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951.
Harry Olde Venterink Ignacy Kardel Wiktor Kotowski Wilma Peeters Martin J. Wassen 《Biogeochemistry》2009,93(3):235-252
To provide a reference for wetlands elsewhere we analysed soil nutrients and the vegetation of floodplains and fens in the
relatively undisturbed Biebrza-valley, Poland. Additionally, by studying sites along a water-table gradient, and by comparing
pairs of mown and unmown sites, we aimed with exploring long-term effects of drainage and annual hay-removal on nutrient availabilities
and vegetation response. In undrained fens and floodplains, N mineralization went slowly (0–30 kg N ha−1 year−1) but it increased strongly with decreasing water table (up to 120 kg N ha−1 year−1). Soil N, P and K pools were small in the undisturbed mires. Drainage had caused a shift from fen to meadow species and the
disappearance of bryophytes. Biomass of vascular plants increased with increasing N mineralization and soil P. Annual hay-removal
tended to have reduced N mineralization and soil K pools, but it had increased soil P. Moreover, N concentrations in vascular
plants were not affected, but P and K concentrations and therefore N:P and N:K ratios tended to be changed. Annual hay-removal
had induced a shift from P to K limitation in the severely drained fen, and from P to N limitation in the floodplain. The
low nutrient availabilities and productivity of the undisturbed Biebrza mires illustrate the vulnerability of such mires to
eutrophication in Poland and elsewhere. In nutrient-enriched areas, hay removal may prevent productivity increase of the vegetation,
but also may severely alter N:P:K stoichiometry, induce K-limitation at drained sites, and alter vegetation structure and
composition. 相似文献
952.
Free air CO2 enrichment (FACE) experiments in aggrading temperate forests and plantations have been initiated to test whether temperate
forest ecosystems act as sinks for anthropogenic emissions of CO2. These FACE experiments have demonstrated increases in net primary production and carbon (C) storage in forest vegetation
due to increased atmospheric CO2 concentrations. However, the fate of this extra biomass in the forest floor or mineral soil is less clear. After 6 years
of FACE treatment in a short-rotation poplar plantation, we observed an additional sink of 32 g C m−2 y−1 in the forest floor. Mineral soil C content increased equally under ambient and increased CO2 treatment during the 6-year experiment. However, during the first half of the experiment the increase in soil C was suppressed
under FACE due to a priming effect, that is, the additional labile C increased the mineralization of older SOM, whereas during
the second half of the experiment the increase in soil C was larger under FACE. An additional sink of 54 g C m−2 y−1 in the top 10 cm of the mineral soil was created under FACE during the second half of the experiment. Although, this FACE
effect was not significant due to a combination of soil spatial variability and the low number of replicates that are inherent
to the present generation of forest stand FACE experiments. Physical fractionation by wet sieving revealed an increase in
the C and nitrogen (N) content of macro-aggregates due to FACE. Further fractionation by density showed that FACE increased
C and N contents of the light iPOM and mineral associated intra-macro-aggregate fractions. Isolation of micro-aggregates from
macro-aggregates and subsequent fractionation by density revealed that FACE increased C and N contents of the light iPOM,
C content of the fine iPOM and C and N contents of the mineral associated intra-micro-aggregate fractions. From this we infer
that the amount of stabilized C and N increased under FACE treatment. We compared our data with published results of other
forest FACE experiments and infer that the type of vegetation and soil base saturation, as a proxy for bioturbation, are important
factors related to the size of the additional C sinks of the forest floor–soil system under FACE.
Author Contribution: MRH conceived of and designed the study, performed research, analyzed data, and wrote the paper; GES
conceived of and designed the study and performed research. 相似文献
953.
ASTLEY HASTINGS JOHN CLIFTON-BROWN† MARTIN WATTENBACH C. PAUL MITCHELL‡ PAUL STAMPFL§ PETE SMITH 《Global Change Biology Bioenergy》2009,1(2):180-196
European field experiments have demonstrated Miscanthus can produce some of the highest energy yields per hectare of all potential energy crops. Previous modelling studies using MISCANMOD have calculated the potential energy yield for the EU27 from mean historical climate data (1960–1990). In this paper, we have built on the previous studies by further developing a new Miscanthus crop growth model MISCANFOR in order to analyse (i) interannual variation in yields for past and future climates, (ii) genotype-specific parameters on yield in Europe. Under recent climatic conditions (1960–1990) we show that 10% of arable land could produce 1709 PJ and mitigate 30 Tg of carbon dioxide-carbon (CO2 -C) equivalent greenhouse gasses (GHGs) compared with EU27 primary energy consumption of 65 598 PJ, emitting 1048 Tg of CO2 -C equivalent GHGs in 2005. If we continue to use the clone Miscanthus × giganteus , MISCANFOR shows that, as climate change reduces in-season water availability, energy production and carbon mitigation could fall 80% by 2080 for the Intergovernmental Panel on Climate Change A2 scenario. However, because Miscanthus is found in a huge range of climates in Asia, we propose that new hybrids will incorporate genes conferring superior drought and frost tolerance. Using parameters from characterized germplasm, we calculate energy production could increase from present levels by 88% (to 2360 PJ) and mitigate 42 Tg of CO2 -C equivalent using 10% arable land for the 2080 mid-range A2 scenario. This is equivalent to 3.6% of 2005 EU27 primary energy consumption and 4.0% of total CO2 equivalent C GHG emissions. 相似文献
954.
Alexandre Keiji Tashima Marcel Ottens Luuk A.M. Van der Wielen Dennys E. Cintra José R. Pauli Pedro de Alcântara Pessôa Filho Everson Alves Miranda 《Biotechnology and bioengineering》2009,103(5):909-919
Recent works have pointed to the use of volatile electrolytes such as carbon dioxide (CO2) dissolved in aqueous solutions as a promising alternative to the precipitating agents conventionally used for protein recovery in the food and pharmaceutical industries. In this work we investigated experimental and theoretical aspects of the precipitation of porcine insulin, a biomolecule of pharmaceutical interest, using CO2 as an acid‐precipitating agent. The solubility of porcine insulin in NaHCO3 solutions in pressurized CO2 was determined as a function of temperature and pressure, with a minimum being observed close to the protein isoelectric point. A thermodynamic model was developed and successfully utilized to correlate the experimental data. Insulin was considered a polyelectrolyte in the model and its self‐association reactions were also taken into account. The biological activity of insulin was maintained after precipitation with CO2, although some activity can be lost if foam is formed in the depressurization step. Biotechnol. Bioeng. 2009;103: 909–919. © 2009 Wiley Periodicals, Inc. 相似文献
955.
We evaluated how three co‐occurring tree and four grassland species influence potentially harvestable biofuel stocks and above‐ and belowground carbon pools. After 5 years, the tree Pinus strobus had 6.5 times the amount of aboveground harvestable biomass as another tree Quercus ellipsoidalis and 10 times that of the grassland species. P. strobus accrued the largest total plant carbon pool (1375 g C m?2 or 394 g C m?2 yr), while Schizachyrium scoparium accrued the largest total plant carbon pool among the grassland species (421 g C m?2 or 137 g C m?2 yr). Quercus ellipsoidalis accrued 850 g C m?2, Q. macrocarpa 370 g C m?2, Poa pratensis 390 g C m?2, Solidago canadensis 132 g C m?2, and Lespedeza capitata 283 g C m?2. Only P. strobus and Q. ellipsoidalis significantly sequestered carbon during the experiment. Species differed in total ecosystem carbon accumulation from ?21.3 to +169.8 g C m?2 yr compared with the original soil carbon pool. Plant carbon gains with P. strobus were paralleled by a decrease of 16% in soil carbon and a nonsignificant decline of 9% for Q. ellipsoidalis. However, carbon allocation differed among species, with P. strobus allocating most aboveground in a disturbance prone aboveground pool, whereas Q. ellipsoidalis, allocated most carbon in less disturbance sensitive belowground biomass. These differences have strong implications for terrestrial carbon sequestration and potential biofuel production. For P. strobus, aboveground plant carbon harvest for biofuel would result in no net carbon sequestration as declines in soil carbon offset plant carbon gains. Conversely the harvest of Q. ellipsoidalis aboveground biomass would result in net sequestration of carbon belowground due to its high allocation belowground, but would yield lower amounts of aboveground biomass. Our results demonstrate that plant species can differentially impact ecosystem carbon pools and the distribution of carbon above and belowground. 相似文献
956.
S. Becquevort I. Dumont J.-L. Tison D. Lannuzel M.-L. Sauvée L. Chou V. Schoemann 《Polar Biology》2009,32(6):879-895
Pack ice, brines and seawaters were sampled in October 2003 in the East Antarctic sector to investigate the structure of the
microbial communities (algae, bacteria and protozoa) in relation to the associated physico-chemical conditions (ice structure,
temperature, salinity, inorganic nutrients, chlorophyll a and organic matter). Ice cover ranged between 0.3 and 0.8 m, composed of granular and columnar ice. The brine volume fractions
sharply increased above −4°C in the bottom ice, coinciding with an important increase of algal biomass (up to 3.9 mg C l−1), suggesting a control of the algae growth by the space availability at that period of time. Large accumulation of NH4
+ and PO4
3− was observed in the bottom ice. The high pool of organic matter, especially of transparent exopolymeric particles, likely
led to nutrients retention and limitation of the protozoa grazing pressure, inducing therefore an algal accumulation. In contrast,
the heterotrophs dominated in the underlying seawaters. 相似文献
957.
958.
Organic carbon degradation experiments were carried out using flow-through reactors with sediments collected from an intertidal freshwater marsh of an eutrophic estuary (The Scheldt, Belgium).
Concentrations of nitrate, nitrite, dissolved inorganic carbon (DIC), dissolved organic carbon, methane, dissolved cations
(Ca2+, Mg2+, Na+ and K+), total dissolved Fe, phosphate and alkalinity were measured in the outflow solutions from reactors that were supplied with
or without the terminal electron acceptor nitrate. Organic carbon mineralization rates were computed from the release rates
of DIC after correcting for the contribution of carbonate mineral dissolution. The experiments ran for several months until
nitrate reducing activity could no longer be detected. In the reactors supplied with nitrate, 10–13% of the bulk sedimentary
organic carbon (SOC) was mineralized by the end of the experiments. In reactors receiving no nitrate, only 3–9% of the initial
SOC was mineralized. Organic matter utilization by nitrate reducers could be described as the simultaneous degradation of
two carbon pools with different maximum oxidation rates and half-saturation constants. Even when nitrate was supplied in non-limiting
concentrations about half of the carbon mineralization in the reactors was due to fermentative processes, rather than being
coupled to nitrate respiration. Fermentation may thus be responsible for a large fraction of the DIC efflux from organic-rich, nearshore sediments. 相似文献
959.
Carbon Mineralization and Labile Organic Carbon Pools in the Sandy Soils of a North Florida Watershed 总被引:1,自引:0,他引:1
Mi-Youn Ahn Andrew R. Zimmerman Nick B. Comerford James O. Sickman Sabine Grunwald 《Ecosystems》2009,12(4):672-685
The large pool of actively cycling carbon (C) held in soils is susceptible to release due to changes in landuse, management,
or climate. Yet, the amount and distribution of potentially mineralizable C present in soils of various types and the method
by which this soil C fraction can best be quantified, are not well established. The distribution of total organic C (TOC),
extractable C pools (hot-water-extractable and acid-hydrolyzable), and in vitro mineralizable C in 138 surface soils across
a north Florida watershed was found to be quite heterogeneous. Thus, these C quality parameters could not statistically distinguish
the eight landuses or four major soil orders represented. Only wetland and upland forest soils, with the largest and smallest
C pool size, respectively, were consistently different from the soils of other landuse types. Variations in potential C mineralization
were best explained by TOC (62%) and hot-water-extractable C (59%), whereas acid-hydrolyzable C (32%) and clay content (35%)
were generally not adequate indicators of C bioavailability. Within certain landuse and soil orders (Alfisol, Wetland and
Rangeland, all with >3% clay content), however, C mineralization and clay content were directly linearly correlated, indicating
a possible stimulatory effect of clay on microbial processing of C. Generally, the sandy nature of these surface soils imparted
a lack of protection against C mineralization and likely resulted in the lack of landuse/soil order differences in the soil
C pools. If a single parameter is to be chosen to quantify the potential for soil C mineralization in southeastern U.S. coastal
plain soils, we recommend TOC as the most efficient soil variable to measure.
Author Contributions Conceived of or designed study: Sabine Grunwald, Nick Comerford, and James Sickman—Performed research: Mi-Youn Ahn—Analyzed
data: Mi-Youn Ahn, Andrew Zimmerman, and Nick Comerford—Contributed new methods or models: Andrew Zimmerman, Nick Comerford,
and James Sickman—Wrote the paper: Mi-Youn Ahn, Andrew Zimmerman, and Nick Comerford. 相似文献
960.
Urban areas are home to more than half of the world's people, responsible for >70% of anthropogenic release of carbon dioxide and 76% of wood used for industrial purposes. By 2050 the proportion of the urban population is expected to increase to 70% worldwide. Despite fast rates of change and potential value for mitigation of carbon dioxide emissions, the organic carbon storage in human settlements has not been well quantified. Here, we show that human settlements can store as much carbon per unit area (23–42 kg C m−2 urban areas and 7–16 kg C m−2 exurban areas) as tropical forests, which have the highest carbon density of natural ecosystems (4–25 kg C m−2 ). By the year 2000 carbon storage attributed to human settlements of the conterminous United States was 18 Pg of carbon or 10% of its total land carbon storage. Sixty-four percent of this carbon was attributed to soil, 20% to vegetation, 11% to landfills, and 5% to buildings. To offset rising urban emissions of carbon, regional and national governments should consider how to protect or even to increase carbon storage of human-dominated landscapes. Rigorous studies addressing carbon budgets of human settlements and vulnerability of their carbon storage are needed. 相似文献