Determination of fiber length and juvenile and mature wood zones in Acer velutinum Boiss. trees grown in Iran

In our investigation we studied fiber lengths and the transition age from juvenile to mature wood in Acer velutinum Boiss. For this purpose, samples from three normal maple trees at a Noshahr site in northern Iran were selected. Disks were cut at breast height. Test samples were taken along a radial direction from the pith to the bark, accounting for every ring during a 48-year period. We used the Franklin method to distinguish between fibers of juvenile and mature wood. The results show that the fiber length increased along the radial direction from the pith to the bark. The transition age between juvenile and mature wood was determined at the 14th annual ring from the pith.     

扬州古运河风光带生态景观型林地模式的环境效应

对扬州古运河风光带生态景观型林地模式的环境效应进行了测定,结果表明:林地模式较对照能显著减少噪音3~10dB,叶片大而质硬并重叠排列的树种减噪效果较好;分枝低、树冠矮的乔木减噪作用要比分枝高、树冠高的乔木明显。林分内不同高度的光照强度分布,由林冠上层向林地表面逐步递减。       

Effect of tool angles on the chips generated during milling of wood by straight router-bits

 The effect of tool angles on the shapes of chips generated by parallel-to-grain and end-grain milling was explored for China fir and maple under fixed spindle and feed speeds and cutting depth. The milling path was up-milling by straight router-bits with a diameter of 12 mm. The chip shapes could be distinguished as five types: spiral, splinter, flow, thin, and granules or powder. The flow and thin chips were generated most often (on a weight percentage basis) for all tool angles investigated for parallel-to-grain and end-grain milling of China fir and maple. More granule chips were produced with parallel-to-grain milling than with end-grain milling for both woods. The measured chip thickness (t′) was thicker than the calculated thickness (t _max). Thicker and longer maple chips were produced by end-grain milling than by parallel-to-grain milling. The tool geometries of 40°/15° (sharpness of the angle–rake angle), 50°/15°, and 60°/15° for China fir and 40°/25°, 50°/5°, and 60°/5° for maple produced relatively more flow chips with parallel-to-grain milling. Furthermore, the tool geometries of 40°/5°, 50°/15° and 60°/25° produced more flow chips (weight percentage) by end-grain milling of China fir and maple. Received: May 23, 2001 / Accepted: June 28, 2002 Acknowledgment This study was supported by a grant from the National Council of Science, Taiwan (NSC89-2313-B-415-011).     

河西走廊城镇绿化树种引种栽培试验

十多年来,河西走廊引进各类观赏树种品种120余个,并对其生物学特性、栽培区划、繁育技术、水肥管理、越冬技术、造型和混交栽植等方面进行了研究,初步筛选出适于河西走廊城镇绿化的优良适生品种50多个。       

北京林业发展战略研究与规划

北京市位于华北平原的北端,东南与天津市接壤,其余边界均与河北省相邻,距渤海约150km,是中国的首都。全市陆域面积1.68万km2。       

Effects of cryptic mortality and the hidden costs of using length limits in fishery management

Fishery collapses cause substantial economic and ecological harm, but common management actions often fail to prevent overfishing. Minimum length limits are perhaps the most common fishing regulation used in both commercial and recreational fisheries, but their conservation benefits can be influenced by discard mortality of fish caught and released below the legal length. We constructed a computer model to evaluate how discard mortality could influence the conservation utility of minimum length regulations. We evaluated policy performance across two disparate fish life‐history types: short‐lived high‐productivity (SLHP) and long‐lived low‐productivity (LLLP) species. For the life‐history types, fishing mortality rates and minimum length limits that we examined, length limits alone generally failed to achieve sustainability when discard mortality rate exceeded about 0.2 for SLHP species and 0.05 for LLLP species. At these levels of discard mortality, reductions in overall fishing mortality (e.g. lower fishing effort) were required to prevent recruitment overfishing if fishing mortality was high. Similarly, relatively low discard mortality rates (>0.05) rendered maximum yield unobtainable and caused a substantial shift in the shape of the yield response surfaces. An analysis of fishery efficiency showed that length limits caused the simulated fisheries to be much less efficient, potentially exposing the target species and ecosystem to increased negative effects of the fishing process. Our findings suggest that for overexploited fisheries with moderate‐to‐high discard mortality rates, reductions in fishing mortality will be required to meet management goals. Resource managers should carefully consider impacts of cryptic mortality sources (e.g. discard mortality) on fishery sustainability, especially in recreational fisheries where release rates are high and effort is increasing in many areas of the world.     

东北黑土区横垄坡耕地的产流产沙过程

[目的]在漫川漫岗黑土区开展横垄坡耕地冲刷试验研究,为黑土地保护工作提供理论依据.[方法]采用野外现场放水冲刷试验,研究了10,30,50和70 m横垄坡耕地径流小区,在不同上方来水量下的产流、产沙过程.[结果]3种冲刷流量(0.34,0.67和1.00 L/min)条件下的径流系数和含沙量均随坡长的增加持续波动,但不...     

Repeatability of fin length measurements using digital image analysis and studies of fin erosion as indicator of social interactions in Atlantic cod (Gadus morhua)

The aims of this study were to examine fin erosion caused by social interactions between Atlantic cod (Gadus morhua) juveniles, and to evaluate the repeatability of recorded fin length using digital image analysis (DIA). Fin length of 2100 juvenile Atlantic cod was analysed using DIA, during a 6 weeks experiment. The lengths of the three dorsal fins and the caudal fin were measured by three different assessors (M, K, B) three times during the experiment. Repeatability was based on a sub set of data from 42 randomly chosen fish. Assessor M measured the length of the fins of the 42 fish three times (M1, M2, M3). M1 and M2 were done on the same day, while M3 was conducted 2 weeks later. Assessor K measured two times with a 2‐year interval, and assessor B measured the fin length only once. The correlations between replicated measurements within assessor were highest for assessor M measured on the same day indicating an effect of memory. Repeatability of fin length ranged from 0.57 to 0.73 for the four fins. Social interaction with respect to fin erosion was studied using data on the four fins from all 2100 fish. ‘Relative fin length’ (fin length/total body length × 100) was calculated to assess fin erosion. Results indicated that all four fins were eroded due to social interactions, but the caudal fin was most severely eroded. In conclusion, DIA can be used to measured fin length but the method could be improved by using chromatic pictures.     

基于有限混合模型的山东海域口虾蛄群体体长结构分析

个体大小是渔业资源种群的重要结构特征,一般研究中采用平均个体体长或平均体质量等分析指标,难以充分反应具有多年龄结构和个体生长速度差异的种群组成差异。为研究口虾蛄个体大小组成的时空变化,实验根据山东海域2016年10月和2017年1、5、8月的底拖网调查数据,应用有限混合模型分析了不同性别、不同时间、不同水深口虾蛄个体大小的频率分布特征。结果发现,除秋季外,山东海域口虾蛄均可区分为高、低两个年龄组,同时雌雄体长分布具有一定的差异。从冬季到夏季,雌性口虾蛄中低龄组个体比例先下降后上升,雄性口虾蛄低龄比例则逐渐下降。就不同水深而言,口虾蛄低龄组个体主要集中在近海海域,其比例由近海向远海逐渐减小。各年龄组的近远海分布表现出季节性差异,春季高龄口虾蛄在近海比例最大,由近海向远海比例逐渐减小;夏季高龄组口虾蛄在20～30 m水深比例最大;冬季高龄组口虾蛄比例则由近海向远海逐渐增加。有限混合模型能够较好地对口虾蛄的体长结构进行分析,解析口虾蛄不同年龄组在山东海域的时空分布,对于深入了解口虾蛄种群分布动态和科学的渔业管理具有重要意义。     

鱼类标志放流步骤的优选及其在黄鳍棘鲷中的应用

鱼类标志放流过程中,关键细节缺失参考依据易导致标志鱼因标志操作不规范而死亡(或导致标志脱落),从而影响基于标志群体抽样的增殖效果评估、放流群体时空格局等后续研究的准确性。本研究以南海重要增殖放流鱼类黄鳍棘鲷为对象,采用多因素方差分析对比了标志过程中关键操作(标志前麻醉与否、标志部位、植入角度)的生长率、存活率、标志保留率的差异。40 d的实验结果显示,不同标志操作对鱼的生长无显著影响。麻醉与否对实验鱼的存活率影响极显著。标志部位、植入角度对标志保留率影响显著。优选出的最佳标志操作组合为麻醉,将T型标志以45°植入背鳍基前部肌肉(存活率95.56%、标志保留率98.89%)。综合以往资料,本研究提出了黄鳍棘鲷[体长(10.05±0.39)cm]T型标志操作规范建议,为今后科学开展标志放流提供参考依据:①标志前暂养,将待标志鱼放入培育池内暂养3 d或以上,标志前24 h停食;②材料消毒,将T型标志和标志枪针头用75%酒精浸泡消毒5 min;③麻醉,用30 mg/L丁香酚溶液(或MS-222麻醉剂)麻醉至鱼体腹部向上翻转时,迅速进行标志;④标志,用标志枪针头拨去标志部位的1个鳞片,然后针头与鱼体呈45°将T型标志植入背鳍基前部肌肉;⑤鱼体消毒,将标志鱼放入含有5%聚维酮碘(或高锰酸钾)的海水溶液中药浴消毒30 min;⑥标志后暂养,消毒后的标志鱼人工暂养7 d后可放流。