暖温带山地森林生态系统水分问题研究

本文的研究是中国科学院院重大项目“暖温带森林生态系统结构、功能及生产力持续发展”的主要内容之一。作者以详实的第一手资料，从森林小气候及环境特征、森林降水的水文学效应及降水化学、森林的热量平衡及蒸发散、树木个体的水分生理生态学几个方面阐述、分析了暖温带山地森林生态系统主要林分的水分及其相关生态学问题。 在森林小气候及环境特征一章，作者从不同季节的日变化和生长季的月际变化两个视角，以落叶阔叶混交林和油松林为研究对象，考察了林冠上和林下四个不同梯度的风速、气温、湿度、地温的时空动态。 在森林降水的水文学效应和降水化学一章，笔者以1993、1994年试验年度的83次降雨观测资料为基础，分析了暖温带落叶阔叶混交林、辽东栎林、油松林、落叶松林、次生灌丛降水总量与各降水分量的关系，建立了单次降雨与各降雨分量的经验模型，并给出了生长季林冠作用层和林地作用层的水量分配的月际动态。在探讨上述水量关系的同时，作者还分析了前四类林分大气降水及各降水分量中N、K、Ca、S、Mg、P、Al七种元素的浓度及含量变化，就不同树种对上述元素的选择性交换作了探讨，比较了不同林分的降水化学效应差异。 在第四章，作者以落叶阔叶混交林和油松林为研究对象，分析了两类林分在94试验年度生长季辐射平衡、显热通量、潜热通量、蒸发散以及土壤热通量的季节变化和日变化特征。 在树木个体的水分生理生态部分，作者应用压力室一容积技术测定了暖温带落叶阔叶林、油松林和次生灌丛10种主要树种的水分生理指标：日最低水势值、最大膨压时的渗透势、膨压为零时的渗透势、初始质壁分离时渗透水的相对含量、初始质壁分离时的相对含水量、质外体水的相对含量、细胞最大弹性模量，并比较了不同树种间上述指标与抗旱性的关系。此外，作者还应用Li-1600稳态气孔计测定了上述林分中主要树种的日均蒸腾强度的季节动态，并比较了上下两面叶片蒸腾特性的差异。最后，作者采用九种水分生理指标对10种主要树种的抗旱性作了主分量分析，给出了综合性抗旱指标。 在第六章，作者应用热脉冲技术系统地研究了暖温带山地森林主要乔木树种的树干液流的时空变化特征，并应用时序分析方法对上述树种的树液流量变化建立了自回归模型，在此基础上提出了生理惯性指标，给予了生理学解释。

Isotopic signatures and mercury content of arctic char and their prey, and water chemistry of 18 arctic Canadian lakes

Concentrations of mercury (Hg) have increased slowly in landlocked Arctic char over a 10- to 15-year period in the Arctic. Fluxes of Hg to sediments also show increases in most Arctic lakes. Correlation of Hg with trophic level (TL) was used to investigate and compare biomagnification of Hg in food webs from lakes in the Canadian Arctic sampled from 2002 to 2007. Concentrations of Hg (total Hg and methylmercury [MeHg]) in food webs were compared across longitudinal and latitudinal gradients in relation to d13C and d15N in periphyton, zooplankton, benthic invertebrates, and Arctic char of varying size-classes. Trophic magnification factors (TMFs) were calculated for the food web in each lake and related to available physical and chemical characteristics of the lakes. The relative content of MeHg increased with trophic level from 4.3 to 12.2% in periphyton, 41 to 79% in zooplankton, 59 to 72% in insects, and 74 to 100% in juvenile and adult char. The d13C signatures of adult char indicated coupling with benthic invertebrates. Cannibalism among char lengthened the food chain. Biomagnification was confirmed in all 18 lakes, with TMFs ranging from 3.5 ± 1.1 to 64.3 ± 0.8. Results indicate that TMFs and food chain length (FCL) are key factors in explaining interlake variability in biomagnification of [Hg] among different lakes.

Evaluation by respirometry of the degradability of retort water using a shale ash and overburden packed column

Oil shale processing produces an aqueous wastewater stream known as retort water. The fate of the organic content of retort water from the Stuart oil shale project (Gladstone, Queensland) is examined in a proposed packed bed treatment system consisting of a 1:1 mixture of residual shale from the retorting process and mining overburden. The retort water had a neutral pH and an average unfiltered TOC of 2,900 mg l(-1). The inorganic composition of the retort water was dominated by NH4+. Only 40% of the total organic carbon (TOC) in the retort water was identifiable, and this was dominated by carboxylic acids. In addition to monitoring influent and effluent TOC concentrations, CO2 evolution was monitored on line by continuous measurements of headspace concentrations and air flow rates. The column was run for 64 days before it blocked and was dismantled for analysis. Over 98% of the TOC was removed from the retort water. Respirometry measurements were confounded by CO2 production from inorganic sources. Based on predictions with the chemical equilibrium package PHREEQE, approximately 15% of the total CO2 production arose from the reaction of NH4+ with carbonates. The balance of the CO2 production accounted for at least 80% of the carbon removed from the retort water. Direct measurements of solid organic carbon showed that approximately 20% of the influent carbon was held-up in the top 20cm of the column. Less than 20% of this held-up carbon was present as either biomass or as adsorbed species. Therefore, the column was ultimately blocked by either extracellular polymeric substances or by a sludge that had precipitated out of the retort water.

Clones de Eucalyptus sp. submetidos a estresse hídrico em dois tipos de solo

Pós-graduação em Agronomia (Irrigação e Drenagem) - FCA

Cation exchange capacity and water content of ODP sites from Nankai

Pore fluid chlorinity lower than seawater is often observed in accretionary wedges and one of the possible causes of pore water freshening is the smectite to illite reaction. This reaction occurs during diagenesis in the 80-150°C temperature range. Low chlorinity anomalies observed at the toe of accretionary wedges have thus been interpreted as evidence for lateral fluid migration from inner parts of the wedge and the seismogenic zone. However, temperature conditions in Nankai Trough are locally high enough for the smectite to illite transition to occur in situ. Cation exchange capacity is here used as a proxy for smectite content in the sediment and the amount of interlayer water released during the smectite to illite reaction represents in average 12 water molecules per cation charge. Water and chloride budget calculations show that there is enough smectite to explain the chlorinity anomalies by in situ reactions. The shape of the pore fluid chlorinity profiles can be explained if compaction is also taken into account in the model. Lateral flow is not needed. This argument, based solely on chloride concentration, does not imply that lateral flow is absent. However, previous estimations of lateral fluid fluxes, and of the duration of transient flow events along the de.collement, should be reconsidered.