Composition, structural characteristics and temporal patterns of fish assemblages in non-tidal Mediterranean lagoons: A case study

The importance of transitional water ecosystems as nursery habitats and feeding grounds for fish species is well-known. Detailed studies of colonization patterns of fish guilds in response to biotic and abiotic drivers are however unevenly distributed among ecosystem types. We address here the temporal variability of fish assemblages in small non-tidal lagoons in the Mediterranean basin. The study was carried out at the Acquatina lagoon (Lecce, Italy) where four stations, situated in two habitat types along a confinement gradient, were sampled twice per month for one year with fyke nets. Forty-five taxa ranging across 20 families were collected, with the most abundant species, Atherina boyeri, accounting for more than 95% of total abundance. Pooling all species together (excluding sand smelt), the structural features of the assemblage, relative abundance of families, and abundance of individual species all showed significant temporal patterns. Mean abundance peaked in Summer and Autumn and fell in Winter, whereas taxonomic richness and diversity were highest in Summer and lowest in Spring. Within the fish assemblage, multivariate ordination showed temporal segregation of species belonging to the same family or genus and expected to be functionally similar, suggesting that they avoid competition for space and resources by timing inward migration and peak occurrence differently. Of the environmental driving forces, which also showed temporal patterns of variation, salinity was the main factor affecting the distribution of individuals and species. The catch of young individuals of several marine species confirmed the role of this small lagoon as a nursery and feeding area, and emphasized the need for further studies.     

中国北方荒漠区降水空间结构型及变异性研究

依据中国北方荒漠区35个站点1951—2005年降水资料,运用(旋转)经验正交函数分解(EOF/REOF)、主成分分析、分形理论及地统计学等方法探讨了北方荒漠区降水空间结构型及空间变异性。结果表明,降水空间分布以“相间复杂”型和“东西相反”型为主（对总体方差贡献分别为35.8%和20.4%）;降水趋势自西向东逐渐减弱,有西部增加、中部地区小幅增大而东部地区趋于干旱的可能。新疆地区对全区降水波动方差贡献率达70.4%。新疆地区及青海-河西-河套地区变异函数曲线符合球状模型,内蒙古高原中东部地区符合指数模型;随机因素引起的空间异质性占0.01%~1.62%。20世纪50年代和70年代青海-河西-河套地区变异性最强,新疆地区次之,内蒙古高原中东部地区最弱,90年代以后新疆地区最强,内蒙古高原中东部地区次之,青海-河西-河套地区最弱。新疆地区、青海-河西-河套地区及内蒙古高原中东部地区降水分别在南北方向、东西方向及东北-西南方向异质性最强。     

2008年汶川8.0级地震发生的历史与现今地震活动背景

为了了解2008年5月12日四川汶川M_S8.0地震发生的地震活动背景,本文综合历史与现代地震资料,从南北地震带中段及其邻区的视野研究了汶川地震前1~2千年的强震活动性,以及震前20年的地震活动性背景.结果主要表明：（1）至少在2008年之前的1100~1700年中,龙门山断裂带未发生M≥7的地震,相对其南、北两侧的其他活动断裂带（或段）形成一个地震空区,2008年汶川M_S8.0地震发生在该空区中;（2）17世纪以来,在由龙门山断裂带大部分地区、川北岷江-虎牙断裂带以及甘南文县-武都断裂带组成的巴颜喀拉块体东边界上共发生了12次M=6.5~8.0地震,显示出一个已持续了近400年、逐渐加速的应变能释放过程,2008年汶川M_S8.0地震属于该过程中两次巨大地震之一;（3）汶川地震前20年,龙门山断裂带中、南段不存在背景地震活动的平静,反而显示出比曾经发生过1879年M_S8地震的甘南文县-武都断裂带还略高的地震活动背景水平;（4）2008年汶川地震的强度远远超出龙门山断裂带的历史最大地震,说明仅基于数百年至一、两千年的历史地震记载,远不足以正确评估较低滑动速率的、大型活动断裂带的潜在地震危险性.     

Are spatial patterns of soil moisture at plot scales generalisable across catchments,climates, and other characteristics? A synthesis of synoptic soil moisture across the Mid-Atlantic

The spatial variation of soil moisture over very small areas (<100 m²) can have nonlinear impacts on cycling and flux rates resulting in bias if it is not considered, but measuring this variation is difficult over extensive temporal and spatial scales. Most studies examining spatial variation of soil moisture were conducted at hillslope (0.01 km²) to multi-catchment spatial scales (1000 km²). They found the greatest variation at mid wetness levels and the smallest variation at wet and dry wetness levels forming a concave down relationship. There is growing evidence that concave down relationships formed between spatial variation of soil moisture and average soil moisture are consistent across spatial scales spanning several orders of magnitude, but more research is needed at very small, plot scales (<100 m²). The goal of this study was to characterise spatial variation in shallow soil moisture at the plot scale by relating the mean of measurements collected in a plot to the standard deviation (SD). We combined data from a previous study with thousands of new soil moisture measurements from 212 plots in eight catchments distributed across the US Mid-Atlantic Region to (1) test for a generalisable mean–SD relationship at plot scales, (2) characterise how landcover, land use, season, and hillslope position contribute to differences in mean–SD relationships, and (3) use these generalised mean–SD relationships to quantify their impacts on catchment scale nitrification and denitrification potential. Our study found that 98% of all measurements formed a generalised mean–SD relationship like those observed at hillslope and catchment spatial scales. The remaining 2% of data comprised a mean–SD relationship with greater spatial variation that originated from two riparian plots reported in a previous study. Incorporating the generalised mean–SD relationship into estimates of nitrification and denitrification potential revealed strong bias that was even greater when incorporating mean–SD observations from the two riparian plots with significantly greater spatial variation.     

Linking soil water balance with flood spatial arrangement in an extremely flat landscape

In areas with very mild relief, water drains in a disordered way due to the lack of a developed drainage network, as it occurs in extremely flat sedimentary regions like the Argentine Pampas. The study analysed the flood spatial arrangements in 2014 by calculating landscape metrics and relating them to soil water balance. The study area is located at Del Azul creek lower basin (Pampa Ecoregion, Argentina). Daily soil water balances were obtained, and seven landscape metrics were calculated in 15 windows in five LandSat images, all along 2014, to explore the relationship between hydrological scenarios and spatial pattern summarized with principal component analysis. Water excess concentrated in winter (June and August); deficits were in late spring and summer (January and November), whereas the beginning of autumn (March) was an intermediate situation. Principal component 1 (44.7%) reflected area and shape metrics and correlated positively with water table level; principal component 2 (32.3%) summarized aggregation ones and was negatively associated with accumulated water excesses or deficits in previous 30 days and useful reserve. Both exhibited possible threshold-driven behaviour. Internal heterogeneity between NW and SE zones within the study area coincided with the existence of ancient alluvial fans. The results highlight the peculiarities of the flood spatial patterns in regions with very mild relief, where landforms usually determine water flows.     

Hydrology and related changes after harvesting native forest catchments and establishing pinus radiata plantations. Part 1. Introduction to study

The hydrology of eight small catchments (1.63–8.26 ha) has been monitored in Westland, New Zealand since 1975. Two of these catchments were left in indigenous beech-podocarp-hardwood forest and the rest were subjected to various harvesting and land preparation treatments before being planted with Pinus radiata. This paper introduces a series of papers on the hydrology of the indigenous forest catchments and the changes that occurred after treatment. The catchments, experimental programme, climate of the area and the rainfall regime experienced between 1975 and 1987 are described.     

PATTERNS OF HORSE DEVOLUTION AND TRACTOR DIFFUSION IN ILLINOIS, 1920–1982*

The concern is to extend certain diffusion concepts to devolution. In this example, tractors replaced horses because tractors had advantages over horses. Logistic curves depict well the temporal rate of tractor acceptance and of horse abandonment. Although differing somewhat in time, the spatial patterns of adoption and abandonment are similar. They centered early in east central Illinois, a prosperous agricultural core, and spread outward. Laggard counties as well as persister ones were mainly in southern Illinois, a peripheral area with a relatively impoverished agriculture. Influences on the patterns include farm value, size, and type and land quality.