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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.

Pinewood nematode, Bursaphelenchus xylophilus, as one of the greatest threats to pine trees, is spreading all over the world. During the nematode’s pathogenesis, plant microorganisms play important roles.The phyllosphere and rhizosphere bacterial and fungal communities associated with healthy P. koraiensis (PKa) and P. koraiensis infected by B. xylophilus at the early (PKb) and last (PKc) stages were analyzed. Pine wood nematode (PWD) could increase the phyllosphere and rhizosphere microbial community diversity, and slight shifts of the microbial diversity were observed at the early stage of infection. Generally speaking, an increase in microbial diversity with more serious symptomatic phase was obvious and visible. The phyllosphere and rhizosphere microbial community potentially changed caused by B. xylophilus infection of P. koraiensis. With the infection of B. xylophilus in P. koraiensis, Bradyrhizobium (rhizosphere bacteria), Massilia (phyllosphere bacteria), Phaeosphaeriaceae (rhizosphere 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.

We explored topography-dependent variations of spruce (Picea jezoensis var. komarovii) growth in response to climatic change, and abrupt decline in its climatic sensitivities to temperature under global warming in the Changbai Mountain, Northeast China. Variations in the mountain slope direction, being different in radiation intensity and soil moisture, might exert a profound influence on the growth-climate relationship, which potentially brings indeterminacy in sensitivity to temperature under climate warming. To better understand the spatial variation in this influence, we used dendrochronological methods to determine the relationship between the radial growth of spruce (P. jezoensis var. komarovii) and climate in three aspects at an elevation of approximate 1200 m in the Changbai Mountain. The results indicated obvious correlations among the three spruce chronologies, and the radial growth presented more positive correlations with spring temperature (rather than summer or winter temperature), with April temperature on the south-facing slope and negative with precipitation on the north- and west-facing slopes. Despite the sensitivities to temperature were abruptly declined by the increasing temperature, the year- occurrences were inconsistent with records from 1996, 1995 and 1989 on the north (in May), west (in May) and south (in Apr), respectively. The negative relationship with May precipitation has become stronger since 1982 on the north and west for the increasing amount of precipitation. Therefore, given the declined sensitivity of spruce growth to climate warming, which can be shown among three different slopes, the divergent point would be difficult to precisely disentangle in investigating the temporal stability base on the variation in species, habitat and data analytical method.

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.

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 (WSI

Although beam pumping unit is widely used, it has high energy consumption and is gradually replaced by new energy-saving equipment, such as submersible diaphragm pump. Submersible diaphragm pump has been used in oil production system because of its unique diaphragm structure and high pump efficiency, and has achieved good application effect. At the same time, some engineering application problems have also arisen, such as frequent cable damage, wax deposition or corrosion of oil pipe, and difficult monitoring of pump working condition. In order to solve these problems, the application of submersible diaphragm pump system based on non-metallic coiled tubing is studied. The system consists of non-metallic coiled tubing, submersible diaphragm pump, intelligent control unit and wellhead Christmas tree. In the application test of oil production engineering, the process data are compared with the conventional beam pumping unit, and the results show that the power consumption is more than 50% less than that of the conventional beam pumping unit. The application test shows that the system is easy to realize remote monitoring of oil wells and intelligent adjustment of process parameters, and is conducive to unattended well site, which has a good application prospect.

The water jacket heating furnace has become the widely used crude oil storage and transportation equipment in the oilfield. And the improvement of its thermal efficiency has become one key issue of energy conservation and emission reduction. The combustion system of the oilfield water jacket heating furnace is designed by combining support vector machine with PID control in this paper. The flow rate of heated medium is predicted by the support vector machine (SVM). According to the flow rate of heated medium, the air and fuel in the heating furnace are optimized to increase thermal efficiency and reduce emissions. Through the calculation and simulation, the response speed of the combustion control system is faster and the thermal efficiency has been improved.

International audience; Biodiversity plays a fundamental role in provisioning and regulating forest ecosystem functions and services. Above-ground (plants) and below-ground (soil microbes) biodiversity could have asynchronous change paces to human-driven land-use impacts. Yet, we know very little how they affect the provision of multiple forest functions related to carbon accumulation, water retention capacity and nutrient cycling simultaneously (i.e. ecosystem multifunctionality; EMF). We used a dataset of 22,000 temperate forest trees from 260 plots within 11 permanent forest sites in Northeastern China, which are recovering from three post-logging disturbances. We assessed the direct and mediating effects of multiple attributes of plant biodiversity (taxonomic, phylogenetic, functional and stand structure) and soil biodiversity (bacteria and fungi) on EMF under the three disturbance levels. We found the highest EMF in highly disturbed rather than undisturbed mature forests. Plant taxonomic, phylogenetic, functional and stand structural diversity had both positive and negative effects on EMF, depending on how the EMF index was quantified, whereas soil microbial diversity exhibited a consistent positive impact. Biodiversity indices explained on average 45% (26%–58%) of the variation in EMF, whereas climate and disturbance together explained on average 7% (0.4%–15%). Our result highlighted that the tremendous effect of biodiversity on EMF, largely overpassing those of both climate and disturbance. While above- (β = 0.02–0.19) and below-ground (β = 0.16–0.26) biodiversity had direct positive effects on EMF, their opposite mediating effects (β = −0.22 vs. β = 0.35 respectively) played as divergent pathways to human disturbance impacts on EMF. Our study sheds light on the need for integrative frameworks simultaneously considering above- and below-ground attributes to grasp the global picture of biodiversity effects on ecosystem functioning and services. Suitable management interventions could maintain both plant and soil microbial biodiversity, and thus guarantee a long-term functioning and provisioning of ecosystem services in an increasing disturbance frequency world.

Global warming-induced changes in tree-growth resilience to climate variations have been widely reported for mid- and high-latitude regions around the world. Most studies have focused on the spatial variability of trees in radial growth–climate relationships on Changbai Mountain in Northeast China, but little is known about temporal changes in tree growth in response to climate. We explored the stability of effect of climate variables on radial growth of Yezo spruce [Picea jezoensis Carr. var. komarovii (V.Vassil.) Cheng et L.K.Fu] at 1200, 1400, and 1600 m above sea level, representing low, middle, and upper ranges of the spruce–fir mixed forest on Changbai Mountain. The results showed that the relation between tree growth and climate did not vary with altitude, but the stability of the tree-growth–climate relationship did vary with altitude as the climate changed. Radial growth of Yezo spruce at all three elevations was influenced primarily by maximum temperature during May (Tmax5) and mean minimum temperature from January to March (Tmin1–3). More specifically, the relationship strengthened significantly at lower elevations, but weakened significantly at higher elevation, and fluctuated at mid elevations since 1980. Increase in Tmin1–3 and decrease in Tmax5 were the main reasons for the decrease in the radial growth at three altitudes. The findings of this study clarified that the decrease in radial growth on Changbai Mountain is not a “divergence problem” of an unexpected decrease in tree growth in response to an increase in mean temperature and provides a reference for using tree-ring data to reconstruct climate patterns and/or predict the growth of trees under various climate change scenarios.

Protected areas have become important tourism products that promoted as attractions by the tourism industry. Taking the Changbai Mountain Biosphere Reserve in Northeast China as a case, this study addresses visitor needs as a basis for developing a tourism strategy aimed at enhancing tourist opportunities at this reserve. A factor-cluster approach was employed to identify visitor segment profiles based on their visit motivations. Through random sampling, a pencil-and-paper questionnaire in Chinese language was collected from 637 domestic tourists in the study area. A principal components analysis of motivations revealed eight motivational factors, and four distinct groups of tourists–Nature travelers, Cultural landscape tourists, Food & shopping enthusiasts, and Eclectic adventurers–were identified. Understanding the differences in these visitor segments will help the management authority effectively analyze nature reserve attributes and provide alternative activities and services to tourists. Finally, within the dual framework of market segmentation and destination management some management recommendations and marketing implications are suggested.

Land use changes are a direct consequence of interactions between humans and nature. Analysing the spatial and temporal changes in habitat quality brought about by land use change can provide a scientific basis for ecological protection and land planning. Based on the analysis of land use change from 1990 to 2010 in Northeast China, we used the InVEST (integrated valuation of ecosystem services and trade-offs) module to evaluate habitat quality based on watershed subdivision. The results show that: (1) the main land use changes from 1990 to 2010 were the transition from grasslands and forest lands to agricultural lands, which led to a decrease in connectivity of landscape and an increase in fragmentation; (2) areas of high habitat quality were distributed north of the Greater Khingan Mountains, the region of the Lesser Khingan Mountains and east of the Changbai Mountains, while the central plain had low habitat quality; (3) agricultural lands had the largest effect on habitat degradation among all habitat threats. During these 2 decades, the contribution of agricultural lands to habitat degradation were 43.4% in 1990, 44.6% in 2000 and 43.9% in 2010; and, (4) at a landscape scale, patch density and splitting index present noticeable negative correlations with habitat quality index. Habitat quality was significantly affected by landscape fragmentation and decreased connectivity.

Intraspecific functional trait variability plays an important role in the response of plants to environmental changes. However, it is still unclear how the variability differs across three nested spatial scales (individual, plot, and site) and which determinants (climatic, soil, and ontogenetic variables) shape the trait variability. Along a latitudinal gradient in Korean pine broadleaved forest of northeast China, we quantified the extent of intraspecific variability of four functional traits in two dominant trees Pinus koraiensis and Fraxinus mandshurica at eight sites, including specific leaf area, leaf dry matter content (morphological traits) and leaf nitrogen content, leaf phosphorus content (physiological traits). Results showed a large trait variation within and between species (coefficient variation: 6.07–23.3%). The leaf physiological traits of F. mandshurica and morphological traits of P. koraiensis were more responsive at site scale, while the morphological traits of F. mandshurica and physiological traits of P. koraiensis were more responsive at individual scale. In addition, abiotic and biotic factors explaining functional trait variation differ markedly between the two tree species, with physiological trait of F. mandshurica being more associated with climate and soil, while traits variability in P. koraiensis was not affected by climate, soil, and ontogeny, except for leaf phosphorus content. Overall, we can predict that the physiological traits of broadleaved species tend to be more sensitive to environmental changes, while pines are more sensitive to competition. It is critical to determine which spatial scale and trait type should be taken into account in predictive models of vegetation dynamics.

The long-term stressful utilization of forests and grasslands has led to ecosystem degradation and C loss. Since the late 1970s China has launched six key national ecological restoration projects to protect its environment and restore degraded ecosystems. Here, we conducted a large-scale field investigation and a literature survey of biomass and soil C in China's forest, shrubland, and grassland ecosystems across the regions where the six projects were implemented (∼16% of the country's land area). We investigated the changes in the C stocks of these ecosystems to evaluate the contributions of the projects to the country's C sink between 2001 and 2010. Over this decade, we estimated that the total annual C sink in the project region was 132 Tg C per y (1 Tg = 1012 g), over half of which (74 Tg C per y, 56%) was attributed to the implementation of the projects. Our results demonstrate that these restoration projects have substantially contributed to CO2 mitigation in China.

Although the growth limitation hypothesis (GLH) is the most accepted physiological explanation for alpine treeline formation, the debate about its formation mechanisms still remains controversial due to contradictory findings from different studies. The functional difference between trees and alpine low-stature shrubs may hold answers, as shrubs grow well at higher elevations. We investigated carbon (C) storage in deciduous treeline species Betula ermanii (Erman’s birch) and two dominant shrubs (deciduous Vaccinium uliginosum and evergreen Rhododendron aureum), which naturally grow next to each other at the treeline ecotone on Changbai Mountain, Northeast China. We determined growth and non-structural carbohydrate (NSC) concentrations in organs with increasing elevation at the mid-growing season. Results showed that in the treeline ecotone soil temperature was lower than tree canopy air temperature due to unobvious aerodynamic decoupling near the ground. Species growth consistently decreased with increasing elevation, while NSC concentrations responded differently to elevation between trees and shrubs. An elevational increase and decrease in NSC were observed in leaves and woody organs, respectively, of B. ermanii. NSC concentrations in each organ significantly increased with increasing elevation for R. aureum but decreased for V. uliginosum. At the treeline, shrubs had higher values than B. ermanii in NSC, ratios of soluble sugars to starch in leaves, and leaf mass per area. Organ dependence of NSC with increasing elevation in Betula trees provided partial support for the GLH, while R. aureum and V. uliginosum provided strong support for the GLH and carbon limitation hypothesis, respectively. These imply that alpine shrubs may have evolved to maintain more advantageous C balance and functional features than did trees as an adaptation to higher-elevation climates.

Excessive logging in China is the major cause of poor forest quality, degraded ecosystem functions, and near exhaustion of harvestable resources of the country’s natural forests. An overall extended moratorium on logging in the country’s natural forests has been launched since 2015, which is a suggested method for the gradual recovery of the structure and functions of these forests. However, the main purpose to manage the degraded natural forest after the moratorium remains not yet clear. This paper firstly reviews China’s natural forest management history and clarifies the causes accounting for natural status duo, and then analyses changes in domestic natural forests and timber supply and demand in China, identifies the problems related to the sustainable operation of natural forests, especially those requiring immediate attention. Results shows that as the demand for timber continues to increase rapidly, China will experience a severe imbalance between timber supply and demand. In the long run, timber imports alone cannot meet increasing domestic demands, natural forests remain the primary source of wood products. Many issues concerning management practices and operations technology remain, including ineffective overall spatial zoning, rough operation and management of timber forests, and financial difficulties in forested areas. All of these issues have prevented natural forests from realizing both their ecological functions and timber resource potential. A moratorium on timber harvesting would offer a valuable opportunity for natural forests to recover from decades of excessive logging, as well as an exciting chance to develop sustainable operational practices, ecological functions promotion and relevant technologies. In summary, strategies for the sustainable management and ecosystem services promotion of natural forests during a harvesting moratorium are suggested.

Wind-disturbed (1986) and undisturbed primary forest areas (controls) on Changbai Mountain (China) were studied to compare levels of soil nitrogen mineralization. Soil samples were collected at 0–10 cm (topsoil) and 10–20 cm (subsoil) depths from the vegetation zones of a broadleaf Korean pine forest (BKPF), spruce-fir forest (SFF), and an Erman's birch forest (EBF) at different altitudes. Nitrogen status and mineralization characteristics were studied in the soil samples from a wind-disturbed area where vegetation cover has been restored after 30 years of regrowth. Soil organic carbon (SOC) and total nitrogen (TN) contents in the topsoil layer of the three vegetation types were significantly higher than in the subsoil layer. SOC and TN contents in the topsoil layer increased, and soil C/N ratio significantly decreased with increasing altitude. No significant differences in SOC, TN or pH were detected in the wind-disturbed and control area soils of BKPF and EBF. SOC and TN levels in the subsoil layer of SFF were significantly higher in wind-disturbed than in control areas. The topsoil C/N ratios of BKPF and SFF were significantly higher in the control area vs. the wind-disturbed area. After 21 d incubation, inorganic nitrogen contents (ammonium nitrogen NH 4 + -N and nitrate nitrogen NO 3 − -N) in the soils of BKPF, SFF and EBF increased in both the wind-disturbed and control areas. Ammonium nitrogen (NH 4 + -N) was the primary inorganic form of nitrogen. The changes in the amount of NH 4 + -N formed from ammonification contributed to the 57.1–76.2% total amount of nitrogen mineralized (net nitrogen mineralization) and the net nitrogen mineralization rate. The nitrogen mineralization process was mainly the result of net ammonification. Correlation analysis on the soil nitrogen mineralization rate and chemical properties showed that the ammonification rate had strong positive correlation with SOC and the C/N ratio. Nitrification rate was highly correlated with SOC and TN contents, as well as soil pH. Net nitrogen mineralization rate was significantly correlated with SOC and TN contents, C/N ratio, and soil pH. Multiple comparisons analysis of variance (ANOVA) demonstrated that soil nitrogen mineralization was greatly influenced by vegetation type, soil depth, and wind disturbance in the forest soils at different altitudes. Net ammonification and net nitrogen mineralization were significantly affected by wind disturbance. The vegetation cover has undergone restoration for nearly 30 years in the wind-disturbed area on Changbai Mountain, but our data demonstrate that differences in soil quality between primary forest and wind-disturbed areas remain significant due to the different vegetation types.

The Natural Forest Protection Program (NFPP) is one of the key ecological forestry programs in China. It not only facilitates the improvement of forest ecological quality in NFPP areas, but also plays a significant role in increasing the carbon storage of forest ecosystems. The program covers 17 provinces, autonomous regions, and municipalities with correspondingly diverse forest resources and environments, ecological features, engineering measures and forest management regimes, all of which affect regional carbon storage. In this study, volume of timber harvest, tending area, pest-infested forest, fire-damaged forest, reforestation, and average annual precipitation, and temperature were evaluated as factors that influence carbon storage. We developed a vector autoregression model for these seven indicators and we studied the dominant factors of carbon storage in the areas covered by NFPP. Timber harvest was the dominant factor influencing carbon storage in the Yellow and Yangtze River basins. Reforestation contributed most to carbon storage in the state-owned forest region in Xinjiang. In state-owned forest regions of Heilongjiang and Jilin Provinces, the dominant factors were forest fires and forest cultivation, respectively. For the enhancement of carbon sequestration capacity, a longer rotation period and a smaller timber harvest are recommended for the Yellow and Yangtze River basins. Trees should be planted in state-owned forests in Xinjiang. Forest fires should be prevented in state-owned forests in Heilongjiang, and greater forest tending efforts should be made in the state-owned forests in Jilin.

Pinus koraiensis is a conifer species of ecological and economic importance in northeast China that has been excessively exploited in recent years. A clonal seed orchard (CSO) was established including potentially genetically differentiated provenances from the whole distribution area, we applied nine simple sequence repeat (SSR) makers to study the genetic diversity and population structure of six maternal populations as well as their progeny populations. The results showed a high genetic diversity in both maternal and progeny populations, with the average expected heterozygosity of 0.617 and 0.632, respectively. The level of genetic diversity in the progeny populations was slightly higher than that in the maternal populations, and almost all diversity descriptors were correlated between maternal and progeny populations, indicating that the CSO could preserve the established species’ gene pool. An overall low level of genetic differentiation of P. koraiensis (FST = 0.029 and 0.025 for maternal and progeny populations) was found. The six maternal populations clustered into two groups by Bayesian cluster analysis with the two northernmost populations comprising one group and the other four populations as another genetically differentiated group, potentially indicating regional adaptation. The northern group had significantly higher levels of within population diversity. Population structure was not evident anymore in the progeny populations, suggesting that mating among differentiated provenances within the CSO homogenized the different gene pools, although differences in diversity were still maintained. These results will inform efforts for the conservation and management of P. koraiensis and provide guidance for future studies of population genetics and breeding programs.

This article seeks to develop a fuller understanding of the social and attraction motives of domestic tourists who visit the Changbai Mountain Biosphere Reserve (CMBR) in Northeastern China. To do so, ecotourists are compared to general travelers visiting this area. A questionnaire was employed to collect data on visitor characteristics and motivations, responses to which were then analyzed via descriptive statistics, T-tests and principal component factor analysis. Results showed that 16% of the visitors to this area were classified as ecotourists, while the remainder general travelers. Five motivations displayed significant differences (P

Soil aggregation and soil organic carbon (SOC) mineralization are affected by soil properties, microbes and litter input, all of which vary with changes in temperature, precipitation and vegetations. In order to explore SOC dynamics in natural mature forest ecosystems, this study analyzed the variation of soil aggregates and SOC mineralization along an altitudinal gradient on Changbai Mountain in northeast China. Soil samples collected at four altitudinal sites were fractionated into different size of aggregates. SOC mineralization was measured by incubating soils at constant temperature. Results revealed that proportions of macro-aggregates (5–2 mm, 2–1 mm) increased with increasing altitude, while proportions of micro-aggregates (0.25–0.053 mm, Korean pine and broad-leaved mixed forest > Erman's birch mixed Spruce-fir forest > Spruce-fir mixed forest. Correlation and linear regression analysis revealed that potential mineralized carbon (C0) positively correlated with microbial biomass carbon, readily oxidizable carbon and SOC. Turnover coefficient k, which represents the turnover rates of C0, was positively correlated with proportions of macro-aggregates and negatively correlated with proportions of aggregates 1–0.25 and 0.25–0.053 mm. In conclusion, SOC mineralization was controlled by microbial activity, quality and quantity of SOC and soil structures. Greater proportions of macro-aggregates at higher altitude suggest that SOC might turnover more quickly than that at lower altitudes. Hence more attention should be paid to soils at higher altitude in the future.

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.

The semi-arid grasslands in Inner Mongolia have been degraded as a result of long-term grazing and poor grassland management. A series of ecological restoration strategies have been implemented to enhance the ecosystem services of China's grasslands. To understand the response of ecosystem C and N to grazing exclusion within a nationwide conservation project-Returning Grazing Lands to Grasslands (RGLG), the C and N storages in different parts of the plant-soil system as well as soil microbial biomass carbon (MBC) and nitrogen (MBN) contents were determined and compared between three grazing exclusion sites (6 years) and the paired adjacent grazing sites in the Hulunbuir grassland of Inner Mongolia. Our results showed that the exclusion of grazing for 6 years resulted in significant increases of ecosystem biomass and soil C and N contents, leading to a substantial restoration of ecosystem C and N storage. The average C and N accumulation rates in the whole ecosystem were 173.6 g C m(-2) year(-1) and 19.8 g N m(-2) year(-1), respectively. The accumulation of C and N in soil contributed to more than 87.6% and 98.2% of the increases in ecosystem C and N, respectively, indicating that the restoration of ecosystem C and N were mainly due to the increase of C and N in soil after exclusion of grazing. The higher MBC and MBN in exclosure sites than grazing sites might be partly because of the enhanced organic matter inputs from plant litter and root exudates. The significant correlations between soil organic matter and microbial biomass suggested that soil microbial biomass could be a sensitive indicator of the soil C and N dynamics. These results indicated that exclusion of grazing pressure within the RGLG project is an effective restoration approach to control grassland degradation in this region. However, more comprehensive multidisciplinary studies are needed to evaluate the effectiveness of the RGLG project and to improve the management strategies for grassland restoration. (C) 2014 Elsevier B.V. All rights reserved.

Flooded peat wetlands are an important global carbon pool and are relatively sensitive to frost degeneration due to global climate change. To study the dynamics of greenhouse gas (GHG) formations in the soil of a flooded peat marsh in response to freeze–thaw processes, CO 2 , CH 4 and N 2 O fluxes and gas concentrations at different soil depths were measured in a flooded peat marsh in Northeast China during a freeze–thaw period (from November 2004 to July 2005). During the freeze period, the gas concentrations underneath the frozen soil increased as the freeze developed until the soil completely froze in the root (15−35 cm) and peat (35−80 cm) layers. The highest gas concentrations accumulated in the gley layer (80−120 cm) when the greatest freeze depth formed. During the thaw period, the gas concentrations increased above the frozen layer (15−60 cm); in contrast, the gas concentrations underneath the frozen layer (60–120 cm) rapidly decreased when the bottom of the frozen layer began to thaw. GHG emissions from the marsh were not correlated with gas concentrations underneath the frozen layer during the freeze period but were significantly correlated with gas concentrations above the frozen layer (15−60 cm) during the thaw period. The study suggested that large changes in GHG formation dynamics occurred underneath the frost in the flooded peat marsh when the frost began to thaw due to gas physical diffusion within the peat layer.

Based on the data from China’s Seventh Forest Inventory for the period of 2004–2008, area and stand volume of different types and age-classes of plantation were used to establish the relationship between biomass density and age of planted forests in different regions of the country. Combined with the plantation area in the first-stage of the Natural Forest Protection (NFP) program (1998–2010), this study calculated the biomass carbon storage of the afforestation in the first-stage of the program. On this basis, the carbon sequestration potential of these forests was estimated for the second stage of the program (2011–2020). Biomass carbon storage of plantation established in the first stage of the program was 33.67 Tg C, which was majority accounted by protection forests (30.26 Tg C). There was a significant difference among carbon storage in different regions, which depended on the relationship of biomass carbon density, forest age and plantation area. Under the natural growth, the carbon storage was forecasted to increase annually from 2011 to 2020, reaching 96.03 Tg C at the end of the second-stage of the program in 2020. The annual growth of the carbon storage was forecasted to be 6.24 Tg C/yr, which suggested that NFP program has a significant potential for enhancing carbon sequestration in plantation forests under its domain.

The Natural Forest Protection (NFP) program is one of the Six Key Forestry Projects which were adopted by the Chinese Government since the 1980s to address important natural issues in China. It advanced to protecting and restoring the structures and functions of the natural forests through sustainable forest management. However, the role of forest carbon storage and tree carbon pool dynamics since the adoption of the NFP remains unknown. To address this knowledge gap, this study calculated forest carbon storage (tree, understory, forest floor and soil) in the forest region of northeastern (NE) China based on National Forest Inventory databases and field investigated databases. For tree biomass, this study utilized an improved method for biomass estimation that converts timber volume to total forest biomass; while for understory, forest floor and soil carbon storage, this study utilized forest type-specific mean carbon densities multiplied by their areas in the region. Results showed that the tree carbon pool under the NFP in NE China functioned as a carbon sink from 1998 to 2008, with an increase of 6.3 Tg C/yr, which was mainly sequestrated by natural forests (5.1 Tg C/yr). At the same time, plantations also acted as a carbon sink, reflecting an increase of 1.2 Tg C/yr. In 2008, total carbon storage in forests covered by the NFP in NE China was 4603.8 Tg C, of which 4393.3 Tg C was stored in natural forests and 210.5 Tg C in planted forests. Soil was the largest carbon storage component, contributing 69.5%–77.8% of total carbon storage; followed by tree and forest floor, accounting for 16.3%–23.0% and 5.0%–6.5% of total carbon storage, respectively. Understory carbon pool ranged from 1.9 to 42.7 Tg C, accounting for only 0.9% of total carbon storage.

The treeline on Changbai Mountain controlled by low temperature and water stress, has not reached the position most commonly expected. Treeline pattern is an important consideration in exploring the general mechanisms controlling the response of treelines to climatic change. However, most of the present conclusions were derived from evergreen and/or conifer treeline, it is still not clear about the deciduous treeline. This study analyzed concentrations of non-structural carbohydrates (NSC) and their components (total soluble sugars and starch) in tree tissues of the deciduous species Erman’s birch (Betula ermanii) at four points along an elevational gradient ranging from 1,908–2,058 m a.s.l at the end of the growing season on Changbai Mountain in Northeast China. The mean 10-cm soil temperature of 8.2 °C under trees across the 129-day growing season at the treeline in this region was higher than that of the average threshold temperature found at treeline positions in the global and China’s climate studies. However, altitudinal trends of NSC concentrations increased significantly in all tissue types along the altitudinal gradients, revealing no depletion of carbon reserves at the treeline on Changbai Mountain. At the same time, the pronounced variation of δ13C in leaves and aged branches suggested that low temperature and water stress may simultaneously be operating at high altitudes to restrict the growth and NSC accumulation in trees above the treeline. In light of the above, we conclude that treeline formation on Changbai Mountain is no carbon depletion at the end of growing season, and most likely the result of sink limitation reflecting the combined effects of low temperature and water stress that determined the actual position of the treeline.

Land use changes are known to alter soil organic carbon (SOC) and microbial properties, however, information about how conversion of natural forest to agricultural land use as well as plantations affects SOC and microbial properties in the Changbai Mountains of Northeast China is meager. Soil carbon content, microbial biomass carbon (MBC), basal respiration and soil carbon mineralization were studied in five selected types of land use: natural old-growth broad-leaved Korean pine mixed forest (NF); spruce plantation (SP) established following clear-cutting of NF; cropland (CL); ginseng farmland (GF) previously under NF; and a five-year Mongolian oak young forest (YF) reforested on an abandoned GF, in the Changbai Mountains of Northeast China in 2011. Results showed that SOC content was significantly lower in SP, CL, GF, and YF than in NF. MBC ranged from 304.4 mg/kg in CL to 1350.3 mg/kg in NF, which was significantly higher in the soil of NF than any soil of the other four land use types. The SOC and MBC contents were higher in SP soil than in CL, GF, and YF soils, yielding a significant difference between SP and CL. The value of basal respiration was also higher in NF than in SP, CL, GF, and YF. Simultaneously, higher values of the metabolic quotient were detected in CL, GF, and YF soils, indicating low substrate utilization of the soil microbial community compared with that in NF and SP soil. The values of cumulative mineralized carbon and potentially mineralized carbon (C0) in NF were significantly higher than those in CL and GF, while no significant difference was observed between NF and SP. In addition, YF had higher values of C0 and C mineralization rate compared with GF. The results indicate that conversion from NF into agricultural land (CL and GF) uses and plantation may lead to a reduction in soil nutrients (SOC and MBC) and substrate utilization efficiency of the microbial community. By contrast, soils below SP were more conducive to the preservation of soil organic matter, which was reflected in the comparison of microbial indicators among CL, GF, and YF land uses. This study can provide data for evaluating soils nutrients under different land use types, and serve as references for the rational land use of natural forest in the study area.

Old-growth forest ecosystems are large carbon pools, and recent research has found that old-growth forests generally serve as global carbon sinks. However, the impact of climate change on the capacity for carbon sequestration in old-growth forest ecosystems is uncertain. Combining data from 30-year monitoring of permanent plots with that measuring variations in radial growth of dominant trees in an old-growth forest on Changbai Mountain in Northeast China, this study investigated the net biomass carbon sequestration and the effects of climate warming on carbon sequestration for dominant living trees in this forest ecosystem. The results showed that in 2010 biomass carbon density for living trees was 201.22 t ha−1 in Korean pine and broad-leaved mixed forest (KBF), 106.46 t ha−1 in spruce-fir forest (SFF), and 89.49 t ha−1 in Erman’s birch forest (EBF). During the past 30 years the net biomass carbon density has increased in KBF and EBF, with annual net increases of 1.79 t ha−1 and 1.22 t ha−1, respectively; while net carbon density has decreased in SFF, with an annual net decrease of 0.55 t ha−1. Despite the increase of carbon density in KBF, climate warming has contributed to a decrease of 0.96 t ha−1 in biomass carbon sequestration for the period of 1981–2010, an amount equivalent to 1.8% of total stand biomass carbon increase. The increase in net carbon density in KBF was primarily age- or size-related, since that forest is still maturing. The decreased density in SFF may be caused by climate-induced radial growth decline and mortality of dominant trees in these stands. For the period of 1981–2010, climate-induced decrease of carbon sequestration in SFF was 7.30 ha−1. Wind-related tree mortality in SFF may have led to the stand carbon sequestration decrease of 75.09 t ha−1, about 10.3 times that induced by climate warming. In EBF, climate warming has led to a small increase in stand carbon sequestration, and the increase in net carbon density was also primarily age- or size-related, reflecting the fact that this forest is also still maturing. Our study also suggests that the dominance of Korean pine in KBF will decrease and that of Manchurian ash will increase under continuing climate warming, which is in agreement with the results from previous forest models.

Tree radial growth in mountainous areas is subject to complex environmental influences, and the response of radial growth to climate varies with elevation. To detect spatial variation and temporal instability in the climate–growth relationship for Korean pine (Pinus koraiensis Sieb. et Zucc) in Northeast China, we used dendrochronological analyses to examine radial growth–climate relationships along an altitudinal gradient in different forests on Changbai Mountain. Results confirmed the general conclusion that the climate–growth relationship varies with altitude. More specifically, at lower elevations Korean pine radial growth was controlled mainly by precipitation, while at the upper limit of its higher elevation zone it was much more affected by minimum temperature. Furthermore, these effects have become stronger since the temperature began increasing more rapidly in 1970 than before. In effect, radial growth decreased at lower elevations under climate change characterized by warming and drought, but increased at higher elevations. These results showed that long-term climate sensitivity varies strongly across altitudinal gradients and may be characterized by abrupt temporal shifts and differing trends in drought. The findings of this study will assist in simulating radial growth and distribution dynamics for Korean pine under various global climate change scenarios.

Forestry development in China has undergone a series of reforms over the past six decades. This article examines temporal changes in forest resources and policies, the current status of forestry, and future challenges toward sustainable forest management in China. Excessive logging in the 1950s to 1980s badly damaged the nation’s forests, but the adoption of enlightened forest policies in the late 1990s has led to increases in China’s total forest area and growing stock. Forest degradation was ecologically and economically costly, and rehabilitation processes have become increasingly more expensive. The low quality and young age of forest resources, loss of natural forests, and more difficulties in afforestation and reforestation pose severe challenges for China’s sustainable forestry. It is critically important for China to enhance forest productivity through intensive management, strengthen enforcement, and educational programs for protecting and restoring natural forests, narrow the gap between domesti...

Changbai Mountain Natural Reserve (1,985 km 2 and 2,734 m a.s.l.) of Northeast China is a typical ecosystem representing the temperate biosphere. The vegetation is vertically divided into 4 dominant zones: broad - leaved Korean pine forest (annual temperature 2.32°, annual precipitation 703.62 mm), dark coniferous forest (annual temperature -1.78°C, annual precipitation 933.67 mm), Erman's birch forest (annual temperature -2.80°C, annual precipitation 1,002.09 mm) and Alpine tundra (annual temperature -3.82°C, annual precipitation 1,075.53 mm). Stud - ies of soil carbon (C) and nitrogen (N) mineralization have attracted wide attention in the context of global climate change. Based on the data of a 42-day laboratory incubation experiment, this paper investigated the relationship between soil moisture and mineralization of C and N in soils with different vegetation types on the northern slope of the Natural Reserve Zone of Changbai Mountain. The elevation influence on soil C and N mineralization was also discussed. The results indicated that for the given vegetation type of Changbai Mountain the C and N mineralization rate, potential mineralizable C (C 0 ) and potential rate of initial C mineralization (C 0 k) all increased as the soil moisture rose. The elevation or vegetation type partially affected the soil C and N mineralization but without a clear pattern. The moisture-elevation interaction significantly affected soil C and NO 3 - -N mineralization, but the effect on NH 4 + -N mineralization was not significant. The complex mechanism of their impact on the soil C and N mineralization of Changbai Mountain remains to be studied further based on data of field measurements in the future.

International audience; AbstractKey messageForty years after clear-cutting mixed old-growth forest (broadleaf/Korean pine) in the Changbai Mountain area (Northeast China), a mixed forest with natural broadleaf regeneration and larch plantation displayed larger microbial biomass and activity in the soil than either a naturally regenerated birch forest or a monospecific spruce plantation.ContextClear-cutting with limited restoration effort was until the end of the twentieth century the norm for managing primary forests in Northeast China. Forest restoration plays an important role in the recovery of soil quality after clear-cutting, but the effects of different regeneration procedures on forest soil quality remain poorly known in Northeast China.AimsWe assessed the effects of three regeneration procedures, i.e., (i) naturally regenerated birch forest, (ii) spruce plantation, and (iii) naturally regenerated broadleaf species interspersed with planted larch on soil quality and microbial activity in the Changbai Mountain area. An old-growth mixed broadleaf/Korean pine forest was used as a reference.MethodsPhysical and chemical properties and microbial biomass were recorded in the soil. Basal respiration and carbon mineralization were measured with a closed-jar alkali-absorption method.ResultsMicrobial biomass was smaller in the birch forest and spruce plantation than in the old-growth and the mixed broadleaf/larch forests. Moreover, microbial biomass, microbial quotient, and potentially mineralizable carbon were larger in the mixed broadleaf/larch than in the birch forest, while no difference was found between spruce plantation and birch forest for microbial biomass and microbial quotient. Basal respiration and metabolic quotient were larger in the birch forest as compared to the three other forest types, indicating a larger energy need for maintenance of the microbial community and lower microbial activity in the naturally regenerated birch forest.ConclusionMixed broadleaf/larch forest displayed a larger microbial biomass and higher substrate use efficiency of the soil microbial community than either naturally regenerated birch forest or spruce plantation. The combined natural and artificial regeneration procedure (mixed broadleaf-larch forest) seems better suited to restore soil quality after clear-cutting in the Changbai Mountain.

Height-diameter relationship is one of the most important stature characteristics of trees. It will change with climatic conditions because height and diameter growth displays different sensitivities to climatic factors such as temperature. Detecting and understanding changes in the stature of trees growing along altitudinal gradients up to their upper limits can help us to better understand the adaptation strategy of trees under global warming conditions. On Changbai Mountain in northeastern China, height-diameter datasets were collected for 2723 Erman’s birch (Betula ermanii Cham.) in the alpine treeline ecotone in 2006 and 2013, and for 888 Erman’s birch, spruce (Picea jezoensis Siebold & Zucc. Carr.), larch (Larix olgensis A. Henry), and fir (Abies nephrolepis Trautv. ex Maxim.) along an altitudinal gradient below the alpine treeline in 2006. These datasets were utilized to explore both changes in the stature of birch at the alpine treeline over time and variations in tree stature of different tree species across altitudes at a given time point (2006). Results showed that birch saplings (140 cm became more tapered in the alpine treeline ecotone. The stature of birch along the altitudinal gradient became more tapered from 1700 to 1900 m above see level (a.s.l.) and then became more stunted from 1900 to 2050 m a.s.l., with 1900 m a.s.l. being the altitudinal inflection point in this pattern. The treeline birch, due to its great temperature magnitude of distribution, displayed higher stature-plasticity in terms of its height-diameter ratio than the lower elevation species studied. The stature of birch is strongly modulated by altitude-related temperature but also co-influenced by other environmental factors such as soil depth and available water, wind speed, and duration and depth of winter snow cover. The high stature-plasticity of birch makes it fare better than other species to resist and adapt to, as well as to survive and develop in the harsh alpine environment.

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, PLoS ONE, 8 (8), ISSN:1932-6203

We studied the effect of freezing-thawing on nitrogen (N) mineralization of four vegetation soils from typical vegetation zones of Changbai Mountain with a laboratory incubation experiment. The soils were treated with two levels of soil water content, representing the low and high soil water contents found during late autumn and early spring in Changbai Mountain, respectively, and underwent cycling of freezing at −5 or −25°C and thawing at 5°C up to 15 times. The main purpose of this study was to examine the effects of freezing temperature, frequency of freezing-thawing cycles, and soil water content on N mineralization of four soils to reveal the different effects of spring and autumn freezing-thawing on soil N mineralization in Changbai Mountain. The results showed that inorganic N in the soils increased 1.67–26.77 times after 15 cycles of freezing-thawing, but N mineralization rate decreased with increased cycling of freezing-thawing. The lower freeze temperature and higher soil water content generally enhanced soil N mineralization. The results implied that freezing-thawing of vegetation soils to increase soil N mineralization to favor the growth of plants, and also increase the possibility of runoff loss of soil nutrients, is more effective in the spring than in the autumn.

Studies of the history and current status of forest resources in Northeast China have become important in discussions of sustainable forest management in the region. Prior to 1998, excessive logging and neglected cultivation led to a series of problems that left exploitable forest reserves in the region almost exhausted. A substantial decrease in the area of natural forests was accompanied by severe disruption of stand structure and serious degradation of overall forest quality and function. In 1998, China shifted the primary focus of forest management in the country from wood production to ecological sustainability, adopting ecological restoration and protection as key foci of management. In the process, China launched the Natural Forest Conversion Program and implemented a new system of Classification-based Forest Management. Since then, timber harvesting levels in Northeast China have decreased, and forest area and stocking levels have slowly increased. At present, the large area of low quality secondary forest lands, along with high levels of timber production, present researchers and government agencies in China with major challenges in deciding on management models and strategies that will best protect, restore and manage so large an area of secondary forest lands. This paper synthesizes information from a number of sources on forest area, stand characteristics and stocking levels, and forest policy changes in Northeastern China. Following a brief historical overview of forest harvesting and ecological research in Northeast China, the paper discusses the current state of forest resources and related problems in forest management in the region, concluding with key challenges in need of attention in order to meet the demands for multi-purpose forest sustainability and management in the future.

In this paper, an incubation test with soil columns was carried out for 35 days to study the dynamics of DOC leaching from the organic layers (2 approximately 13 cm) of two meadow marsh soils, and the correlation of DOC release with soil respiration, NH4+ formation, and leachate pH. The results showed that in the first week, DOC release presented a fast decrease, and then held on a steady level, which could be well described by one order exponential equation (R20.96, P0.05). During 35 days incubation, the cumulative release of DOC from two test soils was 210.9 microg C x g(-1) and 506.58 microg C x g(-1), and the cumulative emission of CO2 was 679.64 microg C x g(-1) and 455.54 microg C x g(-1), respectively. It was suggested that in the course of incubation, the lower DOC release might be related to the microbial carbon limitation because of the greater CO2 production rate. A significantly positive correlation was found between DOC release and NH4+ formation (rXI = 0.886, P0.05; rXII = 0.972, P0.01), while no significant correlation was observed between DOC release and leachate pH. Multiple regression analysis showed that the nitrogen mineralization potential of meadow marsh soil was the main factor affecting DOC production.