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831.
Yuriko Yano Gaius R. Shaver Edward B. Rastetter Anne E. Giblin James A. Laundre 《Oecologia》2013,173(4):1575-1586
In the foothills of the Brooks Range, Alaska, different glaciation histories have created landscapes with varying soil age. Productivity of most of these landscapes is generally N limited, but varies widely, as do plant species composition and soil properties (e.g., pH). We hypothesized that the projected changes in productivity and vegetation composition under a warmer climate might be mediated through differential changes in N availability across soil age. We compared readily available [water-soluble NH4 +, NO3 ?, and amino acids (AA)], moderately available (soluble proteins), hydrolyzable, and total N pools across three tussock-tundra landscapes with soil ages ranging from 11.5k to 300k years. The effects of fertilization and warming on these N pools were also compared for the two younger sites. Readily available N was highest at the oldest site, and AA accounted for 80–89 % of this N. At the youngest site, inorganic N constituted the majority (80–97 %) of total readily available N. This variation reflected the large differences in plant functional group composition and soil chemical properties. Long-term (8–16 years) fertilization increased the soluble inorganic N by 20- to 100-fold at the intermediate-age site, but only by twofold to threefold at the youngest site. Warming caused small and inconsistent changes in the soil C:N ratio and AA, but only in soils beneath Eriophorum vaginatum, the dominant tussock-forming sedge. These differential responses suggest that the ecological consequences of warmer climates on these tundra ecosystems are more complex than simply elevated N-mineralization rates, and that the responses of landscapes might be impacted by soil age, or time since deglaciation. 相似文献
832.
Seasonal dynamics of the fish parasite Neoplagioporus ayu (Digenea; Opecoelidae; Plagioporinae) in its definitive host, the ayu Plecoglossus altivelis, in the Chikugo River, Kyushu, Japan, was examined. Natural ayu are amphidromous. In the upper Chikugo River, ayu fry raised
in hatcheries are released into the river every spring because the migration of ayu is completely blocked by a dam that has
no fish-pass channel. Ayu collected in April 2003 (within 1 month after release) harbored no N. ayu, but the prevalence of N. ayu rose to about 80% in May. The prevalence, abundance, and maturity of N. ayu were maintained at high levels from June to September. These finding indicate that the life cycle of N. ayu is completed in a freshwater area, although its intermediate hosts have not yet been identified despite the intense examination
of invertebrates. 相似文献
833.
Hideaki Tojo Mayumi Nishida Kunio Matsuoka Koichi Igarashi Osamu Shiho 《Cytotechnology》1995,19(2):161-165
To generate mutant mice, embryonic stem (ES) cells are used as a vehicle for introducing mutations. The establishment of ES cells is diffucult because it requires specific skills and it is time-consuming. We established a novel ES cell line derived from hybrid mice between C57BL/6 and DBA/2 using a modified method. To collect a large number of preimplantational embryos, we collected embryos at the 8-cell stage and cultured them to blastocysts, whereas the usual procedure of preparing the delayed blastocysts demands technical skills. To eliminate unnecessary female cells at an initial stage of inner cell mass culture, male clones were selected by polymerase chain reaction to detect the mouseSry gene. The established ES cell line efficiently contributed to the germ-line when injected into 8-cell embryos of ICR mice. This potency was maintained after manipulation throughout gene targeting.Abbreviations DMEM
Dulbecco's modified Eagle's medium
- FBS
fetal bovine serum
- FIAU
1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodouracil
- LIF
leukemia inhibitory factor
- NEAA
non-essential amino acids 相似文献