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Potential environmental factors that influence the nitrogen concentration and δ15N values in the moss Hypnum cupressiforme collected inside and outside canopy drip lines
2015
Skudnik, Mitja | Jeran, Z. (Zvonka) | Batič, Franc | Simoncic, Primoz | Kastelec, Damijana
Samples of the moss Hypnum cupressiforme were collected at 103 locations in forests of Slovenia. At each location, samples were taken at two types of sites: under tree canopies and in adjacent forest openings. The results show that the moss collected in the forest openings reflects the surrounding land-use characteristics and, consequently, the main N emission sources. For moss sampled under canopies, the characteristics of the forest at the moss-sampling locations are more important than the main emission sources outside the forest. A regression model was used to provide the nitrogen (N) concentration in moss from the forest openings in relation to the N concentration in moss under canopies and other environmental variables. The spatial distribution of the locations of the N concentrations and δ15N values in moss collected in the forest openings and under the canopies in relation to main N deposition sources is discussed.
Mostrar más [+] Menos [-]Using foliar and forest floor mercury concentrations to assess spatial patterns of mercury deposition
2015
Blackwell, Bradley D. | Driscoll, Charles T.
We evaluated spatial patterns of mercury (Hg) deposition through analysis of foliage and forest floor samples from 45 sites across Adirondack Park, NY. Species-specific differences in foliar Hg were evident with the lowest concentrations found in first-year conifer needles and highest concentrations found in black cherry (Prunus serotina). For foliage and forest floor samples, latitude and longitude were negatively correlated with Hg concentrations, likely because of proximity to emission sources, while elevation was positively correlated with Hg concentrations. Elemental analysis showed moderately strong, positive correlations between Hg and nitrogen concentrations. The spatial pattern of Hg deposition across the Adirondacks is similar to patterns of other contaminants that originate largely from combustion sources such as nitrogen and sulfur. The results of this study suggest foliage can be used to assess spatial patterns of Hg deposition in small regions or areas of varied topography where current Hg deposition models are too coarse to predict deposition accurately.
Mostrar más [+] Menos [-]Elevated ozone and nitrogen deposition affect nitrogen pools of subalpine grassland
2015
Bassin, Seraina | Käch, David | Valsangiacomo, Alain | Mayer, J. (Jochen) | Oberholzer, Hans-Rudolf | Volk, Matthias | Fuhrer, Jürg
In a free-air fumigation experiment with subalpine grassland, we studied long-term effects of elevated ozone (O3) and nitrogen (N) deposition on ecosystem N pools and on the fate of anthropogenic N. At three times during the seventh year of exposure, N pools and recovery of a stable isotope tracer (15N) were determined in above- and belowground plant parts, and in the soil. Plants were much better competitors for 15N than soil microorganisms. Plant N pools increased by 30–40% after N addition, while soil pools remained unaffected, suggesting that most of the extra N was taken up and stored in plant biomass, thus preventing the ecosystem from acquiring characteristics of eutrophication. Elevated O3 caused an increase of N in microbial biomass and in stabilized soil N, probably resulting from increased litter input and lower litter quality. Different from individual effects, the interaction between the pollutants remained partly unexplained.
Mostrar más [+] Menos [-]Is guava phenolic metabolism influenced by elevated atmospheric CO2?
2015
Mendes de Rezende, Fernanda | Pereira de Souza, Amanda | Buckeridge, Marcos Silveira | Maria Furlan, Cláudia
Seedlings of Psidium guajava cv. Pedro Sato were distributed into four open-top chambers: two with ambient CO2 (∼390 ppm) and two with elevated CO2 (∼780 ppm). Monthly, five individuals of each chamber were collected, separated into root, stem and leaves and immediately frozen in liquid nitrogen. Chemical parameters were analyzed to investigate how guava invests the surplus carbon. For all classes of phenolic compounds analyzed only tannins showed significant increase in plants at elevated CO2 after 90 days. There was no significant difference in dry biomass, but the leaves showed high accumulation of starch under elevated CO2. Results suggest that elevated CO2 seems to be favorable to seedlings of P. guajava, due to accumulation of starch and tannins, the latter being an important anti-herbivore substance.
Mostrar más [+] Menos [-]Combined ecological risks of nitrogen and phosphorus in European freshwaters
2015
Azevedo, Ligia B. | van Zelm, Rosalie | Leuven, Rob S.E.W. | Hendriks, A Jan | Huijbregts, Mark A.J.
Eutrophication is a key water quality issue triggered by increasing nitrogen (N) and phosphorus (P) levels and potentially posing risks to freshwater biota. We predicted the probability that an invertebrate species within a community assemblage becomes absent due to nutrient stress as the ecological risk (ER) for European lakes and streams subjected to N and P pollution from 1985 to 2011. The ER was calculated as a function of species-specific tolerances to NO3− and total P concentrations and water quality monitoring data. Lake and stream ER averaged 50% in the last monitored year (i.e. 2011) and we observed a decrease by 22% and 38% in lake and stream ER (respectively) of river basins since 1985. Additionally, the ER from N stress surpassed that of P in both freshwater systems. The ER can be applied to identify river basins most subjected to eutrophication risks and the main drivers of impacts.
Mostrar más [+] Menos [-]Effects of nitrogen deposition on carbon cycle in terrestrial ecosystems of China: A meta-analysis
2015
Chen, Hao | Li, Dejun | Gurmesa, Geshere A. | Yu, Guirui | Li, Linghao | Zhang, Wei | Fang, Huajun | Mo, Jiangming
Nitrogen (N) deposition in China has increased greatly, but the general impact of elevated N deposition on carbon (C) dynamics in Chinese terrestrial ecosystems is not well documented. In this study we used a meta-analysis method to compile 88 studies on the effects of N deposition C cycling on Chinese terrestrial ecosystems. Our results showed that N addition did not change soil C pools but increased above-ground plant C pool. A large decrease in below-ground plant C pool was observed. Our result also showed that the impacts of N addition on ecosystem C dynamics depend on ecosystem type and rate of N addition. Overall, our findings suggest that 1) decreased below-ground plant C pool may limit long-term soil C sequestration; and 2) it is better to treat N-rich and N-limited ecosystems differently in modeling effects of N deposition on ecosystem C cycle.
Mostrar más [+] Menos [-]Atmospheric deposition of nitrogen, sulfur and base cations in jack pine stands in the Athabasca Oil Sands Region, Alberta, Canada
2015
Fenn, M.E. | Bytnerowicz, A. | Schilling, S.L. | Ross, C.S.
Atmospheric deposition in the Athabasca Oil Sands Region decreased exponentially with distance from the industrial center. Throughfall deposition (kg ha−1 yr−1) of NH4–N (.8–14.7) was double that of NO3–N (.3–6.7), while SO4–S ranged from 2.5 to 23.7. Gaseous pollutants (NO2, HNO3, NH3, SO2) are important drivers of atmospheric deposition but weak correlations between gaseous pollutants and deposition suggest that particulate deposition is also important. The deposition (eq ha−1) of base cations (Ca + Mg + Na) across the sampling network was highly similar to N + S deposition, suggesting that acidic deposition is neutralized by base cation deposition and that eutrophication impacts from excess N may be of greater concern than acidification. Emissions from a large forest fire in summer 2011 were most prominently reflected in increased concentrations of HNO3 and throughfall deposition of SO4–S at some sites. Deposition of NO3–N also increased as did NH4–N deposition to a lesser degree.
Mostrar más [+] Menos [-]Inorganic nitrogen wet deposition: Evidence from the North-South Transect of Eastern China
2015
Zhan, X. | Yu, G. | He, N. | Jia, B. | Zhou, M. | Wang, C. | Zhang, J. | Zhao, G. | Wang, S. | Liu, Y. | Yan, J.
We examined the spatio-temporal variation of dissolved inorganic nitrogen (DIN) deposition in eight typical forest ecosystems of Eastern China for three consecutive years. DIN deposition exhibited an increasing gradient from north to south, with N−NH4+ as the predominant contributor. DIN deposition in precipitation changed after interaction with the forest canopy, and serious ecological perturbations are expected in this region. DIN deposition presented seasonal fluctuations, which might be ascribed to agricultural activity, fossil-fuel combustion and environmental factors (i.e., wind direction, soil temperature). Notably, N fertilizer use (FN), energy consumption (E), and precipitation (P) jointly explained 84.3% of the spatial variation in DIN deposition, of which FN (27.2%) was the most important, followed by E (24.8%), and finally P (9.3%). The findings demonstrate that DIN deposition is regulated by precipitation mainly via anthropogenic N emissions, and this analysis provides decision-makers a novel view for N pollution abatement.
Mostrar más [+] Menos [-]CO2 dose–response functions for wheat grain, protein and mineral yield based on FACE and open-top chamber experiments
2015
Pleijel, Håkan | Högy, Petra
Data from three Swedish open-top chamber and four German FACE experiments were combined to derive response functions for elevated CO2 (eCO2) effects on Cd, Zn, Mn, protein, grain yield, grain mass and grain number of wheat. Grain yield and grain number were increased by ∼6% and ∼7%, respectively, per 100 ppm CO2; the former effect was linked to plant nitrogen status. Grain mass was not influenced by eCO2, whereas Cd concentration was reduced. Unlike Zn, Mn and protein, effects on Cd yield were not related to effects on grain yield. Yields of Mn, Zn and (weakly) protein were positively affected by eCO2. For protein, grain yield, grain mass and grain number, the results were consistent among the FACE and OTC experiments. A key conclusion was that yields of essential nutrients were enhanced (Mn > Zn > protein), although less than grain yield, which would not be expected from a simple dilution model.
Mostrar más [+] Menos [-]Contaminants of legacy and emerging concern in terrestrial passerines from a nature reserve in South China: Residue levels and inter-species differences in the accumulation
2015
Peng, Ying | Wu, Jiang-Ping | Tao, Lin | Mo, Ling | Tang, Bin | Zhang, Qiang | Luo, Xiao-Jun | Zou, Fa-Sheng | Mai, Bi-Xian
Knowledge is limited about the bioaccumulation of persistent halogenated compounds (PHCs) in terrestrial wildlife. Several PHCs, including dichlorodiphenyltrichloroethane (DDT) and its metabolites (designated as DDTs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), decabromodiphenylethane (DBDPE) and 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), and stable isotopes (δ15N and δ13C) were analyzed in the muscle of four terrestrial passerines, Parus major, Copsychus saularis, Pycnonotus sinensis and Pycnonotus jocosus, from a nature reserve in South China. P. major had the highest PHC concentrations, with median values of 1060, 401, 92, 25 and 0.3 ng/g lipid weight for DDTs, PCBs, PBDEs, DBDPE and BTBPE, respectively. Fractions of DDT in P. jocosus and PCBs 153, 118 and 180 in C. saularis were higher compared with the other species. The inter-species differences in PHC concentrations and profiles could be attributed to the differences in trophic level, diet, living habits and metabolic capacity among the birds.
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