顾及生态系统连通性的永久基本农田划定

在生态文明背景下，探索兼顾耕地资源保护与生态系统维护的永久基本农田划定方法对构建国土空间开发新格局具有重要意义。该研究通过最小累积阻力（minimum cumulative resistance，MCR）模型与电路理论等在识别生态源地、生态廊道和“踏脚石”基础上，将土地评价与立地条件分析（land evaluation and site assessment，LESA）方法及未来土地利用模拟（future land use simulation model，FLUS）模型相结合构建了一套顾及生态系统连通性的永久基本农田划定方法，以期为十堰市永久基本农田划定提供一定理论参考。结果表明：1）十堰市生态源地共计26个，主要以林地与水域为主，分布在南部和中部山地丘陵区；生态廊道共计66条，集中分布在竹溪县、竹山县、房县等境内；“踏脚石”共计121个。2）基于LESA方法划定的永久基本农田虽然满足了目标需求量，但与重要生态系统连通性用地存在严重冲突，与生态源地、生态廊道、“踏脚石”冲突面积分别为1772.64、4274.19、391.86 hm²。3）顾及生态系统连通性的永久基本农田划定方法，有效避开了划定的永久基本农田对生态源地、生态廊道与“踏脚石”等侵占，而且满足了未来城市用地增长需求，同时划定的永久基本农田质量高，集中连片性强，农田形状也较规则，便于机械化耕作，对保障中国粮食安全，推进农业供给侧结构性改革，实现乡村振兴具有重要作用。     

图的平均边连通度

证明了-K（G）≤-λ（G）≤-δ（G），给出了给定顶点数、边数、边连通度的图的最大平均边连通度的计算公式．     

城市潜在绿色廊道构建方法——以常州市为例

在RS和GIS的支持下,利用遥感影像分类、斑块连通性分析和耗费距离模拟等方法形成一套完整的城市潜在绿色廊道构建体系。首先采用最优指数(OIF)和决策树(QUEST算法)获取城市绿地斑块空间布局,分析绿地斑块间的连通性;然后利用Spearman秩相关等统计方法确定不同连通指数对连通阈值的敏感程度,优选最稳定的连通指数划分绿地斑块的重要性等级,将具有较高重要性值的斑块作为绿地"源"和"目标";最后选用频率比方法改进耗费距离模型的成本表面,在不同空间尺度下,情景模拟城市潜在绿色廊道的空间布局,并对模拟结果进行定量分析与评价。结果表明:最优指数结合决策树方法的分类总精度为90.35%,Kappa系数为0.86,提取绿地面积占城市总面积的22.88%,大面积绿地斑块主要分布在滆湖的西部和太湖的北部;整体连通指数(IIC)具有较高的稳定性,在200～2400m的距离范围内,其dIIC的Spearman秩相关系数变化值最低(0.21);在600m的距离阈值下,以dIIC值大于1%作为标准,确定竺山斑块为绿地"源"及7个主要的绿地斑块为"目标";在不同空间尺度下,模拟的潜在绿色廊道的变形系数ξ值相近(1.28),其空间格局受研究尺度的影响较小。最后进一步探讨该方法体系实践的可行性,为城市绿地系统规划和建设提供科学合理的参考和依据。     

道路侵蚀研究的进展与展望

[目的] 分析目前道路侵蚀研究中所存在的问题及未来亟需关注的研究方向,为防治流域土壤侵蚀和保障流域生态环境安全与高质量发展提供重要依据。[方法] 通过查阅文献,从道路侵蚀的界定、道路侵蚀的特征及影响因素,道路侵蚀研究方法等方面进行总结和分析。[结果] 目前关于道路侵蚀研究存在的主要问题表现在： ①研究方法尚不成熟,模拟降雨/冲刷试验法应用较广,实地监测法和模型模拟法应用较少;②研究内容多局限于道路原位侵蚀效应,而鲜少涉及道路异位侵蚀效应;③道路侵蚀防治研究大都围绕硬化道路进行,土质道路相关研究薄弱。[结论] 未来关于道路侵蚀的研究应结合道路侵蚀特点及其影响因素,运用连通性的概念,探明道路存在对路域及整个流域中的径流泥沙输移的“开关”作用,揭示道路对流域内径流及泥沙的输移机制的影响,并因地制宜地提出硬化道路的维护管理措施和土质道路的侵蚀防治措施。     

Comparing static versus dynamic protected areas in the Québec boreal forest

Conservation planning is often based on static mapping of species’ ranges or habitat distributions. Succession and disturbance alter, however, habitat quality and quantity through time especially under global climate and land use change scenarios; hence, static protected areas may not ensure habitat persistence and species survival. Here, we examined the relative merits of static and dynamic (floating) protected areas for the conservation of American marten (Martes americana) habitat in a dynamic boreal forest of Québec (Canada). Forest dynamics were modeled using a spatially-explicit landscape disturbance model and protected areas were selected based on the quality and compactness of marten home ranges using MARXAN. Static protected areas were fixed in space during 200 year simulations of boreal forest dynamics, while dynamic protected areas were re-located every 50 years to track dynamic habitat. Dynamic protected areas supported more high quality home ranges through time than static protected areas. The locations of dynamic protected areas were constrained, however, by the highly fragmented forest patterns created through logging and fire in unprotected areas. Our findings emphasize the often-overlooked point that if dynamic conservation planning is to be successful in the long term, the landscape matrix quality surrounding protected areas must be managed in such a way that options remain when it comes to re-planning.     

Evaluating hedgerow corridors for the conservation of native forest herb diversity

The maintenance of connecting habitats such as hedgerows in production landscapes could become increasingly critical as species migration is expected to accelerate with climate change. Species of particular conservation interest that could benefit from connecting habitats especially in agroecosystems are native forest herbs. It is still unclear, however, which hedgerow habitats have the best potential of supporting diverse forest herb communities, making it hard to target particular structures for conservation. Our objective was to identify the local and landscape characteristics of hedgerows that could help predict their potential at maximizing the richness, abundance, and diversity of native forest herbs of temperate deciduous forests of North-East America. We used multiple regression, Moran’I correlograms, and conditional autoregressive models to assess the effect of landscape and historical variables (hedgerow age, amount of adjacent forest cover, connection to forests and other hedgerows) and of local variables (hedgerow width, canopy cover, cover of other species) on the response variables. The results show an increase in forest herb diversity and abundance in hedgerows with time and with increasing nearby forest cover. Local factors such as greater width and reduced cover of other species also relate to a greater abundance and diversity of forest herbs in linear habitats. The fact that forest herb communities can reassemble in hedgerow corridors with time implies that there could be long-term benefits in maintaining and even creating linear habitats where there is a pool of dispersing forest herbs.     

未成熟芒果的改进YOLOv2识别方法

在果园场景下,由于光照的多样性、背景的复杂性及芒果与树叶颜色的高度相似性,特别是树叶和枝干对果实遮挡及果实重叠,给未成熟芒果检测带来极大的挑战。本文提出果园场景下未成熟芒果的改进YOLOv2检测方法。设计新的带密集连接的Tiny-yolo网络结构,实现网络多层特征的复用和融合,提高检测精度。为克服遮挡重叠果实检测困难,手工标注遮挡或重叠芒果的前景区域,然后用样本的前景区域训练YOLOv2网络,减小边界框内非前景区域特征的干扰,增强对目标前景区域卷积特征的学习。并以扩增的数据集,采用增大输入尺度和多尺度策略训练网络。最后,对本文方法进行性能评价与对比试验。试验结果表明,该方法在测试集上,芒果目标检测速度达83帧/s,准确率达97.02%,召回率达95.1%。对比Faster RCNN,该方法在杂物遮挡和果实重叠等复杂场景下,检测性能显著提升。     

The effects of soil moisture variability on the vegetation pattern in Mediterranean abandoned fields (Southern Spain)

The demographic pressure decrease in Southern Spanish Mediterranean mountainous areas in the mid twentieth century led to the abandonment of agriculture and rupture in the geo-ecosystem balance which had existed until then. Since then, different phases of recovery have been put into action to return the landscape to its earlier natural condition according to climate and soil degradation state after the abandon. In Mediterranean climatic conditions (between subhumid and semi-arid regimes), degraded soil recovery has followed different tendencies rendering the landscape in heterogenic and complex one. This heterogeneity has manifested in the vegetation pattern of abandoned fields. In this paper, we analyze the state of three abandoned fields situated under different Mediterranean climatic conditions from the recovery point of view by means of monitoring the effects of spatial and temporal variability of soil moisture in the vegetation pattern over a period of two years sampling (Nov. 2002–Nov. 2004). The results showed that: i) more annual rainfall volume did not guarantee success in the biological recovery of the system due to the influence of other factors such as the degradation state of the soil post-abandonment or the steep slope gradient; ii) soil moisture variability tended to play a more important role in affecting vegetal cover in semi-arid conditions; and iii) in dry climatic conditions the system demonstrated greater signs of recovery (greater biodiversity).     

南京东郊生物多样性保护核心绿地分析方法研究

以南京东郊绿地系统为对象,在ArcGIS 9.2、连通性分析软件conefor sensinode 2.2的支持下,以2005年南京东郊SPOT 5卫星影像、2005年南京快速交通矢量化文件为主要信息源,采用巧合概率指数(LCP)、整体连通性指数(IIC)、可能连通性指数(PC)和重要值(dI)等评价指标,分析研究区内的绿地斑块等级、连通性和空间结构。在此基础上,利用连通性指数确定生物多样性保护核心绿地区域。结果表明:以青龙山为主的24个绿地斑块,面积占研究区绿地斑块总面积的35%,构成了研究区域生物多样性保护的核心绿地;核心绿地斑块平均大小、最大斑块占景观面积比例2项指标分别比研究区高出0.31、59.46,景观边缘密度、景观形状指数2项指标分别比研究区低13.55、6.59;宁杭公路和沪宁高速2条快速通道对核心绿地的屏障作用最大。提出快速交通影响下南京东郊生物多样性保护核心绿地的管理对策。     

Geochemical tracing and spatial evolution of the sediment bed load of the Romaine River,Québec,Canada

A four-reservoir hydroelectric complex which is projected on the Romaine River, in eastern Québec, Canada, will likely lead to the complete settling of the sand-size bed load of the river. In order to characterise the present river bed load sources, sediment transport and sedimentary connectivity, a study was conducted to document the compositional continuum of the lower 300 km portion of the river. Bed load samples were collected during the late summer low water period and ICP-MS geochemical analyses of the light and heavy mineral portions were conducted. Principal component analysis of the results successfully identified a series of distinctive geochemical domains. Multivariate Euclidean distance coefficients were also calculated between consecutive samples along the river revealing major bed load compositional breaks. These results indicate a longitudinal fractionation of the bed load along the 300 km course of the river. This is further supported by the sedimentary budget calculated from the annual sedimentary input derived from erosion rates of the river banks, from sediment bed load measurements at three gauging stations and from calculated bed load transport capacity at these three locations. It appears that significant sediment accommodation space is available on the upper course (250 km) of the Romaine River, in spite of the fact that this river has drained highly sediment-laden meltwaters from the receding Laurentide Ice Sheet, some 10 ka ago. This accommodation space leads to the renewal of the bed load due to recurrent partial to complete sedimentation. The major part of the bed load reaching the Romaine River mouth originates from the lower 50 km of the river course.