Recent human impact on vegetation in Takkobu, northern Japan, reconstructed from fossil pollen in lake sediments

The vegetation of Takkobu, northern Japan, has been significantly altered by land-use development following Japanese settlement at the end of the 19th century. In order to assess the impact of human activity on vegetation dynamics in Takkobu, changes in the vegetation composition over the last 300 years were reconstructed from fossil pollen in the sediments of Lake Takkobu. The pollen assemblage represented broadleaved forests on the surrounding hills and alder forests found on the margin of the wetland bordering the lake. Prior to Japanese settlement, the hillside forests consisted predominantly of oak. However, with the onset of land-use development, a significant decline in oak relative to increasing birch was apparent, particularly after the early 1960s. These results suggest that successive logging since the 1880s had gradually undermined the resilience of oak. An increase of Artemisia and birch pollen also indicates an expansion of disturbed land. Since the 1960s, a large part of the broadleaved forests in Takkobu has been converted to larch plantations, although this was not represented in the pollen data because of the underrepresentation of larch pollen. The results of the pollen analysis have implications for forest restoration in Takkobu. The use of long-term data allows the determination of the baseline (natural) vegetation to be restored, and also illustrates the factors affecting present-day vegetation and how it may change in the future.     

The role of ecology in the development of weed management systems: an outlook

This paper discusses the extent to which a knowledge of weed biology and ecology can contribute to the development of weed management strategies. To date, such contributions have been modest and have been constrained by a number of factors that are discussed in this review. In contrast to other pest management disciplines, devising integrated weed management strategies that address a diversity of weed species with a diversity of life history traits is difficult. Because of this diversity, robust systems that require ecological insight beyond that of individual species are needed. Although the contributions have been modest, research findings have helped to shape weed management strategies in a number of important ways. Approaches directed at weed population management have revealed important insights into population equilibria, density-dependent mortality and life stages particularly important in regulating population size. Eco-physiological research has helped to guide the development of biologically effective herbicide dosage strategies, whereas mechanistic interplant competition modelling coupled with empirical field studies have aided in the identification of weed-suppressive crop phenotypes. Finally, much has been learned about the influence of control tactics and agronomic measures on the evolution of herbicide resistance and the development of integrated weed management strategies to address it. In this paper, examples are reviewed where research in ecology and biology has helped to shape the practice of integrated weed management. More importantly, characteristics of such research programmes are identified so that future efforts in the discipline will have a context in which the relevance of research questions and approaches can be considered.     

Acetic acid pulping of wheat straw under atmospheric pressure

Atmospheric acetic acid pulping of wheat straw was carried out. Pulping conditions and their effects on pulp properties were investigated in detail, and a comparison between acetic acid (AcOH) pulp and soda-anthraquinone (AQ) pulps of wheat straw was made of the chemical composition, strength, and fiber morphology of the pulps. Wheat straw was successfully pulped and fractionated into pulp (cellulose), acetic acid lignin, and sugars (monosaccharides from hemicellulose), making it easy to utilize them. It was found that among the pulping conditions the dosage of H₂SO₄ as catalyst was the most notable, and the extent and rate of delignification could be controlled by varying the amount of the catalyst. The results also showed that acetic acid pulp was quite different from soda-AQ pulp. About 70% of the ash or 90% of the silica in wheat straw were kept in AcOH pulp. The ash might function as filler and be beneficial to the printability of paper. It was known that many epidermal cells existed in AcOH pulp in bundles or in single cells. These ash-rich nonfiber cells seemed to hinder the bonding between fibers. AcOH pulp had lower strength than soda-AQ pulp, which might result mainly from the chemical damage of fibers caused by acid, not from the depolymerization of cellulose.Part of this paper was presented at the 65th Pulp and Paper Research Conference of Japan TAPPI, Tokyo, June 1998     

植物提取物对赤拟谷盗种群抑制作用的研究

选用七种植物提取物,分别设置800ppm、400ppm、200ppm、100ppm、50ppm五个浓度梯度,对赤拟谷盗进行试验。结果表明,对主谷盗种群形成抑制效果最好的是800ppm的桔皮提取物,抑制率为93．4％;其次是800ppm的脐橙提取物,抑制率为85．7％。800ppm的一年蓬花瓣、肉桂、艾蒿、山柰、鱼腥草提取物对赤拟谷盗种群形成抑制率依次为78．1％、76．4％、74．4％、67．8％、54．3％。在同种植物提取物的五个浓度梯度中,以最高浓度800ppm的抑制效果最好。在试验剂量范围内,桔皮、脐橙、肉桂、山柰、艾蒿、鱼腥草的提取物对赤拟谷盗成虫和细虫都有不同程度的驱避作用。七种植物提取物对赤拟谷盗成虫和幼虫均未表现明显的触杀作用。     

试论中国诗学对庞德诗歌的影响

中国的诗学对以庞德为主的英美意象派的诗歌影响非常大。试从中西意象论比较、庞德译中国诗、仿体的中国诗,以及作品中蒙太奇手法的运用四个方面论述中国诗学对庞德诗歌的影响。     

低温等离子体技术处理氮氧化物特性研究分析

利用低温等离子体技术转化柴油机NOX很大程度上取决于排气中的气体成分以及等离子体的放电能量,放电过程直接影响气体分子的电子冲击分裂.为此,分析了利用低温等离子体技术处理柴油机NOX排放可能发生的转化反应及其影响因素;并通过介质阻挡放电,研究了放电电压、放电频率与放电功率、功率因数之间的关系,分析了这些因素对处理NOX排放的影响.结果表明,放电功率是等离子体处理氮氧化物最直接的影响因素.     

丘陵地区土地整理工程的环境影响分析

分析了丘陵地区土地整理工程对各环境要素的影响机理、过程和结果,同时根据环境影响分析,简要提出了土地整理工程实施过程中应采取的必要环境保护措施。     

绦柳树干液流变化及其影响因子研究

该文于2006年4—11月利用Granier热扩散探针观测了绦柳的树干液流速率在生长季节的动态变化,并利用全自动气象站同步监测了环境因子。观测结果显示,在土壤水分充足的8月份,绦柳树干平均液流速率为0.004 1 cm/s,液流峰值为0.014 6 cm/s;而在相对干旱的5月份平均液流速率为0.000 503 cm/s,液流峰值为0.003 47 cm/s;土壤水分充足时期液流速率明显高于相对干旱期。在整个生长季节,绦柳液流速率日变化均为明显的单峰曲线,5—11月份各月的峰值分别为0.002 8、0.002 4、0.004 8、0.008 6、0.006 1、0.005 8、0.004 2 cm/s,启动时间和达到峰值时间具有明显的规律性;以太阳辐射强度、气温、空气湿度、风速、不同层次土温等环境因子作为自变量,以边材液流速率作为因变量,经过逐步回归,建立了绦柳液流速率与环境因子的多元线性模型,回归方程极显著,其主要影响因子为空气温度、空气相对湿度和太阳辐射强度。      

三峡库区高速公路建设环境影响分析

通过对三峡库区生态环境要素的分析,对该区域高速公路建设中的生态环境问题进行了探讨,并结合该区域的实际情况提出了在三峡库区高速公路竣工验收环境影响调查中应该注意的一些问题。     

长江三角洲区域土地利用规划环境影响评价研究

以长江三角洲区域土地利用规划为例,结合规划环境影响评价技术导则,对区域土地利用规划环境影响评价程序、影响因子识别和指标体系构建等问题进行探讨,构建一套适合区域土地利用规划环境影响评价的指标体系,并用层次分析法确定各指标的权重,得到评价最终得分,为区域土地利用规划环境影响评价工作的开展提供思路.