Soil warming effect on net ecosystem exchange of carbon dioxide during the transition from winter carbon source to spring carbon sink in a temperate urban lawn

The significant warming in urban environment caused by the combined effects of global warming and heat island has stimulated widely development of urban vegetations. However, it is less known of the climate feedback of urban lawn in warmed environment. Soil warming effect on net ecosystem exchange (NEE) of carbon dioxide during the transition period from winter to spring was investigated in a temperate urban lawn in Beijing, China. The NEE (negative for uptake) under soil warming treatment (temperature was about 5℃ higher than the ambient treatment as a control) was -0.71 μmol/(m².sec), the ecosytem was a CO₂ sink under soil warming treatment, the lawn ecosystem under the control was a CO₂ source (0.13 μmol/(m².sec)), indicating that the lawn ecosystem would provide a negative feedback to global warming. There was no significant effect of soil warming on nocturnal NEE (i.e., ecosystem respiration), although the soil temperature sensitivity (Q₁₀) of ecosystem respiration under soil warming treatment was 3.86, much lower than that in the control (7.03). The CO₂ uptake was significantly increased by soil warming treatment that was attributed to about 100% increase of α (apparent quantum yield) and A_max (maximum rate of photosynthesis). Our results indicated that the response of photosynthesis in urban lawn is much more sensitive to global warming than respiration in the transition period.     

人工曝气复氧整治污染河流

向受到严重有机污染的河流充入溶解氧可以有效消除水体的黑臭,改善水质和恢复生态平衡。文章总结了纯氧增氧系统、鼓风机———微孔布气管曝气系统、叶轮吸气推流式曝气器和水下射流曝气设备等多种使用于河道人工曝气复氧的技术;并列举大量国内外的相关工程实例说明这些技术在实践中的有效性。     

稳定碳同位素示踪农林生态转换系统中土壤有机质的含量变化

为了观察生态系统的转变对土壤有机质的影响,在贵州茂兰喀斯特原始森林保护区内农林生态系统发生转变的地域,分析了土壤有机质含量和土壤有机质的δ¹³C值森林点土壤有机碳含量普遍较高(1.81%～16.00%),而农田点土壤有机碳含量在0.43%～2.22%之间,表明毁林造田加速了土壤有机质的降解,使土壤有机质总量减少;利用C₃植物与C₄植物δ¹³C值的显著差异,对比森林点与农田点的δ¹³C值(森林点:-23.86‰～-27.12‰;农田点:-19.66‰～-23.26‰),计算表明,毁林造田同时也降低了土壤有机质中活性大的组分的比例,使土壤肥力下降.     

Are servant leaders appreciated? An investigation of how relational attributions influence employee feelings of gratitude and prosocial behaviors

Multisource data collected at three time phases were used in investigating when servant leadership elicits gratitude and then promotes prosocial behaviors. We tested a moderated mediation model, contending that relational attributions moderate the relationship between servant leadership and gratitude, and then gratitude sequentially predicts interpersonal citizenship behaviors and upward voice. As hypothesized, when employees do not highly rely on relational attributions for servant leadership, they feel more gratitude and subsequently engage in more interpersonal citizenship behaviors and upward voice than the employees who rely on relational attributions to explain their interactions with the leader. The sequential indirect effect from servant leadership to upward voice via gratitude and then interpersonal citizenship behaviors was significant when relational attributions are low rather than high.     

Interactive effects of natural and human disturbances on vegetation dynamics across landscapes.

Accurate measures of human effects on landscape processes require consideration of both the direct impacts from human activities and the indirect consequences of the interactions between humans and the landscape. This is particularly evident in systems experiencing regular natural disturbances such as in the mountainous areas of southwestern China, where the remaining population of giant pandas (Ailuropoda melanoleuca) is supported. Here the spatiotemporal patterns of human impacts, forests, and bamboo episodic die-offs combine to determine the distribution of panda habitat. To study the complex interactions of humans and landscapes, we developed an integrated spatiotemporally explicit model of household activities, natural vegetation dynamics, and their impacts on panda habitat. Using this model we examined the direct consequences of local fuelwood collection and household creation on areas of critical giant panda habitat and the indirect impacts when coupled with vegetation dynamics. Through simulations, we found that over the next 30 years household impacts would result in the loss of up to 30% of the habitat relied on by pandas during past bamboo die-offs. The accumulation and spatial distribution of household impacts would also have a considerable indirect influence on the spatial distribution of understory bamboo. While human impacts influence both bamboo die-off and regeneration, over 19% of pre-existing low-elevation bamboo habitat may be lost following an episodic die-off depending on the severity of the impacts and timing of the die-offs. Our study showed not only the importance of the spatial distribution of direct household impacts on habitat, but also the far-reaching effects of the indirect interactions between humans and the landscapes they are modifying.     

兔子宫内膜蛋白等电聚焦电泳柱状胶与板状胶电泳效果的比较

哺乳动物早期胚胎发育过程中，胚泡附植的成功与否对早期胚胎的发育十分重要．为了有效地弄清胚泡附植的分子机制，本研究从分析蛋白质的一种生化技术-等电聚焦电泳着手，利用兔子宫内膜蛋白作为实验材料，探讨了柱状胶与板状胶等电聚焦电泳分离蛋白质的电泳效果．研究结果表明：在相同情况下，柱状胶与板状胶的蛋白质分布有一些差别，pH梯度分布也不一致；板状胶比柱状胶pH值分布宽、蛋白质谱带多、分辨率高；板状胶酸性端只有1—2cm没有蛋白带、蛋白带分布比较均匀且压得比较紧．这说明在用子宫内膜作为实验材料进行电泳时用板状胶进行电泳的结果较好．     

几种萃取剂对土壤中重金属生物有效部分的萃取效果

采用6种萃取剂:pH=7的0.01mol/L CaCl_2、pH=7.3的0.005mol/L DTPA+0.1mol/L TEA(三乙醇胺)+0.01mol/L CaCl_2O.1mol/L NaNO_3、0.43mol/L HOAc、pH=7的0.05mol/L EDTA和pH=4.65的0.5mol/L NH_4OAc+0.02mol/L EDTA浸取液.对污染土壤中的重金属Cu、Zn、Cd、Pb、的进行了萃取,并比较了萃取剂的萃取能力。实验结果表明,HOAc、EDTA以及NH_4OAc-EDTA萃取各种重金属的能力远远大于其它几种萃取剂的萃取能力,是比较理想的萃取剂。     

铁屑微电解-共沉淀法处理屠宰场废水的研究

利用铁屑微电解-共沉淀法处理屠宰场废水,介绍其作用机理,考察了废水pH值、铁屑用量、反应时间、曝气时间和操作方式等因素对色度和CODCr去除率的影响.结果表明,在废水pH值为4,铁屑用量为15%,常温反应4 h,曝气时间2 h条件下,色度去除率可达100%,CODCr去除率达92.68%.     

海岛污水处理厂中水回用环境可行性分析—以平潭金井湾污水处理厂为例

基于污水处理厂的特点和区域的规划资料,本研究利用经验系数法、湖泊完全混合衰减方程和二维扩散方程解析解近似方程等方法,分析了平潭金井湾污水处理厂中水回用环境可行性。中水水量和水质可满足湖泊景观用水、冲厕用水、绿化用水、道路洒水等用途; 中水排入湖泊后可以满足相邻海域的环境功能区水质要求。在事故性排放情况下,湖泊出海口处的有小面积水域的水质超过了海域功能区的水质要求,应采取相应措施加强管理,防范事故性排放; 随着城市化的推进和工业的发展,中水用途将更趋于多样化。     

水库温室气体排放及其影响因素

水库是温室气体的一个重要排放源.探讨水库温室气体排放及其影响因素有利于精确估算水库温室气体排放量、减少水利工程与水电开发过程中水库温室气体排放.本文阐述r水库中温室气体的产生机制.总结了水库温室气体的3个排放途径:水库自然排放、水轮机和溢洪道、大坝下游河流,从水库特征、气候、水体pH值、水库中植被状况等角度深入探讨了水库温室气体排放的影响因素.最后,重点分析了水库温室气体排放的空间异质性以及研究结果不确定性的产生根源,并对今后的研究重点进行了展望.