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1.
Mona N. Högberg Róbert Blaško Lisbet Holm Bach Niles J. Hasselquist Gustaf Egnell Torgny Näsholm Peter Högberg 《Plant and Soil》2014,381(1-2):45-60
Background and aims
To find out how N-saturated forests can return to an N-limited state, we examined the recovery of biotic N sinks under decreasing N supply.Methods
. We studied a 40-year-old experiment in Pinus sylvestris forest, with control plots, N0, three N treatments, N1-N3, of which N3 was stopped after 20 years, allowing observation of recovery.Results
In N3, the N concentration in foliage was still slightly elevated, but the N uptake capacity of ectomycorrhizal (ECM) roots in N3 was no longer lower than in N0. Per area the amount of a biomarker for fungi, here mainly attributed ECM, was higher in N3 and N0 than in N1 and N2. Retention of labeled 15NH4 + by the soil was greater in the control (99 %) and N3 (86 %), than in N1 (45 %) and N2 (29 %); we ascribe these differences to biotic retention because cation exchange capacity did not vary. Gross N mineralisation and retention of N correlated, negatively and positively, respectively, with abundance of ECM fungal biomarker.Conclusions
. The results suggest a key role for ECM fungi in regulating the N cycle. We propose, in accordance with plant C allocation theory, that recovery is driven by increased tree below-ground C allocation to ECM roots and fungi. 相似文献2.
3.
Christina Halling Sofia A. Wikström Gustaf Lilliesköld-Sjöö Erik Mörk Elisabeth Lundsør Giuseppe C. Zuccarello 《Journal of applied phycology》2013,25(1):89-95
Seaweed farming has a crucial role in the development of future sustainable mariculture. In the same time, spreading of introduced species or genotypes from farms may threaten local ecosystems. We analyzed a molecular marker (mitochondrial cox2-3 spacers) from cultivated and wild specimen of the widely farmed seaweeds Eucheuma and Kappaphycus, collected in Zanzibar on the African east coast where commercial farming was introduced in 1989. Genotypes of presumed Asian origin were found growing on coral reefs and drifting in seagrass meadows, indicating that genotypes introduced for farming have established successfully in the wild in Zanzibar. Only a very low number of genotypes, all of Asian origin, were found in the farms. This indicates a low accessible gene pool, which can limit the capacity for adaptation to changed conditions and disease resistance in the farming system. African genotypes were found in a few sites, showing the potential for future farming of native strains. The ecological effects of the Asian genotypes introduced to coral reefs should also be further investigated in order to evaluate the risk connected with further introductions of new foreign strains. 相似文献
4.
Peat mosses (Sphagnum) largely govern carbon sequestration in Northern Hemisphere peatlands. We investigated functional traits related to growth and decomposition in Sphagnum species. We tested the importance of environment and phylogeny in driving species traits and investigated trade‐offs among them. We selected 15 globally important Sphagnum species, representing four sections (subgenera) and a range of peatland habitats. We measured rates of photosynthesis and decomposition in standard laboratory conditions as measures of innate growth and decay potential, and related this to realized growth, production, and decomposition in their natural habitats. In general, we found support for a trade‐off between measures of growth and decomposition. However, the relationships are not strong, with r ranging between 0.24 and 0.45 for different measures of growth versus decomposition. Using photosynthetic rate to predict decomposition in standard conditions yielded R2 = 0.20. Habitat and section (phylogeny) affected the traits and the trade‐offs. In a wet year, species from sections Cuspidata and Sphagnum had the highest production, but in a dry year, differences among species, sections, and habitats evened out. Cuspidata species in general produced easily decomposable litter, but their decay in the field was hampered, probably due to near‐surface anoxia in their wet habitats. In a principal components analysis, PCA, photosynthetic capacity, production, and laboratory decomposition acted in the same direction. The species were imperfectly clustered according to vegetation type and phylogeny, so that some species clustered with others in the same section, whereas others clustered more clearly with others from similar vegetation types. Our study includes a wider range of species and habitats than previous trait analyses in Sphagnum and shows that while the previously described growth–decay trade‐off exists, it is far from perfect. We therefore suggest that our species‐specific trait measures offer opportunities for improvements of peatland ecosystem models. Innate qualities measured in laboratory conditions translate differently to field responses. Most dramatically, fast‐growing species could only realize their potential in a wet year. The same species decompose fast in laboratory, but their decomposition was more retarded in the field than that of other species. These relationships are crucial for understanding the long‐term dynamics of peatland communities. 相似文献
5.
Abstract We have studied adhesion and uptake of C. trachomatis serovar E in McCoy cells under various infection conditions. Adhesion and uptake of chlamydiae was completed about 3 h after the initiation of stationary infection at 37°C, but ingestion of cell membrane-attached organisms was finished within 0.5 h at 37°C. Reincubated chlamydiae, not attached after 3 h at 37°C, attached readily to fresh McCoy cell monolayers, but to a lesser extent than the original inoculum. Our results indicate that the lack of further attachment after 3 h incubation at 37°C under stationary infection conditions has complex causes, involving both host cell and parasite. Centrifugation did not affect the uptake of chlamydiae already bound to the cell membrane, suggesting that the uptake phase of C. trachomatis serovar E by McCoy cells is unaffected by centrifugation. 相似文献
6.
Krishnamurthy Ramanarayanan Arrhenius Gustaf Eschenmoser Albert 《Origins of life and evolution of the biosphere》1999,29(4):333-354
Amidotriphosphate (0.1 M) in aqueous solution at near neutral pH in the presence of magnesium ions (0.25 M) converts glycolaldehyde (0.025 M) within days at room temperature into glycolaldehyde phosphate in (analytically) nearly quantitative yields (76% in isolated product). This robust phosphorylation process was observed to proceed at concentrations as low as 30 M glycolaldehyde and 60 M phosphorylation reagent under otherwise identical conditions. In sharp contrast, attempts to achieve a phosphorylation of glycolaldehyde with cyclotriphosphate (trimetaphosphate) as phosphorylating reagent were unsuccessful. Mechanistically, the phosphorylation of glycolaldehyde with amidotriphosphate is an example of intramolecular delivery of the phosphate group. 相似文献
7.
An instrument with integrated flow injection analysis (FIA) system has been developed for on-line monitoring a process for conversion of biomass under field condition. The instrument consists of a newly designed biosensor for easy renewal of the bio-receptor without disassembling the sensor, a FIA controller for controlling the analysis operations, and a computer-based data acquisition system for data recording and processing. The instrument performed a sequence operations automatically including preparation of sample in the desired concentration, sample loading, sample injection, signal recording, data processing, and self-cleaning of the system. This makes the instrument being an interesting and promising device for on-line process monitoring. 相似文献
8.
A previously developed biosensor for fast estimation of short-term biochemical oxygen demand (BODst) was used for off-line monitoring of intermediate products from the initial step of an anaerobic process in laboratory scale. Good agreement was generally achieved between the results from the biosensor method and the conventional 5-day test except for samples with high content of organic polymers. During the period of agreement between the measurement principles, good correlation was achieved between the biogas production rate and the organic loading rate. The results from this study demonstrate that BODst can be a successful monitoring parameter to achieve a better process control. 相似文献
9.
Distel DL Amin M Burgoyne A Linton E Mamangkey G Morrill W Nove J Wood N Yang J 《Molecular phylogenetics and evolution》2011,61(2):245-254
The ability to consume wood as food (xylotrophy) is unusual among animals. In terrestrial environments, termites and other xylotrophic insects are the principle wood consumers while in marine environments wood-boring bivalves fulfill this role. However, the evolutionary origin of wood feeding in bivalves has remained largely unexplored. Here we provide data indicating that xylotrophy has arisen just once in Bivalvia in a single wood-feeding bivalve lineage that subsequently diversified into distinct shallow- and deep-water branches, both of which have been broadly successful in colonizing the world’s oceans. These data also suggest that the appearance of this remarkable life habit was approximately coincident with the acquisition of bacterial endosymbionts. Here we generate a robust phylogeny for xylotrophic bivalves and related species based on sequences of small and large subunit nuclear rRNA genes. We then trace the distribution among the modern taxa of morphological characters and character states associated with xylotrophy and xylotrepesis (wood-boring) and use a parsimony-based method to infer their ancestral states. Based on these ancestral state reconstructions we propose a set of plausible hypotheses describing the evolution of symbiotic xylotrophy in Bivalvia. Within this context, we reinterpret one of the most remarkable progressions in bivalve evolution, the transformation of the “typical” myoid body plan to create a unique lineage of worm-like, tube-forming, wood-feeding clams. The well-supported phylogeny presented here is inconsistent with most taxonomic treatments for xylotrophic bivalves, indicating that the bivalve family Pholadidae and the subfamilies Teredininae and Bankiinae of the family Teredinidae are non-monophyletic, and that the principle traits used for their taxonomic diagnosis are phylogenetically misleading. 相似文献
10.