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Ecological stoichiometry plays an important role in revealing the mechanisms underlying biogeochemical cycles and ecosystem functions. Abiotic factors have strong effects on N-P stoichiometry, yet the impact of plant community structure, especially in forests, has not been fully elucidated. We investigated 68 plots in larch forests in northern China to explore how plant community structure and environmental factors affect the N-P stoichiometry of soil and leaves. The results showed significant differences in soil and leaf N-P stoichiometry among the three larch forests, P concentration and N:P ratio of leaves were significantly related to those of soil. Except for larch forest type, N-P stoichiometry was also regulated by elevation, climatic factors, and community structure. With increasing age (from 25 to 236 years), soil N and N:P ratio significantly increased, especially in the topsoil. With increasing mean DBH, leaf N concentration and N:P ratio also increased, indicating a shift in nutrient limitations with stand growth. These findings provide evidence that plant community structure and environmental factors regulate soil and leaf N-P stoichiometry, which is critically important for understanding biogeochemical cycles and forest management undergoing natural succession. [ABSTRACT FROM AUTHOR]

Beta-diversity reflects the spatial changes in community species composition which helps to understand how communities are assembled and biodiversity is formed and maintained. Larch (Larix) forests, which are coniferous forests widely distributed in the mountainous and plateau areas in North and Southwest China, are critical for maintaining the environmental conditions and species diversity. Few studies of larch forests have examined the beta-diversity and its constituent components (species turnover and nestedness-resultant components). Here, we used 483 larch forest plots to determine the total beta-diversity and its components in different life forms (i.e., tree, shrub, and herb) of larch forests in China and to evaluate the main drivers that underlie this beta-diversity. We found that total beta-diversity of larch forests was mainly dependent on the species turnover component. In all life forms, total beta-diversity and the species turnover component increased with increasing geographic, elevational, current climatic, and paleoclimatic distances. In contrast, the nestedness-resultant component decreased across these same distances. Geographic and environmental factors explained 20%–25% of total beta-diversity, 18%–27% of species turnover component, and 4%–16% of nestedness-resultant component. Larch forest types significantly affected total beta-diversity and species turnover component. Taken together, our results indicate that life forms affect beta-diversity patterns of larch forests in China, and that beta-diversity is driven by both niche differentiation and dispersal limitation. Our findings help to greatly understand the mechanisms of community assemblies of larch forests in China.

Abstract Background Panax ginseng cultivated under the forest is popular because its shape and effective ingredients are similar to wild ginseng. The growth of P. ginseng in the larch forest is generally better than in the broad-leaved forest, and the incidence rate of diseases is low. Therefore, the selection of forest species is one of the basic factors in the successful cropping of P. ginseng. Methods Illumina HiSeq high-throughput sequencing was used to analyze the 16S rRNA/ITS gene sequence of P. ginseng rhizosphere soil under larch forest to study the rhizosphere microbiome's diversity and community composition structure. Results The species classification and richness of rhizosphere bacterial and fungal communities in the same-aged P. ginseng were similar. Consistent with the soil system of commonly cultivated crops, Proteobacteria, Actinobacteriota, Acidobacteriota, Verrucomicrobiota, Chloroflexi, and Basidiomycota, Ascomycota were the dominant phylum of bacteria and fungi, respectively. Compared with the soil without planting P. ginseng, the diversity of microorganisms and community structure of continuous planting for 2 years, 5 years, and 18 years of P. ginseng rhizosphere soil had little change. The accumulation levels of Ilyonectria, Fusarium, Gibberella, and Cylindrocarpon were not significantly increased with planting P. ginseng and the increased age of cropping P. ginseng. Conclusions The results of this study showed that the soil function of the larch forest was good, which provided a theoretical basis for the land selection and soil improvement of cultivating P. ginseng under the larch forest.

Background: Panax ginseng cultivated under the forest is popular because its shape and effective ingredients are similar to wild ginseng. The growth of P. ginseng in the larch forest is generally better than in the broad-leaved forest, and the incidence rate of diseases is low. Therefore, the selection of forest species is one of the basic factors in the successful cropping of P. ginseng. Methods: Illumina HiSeq high-throughput sequencing was used to analyze the 16S rRNA/ITS gene sequence of P. ginseng rhizosphere soil under larch forest to study the rhizosphere microbiome's diversity and community composition structure. Results: The species classification and richness of rhizosphere bacterial and fungal communities in the same-aged P. ginseng were similar. Consistent with the soil system of commonly cultivated crops, Proteobacteria, Actinobacteriota, Acidobacteriota, Verrucomicrobiota, Chloroflexi, and Basidiomycota, Ascomycota were the dominant phylum of bacteria and fungi, respectively. Compared with the soil without planting P. ginseng, the diversity of microorganisms and community structure of continuous planting for 2 years, 5 years, and 18 years of P. ginseng rhizosphere soil had little change. The accumulation levels of Ilyonectria, Fusarium, Gibberella, and Cylindrocarpon were not significantly increased with planting P. ginseng and the increased age of cropping P. ginseng. Conclusions: The results of this study showed that the soil function of the larch forest was good, which provided a theoretical basis for the land selection and soil improvement of cultivating P. ginseng under the larch forest. [ABSTRACT FROM AUTHOR]

Larch forests are important for species diversity, as well as soil and water conservation in mountain regions. In this study, we determined large-scale patterns of species richness in larch forests and identified the factors that drive these patterns. We found that larch forest species richness was high in southern China and low in northern China, and that patterns of species richness along an elevational gradient depend on larch forest type. In addition, we found that patterns of species richness in larch forests are best explained by contemporary climatic factors. Specifically, mean annual temperature and annual potential evapotranspiration were the most important factors for species richness of tree and shrub layers, while mean temperature of the coldest quarter and anomaly of annual precipitation from the Last Glacial Maximum to the present were the most important for that of herb layer and the whole community. Community structural factors, especially stand density, are also associated with the species richness of larch forests. Our findings that species richness in China's larch forests is mainly affected by energy availability and cold conditions support the ambient energy hypothesis and the freezing tolerance hypothesis.

Introduction: Plant species composition in forest ecosystems can alter soil greenhouse gas (GHG) budgets by affecting soil properties and microbial communities. However, little attention has been paid to the forest types characterized by understory vegetation, especially in boreal forests where understory species contribute significantly to carbon and nitrogen cycling. Method: In the present study, soil GHG fluxes, soil properties and bacterial community, and soil environmental conditions were investigated among three types of larch forest [Rhododendron simsii-Larix gmelinii forest (RL), Ledum palustre-Larix gmelinii forest (LL), and Sphagnum-Bryum-Ledum palustre-Larix gmelinii forest (SLL)] in the typical boreal region of northeast China to explore whether the forest types characterized by different understory species can affect soil GHG fluxes. Results: The results showed that differences in understory species significantly affected soil GHG fluxes, properties, and bacterial composition among types of larch forest. Soil CO2 and N2O fluxes were significantly higher in LL (347.12 mg m-2 h-1 and 20.71 µg m-2 h-1) and RL (335.54 mg m-2 h-1 and 20.73 µg m-2 h-1) than that in SLL (295.58 mg m-2 h-1 and 17.65 µg m-2 h-1), while lower soil CH4 uptake (-21.07 µg m-2 h-1) were found in SLL than in RL (-35.21 µg m-2 h-1) and LL (-35.85 µg m-2 h-1). No significant differences between LL and RL were found in soil CO2, CH4, and N2O fluxes. Soil bacterial composition was mainly dominated by Proteobacteria, Actinobacteria, Acidobacteria, and Chloroflexi among the three types of larch forest, while their abundances differed significantly. Soil environmental variables, soil properties, bacterial composition, and their interactions significantly affected the variations in GHG fluxes with understory species. Specifically, structural equation modeling suggested that soil bacterial composition and temperature had direct close links with variations in soil GHG fluxes among types of larch forest. Moreover, soil NO3 --N and NH4 + - N content also affected soil CO2, CH4, and N2O fluxes indirectly, via their effects on soil bacterial composition. Discussion: Our study highlights the importance of understory species in regulating soil GHG fluxes in boreal forests, which furthers our understanding of the role of boreal forests in sustainable development and climate change mitigation. [ABSTRACT FROM AUTHOR]

Alterations in plant litter inputs into the soil are expected to significantly affect soil greenhouse gas (GHG) emissions. However, the influence on boreal forest soils is not clear, given the large amount of accumulated soil organic matter that may buffer the impacts from the input of fresh litter. In this study, we conducted a litter manipulation experiment to explore the effects of the litter layer on soil GHG fluxes in a Dahurian larch (Larix gmelinii) forest ecosystem in northeastern China. Three litter treatments were implemented, namely aboveground litter removal (LR), litter double (LD), and unchanged litter input (CK). The associated microclimate, litter characteristics, and soil properties were also measured. The results showed that this larch forest soil acts as a source of CO2 and N2O but acts as a sink for CH4 for all litter manipulation treatments. LD increased the soil CO2 and N2O fluxes by 15% and 34%, while LR decreased them by 8% and 21%, respectively. However, soil CH4 uptake decreased by 34% in LD treatment and increased by 22% in LR treatment, respectively. Litter manipulation treatments can not only affect soil GHG fluxes directly but also, via their effects on soil MBC, NH4+−N, and NO3−−N content, indirectly affect variations in soil CO2, CH4 and N2O fluxes, respectively. Our study highlights the importance of the plant litter layer in regulating soil GHG between the atmosphere and soil in a Dahurian larch forest ecosystem, especially for litter addition. Considering the natural increase in litter quantity over time, this important regulatory function is essential for an accurate estimation of the role of boreal forests in mitigating future climate change. [ABSTRACT FROM AUTHOR]

The seasonal and daily variability of sensible and latent heat and carbon dioxide (CO2) fluxes, as well as the sensitivity of the fluxes to changing environmental conditions were derived by the eddy covariance flux measurements in an undisturbed northern-taiga larch forest on continuous permafrost in Central Siberia from the end of May to the end of September in 2013 and 2015. The measurements showed a high seasonal and daily variability of CO2, sensible and latent heat fluxes. It was found that whereas dry and sunny weather conditions of June and July in 2013 and 2015 resulted in lower daily latent heat fluxes as compared to sensible ones, mostly cloudy and rainy weather in the second half of the summer led to the reduced net radiation and increased latent heat fluxes. The daily values of gross primary production from the beginning of June to mid-August in 2013 and 2015 exceeded the values of the ecosystem respiration, and the forest ecosystem was the sink of CO2 from the atmosphere. The maximum CO2 uptake was observed in late June and early July, primarily due to high photosynthesis rates influenced by high incoming solar radiation, optimal air temperature, and soil moisture conditions. Since mid-August, the balance between the CO2 uptake and release was close to zero. The total net ecosystem CO2 exchange during the growing season of 2013 was –76.5 g C/m2, while it was slightly higher (–103.6 g C/m2) during the growing season of 2015, primarily due to higher air temperatures in June and greater precipitation in the summer months of 2015. [ABSTRACT FROM AUTHOR]

It is of great significance to study short-term water-use efficiency (WUEs) at different canopy heights for accurately evaluating the adaptability of cold-temperate larch (Larix gmelinii) forest to climate change. The stable isotope method combining data of gradient meteorology, photosynthetic properties and leaf structure were used to assess the influence of different canopy heights on short-term water-use efficiency (WUEs) in larch forests in the northern Da Hinggan Mountains. The results show that: (1) The rank of leaf WUEs at different canopy heights was upper canopy > middle canopy > lower canopy. The leaf WUEs in upper canopy was significantly higher than those in the middle and lower canopy (p < 0.01), and no significant difference was found between the middle and lower canopy (p > 0.05). (2) The environmental factors, the photosynthetic characteristics, the specific leaf weight (LMA) and stomatal density (SD) had significant impact (p < 0.05) on leaf WUEs at different canopy heights of larch forest. (3) The results of the weighted random forest analysis show that the main factor affecting WUEs in larch forests at different canopy heights was vapor pressure deficit (VPD), followed by relative humidity (RH) and net photosynthetic rate (Pn), while LMA and SD made relatively small contributions. This indicates that the variation of leaf WUEs at different canopy heights is mainly due to environmental factors. Our results highlight that the difference of environmental factors at different canopy heights should be considered in the future study of leaf WUE. Our results contribute to a better understanding of water utilization strategies and carbohydrate relations in the boreal forest ecosystems, which is of great significance for improving the sustainable management measures and strategies of boreal forest resources. [ABSTRACT FROM AUTHOR]

Boreal forests cover over half of the global permafrost area and protect underlying permafrost. Boreal forest development, therefore, has an impact on permafrost evolution, especially under a warming climate. Forest disturbances and changing climate conditions cause vegetation shifts and potentially destabilize the carbon stored within the vegetation and permafrost. Disturbed permafrost‐forest ecosystems can develop into a dry or swampy bush‐ or grasslands, shift toward broadleaf‐ or evergreen needleleaf‐dominated forests, or recover to the pre‐disturbance state. An increase in the number and intensity of fires, as well as intensified logging activities, could lead to a partial or complete ecosystem and permafrost degradation. We study the impact of forest disturbances (logging, surface, and canopy fires) on the thermal and hydrological permafrost conditions and ecosystem resilience. We use a dynamic multilayer canopy‐permafrost model to simulate different scenarios at a study site in eastern Siberia. We implement expected mortality, defoliation, and ground surface changes and analyze the interplay between forest recovery and permafrost. We find that forest loss induces soil drying of up to 44%, leading to lower active layer thicknesses and abrupt or steady decline of a larch forest, depending on disturbance intensity. Only after surface fires, the most common disturbances, inducing low mortality rates, forests can recover and overpass pre‐disturbance leaf area index values. We find that the trajectory of larch forests after surface fires is dependent on the precipitation conditions in the years after the disturbance. Dryer years can drastically change the direction of the larch forest development within the studied period. Plain Language Summary: Boreal forests of eastern Siberia, cover more than half of the global permafrost area and insulate the underlying frozen ground. The development of the forest cover is important for the state and evolution of permafrost. Forest disturbances such as fires or droughts and climate change can cause changes in this ecosystem. Potentially such shifts can destabilize the carbon stored within the vegetation and permafrost. Disturbed permafrost‐forest ecosystems can develop into the dry or swampy bush‐ or grasslands, shift toward different forest types, or recover. An increase in the number and intensity of fires, as well as intensified logging, could lead to partial or complete permafrost degradation. We study the interactions between forest disturbances, permafrost, and forests. We use a forest‐permafrost model and simulate disturbances at a study site in eastern Siberia. We implement mortality, defoliation, and ground surface changes of different disturbances. We then analyze the forest recovery's impact on the permafrost underneath. We find that forest loss can cause soil drying and abrupt or steady decline of forests, depending on the intensity of the disturbance. Only after a surface fire, which has low mortality rates and is the most common disturbance, forests can successfully recover. Key Points: We demonstrate a dynamic forest‐permafrost model to investigate the interplay between boreal larch forest, permafrost, and disturbancesForest loss induces soil drying which leads to lower active layer thicknesses and abrupt or steady decline of larch forest coverTrajectory of larch forests after surface fires is dependent on the post‐disturbance precipitation conditions [ABSTRACT FROM AUTHOR]

The results are presented for a study of the radial growth dynamics and xylotomic structure along the trunk of healthy and stag-headed Dahurian larch trees (Larix gmelinii (Rupr.) Rupr.) growing in an evenly aged forest stand (64°19′23″ N, 100°13′28″ E) on permafrost on a north-facing slope. The annual ring widths, as well as the tracheid lumens and wall thickness were measured at 1/4, 1/2, and 3/4 of the trunk height and directly near the top for 25 intact and stag-headed trees. It was discovered that the aforementioned parameters demonstrate a negative gradient from root to top that was especially evident in stag-headed trees. The annual rings on the upper part of the trunk has undergone anatomic modifications over the last 20 years: disturbance of the tracheid rows and thinning of the walls of early- and late tracheids. It was found based on the climatic moving response functions of radial growth that the trees on north-facing slope suffer from a water deficit from the end of May until the twenties of June. The presence of both stag-headed and healthy trees on the north-facing slope can be explained by the high variation in the soil's hydrothermal properties due to the high degree of tessellation of the moss–lichen layer. With time, the sensitivity of certain trees to a water shortage can lead to drying of their tops. [ABSTRACT FROM AUTHOR]

Soil carbon (C) reservoirs held in forests play a significant role in the global C cycle. However, harvesting natural forests tend to lead to soil C loss, which can be countered by the establishment of plantations after clear cutting. Therefore, there is a need to determine how forest management can affect soil C sequestration. The management of stand density could provide an effective tool to control soil C sequestration, yet how stand density influences soil C remains an open question. To address this question, we investigated soil C storage in 8-year pure hybrid larch (Larix spp.) plantations with three densities (2000 trees ha−1, 3300 trees ha−1 and 4400 trees ha−1), established following the harvesting of secondary mixed natural forest. We found that soil C storage increased with higher tree density, which mainly correlated with increases of dissolved organic C as well as litter and root C input. In addition, soil respiration decreased with higher tree density during the most productive periods of warm and moist conditions. The reduced SOM decomposition suggested by lowered respiration was also corroborated with reduced levels of plant litter decomposition. The stimulated inputs and reduced exports of C from the forest floor resulted in a 40% higher soil C stock in high- compared to low-density forests within 8 years after plantation, providing effective advice for forest management to promote soil C sequestration in ecosystems. [ABSTRACT FROM AUTHOR]

Beta-diversity reflects the spatial changes in community species composition which helps to understand how communities are assembled and biodiversity is formed and maintained. Larch ( Larix ) forests, which are coniferous forests widely distributed in the mountainous and plateau areas in North and Southwest China, are critical for maintaining the environmental conditions and species diversity. Few studies of larch forests have examined the beta-diversity and its constituent components (species turnover and nestedness-resultant components). Here, we used 483 larch forest plots to determine the total beta-diversity and its components in different life forms (i.e., tree, shrub, and herb) of larch forests in China and to evaluate the main drivers that underlie this beta-diversity. We found that total beta-diversity of larch forests was mainly dependent on the species turnover component. In all life forms, total beta-diversity and the species turnover component increased with increasing geographic, elevational, current climatic, and paleoclimatic distances. In contrast, the nestedness-resultant component decreased across these same distances. Geographic and environmental factors explained 20%-25% of total beta-diversity, 18%-27% of species turnover component, and 4%-16% of nestedness-resultant component. Larch forest types significantly affected total beta-diversity and species turnover component. Taken together, our results indicate that life forms affect beta-diversity patterns of larch forests in China, and that beta-diversity is driven by both niche differentiation and dispersal limitation. Our findings help to greatly understand the mechanisms of community assemblies of larch forests in China., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 Kunming Institute of Botany, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.)

We constructed a bi-directional reflectance distribution function (BRDF) observation system on a 25-m-high tower surrounded by mature larch forests at the foot of Mt. Yatsugatake, central Japan. The BRDF feature (strong/weak reflections in a backward/forward scattering areas) is related closely to the 3D structure and biophysical parameters of forests. However, because of the difficulty of observations, observational BRDF data of mature forests are scarce, except for those of Boreal Ecosystem –Atmosphere Study (BOREAS). We made BRDF observations 10 times during 2007 to ascertain BRDF characteristics in each season. For comparison to these BRDF data, a semi-empirical BRDF model (Ross–thick Li–sparse kernel model) was introduced. This model can reproduce the BRDF data fairly well under identical solar conditions in each season. Then, seasonal changes of the vegetation structure and possible relations with BRDF were discussed. They are summarized as follows: (1) The forest BRDF changes distinctly and seasonally depending on the phenology. (2) The forest BRDF is influenced primarily by clarity of the geometrical profile on the forest surface, which is affected by shadow. However, the forest BRDF might be influenced by other factors such as the physiological characteristics of leaves and slight change of vegetation structure such as forest floor conditions and leaf angles during summer. (3) Features of forest BRDF must therefore appear during summer when the crown shape is distinctive. Furthermore, BRDF features appear distinctly as seasons progress, e.g., by autumn leaves and defoliation, when the unevenness of forests increases. These findings can promote monitoring of vegetation using multi-angular satellite observations. [ABSTRACT FROM AUTHOR]

To understand climate change’s effect on understory CO 2 flux components, we established automated chambers in a 56-year-old Japanese larch ( Larix kaempferi Sarg.) forest in central Japan for long-term continuous measurements. Between 2006 and 2013, annual CO 2 fluxes ranged from 7.0 to 8.4 tC ha −1 yr −1 for soil respiration ( R s ), 5.7–6.8 tC ha −1 yr −1 for heterotrophic respiration ( R h ), 9.3–10.7 tC ha −1 yr −1 for total understory respiration ( R u ), 2.6–3.5 tC ha −1 yr −1 for understory gross primary production (GPP u ), and 6.1–7.6 tC ha −1 yr −1 for net understory CO 2 exchange (NUE). Mean annual soil temperature (MAT s ), especially in spring, was positively related to annual R s , R h , R u , and NUE. Based on the inter-annual relationship between MAT s and annual understory CO 2 effluxes, a 1 °C MAT s increase was estimated to increase annual effluxes by 25.1% for R s and R h , 14.4% for R u , and 23.9% for NUE. The growing season CO 2 flux components were weakly associated with soil moisture. However, during a short dry period in the summer of 2013, we observed a strong relationship between soil moisture and understory R s , R h , and R u . GPP u was primarily controlled by the understory light intensity; GPP u during growing season increased where the canopy was disturbed by typhoons in the early growing seasons in 2007 (+9.8%) and 2012 (+24.4%) as well as during the 2013 growing season (+12.2%) due to a short drought. Understory CO 2 effluxes in this larch forest will likely increase under global warming. [ABSTRACT FROM AUTHOR]

A wildfire with many ignition points took place in the Daxing'an Mountains of north-east China in June 2010. After the fire, moss polsters and particle traps were collected from burnt and unburnt areas a few kilometres away from four ignition points. Charcoal extracted from the samples was divided into macroscopic charcoal >125 μm and microscopic charcoal <125 μm. Our results showed that the average amount of charcoal deposited in the burnt areas was statistically greater than the amount deposited in unburnt areas. The microscopic charcoal concentration inside the burnt areas rose as the size of the burnt area increased. However, the sampling points within the largest burnt area did not have the highest macroscopic charcoal concentration. We found that only limited amounts of charcoal were transported over a long distance and that the primary charcoal produced during or shortly after a fire event was much more abundant than the secondary charcoal produced during the non-fire period. This suggested that primary charcoal is the dominant signal in charcoal records, and that the charcoal Z-score values inside the burnt areas were clearly higher than the surroundings. Our observations indicate that multiple-size charcoal records may be a robust tool for reconstructing fire histories. [ABSTRACT FROM AUTHOR]

Remote sensing with time series data offers considerable potential in the trajectory of post forest fire dynamics beyond the current monitoring of structural attributes that are displayed in the post-fire area. Many studies have addressed this topic by using time series remote sensing indices; however, this approach has sometimes been demonstrated as an unrealistic and biased representation of the post-fire forest patterns due to the saturation issues of vegetation indices. These saturation issues then lead to an underestimation of the forest successional stages and an overestimation of the forest recovery rate. This paper aims to develop a framework for trajectory of the post-fire forest patterns in the Siberian boreal larch forest ( Larix sibirica ) with the synergistic use of different remote sensing based vegetation-cover indicators derived from the Landsat time series and the WorldView-2 images. A time-series of the forest recovery index (FRI) and fractional vegetation cover (FVC) has been analyzed to estimate the rates of forest regeneration and vegetation recovery across different burn severity levels in the Siberian larch forest. The results showed that the FRI method can be used to observe the regrowth of the larch forest from the tenth year after the fire overlapping with the period of significant increase in the sapling stem volume. The post-fire larch forest canopy can fully recover to the pre-fire condition with respect to the magnitude of the FRI values after 30–47 years where the highest regeneration rate was observed in the moderate burn severity areas followed by the low and high burn severity. On the other hand, the FVC method was positively correlated with burn severity and more sensitive for evaluating the early stages of the forest succession in which the FVC dramatically increases after 5–6 years after the fire. The significant growth of FVC was accentuated by the maximum emergence of the sapling density as well as the rapid growth of herbaceous plants, grasses, shrubs, and shade-intolerant trees immediately after the fire, which could not be evaluated using the FRI. Both time series of the FRI and the FVC are valuable tools for determining the dominant stages of the post-fire larch forest succession in order to understand the relationships between fire disturbance and natural cycles of the boreal larch forest. [ABSTRACT FROM AUTHOR]

Introduction: Plant species composition in forest ecosystems can alter soil greenhouse gas (GHG) budgets by affecting soil properties and microbial communities. However, little attention has been paid to the forest types characterized by understory vegetation, especially in boreal forests where understory species contribute significantly to carbon and nitrogen cycling., Method: In the present study, soil GHG fluxes, soil properties and bacterial community, and soil environmental conditions were investigated among three types of larch forest [ Rhododendron simsii - Larix gmelinii forest (RL), Ledum palustre - Larix gmelinii forest (LL), and Sphagnum-Bryum - Ledum palustre - Larix gmelinii forest (SLL)] in the typical boreal region of northeast China to explore whether the forest types characterized by different understory species can affect soil GHG fluxes., Results: The results showed that differences in understory species significantly affected soil GHG fluxes, properties, and bacterial composition among types of larch forest. Soil CO 2 and N 2 O fluxes were significantly higher in LL (347.12 mg m -2 h -1 and 20.71 μg m -2 h -1 ) and RL (335.54 mg m -2 h -1 and 20.73 μg m -2 h -1 ) than that in SLL (295.58 mg m -2 h -1 and 17.65 μg m -2 h -1 ), while lower soil CH 4 uptake (-21.07 μg m -2 h -1 ) were found in SLL than in RL (-35.21 μg m -2 h -1 ) and LL (-35.85 μg m -2 h -1 ). No significant differences between LL and RL were found in soil CO 2 , CH 4 , and N 2 O fluxes. Soil bacterial composition was mainly dominated by Proteobacteria, Actinobacteria, Acidobacteria, and Chloroflexi among the three types of larch forest, while their abundances differed significantly. Soil environmental variables, soil properties, bacterial composition, and their interactions significantly affected the variations in GHG fluxes with understory species. Specifically, structural equation modeling suggested that soil bacterial composition and temperature had direct close links with variations in soil GHG fluxes among types of larch forest. Moreover, soil NO 3 - -N and NH 4 +  - N content also affected soil CO 2 , CH 4 , and N 2 O fluxes indirectly, via their effects on soil bacterial composition., Discussion: Our study highlights the importance of understory species in regulating soil GHG fluxes in boreal forests, which furthers our understanding of the role of boreal forests in sustainable development and climate change mitigation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Duan, Xiao, Cai, Man, Ge, Gao and Mencuccini.)