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Shrub encroachment into grass-dominated biomes is occurring globally due to a variety of anthropogenic activities, but the consequences for carbon (C) inputs, storage and cycling remain unclear. We studied eight North American graminoid-dominated ecosystems invaded by shrubs, from arctic tundra to Atlantic coastal dunes, to quantify patterns and controls of C inputs via aboveground net primary production (ANPP). Across a fourfold range in mean annual precipitation (MAP), a key regulator of ecosystem C input at the continental scale, shrub invasion decreased ANPP in xeric sites, but dramatically increased ANPP (>1000 g m−2) at high MAP, where shrub patches maintained extraordinarily high leaf area. Concurrently, the relationship between MAP and ANPP shifted from being nonlinear in grasslands to linear in shrublands. Thus, relatively abrupt (<50 years) shifts in growth form dominance, without changes in resource quantity, can fundamentally alter continental-scale pattern of C inputs and their control by MAP in ways that exceed the direct effects of climate change alone. [ABSTRACT FROM AUTHOR]

Studies the interdependence of Myrica cerifera seedlings and the nodule forming actinomycete, Frankia in a coastal environment. Spatial distribution of host plant seedlings in relation to the root symbiont on a Virginia barrier island; Bioassay quantification of the extent of Frankia distribution; Soil chloride level where Myrica cerifera seedlings occurred.

Presents information on a study which investigated the potential species replacement within low-diversity shrub thicket soil seed banks in Virginia barrier island. Methods used in the study; Materials; Findings of the study.

The actinorhizal shrub, Myrica cerifera L., is widespread in coastal areas where it may be exposed to variable saline conditions. In growth chamber studies, 5-month-old seedlings remained viable during exposure to 150 mM NaCl for 35 d, though concentrations above 50 mM significantly depressed plant and root nodule growth. Concentrations of NaCl above 50 mM also depressed stomatal conductance to water vapour diffusion and net photosynthetic rates. Relative to control plants, nitrogenase activity per g dry weight of nodules decreased for 21 d in plants subjected to a range of NaCl concentrations. By day 35, plants exposed to 25 and 50mM NaCl had recovered some nitrogenase activity relative to the controls, whereas plants receiving 100 and 150 mM had not. At 35 d, plants treated with 150 mM NaCl had a rate of N2 fixation per g dry weight of nodule tissue 26% of that in control plants. However, no mortality had occurred, and full recovery followed the conclusion of the experiment. Thus, although periodic natural increases in salinity from sea spray or storm over wash may not lead to plant mortality, growth and N2 fixation will be significantly decreased in M. cerifera. [ABSTRACT FROM AUTHOR]

Plant morphology in the field in Virginia, USA, and growth responses to applied NaCl in a glasshouse were determined for two populations of Opuntia humifusa (Rafinesque) Rafinesque, one from an inland site and the other from the marine strand, which differed in potential exposure to salinity. Cladode dimensions, plant height and rooting depth varied significantly between the populations. Application of NaCl in 50 mM increments up to 400 mM every 3 days for 6 weeks caused the cladodes to decrease up to 30% in thickness, the decrease being about 20% more at 50 to 150 mM NaCl for plants from the inland site than from the marine strand. Inhibition by 150 mM NaCl of the maximum rate of net CO2 uptake and of the total CO2 uptake over a 24-h period was greater for the inland population. Growth, especially of roots, was inhibited by applied NaCl, with a decrease in biomass above 200 mM NaCl for plants from the inland site and not until 400 mM for those from the marine strand. Although the root Na+ level was the same for plants from the two populations, reaching a maximum of about 8 mg (g dry weight)-1 at 200 mM NaCl, the cladode Na+ level was two-fold higher for plants from the marine strand than from the inland site. Thus, exclusion of Na+ from the cladodes is not the reason for the greater NaCl tolerance of O. humifusa from the marine strand, which is a habitat that can experience periodic episodes of high salinity. [ABSTRACT FROM AUTHOR]

Compares canopy gaps to intact shrub thicket (Myrica cerifera) gaps on a Virginia barrier island with regard to microclimate, edaphic characteristics, microsite variability and colonizing species. Difference in microsite variability at gap surface between midisland and bayside gaps; Similarity of the microclimate of the midisland gaps to the bayside thicket understory.

This article presents the report of the secretary of the American Sociological Association. The Council approved by mail ballot minutes of its Chicago, Illinois meetings, and these are published in the December 1959 issue of the American sociological Review. News was received of the sudden death of President Howard Becker on June 8, 1960. In accordance with the Constitution, his duties were assumed by Wilbert Moore as Vice-President. Sociologist Harry Alpert was elected Editor of the American Sociological Review by vote of the Council and the Committee on Publications. He will take office at the close of 1960 annual meetings. In agreement with the recommendation of the Sub-committee on Sociology in the Federal Government of the Committee on the Profession, the Executive Committee voted that the central office should remain in New York but that arrangements should be made as early as practicable for high-level Washington representation. The Association has received from the Asia Foundation a further grant of 2,500 dollars for the purpose of encouraging closer relations between Asian and American sociologists.

This article presents proceedings of the 55th annual meeting of the American Sociological Association held at the Statler Hilton Hotel, New York City from August 28-31, 1960. The first meeting of the 1960 Council was called to order on August 28, 1960 by Vice-President Wilbert Moore. Members of the 1960 Council present in the meeting included Reirihard Bendix, John Clausen, W. Fred Cottrell, Robert Faris, William Goode, George Homans, Rex Hopper, Seymour Lipset, Charles Loomis, Walter Martin, Robert Merton, Wilbert Moore, Charles Page, and John Riley. Three resolutions pertaining to various aspects of the certification problem were received from the Ohio Valley Sociological Society and it was voted that these matters be studied by an ad hoc committee consisting of Talcott Parsons, Robert Merton and Guy Swanson and their findings reported to the first meeting of the 1961 Council. Regarding the site for 1963 meetings, the Council reaffirmed the earlier decision to meet on the West Coast with the detailed arrangements as to place and facilities being left in the hands of the president-elect for that meeting, the Secretary and the Executive Officer.

Investigates the effect of germanium implantation on metal-oxide-semiconductor avalanche injection. Implantation of various doses of germanium into the Si-SiO[sub 2] interface; Use of the avalanche injection technique to generate hot electrons in the substrate; Description of avalanche injection by Young and Nicollian.