气候变暖背景下森林土壤碳循环研究进展

由人类活动引起的温室效应以及由此造成的气候变暖对森林牛态系统的影响已引起人们的普遍关注.森林土壤碳循环作为全球碳循环的重要组成部分,是决定未来陆地牛物嘲表现为碳源/碳汇的关键环节,揭示这一作用对于准确理解全球变化背景下陆地生态系统碳循环过程具有重要的指导意义.本文主要通过论述影响土壤碳循环过程的5个方面(土壤呼吸、土壤微生物、土壤酶活性、凋落物输入与分解、土壤碳库),综述了近10 a来全球气候变暖对土壤碳循环过程的影响.近年来,尽管已开展了大量有关土壤碳循环对气候变暖的响应及反馈机制的研究,并取得了一定的成果,但研究结果仍然存在很大的不确定性.整合各种密切关联的全球变化现象,完善研究方法和实验手段,加强根际微生态系统碳循环过程与机理研究将是下一步研究的方向和重点.参70     

Social environment versus cycling competency predicting risk-taking in 11- to 13-year-old cyclists in The Netherlands

Abstract

Objectives: From age 12 onwards, cycling injuries begin rising in The Netherlands. A known contributing factor is younger children’s underdeveloped competency to deal with complex and hazardous traffic situations, and their exposure to such situations strongly increases after transitioning to secondary school. Little is known about intentional risk-taking as a contributing factor. In this developmental stage, children become increasingly vulnerable because of intentional risk-taking, affecting their safety and health. The incidence, predictors in the child’s social environment, and trends of such risks are systematically monitored; for instance, for alcohol use, smoking, and cyber bullying. Such monitors do not include risky road behavior. This exploratory field study examined the frequency of intentional risky cycling, its relationship with the perceived social environment, and relative to cycling competency measured as the ability to detect emerging hazards quickly.

Methods: Three hundred thirty-five students between 11 and 13 years of age (51% male) completed computerized tests of hazard perception skill and surveys on crashes, risk-taking, peer pressure, perceived risk-taking by parents or friends, and exposure to risky driving as passenger.

Results: Frequent risk-taking was associated with higher crash frequency. Stepwise regression confirmed that children who more often took risks on the road were also more sensitive to peer pressure, had more often been passengers of risky drivers, had parents and friends who exhibited risky behaviors in traffic more often, and perceived hazards as less dangerous but, in contrast to expectations, did not do worse on the detection of hazards. The predictors explained 28% of the variance in total risk-taking but varied from 6 to 20% depending on the specific risk-taking behavior concerned.

Conclusions: At least 20% of children sometimes or more often take risks in traffic. Children who feel peer pressure to behave in a risky manner, observe parents and friends behaving in a risky manner in traffic, and have been exposed as passengers to risky driving more often take risks in traffic themselves. These results provide support for including items on risky road behavior in health monitors and to design interventions that address the risk factors in the child’s perceived social environment.     

The littoral zone of lake okeechobee as a source of phosphorus after drawdown

Following a period of prolonged drought or intentional lake level drawdown, large littoral areas that once contained submersed aquatic vegetation (SAV) are reinundated when lake levels rise. A complete assessment of the contribution made by decomposing SAV to the in-lake phosphorus (P) concentration is important in both the management of Lake Okeechobee and understanding basic P processes. The P contribution to the open waters of Lake Okeechobee from a rapid inundation of exposed SAV was calculated by four methods: cores of field-desiccated SAV, cores of lab-desiccated SAV in the presence and absence of sediments, in situ decomposition, and sequential macrophyte harvesting. P releases, given such an episodic event, were similar among the four methods, ranging from 116±48 to 384±528 mg/m² in the absence of sediment. When SAV is in contact with sediment, which is the realistic field situation, the amount of P released was four times less (30±14 mg/m²) than in the absence of sediment. The calculated P releases would result in total P concentration increases in the lake from 2 to 15 μg/liter (upper 95% CI=2–25 μg/liter) in the absence of sediment; only 1 μg/liter increase was predicted when SAV released P in contact with sediment. Thus it is unlikely that a significant rise in total P concentrations in the limnetic zone of the lake would occur from the export of P released during the desiccation of SAV in the littoral-marsh zone during a drawdown.     

高效垂直流人工湿地在景观湖水循环净化中的应用--以天津东丽湖景观湖水循环净化工程为例

介绍了天津东丽湖景观湖水循环净化工程的工艺流程、运行工况,并对处理效果及景观湖水质进行了分析,对人工湿地系统及景观湖泊的管理和维护进行了总结.通过近1a的运行实践表明高效垂直流人工湿地系统作为一种生态水处理技术,对微污染地表水净化具有良好的实用价值和应用前景.     

农桐间作的养分循环

对农桐间作（以桐为主间作型）的养分循环规律进行了研究。结果表明，泡桐各器官营养元素的含量随季节而变化。对营养元素的年吸收量为４７１．９５９５ｋｇ／ｈｍ￣２，其中氮１５５．１４２９ｋｇ／ｈｍ￣２，磷８０．０８２１ｋｇ／ｈｍ￣２，钾８７．０３９４ｋｇ／ｈｍ￣２，钙１１９．４６０３ｋｇ／ｈｍ￣２，镁３０．２３４８ｋｇ／ｈｍ￣２。营养元素的年归还量为３３１．６１５５ｋｇ／ｈｍ￣２，其中氮１０２．５７２１ｋｇ／ｈｍ￣２，磷４３．２９２２ｋｇ／ｈｍ￣２．钾６３．６４９７ｋｇ／ｈｍ￣２，钙９７．３５８６ｋｇ／ｈｍ￣２，镁２４．７４２９ｋｇ／ｈｍ￣２。营养元素的循环率为７０、２６％，其中氮６６．１１％，磷５４．０６％，钾７３．１３％，钙８１．５０％，镁８１．８４％。     

桉树人工林生态系统养分循环和平衡研究Ⅱ. 桉树人工林生态系统的养分循环

根据大量的观测分析资料,论述了刚果W5桉树人工林生态系统养分的地球化学循环和生物小循环。研究结果表明,每公顷每年通过地表径流和地下渗漏从生态系统输出的养分质量以K最多,达21.25 kg/(hm2a);其次为N,达17.21 kg/(hm2a)。桉树人工林生态系统养分流通质量的净变化值f(K)、f(Ca)为负值,f(N)、f(P)、f(Mg)为正值;桉树人工林生态系统养分的生物小循环研究表明,在一个轮伐期内,每公顷桉树吸收养分的质量,依次为Ca 429.03 kg/hm2,其次为N 277.01 kg/hm2和K 208.12 kg/hm2。而在一个轮伐期中归还的养分质量,Ca只有99.78 kg/hm2,K为113.04 kg/hm2。在养分循环率方面,与热带半落叶季雨林比较,桉树人工林生态系统的养分循环率要小得多,说明桉树人工林土壤养分趋向于减少。     

Nitrogen and Phosphorus Cycling in Shrimp Ponds and the Measures for Sustainable Management

Six ponds of age 3 were selected 45 km north from Suzhou in the Tailake region, and research conducted on nitrogen and phosphorus cycling in P. vannanmei(Penaeus vannanme) ponds and M. nipponense(Macrobrachium nipponense) hatchery ponds under normal management. Two treatments each had three replications. The results confirmed that feed was the major path of nitrogen and phosphorus input, each accounted for 61.24%(193.81 kg ha^–1) and 81.08%(45.20 kg ha^–1) of the total nitrogen and phosphorus input for P. vannanme ponds; the values for M. nipponense ponds were 43.93%(86.31 kg ha^–1) and 57.67%(14.61 kg ha^–1), respectively. Water pumped into ponds contributed on average 83.57 kg ha^–1 nitrogen and 8.48 kg ha^–1 phosphorus for P. vannanmei ponds, and 87.48 kg ha^–1 nitrogen and 7.00 kg ha^–1 phosphorus for M. nipponense hatchery ponds. Shrimp harvest recovered 102.81 kg ha^–1 nitrogen (32.94% of the total nitrogen input) and 7.94 kg ha^–1phosphorus (14.23% of the total phosphorus input) for P. vannanme ponds; and 43.94 kg ha^–1 nitrogen and 4.46 kg ha^–1phosphorus for M. nipponense hatchery ponds. The sum of nitrogen losses through volatilization, denitrification and sedimentation was 173.62 and 122.39 kg ha^–1, 54.86% and 62.29% of the total nitrogen input for P. vannanme ponds and M. nipponense hatchery ponds, respectively. Sediment accumulated 41.46 and 14.63 kg ha^–1 phosphorus, 74.37% and 64.85% of the total phosphorus input for P. vannanm ponds and M. nipponense hatchery ponds. Draining and seeping caused 40.06 kg ha^–1 nitrogen (12.66% of total nitrogen input) and 6.36 kg ha^–1 phosphorus (11.40% of total phosphorus input) loss to the surrounding water from P. vannanme ponds in 114 days; 30.14 kg ha^–1nitrogen (15.34% of the total input) and 4.45 kg ha^–1 phosphorus (17.57% of the total input) to channel water from M. nipponense hatchery ponds in 87 days, respectively. Countermeasures for sustainable pond management include improving feeds and feeding, sediment treatments, machine aerating, chemicals with no pollution, and integrated fish-shrimp cultivation. Management of water resources for pond and methods to reduce nitrogen and phosphorus loading into surrounding water from drainage are elucidated.     

中国环境中氮循环的动态模式

对中国960万km~2范围内氮的生物地球化学循环作了初步探讨。该工作建立在对大气、土、生物及水圈界面氮的流通量的研究基础上,以数学方式模拟氮的生物地球化学循环规律,并预测各圈中氮的库存量和流通量的变化趋势。经过验证,模式的收敛性、稳定性及可信度均是好的。     

硫循环的酶促反应机制及湖泊环境效应

在湖泊沉积物表层存在着强烈的生物作用 ,使SO2 -4 转变成S2 -,然后和Fe2 + 结合而固定在沉积物中 ,这种SO2 -4 的清除机制具有重要的环境意义。本文论述了H2 S的产生和各种形态硫转变成SO2 -4 的酶促反应机制 ,并阐述了不同微生物电子传递载体、最终电子受体和电子进入传递链的部位的差异以及生成ATP的数目和环境效应的差异。