干旱区绿洲荒漠交错带土地退化及生态重建

由于经济的发展，土地资源受到越来越大的压力。当这种压力超过了土地资源的承载能力，就导致了土地退化的发生。作为陆地生态系统的基础，土地资源的退化表现为：土壤肥力降低，生物多样性降低，以及伴随的经济发展的落后。当前世界范围内对土地退化的治理，基本方法仍是基于生态学理论的生物方法。但对土地退化的恢复与生态系统的重建的研究，需要经过谨慎设计的长期实验。绿洲荒漠交错带的重要性，不仅表现为是绿洲的保护屏障，而且在绿洲经济的发展中也起到巨大的作用。通过对国内外大量研究的回顾，讨论了在不同地区进行的长期实验所采用的方法。有人为因素参与的退化土地恢复与生态重建，可以在短期内取得明显效果。产生土地退化的原因，不仅仅是土地资源特点与自然环境这样一些自然因素，还包括一些社会与经济因素。因此退化土地的恢复与生态重建的成功，需要一种考虑自然、社会和经济因素的综合的方法。     

Leafhopper and planthopper vectors of rice viruses and their management in Nepal

Research on insect pests (including leafhoppers and planthoppers) in Nepal was initiated in 1956 by the Entomology Division and Plant Protection Units of the Department of Agriculture. More systematic work began after the establishment of a Rice Improvement Programme in 1972. Because of poor documentation and publication of research findings, it is difficult to assess the research efforts and achievements to date. The available research reports are mostly published in the proceedings of national seminars/workshops. They are used here to assess the current status of research on the occurrence and damage caused, distribution and composition, relative abundance, biology and management through chemicals. Much of past research has focused on insect surveys by light traps and sweep nets and the evaluation of insecticides and, since early 1990, some research on rice green leafhoppers (Nephotettix virescens and Nephotettix nigropictus) has begun to determine their relative abundance and population characteristics in relation to their potential as vectors of rice viruses. The challenges to pest management in general and some suggestions for future research needs are discussed, based on the present standing of agricultural research in the country     

不同温度下转换寄主对桃蚜生态学特征的影响

在5种温度、4组寄主与蚜源组合处理条件下研究了温度对转换寄主后的桃蚜的影响。同一寄主间移植的桃蚜在有效积温、发育起点温度、生殖率、死亡率、寿命以及抗逆性上与不同寄主间移植的桃蚜有明显的差异;寄主对桃蚜生物学、生态学特征有明显的影响,表明长期生活在一种寄主上的桃蚜获得了一定的专化性。若将其移植到另一种寄主上,则会表现出种种不适反应,但这种反应还未进化至型或寄主生殖隔离。     

棉铃虫对拟除虫菊酯类杀虫剂抗性遗传力的分析

采用域性状分析法,估算了棉铃虫对氰戊菊酯、三氟氯氰菊酯和溴氟菊酯的抗性现实遗传力,并对3种菊酯的抗性风险进行了评估。结果表明,棉铃虫对氰戊菊酯、三氟氯氰菊酯和溴氟菊酯的抗性现实遗传力分别为0.2027、0.1554和0.1084。假设田间种群的抗性现实遗传力为估算值的一半,杀死率为80％,预计抗性增长到10倍时,氰戊菊酯可使用14次,三氟氯氰菊酯可使用19次,溴氟菊酯可使用31次。三氟氯氰菊酯和溴氟菊酯的抗性风险明显低于氰戊菊酯;棉铃虫对含氟菊酯的抗性发展速度明显低于不含氟的菊酯。试验结果为实际应用提供了理论依据。     

黄花苜蓿的优良特性与开发利用

本文简要介绍了苜蓿属植物黄花苜蓿的分布、生境以及饲用价值高、抗寒、抗旱、耐盐碱等优良特性，并对其与紫花苜蓿相比所占的优势、对苜蓿育种的贡献及在草地改良中的生态价值进行了评述。在简述目前我国黄花苜蓿国研究现状的同时，提出要大力开发利用这一牧草资源，它必将对我国畜牧业生产、退化草地改良及水土保持等发挥重要作用。     

210国道榆林至陕蒙交界段建设的生态环境影响评价

在简要分析榆林至陕蒙交界段生态环境对公路及公路建设的影响的基础上 ,重点论述了公路建设在建设期和营运期对当地生态环境的影响 ,并对公路建设前后水土流失与土地沙化状况进行了预测 ,最后提出水土保持与防沙护路的方案。结论是 :只要把公路建设与生态环境建设相结合 ,重视生态环境的保护与建设 ,该公路建设和营运对生态环境的不利影响是很小的 ,而且 ,由于公路建设本身的需要所采取的防沙护路措施 ,会使公路沿线的生态环境更好     

森林生态保护与效益补偿法律机制研究

回顾了森林生态保护与效益补偿机制研究现状与存在问题 ,分析了传统的生态保护政策法律手段的作用和历史局限性 ,指出在市场经济条件下 ,法律机制是生态保护和效益补偿机制的主要保障。着重研究了森林生态补偿法律关系中的主体、客体、补偿强度、补偿方法 ;从立法、执法、监督以及产权改革等方面 ,系统提出了建立我国森林生态补偿法律机制的途径和措施     

甘肃省生态环境综合评价指标体系研究

甘肃省生态系统分为社会经济系统和自然生态系统两大类 ,社会经济系统指标体系由社会经济条件和人为环境压力构成 ;自然生态系统由水环境、森林生态系统、草地生态系统和土壤生态系统四个次一级系统组成 ,每个次一级生态系统由各自所属指标体系来系统评定。利用因子分析法、Delphi法和头脑风暴法经过多次综合专家意见最终确定 2 6项指标作为甘肃省生态环境质量综合评价体系。利用层次分析法 (AHP)定量各指标的权重。通过综合评价表明 ,甘南州、陇南地区、张掖地区的生态环境质量较好 ,甘肃中部广大黄土高原地区次之 ,河西走廊的武威市、金昌市和嘉峪关市环境质量最差。评价结果真实地反映了甘肃省生态环境的基本状况 ,说明该指标体系具有科学性 ,能够用于不同地区之间或同一地区不同时间的环境质量对比与变化研究。     

Characterizing historical and modern fire regimes in Michigan (USA): A landscape ecosystem approach

We studied the relationships of landscape ecosystems to historical and contemporary fire regimes across 4.3 million hectares in northern lower Michigan (USA). Changes in fire regimes were documented by comparing historical fire rotations in different landscape ecosystems to those occurring between 1985 and 2000. Previously published data and a synthesis of the literature were used to identify six forest-replacement fire regime categories with fire rotations ranging from very short (<100 years) to very long (>1,000 years). We derived spatially-explicit estimates of the susceptibility of landscape ecosystems to fire disturbance using Landtype Association maps as initial units of investigation. Each Landtype Association polygon was assigned to a fire regime category based on associations of ecological factors known to influence fire regimes. Spatial statistics were used to interpolate fire points recorded by the General Land Office. Historical fire rotations were determined by calculating the area burned for each category of fire regime and dividing this area by fifteen (years) to estimate area burned per annum. Modern fire rotations were estimated using data on fire location and size obtained from federal and state agencies. Landtype Associations networked into fire regime categories exhibited differences in both historical and modern fire rotations. Historical rotations varied by 23-fold across all fire rotation categories, and modern forest fire rotations by 13-fold. Modern fire rotations were an order of magnitude longer than historical rotations. The magnitude of these changes has important implications for forest health and understanding of ecological processes in most of the fire rotation categories that we identified.This revised version was published online in May 2005 with corrections to the Cover Date.     

Recovery of non-target plants affected by airborne bromoxynil-octanoate and metribuzin

The present study was conducted to evaluate the recovery potential of non‐target plants affected by two airborne herbicides. Sunflower at the two‐leaf stage was used as a test plant and exposed for 24 h in a wind tunnel to a range of concentrations of airborne bromoxynil‐octanoate and metribuzin. Quantum yield (φ_PSII) of exposed leaves and of the second leaf pair developed after exposure was determined at a particular time up to 16 days following exposure. Maximum depression in quantum yield of exposed leaves from which a complete recovery occurred within 16 days was 63% for bromoxynil‐octanoate and 60% for metribuzin respectively. The corresponding maximum concentrations were 1.310 and 0.390 μg m^?3 respectively. The second leaf pair was also affected and showed a similar recovery potential. From the results it can be concluded that the significance of airborne bromoxynil‐octanoate and metribuzin must not be overestimated, as sunflower and non‐target plants with a similar sensitivity are likely to recover from air concentrations of both herbicides reported under field conditions.