Georeferenced Samples Research Articles

Infestation maps and spatial stability of main weed species in maize culture

A study on the spatial distribution of the major weeds in maize was carried out in 2007 and 2008 in a field located in Golegã (Ribatejo region, Portugal). The geo-referenced sampling focused on 150 points of a 10 x 10 m mesh covering an area of 1.5 ha, before herbicide application and before harvest. In the first year, 40 species (21 botanical families) were identified at seedling stage and only 22 during the last observation. The difference in species richness can be attributed to maize monoculture favouring reduction in species number. Three of the most representative species were selected for the spatial distribution analysis: Solanum nigrum, Chenopodium album and Echinochloa crus-galli. The three species showed an aggregated spatial pattern and spatial stability over both years, although the herbicide effect is evident in the distribution of some of them in the space. These results could be taken into account when planning site-specific treatments in maize.

Relationship between dichromate oxidizable and total soil organic carbon and distribution of different pools of organic carbon in Vertisols of Central India

Geo-referenced soil samples (0-15 cm) were collected from the farmers fields of Sehore (n = 120) and Vidisha (n = 156) district representing AESR 10.1 to establish the relationship between oxidizable SOC and total SOC in Vertisols of Central India and also to study the distribution of different pools of SOC as well as their relationship with crop yield. Total SOC was apportioned into different pools by using 5, 10 and 20 ml of concentrated H2SO4 that resulted in 3 acid-aqueous solution ratio of 0.5:1, 1:1 and 2:1. Also crop yields during the following winter season and rainy season from the geo-reference fields were recorded and were transformed to % relative yield. Oxidizable SOC (y) was related to total SOC (x) in the form of y = 0.825x – 0.086 (R2 = 0.958, n = 276), indicating that oxidizable SOC comprised 82.5% of the total SOC. Therefore it was recommended that a correction factor of 1.21 should be used to convert oxidizable SOC values to get the estimate of total SOC. The mean crop productivity was better related to oxidizable SOC (r = 0.5275) as compared to total SOC(r = 0.4886). The threshold and optimum values of oxidizable SOC were 3.2 and 11.2 g C/kg, respectively, whereas the threshold and optimum values for total SOC were 3.87 and 14.1 g C/kg, respectively. Among the different pools, less labile C was highly correlated (r = 0.5871) with the crop productivity, the computed threshold and optimum value for less labile C were 1.53 and 5.2 g C/kg, respectively.

Application of Large-Scale Parentage Analysis for Investigating Natal Dispersal in Highly Vagile Vertebrates: A Case Study of American Black Bears (Ursus americanus)

Understanding the factors that affect dispersal is a fundamental question in ecology and conservation biology, particularly as populations are faced with increasing anthropogenic impacts. Here we collected georeferenced genetic samples (n = 2,540) from three generations of black bears (Ursus americanus) harvested in a large (47,739 km2), geographically isolated population and used parentage analysis to identify mother-offspring dyads (n = 337). We quantified the effects of sex, age, habitat type and suitability, and local harvest density at the natal and settlement sites on the probability of natal dispersal, and on dispersal distances. Dispersal was male-biased (76% of males dispersed) but a small proportion (21%) of females also dispersed, and female dispersal distances (mean ± SE = 48.9±7.7 km) were comparable to male dispersal distances (59.0±3.2 km). Dispersal probabilities and dispersal distances were greatest for bears in areas with high habitat suitability and low harvest density. The inverse relationship between dispersal and harvest density in black bears suggests that 1) intensive harvest promotes restricted dispersal, or 2) high black bear population density decreases the propensity to disperse. Multigenerational genetic data collected over large landscape scales can be a powerful means of characterizing dispersal patterns and causal associations with demographic and landscape features in wild populations of elusive and wide-ranging species.

The Influence of Social Systems on Patterns of Mitochondrial DNA Variation in Baboons

Behavior is influenced by genes but can also shape the genetic structure of natural populations. Investigating this link is of great importance because behavioral processes can alter the genetic diversity on which selection acts. Gene flow is one of the main determinants of the genetic structure of a population and dispersal is the behavior that mediates gene flow. Baboons (genus Papio) are among the most intensely studied primate species and serve as a model system to investigate the evolution of social systems using a comparative approach. The general mammalian pattern of male dispersal and female philopatry has thus far been found in baboons, with the exception of hamadryas baboons (Papio hamadryas). As yet, the lack of data on Guinea baboons (Papio papio) creates a taxonomic gap in genus-wide comparative analyses. In our study we investigated the sex-biased dispersal pattern of Guinea baboons in comparison to hamadryas, olive, yellow, and chacma baboons using sequences of the maternally transmitted mitochondrial hypervariable region I. Analyzing whole-range georeferenced samples (N = 777), we found strong evidence for female-biased gene flow in Guinea baboons and confirmed this pattern for hamadryas baboons, as shown by a lack of genetic-geographic structuring. In addition, most genetic variation was found within and not among demes, in sharp contrast to the pattern observed in matrilocal primates including the other baboon taxa. Our results corroborate the notion that the Guinea baboons’ social system shares some important features with that of hamadryas baboons, suggesting similar evolutionary forces have acted to distinguish them from all other baboons.Electronic supplementary materialThe online version of this article (doi:10.1007/s10764-013-9725-5) contains supplementary material, which is available to authorized users.

Mapping HIV epidemics in sub-Saharan Africa with use of GPS data.

Mapping HIV epidemics in sub-Saharan Africa with use of GPS data.

<b>The use of multiple endmember spectral mixture analysis (MESMA) for the mapping of soil attributes using Aster imagery</b> - doi: 10.4025/actasciagron.v35i3.16119

Systematic, physically based acquisition of information regarding soils is required to meet increasing demand in agricultural and environmental systems. The objective of this work is to evaluate the use of multiple endmember spectral mixture analysis (MESMA) for mapping soil attributes within ASTER imagery. A total of 184 georeferenced soil samples were collected from Rafard, São Paulo State, Brazil. These points were overlain on the satellite image to collect spectral data. The laboratory and image information were then arranged and prepared by clustering samples into classes based on the following soil attributes: texture, organic matter, base saturation (V%), CEC and total iron. Following this classification, mean spectral curves were generated for each attribute class. Spectral curves were used as endmembers for the generation of maps using MESMA. Maps of the same attributes were also generated using geostatistical analyses. Based on the two generated maps, a cross-tabulation was used to evaluate the accuracy of MESMA for mapping soil attributes. Agreement was high for maps of the texture, organic matter, CEC and total iron. We conclude that the methodology used in this work was efficient for mapping soil attributes.

Modelling and mapping some soil surface properties of Central Kelkit Basin in Turkey by using Landsat-7 ETM+ images

Using remote sensing and geographical information system (GIS) tools, we investigated relationships among Landsat-7 Enhanced Thematic Mapper Plus (Landsat-7 ETM+) satellite bands and some soil surface variables of Central Kelkit Basin in Turkey. We collected 164 geo-referenced surface soil samples (0–20 cm) from field studies in 2008 and analysed the data to determine soil variables such as calcium carbonate (CaCO3), pH, electrical conductivity (EC), organic matter (OM), nitrogen (N), phosphorus (P), exchangeable potassium (EK), and texture (clay, silt, and sand). Utilizing geographic references and determined soil variables, we established a point database in GIS to overlay and extract corresponding digital number (DN) values of Landsat-7 ETM+ bands. We studied possible relationships between the soil variables and the bands' DN values by using correlation (Pearson) analysis. We found that four soil variables including pH, OM, CaCO3, and N have significant correlations with band 5 (short wave infrared) DN values. We conducted linear regression analysis to develop models for these four variables. Residual statistics and plots showed that the developed models were robust. After running the models in GIS, we mapped pH, CaCO3, OM, and N contents of the basin.

Mapping groundwater quality for irrigation in Punjab, North-West India, using geographical information system

The state of Punjab—a part of the Indus basin of the Indian subcontinent has an excellent net work of irrigation facilities. However, due to intensive cultivation it is facing a major problem with respect to quality of groundwater for irrigation. In the present investigation, geo-referenced groundwater samples were analysed to map water quality using geographical information system. Electrical conductivity varied from 0.418 to 5.754 dS m−1 with an average of 1.365 dS m−1. The carbonate ranged between 0 and 120 mg L−1, whereas bicarbonate ranged from 5 to 1,000 mg L−1. Chloride varied from 7 to 2,347 mg L−1. Calcium plus magnesium ranged from 12 to 1,216 mg L−1 with a mean value of 169 mg L−1. Sodium adsorption ratio ranged between 0.0 and 34.78 with an average of 2.66 meq L−1/2. Residual sodium carbonate varied from 0 to 21.30 meq L−1 with a standard deviation of 2.24. The Geographic Information System (GIS)-based mapping indicated that water in suitable category spatially covered 45.7 % of the state which is located mostly in the sub-mountain (Siwalik Hills), north-eastern undulating and piedmont and alluvial plain agro-eco-subregions. Marginally suitable groundwater spatially covered 46.1 % in the central alluvial plain and south-western alluvial plain agro-eco-subregions. Unsuitable groundwater covered 8.2 % of the state, mostly in the erstwhile sodic soils areas in the central alluvial plain and south-western alluvial plain agro-eco-subregions. GIS-based maps are effective in identifying hot spots which need immediate attention and call for strategic planning for sustainable management.

Mineralogy of the clay fraction of Alfisols in two slope curvatures: III - spatial variability

A good knowledge of the spatial distribution of clay minerals in the landscape facilitates the understanding of the influence of relief on the content and crystallographic attributes of soil minerals such as goethite, hematite, kaolinite and gibbsite. This study aimed at describing the relationships between the mineral properties of the clay fraction and landscape shapes by determining the mineral properties of goethite, hematite, kaolinite and gibbsite, and assessing their dependence and spatial variability, in two slope curvatures. To this end, two 100 × 100 m grids were used to establish a total of 121 regularly spaced georeferenced sampling nodes 10 m apart. Samples were collected from the layer 0.0-0.2 m and analysed for iron oxides, and kaolinite and gibbsite in the clay fraction. Minerals in the clay fraction were characterized from their X-ray diffraction (XRD) patterns, which were interpreted and used to calculate the width at half height (WHH) and mean crystallite dimension (MCD) of iron oxides, kaolinite, and gibbsite, as well as aluminium substitution and specific surface area (SSA) in hematite and goethite. Additional calculations included the goethite and hematite contents, and the goethite/(goethite+hematite) [Gt/(Gt+Hm)] and kaolinite/(kaolinite+gibbsite) [Kt/(Kt+Gb)] ratios. Mineral properties were established by statistical analysis of the XRD data, and spatial dependence was assessed geostatistically. Mineralogical properties differed significantly between the convex area and concave area. The geostatistical analysis showed a greater number of mineralogical properties with spatial dependence and a higher range in the convex than in the concave area.

The character and use of the Soros Hill Obsidian source, Antiparos (Greece)

This article details the geological and elemental character of the obsidian from the Soros Hill source on the Cycladic island of Antiparos, Greece. EDXRF was used to analyse 40 geological geo-referenced samples. The products are clearly chemically discriminated from those of the other Aegean sources, and those from the Carpathians and central Anatolia. While the obsidian is of excellent tool-making quality, the small size of its nodules seems to have made it a less attractive raw material, attested at only a handful of prehistoric sites in the central Cyclades.

Efeito da topografia na estabilidade temporal dos parâmetros do solo numa pastagem permanente mediterrânica

In order to evaluate the effect of topography on spatial and temporal stability of macronutrients, organic matter and pH of soil in Mediterranean permanent pastures, between 2004 and 2010, an experiment was carried out in a bio-diverse pasture. For geo-referenced soil sampling, a 6 ha field was divided into 20 squares, with 56 m sides. Field topography showed a significant influence on the dynamics of soil nutrients and can be used in combination with different types of agronomic information to explaining the soil nutrients variability. pH was the only soil chemical characteristic that presented a high spatial and temporal stability during the six years of the experiment. These results confirm the complex dynamic of the soil nutrients in Mediterranean pastures involving two biological systems, plants and animals, and difficult the site-specific management strategy implementation.

The impact of flow regime on the sedimentation pattern of Calabar River, South-East Nigeria.

The sedimentation pattern of the lower reaches of Calabar River, on the south east coast of Nigeria was investigated with a view to evolving criteria for recognition of their ancient counterparts. Using grain size statistical parameters, the sediment-sediment relationships and flow structure of the river were examined from twenty-five georeferenced bottom samples. Results show that the tidal channel is uniformly impacted with eroded terrestrial sediments which have been delineated into A, B, and C distinct lateral facies. Facies A and B portrayed negatively skewed and near symmetric moderately sorted sands with a considerable upstream increase in kurtosis. But, Facie C depicted near symmetric, very leptokurtic well sorted sand, representing more of terrestrial-borne sediments inferring high rate of siltation/sediment accretion. Tidal flow measurements over-spring, mean and neap tidal cycles gave 0.59 m/s highest with maximum current velocity at neap tide flowing southerly. The mean near-bottom tidal velocity indicated a maximum of 0.40 m/s, predicting that bedforms such as ripples are likely to form based on empirical relationship between flow velocity and mean grain size distribution. The observed results are geared towards understanding the impact of flow regime on sediment mobility and the preservation potential of the environment. Key words: Tidal channel, lateral facies, sediment accretion, tidal current velocities, Calabar River, Nigeria.

Genetic variation among endangered Irish red grouse (Lagopus lagopus hibernicus) populations: implications for conservation and management

Extant populations of Irish red grouse (Lagopus lagopus hibernicus) are both small and fragmented, and as such may have an increased risk of extinction through the effects of inbreeding depression and compromised adaptive potential. Here we used 19 microsatellite markers to assay genetic diversity across 89 georeferenced samples from putatively semi-isolated areas throughout the Republic of Ireland and we also genotyped 27 red grouse from Scotland using the same markers. The genetic variation within Ireland was low in comparison to previously published data from Britain and the sample of Scottish red grouse, and comparable to threatened European grouse populations of related species. Irish and Scottish grouse were significantly genetically differentiated (FST = 0.07, 95% CI = 0.04–0.10). There was evidence for weak population structure within Ireland with indications of four distinct genetic clusters. These correspond approximately to grouse populations inhabiting suitable habitat patches in the North West, Wicklow Mountains, Munster and Cork, respectively, although some admixture was detected. Pair-wise FST values among these populations ranged from 0.02 to 0.04 and the overall mean allelic richness was 5.5. Effective population size in the Munster area was estimated to be 62 individuals (95% CI = 33.6–248.8). Wicklow was the most variable population with an AR value of 5.4 alleles/locus. Local (Munster) neighbourhood size was estimated to 31 individuals corresponding to an average dispersal distance of 31 km. In order to manage and preserve Irish grouse we recommend that further fragmentation and destruction of habitats need to be prevented in conjunction with population management, including protection of the integrity of the existing population by refraining from augmenting it with individuals from mainland Britain to maximise population size.

An experimental design applied to vineyards for identifying spatially and temporally variable crop parameters

Harvesting uniform batches of grapes is required to optimize must quality as one prerequisite for premium wine production. The definition of sub-units of vineyards based on within-field variation allows unitbased vineyard management during cultivation and harvest. Essential for such vineyard management is the definition of sub-units that correspond with uniform batches of quality parameters of the fruit (e.g. berry residual sugar, anthocyanin content) at harvest time or with physiological parameters measuring the vine during berry development until ripeness. The definition requires geo-referenced sampling and parameter analysis, usually in combination with interpolation and kriging methods employed to describe spatial vineyard variation. In an attempt to develop an assay for within-variation in vineyards physiological parameters assessed through chlorophyll fluorescence measurements and leaf temperature were assessed at bloom, veraison and post veraison in a randomized block design in two vineyards of Lower Austria. A statistical model based on a repeated measurement ANOVA was developed and showed suitability for the detection and monitoring of vineyard variability throughout the vegetation period based on the maximum quantum yield of photosystem II (Fv/Fm), the maximum leaf temperature (maxT leaf ) and malic acid. These parameters allow the prospective classification of sub-units according to the vine’s vitality and may be adopted for scientific experimentation and for practical viticulture.

A comparative analysis of fine-scale genetic structure in three closely related syntopic species of the grasshopper genusCalliptamus

Landscape analysis and genetics can allow a better understanding of grasshoppers for which ecology is not very well known. We analysed landscape changes between 1990 and 2006 at two areas from southern France where three grasshopper species ( Calliptamus italicus (L., 1758), Calliptamus wattenwylianus Pantel, 1896, and Calliptamus barbarus (Costa, 1836)) occur. We then applied microsatellite markers to the study of 1200 georeferenced samples collected over both areas. We used a recent Bayesian clustering method with correlated allele frequencies to detect weak population genetic structure. We found evidence of breaks in gene flow only in C. wattenwylianus, thought to be sedentary relative to its congenerics. By using different allele frequency models and prior information to different levels of genetic differentiation for our six real data sets, our study also informs on the ability of the newly available Bayesian clustering methods model to detect weak genetic structure in natural field populations.

Integration of Georeferencing, Habitat, Sampling, and Genetic Data for Documentation of Wild Plant Genetic Resources

Plant genetic resource collections provide novel materials to the breeding and research communities. Crop wild relatives may harbor completely novel forms of allelic variation for biotic and abiotic resistance as well as masked genes for improved quality and production. This variation has been shaped by the environment from which the plant materials were collected. With detailed original source information, genetic assessments of germplasm collections can go beyond the basic measurements of collection diversity and breeding for simple traits to assessments of natural variation in environmental contexts. Availability of detailed documentation of passport, phenotypic, and genetic data increases the value of all genebank accessions. Inclusion of georeferenced sources, habitats, and sampling data in collection databases facilitates interpretation of genetic data for genebank accessions with wild origins.

Spatial variability of Cu, Mn and Zn in marginal sandy beach ridges soil

The concentrations of Mn, Cu and Zn in marginal sandy soils were spatially heterogeneous. The objective of presented study were i) to quantify the variability of Mn, Cu and Zn concentration in marginal sandy soil; and ii) to develop the pattern of that variability in kriged maps. The georeferenced soil samples (n = 26) were taken at 0 to 15 and 15 to 30 cm depths from the experimental site located at Telaga Papan Setiu, Terengganu, Peninsular Malaysia. Soil samples were analyzed for extractible Mn, Cu and Zn and spatial variability was quantified with the geostatistics. Co-efficient of variation ranged from 31 to 75% indicating the heterogeneity of Mn, Cu and Zn in soil and spatial ranges varied from 495 to 2110 m in the studied area. The geostatistical analyses showed a definable spatial structure for Mn, Cu and Zn at both the depths. Cross validation test showed accurate interpolation and 26% of the data were positively correlated for Mn, Cu and Zn in the sandy soil. Kriged maps of marginal sandy area indicated that >50% area was high in Mn content at both the depths. Very high content of Mn were found in 6.8 ha of top soil and 9.5 ha of sub soil. Maps for the Zn content showed that >50% area was low at surface and medium at lower depth of sandy soil. Study concluded that quantification of Mn, Cu and Zn variability would assist in planning of future soil sampling as well as site specific management zone based strategies for crop production on these marginal sandy soils.

Optimum size in grid soil sampling for variable rate application in site-specific management

The importance of understanding spatial variability of soils is connected to crop management planning. This understanding makes it possible to treat soil not as a uniform, but a variable entity, and it enables site-specific management to increase production efficiency, which is the target of precision agriculture. Questions remain as the optimum soil sampling interval needed to make site-specific fertilizer recommendations in Brazil. The objectives of this study were: i) to evaluate the spatial variability of the main attributes that influence fertilization recommendations, using georeferenced soil samples arranged in grid patterns of different resolutions; ii) to compare the spatial maps generated with those obtained with the standard sampling of 1 sample ha-1, in order to verify the appropriateness of the spatial resolution. The attributes evaluated were phosphorus (P), potassium (K), organic matter (OM), base saturation (V%) and clay. Soil samples were collected in a 100 × 100 m georeferenced grid. Thinning was performed in order to create a grid with one sample every 2.07, 2.88, 3.75 and 7.20 ha. Geostatistical techniques, such as semivariogram and interpolation using kriging, were used to analyze the attributes at the different grid resolutions. This analysis was performed with the Vesper software package. The maps created by this method were compared using the kappa statistics. Additionally, correlation graphs were drawn by plotting the observed values against the estimated values using cross-validation. P, K and V%, a finer sampling resolution than the one using 1 sample ha-1 is required, while for OM and clay coarser resolutions of one sample every two and three hectares, respectively, may be acceptable.

Historic (1900) seafloor composition in the Belgian–Dutch part of the North Sea: A reconstruction based on calibrated visual sediment descriptions

Concerns about human-induced degradation of marine ecosystems are presently being translated into European Directives aimed at a restoration of healthier seas. However, anthropogenic alterations are ancient and data on the pristine ecosystem are lacking, making the evaluation of their cumulative effects in the long run challenging. In the Belgian and Dutch parts of the North Sea, a historic data-set (the Gilson’s archive) exists to describe various compartments of the marine ecosystem in the first decade of the 20th century (1899–1914). The bulk of samples were acquired in the nearshore (up to 10 nautical miles off the coast) and further offshore in the Hinder banks area. In this contribution, we focus on the sediment information, which consists of 2200 visual descriptions of geo-referenced seafloor samples and 690 archived sub-samples, to reconstruct the seafloor composition 100 years ago. Estimates of mud levels, sand grain size, shell debris levels as well as occurrence of gravel, pebbles and cobbles were derived from the descriptions and standardized. Mud levels and sand grain-size categories were calibrated by means of grain-size analysis of archived samples ( n=383 analyses). Large patches of very high mud levels (50–100%) used to occur close to the shore, along the central and eastern coast. The visual sand grain-size categories display a significant trend in their median grain-size, enabling us to identify distinct patches of fine (<250 μm) and medium (250< X<500 μm) sands. High levels of shell debris were found in the offshore; in coastal waters, they fringed the high turbidity zone typical of this area. Gravel grounds were identified in gullies bordering offshore sand banks and were colonized with an abundant bushy epifauna. Long-term changes were briefly considered. The nearshore mud levels are reduced in the present-day due to specific human impacts. Thick layers of poorly consolidated mud now occur mostly in the artificially dug navigation channels, at disposal sites and around port areas. Offshore, richly colonized biogenic reefs of native flat oyster ( Ostrea edulis) were destroyed by targeted oyster fishery as early as in the 1860s. Since the 1920s, seabed disturbance caused by trawling activities steadily increased. We thereby demonstrate a degradation path from richly colonized biogenic reefs toward continuously disturbed sandy gravel grounds in the present day. Our conclusion is likely valid for many such grounds in the English Channel and southern North Sea. Major long-term changes observed thus far are clearly related to specific human activities. This reconstruction work will enable to better define the amplitude of human-induced changes in this portion of the North Sea, a necessary pre-requisite to the definition of meaningful environmental health targets.

Identification of nitrate leaching hot spots in a large area with contrasting soil texture and management

► Nitrate leaching often occurs in intensively cultivated agricultural areas. ► We studied nitrate leaching hot spats in a 36,000 ha plain in Southeastern Turkey. ► We detected six isolated nitrate leaching hot spots in the plain. ► Soil texture and irrigation occurred as the major factors of nitrate leaching. ► Alternative crop, water, and soil management practices needed adapting in these hot spots. Identification of nitrate (NO 3 ) leaching hot spots is important in mitigating environmental effect of NO 3 . Once identified, the hot spots can be further analyzed in detail for evaluating appropriate alternative management techniques to reduce impact of nitrate on groundwater. This study was conducted to identify NO 3 leaching hot spots in an approximately 36,000 ha area in Serik plain, which is used intensively for agriculture in the Antalya region of Southern Turkey. Geo-referenced water samples were taken from 161 wells and from the representative soils around the wells during the period from late May to early June of 2009. The data were analyzed by classical statistics and geostatistics. Both soil and groundwater NO 3 -N concentrations demonstrated a considerably high variation, with a mean of 10.2 mg kg −1 and 2.1 mg L −1 NO 3 -N for soil and groundwater, respectively. The NO 3 -N concentrations ranged from 0.01 to 102.5 mg L −1 in well waters and from 1.89 to 106.4 mg kg −1 in soils. Nitrate leaching was spatially dependent in the study area. Six hot spots were identified in the plain, and in general, the hot spots coincided with high water table, high sand content, and irrigated wheat and cotton. The adverse effects of NO 3 can be mitigated by switching the surface and furrow irrigation methods to sprinkler irrigation, which results in a more efficient N and water use. Computer models such as NLEAP can be used to analyze alternative management practices together with soil, aquifer, and climate characteristics to determine a set of management alternatives to mitigate NO 3 effect in these hot spot areas.