) to remain harmless. Large old trees, which bear the most diverse microhabitats and pose greater risks when they collapse, are especially affected by these measures. Accordingly, we found that the co-occurrence of large trees with elevated accident hazards results in significant losses of dead and sloped trees, and trees with cavities, injuries, crown deadwood, fungal fruiting bodies, or epiphytes, particularly in parks and, to a lesser extent, in recreational forests. Apparently, some tree-related microhabitats, such as injuries, cavities, and microsoils, also emerge in risky spots after pruning. Our findings underscore that the conservation of large old trees and their ecological functions faces significant challenges due to safety considerations. To address conservation challenges and harmonize human coexistence with biodiversity, we recommend enhancing environmental awareness and reevaluating arboricultural and planning policies. This would involve establishing strategic and pocket reserves on city peripheries and interiors, allowing larger older trees to thrive and develop important microhabitats without compromising public safety. Otherwise, we risk losing many large old trees and/or their superior value for wildlife, which will regenerate over decades, if not centuries.