Great Xing Research Articles

Community biomass accumulation benefits from flexible plant nutrient homeostasis after wildfire

As an essential part of the stoichiometric flexibility in regulating the relative tissue contents of nitrogen (N) or phosphorus (P), their homeostasis (H) could determine plant growth under changing nutrient environments, such as under wildfire disturbance. Although a growing number of studies have suggested a coupling relationship between plant nutrient H and species abundance, how leaf N and P homeostasis (HN and HP) regulates the accumulation of community biomass remains unclear, especially in nutrient-fluctuating burned areas. We measured leaf N and P concentrations and total biomass of all species and the soil N and P concentrations across 15 forest plots at four recovery periods (2, 10, 20, and 30 years after burning) with low-severity wildfire and one unburned treatment (>80 years after burning) in boreal forests and associated the community-level HN and HP with biomass accumulation in the Great Xing’an Mountains, China. We found that the HN of trees peaked 20 years after burning under N limitation conditions, and the HP of shrubs approached a maximum at 10 years after burning due to P limitation. It is worth noting that the biomass of trees and herbs was significantly positively correlated with HN, while negative relationships between HP and biomass were shown in trees. Nutrient H explained 59% of the total variation in community biomass, and the joint effect of HN and HP mainly contributed to the biomass accumulation of trees (43.5%) and shrubs (68.5%), respectively. These findings greatly improve the theoretical foundation for understanding how plant nutrient H is associated with biomass accumulation after wildfire. Flexible nutrient H in woody plants highlights the vital role of understory woody species in postfire forest management. Therefore, clearly understanding the relationship between nutrient H and carbon sequestration is essential for a thorough assessment of postfire forest sustainability.

Fossil divergent double-subduction zone in the Great Xing’an Range, NE China: Evidence from a deep seismic reflection profile

Divergent double-subduction is an important component of plate tectonics and continental growth at modern active convergent margins. However, such a process is rarely identified by deep seismic reflection (DSR) profiles, which casts doubt on its past significance. We report here a 416 km DSR profile of large dynamite shots across the Great Xing’an Range (NE China), which shows multiple arc-shaped reflections in the upper-middle crust of the Xing’an terrane, and densely layered reflection structures suggesting tectonic nappes in the lower crust. This new evidence, together with recent geological studies, indicates that the Xing’an terrane may not be a micro-continental block as previously thought, but a Paleozoic accretionary complex. In addition, there is a strong west-dipping reflection at the boundary between the Xing’an and Erguna terranes in the western DSR profile extending from the lower crust to the lithospheric mantle, suggesting that this fossil subduction zone is most likely the Toudaoqiao-Xinlin suture, which separates the Xing’an and Erguna terranes. In addition, an east-dipping strong reflection was also found in the eastern profile between the Xing’an and Songliao terranes, corresponding to the Hegenshan-Nenjiang suture at the surface. Given the newly identified crust-mantle structure, the opposite subduction zone, and other geological evidence, we propose a new model that the Xing’an terrane was developed by divergent double-subduction of the Paleo-Xing’an Ocean (part of the Paleo-Asian Ocean in the area) from ca. 500 Ma to ca. 300 Ma. Our study provides the first DSR evidence for a divergent double-subduction in the Paleozoic, which emphasizes its importance in past accretionary orogens.

Undulating electrical lithosphere–asthenosphere boundary beneath Northeast China; as revealed by long–period magnetotelluric data

The geometry of continental lithosphere–asthenosphere boundary (LAB) significantly affects the movements of tectonic plates and flow of the upper mantle. However, the properties and geometry of this boundary beneath tectonically active regions in Phanerozoic continents are mysterious and elusive. Ninety–three long–period magnetotelluric (LMT) observations across Northeast China (NEC) provide a unique opportunity to image the shape of the LAB. Probabilistic resistivity–depth model inversion was employed to obtain the one–dimensional resistivity structure beneath each LMT site. The depth of the electrical LAB is constrained by the most probable interface at which the resistivity changes rapidly from high to low. The inversion results show that the electrical LAB is undulating beneath NEC. The North–South Gravity Lineament marks the transition from deep to shallow LAB. The thickest lithosphere occurs beneath the Great Xing'an Range (GXAR), where the LAB is ∼200 km deep. The electrical lithosphere is relatively thin in the east, with the thinnest lithosphere (∼50 km) being found beneath the Changbai Mountain volcano. We speculate that melt depletion, together with possible mantle downwelling are the likely causes for the formation of the thick GXAR lithosphere. The unresolved lithosphere beneath the northern Songliao Basin could be ascribed to the strong attenuation of electromagnetic waves in highly conductive sedimentary layers or the weak difference in the resistivity of the lithosphere and asthenosphere. The lithosphere steps that can form the edge-driven convection in the asthenosphere may play key roles in forming the widely-spread intraplate magmatism in NEC.

Formation and evolution of multistage hydrothermal fluids in the Baishitouwa quartz–wolframite vein‐type deposit in the southern Great Xing'an Range tungsten belt, NE China: Constraints from individual fluid inclusion LA‐ICP‐MS analysis

Revealing hydrothermal evolution from the early oxide to late carbonate stages for quartz–wolframite vein‐type deposits is essential for understanding the ore‐forming process. In this study, we choose the Baishitouwa tungsten polymetallic deposit located in the southern Great Xing'an Range tungsten belt as a case study, and present detailed deposit geology and in situ fluid inclusion (FI) analyses including microthermometry, laser Raman spectra, and LA‐ICP‐MS microanalysis to address this issue. Four stages of hydrothermal activity were identified: (1) quartz–wolframite (I), (2) quartz–wolframite (II)–pyrite–chalcopyrite, (3) quartz–polymetallic sulphides, and (4) quartz–carbonate. Four types of FIs were recognized: CO2‐rich, CO2‐bearing, liquid‐rich, and brine inclusions. Microthermometric data showed that the homogenization temperatures and salinities from the early to late stages are 380–460°C, 7.4–17.3, and 29.3–43.2 wt% NaCl equiv., 300–390°C and 7.1–17.0 wt% NaCl equiv., 220–320°C and 2.7–8.1 wt% NaCl equiv., and 150–250°C and 0.5–4.8 wt% NaCl equiv., respectively, suggesting a decreasing trend. Geochemically, all stage fluids contained high Rb and Mn concentrations, high Rb/Na, Cs/Na, Li/Na, K/Na, Rb/Sr, low K/Rb, and consistent Cs/Rb and Cs/(Na + K) ratios, indicating that the mineralizing fluids originated from a common source—an underlying, geochemically uniform, and highly fractionated granitic magma. Fluid immiscibility and cooling are the main mechanisms for wolframite precipitation, whereas greisenization is subordinate; the incursion of meteoric water into the hydrothermal system initiated at the sulphide stage, and fluid mixing is the dominant mechanism for sulphide precipitation.

Fluid evolution and ore genesis of the A'gui Cu deposit in southern Great Xing'an Range, Northeast China: Evidence from fluid inclusion and C–H–O–S–Pb isotopes

The A'gui Cu deposit is located in the eastern slope of the southern Great Xing'an Range (SGXR), and it is a vein-type Cu deposit spatially and temporally related to the Cretaceous monzogranite which intruded Pingshan Formation. Vein-type Cu orebodies are mainly hosted in the NE and nearly EW faults. Previous studies on the A'gui deposit mainly focused on geological exploration, and there was no study on its fluid evolution and genesis. Therefore, we carried out conducted fluid inclusion and stable isotope (C–H–O–S–Pb) analysis to study the fluid evolution, fluid and ore-forming material sources and genesis of the A'gui deposit. According to the field investigations and mineral crosscutting relationships, four paragenetic stages were identified: quartz–pyrite–chalcopyrite–pyrrhotite–arsenopyrite ± magnetite (Stage I), quartz–pyrite–chalcopyrite (Stage II), quartz–chalcopyrite ± pyrite–sphalerite–galena (Stage III) and carbonate ± quartz (Stage IV). From Stage I to Stage II, the assemblage of fluid inclusions (FIs) in quartz is characterized by the development of daughter mineral–bearing three–phase FIs (SL–type), vapour FIs (V–type), vapour–rich two–phase aqueous FIs (LV–type) and liquid–rich two–phase aqueous FIs (VL–type). Only VL–type FIs appeared in the Stage III quartz and Stage IV calcite. The homogenization temperatures of FIs in stages I, II, III and IV are 329–390 °C, 255–336 °C, 166–244 °C and 120–157 °C, with salinities of 3.37–45.33 wt%, 3.53–39.76 wt%, 4.17–7.86 wt% and 3.37–7.15 wt% NaCl eqv., respectively. The fluid inclusion type assemblage suggested that obvious fluid boiling occurred in the Stage I and Stage II. Fluid boiling may be the reason for the precipitation of useful minerals. According to the HO isotope analysis of stages I–II quartz (δ18OH2O = −2.1 to 3.2 ‰, δDV–SMOW = −128.4 ‰ to −110.6 ‰), the fluid was originally magmatic water. From Stage III to Stage IV (δ18OH2O = −12.3 to −2.3 ‰, δDV–SMOW = −129.6 ‰ to −104.2 ‰), the HO isotope value is obviously close to the meteoric water line, indicating that meteoric water is mixed with evolved magmatic solutions. The ore–forming fluid of the A'gui deposit represents a medium–high temperature NaCl-H2O magmatic hydrothermal system. The C isotope compositions (δCV–PDB = −5.74 ‰ to −4.76 ‰) in stage IV indicate that the C in the fluid was derived from a magmatic source and was affected by meteoric water. In addition, the measured S isotope compositions in stages I–III of the hydrothermal fluids (δ34SV–CDT = 2.2 to 3.7 ‰) indicate that S mainly comes from granitic magma. Further, the Pb isotope (206Pb/204Pb = 18.276–18.367, 207Pb/204Pb = 15.52–15.556, 208Pb/204Pb = 38.157–38.193) in stages I–III indicate that the ore-forming materials are derived from the mixture of mantle and orogenic material. In summary, this study showed the A'gui is a typical magmatic hydrothermal vein-type Cu deposit that related to Cretaceous monzogranite formed under the joint constraints of Mongolia-Okhotsk Ocean and Paleo-Pacific Ocean tectonic system. Fluid boiling and mixing are the main ore-forming mechanism.

Hydrothermal conditions of southern and northern slope soils of northeastern Great Xing'an Mountain, China

The purpose of the article is to study the influence features of polar-oriented slopes on the near-surface energy and hydrothermal balance in the seasonal cryolithozone. The authors carried out a complex of field observations including measurement of air and underlying surface temperature, soil moisture, solar radiation and wind speed at the hydrological stations of Songling (southern slope) and Luoguhe (northern slope) in the northeast of the Great Xing'an Mountain (China). The analysis of the data obtained allowed to conclude that, on the one hand, the long-term influence of the thermal balance components causes significant differences in the soil structure and properties on differently oriented slopes. The number of daily freeze-thaw soil cycles on the southern slope (100 cycles) significantly exceeds the ones on the northern slope (56 cycles). The soil on the southern soil is 3 °C warmer than that on the northern slope, and its humidity in the area of the Songling hydrological station is lower than that at the Luoguhe station. On the other hand, differences in soil properties control the energy exchange between the atmosphere and the earth's surface, this means that the incoming short-wave solar radiation and heat flux into the soil on the southern slope is greater than on the northern one. Therefore, slope orientation is one of the significant environmental factors affecting the influx of solar energy, temperature and humidity of the soils in the northeastern Great Xing'an Mountain. It also has a decisive role for the spatial distribution and evolution of seasonal permafrost in the region and, accordingly, affects the stability and safety of engineering structures. The performed research is important for understanding the relationship between climate and frozen soil in the mountainous areas with seasonal cryolithozone as well as for optimization of boundary conditions when modeling rock freeze-thaw processes.

Evaluations on the Consequences of Fire Suppression and the Ecological Effects of Fuel Treatment Scenarios in a Boreal Forest of the Great Xing’an Mountains, China

With global warming, catastrophic forest fires have frequently occurred in recent years, posing a major threat to forest resources and people. How to reduce forest fire risk is a hot topic in forest management. Concerns regarding fire suppression and forest fuel treatments are rising. Few studies have evaluated the ecological effects of fuel treatments. In this study, we used the LANDIS PRO model to simulate the consequences of fire suppression and the ecological effects of fuel treatments in a boreal forest of the Great Xing’an Mountains, China. Four simulation scenarios were designed, focusing on whether to conduct fuel treatments or not under two fire-control policies (current fire suppression policy and no fire suppression policy). Each scenario contains nine fuel treatment plans based on the combinations of different treatment methods (coarse woody debris reduction, prescribed burning, coarse woody debris reduction plus prescribed burning), treatment frequency (low, medium, and high), and treatment area (large, medium, and small). The ecological effects of the fuel treatments were evaluated according to the changes in fire regimes, species succession, and forest landscape patterns to find a forest fuel management plan that is suitable for the Great Xing’an Mountains. The results showed that long-term fire suppression increases fuel loads and the probability of high-intensity forest fires. The nine fuel management plans did not show significant differences in terms of species succession and forest landscape patterns while lowering forest fire intensity, and none of them were able to restore historical vegetation structure and composition. Our results consolidate the foundation for the practical performance of forest fuel treatments in fire-prone forest landscapes. We suggest a suitable fuel treatment plan for the Great Xing’an Mountains, with a low treatment frequency (20 years), large treatment area (10%), and coarse woody debris reduction, plus the prescribed burning measure.

Burned vegetation recovery trajectory and its driving factors using satellite remote-sensing datasets in the Great Xing’An forest region of Inner Mongolia

Forest fire is one of the most important factors that alter a forest ecosystem’s biogeochemical cycle. Large-scale distributed burned areas lose their original vegetation structure and are more impacted by climate change in the vegetation recovery process, thus making it harder to restore their original vegetation structure. In this study, we used historical Landsat imagery and the LandTrendr algorithm in the Google Earth Engine platform to study and identify post-fire stages in the Great Xing’An Range of Inner Mongolia. Moreover, we categorized different post-fire vegetation recovery trajectories. The usefulness of spectral indices was also evaluated in the study region. We applied the Geodetector model to analyze the driving factors of the burned area vegetation regeneration process. The results show that burn severity and earth–atmosphere hydrological cycle are two main impacting factors in the short term after the fire (e.g. 5–6 years). Other climatical conditions affect vegetation recovery, including prolonged vegetation recovery process, hydrothermal circulation process and topographical conditions, seasonally frozen soil, freeze–thaw processes, and climate events. This study improves understanding of the dynamic successional processes in the burned area and the driving factors. Also, the outcomes can facilitate and support sustainable forest management of the Great Xing’An Range.

Deposit types, metallogenesis and resource prospect of Li-Be-Nb-Ta deposits in the Great Xing'an Range

Deposit types, metallogenesis and resource prospect of Li-Be-Nb-Ta deposits in the Great Xing'an Range

Cassiterite U-Pb age, fluid inclusion and H-O-S-Pb isotope geochemistry of the Xiaogushan Sn-Zn deposit in the southern Great Xing'an Range, NE China

Cassiterite U-Pb age, fluid inclusion and H-O-S-Pb isotope geochemistry of the Xiaogushan Sn-Zn deposit in the southern Great Xing'an Range, NE China

基于“目标-成本-效益”协同优化的山水林田湖草沙一体化生态保护与修复格局

PDF HTML阅读 XML下载 导出引用 引用提醒 基于“目标-成本-效益”协同优化的山水林田湖草沙一体化生态保护与修复格局 DOI: 10.5846/stxb202210022802 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(32171572) Optimization of integrated ecological conservation and restoration pattern by trading off the targets, costs, and ecological benefits Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:当前以"山水林田湖草沙一体化保护与修复"为代表的国土空间生态修复工程已在全国范围内陆续开展,但相关规划的理论和方法支撑仍较为薄弱,如何确定合理的保护修复目标,并对生态保护与修复格局进行整合优化,是实现山水林田湖草沙一体化保护与修复规划需要解决的关键问题。基于系统保护规划理论和方法,初步构建了基于"目标-成本-效益"协同优化的一体化保护修复规划构架,以大兴安岭中段嫩江-哈拉哈河源头区为例,依托空间优化模型(Marxan)对一体化保护修复格局进行了优化模拟,结果表明:(1)绰尔河流域的生态系统保护优先级最高,其次是哈拉哈河流域和洮儿河流域,最后是霍林河流域。当预算不足时,优先保护绰尔河流域可以最大限度的提升研究区内的生态系统服务功能;(2)当优化目标低于50%,优化格局中以林地保护和草地保护为主,需要修复格局规模较小,当优化目标比例超过50%,需要采取生态修复的面积明显增加。随着优化目标比例的提升,优化格局所需面积越来越大,优化后区域中各类生态系统服务功能均有所提高;(3)依据目标-成本-效益曲线,60%的保护修复水平(即1980-2020年退化损失的生态系统服务的60%)为最高效的保护修复目标,所需生态保护修复总成本为50.6亿,但产生的生态效益可达为66.4亿;(4)60%目标水平下,需要林地、草地和湿地保护面积分别为20400.27 km2、11919.45 km2和25.23 km2;林地、草地和湿地修复面积分别为272.18 km2、1695.23 km2和3.71 km2,分别占1980-2020年期间林地、草地和河湖湿地退化消失比例40.9%、23.5%和6.3%。本研究提出的一体化生态保护修复格局整合优化方法可以确定不同目标和成本约束下,获取最佳综合生态效益的生态保护与修复实施策略和优化布局,为山水林田湖草沙一体化生态保护修复规划相关理论和方法提供一定的科学支撑。 Abstract:Although Terrestrial Ecological Restoration (TER) projects have been advocated and carried out across the China's mainland in recent years, the underlying scientific theory and methodology are still urgently needed to reduce uncertainties in target setting, site selection for conservation & restoration, and cost-benefit evaluation. How to determine reasonable conservation and restoration objectives and to integrate and optimise ecological conservation and restoration patterns are key issues that need to be addressed in order to achieve Terrestrial Ecological Restoration.This paper initially attempted to develop a theoretic and methodological TER framework for integrating conservation and restoration pattern based on the principle of Systematic Conservation Planning, demonstrating by a case study in the central part of the Great Xing'an Mountains. The results show that: (1) The Chao'er River Basin exhibited the highest conservation priority, followed by the Halaha and Taoer river basins, hence prioritizing conservation of Chao'er River Basin could maximize ecosystem services in case of insufficient budget. (2) When the target setting was below 50% (i.e., mitigating 50% of the loss in total ecosystem service during 1980-2020), the prioritized pattern would mainly focus on forestland & grassland ecosystem conservation with a small-scale restoration pattern. With the target level exceeding 50%, the area needed to be restored would increase significantly. With the proportion of targets for optimisation increased, the area required to optimise the pattern became larger, and ecosystem services were improved in the optimised area compared to the current situation.(3) According to the target-cost-benefit curve, the optimized target level was identified at 60% for the ecosystem conservation and restoration in the central part of the Great Xing'an Mountains (i.e., making up 60% of the total ecosystem service lost during 1980-2020). (4) Under the target level of 60%, the cost of conservation and restoration was 5.06 billion yuan, and the ecological benefits generated were 6.64 billion yuan. The prioritized area of forestland, grassland and wetland to be conserved were identified at 20400.27 km2, 11919.45 km2, and 25.23 km2. The prioritized area of forestland, grassland, and wetland to be restored were identified at 272.18 km2,1695.23 km2, and 3.71 km2, accounting for 40.9%, 23.5%, and 6.3% of potential restorable forestland, grassland and riverine & lacustrine wetlands (i.e., areal loss between 19802020), respectively. Based on trading off "target-cost-benefit", this integrated conservation and restoration planning provides an operational framework to measure priorities between conservation and restoration actions, and highlights the necessity to optimize allocation of limited resources by integrating the two approaches cost-efficiently. 参考文献 相似文献 引证文献

Satellite-Based Analysis of Spatiotemporal Wildfire Pattern in the Mongolian Plateau

Burned area is a critical input to biomass burning carbon emissions algorithms and for understanding variability in fire activity due to climate change. This study presents the spatial and temporal patterns of wildland fires in the Mongolian Plateau (MP) using Collection 6 NASA MCD64A1 500 m global Burned Area product from 2001 to 2021. Both inter- and intra-annual fire trends and variations in two subregions, Mongolia and China’s Inner Mongolia, were analyzed. The results indicated that an average area of 1.3 × 104 km2 was consumed by fire per year in the MP. The fire season has two peaks: spring (March, April, and May) and autumn (September, October, and December). The profiles of the burnt area for each subregion exhibit distinct seasonality. The majority of wildfires occurred in the northeastern and southwestern regions of the MP, on the border between Mongolia and China. There were 2.7 × 104 km2 of land burned by wildfires in the MP from 2001 to 2021, 57% of which occurred in spring. Dornod aimag (province) of Mongolia is the most fire-prone region, accounting for 51% of the total burned area in the MP, followed by Hulunbuir, at 17%, Sukhbaatar, at 9%, and Khentii at 8%. The changing patterns of spatiotemporal patterns of fire in the MP were analyzed by using a spatiotemporal cube analysis tool, ArcGIS Pro 3.0.2. The results suggested that fires showed a decreasing trend overall in the MP from 2001 to 2021. Fires in the southern region of Dornod aimag and eastern parts of Great Xing’an Mountain showed a sporadic increasing trend. Therefore, these areas should be priorities for future fire protection for both Mongolia and China.

Tin mineralization in the giant Shuangjianzishan Ag-Pb-Zn deposit, Inner Mongolia

The newly discovered Shuangjianzishan giant Ag-Pb-Zn deposit which located in the Southern segment of the Great Xing’an Range (SGXR), has controlled more than 18 000 t reserves of Ag, 1.9 Mt reserves of Zn, and 3.3 Mt reserves of Pb. Previous research has shown that Shuangjianzishan is a typical epithermal Ag-Pb-Zn deposit, however, mid- to high-temperature Cu-Sn (-W) mineralization are few studies. In this paper, a detailed mineralogical study reveals that a remarkable Cu-Sn (-W) mineralization is observed both in the upper tunnel and the deeper drill core samples. In the shallow ore-bodies, tin dominantly occurs as canfieldite in Pb-Zn-rich ores, minor as cassiterite-quartz veinlets. In the deep drill cores, tin occurs as cassiterite in the Cu-rich ores with the assemblage of quartz-arsenopyrite-chalcopyrite-stannite-(wolframite). Four primary paragenetic stages have been recognized. Stage I: cassiterite-quartz-arsenopyrite-chalcopyrite, including two sub-stage: cassiterite-arsenopyrite-pyrrhotite-quartz (stage I1) and sphalerite-chalcopyrite-galena-pyrite (stage I2); Stage II: galena-sphalerite-silver minerals; Stage III: Quartz-silver minerals, and stage IV: pyrite-carbonate.Electron probe micro-analysis (EPMA) show that the early mineralization (stage I) is characterized by Fe-rich sphalerite, Co-rich pyrite, Se-rich canfieldite, and Se-Bi-rich galena, while the later mineralization (stage II-IV) contains Fe-depleted sphalerite, As-rich pyrite, and Sb-bearing silver minerals. Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis show that cassiterite has high contents of W, Fe, Sb, and Ti and depleted in Nb and Ta. Mineral associations and compositions implies a cassiterite-sulfide type tin mineralization in the Shuangjianzishan Ag-Pb-Zn deposit.A concealed granite porphyry intrusion was exposed in deep drill cores in the northwest part of the ore-field, with zircon U-Pb ages of (137.8 ± 1.1) Ma and (136.8 ± 1.0) Ma for fine- and coarse-grains granite, respectively. Bulk analysis shows that concealed granites are characterized by a highly fractionated, relatively reduced, and high K-calc-alkaline to alkaline, which belongs to A-type granites, and the remnant of Sn-bearing titanite suggests that it has the potential to provide the source of tin. Zircon U-Pb age (138–130 Ma) is well coupled with the previous data (ore-forming age, 136–129 Ma) of Shuangjianzishan, suggesting a close temporal and genetic relationship between tin mineralization and emplacement of the granite. This contribution implies that the Shuangjianzishan deposit may exist a middle- to high-temperature Cu-Sn (-W) mineralization center rather than a simple low-temperature hydrothermal system, and shows there is significant Sn-Cu mineralization potential in the peripheral and root zone of ore district.

Tree rings reveal changes in the temperature pattern in eastern China before and during the Anthropocene

A comprehensive understanding of the spatial characteristics of warming trends and temperature variability is important given global warming. Paleoclimate reconstruction has played an important role in evaluating warming and extreme climactic events in recent decades. Using the ring width of Pinus tabulaeformis, we reconstructed the ground surface temperature changes at Mengshan Mountain, in the central part of eastern China (EC), from 1667 to 2019. There were 3 extremely low-temperature years, 42 low-temperature years, 256 normal years, 37 high-temperature years and 15 extremely high-temperature years over the past 353 years. High and extremely high temperatures mainly occurred in the first half of the 19th century, the end of the 20th century and the beginning of the 21st century; low and extremely low temperatures occurred in almost all periods except for the last 50 years. By combining the past temperature reconstructions from the Great Xing’an Mountains in northern EC and Taiwan in southern EC, we also found that after the start of the Anthropocene, there were strong positive correlations among the temperatures of the northern, central and southern parts of EC. However, before the Anthropocene, these correlations were weak, and there was even a significant negative correlation during some periods. Additionally, the temperature in EC exhibited different change patterns before and during the Anthropocene. Before the Anthropocene, the temperature in southern EC showed an upward trend; in central EC, the temperature first rose and then began to decline in the 1820s; there was no obvious trend in the temperature changes in northern EC. The spatial consistency of temperature changes during the Anthropocene might be related to the fact that greenhouse gases emitted by human activities diffuse evenly withatmospheric circulation and absorb longwave radiation to directly heat the atmosphere.

Multiple fluid sources in skarn systems: Oxygen isotopic evidence from the Haobugao Zn-Fe-Sn deposit in the southern Great Xing’an Range, NE China

Abstract Diverse fluid sources and complex fluid flow paths in skarn systems appear to be well documented. Nevertheless, in situ microanalysis of oxygen isotopes by secondary ion microprobe (SIMS) in skarn minerals can provide further high spatial resolution information on this complexity and the formation of skarns and associated ore deposits. In this study, we investigated the Haobugao skarn Zn-Fe-Sn deposit (0.36 M tonnes Zn) in the southern Great Xing’an Range, northeast (NE) China, and the associated Early Cretaceous Wulanba biotite granite. Based on drill hole logging, four early skarn phases are recognized: proximal red-brown garnet-hedenbergite exoskarn, central green garnet exoskarn, light brown garnet-diopside exoskarn, and distal pyroxene skarn. Oxygen isotope analyses of garnet, pyroxene, and other minerals from skarn, oxide, and quartz-sulfide stages were carried out using SIMS to determine the origin and evolution of the skarn-forming hydrothermal system. Garnet from exoskarn has a much wider range in δ18OVSMOW, between –8.1 and +6.0‰, than other stages and minerals. The estimated δ18O values of fluids in equilibrium with the Haobugao skarn vary widely from –5.1‰ to +8.9‰, suggesting that the skarn formed via episodic flux of magmatic fluid and meteoric water. Low δ18O values of cassiterite and quartz from quartz-sulfide stage rocks are +1.2 to +3.6‰, and +5.7 to +5.9‰, respectively, indicating significant contributions of meteoric water during deposition of Pb-Zn sulphides. Therefore, meteoric fluids were periodically present throughout most of the stages of skarn formation at Haobugao.

Metallogenic Material Source and Genesis of the Jilinbaolige Pb-Zn-Ag Deposit, the Great Xing’an Range, China: Constraints from Mineralogical, S Isotopic, and Pb Isotopic Studies of Sulfide Ores

The Jilinbaolige Pb-Zn-Ag polymetallic deposit is located in the eastern part of Inner Mongolia and in the central-southern part of the Great Xing’an Range, in which several large-sized Pb-Zn-Ag deposits have been found. The Jilinbaolige deposit, which occurs mainly at the contact zone between Yanshanian granite intrusion and sedimentary strata, shows strong NE-to-NNE structural control. The deposit includes three ore-forming stages: (1) the arsenopyrite–pyrite–chalcopyrite–sphalerite stage, (2) the galena–sphalerite–quartz stage, and (3) the pyrite–calcite–quartz stage. In this study, we present a systematic study on the mineralogical and geochemical characteristics (including major elements, S isotopes, and Pb isotopes) of the main sulfide ore minerals in the Jilinbaolige Pb-Zn-Ag deposit in order to evaluate the metallogenic environment, ore-forming material source, and genesis of this polymetallic deposit. The sulfide typomorphic characteristics, ore fabric, and thermometry suggest that the genesis of sulfides in the deposit is closely related to magmatic-hydrothermal activity. The early stage of mineralization might have evolved from a high-temperature hydrothermal environment. The sulfur isotopic results show that the δ34S values in the Jilinbaolige deposit range from 2.3‰ to 6.1‰, with an average value of 3.98‰, indicating that the sulfur originated from magmas with both mantle and crustal components. The Pb isotopic compositions (206Pb/204Pb = 18.214–18.330, 207Pb/204Pb = 15.478–15.615, 208Pb/204Pb = 37.957–38.292, μ = 9.24–9.50, ω = 34.49–36.49) of the sulfide ores suggest that that the lead is of crust-mantle mixed origin. The comparison between the S and Pb isotopic compositions of the Jilinbaolige deposit and the polymetallic deposits from the central-southern parts of the Great Xing’an Range suggests that these deposits have a similar metallogenic source, which is closely related to the Yanshanian granite and medium-temperature hydrothermal fluids. These ore-bearing hydrothermal fluids that evolved from deep magmatic sources migrated along the contact and fracture zones and during the subsequent gradual decrease in temperature, and the metallogenic components were deposited in the relatively open fracture and fissure space. Our results provide insights for further mineral prospecting in the south-central part of the Great Xing’an Range.

Wildfire affects boreal forest resilience through post-fire recruitment in Northeastern China

Climate change has increased the severity, frequency, and impact of fire disturbance on boreal forests worldwide. Unusual fire events can trigger a shift from needle-leaf dominated forests to broad-leaf dominated forests, altering the original succession trajectory. Thus, it is necessary to identify how altered fire regimes affect boreal forest resilience or capacity to recover after fire disturbance. In this study, we used the post-fire tree recruitment density, the aboveground biomass, the understory shrub cover, and the herb cover as indicators of forest resilience. We explored the links between patterns of resilience and burn severity across topographic positions in two post-fire forests with different time since fire. We quantified how burn severity, time since fire, and topographic position affect resilience indicators related to post-fire overstory and understory recruitment in the Great Xing’an Mountains of Northeastern China. We found that burn severity and topographic position exhibited strong influences on post-fire overstory tree recruitment and aboveground biomass. Severe fire promoted deciduous needle-leaf tree (larch) recruitment in lowland sites by removing a thick organic layer. In contrast, severe fire promoted broad-leaf tree (birch and aspen) recruitment in south-facing upland sites with relatively warmer and drier microclimates. Therefore, severe fire disturbance may trigger a post-fire species shift from larch dominated forest to broad-leaf forest, especially in south-facing upland sties. We also found that the understory may be more resilient to high severity fire than the overstory, because severity had short-term effects on post-fire understory recruitment. Our study suggested that burn severity was a crucial factor that affects boreal forest resilience through substantially altering resilience indicators related to post-fire overstory tree recruitment.

Joint Analysis of Lightning-Induced Forest Fire and Surface Influence Factors in the Great Xing’an Range

For several decades, warming-induced fires have been widespread in many forest systems. A forest fire could be a potential indicator, since the Great Xing’an Range is susceptible to global climate changes and frequent extreme events. This region has a relatively integrated forest community structure. This paper investigated 35 factors to explore how natural conditions affect fire scale. We analyzed the fire spatiotemporal distribution, by combining the Google Earth Engine (GEE) platform and historical records, and then reconstructed the fire-prone climate conditions. We used an exploratory model to minimize the climate factors and a geographically and temporally weighted regression (GTWR) model to predict regional large-scale lightning fire occurrence. The main results are (1) Lightning fire occurrence increased during the past four decades, and the regional fire season starts from the spring (May to June). (2) The time of occurrence of lightning fires had a strong correlation with the occurrence density. (3) The main natural factors affecting a fire-affected area are air moisture content, topographic slope, maximum surface air temperature, wind direction, and surface atmospheric pressure. The regional climate can be characterized that the prevailing southeastern wind bringing lots of precipitation and strong surface pressure, combined with the regional periodic lightning weather and irregular high temperatures, forming fire-prone weather. The abnormal soil water content in the spring led to vegetation growth and increased fuel storage. The low air water content and long-term water deficit made the local air dry. Lightning strikes are an influential factor in fire frequency, while climatic conditions shape the fire-affected areas. (4) The seven days of pre-fire data are more accurate for studying lightning fire occurrence. The GTWR model showed the best fitness among the four models. Fire-prone areas showed a trend of increasing from south to north. In the future, lightning fires will likely occur in this region’s north and east. Our work would promote the local forest fire policy-making process.

Age, fluid inclusion, and H–O–S–Pb isotope geochemistry of the Baiyinchagan Sn–Ag–polymetallic deposit in the southern Great Xing'an Range, NE China

The superlarge Baiyinchagan Sn–Ag–polymetallic deposit of Inner Mongolia is located in the west slope of the southern Great Xing'an Range, NE China. The vein orebodies of the deposit occur in the NEE-trending fault zones. The mineralization process at the deposit can be divided into four stages: quartz–fluorite–cassiterite–sphalerite stage (stage I), quartz–fluorite–cassiterite–sulfide stage (stage II), quartz–calcite–sulfide stage (stage III), and quartz–stibnite stage (stage IV). Cassiterite U–Pb dating indicates that the Baiyinchagan deposit formed approximately 140 Ma ago, and zircon U–Pb dating for granite porphyry in the Baiyinchagan deposit yielded an age of 140.8 Ma. Two types of fluid inclusions (FIs), including liquid-rich and gas-rich inclusions, have been distinguished in quartz and fluorite veins. The homogenization temperature of the FIs in the stage I ranges from 318 °C to 351 °C with salinities of 1.2–3.8 wt% NaCl eqv. The homogenization temperature of the FIs in the stage II is 262–276 °C with salinities of 1.8–3.4 wt% NaCl eqv. The homogenization temperature of the FIs in the stage III ranges from 174 °C to 233 °C with salinities of 1.8–3.0 wt% NaCl eqv. The homogenization temperature of the FIs in the stage IV is in the range of 136–168 °C, and the salinity is 0.8 wt% to 2.4 wt% NaCl eqv. The ore-forming fluid of the Baiyinchagan deposit is characterized by medium–high temperature and low salinity. The δ18Owater and δD values of ore-forming fluid range from −13.5 ‰ to 9.5 ‰ and −119 ‰ to −84 ‰, respectively, indicating that the ore-forming fluid was dominantly derived from magmatic fluid mixed with meteoric water. The calculated δ34SH2S values range from −12.3 ‰ to −6.2 ‰, implying that the sulfur mainly came from granitic magma, but magmatic degassing occurred during mineralization. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values of the sulfides are in the ranges of 18.180–18.339, 15.525–15.643, and 38.005–38.477, respectively. The Pb isotopic compositions of sulfides indicate that the Pb mainly derived from granitic magma that may be formed by partial melting of orogenic materials. Fluid immiscibility and mixing were the two primary mechanisms for mineral precipitation.

Ages, H[sbnd]O[sbnd]C[sbnd]S[sbnd]Pb isotopes, and fluid inclusion study of the Daolundaba Cu–Sn–W–Ag deposit in Inner Mongolia, NE China

The medium-sized Daolundaba Cu–Sn–W–Ag deposit is located in the southern Great Xing'an Range (SGXR), being one of the representative deposits in this area. The vein orebodies of the deposit occur within the NE-trending fracture zones, which are developed in the Early Permian silty slate and Late Variscan biotite monzogranite. However, its mineralization age remains controversial, which affects the understanding of Sn–polymetallic mineralization in the SGXR. To determine the mineralization age and reveal the sources of fluid and ore-forming material, sericite and monazite dating, fluid inclusion microthermometry, and isotopic analysis were carried out in this study. The ore-forming process at the deposit can be divided into four stages: quartz–fluorite–muscovite–tourmaline–cassiterite–wolframite–arsenopyrite stage (stage I), quartz–fluorite–wolframite–chalcopyrite–arsenopyrite–pyrrhotite stage (stage II), quartz–fluorite–sericite–chalcopyrite–pyrite–pyrrhotite–silver mineral stage (stage III), and quartz–calcite–fluorite–pyrite stage (stage IV). The sericite sample yielded a 40Ar–39Ar plateau age of 138.8 ± 0.7 Ma and an isochronal age of 140.0 ± 1.1 Ma, and the LA-ICP-MS U–Pb age of three monazite samples was 136.0 ± 2.3–134.7 ± 2.8 Ma, indicating that the Daolundaba deposit formed in the Early Cretaceous. Liquid-rich, gas-rich, and daughter mineral-bearing inclusions have been identified in quartz, fluorite, and calcite. Homogenization temperatures and salinities of the fluid inclusions (FIs) in the stage I vary from 309 °C to 389 °C and 6.2 wt% to 46.3 wt% NaCl eqv., respectively. Homogenization temperatures and salinities of the FIs in the stage II vary from 242 °C to 339 °C and 5.3 wt% to 41.4 wt% NaCl eqv., respectively. Homogenization temperatures and salinities of the FIs in the stage III vary from 153 °C to 268 °C and 3.5 wt% to 35.4 wt% NaCl eqv., respectively. There are only liquid-rich inclusions in quartz, fluorite, and calcite of the stage IV; their homogenization temperatures and salinities vary from 114 °C to 188 °C and 2.1 wt% to 7.6 wt% NaCl eqv., respectively. The ore-forming fluids of the Daolundaba deposit are characterized by moderate–high temperature and great fluctuating salinity, belonging to an H2O–NaCl ± CO2 ± CH4 system. The δ18Owater and δD values of the stages I and II vary from 2.5 ‰ to 7.2 ‰ and − 127 ‰ to − 106 ‰, respectively; the δ18Owater and δD values of the stage III vary from − 3.0 ‰ to − 0.3 ‰ and − 126 ‰ to − 94 ‰, respectively; the δ18Owater and δD values of the stage IV vary from − 10.9 ‰ to − 4.7 ‰ and − 102 ‰ to − 81 ‰, respectively; indicating that the ore-forming fluids of the stages I and II mainly consist of magmatic water, that the ore-forming fluid in the stage III is a mixture of magmatic and meteoric water, and that the fluid in the stage IV is meteoric water. The δ13C values for calcite of the stage IV vary from − 9.8 ‰ to − 6.7 ‰, suggesting that the carbon was mainly from a magmatic source. The δ34S values range from − 7.4 ‰ to − 1.3 ‰ with an average of − 4.7 ‰. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of the metallic minerals are in the ranges of 18.293–18.612, 15.519–15.706, and 38.078–38.826, respectively. Both S and Pb isotopic systems indicate that the ore-forming metals primarily came from Mesozoic felsic magma. Fluid boiling and mixing were two main mechanisms for the deposition of ore-forming materials.