三江平原小叶章湿地枯落物在不同水位梯度上的分解及硫素释放动态

利用分解袋法，研究了小叶章枯落物在不同水位梯度上的分解动态和硫素释放情况，结果表明：在450天的分解试验中，小叶章枯落物在不同水位梯度上具有相同的分解模式，均为快－慢交替变化的模式，干物质残留率沿着水位梯度从洼地边沿到中心呈逐渐减少的趋势，分解速率表现为逐渐增大，水分条件是影响小叶章枯落物分解的一个重要因素。在不同的水位梯度上枯落物中硫的浓度呈波动性变化，这种变化和干物质损失率呈线性相关，分解450天后，枯落物残体中总硫浓度沿着水位梯度从洼地边沿到中心依次为：0.588、0.508、0.404、0.359和0.306g.kg-1，均低于初始浓度，且沿着洼地边沿向中心依次降低。S的释放模式为淋溶－固持－释放，其中枯落物残体中C：S是决定其释放模式的主要因素，当C：S高于1620.34~2430.81时，外源硫被固持，当C：S低于805.17~1070.47时，枯落物中的硫被释放，但硫的固持量或释放量受水分条件的制约，沿着水位梯度由无积水到常年积水区即由小叶章湿草甸到漂筏苔草沼泽（由B到F点），硫的固持量依次增加，释放量逐渐减少。     

垃圾运输问题的模型及其求解

本文通过垃圾运输问题的模型建立与求解,总结出这类问题的一般性解法,即根据实际问题构造恰当的有向或无向赋权图,把问题转化成图论中的TSP问题,通过解决这类TSP问题,从而使原问题获得满意的解答.     

Examining youth perceptions and social contexts of litter to improve marine debris environmental education

Abstract

Youth have astute observations about site-specific personal and environmental factors that contribute to littering and marine debris, and they have a strong potential to act as change agents in communities. Interactions with youth in Pinellas County Florida add insights into a growing body of research on environmental education and marine debris prevention. This study assessed perceptions of marine debris and littering behaviors through group discussions with middle school and high school students (N = ～44), evaluations at summer camp programs (N = ～31) and pre- and post-assessments of environmental field trips (pre-assessment N = ～120; post-assessment N = ～140). Youth showed high initial awareness of the effects of marine debris on the environment but showed less understanding about the role of watersheds and biodegradation in marine litter issues. A majority of youth attributed others’ littering behavior to dispositional factors, like laziness, while attributing their own littering to situational factors, like poorly placed bins. Student observations of educators and parents also influenced littering behaviors and willingness to act. To reduce littering, education and outreach programs need to (1) provide opportunities for ongoing assessment of complex marine debris topics, (2) align visual and written or verbal messages, (3) reduce actor/observer bias related to littering behaviors, and (4) support adult role models.     

Australian Waste Wise Schools Program: Its Past,Present, and Future

The Waste Wise Schools program has a longstanding history in Australia. It is an action-based program that encourages schools to move toward zero waste through their curriculum and operating practices. This article provides a review of the program, finding that it has had notable success in reducing schools’ waste through a “reduce, reuse, and recycle” (or “three Rs”) approach. Since the program's conception, an evaluation process has continually occurred alongside the actual program. This report presents the most recent program evaluation results: a 2007 statewide survey that was administered to 1,015 primary (elementary) and secondary teachers. The article outlines the past, present, and future directions of the Waste Wise Schools program and, in doing so, discusses the broader implications for school-based environmental education programs. In particular and of most significance, the findings reveal a growing sustainability culture in Australian schools and communities.     

马尾松阔叶树混交林凋落物浅析

针阔混交林凋落物研究中,马×拉、马×青、马×闽、马×格、马×苦等混交群落,这5个群落以及马尾松纯林凋落物表层的化验分析结果,枯叶占优势,马×苦混交群落最高,马尾松纯林最低。营养分析A层的凋落物的N及Ca的含量最高,其平均值分别为:0.80%和1.26%,5种元素含量大小为:Ca>N>Mg或K>P。马×闽混交群落中Mg含量最小。     

Climate and litter C/N ratio constrain soil organic carbon accumulation

Soil organic carbon (SOC) plays critical roles in stabilizing atmospheric CO₂ concentration, but the mechanistic controls on the amount and distribution of SOC on global scales are not well understood. In turn, this has hampered the ability to model global C budgets and to find measures to mitigate climate change. Here, based on the data from a large field survey campaign with 2600 plots across China''s forest ecosystems and a global collection of published data from forested land, we find that a low litter carbon-to-nitrogen ratio (C/N) and high wetness index (P/PET, precipitation-to-potential-evapotranspiration ratio) are the two factors that promote SOC accumulation, with only minor contributions of litter quantity and soil texture. The field survey data demonstrated that high plant diversity decreased litter C/N and thus indirectly promoted SOC accumulation by increasing the litter quality. We conclude that any changes in plant-community composition, plant-species richness and environmental factors that can reduce the litter C/N ratio, or climatic changes that increase wetness index, may promote SOC accumulation. The study provides a guideline for modeling the carbon cycle of various ecosystem scales and formulates the principle for land-based actions for mitigating the rising atmospheric CO₂ concentration.     

海南岛中部丘陵地区受台风侵袭影响的4种植物群落凋落物动态

为探讨台风后凋落物组成和量的特征,在“达维”台风后的1a中,测定了海南岛中部丘陵地区次生植被草丛、灌丛、次生林及人工马占相思林的凋落物.结果显示：1）各植被年凋落物量与同类型植被正常年凋落物量相比,明显偏低;2）在台风后的第3个月起次生植被月凋落物量有逐渐回升趋势,人工马占相思林月凋落物量无明显回升趋势;3）各植被类型凋落物叶的比例,均低于同类型植被正常年份凋落物中叶的比例;4）4种植被凋落物凋落节律未因台风而发生明显变化,次生植被为“双峰”特征,人工马占相思林无明显的落叶季节.     

“小先生”与新课改

陶行知的“小先生”产生于二十世纪二十年代,它解决了穷国办教育下师资严重匮乏的大问题。文章介绍“小先生”的由来,“小先生”的内涵,论述的“小先生”形成的理论基础和历史基础,以及“小先生”对当今新课改师资建设的启示等问题。     

高空抛物中邻里要“连坐”之法律分析

《中华人民共和国侵权责任法》对高空抛物和高空坠物的行为第一次作出了明确规定,其中在第87条规定:"从建筑物中抛掷物品或者从建筑物上坠落的物品造成他人损害,难以确定具体侵权人的,除能够证明自己不是侵权人的外,由可能加害的建筑物使用人给予补偿。"此项规定被众多媒体引用,并都解读为"高空抛物邻里要连坐",这一论点引发众多争议,司法处理也引发着巨大的争议,因此,本文仍以"连坐"一词来对此行为作一深入分析。