Defining the habitat niche of Alopecurus myosuroides at the field scale

The distribution of Alopecurus myosuroides (black‐grass) in fields is patchy. The locations of these patches can be influenced by the environment. This presents an opportunity for precision management through patch spraying. We surveyed five fields on various types of soil using a nested sampling design and recorded both A. myosuroides seedlings in autumn and seed heads in summer. We also measured soil properties at those sampling locations. We found that the patches of seed heads within a field were smaller than the seedling patches, suggesting that techniques for patch spraying based on maps of heads in the previous season could be inherently risky. We also found that the location of A. myosuroides patches within fields can be predicted through their relationship with environmental properties and that these relations are consistent across fields on different soil types. This improved understanding of the relations between soil properties and A. myosuroides seedlings could allow farmers to use pre‐existing or suitably supplemented soil maps already in use for the precision application of fertilisers as a starting point in the creation of herbicide application maps.     

半干旱农牧交错区土壤养分空间变异特征分析——以内蒙古伊金霍洛旗为例

本文以伊金霍洛旗为研究区,通过GIS平台对土壤养分中的有机质、全氮、速效钾的空间插值方法进行了比较并得到了最优插值图。然后分析了该旗土壤养分的空间分布规律,为该地区的农业生产布局和生态环境建设提供了依据。通过比较后认为,在该地区有机质的空间插值用反距离权重法为好,而全氮和速效钾的空间插值以克吕格法的指数模型和高斯模型为好。地统计学分析结果表明:有机质、全氮和速效钾的变程分别为11853m,8932.2m和732.99m,全氮和速效钾具有中等空间相关性,而有机质空间相关性较弱。有机质含量普遍偏低,在91%的面积中有机质含量低于10g/kg,其相对高值区呈离散分布,可能与隐域植被的分布有关。全氮含量与有机质含量分布相似,在70%的面积中低于0.75g/kg,而速效钾含量中等,介于102.04-103.31mg/kg之间。在三个不同的景观亚区中,乌审凹地亚区的土壤养分状况较好,黄土丘陵亚区养分状况最差,毛乌素沙地亚区介于它们之间。     

伊犁新垦区土壤盐分垂直分异特征研究

土壤盐分垂直分异特征的定量研究是农业生产、管理以及环境治理的重要内容。采用经典统计分析和层次聚类分析等方法,选择Pearson相关系数和欧氏距离作为聚类统计量,分析伊犁新垦区土壤剖面盐分的垂直分布特征。结果表明:伊犁新垦区土壤盐分存在很强的变异性,各层盐分的变异系数皆大于1,土壤剖面可分为表聚型盐分剖面、中聚型盐分剖面和底聚型盐分剖面等三种类型,根据盐分的数值大小,进一步可划分为非盐化土、表聚盐化土、中聚盐化土和底聚盐化土等四种类型,各占剖面总数的66%、5%、10%和19%。空间上伊犁新垦区土壤盐分垂直变化特征的差异性大,四种类型的盐化土皆有所分布,中聚盐化土和底聚盐化土分布的地区容易发生次生盐渍化,是农业生产和环境治理需要重点关注的区域。     

苦荞种质资源萌发期抗旱性综合评价

以PEG-6000为渗透剂对110份苦荞种质资源进行模拟干旱处理,研究了苦荞种子在0、5%、10%、15%、20%的PEG-6000溶液胁迫下的萌发情况,分析了种子的相对发芽势、相对发芽率、相对萌发指数、相对胚根长和相对胚根粗和萌发耐旱指数的变化。结果表明：15% PEG-6000可以作为苦荞种子萌发期耐旱性鉴定的适宜浓度;通过主成分分析法确定了相对发芽势、相对发芽率、相对萌发指数为关键指标,利用隶属函数结合权重分析法得到了萌发期苦荞种质资源耐旱性的综合评价值D。根据D值排序,筛选鉴定到耐旱型5份、较耐旱型28份、中间型48份、敏感型29份。通过聚类分析将110份苦荞种质资源划分为5个亚群,亚群Ⅰ是一类耐旱能力较强的亚群,亚群Ⅱ和亚群Ⅲ为中度耐旱亚群,亚群Ⅳ和亚群Ⅴ为典型的旱敏感亚群。     

Mapping the distribution of weeds in Great Britain in relation to national survey data and to soil type

A method is presented for using botanical survey and soil survey data to generate maps of the probability of occurrence of weeds in Britain across all habitats. For each species, data from a national, designed botanical survey were smoothed spatially, and the association between species distribution and soils was calculated using the botanical survey and 1 km square data on dominant and subdominant soils using national data. A logistic regression was fitted using the botanical survey data, and was interpolated across the whole country to generate the maps. The resulting maps show the probability of occurrence of species and species groups at the 2-km scale. They map the potential, rather than realized, risk of particular types of weed infestation, as they do not account for local management factors.     

黄土丘陵沟壑区植被类型对土壤质量的影响

土壤质量是支撑地球生物圈和进行可持续农业生产的最重要的环境因子之一。以黄土丘陵沟壑区的纸坊沟流域为研究区,选取不同植被类型和不同恢复年限的样地8块,测定土壤微生物性质（微生物生物量碳、微生物生物量氮、微生物生物量磷、微生物商）、土壤化学性质（土壤有机碳、全氮、碳氮比、碱解氮、销态氮、铵态氮和速效磷）、土壤酶活性（转化酶...     

Weed species composition of small‐scale farmlands bears a strong crop‐related and environmental signature

Weed species loss due to intensive agricultural land use has raised the need to understand how traditional cropland management has sustained a diverse weed flora. We evaluated to what extent cultivation practices and environmental conditions affect the weed species composition of a small‐scale farmland mosaic in Central Transylvania (Romania). We recorded the abundance of weed species and 28 environmental, management and site context variables in 299 fields of maize, cereal and stubble. Using redundancy analysis, we revealed 22 variables with significant net effects, which explained 19.2% of the total variation in species composition. Cropland type had the most pronounced effect on weed composition with a clear distinction between cereal crops, cereal stubble and maize crops. Beyond these differences, the environmental context of croplands was a major driver of weed composition, with significant effects of geographic position, altitude, soil parameters (soil pH, texture, salt and humus content, CaCO₃, P₂O₅, K₂O, Na and Mg), as well as plot location (edge vs. core position) and surrounding habitat types (arable field, road margin, meadow, fallow, ditch). Performing a variation partitioning for the cropland types one by one, the environmental variables explained most of the variance compared with crop management. In contrast, when all sites were combined across different cropland types, the crop‐specific factors were more important in explaining variance in weed community composition.     

Ecological implications from a molecular analysis of phytoplasmas involved in an aster yellows epidemic in various crops in Texas

ABSTRACT In the spring of 2000, an aster yellows (AY) epidemic occurred in carrot crops in the Winter Garden region of southwestern Texas. A survey revealed that vegetable crops, including cabbage, onion, parsley, and dill, and some weeds also were infected by AY phytoplasmas. Nested polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis of PCR-amplified phytoplasma 16S rDNA were employed for the detection and identification of phytoplasmas associated with these crops and weeds. Phytoplasmas belonging to two subgroups, 16SrI-A and 16SrI-B, in the AY group (16SrI), were predominantly detected in infected plants. Carrot, parsley, and dill were infected with both subgroups. Onion and three species of weeds (prickly lettuce, lazy daisy, and false ragweed) were predominantly or exclusively infected by subgroup 16SrI-A phytoplasma strains, while cabbage was infected by subgroup 16SrI-B phytoplasmas. Both types of phytoplasmas were detected in three leafhopper species, Macrosteles fascifrons, Scaphytopius irroratus, and Ceratagallia abrupta, commonly present in this region during the period of the epidemic. Mixed infections were very common in individual carrot, parsley, and dill plants and in individual leafhoppers. Sequence and phylogenetic analyses of 16S rDNA and ribosomal protein (rp) gene sequences indicated that phytoplasma strains within subgroup 16SrI-A or subgroup 16SrI-B, detected in various plant species and putative insect vectors, were highly homogeneous. However, based on rp sequences, two rpI subgroups were identified within the subgroup 16SrI-A strain cluster. The majority of subgroup 16SrI-A phytoplasma strains were classified as rp subgroup rpI-A, but phytoplasma strains detected in one onion sample and two leafhoppers (M. fascifrons and C. abrupta) were different and classified as a new rp subgroup, rpI-N. The degree of genetic homogeneity of the phytoplasmas involved in the epidemic suggested that the phytoplasmas came from the same pool and that all three leafhopper species may have been involved in the epidemic. The different phytoplasma population profiles present in various crops may be attributed to the ecological constraints as a result of the vector-phytoplasma-plant three-way interaction.     

基于GIS的北京地区未来10年土壤水力侵蚀演化趋势探讨

本文是基于永定河上游北京典型段的土壤水力侵蚀深度、降雨强度、地表径流深度、土层有效厚度、土粒平均粒径、植被覆盖度等数据图层 ,利用 GIS、SPSS软件包 ,通过建立水力侵蚀遥感信息模型 ,制作了北京地区土壤水力侵蚀深度图和抗侵蚀年限图 ,依据将近论古的原则及作者的北京地区未来 1 0年环境演化趋势预测结果 ,探讨了未来 1 0年水力侵蚀演化趋势。这可以为该地区未来土地利用和泥石流分布规律研究提供理论指导     

Genetic Diversity Within Colletotrichum acutatum sensu Simmonds

ABSTRACT Isolates of Colletotrichum acutatum from several hosts were characterized by various molecular methods in comparison with morphological identification. Species-specific primer analysis was reliable for grouping C. acutatum isolates to their designated species. Arbitrarily primed polymerase chain reaction and A+T-rich DNA analyses identified four subgroups within C. acutatum. Subgroup I contained U.S. isolates from almond, apple, peach, and pecan, subgroup II contained isolates from anemone, olive, and strawberry, subgroup III contained isolates from almond (Israel) and strawberry (Spain), and subgroup IV contained a single isolate from anemone (the Netherlands). Likewise, sequence analysis of the internal transcribed spacer (ITS) 2 region alone or the complete ITS (ITS 1-5.8S-ITS 2) region grouped the isolates into the same four subgroups. Percent similarity of the complete ITS region within each cluster ranged from 99.6 to 100.0, 99.8 to 100.0, and 98.6% among subgroups I, II, and III, respectively. DNA sequence analysis of the ITS 2 region alone or the entire ITS 1-2 region was more informative than that of the ITS 1 region, which could only group the isolates into two main clusters. The molecular methods employed for studying genetic variation in populations of C. acutatum determined that this species is diverse, indicating that isolates within populations of each subgroup are not host specific.     

Use of airborne multispectral imagery to discriminate and map weed infestations in a citrus orchard

Reliable information on weed abundance and distribution within fields is essential for weed management in agricultural systems. Such information is necessary to adopt localized and variable rates of herbicide spraying, thus reducing chemical waste, crop damage, and environmental pollution. This paper examined the potential of airborne multispectral imagery to discriminate and map weed infestations in an experimental citrus orchard in Japan. Using an airborne digital sensor, multispectral imagery was acquired over the study site on 10 April 2003. The obtained reflectance imagery was analyzed using an image object-based approach in eCognition. After creating image objects on the image, the spectral information for weeds and citrus, represented by corresponding selected sample image objects, was extracted. Significant differences in the spectral characteristics between weeds and citrus were observed in each of the red, green, and blue wavebands. The simple average values of these wavebands were used to classify image objects with the nearest neighbor algorithm. Maps were generated with different classes or levels of class groups. A subsequent accuracy assessment demonstrated that the weeds were successfully discriminated from other image objects with a classification accuracy of 99.07%. Therefore, maps generated based on the classification result could provide valuable information for developing a site-specific weed management program for the study orchard.     

Grazing exclusion-induced shifts,the relative importance of environmental filtering,biotic interactions and dispersal limitation in shaping desert steppe communities,northern China

Grazing exclusion is one of the most efficient approaches to restore degraded grassland but may negatively affects the recovery of species diversity. Changes in plant species diversity should be a consequence of the ecological assembly process. Local community assembly is influenced by environmental filtering, biotic interactions, and dispersal. However, how these factors potentially contribute to changes to species diversity is poorly understood, especially in harsh environments. In this study, two management sites within a Stipa breviflora desert steppe community(typical natural steppe) were selected in northern China. In one of the two management sites, grazing has been excluded since 2010 and in the other with open grazing by sheep. In August 2016, three plots were established and 100 sampling units were created within each plot in a 5 m×5 m area at the two management sites. To assess the effects of grazing exclusion on S. breviflora steppe, we analyzed the vegetation biomass, species diversity,soil organic carbon, and soil particle size distribution using paired T-tests. In addition, variation partitioning was applied to determine the relative importance of environmental filtering and dispersal limitation. Null mode analysis was used to quantify the influence of biotic interactions in conjunction with Eco Sim niche overlap and co-occurrence values. Our results demonstrated that(1) species diversity significantly decreased and the main improvements in soil quality occurred in the topsoil 0–10 cm after the grazing exclusion;(2) environmental filtering was important for community assembly between grazed and fenced grassland and this appears particularly true for soil particle size distribution, which may be well correlated with soil hydrological processes; and(3) however, competitive exclusion may play a significant role within the exclusion. The multiple pathways of assembly may collectively determine negative effects on the restoration of species diversity. Therefore, designers should be aware of the risk of reducing grazing exclusion-induced species diversity and account for manipulating processes. This in turn will reduce dominant species and promote environmental heterogeneity to maximize species diversity in semi-arid regions.     

新疆柽柳属植物(Tamarix L.)的分布与群落相似性聚类分析

调查研究了新疆境内柽柳属植物的分布与群落类型。在前人工作基础上绘制了新疆柽柳属植物分布图。研究结果表明，地表水是柽柳群落繁衍的关键，地下水是柽柳群落生存的命脉。水是决定和影响柽柳属植物现代地理分布的关键环境因子。依据柽柳群落所处地形地貌、土壤类型和群落景观等环境特征将柽柳群落划分成9种不同的生态类型。依据群落间物种组成的相似性系数对群落进行了聚类分析，揭示了各类落间的内在关联性和演替规律。     

甘肃宁夏黄土高原半干旱区农业生态系统景观类型研究

农业生态系统景观分类研究的目的是探讨农业生态系统在中小尺度空间的地域分异规律，为优化系统结构、进行系统的景观生态设计、充分合理利用农业自然资源、建立稳定高效农业生态系统、改善和保护农业生态环境提供科学依据。本文分析了甘宁黄土高原半干旱区农业生态系统的现状特性。探讨了农业生态系统景观类型研究的客观基础及其分类的原则、依据和方法。在此基础上，对研究区农业生态系统进行了景观类型划分，对各级各类农业生态系统景观特征进行了评述、并做出了甘肃宁夏黄土高原半干旱区农业生态系统景观类型图。     

Integrating multiple electromagnetic data to map spatiotemporal variability of soil salinity in Kairouan region,Central Tunisia

Soil salinization is a major problem affecting soils and threatening agricultural sustainability in arid and semi-arid regions,which makes it necessary to establish an efficient strategy to manage soil salinity and confront economic challenges that arise from it.Saline soil recovery involving drainage of shallow saline groundwater and the removal of soil salts by natural rainfall or by irrigation are good strategies for the reclamation of salty soil.To develop suitable management strategies for salty soil reclamation,it is essential to improve soil salinity assessment pro cess/mechanism and to adopt new approaches and techniques.T his study mapped a recovered area of 7200 m2 to assess and verify variations in soil salinity in space and time in K airouan region in Central Tunisia,taking into account the thickness of soil materials.Two electromagnetic conductivity meters(EM38 and EM31)were used to measure the electrical conductivity of saturated soil-paste extract(ECe)and apparent electrical conductivity(E Ca).Multiple linear regression was established between ECe and ECa,and it was revealed that ECa-EM38 is optimal for E Ce prediction in the surface soils.Salinity maps demonstrated that the spatial structure of soil salinity in the region of interest was relatively unchanged but varied temporally.Variation in salinity at the soil surface was greater than that at a depth.These findings can not only be used to track soil salinity variations and their significance in the field but also help to identify the spatial and temporal features of soil salinity,thus improving the efficiency of soil management.     

IT applications in Hungarian plant protection and soil conservation,focusing on GIS*

In Hungary, plant protection and soil conservation are not only believed to be closely related, but are managed in a single, nationwide Service. GIS is used to assist the Service in organising this joint activity by:

• • establishing the infrastructure suitable for coordinating different kinds of data collection, GIS processing, transfer and publication of such data
• • improving the staff capacity by providing training and technical assistance in using GIS, capturing field data, navigating and using thematic maps
• • creating a simple and interactive interface for accessing geographic data produced from activities of controlling use of plant protection products, in plant health, in controlling weeds and in soil conservation
• • providing guidance for designing, monitoring and assessing the impact of particular programmes (e.g. implementing nitrate and sewage sludge directives, ragweed eradication, survey and monitoring for quarantine and other economically important pests)
• • establishing an Agro‐environmental Information and Monitoring System to support environmentally friendly farming.

The Service operates one nationwide and six regional GIS centres. Databases are now tested and operated for the Intranet. Interactive maps are planned to be publicly accessible through a map server from 2007.     

A classification methodology for the risk of weed infestation using fuzzy logic

Despite modern weed control practices, weeds continue to be a threat to agricultural production. Considering the variability of weeds, a classification methodology for the risk of infestation in agricultural zones using fuzzy logic is proposed. The inputs for the classification are attributes extracted from estimated maps for weed seed production and weed coverage using kriging and map analysis and from the percentage of surface infested by grass weeds, in order to account for the presence of weed species with a high rate of development and proliferation. The output for the classification predicts the risk of infestation of regions of the field for the next crop. The risk classification methodology described in this paper integrates analysis techniques which may help to reduce costs and improve weed control practices. Results for the risk classification of the infestation in a maize crop field are presented. To illustrate the effectiveness of the proposed system, the risk of infestation over the entire field is checked against the yield loss map estimated by kriging and also with the average yield loss estimated from a hyperbolic model.     

Potential habitat modeling for reintroduction of three native plant species in central Iran

Potential habitat modeling of endemic species is an appropriate method to maintain biodiversity,ecosystem function and rehabilitation of rangeland ecosystems.Astragalus caragana,A.cyclophyllon and A.podolobus are endemic in Iran's rangelands and some neighboring countries.The three native species could endure environmental stresses due to their distinctive ecophysiological characteristics.They play important roles in sustainable pastures production,recreation and improvement.They suffer severe threat from many factors including;grazing,agriculture and invasive exotic species.We analyzed the potential habitat of three native plant species in central Iran basing on the grid map with the resolution of 1-km.We used inventory records from field surveys,herbarium collections and 22 environmental factors to explore the environmental influences on given species distribution by Maximum entropy(Maxent) model.Maxent is a species distribution model that uses species occurrence and environmental data for predicting potential species.The results of our study indicated species occurrence has strong correlation with environmental factors such as mean temperature of wettest season,elevation and precipitation of coldest season.We evaluated the model accuracy by AUC(area under the receiver operating characteristic curve) based on an independent test data set.AUC values indicated the high power of Maxent to create potential habitat map(AUCA.caragana=0.988,AUCA.cyclophyllon=0.927,AUCA.podolobus=0.923).It is important to consider that AUC values tend to be lower for species that have broad distribution scope,such as A.podolobus distribution.Most suitable potential habitat distributions of the three species were predicted in the western and southwestern parts of rangelands in Isfahan province.Visual comparisons of the actual distribution map of the three species with produced Maxent maps represent a good agreement.In general,the model demonstrated that the occurrence of the given species is highly probable when the elevation is between 2,200 and 3,000 m and mean temperature of wettest season less than 3°C.This model,therefore,can be applied to recognize potential sites for rangeland reclamation projects.     

Computer Mapping and Analysis of Nematode Distribution1

A computer program was used to map the distribution of Longidorus and Xiphinema nematodes in the British Isles and to analyse relationships between distribution and vegetation or soil factors. Most of the records were obtained by taking soil samples from five vegetation types in each 10 km square of the Universal Transverse Mercator (UTM) maps of the British National Grid and the Irish National Grid. Nematodes were extracted from aliquots of each soil sample by a sieving and decanting technique, then killed by heat and fixed in triethanolamine formalin. A mapping program was written in FORTRAN to produce crude line-printer maps for checking and for sets of standard 80-column cards as input for the Biological Records Centre where the final maps were produced. Analysis of relationships between nematode occurrence and various biotic and abiotic factors was carried out using a standard computer program designed for social survey work and available at the Edinburgh Regional Computing Centre. The maps produced from survey data clearly defined the limits of distribution of Longidorus and Xiphinema species within the British Isles and analysis indicated factors such as soil type or vegetation which may be important in limiting their occurrence. It is suggested that similar survey and computer mapping procedures can be used to establish a European Survey of Plant Parasitic Nematodes. Un programme sur ordinateur a permis d'établir des cartes de distribution des especès de Longidorus et Xiphinema dans les Iles britanniques et danalyser les relations qui existent entre la distribution des nematodes et les facteurs biotiques et édaphiques. Les données proviennent pour la plupart d'échantillons de sol preleves par reference a cinq types de vegetation dans chacun des carres de 10 km formant le réseau cartographique de la Grande-Bretagne et de L'Irlande. Les nematodes sont extraits des echantillons de sol par une methode de tamisage, suivie d'une decantation; ils sont ensuite tues par la chaleur et fixes dans une solution de formaline-triethanolamine. Un programme cartographique a ete etabli en FORTRAN afin d'obtenir des cartes brutes imprimées qui permettent des verifications et le transfert des donnees sur cartes à 80 colonnes qui alimentent le systeme du « Biological Records Centre » dont la tiche consistera a produire les cartes definitives. Lanalyse des relations entre la distribution des nematodes et divers facteurs biotiques et abiotiques a été réalisée par un programme normalisé, en usage pour les enquctes toxicologiques du Centre régional dinformatique d'Edimbourg. Les mêmes methodes pourraient être utilisees pour L'etablissement dune etude de la distribution des nematodes au niveau europeen.     

Importance of forest buffers for preserving soil carbon and nutrient stocks in farmed landscapes along two river sites in the savannas of the Volta basin,Ghana

Understanding the impacts of agricultural land use is desired for proper management of riparian forests buffers (RFs) in savannas. In this light, we analyzed the relationship between woody plant diversity and soil properties of RFs in farmlands (FAs) and protected areas (PAs) along Afram (Guinean zone) and Tankwidi (Sudanian zone) Rivers located within the Volta sub-basin of Ghana. ALOS-AVNIR imageries were used to map RFs to facilitate sampling of soil and woody vegetation (dbh ≥5?cm) using stratified randomized design (72 plots; size: 500?m² each) for the analysis of soil physical and chemical properties and Shannon-Wiener plant species diversity. Although the fractions of sand, silt, and clay varied between the PAs and FAs, they were predominantly categorized as sandy loam. Along the Afram River, there were no significant differences in the concentrations and nutrient stocks of soil C, N, P, and K as well as the pH, moisture content, and bulk density between PA and FA. For the Tankwidi River, the concentrations and nutrient stocks of C and K significantly decreased from PA to FA while N, P, pH, bulk density, and moisture content were not different. Of the soil attributes measured C, N, P, pH, ground slope, and soil moisture had significant relationships with the diversity and density of the riparian woody plants. Controlling agricultural activities in riparian forests could preserve soil properties similar to that found in protected areas.