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.

The Effects of Shrub Removal on Soil Microbial Communities in Primary Forest, Secondary Forest and Plantation Forest on Changbai Mountain.

Shrub removal is a common management method in forest ecosystems, but comparatively little is known regarding the effects of shrub removal on soil microbial communities among primary forest, secondary forest, and plantation forests in temperate forests, which limits our accurate assessment of sustainable management of understory vegetation removal. Given this, we used a long-term operation experiment across a contrasting mixed broadleaved-Pinus koraiensis forest, Betula platyphylla forest, and Larix gmelinii plantation forest to explore the variations of soil properties and microbial community after 5 years of shrub removal on Changbai Mountain, as well as the contribution of the soil properties and understory plant diversity to the soil microbial community. The results demonstrated that shrub removal could significantly alter soil SWC and TN, TP, and AP contents of the L. gmelinii, as well as N/P of B. platyphylla. Moreover, shrub removal also clearly improved soil bacterial Pielou_e index and Simpson index of mixed broadleaved-P. koraiensis and soil bacterial Simpson index of L. gmelinii, and decreased soil fungal Pielou_e index and Shannon index of L. gmelinii and soil bacterial Pielou_e index and soil fungal Shannon index of B. platyphylla. Identically, shrub removal notably altered the soil bacterial community composition. Soil characteristics and understory plant diversity accounted for 48.02% and 26.88%, and 45.88% and 27.57% of the variance in the bacterial and fungal community composition, respectively. This study aimed to provide an important scientific basis for the restoration and sustainable management of temperate forests in the Changbai Mountain region.

The effects of previous summer drought and fertilization on winter non-structural carbon reserves and spring leaf development of downy oak saplings.

It is still unknown whether the previous summer season drought and fertilization will affect the winter non-structural carbohydrate (NSC) reserves, spring leaf development, and mortality of trees in the next year. We, therefore, conducted an experiment with Quercus pubescens (downy oaks) saplings grown under four drought levels from field capacity (well-watered; ~25% volumetric water content) to wilting point (extreme drought; ~6%), in combination with two fertilizer treatments (0 vs. 50 kg/ha/year blended) for one growing season to answer this question. We measured the pre- and post-winter NSC, and calculated the over-winter NSC consumption in storage tissues (i.e. shoots and roots) following drought and fertilization treatment, and recorded the spring leaf phenology, leaf biomass, and mortality next year. The results showed that, irrespective of drought intensity, carbon reserves were abundant in storage tissues, especially in roots. Extreme drought did not significantly alter NSC levels in tissues, but delayed the spring leaf expansion and reduced the leaf biomass. Previous season fertilization promoted shoot NSC use in extreme drought-stressed saplings over winter (showing reduced carbon reserves in shoots after winter), but it also showed positive effects on survival next year. We conclude that: (1) drought-stressed downy oak saplings seem to be able to maintain sufficient mobile carbohydrates for survival, (2) fertilization can alleviate the negative effects of extreme drought on survival and recovery growth of tree saplings.

[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.

Seasonal Responses of Hydraulic Function and Carbon Dynamics in Spruce Seedlings to Continuous Drought.

Drought is expected to increase in the frequency and duration associated with climate change. Although hydraulic function and carbon (C) storage have been widely recognized as key components to plant survival under a single drought, the physiological responses to continuous drought remain largely unknown, particularly for high northern temperate and boreal forests which are sensitive to water stress. In this study, we quantified the survival, growth, gas exchange, water relations, and nonstructural carbohydrates (NSCs) in 3-year-old Jezo spruce (Picea jezoensis) seedlings responding to continuous drought stress. Seedlings were maintained in drought conditions for 392 days, covering two growing and one dormant winter season. Seedlings subjected to drought showed a significant decrease in net photosynthesis rate (A net ) and stomatal conductance (g s ) in both growing seasons, and biomass in the second growing season. The seedling mortality continuously increased to 35.6% at the experimental end. Notably, responses of C storage and leaf water potential to drought varied greatly depending on seasons. Living seedlings exposed to drought and control treatments had similar NSC concentrations in both growing seasons. However, seedlings with concentrations of both the soluble sugars and starch less than 1% in root died in the winter dormant season. In the second growing season, compared with the control treatment, droughted seedlings had significantly lower leaf water potential and stem wood-specific hydraulic conductivity (K w). Meanwhile, the leaf predawn water potential did not recover overnight. These suggest that C starvation might be an important reason for seedlings that died in the winter dormant season, while in the growing season drought may limit seedling survival and growth through inducing hydraulic failure. Such seasonal dependence in hydraulic dysfunction and C depletion may lead to higher mortality in spruce forests facing extended drought duration expected in the future.

Variations of Phyllosphere and Rhizosphere Microbial Communities of Pinus koraiensis Infected by Bursaphelenchus xylophilus.

Pine wood nematode, Bursaphelenchus xylophilus, as one of the greatest threats to pine trees, is spreading all over the world. Plant microorganisms play an important role in the pathogenesis of nematodes. The phyllosphere and rhizosphere bacterial and fungal communities associated with healthy Pinus koraiensis (PKa) and P. koraiensis infected by B. xylophilus at the early (PKb) and last (PKc) stages were analyzed. Our results demonstrated that pine wood nematode (PWD) could increase the phyllosphere bacterial Pielou_e, Shannon, and Simpson index; phyllosphere fungal Chao 1 index, as well as rhizosphere bacterial Pielou_e, Shannon, and Simpson index; and rhizosphere fungal Pielou_e, Shannon, and Simpson index. What's more, slight shifts of the microbial diversity were observed at the early stage of infection, and the microbial diversity increased significantly as the symptoms of infection worsened. With the infection of B. xylophilus in P. koraiensis, Bradyrhizobium (rhizosphere bacteria), Massilia (phyllosphere bacteria), and Phaeosphaeriaceae (phyllosphere fungi) were the major contributors to the differences in community compositions among different treatments. With the infection of PWD, most of the bacterial groups tended to be co-excluding rather than co-occurring. These changes would correlate with microbial ability to suppress plant pathogen, enhancing the understanding of disease development and providing guidelines to pave the way for its possible management.

A framework of freshwater services flow model into assessment on water security and quantification of transboundary flow: A case study in northeast China.

Ecosystem service flow dynamics which establish the linkage between human and nature is essential in an ecosystem service assessment. This study constructed an ecosystem service flow model of freshwater flow then utilized it to assess the water-related ecosystem services in northeast China. We included the provision, consumption, and spatial flow of freshwater services in an index to assess the water security condition and quantified the services trans-boundary flow from the northeast forest belt (NFB) in northeast China. Our results showed that large areas (50.54%, 55.10% and 52.90%, respectively) of northeast China received upstream freshwater service in three years. The water security condition of northeast China deteriorated from 2005 to 2015 with the change of water security index considering water flow (WSIflow), mainly influenced by precipitation and agriculture water consumption. Approximately 4.16 billion m3 of freshwater service were delivered from NFB to surrounding regions demonstrating the importance of NFB in terms of ecosystem service provision. In addition, 73 key watersheds (4.71% of total area) within NFB that significantly affect the trans-boundary flow were further identified. We suggested that local government should advocate develop water-saving agriculture and livestock water quotas. Moreover, priorities should be given to protect the key watersheds within NFB in order to maintain the supply of freshwater service. This study provided a framework for exploring suitable strategies for managing water resources and laid a foundation for promoting the ecological compensation in the future.

Effect of microfibers combined with UV-B and drought on plant community.

There is an increasing recognition that microplastics contamination in soils has become an important threat for terrestrial ecosystems, and can interact with drought. In addition, due to the increasingly serious environmental pollution and the destruction of the ozone layer, the UV-B radiation to the earth's surface has gradually increased. However, we currently have no information about potential effects of microplastics, UV-B, and drought on plant communities. In order to make up for the vacancy, we conducted an experiment with grassland plant communities. Polyester fiber microplastics (absent, present), UV-B (fully transparent polythene film, attenuating UV-B radiation), and soil water conditions (well-watered, drought) were applied in a fully factorial design. A plant community consisting of four indigenous species and one invasive species, co-occurring in the terrestrial ecosystem of the northern temperate zone was established, and we investigated the effects of microplastics, UV-B, drought and their interactions on plant functional traits and plant community structure. We found that shoot and root biomass decreased with drought but increased with microfibers, and drought significantly decreased specific leaf area at the community level. Physiological and biochemical indexes of individual species and plant community were affected by microfibers, UV-B, drought and their interaction to a varying degree. More importantly, five species were divided into three clusters along PC1 corresponding to individuals from G. longituba and P. depressa, B. bipinnata and M. sativa, plus G. parviflora, which indicated that at the same conditions, G. parviflora would occupy unique ecological niches that affect the growth of native species. Our research offers insights into the mechanisms of the coexistence of native and invasive plants, as well as the ecological consequences of microplastics and other environment factors on plant communities.

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.

Carbon dynamics in the deciduous broadleaf tree Erman's birch (Betula ermanii) at the subalpine treeline on Changbai Mountain, Northeast China.

PREMISE OF THE STUDY: The growth limitation hypothesis (GLH) and carbon limitation hypothesis (CLH) are two dominant explanations for treeline formation. The GLH proposes that low temperature drives the treeline through constraining C sinks more than C sources, and it predicts that non-structural carbohydrate (NSC) levels are static or increase with elevation. Although the GLH has received strong support globally for evergreen treelines, there is still no consensus for deciduous treelines, which experience great asynchrony between supply and demand throughout the year. METHODS: We investigated growth and the growing-season C dynamics in a common deciduous species, Erman's birch (Betula ermanii), along an elevational gradient from the closed forest to the treeline on Changbai Mountain, Northeast China. Samples were collected from developing organs (leaves and twigs) and main storage organs (stems and roots) for NSC analysis. KEY RESULTS: Tree growth decreased with increasing elevation, and NSC concentrations differed significantly among elevations, organs, and sampling times. In particular, NSC levels varied slightly during the growing season in leaves, peaked in the middle of the growing season in twigs and stems, and increased continuously throughout the growing season in roots. NSCs also tended to increase or vary slightly in developing organs but decreased significantly in mature organs with increasing elevation. CONCLUSIONS: The decrease in NSCs with elevation in main storage organs indicates support for the CLH, while the increasing or static trends in new developing organs indicate support for the GLH. Our results suggest that the growth limitation theory may be less applicable to deciduous species' growth than to that of evergreen species.

Estimates of forest biomass carbon storage inLiaoning Province of Northeast China: a review and assessment.

Accurate estimates of forest carbon storage and changes in storage capacity are critical for scientific assessment of the effects of forest management on the role of forests as carbon sinks. Up to now, several studies reported forest biomass carbon (FBC) in Liaoning Province based on data from China's Continuous Forest Inventory, however, their accuracy were still not known. This study compared estimates of FBC in Liaoning Province derived from different methods. We found substantial variation in estimates of FBC storage for young and middle-age forests. For provincial forests with high proportions in these age classes, the continuous biomass expansion factor method (CBM) by forest type with age class is more accurate and therefore more appropriate for estimating forest biomass. Based on the above approach designed for this study, forests in Liaoning Province were found to be a carbon sink, with carbon stocks increasing from 63.0 TgC in 1980 to 120.9 TgC in 2010, reflecting an annual increase of 1.9 TgC. The average carbon density of forest biomass in the province has increased from 26.2 Mg ha(-1) in 1980 to 31.0 Mg ha(-1) in 2010. While the largest FBC occurred in middle-age forests, the average carbon density decreased in this age class during these three decades. The increase in forest carbon density resulted primarily from the increased area and carbon storage of mature forests. The relatively long age interval in each age class for slow-growing forest types increased the uncertainty of FBC estimates by CBM-forest type with age class, and further studies should devote more attention to the time span of age classes in establishing biomass expansion factors for use in CBM calculations.

Variation in carbon storage and its distribution by stand age and forest type in boreal and temperate forests in northeastern China.

The northeastern forest region of China is an important component of total temperate and boreal forests in the northern hemisphere. But how carbon (C) pool size and distribution varies among tree, understory, forest floor and soil components, and across stand ages remains unclear. To address this knowledge gap, we selected three major temperate and two major boreal forest types in northeastern (NE) China. Within both forest zones, we focused on four stand age classes (young, mid-aged, mature and over-mature). Results showed that total C storage was greater in temperate than in boreal forests, and greater in older than in younger stands. Tree biomass C was the main C component, and its contribution to the total forest C storage increased with increasing stand age. It ranged from 27.7% in young to 62.8% in over-mature stands in boreal forests and from 26.5% in young to 72.8% in over-mature stands in temperate forests. Results from both forest zones thus confirm the large biomass C storage capacity of old-growth forests. Tree biomass C was influenced by forest zone, stand age, and forest type. Soil C contribution to total forest C storage ranged from 62.5% in young to 30.1% in over-mature stands in boreal and from 70.1% in young to 26.0% in over-mature in temperate forests. Thus soil C storage is a major C pool in forests of NE China. On the other hand, understory and forest floor C jointly contained less than 13% and <5%, in boreal and temperate forests respectively, and thus play a minor role in total forest C storage in NE China.

An application of remote sensing data in mapping landscape-level forest biomass for monitoring the effectiveness of forest policies in northeastern China.

Monitoring the dynamics of forest biomass at various spatial scales is important for better understanding the terrestrial carbon cycle as well as improving the effectiveness of forest policies and forest management activities. In this article, field data and Landsat image data acquired in 1999 and 2007 were utilized to quantify spatiotemporal changes of forest biomass for Dongsheng Forestry Farm in Changbai Mountain region of northeastern China. We found that Landsat TM band 4 and Difference Vegetation Index with a 3 × 3 window size were the best predictors associated with forest biomass estimations in the study area. The inverse regression model with Landsat TM band 4 predictor was found to be the best model. The total forest biomass in the study area decreased slightly from 2.77 × 10(6) Mg in 1999 to 2.73 × 10(6) Mg in 2007, which agreed closely with field-based model estimates. The area of forested land increased from 17.9 × 10(3) ha in 1999 to 18.1 × 10(3) ha in 2007. The stabilization of forest biomass and the slight increase of forested land occurred in the period following implementations of national forest policies in China in 1999. The pattern of changes in both forest biomass and biomass density was altered due to different management regimes adopted in light of those policies. This study reveals the usefulness of the remote sensing-based approach for detecting and monitoring quantitative changes in forest biomass at a landscape scale.

[Soil organic carbon storage in different aged Larix gmelinii plantations in Great Xing' an Mountains of Northeast China].

A sampling plot investigation was conducted to study the soil organic carbon (SOC) storage in 0-40 cm layer in 10-, 15-, 26- and 61 years old Larix gmelinii plantations in Great Xing' an Mountains of Northeast China as well as the temporal variation pattern of the SOC source/sink during the plantation management after the clear cutting of primary L. gmelinii forest. With the increasing age of the plantations, the SOC storage increased after an initial decrease, and the inflection point was at a stand age between 15- and 26-years old. Compared with that of primary forest, the SOC storage of the plantations played a role of carbon source at early stage (10-26 years old), but gradually transformed into carbon sink then, with a SOC storage of 158.91 t x hm(-2) in 61-year-old plantation. The SOC storage of the plantations increased with soil depth initially, but was higher in upper soil layer than in deeper soil layer after the stand age being 26, which implied that human disturbance had strong effects on the vertical distribution of SOC. It was considered that the appropriate cutting age for the L. gmelinii plantations in Great Xing' an Mountains could be at least 60 years old.

[Soil organic carbon density and its influencing factors of major forest types in the forest region of Northeast China].

The five main forest types, i. e. larch forest, birch forest, coniferous mixed forest, broad-leaved mixed forest, and coniferous and broad-leaved mixed forest, with varied age classes (young, mid-aged, pre-mature, and over mature) were selected to investigate the variation of soil organic carbon density in the forest region of Northeast China. Results showed that both soil organic carbon content and density were relatively larger in the top soil layer across the five forest types, decreased gradually with soil depth, and varied insignificantly with either forest type or forest age class. The forest soil carbon density was concentrated in the top 20 cm of soil which accounted for 84.7% - 86.1%, 51.7% - 59.8% and 51.2% - 53.4% of total soil carbon density in the Daxing' an, Xiaoxing' an and Changbai mountains, respectively. The total soil organic carbon density decreased significantly with increasing latitude, which might be attributed mainly to the thickness of soil layers in forest region of Northeast China.

[Effects of altitudinal gradient on water use efficiency of Betula ermanii on the northern slope of Changbai Mountains, northeast China].

Taking Betula ermanii forests distributed at the altitudes 1800-2050 m on the northern slope of Changbai Mountains as test objects, and using leaf carbon isotope content (813 C) as an indicator of B. ermanii water use efficiency (WUE), this paper studied the effects of altitudinal gradient on the WUE of B. ermanji forests in the area. With the increase of altitude, the soil volumetric water content (VMC) and the leaf mass per area (LMA) of B. ermanji increased significantly, while the leaf water content (LWC) and soil temperature were in adverse. There was a significant positive correlation between leaf delta13 C and altitude, with the increment of leaf delta13 C being 1.013 % per hundred x (100 m)(-1), and the leaf delta13C was positively correlated with soil VWC and LMA but negatively correlated with soil temperature and LWC. Temperature was not the sole limiting factor for the distribution of treeline in Changbai Mountains, whereas the physiological drought of B. ermanii during its growing season caused by the different water and heat conditions and their interactions along the altitudinal gradient could be the other limiting factors.