冀北山地杨桦次生林不同林层的空间结构特征   总被引：1，自引：0，他引：1  

张曼  高兴九  孙海静  崔丽红  李永宁  黄选瑞 《东北林业大学学报》2014,(9)

利用混交度、角尺度、大小比数和开阔比数4个空间结构参数,结合空间结构单元距离尺度,研究了冀北山地杨桦次生林更新层和乔木层（低林层、中林层和上林层）的空间结构特征。结果表明：乔木层和更新层平均混交度分别为0．520、0．228,差异较大,乔木层混交度随林层增加而降低;乔木层和更新层的平均角尺度分别为0．575、0．530,属于聚集分布,乔木层聚集强度随林层增加而降低;乔木层和更新层平均大小比数分别为0．493、0．511,各等级林木分布较均匀;乔木层平均开阔比数为0．713,处于开阔的光环境中;随着林层增加,大小比数呈下降趋势,开阔比数呈增加的趋势,大小比数与开阔比数呈极显著负相关;参照木与4株最近相邻木的平均距离随林层增加呈递增趋势,但大部分相邻木分布在3m以内。  相似文献   

林用单轨运输车液压传动系统的设计研究     

龙萍  姚立红  刘凯  张强 《林业机械与木工设备》2014,(6):21-24

针对目前林用单轨运输车所采用的机械传动方式存在问题以及林业生产单位对其大载重量的要求,将原机械传动方式改进为液压传动方式。介绍了单轨运输车采用液压传动方式的特点,分析了该液压系统的工作原理。  相似文献   

可移植的UART底层驱动构件设计     

蔡剑卿  王宜怀  冯德旺  罗超 《福建农业大学学报(自然科学版)》2014,(3):332-335

以飞思卡尔公司基于ARM Cortex-M4内核的K60系列微控制器为例,设计了一种具有较好可移植性和重用性的UART底层驱动构件．测试结果表明该构件正确而有效．  相似文献   

行初等变换化矩阵为对称矩阵及其算法     

陈学灵  ;陈梅香  ;陈清华  ;杨忠鹏 《吉林林学院学报》2014,(6):719-724

从行等价的理论和方法出发,以构造形式讨论了如何通过对矩阵具体的行初等变换得到对称矩阵,在此基础上给出了算法程序。  相似文献   

Small cetacean captures in Peruvian artisanal fisheries: High despite protective legislation     

Jeffrey C. Mangel  Joanna Alfaro-Shigueto  Koen Van Waerebeek 《Biological conservation》2010,143(1):136-143

We detail the first direct, at sea monitoring of small cetacean interactions with Peruvian artisanal drift gillnet and longline fisheries. A total of 253 small cetaceans were captured during 66 monitored fishing trips (Gillnet: 46 trips; Longline: 20 trips) from the port of Salaverry, northern Peru (8^o14′S, 78^o59′W) from March 2005 to July 2007. The most commonly captured species were common dolphins (Delphinus spp.) (47%), dusky dolphins (Lagenorhynchus obscurus) (29%), common bottlenose dolphins (Tursiops truncatus) (13%) and Burmeister’s porpoises (Phocoena spinipinnis) (6%). An estimated 95% of common dolphin bycatch was of long-beaked common dolphins (Delphinus capensis). Overall bycatch per unit effort for gillnet vessels (mean ± sd) was estimated to be 0.65 ± 0.41 animals.set⁻¹ (range 0.05-1.50) and overall catch (bycatch and harpoon) was 4.96 ± 3.33 animals.trip⁻¹ (range 0.33-13.33). Based upon total fishing effort for Salaverry we estimated the total annual average small cetacean bycatch by gillnet vessels as 2412 animals.year⁻¹ (95% CI 1092-4303) for 2002-2007. This work indicates that, in at least one Peruvian port, bycatch and harpooning of small cetaceans persist at high levels and on a regular basis, particularly in driftnet vessels, despite the existence since the mid-1990s of national legislation banning the capture of marine mammals and commerce in their products. It is concluded that the coast of Peru is likely still one of the world’s principal areas for concern regarding high small cetacean bycatch and there is clearly an urgent need to increase the geographic scope of observer effort to elucidate the full magnitude of this issue.  相似文献   

Morphological responses of bedding plants to three greenhouse temperature regimes     

Richard H. Merritt  K. C. Ting 《Scientia Horticulturae》1995,60(3-4):313-324

Seedling crops of gazania, geranium, marigold, mimulus, pansy, verbena and vinca were grown to 60% anthesis in three greenhouse temperature regimes: (a) 26 °C day/6 ± 3 °C night (LT), with a 16.5 °C mean daily temperature (MDT), (b) 26 °C day/17 ± 4 °C night, with a 21 °C MDT, and (c) variable day/night temperatures in response to heating and cooling by a phase change material energy storage module (PCM) with an 8 ± 2 °C night and a 16 °C MDT. Crops bloomed from 2 to 17 days earlier in the 26 °C/17 °C greenhouse. The morphological characteristics of all cultivars of gazania, mimulus, pansy and verbena, geranium and vinca were similar regardless of greenhouse temperature regime. Marigold diploid and triploid cultivars and mimulus were morphologically more variable than the other bedding plant species. Crops grown in the PCM and LT greenhouses had virtually identical morphological characteristics and bloomed in about the same number of days. Plant height was not affected by DIF environments in the greenhouses. The PCM and LT greenhouses had a similar MDT, but the distribution of numbers of hours of mean daily temperatures was different.  相似文献   

棉花群体叶面积载荷量与产量关系及对源的调节效应研究   总被引：22，自引：6，他引：16  

陈德华  吴云康  段海  王志国 《棉花学报》1996,(2)

通过对棉花单位叶面积负载的生殖器官量的研究结果表明：较高的叶面积载荷量［以单位叶面积负载的果节数（个／ｍ２叶）、结铃数（个／ｍ２叶）及生殖器官干重（ｋｇ／ｍ２叶））能够促进棉花群体叶片光合强度提高和养分向棉铃输送增多，因而群体成铃数增多，产量提高。同时由剪叶、疏蕾试验揭示了，当群体叶面积系数控制在适宜范围内，可通过提高叶面积载荷量使产量进一步上升，群体叶面积系数过大时，通过减少叶面积，提高叶面积载铃量可以使产量增加。而当叶面积过小时，虽叶面积载荷量增大，但终因光合面积太小，产量下降，因此叶面积载荷量可作为反映棉花群体源库是否协调及改进栽培技术的依据。  相似文献   

我省天保工程公益林建设项目作业设计存在问题与对策   总被引：2，自引：0，他引：2  

查贵生 《林业调查规划》2003,28(4):46-49

我省天保工程实施两年来，公益林建设项目作业设计率已达95％以上，然而还存在着一些单位领导对作业设计重要性认识不到位等诸多问题，据此提出了今后若干对策。  相似文献   

水稻籽粒有关性状与粒重关系的初步探讨   总被引：36，自引：3，他引：36  

王余龙  姚友礼 《作物学报》1995,21(5):573-578

成熟期测定武育粳２号不同比重籽粒的有关性状，分析其与粒重的关系。结果表明：（１）不同比重谷粒及其糙米的长、宽度差异较小，厚度、体积差异较大，千粒重极差达６．４３ｇ；谷壳的面积和体积差异较小，谷壳重及单位面积谷壳重差异较大；（２）粒重为谷粒体积与比重的乘积，随着谷粒体积的增大，其比重明显提高（ｒ＝０．９２３４），粒重极显著地增加（ｒ＝０．９８８０）；（３）谷粒体积与糙米体积的大小关系密切（ｒ＝０．９  相似文献   

基于遥感技术的气象因素变化影响水稻单产定量研究   总被引：2，自引：0，他引：2  

何英彬陈佑启  唐华俊 《华北农学报》2007,22(B10):209-215

以黑龙江省五常市为研究区域，应用在水稻移栽期至成熟期选择的系列MODIS影像反演NDVI，通过NDVI间接反演LAI，并逐日拟合水稻全生育期的LAI，结合SIMRIW模型，计算研究区域2006年低温影响下的水稻单产。经演算，水稻单产值为5411．74kg／hm^2，是实际值的84％。研究结果表明应用高时间分辨率MODIS图像能够准确反演并拟合逐日LAI，可以为冷害影响下水稻单产的研究提供参考。  相似文献