中国主要农用矿产资源安全保障战略研究

主要农用矿产资源(硫、磷、钾)的利用状况和安全保障程度关系国家粮食安全及人类生存发展.本文应用定性分析与定量研究相结合等方法,对硫、磷、钾农用矿产资源安全保障进行综合研究.结合全球硫、磷、钾资源供给格局和国外资源可获得性分析,从供给、需求和国家保障三个层面,提出保障我国主要农用矿产资源(硫、磷、钾)安全、合理开发利用、...     

大型深水贫营养水库——新丰江水库浮游动物群落分析

新丰江水库是位于广东省境内的一座大型深水贫营养水库.为了解这一典型贫营养水体的浮游动物群落特征,于2002-2003年对该水库的轮虫和浮游甲壳动物进行了研究.新丰江水库的浮游动物主要为广布性种类,优势类群是桡足类,其幼体的数量高于成体,优势种为舌状叶镖水蚤、温中剑水蚤和微小近剑水蚤.枝角类优势种是长额象鼻溞、短尾秀体溞和角突网纹溞.轮虫优势种为个体较小的螺形龟甲轮虫和彩胃轮虫.优势种的个体体长为50-1450 μm,个体最大的是舌状叶镖水蚤,平均体长为1190 μm,个体最小的是彩胃轮虫,平均体长为80 μm.在12月份,可能由于银鱼的摄食强度较高,导致大个体(主要为舌状叶镖水蚤及其大个体的哲水蚤幼体)的数量和生物量较低.在其余3个采样月份,浮游动物受银鱼影响相对较小,舌状叶镖水蚤的数量和生物量均远高于透明溞,可能与它们临界食物浓度及滤食方式的差异有关.根据对优势种的分析,新丰江水库的浮游动物群落具有典型的贫营养水体特点.     

农业水生产力研究进展

文章系统阐述了农业水生产力概念的发展过程,综合分析了影响农业水生产力的主要因素,详细列举了不同尺度上评估农业水生产力所需的水流及产出计算方法,给出了4种主要农作物在全球范围内的水生产力的分布范围与空间格局,并从提高水分利用效率、加强田间水资源管理、选择适宜的种植模式和栽培技术以及培育更加高效的农作物品种4个方面全面综述了各种水生产力提高策略。指出在未来的水生产力研究中还需要强调农户的参与以及学科间的协作,加强水生产力尺度效应、水权与水价问题、虚拟水交易、水生产力提高措施对环境影响等方面的研究。     

全球钛资源行业发展现状

钛矿是我国对外依存度较高的矿种之一,对我国战略性新兴产业的发展起着重要的支撑作用,对全球钛矿行业的发展现状进行分析与研究,能够为我国钛矿资源安全提供重要研究依据.本文对全球钛资源的储量及分布状况、钛资源的生产和消费情况进行了分析.分析结果显示,我国是钛资源大国,钛储量位居世界第一;但多为共伴生矿,品位不高.钛精矿进口量...     

河西内陆河流域水生态安全评价研究

水安全评价相关研究已有较多成果,但绝大多数采用P-S-R(压力-状态-响应)及其扩展模型,且评价指标体系的优化校准几乎从未提及.本文将W-SENCE(与水有关的社会-经济-自然复合生态系统)模型引入水生态安全评价领域,从水生态安全的自然属性和社会经济属性方面构建水生态安全评价指标体系,结合模糊系统分析及改进生态位理论对...     

Wetter isn't better: global warming and food security in the Congo Basin

Over 20 million forest farmers practice slash and burn agriculture in the forests of the Congo Basin (Bahuchet and de Maret, 1995. State of Indigenous Populations Living in Rainforest Areas, European Commission DG XI Environment, Brussels). They rely on the long dry season (December–February north of the equator) to ensure that their new fields, cleared from regrowth forest, burn sufficiently well to deposit nutrients into the soil and to minimize the labor required to prepare the field for planting. Data from the Ituri forest in northeastern Democratic Republic of Congo show that the strength of the annual dry season (a) has a direct positive impact on the size of fields cleared each year by slash and burn farmers, and consequently on food production and the severity of the subsequent year's pre-harvest hunger period; and (b) is inversely related to total annual rainfall. These results suggest that the 1 mm/d increase in rainfall predicted for much of the Congo Basin by the 2050s may cause a basin wide increase in the frequency of heavy rains during the dry season, causing a reduction in the size of slash and burn farmers’ fields, and potentially a substantial increase in the food insecurity of poor rural families across the region.     

Nitrogenous Excretion of Penaeus monodon Postlarvae Fed with Different Diets

This study is designed to determine ammonia and nitrite excretion by Penaeus monodon 25–30 day old postlarvae fed with different diets (artificial and natural). Shrimps were fed with Chaetoceros calcitrans (phytoplankton), chironomid larvae (benthos), Brachionus sp. (rotifer) and artificial diet. In the control treatment, shrimps were not fed. The highest concentration of ammonia was excreted by shrimps fed with artificial diet and the lowest by that of control treatment. All treatments except where shrimps fed on C. calcitrans showed a sudden increase in ammonia-N excretion after 36 h. C. calcitrans contributed to high ammonia excretion only after 61 h. Shrimps fed with Brachionus sp. (rotifer) showed significantly higher nitrite excretion rate compared to other treatments. Shrimps fed on C. calcitrans depicted the lowest nitrite excretion. This experiment indicated that nitrogenous excretion was predominant in shrimps fed with artificial diets. Live food like algae and chironomids, despite a high protein content, contribute to low nitrogenous excretion and hence pose less adverse effects on water quality compared to artificial diets.     

提高食物链硒通量防治大骨节病和克山病示范研究

本研究在黄土高原的陕西省彬县大骨节病和克山病重病区,进行小麦、蔬菜的叶面喷Ｓｅ和主食加Ｓｅ防治地方病的示范研究。结果显示,喷Ｓｅ小麦含Ｓｅ量达０．０８１μｇ／ｇ,明显高于未喷Ｓｅ的小麦（０．００９μｇ／ｇ）;示范点膳食含Ｓｅ达０．０７６μｇ／ｇ,显著高于对照点（０．０１４μｇ／ｇ）;示范点人均日摄Ｓｅ量由１３．４０μｇ／ｇ提高到６０．３９μｇ／ｇ;大骨节病Ｘ线阳性检出率由４３．３３％下降到６．４５％,达到国家控制标准。     

西北干旱区生态安全系统结构与功能的监控思路初论

基于西北干旱区生态安全系统监控的必要性,分析了西北干旱区生态安全系统监控机理,进而提出了干旱区生态安全系统结构监控与功能监控的思路与方向,旨在为西北干旱地区生态重建与经济可持续发展提供理论依据。     

Food web manipulation by extreme enhancement of piscivory: an invertebrate predator compensates for the effects of planktivorous fish on a plankton community

By enhancing the stock of piscivorous fish in a whole-lake experiment in Gräfenhain (Germany) since 1981 to such an extent that almost all planktivorous fish were exterminated, we examined the concept of “over-biomanipulation”. This hypothesis predicts that (a) extremely strong piscivory will allow uncontrolled development of large invertebrate predators and (b) these invertebrates can exert the same strong predation pressure on large herbivorous zooplankton as planktivorous fish. The hypothesis is tested the first time by a cross-comparison of the long-term response of the plankton community structure in the experimental lake (Piscivore L.) with (1) the intermediate response in the same lake and with (2) that of the long-term state in a nearby reference lake (Planktivore L.) densely inhabited by planktivorous fish (Leucaspius delineatus, a small cyprinid). The intermediate (1989–1992) response in Piscivore L. revealed a strong increase of the abundance of the invertebrate predator Chaoborus flavicans. Large daphnids were able to coexist with C. flavicans so that edible phytoplankton were suppressed and water transparency increased.As part (a) of the hypothesis predicts, the long-term response in Piscivore L. was characterized by the immigration of the larger predator Chaoborus obscuripes which displaced the smaller C. flavicans completely. The results support also part (b) of the hypothesis of “over-biomanipulation”: C. obscuripes-dominated Piscivore L. showed not much difference in biomasses of daphnids and total and edible phytoplankton as well as Secchi depth compared with fish-dominated Planktivore Lake. On the other hand, C. obscuripes-dominated Piscivore L. was characterized by distinctly lower biomass of daphnids, mean body volume of all crustaceans and Secchi depth as well as by higher biomass of edible phytoplankton compared with C. flavicans-dominated Piscivore Lake. We conclude that long-lasting success of biomanipulation cannot be achieved by extremely high piscivory leading to the almost complete extermination of planktivorous fish.