Search Results (260)

Leaf loss caused by pest infestations poses a serious threat to forest health. The leaf loss rate (LLR) refers to the percentage of the overall tree-crown leaf loss per unit area and is an important indicator for evaluating forest health. Therefore, rapid and accurate acquisition of the LLR via remote sensing monitoring is crucial. This study is based on drone hyperspectral and LiDAR data as well as ground survey data, calculating hyperspectral indices (HSI), multispectral indices (MSI), and LiDAR indices (LI). It employs Savitzky–Golay (S–G) smoothing with different window sizes (W) and polynomial orders (P) combined with recursive feature elimination (RFE) to select sensitive features. Using Random Forest Regression (RFR) and Convolutional Neural Network Regression (CNNR) to construct a multidimensional (horizontal and vertical) estimation model for LLR, combined with LiDAR point cloud data, achieved a three-dimensional visualization of the leaf loss rate of trees. The results of the study showed: (1) The optimal combination of HSI and MSI was determined to be W11P3, and the LI was W5P2. (2) The optimal combination of the number of sensitive features extracted by the RFE algorithm was 13 HSI, 16 MSI, and hierarchical LI (2 in layer I, 9 in layer II, and 11 in layer III). (3) In terms of the horizontal estimation of the defoliation rate, the model performance index of the CNNR_HSI model (MPI = 0.9383) was significantly better than that of RFR_MSI (MPI = 0.8817), indicating that the continuous bands of hyperspectral could better monitor the subtle changes of LLR. (4) The I-CNNR_HSI+LI, II-CNNR_HSI+LI, and III-CNNR_HSI+LI vertical estimation models were constructed by combining the CNNR_HSI model with the best accuracy and the LI sensitive to different vertical levels, respectively, and their MPIs reached more than 0.8, indicating that the LLR estimation of different vertical levels had high accuracy. According to the model, the pixel-level LLR of the sample tree was estimated, and the three-dimensional display of the LLR for forest trees under the pest stress of larch caterpillars was generated, providing a high-precision research scheme for LLR estimation under pest stress. Full article

Investigating the effects of fire disturbance on soil microbial diversity and nitrogen cycling is crucial for understanding the mechanisms underlying soil nitrogen cycling. This study examined the fire burn site of the Larix gmelinii forest in the Greater Khingan Mountains, Inner Mongolia, to analyze the impact of varying fire intensities on soil nitrogen, microbial communities, and the abundance of nitrogen cycle-related functional genes after three years. The results indicated the following findings: (1) Soil bulk density increased significantly following severe fires (7.06%~10.84%, p < 0.05), whereas soil water content decreased with increasing fire intensity (6.62%~19.42%, p < 0.05). The soil total nitrogen and ammonium nitrogen levels declined after heavy fires but increased after mild fires; (2) Mild fire burning significantly increased soil bacterial diversity, while heavy fire had a lesser effect. Dominant bacterial groups included Xanthobacteraceae, norank_o_norank_c_AD3, and norank_o_Elsterales. Norank_o_norank_c_AD3 abundance decreased with burn intensity (7.90% unburned, 3.02% mild fire, 2.70% heavy fire). Conversely, norank_o_Elsterales increased with burning (1.23% unburned, 5.66% mild fire, 5.48% heavy fire); (3) The abundance of nitrogen-fixing nifH functional genes decreased with increasing fire intensity, whereas nitrification functional genes amoA-AOA and amoA-AOB exhibited the opposite trend. Light-intensity fires increased the abundance of denitrification functional genes nirK, nirS, and nosZ, while heavy fires reduced their abundance; (4) The correlation analysis demonstrated a strong association between soil bacteria and denitrification functional genes nifH and amoA-AOA, with soil total nitrogen being a key factor influencing the nitrogen cycle-related functional genes. The primary bacterial groups involved in soil nitrogen cycling were Proteobacteria, Actinobacteria, and Chloroflexi. These findings play a critical role in promoting vegetation regeneration and rapid ecosystem restoration in fire-affected areas. Full article

Differences in environmental conditions due to slope topography result in differences in evapotranspiration along slopes, but it is unclear how changes in environmental conditions affect the variations in evapotranspiration along slopes. Therefore, we monitored dry-day evapotranspiration (ET_d), solar radiation, vapor pressure deficit (VPD), and soil moisture downslope and upslope on a larch plantation hillslope from July to September 2023 to reveal the mechanisms driving ET_d variations. The results revealed that the difference in ET_d values between the downslope and upslope positions varied by month, with comparable ET_d values at both positions in July and higher ET_d values at the downslope position than at the upslope position in August and September. An ET_d model combining the effects of solar radiation, VPD, and soil water content was developed, which explained 68% of the variation in ET_d. The contributions of solar radiation, VPD, soil moisture, and their interactions to ET_d varied across slope positions, and ET_d was limited mainly by solar radiation downslope and by soil moisture upslope. Our study improves the understanding of the mechanisms governing the variations in evapotranspiration along slopes, and provides a new methodology for quantifying the effects of environmental differences between slope positions on evapotranspiration. Full article

This study developed diameter distribution models using the Weibull function for Korean red pine (Pinus densiflora), Korean white pine (P. koraiensis), and Japanese larch (Larix kaempferi). The study data were collected from 49 Korean red pine stands, 54 Korean white pine stands, and 49 Japanese larch stands located in national forests in Gangwon and North Gyeongsang Provinces, South Korea. To identify the optimal method for modeling the diameter distribution of these three species, parameter recovery methods and parameter prediction methods were analyzed. To identify the optimal parameter recovery method for presenting the diameter distribution of these three species, ten parameter recovery methods were compared using moment-based, percentile-based, and hybrid approaches. For parameter prediction methods, major stand characteristics were used as independent variables to develop the models for the parameters a, b, and c of the Weibull function. For estimating the Weibull parameters, two methods—the estimated parameter recovery method and the parameter prediction method—were compared and analyzed. The optimal parameter recovery method was the one using the minimum DBH, the mean DBH, and the DBH variance. The coefficient of determination (R²) for the models predicting the minimum DBH, the mean DBH, and the DBH variance ranged from 0.7186 to 0.9747, and the R² for the models directly predicting parameters ranged from 0.7032 to 0.9374, indicating high explanatory power and unbiased results. When comparing the two methods, the parameter prediction method showed higher accuracy and lower bias. In addition, paired t-tests were conducted to assess differences from the observed Weibull parameters. The results showed a significant difference for the estimated parameter recovery method, whereas no significant difference was found for the parameter prediction method, further supporting its reliability. Full article

Soil microorganisms are crucial in global biogeochemical cycles, impacting ecosystems’ energy flows and material cycling. This study, via high-throughput sequencing in four forests—the original Larix gmelinii (Rupr.) Kuzen. forest (LG), the conifer–broad-leaved mixed Pinus sylvestris var. mongolica Litv. forest (PS), the original pure Betula platyphylla Sukaczev forest (BP), and the original pure Populus L. forest (PL) in Shuanghe National Nature Reserve, Daxing’anling mountains—explored soil microbial community structures and diversities. The results indicated that the BP and PL forests had the lowest soil bacterial ACE and Chao1 indices, and the original pure birch forest’s Shannon index was higher than that of the poplar forest. The soil’s fungal Chao1 index of the birch forest was higher than that of the larch forests. Bradyrhizobium and Roseiarcus were the dominant soil bacterial genera; the dominant soil fungal genera were Podila, Russula, and Sebacina. RDA and mantel analyses indicated that soil microbial community structures varied across forest types mainly because of the effective phosphorous and pH levels, soil’s total nitrogen level, and available phosphorus level. This study offers a scientific foundation for cold-temperate-forest ecosystem management regarding soil microbial diversity and community structural changes in different forest types. Full article

Xinjiang larch (Larix sibirica Ledeb.) is a keystone species in the Altay Mountains, playing a vital role in maintaining ecosystem stability. This study investigates how different soil preparation techniques (ring, strip, and burrow) influence seed germination and seedling establishment by mitigating apomictic allelopathy. Experimental plots were established using artificial seeding and natural seed dispersal at soil depths of 5 cm, 10 cm, and 15 cm. Seedling survival and development were monitored in June, July, and August 2023. The results demonstrated that sod removal significantly enhanced seed germination by reducing allelopathic inhibition, improving seed–soil contact, and increasing moisture retention. Among the techniques, the ring method yielded the highest rates of seedling establishment, particularly when artificial seeding was combined with natural seed dispersal. Although seedling numbers tended to increase with soil depth, the differences were not statistically significant. Temporal dynamics revealed a peak in seedling survival in July, followed by a subsequent decline. These findings highlight the critical role of optimized soil preparation techniques in promoting successful seedling development. The study offers practical guidance for ecological restoration and sustainable forest management in degraded larch ecosystems of the Altay Mountains. Full article

Larch shoot blight, caused by the fungus Neofusicoccum laricinum, threatens larch (Larix spp.) forests across northeastern China, jeopardizing both timber productivity and ecological stability. This study aimed to investigate the genomic diversity, population structure, and potential adaptive mechanisms of N. laricinum across contrasting climatic regions. To achieve this, we conducted whole-genome resequencing of 23 N. laricinum isolates collected from three major provinces—Heilongjiang, Inner Mongolia, and Jilin—that represent distinct climatic zones ranging from cold-temperate to relatively warmer regions. We identified ~219.1 K genetic variants, offering a detailed portrait of the pathogen’s genomic diversity. Population structure analyses, including principal component analysis and phylogenetic tree, revealed clear genetic differentiation aligning with geographic origin and climate. Functional annotation (GO and KEGG) highlighted enrichment in metabolic, stress-response, and membrane transport pathways, suggesting potential adaptation to varied temperature regimes and environmental pressures. Moreover, region-specific variants—particularly missense and stop-gain mutations—were linked to genes involved in ATP binding, oxidoreductase activity, and cell division, underscoring the fungus’s capacity for rapid adaptation. Collectively, these findings fill a critical gap in the population genetics of N. laricinum and lay a foundation for future disease management strategies to larch shoot blight under changing climatic conditions. Full article

This study aimed to understand the difference in forest transpiration (T) between slope positions and to separate the contributions of main influencing factors to improve the accuracy of forest transpiration estimation at the slope scale by up-scaling the results measured at the plot scale, especially in semiarid regions with significant soil moisture differences along slope positions. Two plots of larch plantation were established, one at the lower position and another at the upper position of a northwest-facing slope in the semiarid area of the Liupan Mountains in northwest China. The sap flow velocity ($J_S$, mL·cm⁻²·min⁻¹) of sample trees, meteorological parameters in the open field, and soil water potential in the main root zone (0–60 cm) were monitored simultaneously in the growing season (from July to September) of 2015. However, only the transpiration data of 59 selected effective days were used, after excluding the days with rainfall and missing data. Based on the relative sap flow velocity (the ratio of instantaneous sap flow velocity to its daily peak value), the impacts of terrain shading and soil water potential on sap flow velocity at varying slope positions were quantitatively disentangled. The reduction in $J_S$ at the lower slope plot, attributed to terrain shading, exhibited a positive linear correlation with solar radiation intensity. Conversely, the $J_S$ reduction at the upper slope plot demonstrated a quadratic functional relationship with the differential in soil water potential between the two plots. Subsequently, employing the relationship whereby transpiration is equivalent to the product of sap flow velocity and sapwood area, we conducted a quantitative analysis of the contributions of soil water potential, sapwood area, terrain shading, and their interaction to the disparity in transpiration between the two slope positions. The total transpiration of the 59 effective days was 41.91 mm at the lower slope plot, slightly higher than that at the upper slope plot (37.38 mm), indicating a small difference (4.53 mm) due to the offsetting effects of multiple factors. When taking the upper slope plot as a reference, the plot difference in soil water potential increased the total transpiration for the 59 days at the lower slope plot by 16.40 mm, while the differences in sapwood area and terrain shading and the interaction of the three factors decreased the total transpiration at the lower slope plot by 6.61, 2.86, and 2.40 mm, respectively, making a net increase of 4.53 mm. Based on the pilot study under given conditions of location, soil, climate, and vegetation, the contributions of the influencing factors to the stand transpiration differences between the upper and lower slopes are as follows: soil moisture (soil water potential) > stand structure (sapwood area) > solar radiation (terrain shading) > interaction of all factors. All these impacts should be considered for the accurate prediction of forest transpiration at the slope scale through up-scaling from measurement at the plot scale, especially in semiarid regions. Full article

Forests can simultaneously provide a variety of ecosystem functions and services (ecosystem multifunctionality, EMF). Different stand types, influenced by biotic and abiotic factors, play a key role in determining EMF. To clarify the impact of stand type, as well as biotic and abiotic factors, on EMF, this study quantified EMF across three stand types: Betula platyphylla pure forest (BP), B. platyphylla–Larix principis-rupprechtii mixed forest (BL), and L. principis-rupprechtii pure forest (LP). The multiple-threshold approach was employed to quantify EMF, while structural equation modeling was used to analyze the primary factors influencing EMF. The results indicated the following: (1) BL had higher stand productivity than both BP and LP; (2) BL exhibited significantly higher functional diversity and soil fertility maintenance compared to LP, with no significant difference between BP and BL; (3) BP demonstrated a significantly stronger nutrient cycling function than LP, with no significant difference between LP and BL; (4) the ranking of EMF at all threshold levels was BL > BP > LP; (5) soil was an effective driver of EMF across all threshold levels; and (6) both the niche complementarity effect and the mass ratio effect jointly drove EMF at the low threshold (<50%), with the influence of both effects diminishing as the threshold increased. This study enhances our understanding of the key drivers of EMF in forest ecosystems and provides valuable insights for informing multifunctional forest management practices. Full article

Epiphytic lichens are integral to boreal forest ecosystems, yet their allelopathic interactions with host trees, particularly in cryolithozone regions, remain poorly understood. This study elucidates the physiological and biochemical impacts of the epiphytic lichen Physcia alnophila on Larix gmelinii (Gmelin larch), a keystone species in Siberian permafrost forests. By combining dendrochronology, GC–MS metabolomic analysis, and HPLC–ESI–MS/MS analysis, we demonstrate that the lichen’s primary metabolite, atranorin (ATR), systemically migrates from thalli into the host’s cambium, roots, and needles, with root accumulation reaching 36.3 µg g⁻¹ DW. Lichen-colonized trees exhibited severe radial growth inhibition (27%–51% reduction over five years) and suppressed apical growth, despite comparable heights to controls, indicating chronic phytotoxicity. Metabolomic profiling revealed lichen-specific polyols (e.g., arabitol, mannitol) in larch tissues, alongside elevated stress biomarkers (terpenes, sterols, phenolic acids), and significant disruptions to the tricarboxylic acid cycle and oxidative phosphorylation. These metabolic perturbations correlate with reduced monosaccharide availability and impaired energy production, directly linking ATR translocation to growth suppression. L. gmelinii exhibited compensatory responses, including increased fatty acids and arabinogalactan synthesis, suggesting adaptive mechanisms to mitigate lichen-induced stress. Our findings suggest P. alnophila as a biotic stressor that affects tree physiology in extreme climates, with implications for boreal forest resilience. This work provides an insight to the rarely pointed out species interactions, which, when combined with climate change, may alter carbon cycling and forest dynamics in permafrost ecosystems. Full article

Larch dieback disease, caused by Neofusicoccum laricinum, severely affects forest health and productivity. To effectively curb the occurrence of this disease, a powder formulation of Bacillus amyloliquefaciens JL54 was developed through spray drying. The research commenced with the optimization of fermentation medium and culture conditions through statistical design, aiming to maximize both bacterial viability and antagonistic activity. The optimal medium included 12 g/L yeast extract, 11.8 g/L yeast powder, and 7.2 g/L magnesium sulfate. Optimal culture conditions included 30% loading volume, 1% inoculum, 37 °C incubation temperature, 31.8 h shaking time, and initial pH 6.4. Under these conditions, the viable count of strain JL54 reached 4.45 × 10⁹ cfu/mL, a 296.67-fold increase compared with the unoptimized system. To evaluate its practical applicability, field trials were conducted, showing a 54% control efficiency against larch dieback disease, significantly suppressing disease progression. Subsequently, the spray drying process was optimized with a 1:10 protective agent-to-water ratio, 100 °C inlet temperature, and 630 mL/h feed flow rate, achieving a 78.41% powder recovery rate. Collectively, this study demonstrates the potential of B. amyloliquefaciens JL54 as an effective biocontrol agent for managing larch dieback and supports its application in spray-dried formulations for forest disease control. Full article

The natural regeneration of Larix gmelinii plantations plays a pivotal role in rehabilitating ecosystem services in Northeast China’s degraded forests. However, mechanistic linkages between soil aggregate nutrient fluxes and fungal community assembly remain poorly constrained. Combining space-for-time substitution with particle-size fractionation and high-throughput sequencing, this study examined successional trajectories across regeneration in Langxiang National Nature Reserve to resolve nutrient–fungal interplay during long-term forest restructuring. The results demonstrated that microaggregates (<0.25 mm) functioned as nutrient protection reservoirs, exhibiting significantly higher total carbon (TC) and nitrogen (TN) contents and greater fungal diversity (p < 0.05). Both stand regeneration stage and aggregate size significantly influenced fungal community composition and structural organization (p < 0.05). Aggregate-mediated effects predominated in upper soil horizons, where fungal dominance progressively transitioned from Mortierellomycota to Ascomycota with increasing particle size. In contrast, lower soil layers exhibited regeneration-dependent dynamics: Basidiomycota abundance declined with L. gmelinii reduction, followed by partial recovery through mycorrhizal reestablishment in Pinus koraiensis broadleaf communities. Fungal co-occurrence networks displayed peak complexity during Juglans mandshurica germination (Node 50, Edge 345), with 64.6%positive correlations, indicating the critical period for functional synergy. Basidiomycota showed significant negative correlations with nutrients and major fungal phyla (R² = 0.89). This study confirms that natural vegetation regeneration reshapes belowground processes through litter inputs and mycorrhizal symbiosis, while microaggregate management enhances soil carbon sequestration. Near-natural plantation management should incorporate broadleaf species to preserve mycorrhizal diversity and amplify ecosystem services. These findings provide an essential soil ecological theoretical basis for sustainable plantation management in Northeast China. Full article

Carbon (C), nitrogen (N), and phosphorus (P) are vital nutrients in the soil, exerting a profound influence on the primary productivity of ecosystems. However, our understanding of how the understory influences soil nutrients and their stoichiometry remains limited, especially in cold-temperate forests where the understory plays a crucial role in mediating soil nutrient cycling. To elucidate the effect of understory vegetation on soil nutrients, three typical larch forests, namely Sphagnum–Bryum–Rhododendron tomentosum–Larix gmelinii forest (SLL), Rhododendron dauricum–Larix gmelinii forest (RL), and Rhododendron tomentosum–Larix gmelinii forest (LL), were selected in the typical cold-temperate region of northeast China to determine the soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) contents, and their stoichiometric characteristics in 0–100 cm soil depth. The results revealed the following: (1) Significant differences in soil nutrient and its stoichiometry existed among the three different forest types (p < 0.001), with the SLL displaying the highest mean SOC, TN, and TP contents, as well as soil C:N, C:P, and N:P ratios, whereas the RL exhibited the lowest values (p < 0.05). (2) Across the 0–100 cm soil profile, the soil nutrient content and stoichiometry showed decreasing trends with soil depth, with significant differences among the soil layers. (3) Variations in soil stoichiometry were significantly correlated with soil bulk density, pH, soil temperature, soil water content, total porosity, and capillary porosity (p < 0.05). This study underscores the necessity of further consideration of the impact of understory vegetation in future research on soil stoichiometry in forest ecosystems. Full article

The long-term spatial–temporal variation in shoot blight of larch in China has not yet been clearly defined, and the mechanisms behind its long-distance spread remain unknown. This study, based on the historical occurrence dataset of shoot blight of larch in China, used spatial statistical analysis to describe the spatial changes in the disease across five stages since 1973. Subsequently, the study utilized Geo Detector and Random Forest models to investigate the relationship between the spread and occurrence of shoot blight of larch and seven influencing factors. The results revealed the following: (1) The spread of shoot blight of larch in China exhibits significant directionality, with the affected regions distributed along a northeast–southwest axis, and the epicenter of the spread is shifting southwestward; (2) Shandong and Jilin provinces served as the initial introduction points for shoot blight of larch, with most infected counties in other provinces experiencing outbreaks between 1989 and 1996, accompanied by a noticeable spread to neighboring provinces; (3) the occurrence of shoot blight of larch demonstrates a significant positive spatial clustering effect, forming a monocentric “core–periphery” structure centered in Liaoning Province, where kernel density values decrease gradually outward from the core. Geo Detector identified “seedling planting area” as a potential spatial driving factor for the disease. These findings underscore the critical influence of the combined effects of human activities and natural factors in shaping the spatiotemporal distribution patterns of shoot blight of larch. Full article

Foresters and natural resource managers are increasingly exploring opportunities for the early detection of emerging forest health concerns. One of these emerging concerns is the eastern larch beetle (ELB, Dendroctonus simplex LeConte), a native insect of tamarack (Larix laricina (Du Roi) K., Koch). Historically, the ELB attacked only dead or dying trees, but with climate change, it is now becoming a damaging disturbance agent that affects healthy trees as well. This shift creates a need to evaluate the methods used to detect and quantify the impacted areas. In northern Wisconsin, USA, 50 tamarack stands or aerial detection polygons were surveyed in the field during the 2023 growing season to explore different detection tools for ELBs. We visited 20 polygons identified by aerial sketch map surveys as having ELB mortality, 20 tamarack stands identified by the Astrape satellite imagery algorithm as disturbed, and 10 randomly selected stands from the Wisconsin forest inventory database (WisFIRs) for landscape-level context. For each of the detection methods and the Random stands, information on species composition, mortality, signs of ELB, invasive species, and water presence was quantified. ELBs were common across the landscape, but were not always associated with high levels of mortality. While overstory tree mortality was frequently observed in both aerial sketch map surveys and Astrape, it was not always linked to tamarack mortality. Current methods of detection may need to be re-evaluated in this environment. Tamarack stands in northern Wisconsin were highly heterogeneous in species, which is likely contributing to the difficulties in identifying both tamarack mortality and tamarack mortality specifically caused by ELBs across the two detection methods. Given the evolving impacts of climate change and the shifting dynamics between forests and insects, it is essential to evaluate and innovate detection methods to manage these ecosystems effectively. Full article