First decadal response to treatment in a disturbance-based silviculture experiment in Maine     

Justin E. ArseneaultMike R. Saunders  Robert S. SeymourRobert G. Wagner 《Forest Ecology and Management》2011,262(3):404-412

Disturbance-based silvicultural systems generally seek to promote complex stand structures that are consistent with temporal and spatial patterns of natural disturbance while allowing for the sustainable harvest of timber. Gap-based harvesting systems are commonly used within this framework because they can be designed to approximate the frequencies and spatial patterns of a wide array of disturbance regimes. Patterns in stand-level growth, sapling recruitment and regeneration response were examined for one such gap-based system, the Acadian Forest Ecosystem Research Program (AFERP) in central Maine, that was designed to emulate the annual 1% disturbance frequency typical of the northeastern United States and Canada. A decade after treatment, stand-level differences in basal area growth and density between two gap-based treatments and an unharvested control were not statistically significant, largely due to low replication, but within-stand growth and regeneration responses differed strongly by spatial position relative to harvest gaps. Regeneration of shade-tolerant and intolerant species increased regardless of gap size, likely a response to increasing light availability from canopy openings due to harvesting and mortality. Further, there was evidence of gap size effects on sapling recruitment as large gaps (>1000 m²) favored the growth and survival of mid-successional species such as red maple and white pine, while small gaps (<1000 m²) favored late-succession species such as eastern hemlock and spruce. Overstory growth rates also differed by both species and position relative to harvest gaps with most species growing best in gaps and better along gap edges than in adjacent forest. Notably, overstory growth rates for white pine were not influenced by spatial position. These results suggest harvest gaps may have significant growth and regeneration impacts in adjacent, yet unharvested areas, which could lead to profound differences in forest development over the rotation. Obviously, longer-term studies of gap-based systems are needed to more clearly elucidate these responses.  相似文献   

Pollutant loadings from solvay waste beds to lower Ninemile Creek,New York     

Steven W. Effler  Carol M. Brooks  Jeffrey M. Addess  Susan M. Doerr  Michelle L. Storey  Bruce A. Wagner 《Water, air, and soil pollution》1991,55(3-4):427-444

Concentrations of Cl, total ammonia (TNH₃), NO₃ plus NO₂, total P (TP), and soluble reactive P (SRP) were measured at two sites, located 5 km apart, on Ninemile Creek, New York, for a period of more than 8 mo. The sites bound the most recently formed Solvay waste beds, associated with the production of soda ash, that adjoin the creek. Concentrations of Cl and T-NH₃ increased on average by factors of 16.1 and 7.6, respectively, over the monitored stream reach. The estimated average loadings of these materials to the stream over this reach were 2.3 × 10⁵ and 1.2 × 102 kg d^?1, respectively. These inputs are attributable to the Solvay waste beds. The loading of Cl from this source has not changed significantly over a 4 yr period since the closure of the soda ash manufacturing facility. This is the single largest source of Cl, and the second largest source of T-NH₃, to polluted Onondaga Lake. Profiles of Cl in the lake indicated that at times the creek inflow plunges to subsurface layers as a result of its elevated density. This is at least in part a result of the creek's ionic enrichment. The concentration of SRP decreased by a factor of 2.0 on average over the study reach, probably due to adsorption to the CaCO₃ deposits that cover the stream bed in this area. However, the TP load from the creek to the lake is not significantly affected by this phenomenon.  相似文献   

Vertikaler Wasser- und Nitrattransport in tiefere Bodenschichten süddeutscher Ackerstandorte     

Reinhold Funk  Franz-Xaver Maidl  Bernhard Wagner  Gerhard Fischbeck 《植物养料与土壤学杂志》1995,158(4):399-406

Vertical water and nitrate movement into deeper soil layers on fields located in the south of Germany In Southern Bavaria, selected fields from deep loess and sandy sediments were sampled to a depth of maximum 10 m every 4 months, in order to determine the basic processes of water and nitrate movement in the course of the year. The downward movement of water and nitrate followed the principle of piston flow only in the intermediate vadose zone of loess soils with a leaching distance amounting 0.8 m per year. On the other hand, an accelerated as well as a delayed transport was observed in the zone of evapotranspiration of loess soils and in the whole profile of sandy soils, not being in accordance with the simple simulation model FLOTRA based on the classic theories of transport (Darcy flow, convection-dispersion-equation). Preferential flow led to the leaching of nitrate from the top soil to the lower boundary of the evapotranspiration zone of loess soils in 2 m depth, in winter and spring. In sandy soils nitrate was leached to the groundwater table in 4–6 m depth after extensive rainfall.  相似文献   

The Politics of Knowledge. Activist Movements in Medicine and Planning. Lily M. Hoffman. State University of New York Press, Albany, 1989. xii, 290 pp. $54.50; paper, $17.95. SUNY Series in the Sociology of Work     

Wagner DH 《Science (New York, N.Y.)》1990,247(4940):347-348

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RNA complementary to a herpesvirus alpha gene mRNA is prominent in latently infected neurons   总被引：107，自引：0，他引：107  

J G Stevens  E K Wagner  G B Devi-Rao  M L Cook  L T Feldman 《Science (New York, N.Y.)》1987,235(4792):1056-1059

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Genetics and phenogenetics of mitochondria   总被引：6，自引：0，他引：6  

R P Wagner 《Science (New York, N.Y.)》1969,163(871):1026-1031

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Effect of the Vinca alkaloids on RNA synthesis in human cells in vitro   总被引：3，自引：0，他引：3  

E K Wagner  B Roizman 《Science (New York, N.Y.)》1968,162(853):569-570

The Vinca alkaloids vinblastine sulfate and vincrystine sulfate, which are mitotic poisons, inhibit RNA synthesis in human (HEp-2) cells cultured in vitro. Analyses of RNA synthesis by cells treated with these drugs by acrylamide gel electrophoresis show that 28s rRNA and to a lesser extent 18s rRNA are preferentially inhibited. The synthesis of tRNA is affected much less than that of rRNA. The present experiments suggest that the drugs inhibit both the synthesis and processing of the nucleolar RNA precursors of rRNA. An explanation is also given for previous reports that these alkaloids preferentially inhibit the synthesis of tRNA in animal cells in vitro.  相似文献   

Submicrometer Superconducting YBa2Cu3O6+x Particles Made by a Low-Temperature Synthetic Route     

Horowitz HS  McLain SJ  Sleight AW  Druliner JD  Gai PL  Vankavelaar MJ  Wagner JL  Biggs BD  Poon SJ 《Science (New York, N.Y.)》1989,243(4887):66-69

Evidence suggests that superconducting, orthorhombic YBa(2)Cu(3)O(6+x)+ (x greater, similar 0.5) is always produced by oxidation of the oxygen-deficient, tetragonal form (x less, similar 0.5) of this phase (commonly referred to as 123). A synthetic route whereby solution-derived, carbon-free precursors are decomposed at 650 degrees to 700 degrees C in inert atmosphere to yield tetragonal 123 is now available. Appropriate precursors include hydrated oxides derived from the hydrolysis of organometallic solutions and aqueous solution-derived hyponitrites. Subsequent oxidation of the tetragonal phase at 400 degrees C results in submicrometer particles of orthorhombic 123. Superconductivity (T(c) onset approximately 87 K) has been confirmed in these materials by both Meissner effect and specific-heat measurements.  相似文献   

Fission track ages and ages of deposition of deep-sea microtektites     

Gentner W  Glass BP  Storzer D  Wagner GA 《Science (New York, N.Y.)》1970,168(3929):359-361

The Australasian and Ivory Coast deep-sea microtektites have fission track ages of 0.71 and 1.09 million years, respectively. These ages are in good agreement with the ages of deposition of the microtektites determined from paleomagnetic data. Both the fission track ages and ages of deposition of the microtektites agree with the potassium/ argon and fission track ages of tektites from the respective tektite strewn fields.  相似文献   

A zinc clasp structure tethers Lck to T cell coreceptors CD4 and CD8     

Kim PW  Sun ZY  Blacklow SC  Wagner G  Eck MJ 《Science (New York, N.Y.)》2003,301(5640):1725-1728

The T cell coreceptors CD4 and CD8 both associate via their cytoplasmic tails with the N-terminus of the Src-family tyrosine kinase Lck. These interactions require zinc and are critical for T cell development and activation. We examined the folding and solution structures of ternary CD4-Lck-Zn2+ and CD8alpha-Lck-Zn2+ complexes. The coreceptor tails and the Lck N-terminus are unstructured in isolation but assemble in the presence of zinc to form compactly folded heterodimeric domains. The cofolded complexes have similar "zinc clasp" cores that are augmented by distinct structural elements. A dileucine motif required for clathrin-mediated endocytosis of CD4 is masked by Lck.  相似文献