Living in an amphidromous world: Perspectives on the management of fish passage from an island nation

1. Amphidromy is a form of migratory life history typified by the reproduction of fish in freshwater environments, the early downstream dispersal of post‐hatch larvae to marine environments, and the return of small‐bodied young juveniles to freshwater environments for growth to adulthood. Island freshwater fish communities are frequently dominated by fish species with amphidromous life histories.
2. Amphidromous life cycles leave fish communities highly susceptible to habitat modification and disruptions to connectivity across marine and freshwater environments. This means that managing waterway connectivity is fundamental to their conservation; however, the unique and often geographically restricted amphidromous communities that characterize many small island nations have received little consideration in the development of strategies for the management of fish passage.
3. The ecology and locomotory capabilities of amphidromous species are often poorly studied, partly because their small size at migratory life stages renders current state‐of‐the‐art in situ biotelemetry methods unsuitable. The small size of fish also means that seemingly small obstructions can severely impede migrations.
4. The steps necessary to advance the management of fish passage for island fish communities are: curating and maintaining barrier inventories; evaluating barrier permeability; developing effective barrier mitigation options; and prioritizing restoration and conservation efforts.
5. New methods for understanding the ecology and locomotory capabilities and behaviour of amphidromous fishes are required to advance the management of fish passage for island fish communities. Fish passage solutions that imitate natural streams, such as those promoted in new guidelines in New Zealand, may be the most effective way of improving waterway connectivity; however, integrated approaches to freshwater fish conservation that account for meta‐population dynamics, in combination with the management of fish passage, are necessary to optimize conservation outcomes for amphidromous species.

     

Conversion of cropland into agroforestry land versus naturally-restored grassland alters soil macro-faunal diversity and trophic structure in the semi-arid agro-pasture zone of northern China

Restoration of cropland(termed 'Farm') after abandonment including shrubs(termed 'Shrub'),trees(termed 'Tree') and natural grassland(termed 'Grass') has become a routine process aimed to improve land productivity and control desertification. During this restoration process, soil macro-faunal diversity, and trophic structure were investigated at four types of sites(Farm, Shrub, Tree, and Grass)during growing season in the semi-arid agro-pasture zone of northern China. Results indicated that the Staphylinidae family was found to dominate at the Grass, Shrub, and Tree sites, whiles larval Pyralidae individuals were found at the Grass site only. The density of the omnivores(i.e., Formicidae family) was significantly(P<0.05) greater at the Grass site than at the Tree and Farm sites. The total density and richness of predator and phytophages were found to be markedly(P<0.05) greater at the Grass site than at the Farm site. Meanwhile, we found the taxon richness of predators was significantly(P<0.05) higher at the Shrub site than at the Farm and Tree sites. Compared with the Farm and afforested Shrub/Tree sites,the Grass site had greater density, taxon richness, and Shannon index(P<0.05). In conclusion, natural restoration of abandoned croplands toward grassland was an effective strategy relative to artificial afforestation for improvement of soil biological diversity. Moreover, planting shrub is a preferable measure in abandoned croplands for land development in the semi-arid agro-pasture zone of northern China.     

基于元胞自动机模型的土地利用情景模拟与驱动力分析

土地利用格局的形成过程比其最终形成的结果更为重要。本文以哈尔滨市双城区为例，利用不同时期的土地利用数据，在土地利用变化关键驱动因素分析的基础上，选取了对土地利用变化影响较大的距离变量、邻近土地利用类型数量、单元自然属性、社会经济因素等4方面14个驱动力因子，建立了基于元胞自动机(CA)与人工神经网络(ANN)相结合的土地利用空间格局模拟模型。在此基础上，对研究区自然禀赋、社会经济快速发展、基本农田保护及土地利用规划等不同情景驱动机制下的土地利用空间格局进行了时空模拟，以此解析土地利用变化过程与驱动力因素的响应关系。模拟结果显示：自然禀赋情景下，各地类变化趋势与现在保持一致；在社会经济快速发展情景下，建设用地面积增加明显，主要由旱地和其他用地转入；在基本农田保护情景下，耕地面积比较稳定，各地类变化趋势较为缓和；在土地利用规划情景下，各地类变化较为合理，兼顾耕地保护和经济发展。研究结果显示，该方法对哈尔滨市双城区土地利用格局变化的驱动机制具有较好的解释作用。     

Impact of newly introduced perennial bioenergy crops on soil quality parameters at three different locations in W‐Germany

The land areas used for bioenergy crop cultivation are increasing across Europe. For several years now, various perennial crops have been cultivated, including Miscanthus , switchgrass and reed canary grass, and the newly introduced cup plant, giant knotweed, tall wheatgrass, virginia mallow, and wild plant mixtures. We investigated the impact that many of these perennial bioenergy crops (PECs) have on the soil organic C and N pools, microbial properties, and earthworm activity at three different study sites in W‐Germany with varying soil conditions after an experimental period of five years. Silage maize (Zea maize ) in rotation with green rye (Cecale cereale ) or Triticale was used for comparison (= annual energy crops; AEC). The overall intention of this study was to gain insights into the future trends of soil quality with changes in land‐use towards bioenergy production. Our results emphasized that in general, soil quality was improved through the cultivation of perennials. For example, after five years of investigation, the mean soil organic carbon contents increased, on average, by 1–2% at two of the three study sites, the soil microbial biomass increased from 13% (virginia mallow) to 27% (tall wheatgrass) (p < 0.05) compared to AEC treatment and the mean earthworm activity (cast production) was significantly improved in PECs compared to AEC. These trends were mainly found in silty to loamy soils, but the results were slightly different in sandy soils and dry climate conditions. We suggest that this might be traced back to unfavourable growing conditions for perennial crops during the first years of establishment. To our knowledge, this is the first comprehensive field investigation of the impact of these newly introduced perennial crops on soil quality indicators that considers various site‐ and soil‐specific growth conditions.     

基于社会燃烧理论的耕地非农化驱动因素分析

中国耕地非农化现象日益明显。基于社会燃烧理论分析了耕地非农化的驱动原理,建立了耕地非农化影响机制模型,并运用SPSS 19.0软件对分类驱动因素进行了主成分及回归分析。结果表明,人均GDP和固定资产投资所占GDP比重等经济发展变量对耕地非农化水平的正向影响最大;粮食单产、总产等农业技术变量对耕地非农化水平具有最大的逆向影响。最后在模型拟合的基础上提出了相应的对策与建议,旨在为合理有效保护耕地提供参考。     

RCPs气候情景下三江平原典型流域耕地动态模拟

选取三江平原典型流域挠力河流域为研究区,以1990、2002和2014年3期Landsat影像、DEM数据和社会经济统计资料等多源数据为基本信息源,结合3S技术,运用FLUS模型定量模拟代表性浓度路径情景系列(RCPs)下耕地动态变化特征。结果表明:24 a间挠力河流域的旱地面积变化幅度较小,水田面积持续增加,1990—2002年水田扩张剧烈,2002—2014年扩张速度趋于缓和;3个时点的旱地均沿东北-西南轴方向进行分布,主轴沿顺时针缓慢旋转,空间变化稳定,分布范围逐渐减小。水田沿东北-西南走向分布,1990—2002年其主轴逆时针旋转,后顺时针旋转至45.31°,整体分布较为离散,极化特征不明显;通过对比不同空间分辨率及时间尺度下模拟精度,确定最优模拟空间分辨率为200 m,最优模拟时间点为2038年;MESSAGE气候模式下,未来挠力河流域的旱地面积先减少后增加,水田继续维持扩张态势,2029年后面积将以2%速度逐年下降,其分布将更加聚集,主轴沿顺时针旋转,重心逐渐向东北方向进行偏移;AIM气候模式下,气候波动对水田的影响程度大于旱地,旱地面积持续缓慢增加,水田面积在波动中下降,空间分布的极化特征突出。     

基于EnKF-3DVar模型的海淀区地表温度模拟

以城市化程度较深的北京市海淀区为研究区,基于2005年、2010年和2015年的遥感影像数据,利用基于影像(IB)的算法反演城市地表温度空间分布。将数据同化算法EnKF-3DVar与CA/Markov模型集成,将海淀区的多年平均臭氧浓度空间分布数据同化进行城市地表温度的模拟预测。结果表明海淀区的城市地表温度10年间呈现先下降后上升的趋势,但总体呈现下降趋势,其中2015年的平均温度为31.139 3℃。引入EnKF-3DVar的预测模型能够显著提升模型的模拟精度,所预测的2015年的数据结果 Kappa系数达到0.821 6。在有城市公园绿地的模式下,地表温度高值区呈现缓解趋势,在无城市绿地公园的模式下,城市地表温度高值区呈现出明显的扩张趋势,最高温度达到了56.142 3℃,城市生态绿地对于城市地表温度的空间分布影响巨大,合理布局城市绿地公园意义重大。     

基于物元分析的区域土地生态安全评价方法研究

现有土地生态安全评估涉及大量的行政区社会经济数据，评价方法常常忽略单个指标对综合值的影响程度，本文构建了基于地质-水文-生物（GHB）的生态安全评价体系，提出基于物元分析的区域土地生态安全评价方法，以大安市为例进行土地生态安全水平定量评价。评价得出大安市87.45%的土地生态安全水平处在安全级，但整体生态安全水平仍有较大提升空间；单个指标分析表明，大安市土地生态建设重在推进重要水源管理、提高植被覆盖度、减少矿产开采量和减少地下水开采量等工作。研究结果表明，物元分析能够揭示单个评价指标的分异信息，对大安市生态安全的改善有一定指导意义。