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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.

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 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

The flow of labeled carbon in ectomycorrhizal and non-ectomycorrhizal seedlings of Japanese larch (Larix kaempferi Sarg.) and its F1 hybrid (Larix gmelinii Rupr. x L. kaempferi) was studied. Larch seedlings were grown in a greenhouse for 110 days with larch forest soil (FM) or Suillus grevillei (SM) inoculum, or in the absence of ectomycorrhizal fungi (NM). Shoots of colonized and NM seedlings were exposed to a pulse of 14CO2 for 1 h under natural light. Seedlings were harvested following 0, 6 and 24 h of exposure to 14CO2. At the final harvest, SM seedlings of Japanese larch and hybrid larch allocated 2.6 and 2.5% more 14C, respectively, to roots than NM seedlings. In contrast, FM seedlings of Japanese larch and hybrid larch allocated 6.5 and 18.0% more 14C, respectively, to the stem than NM seedlings. Of the total 14C detected in needle, stem and root fractions, FM and SM seedlings allocated a greater proportion than NM seedlings, perhaps because FM and SM seedlings had significantly (P < 0.05) higher photosynthetic rates than NM seedlings. As a result, FM and SM seedlings had greater dry masses than NM seedlings. Concentrations of nitrogen and phosphorus in FM and SM seedlings were significantly (P < 0.05) higher than in NM seedlings, as was stomatal conductance.

The seasonal changes in photosynthetic properties in 1-year-old needles of Sakhalin spruce (Picea glehnii) were measured using the chlorophyll fluorescence technique at various temperatures (5, 10, 20, 25 and 30°C). In the course of seasonal change, a temporary decrease in the quantum yield of PSII electron transport (Φ PSII ) was observed just before budbreak. A decline in photochemical quenching (qp) was observed at the same time as that of Φ PSII but only at the two lowest temperatures (5 and 10°C). Photochemical efficiency of open PSII (F v '/F m ') also declined just before budbreak at 25 and 30°C. An increase in thermal energy dissipation as indicated by a decrease in F v '/F m ' before budbreak was not significant at lower temperatures (5 and 10°C) in spite of the declines in qp. This implies that thermal energy dissipation necessitated by the decline in Φ PSII might not be sufficiently strong to prevent a decline in qp at lower temperatures. On the other hand, at higher temperatures no decline was observed in qp because Φ PSII decreased to a relatively small extent, therefore thermal energy dissipation is sufficient in coping with the excessive energy accumulation in PSIL Seedlings of Sakhalin spruce exposed to ambient air temperature below 10°C before budbreak exhibited photoinhibition indicated by a decrease in the maximal photochemical efficiency of PSII (F v /F m ) after an overnight dark adaptation. The present study suggests that 1-year-old shoots of Sakhalin spruce have an increased susceptibility to photoinhibition at low temperature just before budbreak.

The ectomycorrhizal fungi (ECM fungi) are both abundant and widespread in boreal forests. Host plant provides the assimilated carbon to the infecting ECM fungi. Many studies indicate that at most 10-30% of the assimilated carbon by the host plant photosynthesis may be used by the fungal partner for the production and sustenance of its external biomass (Smith and Read 1997). On the other hand, ECM fungi exude extracellular enzymes that are able to break down complex organic substances and consequently transmit the inorganic nutrients to their hosts. Such ECM activity results in greater plant growth under severe environmental conditions of the boreal forests (Read 1991; Chalot and Brun 1998). Tree seedlings infected with ECM can significantly improve their growth when compared with nonmycorrhizal seedlings.

The effects of different fertilization regimes on root growth characteristics, nutrient uptake and biomass production of Japanese larch (Larix kampferi Sarg.) and its hybrid larch (L. gmelinii × L. kampferi) seedlings were examined for one growing season. Seedlings were raised in the greenhouse under three fertilizer levels (10, 20, 40 mg N seedling−1 season−1) and two delivery schedules, conventional (C) and exponential (E) for 12 weeks. Root growth, biomass allocation and nutrient loading capacity of seedlings were measured for a 3-week interval. By the end of growing season, seedlings fertilized with low dose conventionally (10C) and exponentially (10E) developed relatively longer root and larger root surface areas than those fertilized at high dose exponential loading (40E). At final harvest, the 40E treated Japanese larch had 134% and 155% more shoot mass as compared with those raised under 20E and 10E treated seedlings, respectively. The seedlings fertilized under 10C and 10E showed a high root mass ratio, while 40E treated seedlings showed a low root mass ratio. These data indicated that different nutrient levels (10 mg, 20 mg and 40 mg) strongly affected root growth characteristics. The same seasonal dose (10 mg) applied exponentially (10E) accumulated more N in seedlings compared to the 10C treatment. Exponential fertilization enhanced an increase in N concentration of the whole plant suggesting exponential delivery schedule is an efficient fertilization technique for greater nutrient uptake of plants. In contrast, N concentration of whole plant was declined for seedlings treated with conventional fertilization due to growth dilution. Late in the growing season, seedlings raised under 40E did not significantly improved dry mass production of root, but nutrient accumulation increased without a concomitant increased in root dry mass production. The result suggests that seedlings fertilized exponentially at medium and high dose rates (20E and 40E) induced luxury nutrient consumption within the plant.

This study investigated the influence of broadleaf and conifer vegetation on soil microbial communities in a distinct vertical distribution belt in Northeast China. Soil samples were taken at 0-5, 5-10 and 10-20 cm depths from four vegetation types at different altitudes, which were characterized by poplar (Populus davidiana) (1250-1300 m), poplar (P. davidiana) mixed with birch (Betula platyphylla) (1370-1550 m), birch (B. platyphylla) (1550-1720 m), and larch (Larix principis-rupprechtii) (1840-1890 m). Microbial biomass and community structure were determined using the fumigation-extraction method and phospholipid fatty acid (PLFA) analysis, and soil fungal community level physiological profiles (CLPP) were characterized using Biolog FF Microplates. It was found that soil properties, especially soil organic carbon and water content, contributed significantly to the variations in soil microbes. With increasing soil depth, the soil microbial biomass, fungal biomass, and fungal catabolic ability diminished; however, the ratio of fungi to bacteria increased. The fungal ratio was higher under larch forests compared to that under poplar, birch, and their mixed forests, although the soil microbial biomass was lower. The direct contribution of vegetation types to the soil microbial community variation was 12%. If the indirect contribution through soil organic carbon was included, variations in the vegetation type had substantial influences on soil microbial composition and diversity.