Assessment of soil erosion under rainfed sugarcane in KwaZulu‐Natal,South Africa

Soil erosion from agricultural land use runoff is a major threat to the sustainability of soil composition and water resource integrity. Sugarcane is an important cash and food security crop in South Africa, subjected to an intensive soil erosion, and consequently, severe land degradation. This study aimed to investigate soil erosion and associated soil and cover factors under rainfed sugarcane, in a small catchment, KwaZulu‐Natal, South Africa. Three replicated runoff plots were installed at different slope positions (down, mid and upslope) within cultivated sugarcane fields to monitor soil erosion during the 2016–2017 rainy season. On average, annual runoff (RF) was significantly greater from 10 m² plots with 1163.77 ± 2.63 l/m/year compared to 1 m² plots. However, sediment concentration (SC) was significantly lower in 10 m² (0.34 ± 0.04 g/l) compared to 1 m² (6.94 ± 0.24 g/l) plots. The annual soil losses (SL) calculated from 12 rainfall events was 58.36 ± 0.77 and 8.84 ± 0.20 t/ha from 1 m² and 10 m² plots, respectively. The 1 m² plot, SL (2.4 ± 1.41 ton/ha/year) in the upslope experienced 33% more loss than the midslope and 50% more loss than the downslope position. SL was relatively lower from the 10 m² plots than the 1 m² plots, which is explained by high sediment deposition at the greater plot scale. SL was negatively correlated with the soil organic carbon stocks (r = ?0.82) and soil surface cover (r = ?0.55). RF decreased with the increase of slope gradient (r = ?0.88) and soil infiltration rate (r = ?0.87). There were considerable soil losses from cultivated sugarcane fields with low organic matter. These findings suggest that to mitigate soil erosion, soil organic carbon stocks and vegetation cover needs to be increased through appropriate land management practices, particularly in cultivated areas with steep gradients.     

Modeling Flow,Nutrient, and Sediment Delivery from a Large International Watershed Using a Field‐Scale SWAT Model

A large international watershed, the St. Clair‐Detroit River System, containing both extensive urban and agricultural areas, was modeled using the Soil and Water Assessment Tool (SWAT) model. The watershed, located in southeastern Michigan, United States, and southwestern Ontario, Canada, encompasses the St. Clair, Clinton, Detroit (DT), Sydenham (SY), Upper, and Lower Thames subwatersheds. The SWAT input data and model resolution (i.e., hydrologic response units, HRUs), were established to mimic farm boundaries, the first time this has been done for a watershed of this size. The model was calibrated (2007–2015) and validated (2001–2006) with a mix of manual and automatic methods at six locations for flow and water quality at various time scales. The model was evaluated using Nash–Sutcliffe efficiency and percent bias and was used to explore major water quality issues. We showed the importance of allowing key parameters to vary among subwatersheds to improve goodness of fit, and the resulting parameters were consistent with subwatershed characteristics. Agricultural sources in the Thames and SY subwatersheds and point sources from DT subwatershed were major contributors of phosphorus. Spatial distribution of phosphorus yields at HRU and subbasin levels identified locations for potential management targeting for both point and nonpoint sources and revealed that in some subwatersheds nonpoint sources are dominated by urban sources.     

Characterizing In Situ Methane‐Enhanced Biostimulation Potential for 1,4‐Dioxane Biodegradation in Groundwater

This study characterizes the 1,4‐dioxane biodegradation potential for an in situ methane‐enhanced biostimulation field pilot study conducted at Air Force Plant 44, located south of the Tucson International Airport in Arizona. In this study, the use of methane as the primary substrate in aerobic cometabolic biodegradation of 1,4‐dioxane is evaluated using environmental molecular diagnostic tools. The findings are compared to an adjacent pilot study, wherein methane was generated via enhanced reductive dechlorination and where methane monooxygenase and methane‐oxidizing bacteria were also found to be abundant. This article also presents the use of ¹³C and ²H isotopic ratio enrichment, a more recent tool, to support the understanding of 1,4‐dioxane biodegradation in situ. This study is the first of its kind, although alkane gas‐enhanced biodegradation of 1,4‐dioxane has been evaluated extensively in microcosm studies and propane‐enhanced biodegradation of 1,4‐dioxane has been previously studied in the field. ©2016 Wiley Periodicals, Inc.     

A new look at the psychological contract during organizational socialization: The role of newcomers' obligations at entry

Previous studies have demonstrated that the psychological contract is largely shaped during socialization. This study adopts a complementary perspective and analyzes how the psychological contract at the start of employment shapes the subsequent socialization process. Drawing upon social exchange theory, we propose that newcomers with a higher sense of their personal obligations at entry will perceive orientation training as more useful and develop better relationships with their supervisors and peers, which in turn will facilitate their work adjustment. Results of a longitudinal survey on a sample of 144 recruits from a European Army show that newcomers with a higher initial sense of their employee obligations toward their employer report higher perceived training utility, higher leader–member exchange (LMX) with their instructors, and higher team–member exchange (TMX) with their platoon peers. Moreover, perceived training utility and LMX predict the fulfillment of employers' obligations; and training utility predicts the level of newcomers' employee obligations. Finally, training utility, LMX, and TMX predict some of three indicators of newcomers' adjustment, namely, role clarity (training utility and LMX), group integration (TMX), and organizational values understanding (training utility). These results highlight how newcomers' obligations at the start of employment contribute to the social exchange dynamic underlying organizational socialization. Copyright © 2015 John Wiley & Sons, Ltd.     

Energy's role in the extraversion (dis)advantage: How energy ties and task conflict help clarify the relationship between extraversion and proactive performance

While academic and practitioner literatures have proposed that extraverts are at an advantage in team‐based work, it remains unclear exactly what that advantage might be, how extraverts attain such an advantage, and under which conditions. Theory highlighting the importance of energy in the coordination of team efforts helps to answer these questions. We propose that extraverted individuals are able to develop more energizing relationships with their teammates and as a result are seen as proactively contributing to their team. However, problems in coordination (i.e., team task conflict) can reverse this extraversion advantage. We studied 27 project‐based teams at their formation, peak performance, and after disbandment. Results suggest that when team task conflict is low, extraverts energize their teammates and are viewed by others as proactively contributing to the team. However, when team task conflict is high, extraverts develop energizing relationships with fewer of their teammates and are not viewed as proactively contributing to the team. Our findings regarding energizing relationships and team task conflict clarify why extraversion is related to proactive performance and in what way, how, and when extraverts may be at a (dis)advantage in team‐based work. Copyright © 2016 John Wiley & Sons, Ltd.     

Estimating Floodwater Depths from Flood Inundation Maps and Topography

Information on flood inundation extent is important for understanding societal exposure, water storage volumes, flood wave attenuation, future flood hazard, and other variables. A number of organizations now provide flood inundation maps based on satellite remote sensing. These data products can efficiently and accurately provide the areal extent of a flood event, but do not provide floodwater depth, an important attribute for first responders and damage assessment. Here we present a new methodology and a GIS‐based tool, the Floodwater Depth Estimation Tool (FwDET), for estimating floodwater depth based solely on an inundation map and a digital elevation model (DEM). We compare the FwDET results against water depth maps derived from hydraulic simulation of two flood events, a large‐scale event for which we use medium resolution input layer (10 m) and a small‐scale event for which we use a high‐resolution (LiDAR; 1 m) input. Further testing is performed for two inundation maps with a number of challenging features that include a narrow valley, a large reservoir, and an urban setting. The results show FwDET can accurately calculate floodwater depth for diverse flooding scenarios but also leads to considerable bias in locations where the inundation extent does not align well with the DEM. In these locations, manual adjustment or higher spatial resolution input is required.     

力学载荷条件下 EB-PVD 热障涂层损伤行为研究

目的研究力学载荷条件下EB-PVD热障涂层的损伤行为。方法采用电子束物理气相沉积工艺(EB-PVD)制备热障涂层(TBCs),利用SEM和体式显微镜对力学性能试验后带涂层试样的断口特征、裂纹形貌和金相组织进行观察,分析热障涂层在拉伸、持久和旋转弯曲疲劳等典型力学载荷条件下的损伤行为。结果在室温拉伸条件下,陶瓷层内先出现垂直于应力轴、沿柱状晶簇扩展的平行环状周向微裂纹,随着拉伸塑变量的增加,局部区域裂纹贯穿粘结层并进入合金基体;900℃高温拉伸条件下裂纹也产生于陶瓷层,但裂纹均钝化于粘结层与陶瓷层的界面,并穿透粘结层。在持久条件下,试样在弹性变形阶段涂层即发生开裂,随后沿着陶瓷层柱状晶簇间扩展,但未扩展至粘结层;在高温高周疲劳条件下,裂纹首先出现在粘结层,随后向基体逐渐扩展,扩展深度较浅,而基体疲劳裂纹在粘结层裂纹末端萌生并倾斜滑移扩展。结论提高粘结层韧性、减少粘结层中裂纹萌生和向基体扩展,是热障涂层材料和工艺优化的有效途径。     

The market and shadow value of informal fish catch: a framework and application to Panama

Fisheries catches are known to be widely underreported, and much of their value flows in informal markets. Goods and services that are not directly sold in a market also have a corresponding economic value, here termed ‘shadow value’, which can apply to discarded fish—or those that are consumed but not sold (e.g., subsistence catches). Here, we estimate the monetary value of fisheries catches in Panama that are landed but not reported, or that are discarded at sea; this includes catches from artisanal and industrial fleets, as well as recreational and subsistence fisheries. Based on available data, we estimate that the market and shadow value of unreported catches in Panama in 2010 was around US$92 million, equal to approximately 43% of the total reported landed value. In the case of discarded fish, the shadow value represents the potential but entirely unrealized economic benefit of landing such fish; in the case of unreported landings, unreported market value represents only the first link in the potentially sophisticated informal seafood economy. One must be careful in considering these results for policy. It is possible that, rather than seeking to capture these ‘lost’ benefits, fish that are discarded or unreported should not have been caught at all, for example, if they are juveniles or of threatened species; conversely, unreported subsistence catches are crucial for food security throughout the world. These results help contextualize the scale of unreported fisheries in economic terms, and can inform subsequent policies and strategies to ensure social, ecological, and economic sustainability.     

海洋铁施肥研究进展

简要回顾了自1993年以来世界范围内海洋铁施肥试验的研究动态以及阶段性研究成果,注重探讨铁施肥后初级生产力的变化情况,海水中颗粒态有机碳变化与迁移情况以及铁施肥可能造成的环境影响及生态效应,初步分析了海洋铁施肥作为缓解气候变化策略面临的主要问题,以及进一步开展海洋铁施肥研究需要解决的关键问题,为我国开展海洋铁施肥相关的...