Does bicarbonate affect the nitrate utilization and photosynthesis of <Emphasis Type="Italic">Orychophragmus violaceus</Emphasis>?

The effect of bicarbonate (HCO₃^?) on the growth and development of plants varies by species. To better understand inorganic carbon and nitrogen assimilation changes of karst-adaptable plants under different HCO₃^? treatments, we conducted experiments on seedlings and in vitro plantlets of Orychophragmus violaceus (Ov). We found that the vital photosynthesis potential (as measured by net photosynthetic rate, actual photochemical efficiency of photosystem-II, photochemical quenching coefficient, and the instantaneous carbon isotope ratio of 3-phosphoglycerate) was consistent under different HCO₃^? treatments of Ov. Bicarbonate’s lack of effect on carbon assimilation of Ov may be related to carbonic anhydrase in Ov converting HCO₃^? to H₂O and CO₂. In this way, Ov could prevent HCO₃^? ion toxicity and high pH from harming its growth and development under HCO₃^? stress. This study also found that high HCO₃^? concentrations could promote nitrogen assimilation and utilization of Ov through changes in related indexes (foliar nitrogen isotope fractionation ratio, stable nitrogen isotope assimilation ratio, foliar stable nitrogen isotope fractionation, nitrate nitrogen utilization efficiency, and nitrate utilization share) under different HCO₃^? treatments. Bicarbonate has different effects on photosynthesis and on inorganic nitrogen assimilation of Ov, which may be connected to photosynthesis providing electrons for nitrate/nitrite reduction through the photosynthetic chain.     

天水市秦州区白家堡子滑坡特征与治理措施探析

以天水市秦州区白家堡子滑坡为研究对象,利用已有资料和野外实地勘察对其发育特征和物质组成进行系统的分析。明确了白家堡子滑坡属牵引式中厚层黄土—泥岩滑坡,滑体主要组成物质是黄土及部分全—强风化泥岩堆积层,滑体分上下两层滑面,滑面位于黄土—泥岩交界面或泥岩中,滑体缺少约束条件,较易变形失稳,长期处于活动状态。最后,根据白家堡子滑坡的特征,结合该区域的城市详细建设规划,初步提出白家堡子滑坡治理措施,为后期相邻滑坡的治理提供参考。     

Derivation of soil water retention curve incorporating electrochemical effects

Water retention of clayey soils with wide particle size distributions involves a combination of capillary and adsorbed layers effects that result into suction–saturation relations spanning over multiple decades of matric suction values. The present study provides a physics-based analysis to reproduce the water retention curve of such soils based solely on particle size distribution and porosity. The distribution of inter-particle pore sizes is inferred through a probabilistic treatment of the particle size distribution, which is then used, together with an assigned pore entry pressure, to estimate the inter-particle water volume at a given suction. The contribution to water content from adsorbed layers is also taken into account by considering the balance of electrochemical forces between water and clay material. The total water content is therefore found by summing up the contribution of inter-particle water, as well as adsorbed layers that form around clay particles and around the individual clay platelets. Comparisons with experimental results on nine different soil samples verify the capability of the model in accurately predicting the wide water retention curves without any prior calibration. Additional to capturing the essential features of the water retention curve with remarkable detail, the analytical model also provides insights into the relative contributions of capillary and adsorbed waters to the overall saturation at different suction regimes. Being based upon easily accessible information such as particle size distribution and void ratio, the model can therefore be considered as a substitute for costly and lengthy laboratory and in situ measurements of water retention curve.

     

The 2007 Fox Creek landslide,Peace River Lowland,Alberta, Canada

Fox Creek is a small tributary of the Saddle River, a tributary of the Peace River in northwestern Alberta. It has several dormant landslides with degraded scarps and grabens. A new, reactivated landslide on the north bank of the Fox Creek occurred on 5 May 2007. The landslide formed two major sliding blocks. A rapid translational block slide, it mobilized 47 Mm³ of displaced materials, blocked the creek, and made a natural dam with a maximum height of 19 m at the tips of the displaced blocks. The rupture surfaces of the 2007 landslide were within the advance phase glaciolacustrine sediments. The residual friction angles are about 10° similar to those of the previous landslides in the Peace River Lowland. Precipitation and snow melt prior to the landslide are likely triggers of the 2007 Fox Creek landslide. The farmlands on the crest of the river valley and timber resources were impacted. The current landslide dam in Fox Creek does not have any evidence of seepage downstream; it may last for many years. Eventually, the creek will overtop and erode the dam. The same cycle of actions, landsliding, damming, and erosion will continue in the foreseeable future.     

山东伏期旱涝特征与大气环流异常

以山东75个观测站伏期降水资料(1959-2005年)分析得到山东伏期旱涝在演变趋势有其独特性;500 hPa高度场距平分析表明,在中高纬尤其是贝加尔湖地区大气环流的异常对山东伏期的严重旱涝和洪涝形成起着重要作用;500 hPa高度距平场的EOF分析进一步证明,山东上游蒙古地区的冷空气活动和副高的强度是500 hPa高度场上影响山东伏期旱涝的两个最主要因子.     

土壤水分胁迫对冬小麦旗叶光合特性的影响

以土壤水分适宜做对照(CK),轻度水分胁迫(50%～70%)、中度水分胁迫(小于50%)3种处理在河北固城可控式土壤水分试验场,选择冬小麦灌浆初期的晴朗天气,采用Li-Cor 6400便携式光合作用仪,观测了3种处理的冬小麦旗叶光合作用参数的日变化。试验结果表明:土壤水分适宜时冬小麦旗叶净光合速率的日变化为"单峰型",未出现明显的"午休"现象,水分胁迫的处理都呈"双峰型",中度胁迫反而比轻度胁迫光合"午休"要短2h;3种处理的蒸腾速率日变化都呈"双峰型",气孔导度是反映叶片气体交换的重要指标,蒸腾速率与气孔导度成极显著正相关;土壤水分适宜或土壤干旱时冬小麦旗叶对环境变化的应变性较迟钝;轻度水分胁迫时冬小麦旗叶净光合速率比CK高2.8%～9.0%,蒸腾速率与CK基本相近,水分利用效率(WUE)比CK高10.6%～12.9%,这可能是一定程度的水分胁迫下冬小麦节水增产的生理调节机理。     

坡面植被对坡面径流和入渗的影响

通过人工模拟降雨和自然降雨试验,本文讨论了植被对雨水的截留和分流作用,以及坡面植被对水流入渗的影响。     

Distribution of convection associated with tropical cyclones making landfall along the South China coast

Summary This study examines the convection distribution associated with 18 TCs that made landfall along the South China coast during 1995 and 2005. Cloud-top temperatures from high-resolution satellite imageries of the Geosynchronous Meteorological Satellite 5 are used as proxy of strong convection. It is found that convection tends to be enhanced on the western side of the TC as it makes landfall in 10 of the cases, in agreement with the conclusion of some previous studies. Four cases have stronger convection on the eastern side. This “deviation” from the general rule appears to be related to the TCs being more slow-moving or their interaction of the TC with another land surface prior to its making landfall along the South China coast. For the remaining cases in which no significant asymmetries in convection can be identified, the vertical wind shear appears to enhance convection on the east side.     

临沂市紫外线辐射变化特征分析

利用临沂市2004年7月至2005年6月逐日紫外线观测资料,分析太阳紫外线辐射强度指数和等级的年、季、月和日变化特征。指出临沂市日紫外线最大辐射强度为4级的日数为多数,即紫外线辐射指数为7~9的日数占52%,4级以上紫外线辐射主要出现在春夏季节,冬季紫外线辐射较弱,出现4级辐射日数很少且无5级辐射。晴空条件下,冬季太阳紫外线辐射强度日变幅明显小于其他季节,夏季日最大辐射强度出现在12-14时,较其他季节的日最大辐射强度出现时段滞后1小时。