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Annual Rings (annual + ring)

Distribution by Scientific Domains

Earth and Environmental Science	75%

Selected Abstracts

Annual sex hormonal profiles, gonad development and age determination of the Mekong giant catfish (Pangasianodon gigas, Chevey)

AQUACULTURE RESEARCH, Issue 15 2003
A Manosroi
Abstract Annual sex hormonal profiles, gonad development and age determination of 18 (13,14 kg body weight) and three (145,226 kg body weight) Mekong giant catfish (MGC) (Pangasianodon gigas, Chevey) reared in earthen ponds in Chiang Mai and from the Mekong River in Chiang Rai, Thailand, respectively, were investigated. The hormonal profiles were determined from blood samples of the fish by electrochemiluminescence immunoassay during May to August in 2000. The highest testosterone levels of 0.06 ng mL,1 in both sexes and the highest oestradiol of 47.8 and 14.23 pg mL,1 in females and males, respectively, were observed in May. The gonadosomatic index was found to be 0.07 for males and 0.38 for females from ponds in comparison with 2.27 for males and 8.29 for females from the Mekong River. Higher development stages of spermatocytes and oocytes of the cultured fish in May than in February and November were demonstrated. No mature germ cells were obtained from either the males or females, indicating no sexual maturity. The average age of fish was determined from the annual rings of the cross-section of the pectoral fins by a stereomicroscope. The average age of fish in earthen pond determined from the annual ring was 8 years, which agreed with the actual culture records, while those from the Mekong River were 21 years. This information will be beneficial for the breeding programmes and conservation of the MGC. [source]

Dating floodplain sediments using tree-ring response to burial,

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2005
Jonathan M. Friedman
Abstract Floodplain sediments can be dated precisely based on the change in anatomy of tree rings upon burial. When a stem of tamarisk (Tamarix ramosissima) or sandbar willow (Salix exigua) is buried, subsequent annual rings in the buried section resemble the rings of roots: rings become narrower, vessels within the rings become larger, and transitions between rings become less distinct. We combined observations of these changes with tree-ring counts to determine the year of deposition of sedimentary beds exposed in a 150-m-long trench across the floodplain of the Rio Puerco, a rapidly filling arroyo in New Mexico. This method reliably dated most beds thicker than about 30 cm to within a year of deposition. Floodplain aggradation rates varied dramatically through time and space. Sediment deposition was mostly limited to brief overbank flows occurring every few years. The most rapid deposition occurred on channel-margin levees, which migrated laterally during channel narrowing. At the decadal timescale, the cross-section-average sediment deposition rate was steady, but there was a shift in the spatial pattern of deposition in the 1980s. From 1936 to 1986, sediment deposition occurred by channel narrowing, with little change in elevation of the thalweg. After 1986 sediment deposition occurred by vertical aggradation. From 1936 to 2000 about 27 per cent of the arroyo cross-section filled with sediment. The rate of filling from 1962 to 2000 was 0·8 vertical m/decade or 85 m2/decade. Published in 2005 by John Wiley & Sons, Ltd. [source]

Seasonal variation in ,13C and ,18O of cellulose from growth rings of Pinus radiata

PLANT CELL & ENVIRONMENT, Issue 11 2002
M. M. Barbour
Abstract Seasonal variation in ,13C and ,18O of cellulose (,13Cc and ,18Oc) was measured within two annual rings of Pinus radiata growing at three sites in New Zealand. In general, both ,13Cc and ,18Oc increased to a peak over summer. The three sites differed markedly in annual water balance, and these differences were reflected in ,13Cc and ,18Oc. Average ,13Cc and ,18Oc from each site were positively related, so that the driest site had the most enriched cellulose. ,13Cc and ,18Oc were also related within each site, although both the slope and the closeness of fit of the relationship varied between sites. Supporting the theory, the site with the lowest average relative humidity also had the greatest change in ,18Oc, change in ,13Cc. Specific climatic events, such as drought or high rainfall, were recorded as a peak or a trough in enrichment, respectively. These results suggest that seasonal and between-site variation in ,13Cc and ,18Oc are driven by the interaction between variation in climatic conditions and soil water availability, and plant response to this variation. [source]