环巢湖地区多水塘景观时空格局演变特征及其驱动因素

快速城市化背景下,小型水体(人工、自然、半自然)景观正在大量消失,以环巢湖地区多水塘景观(水塘面积小于10 hm2)为例,基于遥感影像数据,综合运用RS/GIS技术和Fragstats 3.3软件对1989年、2000年和2016年3个年份环巢湖地区多水塘景观格局时空动态进行分析,运用地理探测器深入探讨多水塘景观面积变化驱动要素,对帮助理解多水塘景观演变带来的景观格局——过程关系及多水塘景观保护、利用和恢复等具有重要的现实意义。研究结果表明:(1) 1989—2016年间,农田景观面积比例呈下降趋势,表现的更加破碎,建设用地景观面积比例大幅度增加,森林绿地景观持续破碎化,水体景观面积比例下降,多水塘景观斑块数量、面积、斑块形状指数、最大斑块指数均呈下降趋势;(2)基于3 km×3 km网格单元多水塘景观时空演变特征分析表明,巢湖北岸多水塘景观集中在烔炀镇、黄麓镇,巢湖南岸多集中在白山镇、盛桥镇和槐林镇,这些地区也是多水塘景观格局变化最剧烈的地方;(3)基于地理探测器,揭示环巢湖地区多水塘景观用地变化的主要影响因子。因子探测结果表明,自然环境条件中的坡度因子q值最大,为0.545,其次为建设用地变化量、农田变化量、人口密度变化量和林地变化量等,交互探测结果表明,多水塘景观面积变化各因子交互作用后,对多水塘景观面积变化的影响显著增强,由此表现出多水塘景观变化影响要素的多样性和复杂性。     

西南典型喀斯特地区石漠化时空演变特征——以贵州省普定县为例

为揭示我国西南典型喀斯特地区石漠化时空演变特征,选取贵州省普定县为研究对象,基于Landsat、DEM等影像数据,提取了坡度和4期植被覆盖度、岩石裸露率分布图,并利用地理探测器获得各自的贡献率,反演了1990—2015年4期石漠化空间分布信息,进而讨论了石漠化时空演变特征。结果表明:(1)在1990—2015年间,普定县石漠化演变复杂,经历了由好转到恶化再到好转的阶段,总体趋势在好转,局部恶化,石漠化治理仍需加大力度;(2)中度以上石漠化集中分布在三岔河沿岸附近,轻度以下石漠化则分布较散乱;(3)潜在和轻度石漠化演变方向复杂,潜在石漠化平均变化速率最大(2.75 km2/a),在1997—2006年间更是达到了16.5 km2/a;(4)植被覆盖度与岩石裸露率的变化主要呈负相关,前者的增加主导了石漠化的好转,而后者的增加则控制了石漠化的恶化;(5)石漠化演变存在突变,在三岔河沿岸附近,存在无/潜在石漠化突变为重度以上石漠化的现象;在靠近城乡居民地附近,存在重度以上石漠化突变为无/潜在石漠化的现象;(6)植被覆盖度、岩石裸露率、坡度能较准确反演石漠化,贡献率分别为44%、42%、14%。本文提供的石漠化反演方法快速高效,制作的图件、数据为同行提供了参考,得出的结论为石漠化治理提供了科学支撑。     

Controls on isoprene emission from trees in a subtropical dry forest

Isoprene emission from vegetation is the single most important source of photochemically active reduced compounds to the atmosphere. We present the first controlled-environment measurements of isoprene emission from leaves of tropical forest trees. Our studies were conducted in the Guanica State Forest in Puerto Rico. We report the effects of temperature and light variations on biogenic isoprene emissions during 1995. Maximum emission rates varied among species from 0 to 268 nmol m^?2 s^?1. Values at the upper end of this range of maximum emission rates are 2–3 times higher than values reported from any temperate taxa. Isoprene emission showed strong sensitivity to light and temperature variations. In contrast to temperate plants, whose emissions tend to saturate at a light intensity of ～1000 μmol m^?2 s^?1, emissions from the tropical species increased with light intensity up to 2500 μmol m^?2 s^?1. The temperature optima for emissions from these plants were similar to those previously reported for temperate plants: ～40 °C. The high maximum emission rates and lack of light saturation indicate that estimates of isoprene emission from tropical forests need to be revised upwards.     

同步辐射小角散射实验站探测系统的改进

同步辐射小角X射线散射（SAXS）实验站所用的探测器由原来的NaI闪烁计数器改为位置灵敏探测器,其位置分辨好于100 μm,有效探测面积为50 mm×10 mm,得到了较以往更高质量的SAXS谱,并成功地对液体样品的SAXS谱进行了测试.     

2009-2013年中国西方蜜蜂蜂群损失情况调查分析

近年,欧洲和北美地区相继出现蜜蜂蜂群崩溃(Colony Collapse Disorder, CCD)现象,蜂业科学家在世界范围内开展蜜蜂蜂群损失情况调查与分析。基于此,探讨近4年我国主要西方蜜蜂饲养省份蜂群损失情况,并对损失量、损失原因进行分析。研究采用欧盟政府间合作框架(COST)下项目- CoLoss (Prevention of honey bee COlony LOSSes)项目组提供的国际统一的标准调查表格,利用R语言在RStudio环境下开展全部的统计分析工作,采用广义线性混合模型分析调查数据的相关性及因变量为非正态分布的非独立数据。调查我国12 个主要西方蜜蜂饲养省份的蜂群越冬死亡损失情况。2009-2013 年蜂群平均损失率为8.9%,损失比例同比低于欧洲和北美国家和地区的蜂群损失率,在可接受范围内。利用广义线性混合模型分析,显著影响蜜蜂蜂群损失的因素有:巢脾使用时间及蜂王因素。我国蜂群损失率较低,大部分损失症状不属于CCD。CCD现象在我国尚未确认发生。加强蜂螨及其他病害的防治工作,增加更新巢脾频率,监控蜂王在蜂群中的表现及增加换王次数等可以有效控制蜂群越冬损失率。结果对明确我国蜂群是否受蜜蜂蜂群崩溃症状现象影响提出了明确的解释,对蜂群损失的防控提供重要的指导建议。     

Increased potential for wound activated production of Prostaglandin E2 and related toxic compounds in non-native populations of Gracilaria vermiculophylla

The capacity of the East Asian seaweed Gracilaria vermiculophylla (“Ogonori”) for production of prostaglandin E₂ from arachidonic acid occasionally causes food poisoning after ingestion. During the last two decades the alga has been introduced to Europe and North America. Non-native populations have been shown to be generally less palatable to marine herbivores than native populations. We hypothesized that the difference in palatability among populations could be due to differences in the algal content of prostaglandins. We therefore compared the capacity for wound-activated production of prostaglandins and other eicosatetraenoid oxylipins among five native populations in East Asia and seven non-native populations in Europe and NW Mexico, using a targeted metabolomics approach. In two independent experiments non-native populations exhibited a significant tendency to produce more eicosatetraenoids than native populations after acclimation to identical conditions and subsequent artificial wounding. Fourteen out of 15 eicosatetraenoids that were detected in experiment I and all 19 eicosatetraenoids that were detected in experiment II reached higher mean concentrations in non-native than in native specimens. Wounding of non-native specimens resulted on average in 390% more 15-keto-PGE₂, in 90% more PGE₂, in 37% more PGA₂ and in 96% more 7,8-di-hydroxy-eicosatetraenoic acid than wounding of native specimens. Not only PGE₂, but also PGA₂ and dihydroxylated eicosatetraenoic acid are known to deter various biological enemies of G. vermiculophylla that cause tissue or cell wounding, and in the present study the latter two compounds also repelled the mesograzer Littorina brevicula. Non-native populations of G. vermiculophylla are thus more defended against herbivory than native populations. This increased capacity for activated chemical defense may have contributed to their invasion success and at the same time it poses an elevated risk for human food safety.     

Three-phase extraction and partitioning with the aid of dialysis – a new method for purification of indolyI-3-acetic and abscisic acids in plant materials

A three-phase partitioning method to separate indolyl-3-acetic acid (IAA) and abscisic acid (ABA) from a crude plant extract was developed and evaluated. The aqueous phase at pH 2.7 of a methanolic plant extract constituted the 1st phase, from which IAA and ABA were transferred via diethyl ether, the 2nd phase, to a 3rd phase consisting of an alkaline buffer, enclosed in a dialysis tube. Partitioning of the free forms of the two hormones among the three phases in one container were carried out simultaneously and efficiently. The method also proved to be satisfactory when used as a combined step for both extraction and partitioning, at which the plant homogenate in buffer at pH 2.7 constituted the 1st phase. The content of IAA and ABA in kernels of Zea mays and in hypocotyls of Beta vulgaris were tested with the new method. The method presented is reliable and time-saving, and the demand for chemicals is less than for most of the conventional procedures used.     

西南喀斯特地区石漠化时空演变过程分析

喀斯特地区石漠化对当地社会经济的可持续发展有严重的阻碍作用，因此，研究喀斯特石漠化时空特征及演变规律，对石漠化治理有着重要的意义。以西南八省为研究区，利用归一化差分植被指数（Normalized Difference Vegetation，NDVI）、净初级生产力（Net Primary Productivity，NPP）、地表反照率（Surface Albedo）和坡度（Slope）数据，借助ArcGIS等软件平台，分析石漠化在不同的坡度、土地利用和生态保护区内的变化。结果显示：（1）轻度和中度石漠化是西南主要的石漠化类型。从空间分布来看，石漠化发生分布面积最广的是贵州，其次为云南和广西。（2）从不同土地利用来看，2000-2015年间无石漠化面积最多，潜在石漠化次之。石漠化主要发生在耕地和林地两种土地类型上，其他用地上石漠化发生面积最少，但是极重度石漠化在其他用地上的发生比例很大，平均在11%左右。（3）从不同坡度来看，石漠化严重程度不随坡度的增加而加剧，在坡度6°-25°之间石漠化发生面积最大。（4）从生态保护区来看，2000和2015年西南喀斯特生态保护区是石漠化面积分布最多的区域，分别为27481.86 km²和21738.65 km²。最少的是大别山山地生态功能保护区，从变化量来看，增加最多的是三峡库区，增加1641.22 km²，减少最多的是西南喀斯特生态功能保护区，减少5743.22 km²。（5）利用NPP、NDVI、地表反照率和坡度能较精准的反演石漠化，其反演权重依次为0.33、0.42、0.15和0.1。研究时段内，西南生态环境逐渐得到改善。