Connectivity of the Coarsest Fraction in Headwater Channels: Imprints of Fluvial Processes and Debris‐Flow Activity

Some steep headwater streams of the mid‐mountains landscape of the flysch belt of the Western Carpathians are affected by debris flows. Connectivity of the largest boulder and cobble fractions has been evaluated in steep streams found in the transitional zones between the hillslopes and alluvial cones of similar lithology and watershed morphometry. Two longitudinal profiles affected by past debris‐flow activity and two longitudinal profiles void of such processes were selected. In the first case, active channels were characterised by the presence of the coarsest fraction, while a downstream trend of sediment coarsening or fining lacked any influence of contemporary fluvial processes and sediment supply. In addition, debris‐flow‐affected streams showed greater differences between the middle axis of the coarsest particle and the particle‐size index including the lengths of all three axes, which is most likely the result of limited active fluvial transport. All the studied streams demonstrated general downstream fining of the largest particles, which resulted from local flysch lithology containing more resistant sandstones in the upper parts of the watershed. The trend of sediment fining was more rapid in the longitudinal profiles unaffected by past debris flows. These types of streams also showed adjustment of the coarsest bed fraction to contemporary processes in channels by sediment coarsening in incised reaches and sediment fining in depositional reaches as well as by downstream response to some lateral sediment inputs. The index of the unit stream power showed no correlation with the considered coarsest fraction in both fluvial‐dominated channels and debris‐flow‐affected channels.     

黑潮化学物质输入东海的途径与通量

在对黑潮水文特征分析的基础上,探讨了黑潮对中国近海化学物质输入途径,归纳总结了黑潮对东海生源要素、痕量元素、同位素及其他化学物质的输入特征,提出了黑潮对中国近海化学物质输入研究应着重关注的问题。主要的结论包括:吕宋海峡、中国台湾东北部及日本九州西南海域是黑潮向中国近海输送化学物质的3个关键区域;黑潮表层水向东海陆架的扩展、次表层水和中层水的涌升以及黑潮季节性流轴摆动是黑潮向东海输送化学物质的基本途径。黑潮主体生源要素的浓度随深度的增加而增大。黑潮对东海生源要素的影响夏季最弱、春季次之、秋冬季最强,其对东海生源要素的输入通量要远高于河流、大气等其他输入源,并且各水层中以中层水的生源要素输入通量为最大。痕量元素在黑潮主体的分布、对东海的输入通量等方面均表现出了与生源要素的差异,各痕量元素的分布及输入通量随痕量元素的不同而不尽相同,其中次表层水的涌升在对邻近海域痕量元素分布的影响中起到了重要作用。同位素可指示黑潮对东海陆架的入侵程度及变化规律,并与营养盐等有一定的相关性。黑潮是东海微量温室气体N2O,CH4等其他化学物质的重要输入源,进而对东海生态环境产生影响。进一步研究应着重从系统性外海观测、痕量元素及同位素等化学物质调查、黑潮对中国近海输入化学物质的控制过程等方面深入开展。     

Otolith microchemical evidence revealing multiple spawning site origination of the anadromous tapertail anchovy (Coilia nasus) in the Changjiang (Yangtze) River Estuary

The estuarine tapertail anchovy(Coilia nasus) is a high-value commercial fish. Estimating the spawning site or hatchery origin and habitat is essential for its conservation. This study aimed to determine the habitat use and life history characteristics of C. nasus from the Changjiang River Estuary. We investigated the environmental signatures of strontium(Sr) and calcium(Ca) in the otoliths of the collected specimens using electron probe microanalysis; additionally, we examined their gonadal mat...     

Assessment of connectivity in a water‐stressed wetland (Kaabar Tal) of Kosi‐Gandak interfan,north Bihar Plains,India

Landscape elements respond to the processes acting on them, and this response connects with neighboring landscape units. The propagation, superposition, and interference of these responses are functions of the connectivity among the landscape units. Such landscape units are referred to as ‘Connectivity Response Units’ or CRUs that are in turn influenced by topography and landuse/landcover (LULC). The CRUs are obtained by the application of diffusion‐kernel based smoothing technique over the connectivity potential maps. A framework has been designed using the CRUs to understand the impacts of changing LULC on the connectivity structure in a relatively flat terrain under pre‐ and post‐monsoon scenarios. The proposed framework has been applied to a water‐stressed wetland occurring in an interfan setting in north Bihar plains, eastern India. It has also been demonstrated that CRUs can be used as a viable option for understanding the seasonal and temporal dynamics of connectivity structure in and around such wetlands and for guiding a rehabilitation strategy for such fragile ecosystems. Copyright © 2017 John Wiley & Sons, Ltd.     

Better models are more effectively connected models

Water‐ and sediment‐transfer models are commonly used to explain or predict patterns in the landscape at scales different from those at which observations are available. These patterns are often the result of emergent properties that occur because processes of water and sediment transfer are connected in different ways. Recent advances in geomorphology suggest that it is important to consider, at a specific spatio‐temporal scale, the structural connectivity of system properties that control processes, and the functional connectivity resulting from the way those processes operate and evolve through time. We argue that a more careful consideration of how structural and functional connectivity are represented in models should lead to more robust models that are appropriate for the scale of application and provide results that can be upscaled. This approach is necessary because, notwithstanding the significant advances in computer power in recent years, many geomorphic models are still unable to represent the landscape in sufficient detail to allow all connectivity to emerge. It is important to go beyond the simple representation of structural connectivity elements and allow the dynamics of processes to be represented, for example by using a connectivity function. This commentary aims to show how a better representation of connectivity in models can be achieved, by considering the sorts of landscape features present, and whether these features can be represented explicitly in the model spatial structure, or must be represented implicitly at the subgrid scale. Copyright © 2017 John Wiley & Sons, Ltd.     

Variation in hydrologic connectivity as a result of microtopography explained by discharge to catchment size relationship

In hydrological terms, raised bogs are often approximated by simple models as in the acrotelm–catotelm concept. However, raised bogs are often characterized by a pronounced surface topography, causing large changes in connectivity of contributing areas on the bog. In this study, daily regression of measured discharges versus catchment areas is used to quantify the impact of surface topography on catchment connectivity within a raised bog. The resulting coefficient of determination shows the strength of the relationship between the discharge and catchment area over time under different hydrological conditions. Monitoring of discharge, water table, transmissivity, and basic weather data on a raised bog (1.9 km²) in eastern central Estonia took place from May 2008 to June 2010. Contributing areas, calculated based on the outlet's discharge volume (V _Q ) divided by the net precipitation volume ( ), of the outlet containing the central pool‐ridge system varied between 1×10^?3 and 0.7 km², suggesting significant differences in connectivity between hydrological events. Correlation between discharge and theoretical catchment size was high (R ²>0.75) when the water table was close to the surface (less than 5 cm below peat surface), and consequently, transmissivities were also high (up to 1,030m²d^?1), which led to connectivity of local storage elements, such as pools and hollows. However, a water table below this threshold resulted in large parts of the catchment being disconnected. The importance of water table depths on catchment connectivity suggests the need to reconsider the hydrological concept of raised bogs; to incorporate these shallow flow components and better understand residence time and consequently transport of solutes, such as DOC, from patterned peatlands.     

致密储层源储结构对储层含油性的控制作用——以鄂尔多斯盆地合水地区长6～长8段为例

鄂尔多斯盆地长6～长8段致密油是中国典型的致密油分布区。源储紧密接触是致密油的典型特征与成藏条件。致密油层非均质性强,石油运移多以垂向短距离为主。已有研究表明,储层非均质性是影响鄂尔多斯盆地合水地区剩余油分布的重要因素,但是目前对合水地区储层含油性影响因素的研究很少。通过分析合水地区长6～长8段源储结构及其与含油性的关系,研究其对储层含油性的控制作用。结果表明:合水地区长6～长8段源储结构复杂,长7段为源储一体型岩性组合,可细分为源夹储型、源储互层型与储夹源型3种类型,长6与长8段为研究区主要储层,与烃源岩形成邻源型岩性组合,细分为源储接触型、源储过渡型与源储间隔型3种类型;长7段源夹储型岩性组合的含油性最好,长6与长8段源储接触型岩性组合的含油性最好,最有利于致密油聚集;长6～长8段形成干酪根网络→孔隙+微裂缝型、干酪根网络+构造裂缝→孔隙+微裂缝型两种石油运移通道组合,为致密油充注提供有利的通道网络。     

水系连通变异下荆南三口河系水文干旱识别与特征分析

为揭示水系连通变异下荆南三口河系水文干旱演变特征,运用荆南三口河系五站1956-2016年的月径流量数据,采用游程理论识别该河系水文干旱特征变量,并运用Kolmogorow-Smirnov优度检验法选出干旱历时、干旱强度和峰值的概率分布函数,构建出水文干旱特征联合分布Copula函数,对水系连通变异下该河系水文干旱特征进行深入研究。结果表明：① 1989年为荆南三口河系（1956-2016年）水系连通变异分割点;② 该河系连通性变异前后水文干旱特征均发生显著变化,水文干旱事件发生的次数增多,干旱历时增长,干旱强度增大,峰值增高;③ 各站点的相同单变量重现期下二维联合重现期在水系连通变异前基本上均比水系连通变异后长,二维同现重现期在水系连通变异前均比水系连通变异后短;④ 水系连通变异后,该河系水文干旱历时、干旱强度和峰值呈现增加趋势,且在相同单变量重现期的情况下,干旱历时更长,干旱强度更大,峰值更高;⑤ 水系连通变异后水文干旱特征的变化幅度与变异前存在差异,不同河系其水文干旱特征的变化幅度不同。     

西南地区滇金丝猴潜在优先保护区与保护网络识别（英文）

In Southwest China, five Nature Reserves(NRs)(Mangkang, Baimaxueshan, Yunling, Habaxueshan, and Yunlongtianchi) play a key role in protecting the endemic and endangered Yunnan snub-nosed monkey(YSM)(Rhinopithecus bieti). However, increasing human activities threaten its habitats and corridors. We used a GIS-based Niche Model to delineate potential core habitats(PCHs) of the YSMs and a Linkage Mapper corridor simulation tool to restore potential connectivity corridors(PCCs), and defined five scenarios. A normalized importance value index(NIVI) was established to identify the protection priority areas(PPAs) for the YSMs for five scenarios. The results indicated that locations of the habitats and corridors were different in the five scenarios, thereby influencing the distribution of the PPAs and protection network of the YSMs. The NIVI value of Baimaxueshan nature reserve was 1 in the five scenarios, which implied the maximum importance. There were only 7 PCHs and 16 PCCs(with the longest average length of 223.13 km) which were mainly located around 5 NRs in scenario III. The protection network of the YSMs was composed of 16 PCHs, 18 PCCs, and 5 NRs. Under each scenario, most of the PCHs and the PCCs were located in the south of the study area. The five NRs only covered 2 PPAs of the YSMs. We suggest that the southern part of the study area needs to be strictly protected and human activities should be limited. The area of the five NRs should be expanded to maximize protection of the YSMs in the future.     

Potential priority areas and protection network for Yunnan snub-nosed monkey (Rhinopithecus bieti) in Southwest China

In Southwest China, five Nature Reserves (NRs) (Mangkang, Baimaxueshan, Yunling, Habaxueshan, and Yunlongtianchi) play a key role in protecting the endemic and endangered Yunnan snub-nosed monkey (YSM) (Rhinopithecus bieti). However, increasing human activities threaten its habitats and corridors. We used a GIS-based Niche Model to delineate potential core habitats (PCHs) of the YSMs and a Linkage Mapper corridor simulation tool to restore potential connectivity corridors (PCCs), and defined five scenarios. A normalized importance value index (NIVI) was established to identify the protection priority areas (PPAs) for the YSMs for five scenarios. The results indicated that locations of the habitats and corridors were different in the five scenarios, thereby influencing the distribution of the PPAs and protection network of the YSMs. The NIVI value of Baimaxueshan nature reserve was 1 in the five scenarios, which implied the maximum importance. There were only 7 PCHs and 16 PCCs (with the longest average length of 223.13 km) which were mainly located around 5 NRs in scenario III. The protection network of the YSMs was composed of 16 PCHs, 18 PCCs, and 5 NRs. Under each scenario, most of the PCHs and the PCCs were located in the south of the study area. The five NRs only covered 2 PPAs of the YSMs. We suggest that the southern part of the study area needs to be strictly protected and human activities should be limited. The area of the five NRs should be expanded to maximize protection of the YSMs in the future.