Cold Temperate Forests Research Articles

Population Genetic Characteristics of Siberian Roe Deer in the Cold Temperate Forest Ecosystem of the Greater Khingan Mountains, Northeast China.

This study focuses on the Siberian roe deer population in the Greater Khingan Mountains, Northeast China. The cold temperate forest ecosystem in this area is distinctive. The Siberian roe deer is a crucial ecological indicator species, and its living conditions hold significant importance for ecological balance. From the winter of 2019 to 2022, 269 fecal samples of Siberian roe deer were collected from four protected areas in the northern part of the Greater Khingan Mountains, Heilongjiang Province. These samples were comprehensively analyzed using mitochondrial DNA and microsatellite markers, combined with conservation genetics evaluation methods. The results revealed that 244 individuals were identified in the fecal samples. The results of a Cyt b genetic analysis of the samples indicated that the haplotype and nucleotide diversity were 88.1% and 20.3%, respectively. The evaluation of 14 pairs of microsatellite loci showed that the average number of alleles was 11.2, and the average expected and observed heterozygosity were 0.672 and 0.506, respectively. Therefore, the overall genetic diversity level is high, but some populations of Siberian roe deer are at risk. AMOVA analysis and STRUCTURE Bayesian clustering confirmed the existence of obvious genetic differentiation among the populations. Historical studies have shown that the HZ and SH populations underwent the earliest diffusion events, and the BJC and SL populations also exhibited related signs (HZ: Huzhong Nature Reserve in the Greater Khingan Mountains; SH: Shuanghe National Nature Reserve in Heilongjiang Province; BJC: Heilongjiang Beijicun National Nature Reserve; SL: Songling District in Heilongjiang Province). Mismatch distribution and neutral tests indicated no expansion events or bottleneck effects in the population, and the inbreeding coefficient was positive, suggesting the possibility of inbreeding. The development potential of the population in the future varies among the various local populations. This study supports the biodiversity of Siberian roe deer at the genetic level to save the population and provides important scientific basis and reference for the protection and management of Siberian roe deer.

Methane concentration in the heartwood of living trees in a cold temperate mountain forest: variation, transport and emission.

Forest soils are the largest terrestrial sink of methane (CH4), but CH4 produced in tree trunks by methanogenic archaea and emitted into the atmosphere can significantly offset CH4 oxidation in the soil. However, our mechanistic understanding of CH4 accumulation in tree trunks, in relation to CH4 emission from the trunk surface, is still limited. We characterized temporal variations in the molar fraction of CH4 in the heartwood of trees ([CH4]HW) of four different species in a mountain forest and addressed the relationship between [CH4]HW and emission from the surface of the trunk (${F}_{CH_4}$), in connection with the characteristics of the wood. [CH4]HW measurements were made monthly for 15 months using gas-porous tubes permanently inserted into the trunk. [CH4]HW were above ambient CH4 molar fraction for all trees, lower than 100p.p.m. for seven trees, higher for the nine other trees and greater than 200,000p.p.m. (>20%) for two of these nine trees. [CH4]HW varied monthly but were not primarily determined by trunk temperature. Heartwood diffusive resistance for CH4 was variable between trees, not only due to heartwood characteristics but probably also related to source location. ${F}_{CH_4}$were weakly correlated with [CH4]HW measured a few days after. The resulting apparent diffusion coefficient was also variable between trees suggesting variations in the size and location of the CH4 production sites as well as resistance to gas transport within the trunk. Our results highlight the challenges that must be overcome before CH4 emissions can be simulated at the tree level.

Leaf stomatal configuration and photosynthetic traits jointly affect leaf water use efficiency in forests along climate gradients.

Water use efficiency (WUE) represents the trade-off between carbon assimilation and water loss in plants. It remains unclear how leaf stomatal and photosynthetic traits regulate the spatial variation of leaf WUE in different natural forest ecosystems. We investigated 43 broad-leaf tree species spanning from cold-temperate to tropical forests in China. We quantified leaf WUE using leaf δ13C and measured stomatal traits, photosynthetic traits as well as maximum stomatal conductance ( ) and maximum carboxylation capacity ( ). We found that leaves in cold-temperate forests displayed 'fast' carbon economics, characterized by higher leaf nitrogen, Chl, specific leaf area, and , as an adaptation to the shorter growing season. However, these leaves exhibited 'slow' hydraulic traits, with larger but fewer stomata and similar , resulting in higher leaf WUE. By contrast, leaves in tropical forests had smaller and denser stomata, enabling swift response to heterogeneous light conditions. However, this stomatal configuration increased potential water loss, and coupled with their low photosynthetic capacity, led to lower WUE. Our findings contribute to understanding how plant photosynthetic and stomatal traits regulate carbon-water trade-offs across climatic gradients, advancing our ability to predict the impacts of climate changes on forest carbon and water cycles.

Tracking Forest Disturbance in Northeast China’s Cold-Temperate Forests Using a Temporal Sequence of Landsat Data

Cold-temperate forests (CTFs) are not only an important source of wood but also provide significant carbon storage in China. However, under the increasing pressure of human activities and climate change, CTFs are experiencing severe disturbances, such as logging, fires, and pest infestations, leading to evident degradation trends. Though these disturbances impact both regional and global carbon budgets and their assessments, the disturbance patterns in CTFs in northern China remain poorly understood. In this paper, the Genhe forest area, which is a typical CTF region located in the Inner Mongolia Autonomous Region, Northeast China (with an area of about 2.001 × 104 km2), was selected as the study area. Based on Landsat historical archived data on the Google Earth Engine (GEE) platform, we used the continuous change detection and classification (CCDC) algorithm and considered seasonal features to detect forest disturbances over nearly 30 years. First, we created six inter-annual time series seasonal vegetation index datasets to map forest coverage using the maximum between-class variance algorithm (OTSU). Second, we used the CCDC algorithm to extract disturbance information. Finally, by using the ECMWF climate reanalysis dataset, MODIS C6, the snow phenology dataset, and forestry department records, we evaluated how disturbances relate to climate and human activities. The results showed that the disturbance map generated using summer (June–August) imagery and the enhanced vegetation index (EVI) had the highest overall accuracy (88%). Forests have been disturbed to the extent of 12.65% (2137.31 km2) over the last 30 years, and the disturbed area generally showed a trend toward reduction, especially after commercial logging activities were banned in 2015. However, there was an unusual increase in the number of disturbed areas in 2002 and 2003 due to large fires. The monitoring of potential widespread forest disturbance due to extreme drought and fire events in the context of climate change should be strengthened in the future, and preventive and salvage measures should be taken in a timely manner. Our results demonstrate that CTF disturbance can be robustly mapped by using the CCDC algorithm based on Landsat time series seasonal imagery in areas with complex meteorological conditions and spatial heterogeneity, which is essential for understanding forest change processes.

Comparative Analysis of Bacterial Community Structures in Earthworm Skin, Gut, and Habitat Soil across Typical Temperate Forests.

Earthworms are essential components in temperate forest ecosystems, yet the patterns of change in earthworm-associated microbial communities across different temperate forests remain unclear. This study employed high-throughput sequencing technology to compare bacterial community composition and structure in three earthworm-associated microhabitats (skin, gut, and habitat soil) across three typical temperate forests in China, and investigated the influence of environmental factors on these differential patterns. The results indicate that: (1) From warm temperate forests to cold temperate forests, the soil pH of the habitat decreased significantly. In contrast, the physicochemical properties of earthworm skin mucus exhibited different trends compared to those of the habitat soil. (2) Alpha diversity analysis revealed a declining trend in Shannon indices across all three microhabitats. (3) Beta diversity analysis revealed that the transition from warm temperate deciduous broad-leaved forest to cold temperate coniferous forest exerted the most significant impact on the gut bacterial communities of earthworms, while its influence on the skin bacterial communities was comparatively less pronounced. (4) Actinobacteria and Proteobacteria were the predominant phyla in earthworm skin, gut, and habitat soil, but the trends in bacterial community composition differed among the three microhabitats. (5) Mantel tests revealed significant correlations between bacterial community structures and climatic factors, physicochemical properties of earthworm habitat soil, and physicochemical properties of earthworm skin mucus. The findings of this study offer novel perspectives on the interplay between earthworms, microorganisms, and the environment within forest ecosystems.

Different Responses of Terrestrial Carbon Fluxes to Environmental Changes in Cold Temperate Forest Ecosystems

Different Responses of Terrestrial Carbon Fluxes to Environmental Changes in Cold Temperate Forest Ecosystems

Ubiquity of methanogenic archaea in the trunk of coniferous and broadleaved tree species in a mountain forest.

Wetwood of living trees is a habitat of methanogenic archaea, but the ubiquity of methanogenic archaea in the trunk of various trees has not been revealed. The present study analysed methanogenic archaeal communities inside coniferous and broadleaved trees in a cold temperate mountain forest by culture-dependent or independent techniques. Heartwood and sapwood segments were obtained from the trunk of seven tree species, Cryptomeria japonica, Quercus crispula, Fraxinus mandshurica, Acer pictum, Aesculus turbinata, Magnolia obovata, and Populus tremula. Amplicon sequencing analysis of 16S rRNA genes showed that Methanobacteriaceae predominated the archaeal communities and Methanomassiliicoccaceae also inhabited some trees. Real-time PCR analysis detected methanogenic archaeal mcrA genes from all the tree species, with a maximum of 107copiesg-1 dry wood. Digital PCR analysis also detected mcrA genes derived from Methanobacterium spp. and Methanobrevibacter spp. from several samples, with a maximum of 105 and 104copiesg-1 dry wood. The enumeration by the most probable number method demonstrated the inhabitation of viable methanogenic archaea inside the trees; 106cellsg-1 dry wood was enumerated from a heartwood sample of C. japonica. Methanogenic archaea related to Methanobacterium beijingense were cultivated from a heartwood sample of Q. crispula and F. mandshurica. The present study demonstrated that the inside of various trees is a common habitat for methanogenic archaeal communities and a potential source of methane in forest ecosystems.

Ring- and diffuse-porous tree species coexisting in cold and humid temperate forest diverge in stem and leaf phenology

Leaf and stem phenology are critical drivers of tree growth patterns in seasonal climates, but the implications for species differences in radial stem growth dynamics are still poorly studied. In our study, we compared the leaf phenology and stem phenology with the underlying cell development as well as annual stem growth between five diffuse-porous (DP) and five ring-porous (RP) coexisting angiosperm species in cold and humid temperate forests. Our results show that RP species unfolded leaves later but initiated wood growth earlier compared to DP species. Yet, xylem vessel maturation in the stem started in June and was remarkably synchronized between DP and RP, which implies that species from both functional groups can effectively avoid vessel cavitation potentially triggered by late spring frost. DP species exhibited one peak in stem growth across the growing season reflecting a uniform vessel formation pattern. Instead, RP species exhibited two peaks in stem growth, with the first peak reflecting expansion of early-wood vessels and the second peak related to subsequent fiber and vessel proliferation in the late-wood. In general, species with a greater number of growth days from the start of cambium activity until full lignification of cells exhibited higher annual stem growth, regardless of species group. The observed differences in leaf and stem phenology between DP and RP species are discussed with respect to the adaptation potential of the two functional groups to changing climate conditions in cold and humid temperate forests.

Fractionation of Inorganic Phosphorus in Cold Temperate Forest Soils: Associating Mechanisms of Soil Aggregate Protection and Recovery Periods after Forest Fire Disturbance

The soil aggregate is the fundamental unit of soil structure. The fractionation characteristics and influencing factors of phosphorus (P) in soil aggregates inherently link its geochemical characteristics and recycling mechanism. This work investigated the fractionation characteristics of inorganic P in cold temperate forest soils and studied the impacts of recovery periods after forest fires and soil aggregate protection mechanisms on P fractionation. Our results showed that the TP, active P, stable P, and total organic carbon (TOC) contents varied with increasing recovery years after forest fire disturbance. The TP content in the coarse particulate organic matter fraction (cPOM) exhibited an increasing trend with the number of recovery years. Redundancy analysis (RDA) and correlation analysis indicated that TOC played a crucial role in influencing the dynamics of P fractionation during the recovery process. The order of TP levels in different soil aggregate fractions was as follows: μClay > dClay > LF > cPOM > dSilt > μSilt > iPOM, with significant contributions from the cPOM and dSilt fractions. The ranking of P fractions in bulk soils was as follows: ACa-P > Fe-P > Oc-P > Or-P > De-P > Al-P > Ex-P. The protective mechanism of soil aggregates had a more significant effect on TOC than TP, with the order of protective abilities being: Phy×biochem-protected > Biochem-protected > Phy-protected > Non-protected mechanism. TOC and recovery years emerged as critical factors influencing the dynamics of different P fractions during post-fire recovery. Soil aggregate protection mechanisms demonstrated significantly higher effects on TOC than on TP. This study provides insights into the fractionation mechanisms of P in the soil–forest ecosystem of the Greater Khingan Mountains, contributing to the sustainable development and utilization of cold temperate forest ecosystems.

Effect of severe wildfire on soil phosphorus fractions and adsorption in a cold temperate coniferous forest after 5 years

AbstractForest fires are a primary driver of biogeochemical processes in ecosystems and affect the soil nutrient balance by altering the distribution of organic matter and associated nutrients as well as the composition and availability of elemental nutrients. We investigated the changes in soils’ phosphorus (P) fractions and the adsorption characteristics of potassium dihydrogen orthophosphate (orthoP) and myo‐inositol hexakisphosphate (IHP) at two depths (0–5 and 5–10 cm) in soils from two sites differing in fire severity: long‐unburned and heavily burned. Five years after the fire, there were increases in the total P and extractable inorganic P (H2O‐P, NaHCO3‐Pi, NaOH‐Pi, D.HCl‐Pi and C.HCl‐Pi) contents. Conversely, there was a decrease in organic P (NaHCO3‐Po, NaOH‐Po and C.HCl‐Po). The adsorption of soil for orthoP at a depth of 0–5 cm was dependent on the amount of P supplied by the soil; at low concentrations, heavily burned soil showed a lower adsorption than long‐unburned soil. However, at high concentrations, the adsorption of heavily burned soil was significantly larger than that of long‐unburned soil. With respect to IHP, the adsorption of long‐unburned soil was also more significant at depths of 0–5 cm. The adsorption of both orthoP and IHP of heavily burned soil was significantly higher than that of long‐unburned soil at a depth of 5–10 cm. Fire also decreased the binding degree (k1) of soil‐P and the solid phase at depths of 0–5 and 5–10 cm. The increase in P adsorption capacity outweighed the addition of P from ash, resulting in less leaching in heavily burned areas and minimizing P loss. Overall, forest fires significantly affect the adsorption characteristics and P fractions of soil, specifically orthoP and IHP, during the initial stage of postfire recovery. These effects are closely related to the direct influences of iron oxide, soil organic matter and aluminium oxide in the soil and may even produce relatively long‐term effects on the P recycling process of the entire ecosystem.

The cooling and warming effects of potential forest transition on local land surface temperature in Northeast China

Forest cover change directly affects the surface energy balance by altering the radiative and non-radiative properties of the surface. These competing processes may yield considerable biophysical impacts on local and regional climate that depend on background climate and specific forest type. Here we compared the differences in land surface temperature (LST) between temperate forests and adjacent croplands/grasslands to quantify the potential biophysical effects of transitions from croplands/grasslands to forests in Northeast China, based on multiple satellite observation products from 2001 to 2016. Forests were found to show a slight lower daytime LST and strong higher nighttime LST than adjacent croplands or grasslands. As a result, the daily LST of forests was 0.15 ± 0.06 ℃ and 0.32 ± 0.04 ℃ higher than that of croplands and grasslands, respectively. On the seasonal scale, the warming effect of cropland/grassland-to-forest transition during non-growing season outweighed the cooling effect during growing season, and dominated the annual positive LST response. Moreover, the cooling effect of cropland-to-forest transition during growing season was stronger in the early growth stage than late growth stage (−1.65 ± 0.9 ℃ in May to June, −0.39 ± 0.5 ℃ in July to September). The net cooling effect of warm temperate broadleaved forests was found to shift toward net warming effect of cold temperate coniferous forests with increasing latitude. The daytime cooling effect of forests was mainly driven by increased non-radiative evapotranspiration. Overall, the radiative process related to the solar energy dominated the net warming effect of forest transitions over Northeast China. Estimating the climate feedback potential of forests could be useful to provide theoretical references for the adaptation and mitigation strategies for climate change.

Phyllospheric fungal diversity in decomposing larch leaf litter: a comparative study of epiphytic and endophytic fungi.

Epiphytic and endophytic fungi are primary decomposers of forest litter due to their complex species composition and metabolic functions. To clarify the community diversity of phyllospheric fungi and to explore nutrient loss and the role of fungal decomposition, we conducted a study on the decomposition of leaf litter during the 1-year decomposition of Larix gmelinii in the cold temperate zone. Fungal diversity data were characterized via Single Molecule Sequencing (based on the Sequel II Sequencing System) and statistical analyses in R. Our findings revealed the presence of 11 known fungal phyla and 29 dominant genera in the larch litter of Greater Khingan. Among these, Basidiomycota and Leucosporidium were dominant in the epiphytic environment, while Ascomycota and Exutisphaerella dominated the endophytic environment. In the early periods of decomposition, phyllospheric fungi became the primary colonizers during litter decomposition by adjusting their life strategies to transition to saprophytic or pathogenic metabolic processes. During decomposition, significant differences in alpha diversity were observed between endophytes and epiphytes. Correlation analysis between these fungi and biological factors revealed a strong relationship between cellulose loss in leaves and the return of N, P, and K. This indicated that the combined biological effects of nutrients, aminosugars, and plant fibers strongly explained changes in community structure. Our results also revealed a significant clustering effect between fungi and biological factors, reflecting the important role of phyllospheric functional fungal communities in carbon fluctuations, cellulose decomposition, and the enrichment of P and K in leaf litter. In summary, this study offers insights into ecosystem processes and nutrient cycling within cold temperate forests, with potential applications for understanding global carbon dynamics.

Global assessment of soil methanotroph abundances across biomes and climatic zones: The role of climate and soil properties

The pmoA gene serves as a biomarker of the methane-oxidizing communities in soils. Therefore, much effort has been directed at quantifying the pmoA gene to quantify the abundances of methanotrophs at the local or regional scale, however, the abundances of methane-oxidizing bacteria as well as factors shaping the abundance of methane-oxidizing bacteria at the global scale remains poorly understood. To fill this knowledge gap, we performed a quantitative analysis of peer-reviewed publications to assess the distribution of the pmoA gene abundances across various biomes, climatic zones, land use, and between forest and grassland biomes, with 114 observations collected from 27 peer-reviewed articles. Results showed that the abundance of pmoA genes increased significantly with latitude, whereas a higher pmoA gene abundance was observed in the boreal forest than in cold grassland, dry grassland, temperate forest, and temperate grassland, while tropical grassland and the tropical forest did not differ significantly from other biomes in pmoA gene abundance. The PCA indicated that pmoA abundance was positively correlated with MAT and MAP but negatively correlated with pH. The TOC was as a key driver of pmoA gene abundance at a global scale. The abundance of the pmoA gene in tropical and boreal forests increased with TOC, while the pmoA gene abundance in temperate forests and grasslands decreased with TOC. The pmoA gene abundance in the tropical and subtropical zones increased with TOC while pmoA gene abundance in the temperate climatic zones decreased with TOC. The path model revealed a direct effect of vegetation cover on the pmoA gene abundance, but indirect effect of climate and soil properties on pmoA gene abundance via their direct effect on vegetation cover. We suggest that the changes of TOC and C:N ratio due changes of vegetation and climate across biomes may serve as a possible mechanism underlying the idiosyncratic effects of TOC on the abundance of methanotrophs in soils.

Temperature and moisture sensitivities of soil respiration vary along elevation gradients: An analysis from long-term field observations

Based on long-term field observation data over 11 years at 23 sites in two mountainous areas (TS1 and TS2) at elevations from 829 to 2700 m, where the dominant vegetation type of TS1 and TS2 was temperate mixed broadleaf-coniferous forest and cold temperate coniferous forest, respectively, we analyzed the correlations between soil respiration (Rs) and abiotic and biotic factors to explore the response patterns of Rs to environmental factors within and between the sites along the elevation gradient. We found that soil moisture (θ) and its combinations (Ts × θ and θ/Ts) with soil temperature (Ts) increased significantly with increasing elevation, while Ts, soil bulk density (SBD), C/N ratio, and pH decreased significantly with increasing elevation. Within each site, both exponential- Ts (ET) and Gaussian-Ts (GT) models could be used for predicting the Rs seasonal variation, except for two sites in the area of TS1, where θ was a better predictor than Ts. The integrated ET–θ and GT–θ models could be applied to all sites except for 22S, and both were superior to the ET and GT models. The mean Rs of each site over the measurement period ranged from 3.07 to 6.94 μmol CO2 m−2 s−1 and showed a quadratic increase along the elevation gradient. Among the 23 sites, Q10 ranged from 1.15 to 3.79, and it increased with elevation, reaching a maximum at an elevation of 2366 m; the θ sensitivity parameter (d) decreased significantly with elevation and reached a minimum at an elevation of 1975 m. Both the d and Ts sensitivity parameter (b) of Rs were complementary to each other along the elevation gradient. Among the sites, Ts, θ, and combinations of the two were more important drivers for both Rs and Q10 variations than microbial and physicochemical indicators.

Differences in functional niche hypervolume among four types of forest vegetation and their environmental determinants across various climatic regions in China.

Functional traits play an important role in studying the functional niche in plant communities. However, it remains unclear whether the functional niches of typical forest plant communities in different climatic regions based on functional traits are consistent. Here, we present data for 215 woody species, encompassing 11 functional traits related to three fundamental niche dimensions (leaf economy, mechanical support, and reproductive phenology). These data were collected from forests across four climatic zones in China (tropical, subtropical, warm-temperate, and cold-temperate) or sourced from the literature. We calculated the functional niche hypervolume, representing the range of changes in the multidimensional functional niche. This metric quantifies how many functional niche spaces are occupied by existing plants in the community. Subsequently, we analyzed differences in functional niche hypervolume and their associated environmental factors across different types of forest vegetation. The results indicate that the functional niche hypervolume and the degree of forest vegetation overlap decrease with increasing latitude (e.g., from tropical rainforest to cold temperate coniferous forest). The total explanatory power of both climate and soil factors on the variation in functional niche hypervolume was 50%, with climate factors exhibiting a higher explanatory power than soil factors. Functional niche hypervolume is positively correlated with climate factors (annual mean temperature and annual precipitation) and negatively correlated with soil factors (soil pH, soil organic matter content, soil total nitrogen content, and soil total phosphorus content). Among these factors, annual mean temperature, soil pH, and soil total nitrogen content most significantly affect the difference in functional niche hypervolume among forest vegetation. Our study emphasizes the significant variation in the functional niche hypervolume among typical forest vegetation in China.

Elevational patterns of microbial species richness and evenness across climatic zones and taxonomic scales.

Understanding the elevational patterns of soil microbial diversity is crucial for microbial biogeography, yet the elevational patterns of diversity across different climatic zones, trophic levels, and taxonomic levels remain unclear. In this study, we investigated the elevational patterns of species richness, species evenness and the relationship between species richness and evenness (RRE) in the forest soil bacterial and fungal communities and individual phyla across three climatic zones (tropical, subtropical, and cold temperate). Our results revealed that soil bacterial richness (alpha diversity) decreased with elevation, while fungal richness exhibited a hump-shaped pattern in the tropical and cold-temperate forests. Elevational patterns of evenness in bacterial and fungal communities showed the hump-shaped pattern across climatic zones, except for bacterial evenness in the tropical forest. Both bacterial and fungal richness and evenness were positively correlated in the subtropical and cold-temperate forests, while negatively correlated for bacteria in the tropical forest. The richness and evenness of soil microorganisms across different regions were controlled by climatic and edaphic factors. Soil pH was the most important factor associated with the variations in bacterial richness and evenness, while mean annual temperature explained the major variations in fungal richness. Our results addressed that the varieties of elevational patterns of microbial diversity in climatic zones and taxonomic levels, further indicating that richness and evenness may respond differently to environmental gradients.

Landscape Dynamics and Ecological Risk Assessment of Cold Temperate Forest Moose Habitat in the Great Khingan Mountains, China.

The change in habitat pattern is one of the key factors affecting the survival of the moose population. The study of the habitat landscape pattern is the key to protecting the Chinese cold-temperate forest moose population and monitoring the global distribution of moose. Through the ecological risk assessment of the moose habitat landscape pattern in a cold-temperate forest, we hope to assess the strength of habitat resistance under stress factors. This study provides a theoretical basis for the protection of the moose population in the cold-temperate forest in China and the establishment of the cold-temperate forest national park. In the study, the MaxEnt model, landscape index calculation and ecological risk assessment model construction were used to analyze the field survey and infrared camera monitoring data from April 2014 to January 2023. The habitat suitability layer of the moose population in the Nanwenghe National Nature Reserve of the Great Khingan Mountains was calculated, and the range of the moose habitat was divided based on the logical threshold of the model. The landscape pattern index of the moose habitat was calculated by Fragstats software and a landscape ecological risk assessment model was established to analyze the landscape pattern and ecological risk dynamic changes of the moose habitat in 2015 and 2020. The results showed that under the premise of global warming, the habitat landscape contagion index decreased by 4.53 and the split index increased by 4.86 from 2015 to 2020. In terms of ecological risk: the area of low ecological risk areas increased by 0.88%; the area of medium ecological risk areas decreased by 1.11%; and the area of high ecological risk areas increased by 0.23%. The fragmentation risk of the landscape pattern of the moose habitat tends to increase, the preferred patch type is dispersed, the degree of aggregation is low, and the risk of patch type transformation increases. The middle and high ecological risk areas are mainly concentrated in the river area and its nearby forests, showing a fine and scattered distribution. Under the interference of global warming and human activities, the fragmentation trend of the moose habitat in the study area is increasing, and the habitat quality is declining, which is likely to cause moose population migration. For this reason, the author believes that the whole cold temperate forest is likely to face the risk of increasing the transformation trend of dominant patch types in the cold-temperate coniferous forest region mainly caused by global warming, resulting in an increase in the risk of habitat fragmentation. While the distribution range of moose is reduced, it has a significant impact on the diversity and ecological integrity of the whole cold-temperate forest ecosystem. This study provides theoretical references for further research on the impact of climate warming on global species distribution and related studies. It is also helpful for humans to strengthen their protection awareness of forest and river areas and formulate reasonable protection and sustainable development planning of cold-temperate forests. Finally, it provides theoretical references for effective monitoring and protection of cold-temperate forests and moose population dynamics.

Effects of nitrogen addition on greenhouse gas fluxes during continuous freeze-thaw cycles in a cold temperate forest.

Both nitrogen (N) deposition and soil freeze-thaw cycles (FTCs) induce pulses of greenhouse gas (GHG) emissions in cold temperate zones due to changes in soil carbon (C) and nitrogen (N) turnover. However, the combined effects of N addition and FTCs on GHG fluxes have received little research attention, particularly in boreal forests. We conducted a laboratory incubation experiment using intact soil cores from Rhododendron dauricum-Larix dahurica plots to investigate the GHG flux response to these combined effects. We separated the soil samples into seven groups (no, low, medium, and high sodium nitrate addition and low, medium, and high ammonium chloride addition) and exposed each group to continuous FTC conditions. The N2O and CO2 emissions were eventually stimulated by the FTCs, while CH4 uptake was inhibited by FTCs but responded differently under different N addition treatments. All the treatments had substantially increased N2O emissions compared to the control. However, the soil respiration rate significantly increased only with medium sodium nitrate addition, and high levels of N addition (regardless of form) inhibited CH4 uptake. These findings demonstrate that FTCs and N addition (in various forms and levels) have considerable effects on GHG emissions in temperate forest ecosystems. Moreover, dissolved organic carbon (DOC), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and inorganic nitrogen in soil are potential factors that drive GHG emissions and are necessary considerations in predicting future feedback effects of GHG emissions on climate change.

Roles of climatic and anthropogenic factors in shaping Holocene vegetation and fire regimes in Great Dismal Swamp, eastern USA

The Great Dismal Swamp wetland, spanning >400 km2 along the Virginia and North Carolina border, was shaped by a complex combination of geomorphic, climatic, and anthropogenic forcings during the last 14,000 years. Pollen, macrofossils, charcoal, and physical properties from sediment cores at seven sites provide a detailed record of the spatial heterogeneity of the wetland and the roles played by natural hydrologic variability, wildfire, and human modification of drainage in shaping vegetation and habitats. Cold-temperate forests occupied regional uplands from at least 13.5–10.3 cal ka BP. Marshes dominated by grasses and other herbaceous taxa began developing along low-elevation streams as early as 10.3 cal ka BP, resulting in accumulation of organic silts. Long-hydroperiod, peat accumulating marshes, with abundant floating aquatic plants, developed as early as 9.6 cal ka BP, as rapid rates of sea-level rise elevated the water table and facilitated wetland development and peat accumulation along stream courses. By the mid-Holocene (c. 7–6.5 cal ka BP), when local sea-level rise began slowing and reached about 12–15 m below present, shorter hydroperiod, peat-accumulating marshes dominated the landscape, with increased wildfire activity. Great Dismal Swamp vegetation shifted from marshes to peat-accumulating forested wetlands by c. 3.7 cal ka BP; these were dominated by varying combinations of Nyssa (tupelo), Taxodium (cypress), and Chamaecyparis thyoides (Atlantic white cedar). Wildfires were infrequent during this time, and the forested wetlands persisted, with minor compositional changes related to climate-driven fluctuations in stream flow, until colonial ditching and logging began in the swamp during the late 18th century. These activities decreased cypress and cedar populations, and, by the mid-20th century, expanded ditching resulted in even drier conditions and expansion of maple-gum (dominated by Acer and Liquidambar), and pine-pocosin (dominated by Pinus) forests. The distribution of these forests differs from that of the late Holocene and represents a fundamental shift in hydrology, peat structure, vegetation, and fire regime due to landscape alterations of the last few centuries.

Priority conservation area of Larix gmelinii under climate change: application of an ensemble modeling.

Larix gmelinii (Rupr.) Kuzen is a major tree species with high economic and ecological value in the Greater Khingan Mountains coniferous forest of Northeast China. Reconstructing the priority Conservation Area of Larix gmelinii under Climate could provide a scientific basis for its germplasm conservation and management. The present study used ensemble and Marxan model simulations to predict species distribution areas and delineate priority conservation areas for Larix gmelinii in relation to productivity characteristics, understory plant diversity characteristics, and climate change impacts. The study revealed that the Greater Khingan Mountains and the Xiaoxing'an Mountains, with an area of approximately 300 974.2 km2, were the most suitable for L. gmelinii. The stand productivity of L. gmelinii in the most suitable area was significantly higher than that in the less suitable and marginally suitable areas, but understory plant diversity was not dominant. The increase in temperature under future climate change scenarios will reduce the potential distribution and area under L. gmelinii; the species will migrate to higher latitudes of the Greater Khingan Mountains, while the degree of niche migration will gradually increase. Under the 2090s-SSP585 climate scenario, the most suitable area for L. gmelinii will completely disappear, and the climate model niche will be completely separated. Therefore, the protected area of L. gmelinii was demarcated with a target of the productivity characteristics, understory plant diversity characteristics and climate change sensitive area, and the current key protected area was 8.38 × 104 km2. Overall, the study's findings will lay a foundation for the protection and rational development and utilization of cold temperate coniferous forests dominated by L. gmelinii in the northern forested region of the Greater Khingan Mountains.