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Regeneration success of forests is strongly dependent on symbiotic microorganisms, that is, arbuscular mycorrhiza (AM) and ectomycorrhiza (ECM). In the northeastern part of Asia, larch and birch are used as timber resources, and in the south, fir, cedar, cypress, and oak are used as timber resources. Planted forests have reached the time of harvesting and/or thinning, and after the forestry practices, it is expected that they will become mixed forests equipped with resistance to weather damage; that is, drought, heat, typhoons, etc. On the other hand, the physical production environment has changed greatly, therefore, we investigated the growth of the major trees and the role of mycorrhizal fungi in the northeastern Asia. Elevated O3 decreased growth, colonization rates of ECM, and the biodiversity; however, elevated CO2 moderated or increased them in larch. Except for disease of rot and damping off, we discuss wise use of symbiotic microbe in far East Asia.

Heavy metal (Cu, Mn, Zn, Pb, and Cd) concentrations were measured in the leaves of Sabina chinensis and Platycladus orientalis collected from urban, suburban, and rural sites in Tianjin, China. Photosynthetic pigment contents, reactive oxygen species content, malondialdehyde (MDA) content and antioxidant enzyme activity were investigated, providing physiological response parameters. Our comparison of the sites revealed that urbanization significantly influenced the heavy metal concentrations in both plant leaves. At the rural site, both plant leaves exhibited the lowest heavy metal accumulation. The highest Cu, Mn, and Zn concentrations were found in S. chinensis leaves from the urban site; the highest Pb and Cd concentrations were found in P. orientalis leaves from the urban site. These results indicate that the urban site contained larger heavy metal concentrations in the plant leaves that may reflect the anthropogenic emission gradient. It is also found that S. chinensis may be used to monitor airborne heavy metal pollution because it is highly quick response to heavy metals, while P. orientalis may be used for mitigation due to its high resistance. The results of this study can contribute to the development of monitoring and environmental management plans by providing information on sensitive and resistant tree species for city greening in North China.

Elevated ozone (O

BackgroundDeclines in plant biodiversity often have negative consequences for plant community productivity, and it becomes increasingly acknowledged that this may be driven by shifts in soil microbial community composition. These relationships have been well-established in grasslands, and few studies also indicate that fungi play a role in driving tree diversity-productivity relationships in forests. However, the role of bacteria and archaea, which are also highly abundant in forest soils and perform pivotal ecosystem functions, has been largely overlooked. Here, we investigated how tree and shrub richness affects stand-level tree productivity via modulating bacterial and archaeal community diversity and composition. We used a landscape-scale, subtropical tree biodiversity experiment (BEF-China) where tree (1, 2 or 4 species) and shrub richness (0, 2, 4, 8 species) were modified.ResultsOur results showed that tree and shrub species richness affected bacterial diversity, community composition, and co-occurrence networks, but such effects were marginal for archaea. Both tree and shrub species richness increased stand-level tree productivity by modulating soil microbial community composition, with the effects being mediated via increases in soil C:N ratios.ConclusionsOur findings imply the importance of bacterial and archaeal communities in driving the relationship between plant diversity and productivity in subtropical forests and highlight that we may require better a understanding of prokaryotic communities in forest soils.

Larch species are widely distributed in the northern hemisphere where permafrost and seasonal frozen soil exist. This species with heterophyllous shoots has been intensively planted in northeast Asia as well as in northeast China as the principal afforestation species for restoring agricultural lands to forests from 1999. Although approximately 15 species exist in the northern hemisphere and they are easy to hybridize. Among them, Japanese larch grows the fastest and was exported to Europe as a breeding species from early 20s. Although Japanese larch is tolerant to cold, it suffered from various biological stresses. After nearly 40 years of vigorous breeding effort, hybrid larch F1 (Dahurian larch × Japanese one) was developed with simple propagation methods. With the use of free-air CO2 enriched (FACE) systems, we revealed growth responses of the F1 and its parent larches to environmental conditions. From experiments, F1 showed high responses to elevated CO2 and O3 but not so much to N loading. As future perspectives for larch plantations as an important eco-environmental resource, we expect to afforest F1 seedlings infected with ectomycorrhizae (e.g., Suillus sp.) for efficient afforestation at nutrient-poor sites and at the same time for the production of delicious mushrooms.

Inland river basins include critical habitats and provide various ecosystem services in extremely arid lands. However, we know little about the distribution patterns of soil fungal communities in these river basins. We investigated the distribution patterns of soil fungal communities from the riparian oasis zone (ROZ) to the circumjacent desert zone (CDZ) at the lower reaches of the Heihe River. The results indicated that soil fungal communities were mainly dominated by the phyla Ascomycota and Basidiomycota across all samples. The dominant soil fungi taxa were significantly different between ROZ and CDZ habitats at both the phylum and genus levels. Fungal alpha diversity was mainly affected by spatial factors and plant functional traits, and Pearson correlation analysis revealed that fungal alpha diversity was more closely related to plant functional traits than soil properties. Furthermore, fungal community structure was best explained by spatial factors and plant attributes (including plant diversity and plant functional traits). Together, our findings provide new insights into the significance of spatial factors and plant attributes for predicting distributions of fungal communities in arid inland river basins, which will help us better understand the functions and services of these ecosystems.

Conservation of urban greens is an essential action for city residents, however, declining symptoms and/or traces in the annual ring of trees grown are found in parks and forest stands in a city as well as its suburb with a high level of ozone (O3). Urban greens, including roof-green, provide comfortable conditions for the people and a moderate environment in a city. They are exposed to severe environments; heat, drought, air-pollutions, etc. even with intensive management of the people. How can we proceed with the conservation and wise use of urban greens? We should know the ecophysiological responses of urban trees to such a global environment as well as a local one. Defensive capacities of urban greens should be analyzed in terms of damages caused by biotic and abiotic stresses, and it is important to understand their interactions from the viewpoint of plant-insect/disease. There is a concern that some green areas are suffering from an outbreak of insects and diseases, reducing the vigor and health of urban greens. We discuss these based on specific examples, such as man-made forests, in cities in far east Asia for considering our approach to how to keep urban green resources.

International audience; The climate impact of water-table drawdown in peatlands is unclear as carbon dioxide emissions increase and methane emissions decrease due to drying. This study shows decreasing water-table depth results in net greenhouse gas emissions from global peatlands, despite reducing methane emissions.Water-table drawdown across peatlands increases carbon dioxide (CO2) and reduces methane (CH4) emissions. The net climatic effect remains unclear. Based on global observations from 130 sites, we found a positive (warming) net climate effect of water-table drawdown. Using a machine-learning-based upscaling approach, we predict that peatland water-table drawdown driven by climate drying and human activities will increase CO2 emissions by 1.13 (95% interval: 0.88-1.50) Gt yr(-1) and reduce CH4 by 0.26 (0.14-0.52) GtCO(2)-eq yr(-1), resulting in a net increase of greenhouse gas of 0.86 (0.36-1.36) GtCO(2)-eq yr(-1) by the end of the twenty-first century under the RCP8.5 climate scenario. This drops to 0.73 (0.2-1.2) GtCO(2)-eq yr(-1) under RCP2.6. Our results point to an urgent need to preserve pristine and rehabilitate drained peatlands to decelerate the positive feedback among water-table drawdown, increased greenhouse gas emissions and climate warming.

Tropospheric ozone (O3) affects isoprenoid emissions, and floral emissions in particular, which may result in potential impacts on the interactions of plants with other organisms. The effects of ozone (O3) on isoprenoid emissions have been investigated for many years, while knowledge on O3 effects on floral emissions is still scarce and the relevant mechanism has not been clarified so far. We investigated the effects of O3 on floral and foliar isoprenoid emissions (mainly isoprene, monoterpenes and sesquiterpenes) and their synthase substrates from three rose varieties (CH, Rosa chinensis Jacq. var. chinensis; SA, R. hybrida 'Saiun'; MO, R. hybrida 'Monica Bellucci') at different exposure durations. Results indicated that the O3-induced stimulation after short-term exposure (35 days after the beginning of O3 exposure) was significant only for sesquiterpene emissions from flowers, while long-term O3 exposure (90 days after the beginning of O3 exposure) significantly decreased both foliar and floral monoterpene and sesquiterpene emissions. In addition, the observed decline of emissions under long-term O3 exposure resulted from the limitation of synthase substrates, and the responses of emissions and substrates varied among varieties, with the greatest variation in the O3-sensitive variety. These findings provide important insights on plant isoprenoid emissions and species selection for landscaping, especially in areas with high O3 concentration.

Membrane fouling has become the one of main obstacles for the widespread application of membrane technology in water treatment processes. Coagulation as pretreatment is proven to be effective for the alleviation of membrane fouling. In this study, the influence of humic acid (HA)/sodium alginate (SA) fractions in the structure and resistance of cake layer on the membrane surface was investigated. The presence of SA at an appropriate fraction could facilitate the formation of large and loosely branched flocs and thereby form a more permeable cake layer on the membrane surface due to good bridging and charge neutralization abilities of SA molecules. The particle image velocimetry (PIV) technique was employed for monitoring the dynamic formation process of cake layer under different HA/SA fractions. The cake layer with a higher thickness was observed to be rapidly formed on the membrane surface at the presence of SA in water. According to the theoretical analysis, the membrane fouling in coagulation-ultrafiltration (UF) combined system demonstrated to be highly dependent on the size and intra-porosity of flocs. The fractal dimension of flocs might have an impact on the resistance of cake layer through affecting the porosity of aggregated flocs. The SA molecules could be used as the coagulant aid for effective alleviation of membrane fouling and the improvement of filtration performance in a coagulation-UF combined system.

The impacts of ozone (O3) on crops have been extensively studied and are well understood. However, little information is available on the response of crops (especially maize) to the interactive effects of O3 and nitrogen (N) fertilizer. To this end, a maize cultivar (Zheng dan 958, ZD958) that is common in China was exposed to two O3 treatments and four N levels. We found that (1) the interactions between O3 and N were non-significant for grain yield, plant biomass, C and N, although N addition significantly increased all parameters except C concentrations in grain and plant; (2) compared to NF (non-filtered ambient air O3 concentration), NF60 (NF plus an extra 60 ppb O3) increased the optimum N application rates (Nopt) in grain yield and plant biomass, but not grain yield and plant biomass potentials, thus resulting in lower N use efficiencies (NUE) and a larger risk of N-related environmental pollution (e.g., increased N2O emission) under Nopt in NF60; (3) because of higher optimum plant N uptake (PNopt) in NF60, relative to NF, plant N-saturated conditions for grain yield potential can be gradually turned into N-limited conditions as O3 pollution increases. These findings manifest that O3 is a vital global change factor impacting the management of N fertilization. If current O3 pollution is substantially reduced, maize yield and biomass potentials can be increased under reductions in N input and N-related environmental pollution. In addition, these results can also contribute in developing and verifying Nopt model considering O3 pollution in the future.

Ground-level ozone (O3) increases in the northeastern part of Eurasia, where larch species are dominant trees and have been planted intensively. The Japanese larch (Larix kaempferi; hereafter larch) is classified as the tree species most of its sensitive to O3 based on data from long-shoot needles of seedlings. This criterion should be reconsidered based on O3 uptake, which is strongly depended on stomatal conductance (Gs) of adult trees through the difference in relevant needle traits. Because Gs is closely correlated with photosynthetic activity, we measured the in situ seasonal and yearly change in photosynthetic function, needle mass per area (LMA) and nitrogen (N) content of both short- and long-shoot needles of the canopy of larch trees over successive 3 years. No difference was observed in the in light saturated photosynthetic rate at ambient CO2 (Psat) between needles of hetero types of shoot in the latter part of the growing season, but clear differences were found within a specific year, indicating that seasonal changes in climatic factors determine Psat in the long term. The Psat-N relations differed significantly between the needle types. However, Psat at saturated CO2 (Pmax)-N was quite similar, implying that the CO2 diffusion difference between short- and long-shoots is responsible for the differing Psat -N. In conclusion, seasonal and yearly variations in photosynthetic capacity are mainly determined mainly by climatic variations, whereas shoot type determined the traits of photosynthetic N utilization as well as Gs regulation.

With the rapid industrial development and modern agricultural practices, increasing nitrogen (N) deposition can cause nutrient imbalance in immature volcanic ash soil commonly found in Japan. Larch species, widely distributed in northeast Eurasia, are associated with ectomycorrhizal (ECM) fungi which play a critical role in nutrient acquisition for their hosts. In this study, we investigated species richness and diversity of ECM fungi associated with a hybrid larch (F1) and its parents, Dahurian larch (Larix gmelinii var. japonica) and Japanese larch (L. kaempferi), under simulated N deposition (0 and 100 kg ha-1yr-1) with/without phosphorous (P) (0 and 50 kg ha-1yr-1). Seedlings planted in immature volcanic ash with low nutrient availability were subjected to the N and P treatments for fifteen months. We found that response of ECM community structure to the increased nutrient availability depended on host genotypes. Nutrient addition significantly affected ECM structure in Japanese larch, but no such significant effect was found for Dahurian larch. Effects of the nutrient addition to ECM fungal community in F1 was intermediate. F1 was tolerant to high N loading, which was due to consistent, relatively high association with Suillus sp. and Hebeloma sp. F1 showed heterosis in relative biomass, which was most apparent under high N treatments. This co-variation of ECM fungal community structure and F1 biomass in response to N loading suggest that ECM community structure might play an important role in host growth. The present findings indicate effects of N deposition on ECM fungal community structure can depend on larch species, thus it is challenging to predict general trends.

Soil microbes contribute significantly to soil respiration (SR) in boreal forests; however, there is limited knowledge on microbial contributions from long field investigations. The objective of this study was to estimate soil microbial respiration, as well as its primary controlling factors, for a period of three consecutive years. A trenching method was used to distinguish soil microbial respiration (R Mic) in a 55-year-old mature Japanese larch (Larix kaempferi) plantation in Northern Japan; the soil in which developed originally from volcanic soils containing pumice. We used a portable CO2 detection system to measure the soil respiration rate during the growing season. Environmental factors, soil physiochemical characteristics, and soil microbial biomass carbon and nitrogen (MBC and MBN) were analyzed to explain the seasonal variations of SR and R Mic. The results showed that the estimated contribution of soil microbes to SR was 78, 62, and 55% during the three successive years, respectively. Respiration attributable to decomposition of aboveground litter contributed approximately 19% to SR. The major environmental factor that affected R Mic was soil temperature at 5 cm depth, which accounted for more than 70% of the seasonal variation in R Mic observed. There were close relations among MBC, MBN, and soil water content, but the soil water content showed no significant relation with R Mic. The R Mic to SR varied from 78 to 55% following 3 years of trenching treatments. Our results demonstrated the important role of soil microbes on soil respiration in this larch forest. Soil temperature was the major positive factor that influenced R Mic, while soil water content had no significant effect. Global warming will increase the loss of C into the atmosphere by increasing the R Mic, and could accelerate climate change.

To elucidate changes in the defensive traits of tree seedlings under global environmental changes, we evaluated foliar defensive traits of the seedlings of successional trees, such as beech, oak, and magnolia grown in a natural-light phytotron. Potted seedlings were grown under the combination of two CO2 concentrations (360 vs. 720 ppm) and two nitrogen (N) treatments (4 vs. 15 kg N ha−1 yr−1) for two growing seasons using quantitative chemical analyses and anatomical method. We hypothesized that the effects of CO2 and N depend on the successional type, with late successional species providing greater defense of their leaves against herbivores, as this species exhibits determinate growth. Beech, a late successional species, responded the most to both elevated CO2 concentration (eCO2) and high N treatment. eCO2 and low N supply enhanced the defensive traits, such as the high leaf mass per area (LMA), high carbon to N ratio (C/N ratio), and increase in the concentrations of total phenolic and condensed tannin in agreement with the carbon–nutrient balance (CNB) hypothesis. High N supply decreased the C/N ratio due to the high N uptake in beech leaves. Oak, a mid–late successional species, exhibited different responses from beech: eCO2 enhanced the LMA, C/N ratio, and concentration of total phenolics of oak leaves, but only condensed tannin increased under high N supply. Magnolia did not respond to all treatments. No interactive effects were observed between CO2 and N supply in all species, except for the concentration of total phenolics in oak. Although the amounts of phenolic compounds in beech and oak varied under eCO2 and high N treatments, the distribution of these compounds did not change. Our results indicate that the changes in the defensive traits of forest tree species under eCO2 with N loading are related to the successional type.

Water sources from the lower reaches of the Heihe River northwest China, located in an arid area impacted by environmental stresses, have promoted changes to the local soil and plant conditions; however, our understanding of variations and drivers of soil bacterial communities in an arid inland river basin remains unclear. Therefore, we collected 39 soil samples from a riparian oasis zone (ROZ) to the circumjacent desert zone (CDZ) at the lower reaches of Heihe River to evaluate bacterial communities based on the 16S rRNA gene data. We found that the bacterial community composition differed between ROZ and CDZ habitats, with significantly higher relative abundance of the phyla Gemmatimonadetes and Acidobacteria in ROZ, whereas the abundance of the phyla Actinobacteria and Deinococcus–Thermus was greater in CDZ. The difference in the bacterial community was almost entirely generated by the species turnover rather than the nestedness among all samples. In addition, we found that bacterial α-diversity index showed no significant difference between ROZ and CDZ habitats. The distance-decay analysis showed that spatial distance, plant community, soil property, and plant functional trait were correlated with bacterial community variations. However, the variation partition analysis (VPA) revealed that both soil properties and plant community strongly explained the difference [such as soil water content (WC), soil silt content, and plant community structure] compared with plant functional traits in bacterial β-diversity and species turnover. Based on a co-occurrence network analysis, we found that the bacterial network of ROZ, which had more negative correlations, higher average connectivity, shorter average path length, and smaller modularity, was more complex than the network of CDZ. This suggested that the bacterial community was more stable and less vulnerable to change in the ROZ habitat than in the CDZ habitat. Overall, our findings suggest that the heterogeneity of soil properties and plant community collectively affect the structure of the soil bacterial community in an arid inland river basin. However, the influence of plant functional traits on the variation of the bacterial community depends on soil properties and plant community.

Urbanization accelerates pollution and habitat fragmentation, and the mechanism that shapes the arbuscular mycorrhizal (AM) fungal community in urban ecosystem still remains poorly understood. In this study, soil samples from 23 sites (from rural to urban), belonging to 4 green space types (country park, Co; urban park, Pa; roadside green space1, RoP1; and roadside green space2, RoP2), were collected to assess the effects of the urbanization on the AM fungal diversity. Using 454 pyrosequencing, a total of 79 AM fungal OTUs were uncovered. We found that urbanization showed a neutral effect on Shannon diversity, Simpson diversity, Pielou diversity, and community composition of the AM fungi. Within urban areas, the composition of AM fungal community was significantly different between RoP1 and RoP2. The db-RDA analysis of RoP1 and RoP2 revealed that the soil Cd accounted for the largest community composition variation, with an explanation rate of 20.5%, followed by the SOC (15.1%). Across 23 sites, Cd may have an obvious ecological toxicity on AM fungi, with significantly negative correlations between the soil Cd content and the AM fungal species richness and evenness. The AM fungal community also indicated significantly Mantel correlation with the soil Cd contents. Additionally, high herbaceous richness promoted rich AM fungi. The herbaceous composition, not the richness, has a significant impact on the AM fungal community composition. This study suggests that the toxicity of Cd from traffic should receive more attention during urban green space construction and management, and reasonable plant configuration contributed to the maintenance of the AM fungal community.

The growth of Japanese larch seedlings is regulated by the presence of nutrients as well as ectomycorrhizal symbiosis. The mountain slope of an active volcano is a severe environment for the regeneration of larch (Larix kaempferi Sarg. hereafter larch) seedlings. To determine parameters affecting the growth of larch seedlings, we analyzed stoichiometry of elements in the soils and plant organs, ectomycorrhizal (ECM) colonization, and photosynthetic abilities. These parameters were compared with two different elevations. From nutrient analysis of plant organs from larch seedlings grown on the slope of a volcano, potassium (K) was insufficient compared with the seedlings grown in other habitats. Symbiosis with ECM fungi enabled the uptake of nutrients, especially phosphorous (P) and nitrogen (N). The main factor affecting the differences in relative height growth rate (RHGr) of larch was attributed to ECM colonization. There was a positive relationship between ECM colonization and concentrations of P or N in needles. Larch seedlings with high rates of ECM colonization showed high concentrations of P and N, and had high photosynthetic rates. At lower elevation sites, concentrations of N and K in needles were low with high density of individuals. Moreover, larch showed a high accumulation of aluminum (Al) and iron (Fe) even though the amount of these elements in the soil was small. These seedlings exhibited a suppressed photosynthetic rate and RHGr. Symbiosis with ECM fungi could suppress the excessive uptake of Al and Fe.

We studied the colonization of ectomycorrhizal fungi and species abundance of a hybrid larch (F1) under elevated CO2 and O3. Two-year-old seedlings were planted in an Open-Top-Chamber system with treatments: Control (O3

The patchy distribution of vegetation in dry land results in well-documented “fertile islands”. However, the response of shrub fertile islands to plant recovery and the underlying mechanisms, such as the linkage plant and soil properties, remain unknown. We sampled soils from areas with three different plant coverages (25%, 45%, and 75%) and three of their adjacent inter-plants to investigate soil physicochemical and microbial properties in the upper Minjiang River arid valley. The results showed that these factors were influenced by the persistence of plants that contrasted with the inter-plant interspaces. We found fertile islands in under-plant soil that were enhanced with increasing plant coverage, from 25% to 45% and 75%; however, there were no significant differences between 45% and 75% plant coverage apart from the soil clay content and the fungi to bacteria ratio. The soil microbial communities in under-plant soil were strongly influenced by the total soil carbon (TC), soil organic carbon (SOC), and available nitrogen (AN), whereas the microbial communities in inter-plant soil were primarily constrained by the AN and available phosphorous (AP). Moreover, the inter-plant soil properties, including gravimetric soil water content, pH, electrical conductivity (EC), and soil C:N ratio, were also strongly influenced by adjacent vegetation, which suggested that fertile islands may be beneficial for plant recovery in this region.

Effective conservation of mangroves requires a complete understanding of vegetation structure and identification of the variables most important to their assembly. Using canonical correspondence analysis (CCA) combined with variation partition, we determined the independent and joint effects of sediment variables, including physicochemical characteristics and heavy metals, on mangrove community assemblies in the overstory and understory in Leizhou Peninsula, China. The results indicated that the contributions of sediment physicochemical variables to community assembly were greater than were those of heavy metals, particularly in overstory vegetation. However, the independent contributions of heavy metals were higher in understory mangrove vegetation than in the overstory. The TOC, TP, and salinity of the sediment, distance from the coastline, and concentration of As were limiting factors for mangrove assembly in overstory vegetation, while understory vegetation may be affected to a greater degree by the distance from the coastline, electrical conductivity, and concentration of As and Pb in the sediment.

Plant establishment is widely recognized as an effective way to prevent soil erosion in arid and semiarid ecosystems. Artemisia gmelinii, a pioneering species in many degraded ecosystems in China, is effective in improving soil properties and controlling runoff and soil loss, but mechanisms underlying soil improvement are not well understood. We therefore investigated how the presence and cover of A. gmelinii affect soil physico-chemical properties and soil microbial communities in differently sized soil aggregates in the rhizosphere and inter-plant soil in the Upper Minjiang River arid valley of China. We found that A. gmelinii presence significantly improved soil quality in terms of soil structure, water content, aggregate-associated carbon and nutrients, and soil microbial biomass and activities. Interestingly, also inter-plant soils were strongly influenced by adjacent-plant-cover, showing enhanced soil organic carbon, total carbon, nitrogen and phosphorus, and reduced soil bulk density and pH with increasing A. gmelinii cover in plots. In turn, the A. gmelinii-induced changes in inter-plant soil properties could explain a large part of the observed variation in microbial biomass, carbon and nitrogen. Importantly, effects of the presence and cover of A. gmelinii on soil properties were mostly specific for particular aggregate size classes. Specifically, A. gmelinii significantly increased P accumulation only in small macroaggregates (250–2000 μm) illustrating the importance of this aggregate class in terms of plant-mediated phosphorus accumulation, critical for P uptake in this P limited area. Our results thus indicate that A. gmelinii not only improves soil physical and microbial conditions in its rhizosphere but also in inter-plant soil, and that increasing A. gmelinii cover has the potential to reduce runoff and soil loss and to promote revegetation.

The scarcity of research on the interactive effects of multi-limiting resources has hampered the success in ecological restoration. The effects of water (W), nitrogen (N) and phosphorous (P) on the performance of a perennial shrub, Bauhinia faberi seedlings were studied through a full factorial experimental design. Eighteen treatments was involved including three water (W1:10, W2: 20 and W3: 40% field capacity), two N (N1: 100 and N2: 280 mg N kg(-1) soil) and three P (P1:12, P2: 24 and P3: 48 mg P kg(-1) soil) for 19 weeks in a greenhouse experiment. P strongly regulated the biomass allocation under severe drought stress. Elevated W and P with N1 or N2 level increased root surface area and length, root and shoot mass, water-use efficiency and tissue P concentration, but did not significantly decrease tissue N concentration. The interaction of N and P was significant. Compared to N1, N2 significantly decreased growth parameters at P1 and P2, slightly reduced them at P3, suggesting that P3 alleviated the negative effects of N2. Therefore, the interactive effects of soil N and P should be examined thoroughly in seedlings plantation sites in arid regions to avoid excess level of nitrogen. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.

We investigated the effect of ectomycorrhizal colonization, charcoal and CO2 levels on the germination of seeds of Larix kaempferi and Pinus densiflora, and also their subsequent physiological activity and growth. The seeds were sown in brown forest soil or brown forest soil mixed with charcoal, at ambient CO2 (360 μmol mol−1) or elevated CO2 (720 μmol mol−1), with or without ectomycorrhiza. The proportions of both conifer seeds that germinated in forest soil mixed with charcoal were significantly greater than for seeds sown in forest soil grown at each CO2 level (P

Forest fires frequently occur in boreal forests, and their effects on forest ecosystems are often significant in terms of carbon flux related to climate changes. Soil respiration is the second largest carbon flux in boreal forests and the change in soil respiration is not negligible. Environmental factors controlling the soil respiration, for example, soil temperature, are altered by such fires. The abnormal increase in soil temperature has an important negative effect on soil microbes by reducing their activities or even by killing them directly with strong heat. On the other hand, although vegetation is directly disturbed by fires, the indirect changes in soil respiration are followed by changes in root activities and soil microbes. However, there is very limited information on soil respiration in the forests of Northeast China. This review, by combining what is known about fire influence on soil respiration in boreal forests from previous studies of post-fire effects on soil conditions, soil microbes, and forest regeneration, presents possible scenarios of the impact of anticipated post-fire changes in forest soil respiration in Northeast China.

Road dust is one of the most common pollutants and causes a series of negative effects on plant physiology. Dust's impacts on plants can be regarded as a combination of load, composition and grain size impacts on plants; however, there is a lack of integrated dust effect studies involving these three aspects. In our study, Sophora japonica seedlings were artificially dusted with road dust collected from the road surface of Beijing so that we could study the impacts of this dust on nitrogen/carbon allocation, biomass allocation and photosynthetic pigments from the three aspects of composition, load and grain size. The results showed that the growth characteristics of S. japonica seedlings were mostly influenced by dust composition and load. Leaf N, root–shoot ratio and chlorophyll a/b were significantly affected by dust composition and load; leaf C/N, shoot biomass, total chlorophyll and carotenoid were significantly affected by dust load; stem N and stem C/N were significantly affected by dust composition; while the dust grain size alone did not affect any of the growth characteristics. Road dust did influence the growth characteristics more extensively than loam. Therefore, a higher dust load could increase the differences between road dust and loam treatments. The elements in dust are well correlated to the shoot N, shoot C/N, and root–shoot ratio of S. japonica seedlings. This knowledge could benefit the management of urban green spaces.

Sediments in eight types of mangroves were sampled in the Leizhou Peninsula. Heavy metals were analyzed to investigate the effects on metal distribution of mangrove communities, to evaluate contamination levels, identify sources and relationships between the two. Results showed that mangrove communities have effects on most heavy metal distributions in sediments, especially in the sediment with shrub communities of Aegiceras corniculatum where the contents of many metals are highest. As, Cr and Ni were identified as metal pollutants of primary concern, while Cd was of no concern. Zn, Pb, As mainly originated from anthropogenic source while the other metals are geogenic. Heavy metal distributions were affected by the independent and joint effects of landscape and sediment context; landscape context explains more variations in heavy metals than does sediment physicochemical variables. Total sulfur, total phosphorus and total potassium in sediment, and the existence of paddy field and forest land within 2000m around the sampling sites are significant variables also.

Harvesting of trees or the loss of trees due to strong winds may lead to large variations at the ground surface that, in turn, causes spatial and temporal variability of soil respiration. We performed thinning (partial harvest) on a mature larch plantation (ca. 50 yr‐old) in Tomakomai National Forest (Japan) with the purpose of studying the effects of thinning on soil respiration (Rs). We conducted field measurements to determine how soil temperature (Ts), mineral soil water content (MSWC), litter water content (LWC), fine root density, litter density, and carbon to nitrogen ratio (C/N) individually influence soil respiration. Soil respiration values did not differ significantly at the disturbed site. Soil temperature was significantly greater at the disturbed site than at the control site (t‐test= ‐12.7, P