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61.
Daniel L. Peters Terry D. Prowse Phil Marsh Peter M. Lafleur James M. Buttle 《Wetlands Ecology and Management》2006,14(3):221-243
The Peace-Athabasca Delta (PAD) is one of the world’s largest freshwater deltas. Many of its shallow (<1.5 m) lakes and wetlands
are perched above surrounding waterways. The delta has experienced a number of wetting and drying intervals. The latest drying
trend ended in 1996 when high waters, generated under ice-jam and open-water conditions, recharged a number of the perched
basins. The objective of this study was to determine the relative importance of hydroclimatic components on the persistence
of water. A water-balance model was developed to simulate water-level responses following a flood event. Basin response was
tested against a range of historical hydroclimatic conditions that have occurred in the delta during the 20th century. Ponded
water duration in a 0.8 m deep perched basin was 5 years for the cool-dry period of the 1920s, slightly longer for the post-1974
flood era, and up to 9 years for the wet conditions of the 1940s and 1950s. Water drawdown occurred in almost every year and
was almost exclusively due to evaporation exceeding precipitation. Net groundwater flux was minimal. Given the overlying importance
of the floodwater component in the water balance of perched basins, the next step is to investigate the causes, spatial sources
and frequency of flooding. This water balance model presented in this paper offers a useful tool for the management of the
duration of water in perched wetlands of the PAD, which can help preserve essential habitat for wildlife. 相似文献
62.
Two skeletons of the large compsognathid Sinocalliopteryx gigas include intact abdominal contents. Both specimens come from the Jianshangou Beds of the lower Yixian Formation (Neocomian), Liaoning, China. The holotype of S. gigas preserves a partial dromaeosaurid leg in the abdominal cavity, here attributed to Sinornithosaurus. A second, newly-discovered specimen preserves the remains of at least two individuals of the primitive avialan, Confuciusornis sanctus, in addition to acid-etched bones from a possible ornithischian. Although it cannot be stated whether such prey items were scavenged or actively hunted, the presence of two Confuciusornis in a grossly similar state of digestion suggests they were consumed in rapid succession. Given the lack of clear arboreal adaptations in Sinocalliopteryx, we suggest it may have been an adept stealth hunter. 相似文献
63.
64.
Paul C. D. Newton Mark Lieffering W. M. Saman D. Bowatte Shona C. Brock Chris L. Hunt Phil W. Theobald Des J. Ross 《Plant and Soil》2010,336(1-2):433-441
A decline in the availability of nitrogen (N) for plant growth (progressive nitrogen limitation or PNL) is a feedback that could constrain terrestrial ecosystem responses to elevated atmospheric CO2. Several long-term CO2 enrichment experiments have measured changes in plant and soil pools and fluxes consistent with PNL but evidence for PNL in grasslands is limited. In an 11 year Free Air CO2 Enrichment (FACE) experiment on grazed grassland we found the amount of N harvested in aboveground plant biomass was greater at elevated CO2 but declined over time to be indistinguishable from ambient after 5 years. Re-wetting after a major drought resulted in a large input of N from mineralisation and a return to a higher N harvested under elevated CO2 followed by a further decline. Over these two periods the amount of N in soil significantly increased at elevated CO2. Data from mesocosms introduced into the rings at intervals, and therefore having different lengths of exposure to CO2, showed plant N availability declined at elevated CO2 reaching a new equilibrium after 6 years of exposure. We conclude that the availability of N for plants in this grassland is dynamic but the underlying trend at elevated CO2 is for PNL. 相似文献
65.
Istem Fer Anthony K. Gardella Alexey N. Shiklomanov Eleanor E. Campbell Elizabeth M. Cowdery Martin G. De Kauwe Ankur Desai Matthew J. Duveneck Joshua B. Fisher Katherine D. Haynes Forrest M. Hoffman Miriam R. Johnston Rob Kooper David S. LeBauer Joshua Mantooth William J. Parton Benjamin Poulter Tristan Quaife Ann Raiho Kevin Schaefer Shawn P. Serbin James Simkins Kevin R. Wilcox Toni Viskari Michael C. Dietze 《Global Change Biology》2021,27(1):13-26
In an era of rapid global change, our ability to understand and predict Earth's natural systems is lagging behind our ability to monitor and measure changes in the biosphere. Bottlenecks to informing models with observations have reduced our capacity to fully exploit the growing volume and variety of available data. Here, we take a critical look at the information infrastructure that connects ecosystem modeling and measurement efforts, and propose a roadmap to community cyberinfrastructure development that can reduce the divisions between empirical research and modeling and accelerate the pace of discovery. A new era of data‐model integration requires investment in accessible, scalable, and transparent tools that integrate the expertise of the whole community, including both modelers and empiricists. This roadmap focuses on five key opportunities for community tools: the underlying foundations of community cyberinfrastructure; data ingest; calibration of models to data; model‐data benchmarking; and data assimilation and ecological forecasting. This community‐driven approach is a key to meeting the pressing needs of science and society in the 21st century. 相似文献
66.
Sarah C. Webb Anthony Attwood Tony Brooks Tom Freeman Phil Gardner Clare Pritchard Debbie Williams Peter Underhill Mark A. Strivens Andy Greenfield Ekaterina Pilicheva 《Mammalian genome》2004,15(9):740-747
Microarrays allow monitoring of gene expression for tens of thousands of genes in parallel and are being used routinely to generate huge amounts of valuable data. Handling and analysis of such data are becoming major bottlenecks in the utilization of the technology. To enable the researcher to interpret the results postanalysis, we have developed a laboratory information management system for microarrays (LIMaS) with an n-tier Java front-end and relational database to record and manage large-scale expression data preanalysis. This system enables the laboratory to replace the paper trail with an efficient and fully customizable interface giving it the ability to adapt to any working practice, e.g., handling many resources used to form many products (chaining of resources). The ability to define sets of activities, resources, and workflows makes LIMaS MIAME-supportive.LIMaS is available for download at (http://www.mgu.har.mrc.ac.uk/microarray.) 相似文献
67.
Stephanie Eby Deron E. Burkepile Richard W. S. Fynn Catherine E. Burns Navashni Govender Nicole Hagenah Sally E. Koerner Katherine J. Matchett Dave I. Thompson Kevin R. Wilcox Scott L. Collins Kevin P. Kirkman Alan K. Knapp Melinda D. Smith 《Oecologia》2014,175(1):293-303
Large herbivore grazing is a widespread disturbance in mesic savanna grasslands which increases herbaceous plant community richness and diversity. However, humans are modifying the impacts of grazing on these ecosystems by removing grazers. A more general understanding of how grazer loss will impact these ecosystems is hampered by differences in the diversity of large herbivore assemblages among savanna grasslands, which can affect the way that grazing influences plant communities. To avoid this we used two unique enclosures each containing a single, functionally similar large herbivore species. Specifically, we studied a bison (Bos bison) enclosure at Konza Prairie Biological Station, USA and an African buffalo (Syncerus caffer) enclosure in Kruger National Park, South Africa. Within these enclosures we erected exclosures in annually burned and unburned sites to determine how grazer loss would impact herbaceous plant communities, while controlling for potential fire-grazing interactions. At both sites, removal of the only grazer decreased grass and forb richness, evenness and diversity, over time. However, in Kruger these changes only occurred with burning. At both sites, changes in plant communities were driven by increased dominance with herbivore exclusion. At Konza, this was caused by increased abundance of one grass species, Andropogon gerardii, while at Kruger, three grasses, Themeda triandra, Panicum coloratum, and Digitaria eriantha increased in abundance. 相似文献
68.
Koh PO Kwak SD Kim HJ Roh G Kim JH Kang SS Choi WS Cho GJ 《Molecular reproduction and development》2003,64(1):27-31
Pituitary adenylate cyclase activating polypeptide (PACAP) was first isolated from ovine hypothalamus and is known to act as a tropic factor in various cells. Recent report revealed the expression of PACAP and the PACAP type I (PAC(1)) receptor in human and rat placentas at term. Placenta is a critical organ that synthesizes several growth and angiogenic factors for its own growth as well as fetal development. However, there is little information regarding the expression pattern and cellular localization of PACAP and PAC(1) during pregnancy. The aim of this study was to define the expression and distribution of PACAP and PAC(1) receptor mRNAs in the rat placenta during pregnancy. PACAP and PAC(1) receptor mRNAs were expressed in decidual cells, chorionic vessels, and stromal cells of the chorionic villi. Interestingly, the expression of these genes varied with the day of gestation. For example, PACAP and PAC(1) receptor mRNAs expressed in decidual cells on day 13.5 and 15.5, their expression was strong in chorionic vessels and stromal cells of the chorionic villi within the labyrinth zone on day 17.5, 19.5, and 21.5. In fact, as gestation advanced, the expression of PACAP and PAC(1) receptor mRNAs in the decidua cells disappeared, as their high expression became evident in the chorionic vessels and stromal cells of the chorionic villi. Our finding that PACAP and the PAC(1) receptor are co-localized and their genes seemingly co-regulated within specific placental areas, strongly suggest that this peptide may play an important role, as an autoregulator or pararegulator via its PAC(1) receptor, in physiological functioning of the placenta for gestational maintenance. 相似文献
69.
The vascular endothelium acutely autoregulates blood flow in vivo in part through unknown mechanosensing mechanisms. Here, we report the discovery of a new acute mechanotransduction pathway. Hemodynamic stressors from increased vascular flow and pressure in situ rapidly and transiently induce the activity of neutral sphingomyelinase but not that acid sphingomyelinase in a time- and flow rate-dependent manner, followed by the generation of ceramides. This acute mechanoactivation occurs directly at the luminal endothelial cell surface primarily in caveolae enriched in sphingomyelin and neutral sphingomyelinase, but not acid sphingomyelinase. Scyphostatin, which specifically blocks neutral but not acid sphingomyelinase, inhibits mechano-induced neutral sphingomyelinase activity as well as downstream activation of extracellular signal-regulated kinase 1 and 2 (ERK1 and ERK2) by increased flow in situ. We postulate a novel physiological function for neutral sphingomyelinase as a new mechanosensor initiating the ERK cascade and possibly other mechanotransduction pathways. 相似文献
70.