Chemical Properties of Eroded Soil Material

In a 5‐year stationary investigation at an experimental station in central Croatia, total amounts of erosional drift were measured on a Stagnic Luvisol on which six tillage methods were used. The chemical properties of the tilled soil and the erosional drift were recorded for each trial method in the same plots. A generally higher soil reaction value, higher organic matter content and larger amounts of available phosphorus and potassium were found in the majority of erosional drifts compared to plot soil. On black fallow, erosional drifts contained significantly larger amounts of organic matter, available phosphorus and potassium than in other treatments. Higher contents of organic matter, phosphorus and potassium were recorded in erosional drifts from spring crop cultivation than in those from cultivation of winter wheat, oil‐seed rape and a consociation of summer barley and soybean. Also, higher losses of organic matter, phosphorus and potassium by erosional drift were recorded for the up/down the slope tillage methods than for no‐tillage and tillage across the slope. This suggests that no‐tillage and tillage across the slope can be recommended for this region, since these tillage methods conserve the soil and substantially reduce water pollution by chemical agents applied in agricultural production.     

方差补偿自适应卡尔曼滤波在GPS滑坡监测中的应用研究

卡尔曼滤波是目前处理滑坡监测数据的主要方法。针对传统卡尔曼滤波中动态噪声不准或不容易确定而导致滤波发散的现象,提出用动态噪声的方差阵补偿法对滤波中的方差-协方差误差进行修正,结合三峡实测数据处理,证明该方法能有效地克服滑坡监测数据处理中滤波模型发散的问题。     

A Biophysical and Economic Assessment of a Community‐based Rehabilitated Gully in the Ethiopian Highlands

Gully erosion reduces agricultural productivity by destroying valuable land resources, increases sediment concentrations, reduces water quality, and fills up reservoirs. Gully rehabilitation has proven to be challenging especially in the high‐rainfall areas of the Ethiopian Highlands and has therefore had limited success. This paper describes a successful low‐cost gully rehabilitation effort with community participation in the Birr watershed in the Blue Nile basin that begun in early 2013. Initially, farmers were reluctant to participate for religious reasons, but with the aid of local priests and respected elders, community discussions, and a visit to a rehabilitated gully, a consensus was reached to rehabilitate a 0·71‐ha upland gully. The rehabilitation measures consisted of regrading the gully head at a 45° slope, constructing low‐cost check dams from locally available materials, and planting Pennisetum purpureum grass and Sesbania sesban. At the end of the first post‐implementation rainy season, 2,200 tons of soil was conserved by the constructed check dams and newly planted vegetation, compared with soil losses of 680 and 560 tons in two untreated, nearby gullies. In 2014, an additional 3,100 tons of soil was conserved. In 2013, the marginal rate of return (MRR) on the gully rehabilitation investment was 2·6 based on the value of increased forage production alone. When we include trapped soil nutrient values, the rehabilitation MRR was increased to 10. Although these numbers are impressive, the best proof of the success was that farmers on their own initiative rehabilitated an additional five gullies in 2014. Copyright © 2015 John Wiley & Sons, Ltd.     

Towards a Pan‐European Assessment of Land Susceptibility to Wind Erosion

Understanding spatial and temporal patterns in land susceptibility to wind erosion is essential to design effective management strategies to control land degradation. The knowledge about the land surface susceptible to wind erosion in European contexts shows significant gaps. The lack of researches, particularly at the landscape to regional scales, prevents national and European institutions from taking actions aimed at an effective mitigating of land degradation. This study provides a preliminary pan‐European assessment that delineates the spatial patterns of land susceptibility to wind erosion and lays the groundwork for future modelling activities. An Index of Land Susceptibility to Wind Erosion (ILSWE) was created by combining spatiotemporal variations of the most influential wind erosion factors (i.e. climatic erosivity, soil erodibility, vegetation cover and landscape roughness). The sensitivity of each input factor was ranked according to fuzzy logic techniques. State‐of‐the‐art findings within the literature on soil erodibility and land susceptibility were used to evaluate the outcomes of the proposed modelling activity. Results show that the approach is suitable for integrating wind erosion information and environmental factors. Within the 34 European countries under investigation, moderate and high levels of land susceptibility to wind erosion were predicted, ranging from 25·8 to 13·0 M ha, respectively (corresponding to 5·3 and 2·9% of total area). New insights into the geography of wind erosion susceptibility in Europe were obtained and provide a solid basis for further investigations into the spatial variability and susceptibility of land to wind erosion across Europe. © 2014 The Authors. Land Degradation and Development published by John Wiley & Sons, Ltd.     

Multi‐temporal Digital Photogrammetric Analysis for Quantitative Assessment of Soil Erosion Rates in the Landola Catchment of the Upper Orcia Valley (Tuscany,Italy)

This paper focuses on the analysis of the slope and catchment erosion dynamics in a typical Mediterranean context and its sensitivity to recent climatic and socio‐economic changes. The main objective of the present study is to test the reliability of digital photogrammetric analysis to evaluate the time and space evolution of erosion processes mainly triggered by surface running waters and landslides for about the last 60 years. The selected test area is the Landola catchment, a minor tributary of the Upper Orcia River Valley (Southern Tuscany). The Upper Orcia valley is a key site for the comprehension of denudation processes typically acting in Mediterranean badland areas thanks to the following: (i) the availability of long‐lasting erosion monitoring datasets (20 years' long direct measurements at erosion ‘hot spots’); (ii) its representativeness as a sub‐humid Mediterranean badland area; and (iii) the rapidity of development of erosion processes, which makes it suitable as an open‐air laboratory for the study of badland dynamics. The outputs of this work highlight that the application of high‐resolution digital photogrammetric methodologies can represent a powerful and low‐cost tool to evaluate rates and spatial–temporal distribution of denudation processes, as confirmed by the validation through field point monitoring in areas close to the study area. The results obtained for the study area confirm that high erosion rates are a persistent environmental problem for the Upper Orcia Valley, which is not solved up to now, despite various land conservation interventions. The performed multi‐temporal analysis shows a slight decrease in the average water erosion rate during the last 60 years and a parallel increase in the frequency of mass wasting events. These variations are most likely related to a complex interplay between land use changes that have affected the study area during the studied period, revealing a very delicate equilibrium between farming activities and erosion processes. Copyright © 2014 John Wiley & Sons, Ltd.     

覆盖光降解地膜对土壤污染及棉花生育影响的研究

自１９８４年以来，对国内外３０种不同型号的可控制降解时间的光降解地膜，进行了棉花田间效应研究认为，光解膜在自然曝晒下在一定时间范围内能够自行降解，与普通地膜相比具有相同的土壤环境效应和相近的增产效果。降解产物对土壤的矿质元素含量无明显影响，也未发现有害物质产生。在棉田应用时，诱导期控制在６０天左右，此后，降解过程越短越好，最长不宜超过１２０天。     

Accelerated Generalized Minimal Residual Algorithm

This paper studies the fundamental theory of the generalized minimal residual algorithm(GMRES(m))in Krylov subspace and specially the relationship between residual vector and Krylov subspace.The relationship of the algorithm convergence and the subspace be selected is further researched according the linear system about residual vector.It is posed that the convergence can be slowed down because there are so many very small eigenvalue in magnitude.And a accelerated method(AGMRES(m)) is proposed to improve the convergence of the GMRES(m).Theoretical analysis and numerical results show the reliability and efficiency of the algorithm.     

侵蚀土壤物理性质变化及其与土壤氮素迁移转化的关系

侵蚀破坏土壤团聚体结构,使团聚体破碎产生更小的可迁移颗粒而导致土壤养分的运移;侵蚀还改变了土壤的水分状况,水蚀在一定程度上增加了土壤的含水量,风蚀则可使土壤的含水量降低。团聚体结构的破坏以及土壤水分状况的改变与土壤的氮素迁移转化过程有着密切的联系。本文仅对土壤侵蚀造成的土壤物理性状的改变与土壤氮素迁移转化作一概述,并就耕作、覆盖等降低土壤侵蚀的农业措施与土壤氮素转化的关系进行阐述,提出了侵蚀土壤氮素研究的去向。     

Residual effects of the Xa-4 resistance gene in three rice cultivars when exposed to a virulent isolate of Xanthomonas campestris pv. oryzae

Summary F₂ plants of five, and F₃ plants of three, crosses between genotypes carrying the race-specific resistance gene Xa-4 and genotypes not carrying this gene were inoculated with two isolates of Xanthomonas campestris pv. oryzae. Half the tillers of each plant received isolate PX061, avirulent on the Xa-4 gene, the other half of the tillers received isolate PX099, virulent for the Xa-4 gene. The F₂ and F₃ populations segregated for a single dominant resistance gene, Xa-4.The parental, F₂ and F₃ genotypes not carrying Xa-4 had mean lesion lengths between 28 and 29 cm for both isolates. The Xa-4 carrying parents showed a mean lesion length of 2.7 cm with the avirulent isolate and of 12.4 cm with the virulent isolate. The Xa-4 carrying F₂ and F₃ genotypes had mean lesion lengths of 5.2 and 20.1 cm for the two isolates, respectively. These observations strongly indicate that the Xa-4 gene, carried by the rice genotypes studied (IR28, Cisadane and BR51-282-8), had a considerable residual effect when exposed to virulent isolate PXO99.