Young Forests Research Articles

Mismatch between strong nest-site selection and low survival of nests and broods for Scolopax minor (American Woodcock) and its implications for conservation

Abstract Nest-site selection may reduce predation and enhance recruitment, especially in ground-nesting birds. Few studies have examined both nest-site selection and its potential effects on nesting success, even though predation risk and exposure to inclement weather may limit the effectiveness of nest-site selection. We assessed home range and local-scale nest-site selection of Scolopax minor (American Woodcock) as well as nest and brood survival in Rhode Island, USA during the breeding seasons (March 15 to June 15) of 2020–2022. Specifically, we employed a use/available design and conditional logistic regression models to evaluate nest-site selection and used the Program MARK to estimate nest and brood survival. At the home-range scale, we found that nesting woodcock selected for early successional cover types (i.e., pastures, grasslands, or regenerating clearcuts) and areas closer to upland young forest and reverting agricultural openings. They also occupied forests and wetlands of varied species composition and age (i.e., upland young forests as well as upland and wetland deciduous forests, and emergent wetlands). At the local scale, females selected nest sites that provided visual concealment of the nest. Despite nest-site selection at two spatial scales, nest and brood survival were low (10% and 16%, respectively) and were not influenced by vegetation, landscape configuration, and weather. Given that woodcock nest-site selection is driven by vegetative structure and concealment, yet reproductive success was low, future management should experimentally alter forests to identify forest configurations that help mitigate predation and increase cover in fragmented landscapes, such as Rhode Island.

Effects of Stand Age and Environmental Factors on Soil Phytolith-Occluded Organic Carbon Accumulation of Cunninghamia Lanceolata Forests in Southwest Subtropics of China

The area of Cunninghamia lanceolata forests in China is expansive, the soil PhytOC(phytolith-occluded organic carbon) stock of Cunninghamia lanceolata forests is a vital carbon reservoir on the global scale. Soil from the Cunninghamia lanceolata forests was collected, and the soil physicochemical indexes and phytoliths and PhytOC content were measured to explore the accumulation characteristics of PhytOC in the 0–10, 10−20, and 20−30 cm soil layers at different stand ages. The results are as follows: (1) soil phytolith content (11.98–32.60 g·kg−1), PhytOC content (0.48−1.10 g·kg−1), PhytOC/TSOC (1.90%−6.93%), soil PhytOC stock (0.446−1.491 t·hm−2), and mature forest > middle−aged forest > Huitou−sha forest > young forest. The soil PhytOC accumulation was significantly affected by stand age. Huitou−sha is not an advantageous afforestation way of Cunninghamia lanceolata. (2) the soil physicochemical properties and stand conditions had significant effects on soil PhytOC accumulation. High−silicon, carbon-rich, acidic soil environment and appropriate thinning are conducive to phytolith formation and PhytOC sequestration. (3) the accumulation potential of soil PhytOC in the Cunninghamia lanceolata forest is relatively large, and its importance as a forest carbon sink cannot be ignored. Soil PhytOC stock in Cunninghamia lanceolata forests of different stand ages will lay a foundation for accurate estimation of forest carbon sink.

Biophysical impact of forest age changes on land surface temperature in China.

Forest age structures have been substantially affected by natural disturbances and anthropogenic activities worldwide. Their changes can significantly influence local and nonlocal climate through both the biogeochemical and biophysical processes. However, numerous studies have focused on the biogeochemical effect of forest age changes whereas the biophysical effect has received far less attention. Here we investigated how forest age changes influence land surface temperature (LST) by comparing older forests and adjacent younger forests pixels and unraveled underlying biophysical mechanisms using satellite observations over China during 2003-2012. Our study showed that older forests had a substantial annual cooling benefit than adjacent medium-aged and young forests. Attribution analysis indicated that the cooling effect of latent heat flux counteracted the albedo-induced warming effect, leading to the net cooling effect of older evergreen needle-leaved forest or evergreen broadleaved forest. Furthermore, the cooling effect of sensible heat flux is greater than the albedo-driven warming effect, contributing to the net cooling effect of older deciduous broadleaved forest. Our work is a step forward to underscore the potential of preserving mature forests as a local climate adaptation strategy and provides important parameterization foundation for earth system models without incorporation of forest age modules.

Seasonal warming responses of the carbon dioxide sink from northern forests are sensitive to stand age

Northern forests (forests north of 30°N) are major terrestrial carbon dioxide (CO2) sinks, while rapid warming can disturb their CO2 sink function. Here we use multi-year net CO2 exchange observations from 65 northern forest sites to show that the increased net CO2 uptake during warmer springs was more pronounced in old forests (>90 years old) compared to young (<40 years old) and mid-aged (40–90 years old) forests. In addition, the decreased net CO2 uptake during warmer summers and autumns was more pronounced in young forests compared to mid- and old-aged forests. Annually, this resulted in an increase in net CO2 uptake due to seasonal warming for old forests (4.8 g C m−2 yr-1) and a decrease in young- and mid-aged forests (3.2 and 0.8 g C m−2 yr-1, respectively). In future projections, increasingly uneven seasonal warming may amplify the impacts of stand age on CO2 sinks of northern forests.

Effects of forest age and stand density on the growth, soil moisture content, and soil carbon content of Populus simoni plantations in the sandy area of western Liaoning, Northeast China

Poplar (Populus simoni) plantations are crucial in the sandy regions of western Liaoning, serving key roles in wind protection, sand stabilization, soil moisture regulation, and carbon sequestration. However, challenges such as suboptimal stand quality and limited ecological benefits persist. This study aims to elucidate the growth dynamics of poplar plantations and their impact on soil moisture content and soil carbon content in this region. We established 75 standard plots across various age groups and stand densities in Fuxin City, measuring poplar diameter at breast height (DBH), tree height (TH), soil moisture content, and soil carbon content. We found that DBH and TH increase with increasing stand density in young and middle-aged forests, but the opposite is true at near-maturity, maturity, and over-maturity, where DBH and TH decrease with increasing stand density. Soil moisture content rises with stand density in younger forests, while soil carbon content increases with age, with surface soil layers exhibiting higher carbon concentrations. The soil carbon stock in these plantations is approximately 3.0 × 106 tons, the highest recorded in Fuxin City. This research provides a foundation for the effective management and development of poplar plantations in wind-prone, sandy areas. Overall, optimizing stand density and managing forest age distribution are essential for enhancing the ecological and carbon sequestration benefits of poplar plantations in this region.

Tree-volume and forest age increase bat species diversity in boreal urban landscape

ContextGiven the rate at which humankind is changing habitats, it is essential to understand its impact on the surrounding nature and biota. The intensification of human activities and the fragmentation of forested habitats now affect many taxonomic groups, such as bats, which are largely dependent on forests (e.g. roosting sites and feeding areas). Northern Europe is generally considered very forested but intensive land-use changes, caused by urbanization and forestry, contribute to forest fragmentation and loss of biodiversity. Land-use changes are classified as the biggest threats for bats, but especially in the boreal zone, the impact of these environmental changes is not yet known at a sufficient level.ObjectivesWe explored how bats (species occurrences and activity) were influenced by forestry and urbanization, and by landscape variables (tree volume, percentage of deciduous trees, vicinity of water bodies and built areas).MethodsWe used a bioacoustic dataset on bats from Finnish capital area (20 × 20 km, 51 sites) recorded during the summer season (May – September) to evaluate how different habitat classes (old forest, young economical forest, rural area, suburban and urban) and landscape variables influence activity and species richness of bats across this region. We used Hierarchical Modelling of Species Communities (HMSC) approach to characterize the responses of species. We investigated with two different models: one focusing on species occurrences and the second one focusing on relative activity.ResultsOur findings indicate a distinct pattern, with the highest species richness in old forests, followed by a gradual decline with increased land-use intensity. Species-specific responses to habitat classes were evident in both presence and activity. Most of the species showed negative responses to built area, either by their presence or activity. Key landscape variables further underscored species-specific variations in different environmental conditions. Additionally, our study observed temporal dynamics, revealing species-specific variations in occurrences across the bats’ active season.ConclusionOur study sheds light on the complex dynamics of bats in diverse landscapes, emphasizing the crucial role of both habitats and specific environmental factors in conservation. Old natural forests emerge as vital for bats, while land-use changes, especially urbanization, pose challenges highlighting the need for continuous monitoring and strategic conservation actions.

From overgrazed land to forests: assessing soil health in the Caatinga biome.

Overgrazing is the primary human-induced cause of soil degradation in the Caatinga biome, intensely threatening lands vulnerable to desertification. Grazing exclusion, a simple and cost-effective practice, could restore soils' ecological functions. However, comprehensive insights into the effects of overgrazing and grazing exclusion on Caatinga soils' multifunctionality are lacking. This study examines (i) how overgrazing impacts multiple soil indicators, functions, and overall soil health (SH) and (ii) whether natural early forest growth post-grazing exclusion enhances critical soil functions for ecosystem restoration. We compared preserved dense forests, long-term overgrazed pastures (over 30 years), and young fenced-off open forests (three years old) along a longitudinal transect in the Caatinga biome: 36°W (São Bento do Una), 37°W (Sertânia), and 40°W (Araripina). Soil samples from the 0-20cm layer were analyzed for thirteen physical, chemical, and biological indicators for a structured SH assessment, calculating index scores based on soil functions. Forest-to-pasture transition and subsequent overgrazing consistently compacted the soils and decreased nitrogen, carbon (C), microbial biomass C, and glomalin protein, thus degrading the soil's physical, chemical, and biological functions. Regionally, this conversion depleted 14.7MgC ha-1 and reduced overall SH scores by 18%, severely impacting biological functions (e.g., -43% for sustaining biological activity). No significant differences in functions or SH were found between grazed pastures and open forests. SH scores and C stocks were highly interrelated (r>0.5; p<0.001), suggesting that C losses and SH deterioration were closely aligned. We conclude that overgrazing degrades soil multifunctionality and health across the Caatinga biome, with biological functions most severely damaged and legacies obstructing soil recovery for up to three years of grazing exclusion. Future SH studies should include open forest chronosequences with older ages and active restoration practices (e.g., planting trees or green manure) to enhance Caatinga's ecological restoration knowledge and efforts.

Seasonal Bird Communities in Shelterwood Harvests and Unmanaged Mature Forest

Effective bird conservation planning requires consideration of year-round habitat requirements. We evaluated how bird communities differed across seasons, and between young shelterwood (SW) and unmanaged mature (M) hardwood forests over 8 years. We detected 3,952 individuals of 82 bird species within transects. Total abundance, richness, and diversity were highest in summer and lowest in winter. Richness was greater in SW than M during all seasons; abundance and diversity were greater in SW during summer, fall, and spring. Community composition differed between SW and M during all seasons except winter. Within seasons, abundance of most analyzed species was greater in SW than M or similar between the treatments. In SW young forest habitat suitability for most species (except indigo buntings) persisted for at least 8 years. Residency guilds and some species showed greater habitat selectivity in some seasons (heavier use of SW) than others (similar use of both SW and M). Our study illustrates the important role of young forests in promoting bird diversity year-round. However, knowledge gaps remain regarding bird use of all forest age-classes during all seasons, and how long dynamically changing young forests support more birds and bird species than mature forest during non-breeding seasons.

Rapid Increase in Soil Respiration and Reduction in Soil Nitrate Availability Following CO2 Enrichment in a Mature Oak Forest.

In the future, with elevated atmospheric CO2 (eCO2), forests are expected to increase woody biomass to capture more carbon (C), though this is dependent on soil nutrient availability. While young forests may access unused nutrients by growing into an unexplored soil environment, it is unclear how or if mature forests can adapt belowground under eCO2. Soil respiration (R s) and nutrient bioavailability are integrative ecosystem measures of below-ground dynamics. At Birmingham's Institute of Forest Research Free Air CO2 Enrichment (BIFoR FACE) facility, we investigated the effects of eCO2 (+150 ppm above ambient) on a mature oak forest during the first year of exposure. We observed an annual Rs increase of ∼21.5%; 996 ± 398 g C m-2 year-1 (ambient) to 1210 ± 483 g C m-2 year-1 (eCO2). The eCO2 impact was greater on belowground nutrient cycling, with monthly nitrate availability decreasing by up to 36%. These results show that high C uptake resulted in higher soil respiration with a concomitant decrease in the level of soil nitrate during the first year. These belowground responses and their long-term dynamics will have implications for the carbon budget of mature forest ecosystems in changing climate.

Great Tit (Parus major) Nestlings Have Longer Telomeres in Old-Growth Forests Than in Young Forests.

Modification and deterioration of old-growth forests by industrial forestry have seriously threatened species diversity worldwide. The loss of natural habitats increases the concentration of circulating glucocorticoids and incurs chronic stress in animals, influencing the immune system, growth, survival, and lifespan of animals inhabiting such areas. In this study, we tested whether great tit (Parus major) nestlings grown in old-growth unmanaged coniferous forests have longer telomeres than great tit nestlings developing in young managed coniferous forests. This study showed that the patches of young managed coniferous forests had lower larval biomass than old-growth forests. Since insect larvae are the preferred food for great tit nestlings, the shortage of food may divert energy resources away from growth, which can show up as physiological stress, often raising the heterophil/lymphocyte (H/L) ratio. The H/L ratio revealed a significant difference in stress levels, being the highest in great tit nestlings developing in young-managed pine forests. We also found that the development of great tit nestlings in young managed forests had significantly shorter telomeres than in old-growth forests. Although nestling survival did not differ between the habitats, nestlings growing up in old-growth forests had greater telomere lengths, which can positively affect their lifespan. Our results suggest that the forest habitats affected by industrial forestry may represent ecological traps, as the development of young birds in deteriorated environments can affect the age structure of populations.

Canopy complexity drives positive effects of tree diversity on productivity in two tree diversity experiments.

Forest canopy complexity (i.e., the three-dimensional structure of the canopy) is often associated with increased species diversity as well as high primary productivity across natural forests. However, canopy complexity, tree diversity, and productivity are often confounded in natural forests, and the mechanisms of these relationships remain unclear. Here, we used two large tree diversity experiments in North America to assess three hypotheses: (1) increasing tree diversity leads to increased canopy complexity, (2) canopy complexity is positively related to tree productivity, and (3) the relationship between tree diversity and tree productivity is indirect and driven by the positive effects of canopy complexity. We found that increasing tree diversity from monocultures to mixtures of 12 species increases canopy complexity and productivity by up to 71% and 73%, respectively. Moreover, structural equation modeling indicates that the effects of tree diversity on productivity are indirect and mediated primarily by changes in internal canopy complexity. Ultimately, we suggest that increasing canopy complexity can be a major mechanism by which tree diversity enhances productivity in young forests.

Nitrogen addition accelerates aboveground biomass sequestration in old-growth forests by stimulating ectomycorrhizal tree growth.

Examining whether nitrogen (N) enrichment promotes secondary tree growth in both young (YF) and old-growth forests (OF) is crucial. This will help determine how N addition influences plant carbon sequestration across successional phases in temperate forests. We conducted an eight-year N addition experiment (0, 25, 50, 75kgN ha-1 yr-1) in YF and OF in northeast China to investigate the effects of enhanced in situ N deposition on tree growth. Our results indicated that N addition accelerated the accumulation of annual mean aboveground biomass (ΔAGB) of trees only in OF. Specifically, for the species co-occurring in both YF and OF plots, their ΔAGB in OF peaked under the medium N treatment (3.69Mgha-1 yr-1), which was 2.3 times higher than that of YF (1.58Mgha-1 yr-1). Regarding mycorrhizal types, only the ΔAGB of EcM-associated trees peaked under the high N treatment (2.81Mgha-1 yr-1), increasing by 126.6% compared to the control (1.24Mgha-1 yr-1). This increase in biomass primarily came from large trees with a DBH ≥15cm, most of which are EcM -associated species, such as Pinus koraiensis. In conclusion, continuous N addition increases nutrient supply and alleviates N limitation in old growth forest, leading to faster biomass accumulation. The growth of large-diameter trees with EcM-associated may contribute significantly to aboveground biomass accmulation under N addition. Nutrient limitation is dependent on stand age, mycorrhizal type and size, so these factors must be considered when assessing forest nutrient limitations.

The Effect of Pre- and Post-Processing Techniques on Tree Detection in Young Forest Stands from Images of Snow Cover Using YOLO Neural Networks

A neural network model for individual tree detection was developed based on the YOLOv4 architecture, which underwent additional preprocessing and postprocessing steps. The preprocessing step involved expanding the dataset by randomly cutting fragments from images, calculating anchor box sizes using the K-means clustering algorithm, and discarding anchor boxes that were too small a priori. The existing post-processing block of the YOLO architecture was modified by giving more weight to false positives in the error function and using the non-maximum suppression algorithm. Baseline neural networks from the YOLOv4 and YOLOv5 architectures, each in two versions (pre-trained and not pre-trained on the MS COCO dataset), were used for comparison without any additional modifications. In the overgrown experimental field, multi-season aerial copter surveys and ground counts were conducted on several sample plots to gather data. Comparison of multi-season aerial photographs with ground-count data showed that the best images in terms of the percentage of visually identifiable trees were those taken during the snowy season and when there was no foliage. Using these images and some additional images, we manually created a dataset on which we trained and tested neural network models. The model we developed showed significantly better results (2 to 10 times better) on the mAP 0.5 metric compared to the alternatives we considered.

Динамика биометрических и углеродных показателей сосновых насаждений на залежных землях Красноярской лесостепи

Today, the overgrowth of woody and shrubby vegetation on former agricultural lands is a serious problem. The aim of this research has been to investigate age-related changes in the forest inventory indicators of forest stands on abandoned farmlands. Taking into account the temporal factor when monitoring the carbon budget allows identifying a number of processes in the dynamics of carbon sequestration that cannot be estimated in a single study. To address this issue, data from permanent sample plots have been analyzed in 2011 with repeated measurements in 2023. The sample plots are located on the abandoned farmlands on the border of the Krasnoyarsk forest-steppe area. The dynamics of the process of Today, the overgrowth of woody and shrubby vegetation on former agricultural lands is a serious problem. The aim of this research has been to investigate age-related changes in the forest inventory indicators of forest stands on abandoned farmlands. Taking into account the temporal factor when monitoring the carbon budget allows identifying a number of processes in the dynamics of carbon sequestration that cannot be estimated in a single study. To address this issue, data from permanent sample plots have been analyzed in 2011 with repeated measurements in 2023. The sample plots are located on the abandoned farmlands on the border of the Krasnoyarsk forest-steppe area. The dynamics of the process of overgrowth and development of plantations has shown that as the abandoned farmlands form, in addition to the dominant Scots pine (Pinus sylvestris L.), silver birch (Betula pendula Roth) and aspen (Populus tremula L.), Siberian larch (Larix sibirica Ledeb.), Siberian spruce (Picea obovata Ledeb.) and goat willow (Salix caprea L.) are also found. The dynamic process of pine abandoned farmlands has been established over a period of 15 to 27 years after land abandonment. The mixed plantations of various successional origins have ranged in age from 10 to 30 years old. Various processes have been observed in the research plots in terms of changes in the density of abandoned farmlands (overgrowth, thinning). The reforestation of abandoned farmlands occurs from the forest border and at a distance of up to 50 m continues after 30 years. The abandoned farmlands are characterized by various forms of overgrowth: clumps, biogroups, complete and by single trees. The average quantitative assessment has shown that that the most intense changes in height, diameter, height to the crown base, height to the largest crown width, and crown diameters have occurred in the test area where the minimum density has been observed, which has been decreasing dynamically. In the plot with the maximum density, morphological indicators have been characterized by an average increase. Minimal changes have been recorded in the sample plot where the density has increased significantly over 12 years. The growth rate of trees of the same diameter in height has been greater in 2023 compared to 2011. It is possible that this has been influenced by a combination of external and internal factors, including climate change. To assess the carbon productivity of forest stands growing on the abandoned farmlands, it is advisable to use regression equations developed for a specific area. The results of the study of the dynamics of carbon sequestration by young forests growing on the abandoned farmlands indicate the feasibility of using postagrarian lands for the implementation of forest climate projects.

Application of the Stacking-InSAR method for analyzing changes in forest canopy height

The brief communication demonstrates the potential for quantitative assessment of forest canopy height dynamics in mature and young pine forests on a plain using the method of weighted summing of time series of unwrapped interferometric phases. The latter were obtained using a modern approach based on cloud computations. By comparing the rates of canopy height growth for the years 2017, 2018, and 2019, it has been confirmed that the growth rate is influenced by the amount of precipitation in May-July of the respective year.

Drivers of biomass stocks and productivity of tropical secondary forests.

Young tropical secondary forests play an important role in the local and global carbon cycles because of their large area and rapid biomass accumulation rates. This study examines how environmental conditions and forest attributes shape biomass compartments and the productivity of young tropical secondary forests. We compared 36 young secondary forest stands that differed in the time since agricultural land abandonment (2.3-3.6 years) from dry and wet regions in Ghana. We quantified biomass stocks in living and dead stems, roots, and soil, and aboveground biomass and litter productivity. We used structural equation models to evaluate how macroclimate, soil nutrients (N, P), and forest attributes (structure, diversity, and functional composition) affect ecosystem functioning. After three years of succession, tropical wet forests stored on average 115 t biomass ha-1 (the sum of aboveground living and dead biomass, belowground fine root biomass, and soil organic matter), and dry forests stored 99 t ha-1. These values represent 31% (in the wet forest) and 39% (in the dry forest) of the biomass compared with neighboring old-growth forests. The majority of forest ecosystem biomass was stored in the soil (70%) and aboveground living vegetation (25%). Macroclimate strongly shaped forest attributes, which in turn determined biomass stocks and productivity. Soil phosphorus strongly increased litter production and soil organic matter, confirming that it is a limiting element in tropical ecosystems. Tree density and species diversity increased forest biomass stocks, suggesting crown packing and complementary resource use enhance forest functioning. A more conservative trait composition (high wood density) increased biomass stocks but reduced productivity, indicating that quantity, identity, and quality of species affect ecosystem functioning.

Multi-scale forest heterogeneity promotes occupancy of dusky-footed woodrats in the Sierra Nevada

Forested landscapes are naturally heterogeneous, with the distribution of resources influencing animal habitat selection at multiple spatial scales. However, anthropogenic activities and changing disturbance regimes have reorganized how forests are structured from fine- to landscape-scales, generally with unknown consequences for forest-associated wildlife. For instance, fire suppression and selective logging in the western US has led to more homogeneous forests with fewer small patches of early-successional vegetation. As forest management aims to improve forest resilience to extreme fire and drought by restoring historical disturbance regimes and modifying forest structure through fuel management, there is a need for studies that evaluate how animals respond to forest heterogeneity at multiple scales. Here, we estimated occupancy for the dusky-footed woodrat (Neotoma fuscipes), an important prey species for many forest predators including the California spotted owl (Strix occidentalis occidentalis), relative to forest structure and composition at site-, patch-, and landscape-scales within landscapes where forest heterogeneity was created by even-aged timber management. Woodrats were more likely to occupy sites with greater canopy cover, understory cover, and hardwoods – particularly tanoak (Notholithocarpus densiflorus) – and smaller patches of young forest. Woodrats were also more likely to occupy mature forests in close proximity to younger forests, suggesting that young forest patches with more favorable local conditions can produce populations that recruit into adjacent, lower-quality mature forests. Our results suggest that creating small (∼2 ha) patches of high-quality woodrat habitat (i.e., young forests with dense understory and hardwoods) could provide “fishing holes” for spotted owls and other predators by supporting higher woodrat densities in surrounding mature forests managed for fuels – thus helping to meet both spotted owl conservation and forest resilience objectives. More broadly, we highlight the benefits of multi-scale studies and demonstrate that restoring landscape heterogeneity, including the creation of small early-successional forests, may benefit species conservation without compromising efforts to improve resilience in forest ecosystems globally.

Integrated multi-satellite data and machine learning approach in mapping the successional stages of forest types in a tropical montane forest

Understanding the successional stages in tropical montane forests (TMF) is crucial for its conservation and management. This study integrated Sentinel-1, Sentinel-2, InSAR, GEDI, and machine learning to map the categorical successional stages of different forest types in a Philippines’ TMF. Field data collected from December 2022 to January 2023 were used to create and validate successional stages models. Sentinel-1 interferogram, unwrapped interferogram, and coherence exhibited moderate positive correlations with canopy height (r = 0.43). Incorporating GEDI with InSAR to predict canopy height yielded less accurate predictions (r = −0.20 to 0.04; RMSE = 12–13 m). Results show that canopy height, a widely accepted attribute for forest structure, appears secondary to other biophysical variables. Integrating optical, radar, and auxiliary variables achieved an overall accuracy of 79.56% and a kappa value of 75.74%. Feature importance analysis using Random Forest enhanced the overall accuracy (84.22%) and kappa value (81.19%). The integration of multi-satellite data with machine learning has proven effective for studying TMFs successional stages. Elevation emerged as the most significant predictor of forest type distribution, with mature and young pine forests dominating lower elevation (700–1,400m) and mossy forests dominating above 1,400m. Given the observed disturbances, the study underscores the need for robust conservation strategies and sustainable TMF management. Future research should focus on time-series analyses of successional stages, further optimization of machine learning models, and integrating additional data sources, such as LiDAR, to enhance canopy height predictions and forest monitoring efforts. The findings also provide valuable knowledge applicable to TMFs globally, supporting informed conservation and policies intended to protect biodiversity.

Assessment of soil CO2, CH4, and N2O fluxes and their drivers, and their contribution to the climate change mitigation potential of forest soils in the Lublin region of Poland

AbstractForests can play a key role in the mitigation of climate change, although there have been limited regional scale assessments that account for variations in soil type and tree species. Most of the focus has been on their ability to sequester atmospheric CO2, while there is less information on the two other major greenhouse gases (GHGs), N2O and CH4. We examined the GHG budgets of ten forest soils in Poland, considering all three major GHGs, where no previous long-term measurements had been made, which encompassed different tree species, stand age, and contrasting edaphic conditions. In addition to the quantification and assessment of seasonal variability in the major soil GHG fluxes over two years, the aims of the present study were (i) the identification of the main drivers of the soil-based GHG fluxes, (ii) the determination of the contribution of each gas to the Global Warming Potential (GWP), and (iii) to assess the mitigation potential of these fluxes over different forest systems. All the forest soils were sources of CO2 and N2O and sinks for atmospheric CH4 with pronounced seasonal variations in CO2 and CH4 driven by soil moisture and temperature. The soils showed significant differences in annual GHG fluxes, with average values of 16.7 Mg CO2 ha−1, − 3.51 kg CH4 ha−1, and 0.95 kg N2O ha−1. The annual total GWP ranged from 13.1 to 22.0 Mg CO2 eq ha−1 with CO2 making the highest contribution, and forest-specific CH4 uptake resulting in a reduction in GWP, ranging from − 0.08% (in the youngest forest) to -0.97% (in the oldest forest). Mixed forests showed the greatest potential for climate change mitigation, with the highest soil C sequestration, and the lowest GWP values when compared to sites with monocultures. The results suggest that a mixture of tree species could eventually be incorporated into management plans to increase the effectiveness of forests in climate change mitigation.

Sensitivity of gross primary production and evapotranspiration to heat and drought stress in a young temperate plantation in northern China

Assessing the sensitivities of ecosystem functions to climatic factors is essential to understanding the response of ecosystems to environmental change. Temperate plantation forests contribute to global greening and climate change mitigation, yet little is known as to the sensitivity of gross primary production (GPP) and evapotranspiration (ET) of these forests to heat and drought stress. Based on near-continuous, eddy-covariance and hydrometeorological data from a young temperate plantation forest in Beijing, China (2012–2019), we used a sliding-window-fitting technique to assess the seasonal and interannual variation in ecosystem sensitivity (i.e., calculated slopes, SGPP-Ta, SET-Ta, SGPP-EF, and SET-EF) in GPP and ET to anomalies in air temperature (Ta) and evaporative fraction (EF). The EF was used here as an indicator of drought. Seasonally, daily SGPP-Ta, SET-Ta, and SGPP-EF were greatest in summer, reaching maxima of 1.12 ​± ​0.56 ​g ​C·m−2·d−1⋅°C−1, 1.36 ​± ​0.56 ​g H2O·m−2·d−1⋅°C−1, and 0.37 ​± ​0.35 ​g ​C·m−2·d−1, respectively. Evapotranspiration was constrained by drought, especially during the spring-to-summer period, SET-EF reaching −0.51 ​± ​0.34 ​g H2O·m−2·d−1. Variables EF, Ta, soil water content (SWC), vapor pressure deficit (VPD), and precipitation (PPT) were the main controls of sensitivity, with SGPP-Ta and SET-Ta increasing with Ta, VPD, and PPT (<50 ​mm·d−1) during both spring and autumn. Increased drought stress during summer caused the positive response in GPP and ET to decrease with atmospheric warming. Variable SET-EF intensified (i.e., became more negative) with decreasing EF and increasing Ta. Interannually, annual SGPP-Ta and SET-Ta were positive, SGPP-EF near-neutral, and SET-EF negative. Interannual variability in SGPP-Ta, SET-Ta, SET-EF, and SGPP-EF was largely due to variations in bulk surface conductance. Our study suggests that the dynamics associated with the sensitivity of ecosystems to changes in climatic factors need to be considered in the management of plantation forests under future global climate change.