Macroalgal assemblages of disturbed coastal detritic bottoms subject to invasive species

Characteristic flora and fauna that are highly sensitive to disturbances colonize coastal detritic bottoms in the Mediterranean Sea. In the present study, a comparison of the assemblage composition and colonization by invasive macroalgae was made between two coastal detritic macrophyte assemblages, one dominated by rhodoliths (free-living non-geniculate Corallinales) and the other dominated by fleshy algae, in an area that has been exposed to important levels of anthropogenic disturbance, mainly pollution (including changed sedimentation regimes) in the recent past (bay of Marseilles, France). In comparison with less strongly impacted Mediterranean regions, the macrophyte assemblages in the bay of Marseilles were characteristic in terms of species identity and richness of coastal detritic macrophyte assemblages. However, extremely low species abundance (cover) was observed. As far as invasive species were concerned, Caulerpa racemosa var. cylindracea was only abundant in the rhodolith assemblage whereas the two invasive Rhodophyta Asparagopsis armata and Womersleyella setacea were mainly found in the fleshy algae assemblage. The seasonality observed in the Rhodolith assemblage seemed to be related to the development of C. racemosa var. cylindracea and did not follow the typical pattern of other Mediterranean assemblages. This study represents the first study of coastal detritic assemblages invaded by C. racemosa var. cylindracea.     

长江河口深层软土含盐特征及其沉积环境分析

软土的含盐特征是地基设计的一个重要指标,含盐特征主要受沉积环境控制,往往具有较强的地域性。以长江河口北翼海陆交互相软土为研究对象,采集多组土样进行室内试验,进行土体含盐特征、参数相关性及沉积环境分析。研究结果表明,软土含盐特征为NaCl型,含盐量均值为0.613%,以弱盐渍土为主,占比85.4%。含盐量、Cl−含量、Na+含量、K+含量峰度检验符合正态分布,但偏度检验值坐落在拒绝域,不属于正态分布。其他离子假设检验偏度和峰度检验均不符合正态分布。软土含盐量与Cl–含量相关性最高,与除了Ca2+含量、${\rm{CO}}_3^{2-} $含量之外的离子相关性好。软土Cl–含量与含盐量、${\rm{SO}}_4^{2-} $含量拟合以乘幂效果最佳;Cl–含量与Na+、Ca2+、Mg2+、K+、${\rm{HCO}}_3^- $含量拟合以多项式拟合效果最佳。软土环境沉积为碱性。软土钠吸附比平均值为54.35,与标准海水的钠吸附比接近,说明软土层含盐特征保留了海水特征。随着深度的增加,软土钠吸附比有减小的趋势,这与软土形成时间有关,软土形成时代越老,渗透淋滤的时间越长。软土中Sr/Ba远大于1,说明土体沉积时受到了海水作用。软土浸出液中的γMg/γCa远高于地表淡水的γMg/γCa背景值,说明土体沉积时受到海水入侵。引入海水混合模型,计算了海水混合比例。海水混合比的低值主要分布于西部远离海岸区,该区土体沉积主要受长江河水控制。海水混合比的高值主要分布在滨海地区,该区土体沉积主要受海侵控制,海相属性更重。     

长江流域外来鲟入侵风险评估、适生区预测及影响因素分析

长江流域外来鲟的养殖规模庞大,养殖逃逸成为外来鲟进入长江流域的主要途径,影响本地鲟种群生存。根据世界鱼类数据库(FishBase),10种主要养殖的外来鲟中,西伯利亚鲟已被列为德国和奥地利的入侵物种,匙吻鲟已被列为白俄罗斯的入侵物种。为了评估长江流域外来鲟的入侵风险,量化流域内入侵风险最高的外来鲟的适生区,本文使用水生物种入侵性筛查工具(AS-ISK)评估10种主要养殖的外来鲟和5种相关鱼类(虹鳟、尼罗罗非鱼、斑点叉尾鮰、鲮和丁鱥)的入侵风险;使用最大熵算法,基于当前和未来时期(2021—2040年)气候模式下的生物气候变量以及海拔,对于入侵评分最高的外来鲟在流域内的适生区进行预测与分析。结果表明,匙吻鲟在外来鲟中入侵评分最高,表明其在长江流域入侵风险最高。适生区预测时,最热季降水量、年降水量、最热月份最高温度、最冷月份最低温度、昼夜温差的月平均值和降水季节性变异系数是影响匙吻鲟在长江流域分布的主要变量。当前时期,匙吻鲟在长江流域中下游地区具有较大范围的适生区,主要包含湖南、湖北、安徽和江西等省份的部分地区,其中Ⅲ级适生区(高适生区)面积约为2996.8 km²;...     

草地退化杂类草入侵遥感监测方法研究进展

近年来,受全球气候变暖及日趋频繁的人类活动的共同影响,我国草地生态系统出现了不同程度的退化,成为草地生态学界的研究热点。本文较系统总结了草地退化、杂类草入侵遥感监测方法的应用进展,指出了常规草地退化遥感监测方法的不足,并展望了今后的发展方向。研究发现草地退化在群落尺度上往往表现为优质牧草种类减少,杂类草种类增加。在草地退化过程中,杂类草侵入,往往导致植被覆盖度增加,因而传统的基于植被覆盖度、生产力和产草量下降的草地退化遥感监测方法,无法反映草地退化在植被种群方面的变化特征,尤其是杂类草入侵的草地退化过程。而目前基于高光谱数据的草地退化杂类草入侵监测方法,结合地面光谱测定和对退化草地物种特征微弱光谱差异的定量分析,能有效识别群落中杂类草种类,并反演出占群落的面积比例、高度和盖度等,可为草地退化监测及其治理提供群落演替过程及其态势的重要指标,为草地退化监测提供新的遥感技术方法。     

Altered mayfly distribution due to strong interactions with alien rainbow trout in Andean streams of Patagonia

Nesameletidae is a Southern Hemisphere ephemeropteran family with large-bodied nymphs that are swimming grazers, traits that make aquatic invertebrates vulnerable to visual predators. Metamonius anceps is the sole representative of this family in South America and its present known distribution along the Southern Andes is mostly restricted to headwater streams, usually with clear and well-oxygenated waters.We analyzed their spatial distribution in relation to the presence of the exotic predator rainbow trout (Oncorhynchus mykiss), which is the only fish species in many small Andean Patagonia streams. We measured mayfly abundance in the benthos and drift in reaches with and without fish (the latter being reaches upstream of waterfalls that prevent trout access) in three catchments of Nahuel Huapi Lake basin at the Nahuel Huapi National Park, Argentina. We compared nymphal abundance and body size at the habitat scale and at the reach scale, and nymphal presence and body size in trout diet.A multivariate analysis of physical stream features showed that habitat/reaches with and without fish had similar abiotic characteristics. In no fish sites, nymph density ranged between 44 and 180 m⁻² while in fish sites they were 0–3 m⁻². In one stream nymphs drifted mainly during the day and ∼400 indiv. day⁻¹ were estimated to enter the site with fish. However no nymphs were collected drifting 200 m below the waterfall (the reach with fish). Observations on the diet of rainbow trout also supported the ongoing strong interaction between this mayfly and the trout. M. anceps is a highly vulnerable prey as no permanent populations were found in study reaches with the exotic predator established. Our study emphasizes the potential of natural physical barriers to stop invasive fish having access to headwaters allowing them to harbour natural populations of the most trout-susceptible species supporting pristine ecosystem conditions.     

不同水化学条件下循环侵水砂岩劣化规律研究

岩石力学性质的损伤对于工程结构的稳定造成严重影响,尤其是废弃露天矿坑作为尾矿库使用,蓄水与排水导致库岸边坡岩体长期受到复杂水化学环境与循环侵水的耦合作用。为模拟复杂水化学环境与循环侵水的耦合作用对岩石损伤影响,设计了砂岩在酸、中、碱性三种环境下的循环侵水试验,并通过常规三轴压缩试验分析岩石力学参数的弱化规律。研究结果表明：（1）砂岩峰值强度随围压增大呈递增趋势,随循环侵水次数增加呈降低趋势,且峰值强度按pH值排序为7>10>4;（2）砂岩孔隙率随循环次数增加呈增长趋势,其变化率呈降低趋势,且孔隙率按pH值排序为4>10>7,pH=4和pH=10环境中孔隙率明显大于pH=7环境中的孔隙率,表明pH=4和pH=10环境中砂岩同时发生水解反应与化学反应两种劣化,使得孔隙率增大;（3）砂岩粘聚力c和内摩擦角φ呈劣化递增趋势,0次到5次循环阶段,c和φ的劣化程度最大,5次到20次循环阶段,c和φ劣化的趋势逐渐减缓,且c值和φ值按pH排序为7>10>4;（4）对砂岩粘聚力c和内摩擦角φ拟合方程微分后得到微分方程,归一化处理后定义其系数为砂岩劣化系数,得到c和φ的劣化系数按pH排序均为4>10>7,并分别建立c和φ与pH值、循环次数的双变量拟合函数表达式。     

植物入侵与其它全球变化因子间的相互作用

全示变化包括大气臭氧层的损耗，CO2等温室气体排放增加，气候增暖，土地利用和覆盖变化。生物多样性丧失以及外来种入侵等因子，植物入侵与其它全球性变化因子间有复杂的相互作用；大气CO2浓度增加将导致C3植物比C4植物竞争力更强，低营养生态系统会变得更易入侵，变化的气候条件下，许多种类面临迁移或外来问题，土壤变暖也将使许多休眠植物改变习性，增加紫外辐射将使一些植物的生长和生产力减少。进而会对其竞争和生态过程有间接的影响，CO2浓度升高时硫酸盐的沉积可以增强C3植物的竞争力，较致密的生境破碎化后，一些入侵种可通过边缘进一步向群落内部入侵，增加或降低典型干扰的频率和强度及引入新干扰，能促进外来种的定居和扩散，植物，动物和微生物间的关系改变对植物入侵的速率和效果有明显影响，世界性贸易和运输为生物的入侵提供了条件。     

2009年5月9—10日华北南部强降水天气分析

应用常规天气图、地面加密降水观测资料、探空资料和NCEP/NCAR 1°×1°再分析资料,对2009年5月9—10日华北南部大范围持续性强降水天气过程进行分析研究。结果表明,强降水是在冷空气与西南暖湿气流交汇的过程中产生的。500 hPa为槽前西南气流,850～700 hPa为东北—西南向切变线,地面冷锋转变为静止锋,之后生成弱的气旋波向东南方向移动消失。大气高温高湿,中层为弱的对流不稳定和对称不稳定。冷空气从底层锲入,一方面与暖湿气流汇合产生辐合上升,另一方面抬升暖湿气流,使上升运动加强,降水增幅。中高层空气暖湿,0℃层较高,以强降水天气为主,伴有雷电。由于暖湿气流较强,冷空气在南下过程中逐渐减弱,速度减慢,冷暖空气在黄河下游长时间对峙,强降水持续时间长。     

安徽刘桥二矿太灰水突水性分析

对刘桥二矿煤层开采时太灰水的突水性分正常块段和构造破坏块段两方面进行了分析,并用比拟法和解析法计算出了太灰水突水时的最大突水量。     

Invasion and spreading of Cabomba caroliniana revealed by RAPD markers

Applying randomly amplified polymorphic DNA （RAPD）, the genetic variation of Cabomba caroliniana Gray （cabomba or fanwort）, a new alien plant in China, was analyzed in this paper. Total 143 bands, including 47 polymorphic bands, were amplified from 23 primers in 20 samples. The sampling distance was large, but its genetic diversity was low. The main results were that： （1） Cabomba, which grew and dispersed mainly in fragment, was an abundant and dominant species in freshwater, and its main dispersal mechanism was vegetative reproduction. （2） Cabomba was originally introduced into China as an aquarium submerged plant. Somehow, those discarded cabomba became invasive species in the areas of Hangzhou, Shanghai, and Meicheng, and other places. （3） Although the level of genetic diversity in cabomba was low, their rapid dispersion and propagation could seriously harm to local aquatic community. Therefore, specific measure should be used to control cabomba from uncontrolled spreading and damage to local vegetation communities.