Search Results (38)

The Qipanshan area in Northeastern China has diverse stand types and abundant forest resources, but extremely low resistance to external disturbances such as forest fires. Thus, improving the accuracy of understory fuel moisture content prediction is crucial for local forest fire prevention. This study focused on surface branch fuels in four typical stands (Larix gmelinii (Rupr.) Kuzen forest, Betula platyphylla Sukaczev forest, Pinus sylvestris var. Mongholica Litv. forest and cutover land) to evaluate the prediction and extrapolation performance of three hourly scale models (Nelson, Simard, and meteorological element regression models), and analyze their variations with slope positions and stand types, filling the gap in local hourly fuel moisture prediction model application. Results indicated that obvious spatial heterogeneity in fuel moisture content, closely affected by slope, fuel decay degree and microclimate, and thick, badly decayed branches had higher moisture content, with the highest in the Betula platyphylla forest and the lowest in cutover land. In terms of prediction accuracy, the Nelson model performed best, followed by the Simard model, while the meteorological element regression model was the poorest; predictions were more accurate in Pinus sylvestris var. mongholica forest and cutover land, and better on upper slopes than middle and lower slopes. For extrapolation capacity, the Simard model was optimal, followed by the Nelson model, while the meteorological element regression model was unfit for extrapolation due to excessive errors; extrapolation accuracy was best in cutover land and upper slopes. This study clarifies the applicability of the three models, providing methodological support for accurate real-time forest fire danger forecasting in the region. Full article

In this study, we focused on four major coniferous species in the eastern part of Inner Mongolia, namely Larix gmelinii var. principis-rupprechtii (Mayr) Pilg., Larix gmelinii (Rupr.) Kuzen., Pinus tabuliformis Carrière and Pinus sylvestris var. mongolica Litv. and carried out a systematic study on their ectomycorrhiae (EM) fungi. The present study was based on high-throughput sequencing. Based on the high-throughput sequencing data, analyzed by bioinformatics and statistical methods, the results showed that (1) a total of 150 operational taxonomic units (OTUs) were obtained, which belonged to 26 evolutionary branches of Basidiomycota and Ascomycota, respectively. Among them, Tricholoma, Tomentella-thelephora, Suillus-rhizopogon, Wilcoxina, Piloderma, Pustularia, Hygrophorus, Sebacina and Amphinema-tylospora are the EM fungi shared by four conifer species. (2) The species diversity and community composition of EM fungi differed significantly among tree species and sample plots, while soil total nitrogen (N) content and nitrogen/phosphorus (N/P) ratio were the main factors affecting community structure. (3) The Neutral Community Model (NCM) and β-Nearest Taxon Index (β-NTI) showed that stochastic processes dominated the construction of EM fungal communities. The results of this study revealed the geographical distribution pattern and maintenance mechanisms of EM fungal communities of four coniferous species in the eastern part of Inner Mongolia, which provides a scientific basis for the restoration practice of disturbed ecosystems and the sustainable development of the regional economy. 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

The changes in soil nitrogen mineralization rate induced by litter input can determine the availability of nitrogen for plant growth in the soil. In forest ecosystems, the mixing of different species of litter can alter the chemical properties of the litter, ultimately affecting the rates of soil nitrogen transformation and cycling. In this study, litters with Fraxinus mandshurica Rupr. and Larix gmelinii (Rupr.) Kuzen. and mixed litter with Fraxinus mandshurica and Larix gmelinii were added to dark brown soil and incubated in the lab for 175 days at 25 °C. NH₄⁺-N and NO₃⁻-N contents and nitrogen mineralization rates were periodically measured to explore the effect of mixed litter addition on soil nitrogen mineralization. The results showed that compared to Larix gmelinii litter, Fraxinus mandshurica litter demonstrates higher carbon, nitrogen, and phosphorus contents while exhibiting lower lignin and cellulose contents and lower C/N and lignin/N ratios. Soil inorganic nitrogen content showed a trend of initial decrease followed by an increase. At the end of the incubation, soil NH₄⁺-N and NO₃⁻-N and the total inorganic nitrogen contents were 4.6–7.8 times, 2.2–3.4 times, and 2.9–4.3 times higher than the initial value, respectively. The soil nitrogen mineralization rate exhibited an initial rapid increase followed by stabilization. During days 7–28 of incubation, the nitrogen mineralization rates in litter addition treatments were lower than that in the control, while they were higher than that in the control during days 42–175. The soil nitrogen mineralization rate in the treatments with Fraxinus mandshurica litter and mixed litter were higher than those in the treatment with Larix gmelinii litter. The cumulative net nitrogen mineralization amounts in the Fraxinus mandshurica litter and mixed litter treatments were higher than those in the Larix gmelinii litter treatment, being 1.5 and 1.2 times those of the Larix gmelinii litter treatment, respectively. MBC and MBN presented a trend of first increasing and then decreasing, peaking on days 7 and 14 of incubation, respectively. Correlation analysis revealed that soil inorganic nitrogen content and nitrogen mineralization rate were positively correlated with the litter total nitrogen and soil microbial carbon and nitrogen and negatively correlated with litter C/N and lignin/N. The changes in soil inorganic nitrogen and nitrogen mineralization are primarily associated with soil microbial immobilization. Initially, in the treatments with litter addition, an increase in microbial biomass enhanced the immobilization of soil inorganic nitrogen. Subsequently, as litter mineralization progressed, the amount of litter decreased, leading to reduced microbial biomass and weakened immobilization. This study indicates that the interaction between litter types and soil microorganisms is the key factor affecting soil nitrogen mineralization process and soil mineral nitrogen content. These findings provide a scientific basis for soil fertility management in the forest ecosystems of Northeast China. Full article

Soil enzymes mediate organic matter decomposition and nutrient cycling, and their stoichiometry can indicate microbial nutrient demands. However, research on the variations in soil enzymes and microbial nutrient limitation under different temperate forest types still lacks insight. In this study, we sampled soils under five typical forest types (including Betula platyphylla Suk. forest, Fraxinus mandschurica Rupr forest, Larix gmelinii (Rupr.) Kuzen. forest, Populus davidiana Dode forest, and Pinus koraiensis Siebold et Zucc.forest) in the temperate climatic region of northeast China. Soil enzyme activities and soil microbial community composition and diversity were determined for each, and vector analysis was used to quantify the value of microbial limitation. The results showed that soil enzyme activity, enzyme stoichiometry, and microbial community structure were significantly different among the five temperate forest types. The ratios of soil C:N:P acquiring enzyme activity were close to 1:1:1. All the forests showed prevalent P limitation over N limitation (all vector angles > 45°), and the degree of impact varied among different forest types. Redundancy analysis (RDA) and Pearson’s test demonstrated that soil enzyme activities and microbial nutrient limitation were mainly determined by soil physical properties and microbial community. These results contribute to understanding the mechanisms that link plant composition, soil enzyme activity, and microbial nutrient limitation in temperate forests. Full article

The impact of frequent water deficits on dominant tree species in boreal forests has received increased attention, particularly towards addressing the global climate change scenarios. However, the impacts of coupled light intensity and water deficit in the regeneration and growth of Larix gmelinii seedlings, a dominant species in China’s boreal forests, are still unclear. We conducted a dual-factor controlled experiment with four light intensities (natural sunlight, 50% shading, 75% shading, and 90% shading) and three soil water conditions (80%, 60%, and 40% soil saturated water content). The results showed that the coupling of light and water has a significant effect on the growth and development of Larix gmelinii seedlings. In 40% of the saturated soil moisture content, net photosynthetic rate, transpiration rate, chlorophyll a, and total phenol—leaf were significantly lower than the same light conditions under 80% soil saturated water content. Under the coupling treatment of 60% soil saturated water content and 50% shading treatment, the plant height increment, net photosynthetic rate, stomatal conductance, transpiration rate, chlorophyll a, and phenolic compound content were significantly higher than those of other coupling treatments; however, more than 75% shading inhibited photosynthetic parameters, chlorophyll a, total flavonoid—leaf, and total flavonoid—branch. Our results have important implications for forest management practices; they provide a scientific reference for the early growth of Larix gmelinii seedlings under the coupling of light and water and promote the survival and growth of seedlings. Full article

Fire is crucial for shaping northern forest ecosystems and can affect soil microbial community structure. However, there are few studies on the long-term effects of forest fire disturbance on soil microbial community diversity. In this study, we employed high-throughput sequencing of 16S rRNA and ITS1 to assess variations in the abundance of bacterial and fungal communities in dominant populations at 1, 6, and 11 years post-fire. Furthermore, a comprehensive analysis was conducted to examine the relationship between soil microenvironmental changes and soil microbial communities after fire disturbances, considering soil physicochemical properties, including bulk density, moisture content, pH, organic carbon, total nitrogen, ammonium nitrogen, nitrate nitrogen, available potassium, and available phosphorus. We found that fire significantly increased soil pH, NO₃⁻-N, AP, and AK contents, in which the content of NO₃⁻-N basically recovered to the pre-fire level at 11 years after fire. The soil SOC and TN contents decreased significantly 1 year after the fire. However, compared to the unfired site, the SOC content essentially recovered 11 years after the fire, while TN content was still significantly higher 11 years after fire. Furthermore, fire changed the diversity and richness of soil microbial communities to some extent. PCoA and NMDS analyses suggested that the bacterial community structures in soil samples from different burned areas with different recovery periods exhibited similarity. However, notable differences were observed in the fungal community structures between the 1-year and 6-year post-fire study sites when compared to the unburned control site. Bacterial communities predominantly comprised Proteobacteria, Actinobacteria, and Acidobacteria, while fungal communities were mainly dominated by Ascomycota and Basidiomycota. RDA confirmed the significant roles of SOC, TN, and NO₃⁻-N in affecting the diversity of soil microbial communities. Therefore, our study not only enhances our understanding of the long-term effects of forest fire disturbances on soil properties and soil microbial community structure, but also provides insights for further utilizing and controlling carbon and nitrogen content to regulate soil microbial activity and accelerate the recovery process of burned areas. Full article

Against the background of global warming, trees in high-latitude and high-altitude areas are more sensitive to rapid warming. Revealing the response patterns of trees at different altitudes to rapid warming in typical alpine mountain environments can help to predict the future distribution of forests in the region and the associated changes in the timberline. This study used tree-ring width data (band sampling) from Dahurian larch (Larix gmelinii Rupr.) along an altitudinal gradient (970–1409 m) on Oakley Mountain to establish 10 chronologies and to analyze the growth–climate response of larch to warming and altitudinal changes along a gradient. The results showed that before rapid warming, larch growth was strongly influenced mainly by precipitation in July–August, while after warming, the growth was controlled mainly by precipitation (snowfall) in winter (October–April) and showed a significant positive correlation with the SPEI in winter and a negative correlation with temperature in February–April (early spring). This indicates that the rapid warming event led to a drastic change in the water heat balance during the pre-growth period of the trees in the study area, which shifted the tree growth from being restricted by drought in the growing season before warming to being restricted by winter drought (i.e., the lagged effect of snowfall in the pre-growing season) after warming and that the trees at low altitudes suffered from more severe winter drought. In the future, as the global climate warms further, the growth of mountain larch at low altitudes (below 1200 m) will continue to decrease, and the coupling of winter snowfall and seasonal (February–April) warming will increase the upper altitude limit at which winter drought occurs for larch in the study area; additionally, larch at higher altitudes will be able to cope with this ecological process better. Full article

Global warming significantly affects forest ecosystems in the Northern Hemisphere’s mid-to-high latitudes, altering tree growth, productivity, and spatial distribution. Additionally, spatial and temporal heterogeneity exists in the responses of different tree species to climate change. This research focuses on two key species in China’s Greater Khingan Range: Larix gmelinii (Rupr.) Kuzen. (Pinaceae) and Quercus mongolica Fisch. ex Ledeb. (Fagaceae). We utilized a Maxent model optimized by the kuenm R package to predict the species’ potential habitats under various future climate scenarios (2050s and 2070s) considering three distinct Shared Socioeconomic Pathways: SSP1-2.6, SSP2-4.5, and SSP5-8.5. We analyzed 313 distribution records and 15 environmental variables and employed geospatial analysis to assess habitat requirements and migration strategies. The Maxent model demonstrated high predictive accuracy, with Area Under the Curve (AUC) values of 0.921 for Quercus mongolica and 0.985 for Larix gmelinii. The high accuracy was achieved by adjusting the regularization multipliers and feature combinations. Key factors influencing the habitat of Larix gmelinii included the mean temperature of the coldest season (BIO11), mean temperature of the warmest season (BIO10), and precipitation of the driest quarter (BIO17). Conversely, Quercus mongolica’s habitat suitability was largely affected by annual mean temperature (BIO1), elevation, and annual precipitation (BIO12). These results indicate divergent adaptive responses to climate change. Quercus mongolica’s habitable area generally increased in all scenarios, especially under SSP5-8.5, whereas Larix gmelinii experienced more complex habitat changes. Both species’ distribution centroids are expected to shift northwestward. Our study provides insights into the divergent responses of coniferous and broadleaf species in the Greater Khingan Range to climate change, contributing scientific information vital to conserving and managing the area’s forest ecosystems. Full article

It is necessary to understand the radial growth responses of trees in the Greater Khingan Range to climatic factors to predict changes in forest ecosystems under climate change scenarios. We sampled Mongolian pine (Pinus sylvestris var. mongolica) and Dahurian larch (Larix gmelinii (Rupr.) Kuzen) at four locations at elevations of 900–1100 m in the Greater Khingan Range to establish a tree-ring chronology. The Vaganov–Shashkin (VS) model was used to describe the relationship between tree radial growth and the dominant limiting climatic factors with a focus on physiological processes. The results showed that the VS model accurately reflected the effects of various climatic factors on the growth of Mongolian pine and Dahurian larch. The simulated and measured tree-ring widths index (RWI, the same as below) were consistent. The physiological parameters affecting tree growth differed for the two tree species in the study area. Mongolian pine required higher temperatures and less soil moisture for growth than Dahurian larch. The growth rings of the two tree species are more consistent across the elevation gradient. Higher-elevation trees had an “intensive strategy” with shorter growing periods and high growth rates, whereas low-elevation tree species had a “broad strategy” with lower maximum growth rates for longer periods. The start and cessation date of tree growth strongly affected the RWI of Mongolian pine and high-elevation Dahurian larch, but no significant effect on the RWI of low-elevation Dahurian larch. Differences in the limiting climatic factors were observed between Mongolian pine and Dahurian larch. Mongolian pine shows some similarity between high and low elevations, subject to the common limitations of temperature and soil moisture during the growing season for both, with a greater proportion of the lower elevations being limited by soil moisture. Dahurian larch was influenced by the growing season temperatures and May–August soil moisture at higher elevations and by the growing season soil moisture at lower elevations. This study provides a scientific basis for the management and conservation of forest ecosystems in the Greater Khingan Range. Full article

Bark is vital for woody plants, providing protection, transporting nutrients and water, and storing essential resources. For fire-prone ecosystems, bark thickness is a key adaptive trait conferring fire resistance. Few studies have been conducted on the drivers of variation in bark thickness of the widely distributed Larix gmelinii (Rupr.) Kuzen in the Great Xing’an Mountains region, on the southern edge of East Siberia, where surface fire disturbances are frequent. To elucidate the relationships between variation in bark thickness (inner vs. outer bark) of L. gmelinii and plant size, environmental factors, and co-variation with other fire-tolerance traits, we selected 26 sites to set up plots and carried out a survey and bark sampling. Results showed that stem diameter primarily determines variation in bark thickness, especially outer bark. The proportion of outer bark to total bark increased accordingly as the tree increased in size. We also observed stronger correlated variation in outer bark thickness, tree height, and self-pruning capacity, implying that larger trees have thicker protective outer bark and taller heights with greater self-pruning, mitigating crown fire risks. Environmental factors appear to have a relatively limited effect on changes in bark thickness in L. gmelinii. Mean air temperature, annual precipitation, and total soil nitrogen content had some effect on outer bark thickness, and mean air temperature had some effect on inner bark thickness. Full article

Crown width (CW) is an important indicator for assessing tree health, vitality, and stability, as well as being used to predict forestry models and evaluate forest dynamics. However, acquiring CW data is laborious and time-consuming, making it crucial to establish a convenient and accurate CW prediction model for forest management. In this study, we developed three models capable of conducting calibration: generalized models (GM), quantile regression models (QR), and mixed-effects models (MIXED). The aim was to effectively improve the prediction accuracy of CW using data from Dahurian larch (Larix gmelinii Rupr.) in Northeastern China. Different sampling designs were applied, including selecting the thickest, thinnest, intermediate, and random trees, with 1 to 10 sample trees for each design. The results showed that all models achieved accurate CW predictions. MIXED displayed the most superior fitting statistics than GM and QR. In model validation, with the increase in the number of sample trees, the model prediction accuracy gradually improved and the model differences gradually reduced. MIXED produced the smallest RMSE, MAE, and MAPE across all sampling designs. The intermediate tree sampling design with the best validation statistics for the given sample size was selected as the final sampling design. Under intermediate tree sampling design, MIXED required a minimum of five sample trees, while GM and QR required at least five and six sample trees for calibration, respectively. Generally, we suggested selecting MIXED as the final CW prediction model and using the intermediate tree sampling design of five trees per plot. This study could provide ideas and support for forest managers to accurately and efficiently predict CW. Full article

The accurate habitat suitability evaluation of forest species is vital for forest resource management and conservation. Therefore, the previously published thresholds of soil organic carbon (SOC) contents for the six main forest species were used to screen sample points in this study; the maximum entropy modeling (MaxEnt) was applied to predict the potential distribution of those species in Lvliang Mountain, Shanxi Province, China. The following results were derived: (1) the area under the curve (AUC) value of the MaxEnt model was 0.905, indicating the model results had high accuracy; (2) the main environmental factors affecting the woodlands were mean diurnal temperature range, solar radiation, population density and slope; (3) the model accurately depicted the most suitable areas for those species, namely Populus davidiana Dode (Malpighiales: Salicaceae), Betula platyphylla Sukaczev (Fagales: Betulaceae), Quercus wutaishanica Mayr (Fagales: Fagaceae), Platycladus orientalis (L.) Franco (Pinales: Cupressaceae), Larix gmelinii (Rupr.) Kuzen. (Pinales: Pinaceae) and Pinus tabuliformis Carrière (Pinales: Pinaceae). This study has improved the representativeness of the samples based on prior knowledge to enhance the biological meaning and accuracy of the prediction results. Its findings provide a theoretical basis for the forest resource protection, management measures alongside the reconstruction of low-yield and low-efficiency forests. Full article

The rapid urbanization process and high-intensity construction mode have greatly changed the underlying surface structure and spatial distribution of the natural land surface, further amplified the possibility of urban floods, and made urban security face more serious threats. Urban forest could help to mitigate urban floods through water holding and interception by its unique structures, especially the litter layer. This paper compared the ability of different forest tree species on urban floods mitigation, through analyzing their litter accumulation, litter water holding characteristics, and water interception features of different decomposed layers. The results concluded that Quercus mongolica Fisch. ex Ledeb. (QM) forest, Betula platyphylla Sukaczev (BP) forest, Larix gmelinii (Rupr.) Kuzen. (LG) forest, and Picea koraiensis Nakai (PK) forest were the best choices for improving urban floods resistance in a high-urbanization winter city, for they had larger litter mass and higher maximum water holding and interception capacity. The corresponding results of this study could help environmental management departments worldwide in the selection of tree species in urban greening projects focusing on urban flood control. Full article

Wildfires are one of the most important environmental factors controlling forest ecosystem physiology and the carbon balance in the permafrost zone of North Siberia. We investigated tree-ring width (TRW) and stable isotope chronologies in tree-ring cellulose (δ¹³C_Cell, δ¹⁸O_Cell) of Larix Gmelinii (Rupr.) Rupr. from a wet (WS) and a dry (DS) site. These sites are characterized by different fire histories (fire in 1852 at the wet and 1896 at the dry sites, respectively). TRW and δ¹⁸OCell are identified to be the most sensitive parameters in the changing tree growth conditions after fire. The differences in the soil seasonal thermal regime of sites after fires are shown in the relationship between the studied parameters. The δ¹³C_Cell values in tree rings from the two sites are positively correlated independently of the fire impact. This fact indicates that δ¹³C_Cell chronologies might be more adequate for climatic reconstruction in the region due to the climate signal consistency. Relationships of δ¹⁸O_Cell values between the two sites are still significantly positive 60 years after the fire impact. Dendroclimatic analysis indicates significant changes in tree-ring growth and isotopic ratio responses to climate due to the increased demand of water for trees during the post-fire period (deeper seasonal subsidence of permafrost). Full article