Soil respiration is a main dynamic process of carbon cycle in wetland. It is important to contribute to global climate changes.
Water table and nutritious availability are significant impact factors to influence responses of CO2 emission from wetland soil to climate changes. Twenty-four wetland soil monoliths at 4 water-table positions and in 3 nitrogen
status have been incubated to measure rates of CO2 emission from wetland soils in this study. Three static water-table controls and a fluctuant water-table control, with 3
nitrogen additions in every water-table control, were carried out. In no nitrogen addition treatment, high CO2 emissions were found at a static low water table (I) and a fluctuant water table (IV), averaging 306.7mg/(m2·h) and 307.89mg/(m2·h), respectively, which were 51%–57% higher than that at static high water table (II and III). After nitrogen addition, however,
highest CO2 emission was found at II and lowest emission at III. The results suggested that nutritious availability of wetland soil might
be important to influence the effect of water table on the CO2 emission from the wetland soil. Nitrogen addition led to enhancing CO2 emissions from wetland soil, while the highest emission was found in 1N treatments other than in 2N treatments. In 3 nutritious
treatments, low CO2 emissions at high water tables and high CO2 emissions at low water tables were also observed when water table fluctuated. Our results suggested that both water table
changes and nutritious imports would effect the CO2 emission from wetland.
Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 90211003) and the Knowledge Innovation
Program of Chinese Academy of Sciences (No. KACX3-SW-332)
Biography: YANG Ji-song (1978-), male, a native of Chengwu of Shandong Province, Ph.D. candidate, specialized in environmental
ecology and wetland biogeochemistry. E-mail: yangjisong@neigae.ac.cn 相似文献
Appearing in the composite spectral data of BATSE, EGRET and COMPTEL for GRB 910503, there is a bump at around 1600 keV. We perform a statistical analysis on the spectral data, trying to find out if the bump could be accounted for by a blue-shifted and significantly broadened rest frame line due to the Doppler effect of an expanding fireball surface. We made an F-test and adopted previously proposed criteria. The study reveals that the criteria are well satisfied and the feature can be interpreted as the blue shifted 6.4 keV line. Prom the fit with this line taken into account, we find the Lorentz factor of this source to be P = 116-9+9 (at the 68% confident level,△x2 = 1) and the rest frame spectral peak energy to be E0,p- 2.96-0.18+0.24 keV. Although the existence of the emission line feature requires other independent tests to confirm, the analysis suggests that it is feasible to detect emission line features in the high energy range of GRB spectra when taking into account the Doppler effect of fireball expansion. 相似文献
A new equivalent map projection called the parallels plane projection is proposed in this paper. The transverse axis of the parallels plane projection is the expansion of the equator and its vertical axis equals half the length of the central meridian. On the parallels plane projection, meridians are projected as sine curves and parallels are a series of straight, parallel lines. No distortion of length occurs along the central meridian or on any parallels of this projection. Angular distortion and the proportion of length along meridians (except the central meridian) introduced by the projection transformation increase with increasing longitude and latitude. A potential application of the parallels plane projection is that it can provide an efficient projection transformation for global discrete grid systems.
Regular distribution patterns of elements Ca, Sr, K, Na, Mg, Fe, Mn, Ti, Cu, Co, Ni, Zn, Pb, Cr, Rb, Ba, Cd, and U in Late
Quaternary strata have been studied in detail. The regional variation patterns of elements in these strata are similar to
those in recent surface sediments, showing that the sedimentary environment has been relatively stable since Late Quaternary.
Element distribution changes with the variations of lithological characters. Contents of Ca and Sr increase in coarse sediments,
while those of other elements decrease. Na content increases in the pumice layer. Mn, content tends to increase sharply towards
the surface layer. Ca content decreases sharply in strata where water depth is more than 2,000 m. The strata can be divided
based on the distribution curves of element assemblages. The variations in contents of most elements in Holocene Series are
smaller than those in Late Pleistocene Series, which might be related to the factors of glacial and interglacial changes,
sea level fluctuations and material source differences.
Contribution No. 1488 from Institute of Oceanology, Academia Sinica 相似文献