Search Results (207)

Alpine forests are key regulators of soil biogeochemical cycles, yet the extent to which forest type constrains soil microbial diversity and soil quality in high-elevation regions remains insufficiently resolved. Here, we assessed how contrasting alpine forest types influence the taxonomic composition and diversity of soil microbial communities, identified the dominant environmental drivers, and evaluated soil quality along the southern slope of the Qilian Mountains. Six forest types were examined, including four monospecific stands (Picea crassifolia, QQ; Betula spp., HS; Juniperus przewalskii, YB; and Pinus tabuliformis, YS) and two mixed formations (mixed conifer–broadleaf, ZKHJ; and mixed broadleaved, KKHJ). Bacterial and fungal communities were characterized using Illumina high-throughput sequencing, while structural equation modeling (SEM) was used to identify primary drivers of diversity and principal component analysis (PCA) was applied to construct the minimum data set (MDS) for soil quality evaluation. Mixed forests consistently exhibited higher bacterial and fungal alpha diversity than pure stands. Environmental gradients were the strongest positive drivers of microbial diversity, whereas soil chemical properties and vegetation-related biotic factors exerted partially negative effects. Soil quality index (SQI) values ranked as follows: KKHJ (0.55) > ZKHJ (0.49) > YB (0.48) > HS (0.46) > YS (0.44) > QQ (0.43). The mixed broadleaved forest reached Grade IV (upper-intermediate level) soil quality, whereas the other forest types were classified as Grade III (intermediate). Mixed forests showed stronger capacities for organic matter accumulation and nutrient retention. These findings indicate that promoting mixed forest stands is critical for improving soil structure, nutrient retention, and microbial diversity in this alpine region. Accordingly, forest management should prioritize the development of mixed forests to enhance overall soil quality. Full article

We surveyed bee communities across an organic conifer tree farm landscape in northern Idaho to assess how managed forest–agriculture mosaics support pollinator diversity. Bees were collected from farm fields, adjacent conservation forests, and a pollinator garden between May and August 2024 using aerial nets and identified to species or morphospecies. In total, 94 bee species were recorded, representing a mix of ground-nesting (46%), cavity-nesting (37%), and social (17%) taxa. Bee richness was highest in farm fields (66 species), intermediate in forests (48 species), and lowest in the pollinator garden (35 species). Community turnover among habitats was substantial (Jaccard dissimilarity = 0.67–0.76; Bray-Curtis dissimilarity = 0.53–0.55), indicating distinct assemblages associated with each habitat type. Comparisons with regional datasets from Montana and Washington revealed moderate overlap (Jaccard = 0.22–0.24), suggesting that the Highland Flats farm supports a partly unique bee fauna within the Northern Rockies. Seven non-native bee species and nine species of conservation concern (five Osmia, four Bombus) were detected, with those of conservation concern taxa often visiting native Lupinus flowers. Most bee visits occurred on non-native plants, though native blooms contributed key seasonal resources. These findings demonstrate that organic tree farms with structurally diverse forests and managed floral resources can function as refugia for both common and at-risk bees in temperate forested landscapes. Full article

Broad-scale assessments often track forest productivity, yet they rarely quantify how soil conditions determine whether these gains persist as long-lived carbon and generate measurable economic value. This study focused on Northeast China, where forests include boreal coniferous stands dominated by Dahurian larch, temperate conifer–broadleaf mixed forests with Korean pine, and temperate deciduous broadleaf forests dominated by Mongolian oak. We combined GLASS net primary productivity and ESA CCI Land Cover to delineate forest pixels, used 2000 to 2005 as the baseline, and converted productivity anomalies into pixel level carbon economic value using a consistent pricing rule. Forest NPP increased significantly during 2000 to 2018 (slope = 1.57, p = 0.019), and carbon economic value also increased over time during 2006 to 2018 (slope = 2.24, p = 0.002), with the highest values in core mountain forests and lower values in the western forest–grassland transition zone. Correlation analysis, explainable random forests, and variance partitioning characterized spatial and temporal dynamics from 2000 to 2018 and identified environmental controls. Carbon value increased over time and showed marked spatial heterogeneity that mirrored productivity patterns in core mountain forests. Climate was the dominant predictor of value, while higher soil pH and clay content were negatively associated with value. The random forest model explained about 70% of the variance in carbon value (R² = 0.695), and variance partitioning indicated substantial unique and joint contributions from climate and soil alongside secondary topographic effects. The automatable framework enables periodic updates with new satellite composites, supports ecological compensation zoning, and informs soil-oriented interventions that enhance the monetized value of forest carbon sinks in data-limited regions. Full article

Northeast British Columbia (54–60° N latitude, 120–123° W longitude) has 10+ M ha of complex conifer–broadleaf forest, which is a unique forest type in the province. Current management practice is to remove competing broadleaf species to promote the growth of more commercially valued conifers. This approach ignores the species silvics and results in forest simplification, thus reducing species and structural diversity, habitat value, and overall stand resilience to future events such as climate change and wildfires. These practices also negatively impact traditional First Nation treaty rights. Three trials were established across the region in 5-to-18-year-old post-logging mixed species stands where broadleaves had not been removed. Competition-free radii of 0, 1, 2, and 4 m were established around white spruce (Picea glauca (Moench) Voss) crop trees. The objective was to investigate the impact of broadleaf (aspen Populus tremuloides Michx. or paper birch Betula papyrifera Marsh.) competition on crop tree growth with respect to the free-to-grow (FTG) standard. Except at extreme broadleaf densities (>10,000 SPH), crop tree DBH growth was not impacted when trials were established. After at least 11 growing seasons, except at the competition-free 4 m radius, DBH was not impacted by competition. Spruce DBH in the mixed stand at all radii was greater than the expected BC model projections for a pure spruce stand on these sites. Our findings suggest that the current FTG management approach in northeast BC only has a positive result if taken to an extreme. It has a low return on investment and reduces stand resilience and total productivity. An alternative forest management approach for the region is presented. Full article

Enhancing forest biodiversity and carbon sinks in the face of climate change is a high priority on the global agenda. The aim of our study was to explore the feasibility and potential of enhancing biodiversity and stand biomass productivity, which are strongly linked to forest ecosystem functioning and services in temperate forests. Based on data from the 5th to 7th National Forest Inventory of South Korea, 1760 natural forest plots (0.16 ha) were used, of which 344 plots belonged to conifer stands, 711 plots belonged to broadleaved stands, and 705 plots belonged to mixed stands. Forest succession-related factor (i.e., stand age), and abiotic (i.e., climatic and topographic conditions, and soil properties) and biotic drivers (i.e., species diversity, functional trait diversity, functional trait identity, and stand structural diversity) were jointly included as independent variables in an integrated model to explain variations in stand biomass productivity. In order to reveal the key drivers and relationships that regulate stand biomass productivity across forest stand types, we applied a multi-model averaging approach and piecewise structural equation modelling (pSEM). As a key finding, across all forest stand types, forest stand age-induced tree size inequality (i.e., DBH STD) in all forest stand types commonly increased stand biomass productivity, showing strong positive standardized effects (β > 0.5, p < 0.001). We also found that the functional trait identities controlling stand biomass productivity within each forest stand type differed according to their functional traits of dominant species, and that these mechanisms were controlled directly or indirectly by environmental conditions. Our research suggests that appropriate forest management plans should be developed in accordance with environmental gradients to simultaneously promote biodiversity and stand biomass productivity in different forest stand types. Full article

In Hanson (2022), I found that commercially thinned forests had significantly higher overall tree mortality, or cumulative severity, from the combination of pre-fire commercial thinning and the Antelope fire of 2021 in northern California. A comment on Hanson (2022) by Loehle (2025) does not dispute my central finding about cumulative severity but suggests that the findings might be limited to the Antelope fire, that differences in accuracy might exist between tree mortality estimates for thinning versus fire, and argues that there are other benefits from commercial thinning, such as financial gains for logging companies and reduced rate of fire spread in low-density forests. In this reply, I address these and other criticisms and explain why they do not affect my results or conclusions. Full article

Forest managers need regular accurate assessments of forest conditions to make informed decisions associated with harvest schedules, growth projections, merchandising, investment, and overall management planning. Traditionally, this is achieved through field-based sampling (i.e., timber cruising) a subset of the trees within a desired area (e.g., 1%–2%) through stratification of the landscape to group similar vegetation structures and apply a grid within each stratum where fixed- or variable-radius sample locations (i.e., plots) are installed to gather information used to estimate trees throughout the unmeasured remainder of the area. These traditional approaches are often limited in their assessment of uncertainty until trees are harvested and processed. However, the increasing availability of airborne laser scanning datasets in commercial forestry processed into Digital Inventories^® enables the ability to non-destructively assess the accuracy of these field-based surveys, which are commonly referred to as cruises. In this study, we assess the uncertainty of common field sampling-based estimation methods by comparing them to a population of individual trees developed using established and validated methods and in operational use on the University of Idaho Experimental Forest (UIEF) and a commercial conifer plantation in Louisiana, USA (PLLP). A series of repeated sampling experiments, representing over 90 million simulations, were conducted under industry-standard cruise specifications, and the resulting estimates are compared against the population values. The analysis reveals key limitations in current sampling approaches, highlighting biases and inefficiencies inherent in certain specifications. Specifically, methods applied to handle edge plots (i.e., measurements conducted on or near the boundary of a sampling stratum), and stratum delineation contributes most significantly to systematic bias in estimates of the mean and variance around the mean. The study also shows that conventional estimators, designed for perfectly randomized experiments, are highly sensitive to plot location strategies in field settings, leading to potential inaccurate estimations of BAA and TPA. Overall, the study highlights the challenges and limitations of traditional forest sampling and impacts specific sampling design decisions can have on the reliability of key statistical estimates. Full article

Semi-humid subtropical montane regions face the dual pressures of climate change and water scarcity, making it essential to understand how soil carbon–water coupling varies among forest types. Focusing on seven representative forest types in the central Yunnan Plateau, this study analyzes the spatial distribution, trade-offs, and drivers of soil organic carbon storage (SOCS) and soil water storage (SWS) within the 0–60 cm soil layer, using sloping rainfed farmland (SRF) as a reference. We hypothesize that, relative to SRF, both SOCS and SWS increase across forest types; however, the direction and strength of the SOCS–SWS trade-off differ among plant communities and are regulated by litter traits and soil structural properties. The results show that SOCS in all forest types exceeded that in SRF, whereas a significant increase in SWS occurred only in ACF. Broadleaf stands were particularly prominent: SOCS rose most in the 23 yr SF and the 20 yr ACF (274.44% and 256.48%, respectively), far exceeding the 9–60 yr P. yunnanensis stands (44.01%–105.32%). Carbon–water trade-offs varied by forest type and depth. In conifer stands, SWS gains outweighed SOCS and trade-off intensity increased with stand age (RMSD from 0.48 to 0.53). In broadleaf stands, SOCS gains were larger, with RMSD ranging from 0.21 to 0.45 and the weakest trade-off in SF. Across depths, SOCS gains exceeded SWS in 0–20 cm, whereas SWS gains dominated in 40–60 cm. Regression analyses indicated a significant negative SOCS–SWS relationship in conifer stands and a significant positive relationship in 0–20 cm soils (both p < 0.05), with no significant correlations in other forest types or depths (p > 0.05). Correlation results further suggest that organic matter inputs, N availability, and soil physical structure jointly regulate carbon–water trade-off intensity across forest types and soil depths. We therefore recommend prioritizing native zonal broadleaf species, as well as protecting SF and establishing mixed conifer–broadleaf stands, to achieve synergistic improvements in SOCS and SWS. Full article

Clarifying the role of density regulation in different stand types of Chinese fir (Cunninghamia lanceolata) is beneficial for sustainable management. Stand density management diagrams (SDMDs) can help in simulating thinning, regulating stand structure, and balancing timber yield. This study, conducted in Ganzhou City, a mid-subtropical region of China, used second-class forest resource survey plots dominated by Chinese fir, including 541 Chinese fir pure stands, 232 Chinese fir-conifer mixed stands, and 351 Chinese fir-broadleaf mixed stands. Equations for self-thinning, dominant height, and stand volume were constructed, and the SDMDs were subsequently developed to simulate two management scenarios: self-thinning and thinning. The results indicate that self-thinning relationships differ among Chinese fir stand types and that appropriate thinning can improve stand growth. Mixed stands, particularly Chinese fir–broadleaf mixed stands, showed greater growth potential at later stages, highlighting the role of species mixing in reducing competition and enhancing resource-use efficiency. The SDMDs developed in this study provide a practical tool for density regulation and silvicultural planning in Chinese fir plantations. However, being based on regional-scale growth models, the results mainly reflect regional conditions and should be further validated with long-term experiments. Full article

A sharp escalation in wildfire frequency, severity, and scale in the western United States calls for the creation of forests that are resilient in the future. One reforestation method involves clustering trees into groups of two to four, instead of creating evenly spaced plantations, in an effort to increase structural heterogeneity and emulate natural regeneration patterns. There have been a limited number of studies on clustered plantations, and this study addresses this important research gap. In Eldorado National Forest in the Sierra Nevada, we compared growth and structure in several post-fire plantations, treated with and without pre-commercial thinning (PCT), and naturally regenerating stands. Using mixed-effects models, we tested for growth and structural differences between evenly spaced and clustered plantations, as well as comparing them to stands of naturally regenerating trees. Our results indicated that diameter and height growth were generally better maintained in the plantations compared to under natural stand conditions. When considering plantation arrangement, the annual basal area increment (BAI) thinning index ([BAI after thinning − BAI before thinning]/BAI before thinning) was generally higher in evenly spaced plantations (1.03) compared to clustered plantations (0.79). While high plant diversity would be important eventually from an ecological perspective, our study suggests that during the initial phases of plantation development, lower shrub diversity could assist with plantation establishment and growth. The frequency of yellow pines was an important, positively associated factor affecting BAI and height growth, but primarily in the high-elevation region, which demonstrates a facilitative legacy effect of prior stand composition. Our study highlighted the important legacy effect of prior stand density on the growth of yellow pines, but primarily in the low-elevation region, and only when the two plantation groups were examined. The negative association suggests that a lower initial density of plantations promotes better BAI growth and height growth after PCT. These findings thus have broad implications for effective post-fire restoration of young plantations to help ensure their future resilience to both post-fire restoration and climate change adaptation and biotic (i.e., plant competition) stress factors. Full article

Global climate change is driving profound transformations in forest ecosystems, particularly in monsoon-influenced regions of the Pacific coast of Asia, such as the Sikhote-Alin Mountains. Long-lived conifer species, notably Korean pine (Pinus koraiensis Siebold & Zucc.), play a central ecological role in mixed broadleaf–coniferous forests of the region. We examined how the radial growth response of Korean pine to climatic variability changes with tree age and ontogenetic stage, using 191 increment cores from trees ranging from early virginile to old generative stages. We employed two approaches: (i) a stage-based analysis, constructing tree-ring chronologies for each ontogenetic stage; (ii) an individual-tree analysis, applying correlation and regression directly to individual ring-width series. Climate–growth relationships were assessed using monthly temperature, precipitation, and drought indices (PDSI, SPEI). For the stage-based approach, radial growth was positively correlated with the mean August temperature of the previous year (up to r = 0.61), minimum November temperature (up to r = 0.50), and summer drought indices (up to r = 0.57). Age-related trends in climate sensitivity, assessed from regression models under both approaches, were significant for 9 of the 18 monthly climate variables examined. For stage-specific chronologies, simple regressions across six ontogenetic stages described up to 98% of the variance, whereas cambial-age-based relationships were much weaker (R² = 0.03–0.14). These findings highlight the importance of accounting for ontogenetic structure in dendroclimatic analyses and climate reconstructions. Such insights are critical for understanding long-term forest dynamics and informing climate adaptation strategies in Korean pine-dominated ecosystems. Full article

Urban trees play a crucial role in regulating hydrological processes within urban ecosystems by intercepting rainfall to effectively reduce surface runoff and mitigate urban flooding. Current research lacks a systematic quantification of rainfall interception capacity and its community-level impacts at the urban scale. This study adopts a city-scale perspective, integrating field survey data with the i-Tree Eco model to systematically explore the contributions of 20 factors to the average annual rainfall interception of tree species and the average annual rainfall interception efficiency of communities. The study revealed that Deciduous broadleaf trees (1.28 m³ year⁻¹) and Pure coniferous forests (90.7 mm year⁻¹) exhibited substantial rainfall interception capacity. Relative Height, Average Tree Height, Average Crown Width, and Planting Density of trees significantly influence interception capacity. Urban planning can optimize the selection of tree species (e.g., Paulownia, Populus tomentosa, etc.) and community structure (e.g., mixed planting of conifers and deciduous broadleaf trees) to improve rainfall interception capacity, thereby effectively reducing stormwater runoff, mitigating the risk of urban flooding. These findings provide a scientific basis for designing urban vegetation to mitigate flooding, support water management, and advance sponge city development. Full article

Longleaf pine forests are economically important habitats that stabilize and enrich the soil and store carbon over long periods. When mixed with oaks, these forests provide an abundance of lichen habitats. The tree canopy lichens promote greater moisture capture and retention and encourage canopy insects. Ground lichens limit some vascular plant germination and growth, promoting a more open and healthy pine community. There is a longstanding mutualistic relationship between longleaf pine habitat and lichens. Longleaf pine habitat has a long history of natural summer burning, which promotes a diverse understory and limits tree densities. Lichen diversity exceeds vascular plant diversity in many mature longleaf pine habitats, yet information on the impacts of prescribed fire on lichen species in these habitats is limited. We assessed lichen diversity and abundance before and after a prescribed ground fire in a longleaf pine/wiregrass habitat near Ocala, Florida. Pre-burn, we found greater lichen abundance and diversity on hardwoods, primarily oak species, than on pines. Post-burn, lichen abundance on hardwoods dropped overall by 28%. Lichen abundance on conifers dropped overall by 94%. Ground lichen species were basically eliminated, with a 99.5% loss. Our study provides insights into retaining lichen diversity after a prescribed burn. Hardwood trees, whether alive or standing dead, help retain lichen biodiversity after burning, whereas conifer trees do not support as many species. Landscapes may need to be actively managed by raking pine needle litter away from ground lichen beds, moistening the ground, or removing some lichen material before the burn and returning it to the site post-fire. Based on these results, we suggest retaining some oaks and conducting burns in a mosaic pattern that retains unburned areas. This will allow for lichens to recover between burns, significantly enhancing biodiversity and the ecological health of these longleaf pine communities. Full article

Converting monoculture forests into mixed forests is a widely adopted strategy to enhance forest ecosystem quality. Soil enzyme activities and their stoichiometric ratios are acknowledged as critical indicators of nutrient cycling and ecosystem multifunctionality, with microbial nutrient limitation (particularly C, N, and P) being strongly influenced by forest management practices. However, the effects of this conversion on soil enzyme activities and stoichiometric ratios remain inconclusive, and the impacts of forest conversion on soil C, N, and P dynamics require further clarification. To address these uncertainties, a meta-analysis of 2113 paired observations was conducted to assess the impacts of forest conversion on soil enzyme activities, stoichiometric ratios, and microbial nutrient limitations. The activities of four key enzymes, including β-1,4-glucosidase (BG), β-1,4-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and phosphatase (ACP) were examined. It was found that mixed forests exhibited significantly higher C-, N-, and P- enzyme activities than monocultures (increases of 36.23%, 9.85%, and 11.07%, respectively). Additionally, soil C, N, and P contents were generally enhanced following the conversion from monocultures to mixed forests. Elevated enzyme C:P and N:P ratios were observed in mixed forests, while C:N ratios were reduced. Microbial C limitation was alleviated, though C&P co-limitation remained prevalent. Notably, greater effects on enzyme activities were observed when conifer monocultures (particularly those introduced with broadleaf species) were converted, compared with conversions of broadleaf monocultures. In contrast, the introduction of additional conifer species into existing conifer stands exacerbated C limitation. These results suggest that conversion of monocultures to mixed-species forests can mitigate microbial C limitation in soils while improving soil nutrient availability. Furthermore, for conifer plantation conversion, selecting functionally complementary broadleaf species yields greater benefits than introducing additional conifer species. Full article

Bare land exposed by glacier retreat provides new opportunities for ecosystem development. Investigating primary vegetation succession in deglaciated regions can provide significant insights for ecological restoration, particularly for future climate change scenarios. Nonetheless, research on this topic in the Qinghai–Tibet Plateau has been exceedingly limited. This study aimed to investigate vegetation succession in the deglaciated area of the Zepu glacier during the Little Ice Age in southeastern Tibet. Quadrat surveys were performed on arboreal communities, and trends in vegetation change were assessed utilizing multi-year (1986–2024) remote sensing data. The findings indicate that vegetation succession in the Zepu glacier deglaciated area typically adheres to a sequence of bare land–shrub–tree, divided into four stages: (1) shrub (species include Larix griffithii Mast., Hippophae rhamnoides subsp. yunnanensis Rousi, Betula utilis D. Don, and Populus pseudoglauca C. Wang & P. Y. Fu); (2) broadleaf forest primarily dominated by Hippophae rhamnoides subsp. yunnanensis Rousi; (3) mixed coniferous–broadleaf forest with Hippophae rhamnoides subsp. yunnanensis Rousi and Populus pseudoglauca C. Wang & P. Y. Fu as the dominant species; and (4) mixed coniferous–broadleaf forest dominated by Picea likiangensis (Franch.) E. Pritz. Soil depth and NDVI both increase with succession. Species diversity is significantly higher in the third stage compared to other successional stages. In addition, soil moisture content is significantly greater in the broadleaf-dominated communities than in the conifer-dominated communities. An analysis of NDVI from 1986 to 2024 reveals an overall positive trend in vegetation recovery in the area, with 93% of the area showing significant vegetation increase. Temperature is the primary controlling factor for this recovery, showing a positive correlation with vegetation cover. The results indicate that Key ecological indicators—including species composition, diversity, NDVI, soil depth, and soil moisture content—exhibit stage-specific patterns, reflecting distinct phases of primary succession. These findings enhance our comprehension of vegetation succession in deglaciated areas and their influencing factors in deglaciated areas, providing theoretical support for vegetation restoration in climate change. Full article