过渡带近距离同地分布不同植物群落建群种叶片草酸钙特征

不同功能群植物天然近距离同地分布时有利于比较它们生理特性之间的差异。本文以地处过渡带的宁夏回族自治区境内的红寺堡区和宁夏哈巴湖国家级自然保护区为研究区,用连续组分法测定了近距离分布(间隔在30 m内)的不同生态系统和不同演替阶段的建群种以及同种不同冠层高度和不同生长阶段叶片草酸钙含量。结果表明:荒漠植物群落建群种叶片草酸钙含量显著高于典型草原建群种,演替后期阶段与演替中后期阶段植物叶片草酸钙含量之间差异不显著,3种豆科灌木冠层底部叶片草酸钙含量均显著高于顶部;油蒿(Artemisia ordosica)成龄阶段叶片草酸钙含量显著低于幼龄和老龄阶段。上述研究表明,植物体内草酸钙含量是其对环境长期适应的结果,也与冠层高度和年龄阶段有关。

Comparison of roosting habitat characteristics of two sympatric pheasants during springtime at Dazhong Mountain,southwestern China

Hume's Pheasant(Syrmaticus humiae) and the Silver Pheasant(Lophura nycthemera) are two sympatric bird species at Dazhong Mountain of Yunnan Province,southwestern China.We investigated characteristics of roosting habitats of the two pheasants from February to April,2004 in this area.Multiple statistics,Matryoshka and a habitat classification-tree were used to analyze the selection of roosting habitats of these pheasants. The results of the habitat classification-tree indicated that several separations occurred in their macro and micro roosting habitats in the study area. The two pheasants had similar crucial requirements for and selection of ecological roosting factors,which allow them to live in the same macrohabitat.Competition between these two pheasants was avoided by separation of spatial elements,such as roosting trees and topographic characteristics.For safety strategy,Hume's Pheasant adopted primarily a way of'uneasily found habitat cover plus easy escape',while the Silver Pheasant employed a unique way of'uneasily found habitat cover'.For tactics of keeping warm,Hume's Pheasant selected mainly a method of'suitable vegetation supplemented with suitable topography',while the Silver Pheasant chose a unique man-ner of'suitable vegetation'.

The Characteristics of Spatial Distribution of Saline-alkali Wasteland in Datong Basin, Northern China

[Objective] Saline-alkali wasteland is a kind of land use type that formed by soil salinization and secondary salinization. To study the causes of spatial distri- bution of saline-alkali wasteland could be used as reference for the amelioration and is significant for developing the reserved land with great potential. [Method] The re- search set a total of 1 729 sampling points in the study area of 34 433 hm2. Spa- tial analyses were used to find out the causes of saline-alkali wasteland in Datong basin from four factors： topography, geology, hydrology and soil. DEM and land use data were used to calculate distribution index of topography, and distribution of the total salinity （TS） and pH was analyzed by means of IDW interpolation. [Result] The results showed that saline-alkali wasteland was distributed on flat and low-lying ter- rains with poor drainage, which led to salt accumulation. 87% of saline-alkali wasteland was distributed on Quaternary Holocene alluvium whose performance of soil hydraulic conductivity was poor. TS value distribution was that in midstream re- gion was the highest, less in upstream region and the least in downstream region along the rivers, and TS value decreased when distance between saline-alkali wasteland and rivers increased. The major soil types in Datong basin were fluvo- aquic soil and saline soil. Both of the two soil types were of high TS value and pH value, and heavily salinized and strongly alkalized. [Conclusion] High groundwater table and the existence of two salt accumulation centers are the two causes of saline-alkali wasteland in Datong basin. The key to ameliorate saline-alkali waste- land is to descend the groundwater table and lessen salt accumulation.

Correlation Analysis of Gridding of Earthquakes in Datong and Its Surrounding Areas and Implication for Earthquake Prediction

On the basis of the earthquake （gL I〉3.0） catalog in North China from 1970 to 2009, the pattern of temporal and spatial distribution of medium-small earthquakes in Datong and its surrounding areas is studied by correlation analysis with a focus on its anomaly before moderate and strong earthquakes. With different spatial scales, temporal scales and time steps, the spatial distribution of earthquakes is converted to a sequence, then the correlation coefficients between the spatial distribution of medium-small earthquakes in a long-term and a longer time are calculated for the analysis of anomalies before moderate and strong earthquakes. In the study region center on the epicenter of the 1989 Datong- Yanggao earthquake （Ms5. 9） within a radius of less than 0.8~, with the time length of 3600 days, the longer time length of 3700 days, and the time step of 100 days, the correlation coefficient from 1980 to 2009 is steady between 0.94 and 1.00, but there were anomalies with values less than 0. 94 in the 2 years before the 1989 Datong-Yanggao earthquake （Ms 5.9）, the 1991 Datong earthquake （ Ms 5.8） and 1999 Hunyuan earthquake （Ms 5. 6 ）, which indicates the spatial distribution of a medium-small earthquake is very different from steady background seismicity. The implication for earthquake prediction from the anomaly of the correlation coefficient is also discussed with the three conclusions： （1） Before moderate and strong earthquakes in Datong and its surrounding areas, the obvious change of spatial distribution patterns of medium-small earthquake can be a kind of seismic precursor of the 2-year time scale for the prediction of an earthquake＇s time. （2） As the study region is restricted within a radius of less than 0. 8~, the result of correlation analysis is also good for the prediction of an earthquake＇s location. （3） The method of correlation analysis in this paper helps recognize the anomaly of spatial distribution of medium-small earthquake.

Energetic electron flux distribution model in the inner and middle magnetosphere

Based on the magnetospheric kinetic theory, a model is developed to specify the flux of energetic electrons in the inner and middle magnetosphere. Under the assumption of adiabatic motion and isotropic particle distribution maintained by pitch-angle scattering, the model calculates the electron flux by following bounce-averaged electric field, gradient, and curvature drift in the time dependent electric and magnetic field, meanwhile it counts the electron loss caused by pitch angle scattering. Using the model, the clectron flux distribution during a magnetic storm was calculated and compared with the observation data from the geosynchronous orbit. It is shown that the model can successfully reproduce most of the major electron flux enhancements observed at the geosynchronous orbit and generally tracks the satellite data well. The rms errors of the modeled logarithm of flux are between 0.5-1.0.

Distribution of stable carbon isotope in coalbed methane from the east margin of Ordos Basin

The commercial recovery of methane from coal is well established in the coalbed methane(CBM) blocks at the east margin of Ordos Basin, China. CBM forms with various carbon isotopic ratios(δ13CPDB) due to the carbon isotopic fractionation in biogenical or thermogenical processes. Based on the geologic evolution of coalbed reservoir and studies on the characteristics of δ13 CPDB values distributed spatially(e.g., horizontal CBM well location area, vertical coal burial zone, coal rank, etc.) and temporally(e.g., geologic evolution history), we explored the formation mechanism of carbon isotopic of methane. The relatively low δ13 CPDB values are widely distributed along the research area, indicating a trend of "lighter-heavier-lighter" from north to south. From a combination analysis of the relationship between δ13 CPDB and the relative effects, the essential aspects in determining CBM carbon isotope being light in the study area are: the genesis of secondary biogas in the north; water soluble effects in the active hydrodynamic areas in the middle; desorption fractionation effect promoted by tectonic evolution in the south; and the sudden warming hydrocarbon fractionation accelerated by magmatic event in particular areas(e.g., Linxian).