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81.
82.
Hydrologic Regime Controls Soil Phosphorus Fluxes in Restoration and Undisturbed Wetlands 总被引:4,自引:0,他引:4
Allison Aldous Paul McCormick Chad Ferguson Sean Graham Chris Craft 《Restoration Ecology》2005,13(2):341-347
Many wetland restoration projects occur on former agricultural soils that have a history of disturbance and fertilization, making them prone to phosphorus (P) release upon flooding. To study the relationship between P release and hydrologic regime, we collected soil cores from three restoration wetlands and three undisturbed wetlands around Upper Klamath Lake in southern Oregon, U.S.A. Soil cores were subjected to one of three hydrologic regimes—flooded, moist, and dry—for 7.5 weeks, and P fluxes were measured upon reflooding. Soils from restoration wetlands released P upon reflooding regardless of the hydrologic regime, with the greatest releases coming from soils that had been flooded or dried. Undisturbed wetland soils released P only after drying. Patterns in P release can be explained by a combination of physical and biological processes, including the release of iron‐bound P due to anoxia in the flooded treatment and the mineralization of organic P under aerobic conditions in the dry treatment. Higher rates of soil P release from restoration wetland soils, particularly under flooded conditions, were associated with higher total P concentrations compared with undisturbed wetland soils. We conclude that maintaining moist soil is the means to minimize P release from recently flooded wetland soils. Alternatively, prolonged flooding provides a means of liberating excess labile P from former agricultural soils while minimizing continued organic P mineralization and soil subsidence. 相似文献
83.
Johnsen K Maier C Sanchez F Anderson P Butnor J Waring R Linder S 《Plant, cell & environment》2007,30(1):128-134
Quantifying below-ground carbon (C) allocation is particularly difficult as methods usually disturb the root-mycorrhizal-soil continuum. We reduced C allocation below ground of loblolly pine trees by: (1) physically girdling trees and (2) physiologically girdling pine trees by chilling the phloem. Chilling reduced cambium temperatures by approximately 18 degrees C. Both methods rapidly reduced soil CO2 efflux, and after approximately 10 days decreased net photosynthesis (P(n)), the latter indicating feedback inhibition. Chilling decreased soil-soluble C, indicating that decreased soil CO2 efflux may have been mediated by a decrease in root C exudation that was rapidly respired by microbes. These effects were only observed in late summer/early autumn when above-ground growth was minimal, and not in the spring when above-ground growth was rapid. All of the effects were rapidly reversed when chilling was ceased. In fertilized plots, both chilling and physical girdling methods reduced soil CO2 efflux by approximately 8%. Physical girdling reduced soil CO2 efflux by 26% in non-fertilized plots. This work demonstrates that phloem chilling provides a non-destructive alternative to reducing the movement of recent photosynthate below the point of chilling to estimate C allocation below ground on large trees. 相似文献
84.
Rudi Verovnik Branko Micevski Dirk Maes Irma Wynhoff Chris Van Swaay Martin Warren 《Journal of Insect Conservation》2013,17(5):941-947
The Macedonian Grayling is listed as critically endangered in the recent IUCN Red List of European butterflies because of its extreme rarity and habitat loss due to quarrying. This categorisation was, however, based on rather limited knowledge on its actual distribution, population size and habitat requirements. In 2012, we conducted field surveys to acquire more information. We found the species at six new sites extending its known range of suitable habitat to just under 10 km2. The daily population size was estimated using capture-mark-recapture method in the most densely populated part of the Pletvar pass site at more than 650 individuals. Adults proved to be extremely sedentary, not moving far even within the continuous habitat on the same slope. Oviposition was observed on dry plant material and in a rock crevice close to the potential larval host plant Festuca sp. Quarrying is confirmed to be the main threat to the habitat of the Macedonian Grayling with five out of seven populated sites containing active marble quarries. Due to the enlargement of the known area of occupancy, its threat status would now be estimated at endangered. Despite the restricted knowledge about its distribution and trends in the population size, the IUCN criteria proved to be applicable to determine the threat status of a rare and localized butterfly such as Pseudochazara cingovskii. Its original assessment of being called the most threatened butterfly in Europe resulted in immediate research project and subsequent actions that will undoubtedly help to conserve it in the future. 相似文献
85.
86.
Babu M Beloglazova N Flick R Graham C Skarina T Nocek B Gagarinova A Pogoutse O Brown G Binkowski A Phanse S Joachimiak A Koonin EV Savchenko A Emili A Greenblatt J Edwards AM Yakunin AF 《Molecular microbiology》2011,79(2):484-502
Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) and the associated proteins (Cas) comprise a system of adaptive immunity against viruses and plasmids in prokaryotes. Cas1 is a CRISPR-associated protein that is common to all CRISPR-containing prokaryotes but its function remains obscure. Here we show that the purified Cas1 protein of Escherichia coli (YgbT) exhibits nuclease activity against single-stranded and branched DNAs including Holliday junctions, replication forks and 5'-flaps. The crystal structure of YgbT and site-directed mutagenesis have revealed the potential active site. Genome-wide screens show that YgbT physically and genetically interacts with key components of DNA repair systems, including recB, recC and ruvB. Consistent with these findings, the ygbT deletion strain showed increased sensitivity to DNA damage and impaired chromosomal segregation. Similar phenotypes were observed in strains with deletion of CRISPR clusters, suggesting that the function of YgbT in repair involves interaction with the CRISPRs. These results show that YgbT belongs to a novel, structurally distinct family of nucleases acting on branched DNAs and suggest that, in addition to antiviral immunity, at least some components of the CRISPR-Cas system have a function in DNA repair. 相似文献
87.
Taylor Richards Kavindiya Modarage Charlotte Dean Aidan McCarthy-Boxer Helen Hilton Chris Esapa Jill Norman Patricia Wilson Paraskevi Goggolidou 《生物化学与生物物理学报:疾病的分子基础》2019,1865(2):378-390
Autosomal Recessive Polycystic Kidney Disease (ARPKD) is a genetic disorder with an incidence of ~1:20,000 that manifests in a wide range of renal and liver disease severity in human patients and can lead to perinatal mortality. ARPKD is caused by mutations in PKHD1, which encodes the large membrane protein, Fibrocystin, required for normal branching morphogenesis of the ureteric bud during embryonic renal development. The variation in ARPKD phenotype suggests that in addition to PKHD1 mutations, other genes may play a role, acting as modifiers of disease severity. One such pathway involves non-canonical Wnt/Planar Cell Polarity (PCP) signalling that has been associated with other cystic kidney diseases, but has not been investigated in ARPKD. Analysis of the AtminGpg6 mouse showed kidney, liver and lung abnormalities, suggesting it as a novel mouse tool for the study of ARPKD. Further, modulation of Atmin affected Pkhd1 mRNA levels, altered non-canonical Wnt/PCP signalling and impacted cellular proliferation and adhesion, although Atmin does not bind directly to the C-terminus of Fibrocystin. Differences in ATMIN and VANGL2 expression were observed between normal human paediatric kidneys and age-matched ARPKD kidneys. Significant increases in ATMIN, WNT5A, VANGL2 and SCRIBBLE were seen in human ARPKD versus normal kidneys; no substantial differences were seen in DAAM2 or NPHP2. A striking increase in E-cadherin was also detected in ARPKD kidneys. This work indicates a novel role for non-canonical Wnt/PCP signalling in ARPKD and suggests ATMIN as a modulator of PKHD1. 相似文献
88.
89.
Background
Detecting new coding sequences (CDSs) in viral genomes can be difficult for several reasons. The typically compact genomes often contain a number of overlapping coding and non-coding functional elements, which can result in unusual patterns of codon usage; conservation between related sequences can be difficult to interpret – especially within overlapping genes; and viruses often employ non-canonical translational mechanisms – e.g. frameshifting, stop codon read-through, leaky-scanning and internal ribosome entry sites – which can conceal potentially coding open reading frames (ORFs). 相似文献90.