Temporal and spatial variation in soil respiration of poplar plantations at different developmental stages in Xinjiang, China

Soil respiration is essential for the understanding of carbon sequestration of forest plantations. Soil respiration of poplar plantations at three developmental stages was investigated in 2007 and 2008. The results showed that mean soil respiration rate was 5.74, 5.10 and 4.71 μmol CO₂ m⁻² s⁻¹ for stands of 2-, 7- and 12-year-old, respectively, during the growing season. Soil temperature decreased with increasing plantation age and canopy cover. As plantation matured, fine root biomass also declined. Multiple regression analysis suggested that soil temperature in the upper layer could explain 73-77% of the variation in soil respiration and fine root biomass in the upper layer could explain further 5-8%. The seasonal dynamics of soil respiration was mainly controlled by soil temperature rhythm and fine root growth since soil water availability remained adequate due to monthly irrigation. Spatial variability of soil respiration varied considerably among three age classes, with the coefficient of variation of 28.8%, 22.4% and 19.6% for stands of 2-, 7- and 12-year-old, respectively. The results highlight the importance of the development stage in soil carbon budget over a rotation, since both temporal and spatial variation in soil respiration displayed significant differences at different developmental stages.     

Modelling to analyse the impacts of animal treading effects on soil infiltration

Animal treading can change soil physical properties, and thus is an important factor in hydrological modelling. We investigated the impacts of animal treading on infiltration by using a series of rainfall simulation experiments at Whatawhata Research Center, Waikato, New Zealand. The study identified significant variables for estimating soil steady‐state infiltration at a micro‐site (0·5 m²) and fitted the Green and Ampt equation by modifying or including variables for soil and water parameters and animal activities on grazing paddocks. A regression function for estimating steady‐state infiltration rate was created for each of four scenarios: between tracks (inter‐track), track, easy slope with ash soil, and easy slope with clay soil. Significant variables included the number of days after treading, antecedent soil moisture, field capacity, percentage of bare ground, bulk density, and the high degree of soil damage (damage not compacted). Regression models explained more than 71% of the variance in steady‐state infiltration for three scenarios, but only 53% for the easy slope with clay soil. The remodified Green and Ampt equation provided satisfactory estimation of infiltration for all scenarios (accuracy > 80%), and thus enables us to use the modified model for Waikato hill country pastures of different topography, soil physical condition, season and grazing management. Copyright © 2006 John Wiley & Sons, Ltd.     

GPS9800在济南市长清地形控制网中的应用

在济南市长清区经济开发区地形测量控制网设计中应用了SOUTHGPS9800及其数据处理软件。工作中采用GPS观测技术精确测定点位的三维坐标,求定其大地高程,通过四等水准求得该点的正常高程,从而确定该点的高程异常值,布设足够多的GPS水准点,通过求得的高程异常值确定控制点的正常高程,精度符合要求。     

Marine Yeasts and Their Applications in Mariculture

1Introduction Becauseyeastscanproducemanybioactivesubstan ces,suchasprotein,aminoacids,vitamin,polysac charide,fattyacid,phospholipid,polyamine,astax anthin,βcarotenoid,trehalose,glutathione,superox idedismutase,chitinase,amylase,phytase,protease,killert…     

Precession of the Orbital Plane of Binary Pulsars and Significant Variabilities

There are two ways of expressing the precession of orbital plane of a binary pulsar system, given by Barker & O'Connell, Apostolatos et al. and Kidder, respectively. We point out that these two ways actually come from the same Lagrangian under different degrees of freedom. Damour & Schafer and Wex & Kopeikin applied Barker & O'Connell's orbital precession velocity in pulsar timing measurement. This paper applies Apostolatos et al.'s and Kidder's orbital precession velocity. We show that Damour & Schafer's treatment corresponds to negligible Spin-Orbit induced precession of periastron, while Wex & Kopeikin and this paper both found significant (but not equivalent) effects. The observational data of two typical binary pulsars, PSR J2051-0827 and PSR J1713+0747, apparently support a significant Spin-Orbit coupling effect. Specific binary pulsars with orbital plane nearly edge on could discriminate between Wex & Kopeikin and this paper: if the orbital period derivative of the double-pulsar system PSRs J0737-3039 A and B, with orbital inclination angle i = 87.7129 deg, is much larger than that of the gravitational radiation induced one, then the expression in this paper is supported, otherwise Wex & Kopeikin's is supported.     

GPS水准高程拟合精度探讨

论述了应用GPS定位技术,求定地面点的正常高的方法,并对应用最广泛的GPS水准方法做了论述,找出了影响这种方法的主要原因并通过实例对如何提高精度作了详细的探讨。     

Ultrastructural observations on sporogenesis ofMyxobolus Kwangsiensis Hsieh,Gong & Xiao from the kidney of daceLabeo rohita

The early stages and capsulogenetic stages of sporogenesis ofMyxobolus kwangsiensis were studied in detail by electron microscopy.M. kwangsiensis is an intracellular myxosporean infecting the epithelial cells of kidney tubules of young daceLabeo rohita. TheM. kwangsiensis sporogensis presents the typical features of myxosporea. The initial stages are multinucleate primary cells, with one primary cell typically enclosing one secondary cell. The secondary cells are formed directly by cytokinesis inside the primary cells. The primary cell participates in the formation of the secondary cell nucleus. The nuclear division of primary cell is asynchronous by amitosis. The parasitic organisms may degenerate inside the epithelial cells at any stage. The modes of sporoblast formation, the typical features of myxosporea and the cause of its degradation are discussed. This research was supported by the NSFC. (No. 39070675)     

小秦岭金矿成因的新识

目前，对小秦岭金矿的成因有三种观点：岩浆热液、变质热液和大气降水热液，这三种观点均有许多难以解释的地质现象。这些矛盾的出现表明，可能有另种矿床成因的存在。笔者在此提出了由上地幔或下地壳物质向深断裂带排气液作用形成的＂深源热液＂新观点。该观点能很好地解决上述观点难以解决的地质问题。     

新疆、西藏地区地震的时间分布特征及其意义

近年米,笔者对全球、中国、中国大陆、华北、云南、四川、台湾以及日本等不同地区地震的时间分布进行了研究,提出地震的时间间隔△T与其出现频次N_△T之间存在两种分布关系,即:     

Active extension of the Shanxi rift,north China: does it result from anticlockwise block rotations?

The Shanxi rift is an intraplate extensional zone in the North China Block. Active extension has previously been considered to result from anticlockwise block rotation, with successive indentation of the Indian plate toward the Eurasian plate. However, GPS data show that the entire North China Block is moving coherently from WNW to ESE, indicating that no significant block rotations presently exist along the two sides of the rift. We use a viscoelastic model to predict that its active extension might be caused by intraplate deformation localization with lateral changes of the crustal rheological structures. A model result shows that for the ESE movement of the North China Block, the existing topographical loading and crustal weakness could have resulted in the obvious long‐term extension of the Shanxi rift even without different block rotations. The surface extension rate approximated from lateral inhomogeneous crustal models is ～ 0.5–1.4 mm yr^?1, consistent with observed geological and seismological extension rates.