Photosynthesis-transpiration coupling model at canopy scale in terrestrial ecosystem

At the hypothesis of big leaf, an ecosystem photosynthesis-transpiration coupling cycle model was established by the scaled SMPT-SB model from single leaf to canopy, and model parameterization methods were discussed. Through simulating the canopy light distribution, canopy internal conductance to CO2 can be scaled from single leaf to canopy by integrating to canopy using the relationship between single internal conductance and photosynthetic photon flux density. Using the data observed by eddy covariance method from the Changbai Mountains site of ChinaFLUX, the application of the model at the canopy scale was examined. Under no water stress, the simulated net ecosystem photosynthesis rate fitted with the observed data very well, the slope and R2 of the line regression equation of the observed and simulated values were 0.7977 and 0.8892, respectively (n = 752), and average absolute error was 3.78 μmol CO2 m-2s-1; the slope, R2 and average absolute error of transpiration rate were 0.7314, 0.4355 and 1.60mmol H2O m-2 s-1, respectively (n = 752). The relationship between canopy photosynthesis,transpiration and external environmental conditions was discussed by treating the canopy as a whole and neglecting the comprehensive feedback mechanism within canopy, and it was noted that the precipitation course affected the transpiration rate simulation badly. Compared to the models based on eco-physiological processes, the SMPT-SB model was simple and easy to be used. And it can be used as a basic carbon and water coupling model of soil-plant-atmosphere continuum.     

Seasonal variation of carbon exchange of typical forest ecosystems along the eastern forest transect in China

The long-term and continuous carbon fluxes of Changbaishan temperate mixed forest (CBS), Qianyanzhou subtropical evergreen coniferous forest (QYZ), Dinghushan subtropical evergreen mixed forest (DHS) and Xishuangbana tropical rainforest (XSBN) have been measured with eddy covariance techniques. In 2003, different responses of carbon exchange to the environment appeared across the four ecosystems. At CBS, the carbon exchange was mainly determined by radiation and temperature. 0°C and 10°C were two important temperature thresholds; the former determined the length of the growing season and the latter affected the magnitude of carbon exchange. The maximum net ecosystem exchange (N _EE) of CBS occurred in early summer because maximum ecosystem photosynthesis (G _PP) occurred earlier than maximum ecosystem respiration (R _e). During summer, QYZ experienced severe drought and N _EE decreased significantly mainly as a result of the depression of G _PP. At DHS and XSBN, N _EE was higher in the drought season than the wet season, especially the conversion between carbon sink and source occurring during the transition season at XSBN. During the wet season, increased fog and humid weather resulted from the plentiful rainfall, the ecosystem G _PP was dispressed. The Q ₁₀ and annual respiration of XSBN were the highest among the four ecosystems, while the average daily respiration of CBS during the growing season was the highest. Annual N _EE of CBS, QYZ, DHS and XSBN were 181.5, 360.9, 536.2 and ?320.0 g·C·m^?2·a^?1, respectively. From CBS to DHS, the temperature and precipitation increased with the decrease in latitude. The ratio of N _EE/R _e increased with latitude, while R _e/G _PP, ecosystem light use efficiency (L _UE), precipitation use efficiency and average daily G _PP decreased gradually. However, XSBN usually escaped such latitude trend probably because of the influence of the south-west monsoon climate which does not affect the other ecosystems. Long-term measurement and more research were necessary to understand the adaptation of forest ecosystems to climate change and to evaluate the ecosystem carbon balance due to the complexity of structure and function of forest ecosystems.     

构造、气候与砾岩* ——以积石山和临夏盆地为例

探讨构造、气候与砾岩的关系对于研究青藏高原隆升的时间和方式具有重要意义。裂变径迹热年代学表明积石山地区于8MaB.P.开始构造变形,与碎屑颗粒裂变径迹结果和生长地层结果一致,而明显早于积石砾岩出现的时间(3.6MaB.P.)。通过区分岩体隆升与地面隆升之间的差别,文章提出一种新的模型,以解释隆升、气候和砾岩之间的关系。积石山岩体于8MaB.P.开始隆升,隆升初期,尽管岩体隆升1500~2000m,但是由于积石山上覆的新生代地层易于剥蚀,在花岗岩基底被剥露到地表之前,地表只有少量隆升或没有隆升。随着沉积地层被剥蚀殆尽,基岩暴露于地表,地面隆升速率加快。约3.6MaB.P.,积石山隆升约200~900m,造成了地形雨和发源于积石山的横向河流的出现,这些横向河流把积石山的花岗岩搬运到盆地中沉积下来,形成积石砾岩。     

内蒙古狼山-色尔腾山的剥蚀面序列 和景观发育的控制因素*

利用与现今地面有关的数字地形资料,确定了内蒙古河套裂谷带北翼狼山-色尔腾山的剥蚀面序列及其分布型式。始新世末期始发的裂谷作用导致该裂谷北翼在渐新世(E₃)、中新世(N₁)、上新世(N₂)和第四纪(Q)发生了4幕区域性地面隆起和剥蚀作用,与裂谷盆地的4幕沉降和沉积作用相关联。区域性地面降起量和剥蚀作用的时间长度、流水侵蚀对局部地势的潜在影响、隆起和侵蚀速度的相对重要性,以及构造、侵蚀和均衡作用的联合效应是该裂谷翼部景观发育的主要控制因素。     

四川则木河断裂带微断层地貌的地形测量和走滑速率的估算(英文)

则木河断裂带南北分别与安宁河断裂带和小江断裂带相接,自中更新世复活以来,以左旋走滑为主,并成为一条重要的地震断层。据TL和ESR 测年分析,则木河谷地广泛存在的最低一级冲积扇为10 000 ～15 000 年以来形成。切割这些冲积扇的冲沟被则木河断裂带错断,其发生时间与冲积扇相当或者更新,平均位移值测量为86m 。据此计算,则木河断裂带晚更新世以来的平均走滑速率为5-8 ～8-6m m/a     

甘孜-玉树断裂带晚第四纪走滑速率与滑动分解作用

滑动速率是研究断裂运动学特征、地震活动性和区域应变分配的重要参数和依据。前人关于甘孜-玉树断裂带滑动速率的研究结果存在较大差异,因此,其晚第四纪滑动速率有待进一步调查研究。本文基于卫星影像解译和野外实地考察,对甘孜-玉树断裂带西段（玉树断裂）上典型断错地貌点进行测量分析,得到玉树断裂晚第四纪走滑速率为6.6±0.1-7.4±1.2mm/a。通过与前人对甘孜-玉树断裂带东段（甘孜断裂）滑动速率的研究结果进行对比,发现甘孜-玉树断裂带东、西段滑动速率不一致,其原因是甘孜断裂的左旋滑移在向西传递的过程中,一部分应变被分配到了巴塘盆地南缘断裂上。巴塘盆地南缘断裂的存在很好地解释了玉树断裂的走滑速率比甘孜断裂偏低的原因。但是,从区域变形来看,巴塘盆地南缘断裂分配的滑动速率恰好说明了甘孜-玉树断裂带东、西段及鲜水河断裂带的水平构造变形是协调一致的。     

水分胁迫/复水对谷子光合特性及产量影响

以谷子品种大金苗为研究对象,采用遮雨棚控水的大田试验方法,比较孕穗开花期和灌浆期水分胁迫/复水对叶片光合特性及产量影响,分析光合速率的限制因素,阐述光合速率、水分利用效率与产量的协同关系。结果表明：水分胁迫会导致谷子光合速率和产量下降,水分利用效率提高,随胁迫增强和持续时间延长,光合速率和产量下降幅度增大;水分胁迫后复水后,光合性能有所恢复,光合作用可产生补偿效应,水分胁迫越强和持续时间越长,补偿效应越低;轻度和持续时间短的水分胁迫,光合速率降低主要由气孔因素决定,随胁迫增强和持续时间延长,非气孔限制逐渐成为光合速率下降的主要原因;与孕穗开花期相比较,灌浆期水分胁迫对光合速率的影响更大且复水后光合性能恢复能力更低,光合速率与产量的协同关系更明显,产量对灌浆期水分胁迫更敏感。     

珠江三角洲五桂山南麓断裂第四纪活动新知

野外工作期间 ,在珠江三角洲五桂山南麓发现两个切割第四系的断层剖面。这是首次在珠江三角洲地区见到的断裂第四纪活动的直接地质证据。对两个剖面作了详细介绍 ,并通过三角洲第四系的分析和对比 ,确认五桂山南麓断裂在中、晚更新世时期是活动的     

Net water vapour exchange over a mixed needle and broad-leaved forest in Changbai Mountain during autumn

Water vapour and CO2 fluxes were measured by the eddy-covariance technique above a mixed needle and broad-leaved forest with affiliated meteorological measurements in Changbai Mountain as part of China's FLUX projects since late August in 2002. Net water vapour exchange and environmental control over the forest were examined from September 1 to October 31 in 2002. To quantify the seasonal dynamics, the transition period was separated into leafed, leaf falling and leafless stages according to the development of leaf area. The results showed that (a) seasonal variation of water vapour exchange was mainly controlled by net radiation (Rn) which could account for 78.5%, 63.4% and 56.6% for leafed, leaf falling and leafless stages, respectively, while other environmental factors' effects varied evidently; (b) magnitude of water vapour flux decreased remarkably during autumn and daily mean of water vapour exchange was 24.2 mg m-2 s-1 (100%), 14.8 mg m-2 s-1 (61.2%) and 10.3 mg m-2 s-1 (42.6%) for leafed, leaf falling and leafless stage, respectively; and (c) the budget of water vapour exchange during autumn was estimated to be 87.1 kg H2O m-2, with a mean of 1427.2 g H2O d-1 varying markedly from 3104.0 to 227.5 g H2O m-2 d-1.     

吉林省松原地区1119年6 3／4级地震的发震构造条件

１９９９年６ ３／４级地震是东北地区震级在的地震,目前对其发震构造背景缺乏深入的研究。本文从深部构造背景,浅层构造条件和深浅部构造关系等方面,对１１１９年地震的发震构造背景作了剖析。研究认为,本次地震的宏观震中位于扶余－前郭一带,地质构造上,该区处于松辽盆地中央凹陷和东南隆起的交接部位;深部构造背景上,该区是莫霍面起伏的拐点,存在北东向基底断鲜明和弱西向深部断裂,前者规模较大,晚新生代有弱活动,是