Current status and research prospects of terrestrial ecosystem carbon sink in Northeast China.

Increasing the carbon sink capacity of terrestrial ecosystems is a primary strategy to mitigate climate change and achieve the "carbon neutrality" goal. Clarifying the status and future dynamics of carbon sink of terrestrial ecosystems in Northeast China is crucial for achieving "carbon neutrality" as this region is a core contributor to carbon sink in China's terrestrial ecosystems. Here, we systematically summarized current research on carbon sink of terrestrial ecosystems across Northeast China, including the measurements and spatial-temporal patterns of carbon sinks, driving mechanisms of carbon sinks, the assessments of carbon sink potential, and technologies for increasing carbon sequestration. There are substantial uncertainties in quantifying terrestrial ecosystem carbon sink in Northeast China due to differences in data sources and methods, especially for forest carbon sink measurements, ranging from 0.020 to 0.157 Pg C·a-1. Carbon sink function depends on carbon exchange processes across plant-soil-atmosphere interfaces. The key pathways to enhance carbon sequestration in Northeast China under different temporal and spatial scales remains unclear. Improving terrestrial ecosystem quality is the key and core of carbon sequestration and sink enhancement. However, there is an urgent need to develop a multi-ecosystem collaborative carbon sequestration and sink enhancement technology system for the "dual carbon" goal. Future research needs to develop an accurate carbon sink measurement system that integrates multi-source data and multi-scale technologies to accurately assess the function and potential of carbon sink in Northeast China, focus on the multi-scale driving mechanism of carbon sink functions, develop new technical systems for coordinated enhancement of carbon sink for the Northeast terrestrial ecosystems, and carry out demonstrations of carbon sink enhancement technologies. These efforts will provide the scientific and technological supports for achieving the "carbon neutrality" goal.

Research advance in effects of solar radiation on litter decomposition in terrestrial ecosystems.

Litter decomposition significantly influences the carbon (C) dynamics of terrestrial ecosystems. Solar radiation is not only essential for photosynthetic C fixation and primary productivity, but also can directly or indirectly promote litter decomposition through photodegradation. Recently, photodegradation has been identified as a key factor driving litter decomposition and potentially impacts terrestrial C cycle. To enrich and develop the theory of litter decomposition, we summarized the mechanisms and main driving factors of photodegradation, and compared the responses of photodegradation to environment and climate changes at different scales. Photodegradation primarily includes photomineralization, photoinhibition, and photofaciliation, each affecting litter decomposition differently under various environmental conditions. Photodegradation is closely related to factors such as solar radiation, litter traits, temperature, moisture, microorganisms, and vegetation cover. The interactions among these factors complicate the patterns of photodegradation. Finally, we identified the main issues in litter photodegradation research and prospected future research directions. We emphasized the needs for in-depth exploration of photodegradation pathways and intrinsic mechanisms, quantification of its interactive effects with environmental factors, and optimization of traditional carbon turnover models.

Spatial structure and individual competition characteristics of secondary Mongolian oak mature forests in the mountainous area of eastern Liaoning Province, China.

The community structure of natural mature forests is determined by long-term forest succession, characterized by rational structure, rich biodiversity, and high ecological function. Understanding the spatial structure and formation mechanisms of mature forests is a fundamental prerequisite for forest management. We analyzed four structure parameters, including diameter structure, angular scale, size ratio, and mixture degree, as well as the Hegyi competition index, of secondary Quercus mongolica (Mongolian oak) mature forests in the mountainous area of eastern Liaoning Province. The results showed that Q. mongolica predominated the tree layer. In the sapling layer, Q. mongolica, Tilia amurensis, and Acer pictum were the dominant species. In the seedling layer, Acer pseudosieboldianum, T. amurensis, and A. amurensis dominated, with very few Q. mongolica seedlings. The overall diameter distribution of the stand showed an inverse "J" shape, while the diameter distribution of Q. mongolica, the dominant tree species, followed a normal distribution. The horizontal spatial structure of the stand was generally randomly distributed, with an average angle scale of 0.505, size ratio of 0.219, and mixture degree of 0.670 for Q. mongolica. From the perspective of spatial structure binary distribution, Q. mongolica individuals which had a random distribution exhibited greater growth advantages and higher levels of mixing, in comparison to other distribution types. Randomly distributed dominant and subdominant individuals made up nearly half individuals in the stand, and showed a high degree of mixing with surrounding trees. The stand-level individual tree competition index decreased with increasing diameter classes. When the diameter at breast height exceeded 20 cm, the competition index tended to stabilize (ΔCI<2). The competitive radius of individual Q. mongolica trees was 8 m, with intraspecific competition as the main pressure. Other species experienced competition pressure primarily from interspecific sources. Our results suggested that competition played an important role in shaping the spatial structure of secondary Q. mongolica mature forests.

Latitudinal responses of litter decomposition to solar radiation.

Photodegradation driven by solar radiation has been confirmed as an important driving factor for litter decomposition. However, previous single-site studies could not quantify the relative contribution of variation in solar radiation to litter decomposition. To address it, we conducted a field experiment in Heshan National Field Research Station of Forest Ecosystem, Guangdong (Heshan Station, south subtropical climate), Jigongshan Ecological Research Station, Xinyang, Henan (Jigongshan Station, north subtropical climate) and Daqinggou Ecological Research Station, Institute of Applied Ecology, Chinese Academy of Sciences (Daqinggou Station, temperate climate) at intervals of 10 degrees. We examined litter decomposition of Populus davidiana and Larix olgensis, two species with significant differences in initial litter quality through an in-situ spectral-attenuation experiment. Treatments included full-spectrum, No-UV-B (attenuating UV-B radiation <315 nm) and No-UV & Blue (attenuating all UV and blue wavelengths <500 nm). After nearly 1-year decomposition, litter dry mass remaining of P. davidiana and L. olgensis under full-spectrum treatment was lowest at Heshan (30.2% and 36.3%), and highest at Jigongshan (37.3% and 45.8%). Among all sites, litter dry mass remaining was lowest under the full-spectrum, and lower than that of No-UV-B and No-UV & blue. UV and blue light significantly increased litter mass loss of P. davidiana and L. olgensis, with contributions of 59.7% and 57.0% (Heshan), 46.4% and 42.1% (Jigongshan), and 39.0% and 45.9% (Daqinggou), respectively. The contribution of UV-A and blue light (315-500 nm) was greater than UV-B (280-315 nm); the cumulative irradiance, soil temperature and moisture were the main driving factors for litter photodegradation.

Effects of light qualities on growth and physiological-biochemical traits of Scutellaria baicalensis.

Canopy spectral composition significantly affects growth and functional traits of understory plants. In this study, we explored the optimal light condition suitable for enhancing Scutellaria baicalensis's yield and quality, aiming to provide scientific reference for the exploitation and utilization of medicinal plant resources in the understory of forests. We measured the responses of growth, morphology, biomass allocation, physiological traits, and secon-dary metabolites of S. baicalensis to different light qualities. S. baicalensis was cultured under five LED-light treatments including full spectrum light (control), ultraviolet-A (UV-A) radiation, blue, green, and red light. Results showed that UV-A significantly reduced plant height, base diameter, leaf thickness, leaf area ratio, and biomass of each organ. Red light significantly reduced base diameter, biomass, effective quantum yield of photosystem Ⅱ (ФPSⅡ), and total flavonoid concentration. Under blue light, root length and total biomass of S. baicalensis significantly increased by 48.0% and 10.8%, respectively, while leaf number and chlorophyll content significantly decreased by 20.0% and 31.6%, respectively. The other physiological and biochemical traits were consistent with their responses in control. Our results suggested that blue light promoted photosynthesis, biomass accumulation, and secondary metabolite synthesis of S. baicalensis, while red light and UV-A radiation negatively affected physiological and biochemical metabolic processes. Therefore, the ratio of blue light could be appropriately increased to improve the yield and quality of S. baicalensis.

[Effects of canopy spectral composition on growth and photosynthetic fluorescence characteristics of Pinus koraiensis and Quercus mongolica seedlings]. / å† å±‚å ‰è°±ç»„æˆå¯¹çº¢æ¾å’Œè’™å¤æ Žå¹¼è‹—ç”Ÿé•¿å’Œå ‰åˆè§å ‰ç‰¹æ€§çš„å½±å“.

We investigated the responses of leaf and individual traits, growth, and fluorescence characteristics of seedlings of two dominant species of broad-leaved Korean pine forest in Changbai Mountain, i.e., Pinus koraiensis and Quercus mongolica, to five spectrum-attenuation treatments. Results showed that the architecture and growth of P. koraiensis and Q. mongolica seedlings were mainly regulated by ultraviolet B (UV-B) radiation and blue light. The attenuation of blue light significantly decreased leaf area ratio and relative growth rate of two species. The attenuation of UV-B radiation significantly increased leaf area ratio and relative growth rate of P. koraiensis seedlings by 41.8% and 47.7%, respectively, and significantly decreased plant height, total leaf area, and biomass accumulation of Q. mongolica seedlings. Furthermore, the attenuation of UV-B radiation significantly decreased the fluorescence regulation ability of two tree seedlings, with lower magnitude of P. koraiensis than Q. mongolica. The non-regulatory quantum yield (ΦNO) of P. koraiensis increased by 31.6%, and the ΦNPQ/ΦNO ratio, an indicator for photosynthetic fluorescence regulation ability, decreased by 37.5%. These results suggested that those two species might have evolved adaptation strategies to changes in canopy spectral compositions of their respective habitats. Q. mongolica seedlings tended to improve light capture ability through rapid morphological responses, while P. koraiensis seedlings preferred to increase carbon assimilation efficiency by adjusting fluorescence characteristics.

Accounting of gross ecosystem product in Fuzhou City,China.

Carrying out the accounting of ecological system gross ecosystem product (GEP) is a necessary measure to promote the construction of ecological civilization system and an important measure for the integration of ecological benefits into the economic and social development evaluation system. Taking Fuzhou City as the object, we constructed an ecosystem value accounting system with the characteristics of "mountain, sea, and city" to calculate the GEP of Fuzhou City in 2015 and 2018, and compared them from the perspective of temporal and spatial changes. The results showed that the GEP of Fuzhou in 2015 and 2018 was 920.592 and 1047.242 billion yuan, respectively. The per capita GEP in 2015 and 2018 was 130200 and 143900 yuan, the supply service value of ecological products was 94.181 and 110.261 billion yuan, the value of ecological regulation was 636.42 and 598.851 billion yuan, and the service value of ecological culture was 189.991 and 338.13 billion yuan, respectively. Compared with that in 2015, the GEP of Fuzhou City in 2018 increased by 126.65 billion yuan, with an increase of 13.8%, which was mainly due to the increases in ecological product supply service and cultural service. The value of ecological regulation services decreased by 37.569 billion yuan, with a reduction of 5.9%, which was mainly due to the decreases in climate regulation, water flow regulation and water purification services. Fuzhou City took the lead in exploring the establishment of accounting system with the characteristics of "mountain, sea, and city", which could provide a "Fuzhou model" for the accounting work of other cities in Fujian Province and other regions in China, and promote the establishment of a long-term mechanism for realizing the value of ecological products.

[Spatial and temporal variations of the responses of radial growth of Larix gmelinii to climate in the Daxing'anling Mountains of Northeast China]. / å¤§å ´å®‰å²­å ´å®‰è½å¶æ¾å¾„å‘ç”Ÿé•¿å¯¹æ°”å€™å“åº”çš„æ—¶ç©ºå˜åŒ–.

Following the distribution characteristics of Larix gmelinii in Daxing'anling Mountains, nine sampling sites along a latitude gradient were set up to analyze the spatial difference and temporal dynamic in the responses of radial growth of L. gmelinii to climate. Overall, the radial growth of L. gmelinii was positively correlated with the standardized precipitation evapotranspiration index (SPEI) in summer (June to August), summer precipitation, February SPEI, and February preci-pitation, but was negatively correlated with the March temperature. Spatially, in the southern area of the region with higher annual average temperature, the radial growth of L. gmelinii had a significant positive correlation with February SPEI. In the northern area with lower annual average tempera-ture, the radial growth of L. gmelinii was negatively correlated with the temperature in March. Temporally, the growth-climate relationship for L. gmelinii was unstable. In the area with higher annual average temperature, the positive effects of SPEI and precipitation, as well as the negative effects of temperature in summer on growth significantly enhanced with climate warming. In the area with lower annual average temperature, the negative response of growth to March temperature enhanced more obviously. Such a result indicated that climate change would alter growth-climate relationship, with great spatial variations. Our results suggested that radial growth of L. gmelinii would be limited in the future climate of warm and dry in the Daxing'anling Mountains. The growth of L. gmelinii might obviously decline in south due to summer water deficit and winter drought, and might be inhibited in north because of warm and dry winter.

Response of photosynthetic characteristics and non-structural carbohydrate accumulation of Betula ermanii seedlings to drought stress.

We explored the effects of drought stress on photosynthetic characteristics and non-structural carbohydrate (NSC) accumulation of the timberline tree species Betula ermanii in Changbai Mountain with a drought control experiment. The results showed that drought significantly reduced the net photosynthetic rate and stomatal conductance, but increased water use efficiency (WUE) of B. ermanii seedlings. Drought dramatically improved the contents of soluble sugar and total NSC in leaves, barks, stems, and roots of B. ermanii seedlings, but significantly reduced their starch content. The stomatal conductance, photosynthetic rate and WUE decreased rapidly as the drought continued, whereas the contents of soluble sugar, starch and NSC increased and then declined. At the end of the experiment, 90% of the leaves turned yellow, and the ratios of soluble sugar to starch in the stems, barks and roots under the drought treatment were significantly higher than those in the control. These results demonstrated that B. ermanii might be a drought-avoidance species that could reduce water loss by rapidly reducing stomatal conductance and improving WUE under drought stress. B. ermanii might have evolved priority storage strategy to cope with water deficit through improving the content of soluble sugar in organs and increasing the transformation rate between starch and sugar. With the extension of drought stress, seedlings tended to die, since water stress might exceed the threshold of the plant self-regulation capacity. However, the content of NSC in organs did not decrease, suggesting that the death of B. ermanii under drought stress might not be caused by carbon starvation.

[Changes of productivity with stand development in broadleaf-Korean pine forest in Changbai Mountain, China]. / 长白山阔叶红松林生产力随林分发育的变化.

Stand age is a key factor affecting carbon stocks and fluxes of forest ecosystem. Quantification of the changes in forest productivity with stand development is critically important for optimizing forest age structure, facilitating maximum utilization of resources, and better realizing the role of forests in regulating the uptake, storage, and emission of CO2. In this study, using space for time substitution approach, we established 12 chronosequence plots in the broadleaf-Korean pine forests of Lushuihe. Using a locally parameterized Biome-BGC model, we simulated the dynamics of net primary productivity (NPP) with stand development and examined the changes with stand development in NPP of broadleaf-Korean pine forests under four developmental scenarios. Results showed that the biomass in broadleaf-Korean pine forests of different age-classes ranked in the order of young stand < mid-age stand < mature stand < over-mature stand, with the average value of (224.35±20.68), (237.23±39.96), (259.16±19.51), and (357.57±84.74) t·hm-2, respectively. Modelled NPP in broadleaf-Korean pine forests of different developmental stages varied in the range of 489.8-588 g C·m-2·a-1, which were consistent with the observed data of MODIS NPP, highlighting the adequacy and accuracy of Biome-BGC model in simulating the carbon flux of broadleaf-Korean pine forests. Simulated NPP displayed a pattern of initial increase and later decrease with stand development, reaching peak in the mid-age stand and being smallest in the over-mature stand. Simulations of NPP in broadleaf-Korean pine forest under four developmental scenarios showed that, for the two scenarios with planted Korean pine forests experiencing either natural development or controlled cutting, NPP was highest in the mature stage; whereas for the two scenarios with initial natural secondary birch forests experiencing either natural development or controlled cutting, NPP was highest in the young stage.

[Recognition of priority area of biodiversity conservation in Liaoning Province, Northeast China]. / è¾½å®çœç”Ÿç‰©å¤šæ ·æ€§ä¿æŠ¤ä¼˜å ˆåŒºè¯†åˆ«.

Priority areas of biodiversity conservation (PABC) were classified to strengthen biodiversity conservation in China. As there are no such priority areas in Liaoning Province, China, it is important to make up this gap. After calculation of seven indices at three composition levels (ecosystem conservation, human interference, and regionalization for biodiversity conservation), index values, composition values, and comprehensive recognition value for PABCs in Liaoning Province were obtained successively. Suggested territorial scopes of Western Liaoning Priority Area (WPA) and Eastern Liaoning Priority Area (EPA) were then determined in terms of administrative boundaries of towns, counties, and nature reserves. Among them, WPA covers an area of 12951 km2, with 53.6% of forest coverage and nine national or provincial nature reserves. The main ecological function of WPA is soil and water conservation. EPA is 20057 km2 in area, with 78.9% of forest cove-rage and eight national or provincial nature reserves. Water resource conservation is the main ecological function of EPA. Key protected species at national or provincial level and the important ecosystems are densely distributed in those priority areas. It is urgent to carry out biodiversity conservation in these PABCs.

[Exploring the history of the management theory and technology of broad-leaved Korean pine (Pinus koraiensis Sieb. et Zucc.)forest in Changbai Mountain Region, Northeast China.] / é•¿ç™½å±±åŒºé˜”å¶çº¢æ¾æž—ç»è¥åŽ†å²ä¸Žç ”ç©¶åŽ†ç¨‹.

Changbai Mountain is located in the eastern mountain forest region of Northeast China, with broad-leaved Korean pine forest (BKF) as the climax vegetation type. The region is rich in species diversity and serves as an important carrier for precious wood production and forest belts in Northeast China. In the recent 120 years, the vast primary forests in Changbai Mountains have almost disappeared, and have been replaced by secondary forests, over-cut forests, and plantations. Since the founding of the People's Republic of China, the theory and technology of forest management for BKF in Northeast China have gradually improved along with the researches and understanding on the structure and function of BKF, the disputes of Korean pine regeneration characteristics, and the debate about clear cutting and selective cutting. However, the problem of insufficient Korean pine regeneration still exists, and forest management is very extensive. We tried to untangle the management technology trail and research history of BKF in the past 70 years, and to analyze the current forest types and the formation process of the management regulations, with the aim to provide reference for the sustainable management and quality improvement of natural forests in the region.

[Effects of nitrogen addition on biomass allocation of Pinus koraiensis and Fraxinus mandshurica seedlings under water stress.] / æ°®æ·»åŠ å’Œæ°´åˆ†èƒè¿«å¯¹çº¢æ¾ã€æ°´æ›²æŸ³å¹¼è‹—ç”Ÿç‰©é‡åˆ†é çš„å½±å“.

Nitrogen deposition and climate warming-drying are the main environmental changes in Northeast China. How they affect forest ecosystems has always been studied in ecological research. In this study, we explored the effects of water stress and nitrogen (N) addition on the short-term (in 55 weeks) growth of seedlings of Pinus koraiensis and Fraxinus mandshurica, two key species in broad-leaved and P. koraiensis mixed forests in temperate zone of Northeast China. Results showed that the responses of seedling growth of P. koraiensis and F. mandshurica to nitrogen addition and water stress were significantly different. P. koraiensis was more sensitive to water stress. In the early stage (in 10 weeks) of water stress, leaf biomass of P. koraiensis significantly decreased while the root biomass increased. Nitrogen addition significantly reduced the root and total biomass of P. koraiensis under water stress. F. mandshurica was more sensitive to N addition. Nitrogen addition rapidly increased the stem, root and total biomass of F. mandshurica. Only sustained water stress could significantly affect the stem, root and total biomass of F. mandshurica. Under continuous water stress and N addition, the biomass contribution of leaves and roots to whole seedling, and the ratio of aboveground to underground biomass of both species tended to be constant, indicating strong self-regulation ability of both species. The results suggested that when drought occurred in the future, P. koraiensis would adopt a "positive" adjustment strategy, while F. mandshurica would adopt a "passive" response. The survival rate and adaptability of P. koraiensis would be higher than F. mandshurica. F. mandshurica would benefit more from N deposition than P. koraiensis. Our results are helpful for predicting the changes of community structure in temperate forest in Northeast China.

[Competition of key tree species with selective cutting at different intensities in broadleaved-korean pine mixed forest in the Changbai Mountain, China.] / é•¿ç™½å±±é˜”å¶çº¢æ¾æž—ä¸åŒå¼ºåº¦æ‹©ä¼åŽå ³é”®æ ‘ç§çš„ç«žäº‰å ³ç³».

Selective cutting changes tree species composition and stand structure, modifies tree competition intensity in the stand, with consequences on tree growth and population dynamics. Key tree species play a crucial role in maintaining community structure and ecosystem function. To clarify the competitive characteristics of three key species (Pinus koraiensis, Tilia amurensis, and Fraxinus mandshurica, which accounted for about 70% of growing stock) of typical forest types in broadleaved-Korean pine mixed forest, Hegyi competition index was used in four permanent 1-hm2 plots, i.e. virgin forest (VF), low-intensity cutting forest (LCF), moderate-intensity cutting forest (MCF) and high-intensity cutting forest (HCF). Compared with VF, the stand density and mean DBH of big trees (DBH≥20 cm) significantly decreased in MCF and HCF, but the stand density of young trees (2 cm≤DBH<10 cm) increased, but no significant changes of stand or DBH in LCF. In all the four forest types, individual competition index (CI) of the three species decreased with increasing DBH. There was a power function relation between CI and DBH. CI curve turned to be gentle at DBH reaching 20 cm, and this rule was not affected by selective cutting. In VF, LCF and HCF, most of competition pressure of young trees of all key species derived from other tree species in secondary canopy or understory, but the competition pressure of small trees (10 cm≤DBH<20 cm) and big trees of P. koraiensis originated mainly from intra-species and other species in secondary canopy or understory. The competition stress of F. mandshurica was mainly affected by P. koraiensis and other species in secondary canopy or understory. T. amurensis was mainly affected by intra-species and P. koraiensis. Betula platyphylla contributed most of the competition stress (over 50%) to all three key species in HCF. Our results suggested that removing the trees which are in secondary canopy or understory but suppress the three key trees species intensively would be beneficial to the regeneration and growth of key species before tree DBH exceeds 20 cm. We proposed to regulate the density of key tree species in overstory to cultivate large diameter timber according to the competition among the key trees species. Once tree DBH exceeds 20 cm, tree growth would not be affected by competition. This study had guiding significance for the cultivation of key tree species and rapid recovery of natural forests after selective cutting.

[Effect of neighborhood competition on key tree species growth in broadleaved-Korean pine mixed forest in Changbai Mountain, China.] / é‚»åŸŸç«žäº‰å¯¹é•¿ç™½å±±é˜”å¶çº¢æ¾æž—å ³é”®æ ‘ç§ç”Ÿé•¿çš„å½±å“.

Competition is the main factor affecting the growth, morphology and death of trees in fore-sts. The analysis of individual competition can reflect the characteristics of interaction among individuals and their interaction ranges, which is important for reducing individual competition and promoting tree growth. To understand the effects of competition on tree growth in broad-leaved Korean pine forest, based on Hegyi single-tree competition index and neighborhood analysis method, we explored the neighborhood radius of competition for five key tree species, i.e. Pinus koraiensis, Tilia amurensis, Fraxinus mandshurica, Quercus mongolica and Ulmus japonica (80% of basal area at breast height in total), and analyzed the effects of competition on the growth and death of the key tree species. The results showed that the neighborhood radius of single-tree competition of four tree species, P. koraiensis, T. amurensis, F. mandshurica and Q. mongolica was 11 m, while that of U. pumila was 13 m. The single-tree competition intensity for all five key tree species was negatively correlated with the logarithm of its growth increment, and positively correlated with the size of individual trees. The relative importance of competition intensity on tree growth decreased with tree growth. Neighborhood competition significantly increased tree mortality. Our results revealed the effects of neighborhood competition on the growth and survival of the key tree species at different developmental stages in broad-leaved Korean pine forests in Changbai Mountain. The results are instructive to the adjustment of competitive environment and the improvement of productivity of key tree species in broad-leaved Korean pine forests.

[Tree radial growth-climate relationship in Changbai Mountain, Northeast China.] / é•¿ç™½å±±æ ‘æœ¨å¾„å‘ç”Ÿé•¿å¯¹æ°”å€™å› å­çš„å“åº”.

Changbai Mountain is one of the hotspots for tree ring research in Northeast China, with a large number of related research results having been published. To clarify the advance of tree ring research in Changbai Mountain and understand the responses of tree radial growth to climate factors, we reviewed the related literature and analyzed the differences among them based on tree species identity, elevation, and detrended methods. The radial growth of trees in Changbai Mountain was generally affected by temperature and precipitation, with greater influence of temperature. The relationship between tree radial growth and climate variables varied across both species and altitudes. Most studies reported that the radial growth of conifers were mainly affected by temperature in early growing season (April-May) and growing season precipitation (June-August). The radial growth of broadleaved trees were mainly affected by the temperature in previous and current growing season, the precipitation in dormancy season (November-March), and the precipitation in the current growing season. The previous September precipitation had significant effects on the radial growth of conifers and broadleaved trees. However, many studies had reported different or even opposite results. Most of the differences in the results of the studies appeared at low and medium altitudes, indicating that the altitudinal location of sampling points had impacts on the results. In addition, the detrended method was also the main cause for the variation of results across different studies. Comparatively, the linear or negative exponential detrended method might increase the effective significance of precipitation, especially the effect of precipitation on tree growth during dormancy period, and also strengthen the effective significance of the temperature at the end of the growing season. This study showed the habitat and the detrended method used in chronology were the main reasons for the difference of results among the studies. Therefore, for tree ring research in Changbai Mountain, the number of sampling sites should be increased and the detrended method should be carefully selected.

[Interspecific difference of relationship between radial growth and climate factor for Larix olgensis and Picea jezoensis var. komarovii in Changbai Mountain, Northeast China.] / 长白山落叶松与鱼鳞云杉生长-æ°”å€™å ³ç³»çš„ç§é—´å·®å¼‚.

To clarify the responses of radial growth of different tree species to climate change and its stability, we explored the relationships between radial growth and climate factors of larch (Larix olgensis) and spruce (Picea jezoensis var. komarovii) distributed at high altitude (1600-1750 m) on the northern slope of Changbai Mountain, using the chronological method. The results showed that the growth of larch was significantly positively correlated with the maximum temperature in June and negatively correlated with the precipitation in June. The radial growth of spruce was significantly positively correlated with the maximum temperature in May. Results from redundancy analysis showed that larch growth was mainly affected by summer temperature, while spruce growth was significantly restricted by spring temperature. During 1959-2014, the relationship between larch growth and summer temperature was relatively stable. For spruce, the correlation between radial growth and spring temperatures had gradually weakened since 1986, mainly due to the growth slowdown because of decreased maximum air temperature. Our results provide theoretical references for predicting the growth response of conifers at Changbai Mountain region in the context of climate change.

[Responses of soil carbon and nitrogen mineralization to nitrogen deposition in tundra zone of the Changbai Mountain, China.] / 长白山苔原带土壤碳、氮矿化对氮沉降的响应.

The alpine tundra ecosystem, with low soil inorganic nitrogen (N) availability, has a weak buffer against nitrogen and is susceptible to exogenous N enrichment. Here, with a laboratory incubation experiment, we investigated the response of soil carbon and nitrogen mineralization to N deposition with soil samples from the tundra zone on the northern slope of the Changbai Mountain. We set three N levels, control (CK, 0 kg·hm-2), low N (N1, 25 kg·hm-2), and high N (N2, 50 kg·hm-2), with N being added as NH4NO3. The results showed that N addition had no significant effect on soil C mineralization rate, but significantly affected the accumulation of soil C minera-lization. The N2 treatment inhibited soil C mineralization. After the 40 d incubation, soil inorganic N content increased with increasing N addition. After the 80 d incubation, soil inorganic N content in the N2 and N1 was similar and significantly higher than that of CK. Those results indicated that N addition promoted soil N mineralization. The soil microbial biomass C and N in the N1 was higher than that in the N2 and CK, indicating that low N input had stronger effects on soil microbial activity. Increasing N deposition might accelerate C and N turnover in the tundra soils and enhance the soil inorganic N content. While it could provide more N for plants, it may increase the risk of N loss.

[Characteristics of non-structural carbohydrate reserves of three dominant tree species in broadleaved Korean pine forest in Changbai Mountain, China.] / 长白山阔叶红松林3ä¸ªä¸»è¦æ ‘ç§çš„éžç»“æž„æ€§ç¢³å‚¨å­˜ç‰¹å¾.

Non-structural carbohydrates (NSC, including soluble sugars and starch) are key meta-bolites in tree, the storage characteristics of which in tree organs have received extensive attention. It is still unclear how NSC are allocated in the tissues (phloem and xylem) that have different function. In this study, we analyzed the concentration and allocation of NSC in the roots, and in phloem and xylem of the trunk in three dominant species of broadleaved Korean pine forest in the Changbai Mountain, Pinus koraiensis, Fraxinus mandschurica, and Tilia amurensis. The results showed that there was a significant difference in the concentration of NSC between the phloem and xylem. The soluble sugar dominated in the phloem, while starch dominated in the xylem. The concentration of NSC in trunk outside (divided by annual rings, 0-20 years), intermediate (20-40 years) and inner (>40 years) of different tree species was significantly different, but with no difference in the roots. The total soluble sugar concentration in the phloem of P. koraiensis and F. mandschurica was significantly higher than that of T. amurensis, while the difference in xylem was not significant. The results indicated that NSC allocation in the phloem and xylem of the tree had clear tissue differentiation, which might be related to the succession stage of the tree species or the functional evolution of the tissue. These findings would improve our understanding of the carbon storage characteristics and allocation mechanism in temperate trees.

[Ecological vulnerability assessment on Changbai Mountain National Nature Reserve and its surrounding areas, Northeast China.] / é•¿ç™½å±±å›½å®¶è‡ªç„¶ä¿æŠ¤åŒºåŠå ¶å‘¨è¾¹åœ°åŒºç”Ÿæ€è„†å¼±æ€§è¯„ä¼°.

Exploring the ecological vulnerability of nature reserve and its surrounding area is essential to the maintenance of regional ecological security and sustainability of human development, especially under the stress of global change and human activities. Based on the integration of "sensitivity-resilience-pressure" conceptual model and spatial principal component analysis (SPCA), we analyzed the ecological vulnerability of Changbai Mountain National Nature Reserve and its surrounding 30 km buffer in 2005 and 2015. The main driving factors were further analyzed. The results showed that the ecological vulnerability of Changbai Mountain Nature Reserve was mainly potential, slight, and light levels in 2005 and 2015, indicating the ecological vulnerability inside and outside the reserve was in a good condition. For the whole region, the ecological vulnerability showed a slight downward trend from 2005 to 2015. The degradation area inside and outside the reserve were 254 and 967 km2, respectively, with the contribution rate to the increase of overall vulnerability being 30.8% and 69.2%, respectively. The changes in ecological vulnerability inside the reserve were mainly related to the changes in net primary production (NPP), vegetation coverage, and the nearest distance to the road, whereas it was mainly related to the changes in NPP, vegetation coverage and gross domestic product (GDP) density outside the reserve.