Search Results (15)

Plants and the microorganisms living on their surfaces are an inseparable community that interacts with plant functional traits and influences plant growth, but the differences in microorganisms between plant organs and their relationship with plant functional traits have not been deeply explored. In this study, we used high-throughput sequencing to investigate the variation of microorganisms across different plant organs (leaves, twigs, trunks, and roots) of three species (Acer pictum subsp. mono, Acer tegmentosum, and Acer ukurunduense) in the Xiaoxing’an Mountains in Northeastern China and explored the relationship between microorganisms and plant functional traits. The results indicate that rhizosphere microorganisms have a high diversity. Plant organs explained 52.1% and 32.3% of the variations in bacterial and fungal community structures, respectively. The core microbiome consists of the phyla Proteobacteria and Actinobacteria in bacteria and the phyla Ascomycota and Basidiomycota in fungi. Plant functional traits such as specific leaf area and non-structural carbohydrates, as well as soil total carbon and total phosphorus content, were significantly correlated with microbial community composition. The results highlight that host plant organ characteristics are key drivers of variation in plant-associated microbial communities. By elucidating the regulatory role of host traits in microbiome assembly, our findings provide new mechanistic insights into plant–microbe interactions and ecological coexistence strategies. Full article

This study focuses on the Xiaoxing’an Mountains, examining the evolution of ecological security patterns and suggesting optimization strategies by integrating carbon storage and landscape connectivity, using multi-source data from 2000, 2010, and 2020. The study provides a comprehensive assessment of the region’s ecological security by estimating carbon stocks using the InVEST model, analyzing landscape connectivity through MSPA, and spatially extracting ecological corridors and nodes using circuit theory. The key findings are as follows: (1) High-value areas for carbon storage and landscape connectivity are primarily concentrated in the southeastern and northwestern forested mountain regions; (2) Ecological source areas are predominantly concentrated in the southeast and dispersed in the north, with the total area peaking in 2010 at 47,054.10 km²; (3) Northern ecological corridors are dense, radiating in a spider-web pattern, with pinch points concentrated at the corridor termini; southeastern corridors are sparse, mainly short, with fewer pinch points; (4) The area of ecological barriers increased by 280% over the past 20 years. Four major barrier zones were identified, all located at the junction of forest and farmland in the northwest, primarily composed of wetlands, drylands, and rural residential areas; (5) Based on the evolutionary characteristics of the Ecological Security Pattern over the past 20 years, an “axis, two belts, four zones, and multiple cores” ecological security planning framework was proposed, along with corresponding strategies. This study provides theoretical support and practical guidance for enhancing regional ecological network stability, optimizing landscape connectivity, and strengthening carbon sink functions. Full article

Brown-rot fungi are large fungi that can decompose the cell walls of wood; they are notable for their secretion of diverse and complex enzymes that synergistically hydrolyze natural wood cellulose molecules. Fomitopsis pinicola (F. pinicola) is a brown-rot fungus of interest for its ability to break down the cellulose in wood efficiently. In this study, through a combination of rDNA-ITS analysis and morphological observation, the wood decay pathogen infecting Korean pine (Pinus koraiensis Siebold and Zucc.) was identified. Endoglucanase (CMCase) and β-glucosidase were quantified using the DNS (3,5-Dinitrosalicylic acid) method, and the cellulase activity was optimized using a single-factor method and orthogonal test. The results revealed that the wood-decaying fungus NE1 identified was Fomitopsis pinicola with the ITS accession number OQ880566.1. The highest cellulase activity of the strain reached 116.94 U/mL under the condition of an initial pH of 6.0, lactose 15 g·L⁻¹, KH₂PO₄ 0.5 g·L⁻¹, NH₄NO₃ 15 g·L⁻¹, MgSO₄ 0.5 g·L⁻¹, VB₁ 0.4 g·L⁻¹, inoculated two 5 mm fungal cakes in 80 mL medium volume cultured 28 °C for 5 days. This laid a foundation for improving the degradation rate of cellulose and biotransformation research, as well as exploring the degradation of cellulose by brown rot fungi. Full article

The accurate estimation of forest above-ground biomass (AGB) is vital for monitoring changes in forest carbon sinks. However, the spatial heterogeneity of AGB, coupled with inherent uncertainties, poses challenges in acquiring high-quality AGBs. This study introduced a bias-corrected ensemble machine learning (ML) algorithm for AGB downscaling that integrated a ML for AGB mapping with another for residual mapping. The accuracies of six bias-corrected ensemble ML algorithms were evaluated at resolutions of 0.05°, 0.025°, and 0.01°. Moreover, a step-by-step downscaling (SBSD) method was introduced, utilizing bias-corrected ensemble ML algorithms to downscale AGB from 0.1° to 0.05°, 0.025°, and 0.01° resolutions and was compared with the direct downscaling (DD) at three scales. A comparative analysis was conducted in the Daxing’anling Mountains and Xiaoxing’anling Mountains. AGB and corresponding uncertainty maps at three scales were generated using SBSD. The results showed that the efficacy of the XGBoost-based AGB model combined with the random forest-based residual correction model was superior. Spatial patterns in AGB maps generated by SBSD and DD were found to be similar. Notably, SBSD yielded enhanced accuracy in the Daxing’anling Mountains with complex topography, while both performed comparably in the Xiaoxing’anling Mountains with milder topography, highlighting SBSD’s advantages in high heterogeneity areas. Full article

Land use intensity (LUI) is an important indicator for assessing human activities, and quantitatively studying the impact of LUI on ESs can help to realize the scientific management of urban ecosystems as well as sustainable development. In this study, we quantified five important ecosystem service bundles in the study area with the aid of the R-language “kohonen” package and used bivariate spatial autocorrelation modeling to examine the effects of LUI on the ESs in Harbin City from 2000 to 2020. These ESs include food supply (FP), water conservation (WC), soil conservation (SC), carbon storage (CS), water purification (WP), and habitat quality (HQ). The results show the following: (1) The LUI in Harbin City had a trend from 2000 to 2020 of “decreasing and then growing”, with a spatial distribution pattern of “high in the west and low in the east.” (2) Except for FP, all other ESs exhibit a similar spatial pattern of “west-low-east-high”; WC and WP exhibit a trend of continuous increase, SC exhibits a trend of decreasing and then increasing, and CS and HQ are generally more stable, with less fluctuation. The built-up area is situated in the high-value area of LUI, and the area exhibits a significant expansion trend. (3) Ecological conservation bundles, FP–WP synergistic bundles, ecological transition bundles, CS–WP–HQ synergistic bundles, and FP bundles are the five ecosystem service bundles that were discovered in Harbin. (4) From 2000 to 2020, there is a predominately “low LUI-high ESs” and “high LUI-low ESs” aggregation type, with a substantial positive correlation between LUI and FP and a significant negative correlation between LUI and other ESs. Harbin City should strengthen the management of ESs in the western part of the city and, at the same time, maintain the favorable ecological conditions in the ecological barriers of Zhangguangcai Range and Xiaoxing’an Mountains. Full article

Adequate seed provenance is an important guarantee for the restoration of the mixed Korean pine (Pinus koraiensis) and broadleaf forest (MKPBF). However, the commercial harvest exclusion in natural forests has led to a sharp decline in economic income from timber. Given the economic value of Korean pine seeds, predatory seed harvesting (PSH) has become increasingly serious in the past 20 years and has significantly reduced the seed and seedling bank, which might seriously threaten the restoration and sustainable management of the MKPBF. How the historical PSH has affected the future of the MKPBF is unclear at the landscape scale. In this study, we quantified the effects of seed harvesting at the landscape scale by a forest landscape model LANDIS PRO, and then assessed the legacy effects of the historical PSH on the composition and structure of the MKPBF in the Xiaoxing’an Mountains, Northeast China. Our results showed that the historical PSH decreased the Korean pine basal area of all age cohorts, with an average decrease of 0.06 to 0.19 m² ha⁻¹ but insignificantly altered the age structure diversity of Korean pine throughout the simulation. Our results indicated that the historical PSH remarkably decreased the dominance of Korean pine by 11.1%, but significantly increased the dominance of spruce (Picea koraiensis and Picea jezoensis) and fir (Abies nephrolepis) by 3.8% and 4.5%, respectively, and had an insignificant effect on the other tree species over the simulation. We found that the historical PSH evidently changed the succession trajectories of the disturbed stands, which would result in the transition from the succession pattern dominated by Korean pine to that dominated by spruce and fir. The historical PSH decreased the importance value of Korean pine by 12.2% on average but increased it by 5.1% and 6.0% for spruce and fir, respectively, and resulted in an average 33.2% increase in the dissimilarity index compared with the initial state during the whole simulation period. Future forest management should strictly limit the intensity and rotation of seed harvesting to protect the seed provenance of Korean pine and consider how to ensure the recovery and sustainable management of the MKPBF through direct seeding or seedling planting. Full article

Nitrogen (N) deposition has increased in recent years and is significantly affected by global change and human activities. Wetlands are atmospheric CH₄ and N₂O sources and may be affected by changes in N deposition. To reveal the effects of increased N deposition on peatland greenhouse gas exchange, we observed the CH₄ and N₂O emissions from controlled microcosms collected from a temperate peatland in the Xiaoxing’an mountains, Northeast China. We found that the moss biomass did not change, but the total herb biomass increased by 94% and 181% with 5 and 10-times-higher N deposition, respectively. However, there were no significant changes in CH₄ emissions from the microcosms with N addition. The unchanged CH₄ emissions were mainly caused by the opposite effect of increased nitrate and ammonium concentrations on soil CH₄ production and the increased plant biomass on CH₄ emission. We also found that the manipulated microcosms with 5 and 10-times-higher N deposition had 8 and 20-times-higher seasonal average N₂O emissions than the control microcosms, respectively. The increased N₂O emissions were mainly caused by short-term (≤7 d) pulse emissions after N addition. The pulse N₂O emission peaks were up to 1879.7 and 3836.5 μg m⁻² h⁻¹ from the microcosms with 5 and 10-times-higher N deposition, respectively. Nitrate and ammonium concentrations increasing in the soil pore water were the reason for the N₂O emissions enhanced by N addition. Our results indicate that the increase in N deposition had no effects on the CH₄ emissions but increased the N₂O emissions of the temperate peatland. Moreover, pulse emissions are very important for evaluating the effect of N addition on N₂O emissions. Full article

The effects of pre-hardening fertilization and autumn fertilization on seedling growth have been studied separately, but studies on their combined effects are relatively scarce. We studied the effects of pre-hardening fertilization type and autumn fertilization level on biomass allocation and root morphology of container-grown seedlings of Korean pine (Pinus koraiensis Sieb. et Zucc.), a valuable evergreen conifer distributed from Changbai Mountain to the Xiaoxing’an Mountains in northeastern China. Three pre-hardening fertilization types (conventional fertilization, exponential fertilization, and controlled-release fertilizer) were all applied with 72 mg of nitrogen. We also applied four nitrogen levels of autumn fertilization: 0 mg/plant, 2 mg/plant, 4 mg/plant, and 6 mg/plant. We found that autumn fertilization increased Korean pine seedling biomass accumulation and root growth by 65.91%–92.15% and 108.86%–141.48%, respectively. There was significant interaction between pre-hardening fertilization type and autumn fertilization level on biomass allocation and root morphology. Seedlings with conventional fertilization during the growing season have the best response to autumn fertilization, particularly in the 2 mg/seedling and 4 mg/seedling treatments. Autumn fertilization can be applied to the cultivation of high-quality Korean pine seedlings. Full article

Under the trend of climate warming, the high-latitude permafrost in Heilongjiang Province is becoming seriously degraded. The question of how to quantitatively analyze the spatial and temporal trends of multi-year permafrost has become fundamental for current permafrost research. In this study, the temporal and spatial variations of annual mean air temperature (MAAT), annual mean ground temperature (MAGST) and freezing/thawing index based on air and surface temperature data from 34 meteorological stations in Heilongjiang Province from 1971–2019, as well as the variation characteristics of permafrost distribution, were analyzed based on the freezing index model. The results showed that both MAAT and MAGST in Heilongjiang Province tended to decrease with the increase of altitude and latitude. For interannual variation, the MAAT and MAGST warming rates tended to be consistent across Heilongjiang Province, with multi-year variation from −8.64 to 5.60 °C and from −6.52 to 7.58 °C, respectively. From 1971–2019, the mean annual air freezing index (AFI) and ground surface freezing index (GFI) declined at −5.07 °C·d·a⁻¹ and −5.04 °C·d·a⁻¹, respectively, whereas the mean annual air thawing index (ATI) and ground surface thawing index (GTI) were elevated at 7.63 °C·d·a⁻¹ and 11.89 °C·d·a⁻¹, respectively. The spatial distribution of the multiyear mean AFI, ATI, GFI and GTI exhibited a latitudinal trend, whereas the effect of altitude in the northern mountainous areas was greater than that of latitude. Permafrost was primarily discovered in the Daxing’an and Xiaoxing’an Mountains in the north, and sporadically in the central mountainous regions. The southern boundary of permafrost shifted nearly 2° to the north from 1970 to 2010s, while the southern boundary of permafrost in Heilongjiang Province was stable at nearly 51° N. The total area of permafrost narrowed from 1.11 × 10⁵ km² in the 1970s to 6.53 × 10⁴ km² in the 2010s. The results of this study take on a critical significance for the analysis of the trend of perennial permafrost degradation at high latitudes in Heilongjiang Province and the whole northeastern China, as well as for mapping the distribution of large areas of permafrost using the freezing index model. This study provides a reference for natural cold resource development, ecological protection, climate change and engineering construction and maintenance in permafrost areas. Full article

Affected by global warming, methane gas released by permafrost degradation may increase the frequency of wildfires, and there are few studies on wildfires in permafrost regions and their correlation with climate and regional methane emissions. The northwestern section of the Xiaoxing’an Mountains in China was selected as the study area, and the spatial relationship between permafrost and spring wildfires was studied based on Landsat TM and Sentinel-2 data. Combined with monitoring data of air temperature, humidity, and methane concentration, the impact of methane emissions on spring wildfires was analyzed. The study shows that the spatial distribution of fire scars in spring is highly consistent with permafrost, and the change trend of fire scars is in line with the law of permafrost degradation. Wildfires occur intensively during the snow melting period in spring, and the temporal variation pattern is basically consistent with the methane concentration. The number of fire points was positively correlated with air temperature and methane concentration in March and April, and spring wildfires in permafrost regions are the result of a combination of rising seasonal temperatures, surface snow melting, and concentrated methane emissions. Larger areas of discontinuous permafrost are more prone to recurring wildfires. Full article

Understanding terrestrial water storage (TWS) dynamics and associated drivers (e.g., climate variability, vegetation change, and human activities) across climate zones is essential for designing water resources management strategies in a changing environment. This study estimated TWS anomalies (TWSAs) based on the corrected Gravity Recovery and Climate Experiment (GRACE) gravity satellite data and derived driving factors for 214 watersheds across six climate zones in China. We evaluated the long-term trends and stationarities of TWSAs from 2004 to 2014 using the Mann–Kendall trend test and Augmented Dickey-Fuller stationarity test, respectively, and identified the key driving factors for TWSAs using the partial correlation analysis. The results indicated that increased TWSAs were observed in watersheds in tropical and subtropical climate zones, while decreased TWSAs were found in alpine and warm temperate watersheds. For tropical watersheds, increases in TWS were caused by increasing water conservation capacity as a result of large-scale plantations and the implementation of natural forest protection programs. For subtropical watersheds, TWS increments were driven by increasing precipitation and forestation. The decreasing tendency in TWS in warm temperate watersheds was related to intensive human activities. In the cold temperate zone, increased precipitation and soil moisture resulting from accelerated and advanced melting of frozen soils outweigh the above-ground evapotranspiration losses, which consequently led to the upward tendency in TWS in some watersheds (e.g., Xiaoxing’anling mountains). In the alpine climate zone, significant declines in TWS were caused by declined precipitation and soil moisture and increased evapotranspiration and glacier retreats due to global warming, as well as increased agriculture activities. These findings can provide critical scientific evidence and guidance for policymakers to design adaptive strategies and plans for watershed-scale water resources and forest management in different climate zones. Full article

Affected by global warming, permafrost degradation releases a large amount of methane gas, and this part of flammable methane may increase the frequency of wildfires. To study the influence mechanism of methane emission on wildfires in degraded permafrost regions, we selected the northwest section of Xiaoxing’an Mountains in China as the study area, and combined with remote sensing data, we conducted long-term monitoring of atmospheric electric field, temperature, methane concentration, and other observation parameters, and further carried out indoor gas–solid friction tests. The study shows that methane gas (the concentration of methane at the centralized leakage point is higher than 10,000 ppm) in the permafrost degradation area will release rapidly in spring, and friction with soil, surface plant residues, and water vapor will accelerate atmospheric convection and generate electrostatic and atmospheric electrodischarge phenomena on the surface. The electrostatic and atmospheric electrodischarge accumulated on the surface will further ignite the combustibles near the surface, such as methane gas and plant residues. Therefore, the gradual release of methane gas into the air promotes the feedback mechanism of lightning–wildfire–vegetation, and increases the risk of wildfire in degraded permafrost areas through frictional electrification (i.e., electrostatic and atmospheric electrodischarge). Full article

Permafrost thawing may lead to the release of carbon and nitrogen in high-latitude regions of the Northern Hemisphere, mainly in the form of greenhouse gases. Our research aims to reveal the effects of permafrost thawing on CH₄ and N₂O emissions from peatlands in Xiaoxing’an Mountains, Northeast China. During four growing seasons (2011–2014), in situ CH₄ and N₂O emissions were monitored from peatland under permafrost no-thawing, mild-thawing, and severe-thawing conditions in the middle of the Xiaoxing’an Mountains by a static-chamber method. Average CH₄ emissions in the severe-thawing site were 55-fold higher than those in the no-thawing site. The seasonal variation of CH₄ emission became more aggravated with the intensification of permafrost thawing, in which the emission peaks became larger and the absorption decreased to zero. The increased CH₄ emissions were caused by the expansion of the thawing layer and the subsequent increases in soil temperature, water table, and shifts of plant communities. However, N₂O emissions did not change with thawing. Permafrost thawing increased CH₄ emissions but did not impact N₂O emissions in peatlands in the Xiaoxing’an Mountains. Increased CH₄ emissions from peatlands in this region may amplify global warming. Full article

The mixed forest of broad-leaved and Korean pine is the dominant type in the Xiaoxing’an and Changbai Mountains of China. However, few studies have been done on its canopy interception of rainfall. In this study, rainfall amount, rainfall intensity, and canopy interception were monitored during the growing seasons in 2010 and 2011. The results showed that cumulative canopy interception of rainfall was 22.0% and 21.9% in 2010 and 2011, respectively. However, the canopy interception of rainfall varied with rainfall events from 6.6% to 82.7% in 2010, and from 8.7% to 80.2% in 2011. The relationship between rainfall amount and the ratio of canopy interception to rainfall amount could be described by a power function (P < 0.01), i.e., the canopy interception decreased with the increasing rainfall amount and intensity. These results indicate that the rainfall amount and intensity were important factors for estimating the canopy interception of the studied forest type. Full article

A comprehensive set of 30-m resolution land coverage data of 2000 and 2010 was used for an analysis of the spatial heterogeneity of forest area change in early 21st century China. Four regression models were built to determine the current situation of the ‘forest transition’ in China. The results show that forest area in China has grown rapidly over this period such that total forest area has increased by 102,500 km² and forest cover has increased by 1.06%. Our results demonstrate the presence of a ‘U-shaped’ relationship, the so-called ‘forest transition’, between forest area change and per capita gross domestic product (GDP). We estimate that the inflection point in the Chinese ‘forest transition’ will be at a per capita GDP of 50,522 yuan. In the future, regions with lower elevations, or slope, should be the focus of attention because of dramatic recent forest changes. In particular, forest areas in the regions of the Xiaoxing’anling-Changbaishan Mountains and in South China have markedly decreased, and these are areas of concern. In the meantime, the government needs to strengthen the management of large-scale interconversions between forest and grassland. Full article