气候变化情景下毛竹潜在分布及动态预测

为探究毛竹的潜在分布及其动态变化，并确定对其分布起主导作用的环境变量，文章基于MaxEnt预测模型，利用环境变量图层及316个毛竹分布点数据研究毛竹地理分布的变化。结果显示：1）限制毛竹分布的主要环境变量为最干月降水量、年均降水量、最冷月最低温、年平均温、温度年较差和海拔；2）当前毛竹的潜在适生区主要位于中国东南部，与亚热带季风气候区大致重叠，高适生区主要位于总适生区的东部和西北部；3）在未来气候情景下，毛竹总适生区面积有所缩减，各不同等级适生区面积变化大，其中高适生区面积大幅度缩减。研究获得的毛竹适生区变化趋势可为毛竹培育、引种以及入侵防治提供参考。     

基于Google Earth Engine平台的关中冬小麦面积时空变化监测

以关中地区为研究区,基于Google Earth Engine(GEE)平台,根据冬小麦生育期内归一化植被指数(NDVI)时序曲线和物候特征,采用NDVI重构增幅算法和光谱突变斜率,构建了关中地区冬小麦提取模型并实现了冬小麦种植面积的提取。用农业统计面积验证提取结果表明:在市级和县级尺度上,决定系数R~2分别为0.82和0.62,一致性指标d分别为0.95和0.84,提取结果与实地调查数据的空间一致性精度为93.4%。结果显示:关中地区冬小麦主要分布在中部关中平原,冬小麦种植面积在2011—2017年呈下降趋势,减少了83.22×10~3 hm~2(8.47%)。综合考虑冬小麦NDVI时序曲线的"峰""谷"特征,具有一定的普适性,可为大面积连续年份冬小麦种植面积时空监测提供参考。     

Study on a soil erosion sampling survey in the Pan-Third Pole region based on higher-resolution images

Soil erosion is one of the most severe global environmental problems, and soil erosion surveys are the scientific basis for planning soil conservation and ecological development. To improve soil erosion sampling survey methods and accurately and rapidly estimate the actual rates of soil erosion, a Pan-Third Pole region was taken as an example to study a methodology of soil erosion sampling survey based on high-spatial-resolution remote sensing images. The sampling units were designed using a stratified variable probability systematic sampling method. The spatiotemporal characteristics of soil erosion and conservation were taken into account, and finer-resolution freely available and accessible images in Google Earth were used. Through the visual interpretation of the free high-resolution remote sensing images, detailed information on land use and soil conservation measures was obtained. Then, combined with the regional soil erosion factor data products, such as rainfall-runoff erosivity factor (R), soil erodibility factor (K), and slope length and steepness factor (LS), the soil loss rates of some sampling units were calculated. The results show that, based on these high-resolution remote sensing images, the land use and soil conservation measures of the sampling units can be quickly and accurately extracted. The interpretation accuracy in 4 typical cross sections was more than 80%, and sampling accuracy, described by histogram similarity in 11 large sampling sites, show that the landuse of sampling uints can represent the structural characteristics of regional land use. Based on the interpretation of data from the sample survey and the regional soil erosion factor data products, the calculation of the soil erosion rate can be completed quickly. The calculation results can reflect the actual conditions of soil erosion better than the potential soil erosion rates calculated by using the coarse-resolution remote sensing method.     

Genetic differentiation of Mycobacterium bovis and Mycobacterium tuberculosis isolated from cattle and human sources in,Egypt (Suez Canal area)

Bovine tuberculosis is a devastating illness in cattle and it has the ability to transmit causing severe troubles in human. Mycobacterium bovis (M. bovis) infection in human indeed becomes increasingly critical especially in developing countries. Early diagnosis is very important to control and limit its spreading. The aim of this study is to examine the genetic differentiation and possibilities of transmission between cattle and human. Lymph node and sputum samples were collected from cattle and patients showing tuberculin test positive; respectively for phenotypic identification and for molecular examination by detection of IS6110 and oxyR genes which are specific for MTC and M. bovis; respectively. The phenotypic identification of sputum samples showed 80 % positive by both stain and culture, while, lymph nodes revealed 66 % and 84 % positive by stain and culture method; respectively. Alignment of oxyR gene sequences of M. tuberculosis and M. bovis was used as a feature for differentiation between the 2 genes in these two genetically closely similar microorganisms showed 99 % identities between the 2 genes. Alignment and phylogenetic analysis of Mpb70 gene sequences from animal and human origin showed very high relatedness (99.32 %) to each other confirming that the zoonotic transmission is most probably occurred.     

基于网络嵌入性的我国东北国有林区知识转移机理

文中从社会网络视角分析我国东北国有林区职工、家庭及林业企业知识转移的过程和影响因素，以期通过社会关系和网络结构促进林业企业转型。应用知识转移基本理论构建东北国有林区多层次知识转移理论模型，在此基础上从社会网络视角分析林区职工、家庭和林业企业3个层面的知识转移机理。研究表明:增强林区知识转移个体与利益相关者的联系程度、占据更多的结构洞位置以及提高个体网络中心度和凝聚程度有利于知识获取和内化；林区待岗职工与利益相关者的弱联系有利于其获得更多就业机会；国有森工企业由于过度嵌入社会网络，知识内化和创新动力不足。     

高寒丘陵区不同退耕年限人工林形质评价

基于时空互代法研究不同退耕年限对青海东部人工林形质的影响，为高寒丘陵区人工林经营及多功能利用提供理论依据。在青海东部西宁市大通县设置青杨、祁连圆柏、青海云杉和华北落叶松典型人工林试验样地，开展退耕年限10、20 a和30 a样地调查。以生长情况、侧枝情况和土壤养分情况作为退耕还林林木形质评价指标，运用层次分析法构建林木形质的评价体系，对4种人工林林木形质进行综合评价。干形情况对林木形质的影响最大，贡献率占0.603；生长情况对其影响次之，贡献率占0.337；侧枝情况对其影响较小，贡献率仅占0.060；16个评价指标在林木形质评价中的权重大小依次为健康情况(0.674 9)＞自然整枝能力(0.598 8)＞土壤有机质(0.578 7)＞通直度(0.526 5)＞分杈情况(0.348 0)＞土壤K(0.232 5)＞侧枝平均基径(0.202 7)＞胸径年均生长量(0.176 9)＞枝粗指数(0.150 6)＞土壤N(0.139 2)＞树高平均生长量(0.107 6)＞高径比(0.071 5)＞尖削度(0.054 0)＞土壤P(0.049 6)＞侧枝数(0.047 9)＞冠径比(0.040 7)；综合评价得分依次为青杨(81.67)>华北落叶松(80)>青海云杉(75)>祁连圆柏(60)。森林生态系统通过自我调节,其发育呈正向演替。高寒丘陵区人工林形质随退耕恢复年限增加呈先增加后减少趋势。前期造林(10 a)可迅速提高林地盖度；发育至20 a时，林地林木形质最优；退耕30 a，林下光照减少，下层出现竞争缺光,影响林地涵养水分功能发挥，影响林木形质。以层次分析法建立的林木形质评价体系可为高寒丘陵区人工林经营及多功能利用提供依据，为其他树种形质评价提供借鉴。     

2种水分生境下红砂叶片功能性状的响应及适应机制

干旱是中国西北荒漠生态系统的主要特点之一，干旱对植物的生长、发育、繁殖及分布等产生重要的影响。红砂是广泛分布在我国温带荒漠草原生态系统中的优势种和主要建群种之一，对多种环境胁迫尤其是干旱胁迫具有极强的耐受性。因此，研究红砂对不同水分生境的响应及适应机理有着重要的科学意义。对不同水分条件自然生境中(小红山地区和长流水地区)的红砂叶片形态、表皮微形态及超微结构进行分析，揭示红砂适应干旱胁迫的叶片形态结构特征。结果表明，随着生境中土壤含水量的降低，红砂叶片厚度增大，叶面积及气孔开度减小，角质层增厚，从而降低植物蒸散过程中体内水分的散失。表皮细胞面积减小，表皮细胞密度增大，细胞壁增厚，增加了表皮细胞弹性，有助于降低干旱胁迫下植物失水造成的机械损伤。与此同时，栅栏组织增厚，且细胞排列更加致密，海绵组织的厚度减小，在一定程度上促进叶片的光合作用进行。因此，红砂叶片的形态结构特点使其对干旱具有极强的耐受性。研究揭示了荒漠植物红砂的叶片形态结构对不同水分条件的响应，为理解荒漠植物对水分限制的响应机制提供数据支持。     

明清时期西辽河地区农业开发的动力与制约因素

在辽金元农业开发的基础上,明清时期西辽河地区农业开发取得了很大进步。农业发展有利于维护西辽河地区乃至边疆地区的稳定,良好的农业开发环境促进了西辽河地区经济繁荣。明清两代非常重视农业,大力支持西辽河地区的农业开发,给予西辽河地区农业生产资料,加之其他政策的实行、农业生产技术的传授、高产耐旱粮食作物的栽培和驿站、桥梁的建设等,使西辽河地区的农业开发成果颇丰,至清代更加显著。自然灾害等成为制约农业开发的主要因素。本文在前人研究的基础上,对西辽河地区农业开发的动力与制约因素做出了进一步讨论。     

惠州地区猴头菇高效栽培技术研究

惠州市对猴头菇的栽培研究还比较少,但市场对猴头菇的需求却日益增加。该文主要从8个方面介绍了惠州地区猴头菇的高效栽培技术,为菇农生产提供一些参考。     

气候变化背景下舟山沿岸上升流区夏季水动力演变机制

全球变暖会对舟山沿岸上升流的驱动机制产生深远影响,继而作用于海域内的生态环境及渔业资源发生的变迁。使用三维海洋数值模型FVCOM,模拟研究了热通量、风场等气候环境因子变化下舟山沿岸上升流区夏季水动力及环境因子的分布特征。通过引入跃变检验方法来评估全球变暖对过去三十多年来舟山及其邻近海域的夏季海表温度的影响,发现在2016年前后发生了明显的跃变,跃变后海表温度相对于跃变前升高了约1 °C;热通量分析结果显示春季云量减小,短波辐射增加导致的海水热含量增加是夏季海水升温的重要原因;风速的时空变化表明舟山海域7月风速在近几十年有减弱的趋势。通过构建气候环境因子变化的敏感性数值模型实验探究了舟山沿岸上升流水动力的演变机制,结果表明海气热通量增加导致的表层海水吸热及平流热输运增加引起的海水层化加强会使得底层海水不易抬升;夏季风应力的减弱削弱了长江冲淡水低盐水舌的离岸扩展,导致上升流区上层海水的层化减弱,从而加强中下层海水向岸爬升,增加沿岸上升流的强度。