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Soil ectomycorrhizal and saprotrophic fungi play pivotal roles in plant performance and ecosystem functioning. However, the effects of forest secondary succession on their abundance, diversity, and community structure remain unclear. We examined ectomycorrhizal and saprotrophic communities (Illumina Sequencing and FUNGuild database) in five forest secondary successional stages (20-, 32-, 47-, 61-, and > 200-year-old stands). Our results showed that ectomycorrhizal and saprotrophic communities varied with successional stages. The relative abundance of ectomycorrhizal fungi decreased from early to late stages but the relative abundance of saprotrophic fungi increased. In contrast to the abundance, diversity of ectomycorrhizal fungal communities increased with the succession, while saprotrophic fungal diversity dropped in the early successional stages and recovered later stages. Furthermore, there were significant differences in the community structure of ectomycorrhizal and saprotrophic fungi among different successional stages, and the main driving factor (tree productivity) of the shifts in two community structures was similar. Interestingly, there was a significant negative correlation between the variations in relative abundance and community structure of ectomycorrhizal and saprotrophic fungi along the secondary succession, which implied the interactions between ectomycorrhizal and saprotrophic fungi during the successional process. These results indicated that the secondary succession might not only increase decompositions of organic matter by increasing saprotrophic fungal abundance, but also stimulate the return of saprotrophic fungal diversity, which may be beneficial to plant function and ecosystem stability. [ABSTRACT FROM AUTHOR]

Background: Given the ubiquitous nature of mycorrhizal symbioses, different symbiotic fungi have obvious differences in structure and function, which may affect associated tree aboveground and belowground C allocation dynamics. However, the mechanisms underlying tree aboveground and belowground C allocation and its response to symbiotic mycorrhizal types and other factors (e.g., resource availability) remain poorly understood. Results: We used forest inventory data to explore the potential mechanism of tree aboveground and belowground C allocation patterns in Northeast China. Our results showed that tree-fungal symbioses were related to the patterns of tree C allocation. The ratio of aboveground to belowground C pool was significantly higher in ectomycorrhizal (EM)-associated trees than that in arbuscular mycorrhizal (AM)-associated trees. Symbiotic mycorrhizal types were associated with the responses of tree aboveground and belowground C allocation to different factors, such as mean annual precipitation (MAP) and mean annual temperature (MAT). Almost all factors significantly increased aboveground C allocation in AM-associated trees but significantly decreased it in EM-associated trees. Moreover, after controlling the other factors, the effects of climate factors (MAT and MAP) on the C allocation of AM- and EM-associated trees were similar. Increases in MAT and MAP significantly increased belowground and aboveground C allocation, respectively. Conclusions: Our results demonstrate symbiotic mycorrhizal types play an important role in controlling tree aboveground and belowground C allocation and dynamics. [ABSTRACT FROM AUTHOR]

Elevated nitrogen (N) deposition is changing soil communities around the world and will have unknown consequences for terrestrial ecosystem functions. In this study, we investigated a field experiment that lasted for 13 years to explore the effect of simulated N deposition and seasonal variations on the soil faunal community structure in a temperate natural secondary forest. The experimental design included a control group (0 kg N ha−1 yr−1, CK), low N addition (25 kg N ha−1 yr−1, LN), and high N addition (50 kg N ha−1 yr−1, HN). The results showed that long-term high N addition reduced the soil pH, C/N ratio, and microbial biomass carbon (MBC) and increased the total phosphorus. The soil faunal community structure after high N addition was significantly different from those after the CK and low N addition treatments. The overall trend was that abundance and richness increased under low N addition and decreased under high N addition. Further analysis showed that the abundance of omnivores and detritivores was lowest after high N addition, significantly less than the CK and low N addition. The interaction of N addition and seasonal dynamics had a significant impact on herbivores. We found that these changes were driven by differences in ecological strategies such as food and environmental preferences. Furthermore, temperature, moisture, nutrients, and pH in the soil environment were the key factors driving ecological strategies and environmental factors. Seasonal variations significantly affected the soil faunal community structure, showing the highest abundance, richness, diversity, and functional group abundance and richness of the soil faunal community in September. Nitrogen addition and seasonal dynamics significantly affected the abundance and richness of soil fauna by changing soil nutrient concentrations, MBC, and plant diversity. Our study showed that long-term high N addition reduced the abundance and functional group abundance of the soil fauna in natural secondary forests, while low N addition had a positive effect on soil faunal community structure. Collectively, the results suggest that the seasonal balance of soil fauna is affected after long-term N addition, which increases the seasonal sensitivity of soil fauna. [ABSTRACT FROM AUTHOR]

Fine roots (< 2 mm in diameter) are the main organ for obtaining resources from the belowground part of forest and also act as a hub linking the ecological processes of plant and soil. However, in the context of global climate change, it remains unclear how fine root dynamics and morphology in temperate forests respond to increased nitrogen deposition and reduced precipitation in growing season on a year-round time scale. In this study, the minirhizotrons were used to observe the response of fine root dynamics (production, mortality, turnover and life span) and morphology (diameter, single root surface area, single root length) to long-term nitrogen addition (N, 50 kg N ha−1 yr−1), precipitation reduction (W, −200 mm yr−1) and their interactive treatments (NW) in a broad-leaved Korean pine forest in Changbai Mountains over a two-year period. The results showed that N significantly increased the average diameter of fine roots. Compared to the control treatment, all treatments significantly reduced the average monthly number and surface area of live root. However, the morphological traits of the individual root in each treatment differed between the growing and non-growing seasons. All three treatments (N, W, NW) reduced annual production of fine root over the two observation periods, while the effect on annual mortality varied between years. N, W and the interaction of NW did not significantly change the annual turnover of fine root in the first observation period but increased significantly in the second. The median life span of fine root born in both non-growing seasons was significantly lower than that of fine root born in the growing season. Our results show that changes in the growth strategy of fine root depend on the complex interrelationship between their own morphology, soil layer and seasonal climatic conditions. [ABSTRACT FROM AUTHOR]

Background: Natural abundance of carbon (C) and nitrogen (N) stable isotope ratios (δ13C and δ15N) has been used to indicate the state and cycle of ecosystem C and N. However, it is still unclear how C and N cycle of boreal forests respond to the N deposition. Results: We conducted an 8-year continuous N addition field experiment in a Larix gmelinii forest in Greater Khingan Mountains, Northeast China. Four N treatments (0, 25, 50, 75 kg N ha−1 year−1) were built. The effects of N addition on the δ13C and δ15N of needle, branch, bark, and fine root of Larix gmelinii and soil were studied. The result of the balance between the N input and output flux showed that N addition significantly increased the δ15N in each organ of Larix gmelinii, but did not change the δ15N of soil. We also found that the N absorption by needles of Larix gmelinii could increase the needle photosynthesis rate and δ13C by increasing carboxylation, but N addition had no significant effect on the δ13C of soil and other organs. In addition, both the soil δ15N and δ13C increased with the soil depth. Conclusions: Long-term N addition may lead to more open C and N cycles and further affect plant nutrient acquisition strategies in boreal forest ecosystems. [ABSTRACT FROM AUTHOR]

The continuous increase in global atmospheric nitrogen deposition may change the stoichiometric balance of temperate forest plants and affect the nutrient absorption of plants and the carbon and nitrogen cycle of forests. Leaf, fine root and other ephemeral tissues are very sensitive to nutrient changes. However, it has been not clear whether nitrogen addition will affect the nutrient uptake strategies of plant leaves and fine roots. In order to explore the effects of long-term nitrogen addition on nutrient absorption and distribution of main dominant tree species in temperate secondary forests and to cope with the sustainable development of forests under the background of increasing atmospheric nitrogen deposition in the future, we conducted a 12-year continuous nitrogen addition experiment in the natural secondary forest in Changbai Mountains of Northeast China. Responses of fine root morphology, leaf nutrient resorption, fine root exudates and stoichiometry of Populus davidiana and Betula platyphylla to nitrogen addition were studied. Our study found that (1) nitrogen addition could lead to phosphorus limitation, and high nitrogen addition treatment significantly reduced the nitrogen resorption efficiency of B. platyphylla and P. davidiana and then increased the phosphorus resorption efficiency. (2) Nitrogen addition promoted the metabolism and activity of B. platyphylla fine root, which was more inclined to transport and store, while P. davidiana fine root was more inclined to capture and absorb nutrients. (3) Nitrogen addition increased the secretion rate of fine root exudates carbon and decreased that of fine root exudates nitrogen. The release of root exudates from roots to soil may stimulate soil microbial activity and nutrient availability. These different results indicate that both P. davidiana and B. platyphylla are attempting to improve resource acquisition under nitrogen deposition change, which will effectively change the soil carbon and nitrogen cycle of temperate forests. [ABSTRACT FROM AUTHOR]

Changes in precipitation frequency and intensity are predicted to be more intense and frequent accompanying climate change and may have immediate or potentially prolonged effects on soil CO2 and CH4 fluxes. However, how soil CO2 and CH4 fluxes respond to change in precipitation patterns remains poorly understood, especially under nitrogen (N) addition. In this study, we investigated the fluxes of soil CO2 and CH4 during a two-year field experiment and the effects of long-time precipitation reduction (− 30% of through-fall), short-term precipitation pulse and change of snow thickness on their response to simulated N deposition (50 kg N hm−2 y−1). Soil CO2 flux was greater enhanced by N addition in the relatively wet growing season (2016) than in the relatively dry growing season (2017), whereas soil CH4 flux was more inhibited by N addition in the relatively wet growing season 2016 than in the relatively dry growing season 2017. However, reduced precipitation decreased the positive effect of N addition on soil CO2 flux in the relatively wet growing season 2016, while changing the direction of N addition effect in the relatively dry growing season 2017. These results suggested that the precipitation patterns in the growing season may affect soil CO2 and CH4 fluxes response to N addition. Furthermore, we found that short-term extreme precipitation and thickness of snow cover had a significantly positive effect on soil CH4 flux but had a significantly negative effect on soil CO2 flux. The extreme precipitation, that is, very heavy precipitation, reduced the response magnitudes of soil CO2 and CH4 fluxes to reduced precipitation within 3 days, compared to wet precipitation and heavy precipitation. Our results indicated the significant effects of precipitation pattern changes on responses of soil C flux to N deposition, which should be incorporated into the global-C-cycling models to improve the prediction and reduce the uncertainty of C-climate feedbacks. [ABSTRACT FROM AUTHOR]

In recent decades, global warming and nitrogen (N) deposition have been increasing obviously, which have led to some strong responses in terrestrial ecosystems, especially the carbon (C) cycle. The boreal forest occupies an important position in the global C cycle with its huge C storage. However, the impact of global change such as N deposition on boreal forest ecosystem C cycle has been not very clear. In order to solve this problem, the field experiment of N addition in a boreal forest has been built in the Greater Khingan Mountains of Northeast China since 2011. Four N addition gradients (0, 25, 50, 75 kg N ha−1 year−1) were set up to study the response of above- and belowground C pool to N addition. The results showed that the total forest C sequestration of low-, medium- and high-N treatments was 104.4 ± 5.9, 20.2 ± 2.7 and 5.3 ± 0.4 g C/g N, respectively. Aboveground trees were the largest C pool, followed by soil, roots and floor C pool. Low-N increased the input of C by promoting photosynthesis. Trees of Larix gmelini increased the investment in the belowground root system and increased the belowground C pool. High-N reduced the inter-annual litter biomass and decreased litter C:N that accelerated the decomposition of litter, resulting in a reduction in the floor C pool. Low-N increased total soil respiration, while medium- and high-N inhibited heterotrophic respiration and then increased soil C sequestration. The estimation of forest C pool provides valuable data for improving the C dynamic characteristics of boreal forest ecosystem and is of great significance for us to understand the impact of climate change on the global C cycle. [ABSTRACT FROM AUTHOR]

A residential lot impacted by spills from a leaking light heating oil tank was treated with a combination of chemical oxidation and bioremediation to avoid technically challenging excavation. The tank left emptied in the ground was used for slow infiltration of the remediation additives to the low permeability, clayey soil. First, hydrogen peroxide and citrate chelate was added for Fenton's reaction–based chemical oxidation, resulting in a ca. 50% reduction from the initial 25,000 mg/kg average oil concentration in the soil below the tank. Part of this was likely achieved through mobilization of oily soil into the tank, which was beneficial in regards to the following biological treatment. By first adding live bacteria in a soil inoculum, and then oxygen and nutrients in different forms, an approximately 90% average reduction was achieved. To further enhance the effect, methyl-β-cyclodextrin surfactant (CD) was added, resulting finally in a 98% reduction from the initial average level. The applicability of the surfactant was based on laboratory-scale tests demonstrating that CD promoted oil degradation and, unlike pine soap, was not utilized by the bacteria as a carbon source, and thus inhibiting degradation of oils regardless of the positive effect on biological activity. The effect of CD on water solubility for different hydrocarbon fractions was tested to serve as the basis for risk assessment requirements for authorizing the use of the surfactant at the site. [ABSTRACT FROM AUTHOR]

FATP1 plays an important role in the trafficking of free fatty acids in adipocytes, however, its precise function and relationship with other fatty acid transporters all remain poorly understood. In this study, FATP1 gene silencing was induced by transfecting siRNA of target sequence into chicken preadipocytes, then the expression of FABP was found down-regulated while the expression of FAT was raised. In addition, differential inhibition of the cells was observed and the expressions of PPARγ and C/EBPα were found down-regulated. Moreover, the silencing also induced the down-regulation of FAS and inhibited the adipogenesis in adipocytes. Of specific interest here was that FATP1 silencing significantly improved the expressions and activities of cell apoptotic factors Caspases 3 and BCL2 associated X protein (Bax). Consequently, FATP1 deficiency prevented the differentiation while induced apoptosis in chicken preadipocytes. [ABSTRACT FROM AUTHOR]

Background: The nitrogen isotope natural abundance (δ15N) provides integrated information on ecosystem N dynamics, and carbon isotope natural abundance (δ13C) has been used to infer how water-using processes of plants change in terrestrial ecosystems. However, how δ13C and δ15N abundances in plant life and soils respond to N addition and water availability change is still unclear. Thus, δ13C and δ15N abundances in plant life and soils were used to investigate the effects of long-time (10 years) N addition (+ 50 kg N·ha− 1·yr− 1) and precipitation reduction (− 30% of throughfall) in forest C and N cycling traits in a temperate forest in northern China. Results: We analyzed the δ13C and δ15N values of dominant plant foliage, litterfall, fungal sporophores, roots, and soils in the study. The results showed that δ15N values of foliage, litterfall, and surface soil layer's (0–10 cm) total N were significantly increased by N addition, while δ15N values of fine roots and coarse roots were considerably decreased. Nitrogen addition also significantly increased the δ13C value of fine roots and total N concentration of the surface soil layer compared with the control. The C concentration, δ13C, and δ15N values of foliage and δ15N values of fine roots were significantly increased by precipitation reduction, while N concentration of foliage and litterfall significantly decreased. The combined effects of N addition and precipitation reduction significantly increased the δ13C and δ15N values of foliage as well as the δ15N values of fine roots and δ13C values of litterfall. Furthermore, foliar δ15N values were significantly correlated with foliage δ13C values, surface soil δ15N values, surface soil C concentration, and N concentrations. Nitrogen concentrations and δ13C values of foliage were significantly correlated with δ15N values and N concentrations of fine roots. Conclusions: This indicates that plants increasingly take up the heavier 15N under N addition and the heavier 13C and 15N under precipitation reduction, suggesting that N addition and precipitation reduction may lead to more open forest ecosystem C and N cycling and affect plant nutrient acquisition strategies. [ABSTRACT FROM AUTHOR]