南梅北引说梅花

梅花原产于我国西藏、长江流域至台湾岛屿,为我国冬末暮春观花的主要植物。通过南花北引、抗寒能力的驯化、栽培、繁育和现代园林的应用,发掘梅文化,带动旅游产业与国花评选。     

森林经营对土壤酶活性影响的研究进展

为探讨土壤质量酶指标研究的新思路,把有关森林经营对土壤酶活性影响的研究资料进行了归纳总结。结果发现:林地利用方式的改变、人工林的培育模式、森林抚育措施以及林地施肥管理等各种森林生态系统经营过程,都显著改变着土壤酶活性。酶是反映森林土壤质量高低的重要生物学指标,在一定程度上也可反映森林经营措施的实施效果。今后在森林土壤酶的研究中,应重视水解酶的种类、酶指标的敏感性以及酶变化机理的探索。     

北京山区典型针叶林树种蒸腾特性比较

该文通过比较油松和侧柏的蒸腾特性,为北京生态涵养带抗旱树种的筛选提供基础数据。采用Li--6400型便携式光合仪在2006年5—10月对北京市密云水库典型针叶林(油松和侧柏)的蒸腾速率进行了测定。结果表明,油松和侧柏的日平均蒸腾速率分别为2.18和1.95mmol/(m2.s),日平均水分利用率分别为3.52和3.04μmol/mmol。油松和侧柏的水分利用率均在11:00时达到峰值,光合速率的变化趋势均为单峰曲线,且在12:00前后达到峰值。因此,油松和侧柏作为北京山区两种典型针叶树种具有相似的蒸腾特性,油松的日平均蒸腾速率和水分利用率均略高于侧柏,蒸腾作用受环境因子综合影响,气孔导度是影响油松和侧柏蒸腾速率的主要因子。     

Landscape effects mediate breeding bird abundance in midwestern forests

We examine the influence of both local habitat and landscape variables on avian species abundance at forested study sites situated within fragmented and contiguous landscapes. The study was conducted over a six year period (1991–1996) at 10 study sites equally divided between the heavily forested Missouri Ozarks and forest fragments in central Missouri. We found greater species richness and diversity in the fragments, but there was a higher percentage of Neotropical migrants in the Ozarks. We found significant differences in the mean number of birds detected between the central Missouri fragments and the unfragmented Ozarks for 15 (63%) of 24 focal species. We used stepwise regression to determine which of 12 local vegetation variables and 4 landscape variables (forest cover, core area, edge density, and mean patch size) accounted for the greatest amount of variation in abundance for 24 bird species. Seven species (29%) were most sensitive to local vegetation variables, while 16 species (67%) responded most strongly to one of four landscape variables. Landscape variables are significant predictors of abundance for many bird species; resource managers should consider multiple measures of landscape sensitivity when making bird population management decisions.Order of first two authors decided by coin toss     

Interactions Among Different Devices and Electrical Stimulus on the Electroejaculation of Captive Agoutis (Dasyprocta leporina)

The interactions among different electroejaculation devices associated with serial or continuous stimuli were investigated to improve the efficiency of the electroejaculation for semen collection in agoutis. Ten sexually matured male Dasyprocta leporina were restrained by the intramuscular administration of xylazine–ketamine association. Each individual was randomly subjected to four electroejaculation protocols, by combining two devices (one presenting longitudinal electrodes emitting square waves and other presenting ring electrodes emitting sine waves) and two electrical stimuli protocols (serial or continuous). A total of 40 attempts for electroejaculation were conducted in agoutis, being 10 per treatment. The most efficient treatment in providing ejaculates containing sperm (p < 0.05) was that using and electroejaculator connected to a probe with ring electrodes and associated with serial stimuli (4/7; 57%). In spite of semen parameters obtained by sine waves were adequate for using the samples for assisted reproduction, higher values for sperm motility and functional membrane integrity were obtained in the use of the square wave, independently of the electric stimulation protocol used (p < 0.05). In conclusion, we verified that the use of a device presenting a probe with ring electrodes and emitting sine waves, associated with a serial stimuli protocol, improves the efficiency for semen obtaining by electroejaculation in adults D. leporina.