LIVIVO - The Search Portal for Life Sciences

zur deutschen Oberfläche wechseln
Advanced search

Search results

Result 1 - 6 of total 6

Search options

  1. Article: A comparison of three ways to assemble wall-to-wall maps from distribution models of vegetation types

    Horvath, Peter / Halvorsen, Rune / Simensen, Trond / Bryn, Anders

    GIScience & remote sensing. 2021 Nov. 17, v. 58, no. 8

    2021  

    Abstract: Distribution modeling methods are used to provide occurrence probability surfaces for modeled targets. While most often used for modeling species, distribution modeling methods can also be applied to vegetation types. However, surfaces provided by ... ...

    Abstract Distribution modeling methods are used to provide occurrence probability surfaces for modeled targets. While most often used for modeling species, distribution modeling methods can also be applied to vegetation types. However, surfaces provided by distribution modeling need to be transformed into classified wall-to-wall maps of vegetation types to be useful for practical purposes, such as nature management and environmental planning. The paper compares the performance of three methods for assembling predictions for multiple vegetation types, modeled individually, into a wall-to-wall map. The authors used grid-cell based probability surfaces from distribution models of 31 vegetation types to test the three assembly methods. The first, a probability-based method, selected for each grid cell the vegetation type with the highest predicted probability of occurrence in that cell. The second, a performance-based method, assigned the vegetation types, ordered from high to low model performance, to a fraction of the grid cells given by the vegetation type’s prevalence in the study area. The third, a prevalence-based method, differed from the performance-based method by assigning vegetation types in the order from low to high prevalence. Thus the assembly methods worked in two principally different ways: the probability-based method assigned vegetation types to grid cells in a cell-by-cell manner, and both the performance-based method and prevalence-based method assigned them in a type-by-type manner. All methods were evaluated by use of reference data collected in the field, more or less independently of the data used to parameterize the vegetation-type models. Quantity, allocation, and total disagreement, as well as proportional dissimilarity metrics, were used for evaluation of assembly methods. Overlay analysis showed 38.1% agreement between all three assembly methods. The probability-based method had the lowest total disagreement with, and proportional dissimilarity from, the reference datasets, but the differences between the three methods were small. The three assembly methods differed strongly with respect to the distribution of the total disagreement on its quantity and allocation components: the cell-by-cell assignment method strongly favored allocation disagreement and the type-by-type methods strongly favored quantity disagreement. The probability-based method best reproduced the general pattern of variation across the study area, but at the cost of many rare vegetation types, which were left out of the assembled map. By contrast, the prevalence-based and performance-based methods represented vegetation types in accordance with nationwide area statistics. The results show that maps of vegetation types with wall-to-wall coverage can be assembled from individual distribution models with a quality acceptable for indicative purposes, but all the three tested methods currently also have shortcomings. The results also indicate specific points in the methodology for map assembly that may be improved.
    Keywords data collection ; model validation ; probability ; vegetation types
    Language English
    Dates of publication 2021-1117
    Size p. 1458-1476.
    Publishing place Taylor & Francis
    Document type Article
    ZDB-ID 2209042-3
    ISSN 1943-7226 ; 1548-1603
    ISSN (online) 1943-7226
    ISSN 1548-1603
    DOI 10.1080/15481603.2021.1996313
    Database NAL-Catalogue (AGRICOLA)

    More links

    Kategorien

  2. Article: Global 10 m Land Use Land Cover Datasets: A Comparison of Dynamic World, World Cover and Esri Land Cover

    Venter, Zander S. / Barton, David N. / Chakraborty, Tirthankar / Simensen, Trond / Singh, Geethen

    Remote Sensing. 2022 Aug. 21, v. 14, no. 16

    2022  

    Abstract: The European Space Agency’s Sentinel satellites have laid the foundation for global land use land cover (LULC) mapping with unprecedented detail at 10 m resolution. We present a cross-comparison and accuracy assessment of Google’s Dynamic World (DW), ESA’ ...

    Abstract The European Space Agency’s Sentinel satellites have laid the foundation for global land use land cover (LULC) mapping with unprecedented detail at 10 m resolution. We present a cross-comparison and accuracy assessment of Google’s Dynamic World (DW), ESA’s World Cover (WC) and Esri’s Land Cover (Esri) products for the first time in order to inform the adoption and application of these maps going forward. For the year 2020, the three global LULC maps show strong spatial correspondence (i.e., near-equal area estimates) for water, built area, trees and crop LULC classes. However, relative to one another, WC is biased towards over-estimating grass cover, Esri towards shrub and scrub cover and DW towards snow and ice. Using global ground truth data with a minimum mapping unit of 250 m², we found that Esri had the highest overall accuracy (75%) compared to DW (72%) and WC (65%). Across all global maps, water was the most accurately mapped class (92%), followed by built area (83%), tree cover (81%) and crops (78%), particularly in biomes characterized by temperate and boreal forests. The classes with the lowest accuracies, particularly in the tundra biome, included shrub and scrub (47%), grass (34%), bare ground (57%) and flooded vegetation (53%). When using European ground truth data from LUCAS (Land Use/Cover Area Frame Survey) with a minimum mapping unit of <100 m², we found that WC had the highest accuracy (71%) compared to DW (66%) and Esri (63%), highlighting the ability of WC to resolve landscape elements with more detail compared to DW and Esri. Although not analyzed in our study, we discuss the relative advantages of DW due to its frequent and near real-time data delivery of both categorical predictions and class probability scores. We recommend that the use of global LULC products should involve critical evaluation of their suitability with respect to the application purpose, such as aggregate changes in ecosystem accounting versus site-specific change detection in monitoring, considering trade-offs between thematic resolution, global versus. local accuracy, class-specific biases and whether change analysis is necessary. We also emphasize the importance of not estimating areas from pixel-counting alone but adopting best practices in design-based inference and area estimation that quantify uncertainty for a given study area.
    Keywords data collection ; ecosystems ; grasses ; ice ; land cover ; land use ; land use and land cover maps ; landscapes ; shrublands ; shrubs ; snow ; surveys ; trees ; tundra ; uncertainty
    Language English
    Dates of publication 2022-0821
    Publishing place Multidisciplinary Digital Publishing Institute
    Document type Article
    ZDB-ID 2513863-7
    ISSN 2072-4292
    ISSN 2072-4292
    DOI 10.3390/rs14164101
    Database NAL-Catalogue (AGRICOLA)

    More links

    Kategorien

  3. Article: Methods for landscape characterisation and mapping: A systematic review

    Simensen, Trond / Halvorsen, Rune / Erikstad, Lars

    Land use policy. 2018 June, v. 75

    2018  

    Abstract: Due to the multidisciplinary nature of landscape research, many different systems and methods for landscape identification and classification exist. This paper provides a systematic review of 54 contemporary landscape characterisation approaches from all ...

    Abstract Due to the multidisciplinary nature of landscape research, many different systems and methods for landscape identification and classification exist. This paper provides a systematic review of 54 contemporary landscape characterisation approaches from all over the world, with the aim of identifying major methodological strategies. Multivariate statistical analyses revealed segregation of the approaches according to the landscape concept applied, the degree of observer independence and various other factors involved in the landscape characterisation process. Our review confirmed a major distinction between approaches rooted in the natural sciences and approaches rooted in the arts and the humanities. Three substantially different methodological approaches or strategies were identified: 1) ‘holistic’ landscape character assessment approaches, by which visual perception and socio-cultural aspects of the landscape are emphasised; 2) landscape characterisation methods based on a priori selection of geo-ecological and land-use-related properties of the landscape; and 3) biophysical landscape characterisation approaches which rely strongly on statistical analyses in order to identify gradients of variation in the presence and/or abundance of landscape elements and properties. Assessment of landform and the composition of natural and human landscape elements was a central part of all of the reviewed methods. A trend towards increasing observer-independence over time was identified.
    Keywords culture and humanities ; humans ; landforms ; landscapes ; multivariate analysis ; systematic review ; visual perception
    Language English
    Dates of publication 2018-06
    Size p. 557-569.
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 852476-2
    ISSN 0264-8377
    ISSN 0264-8377
    DOI 10.1016/j.landusepol.2018.04.022
    Database NAL-Catalogue (AGRICOLA)

    More links

    Kategorien

  4. Article: Composite landscape predictors improve distribution models of ecosystem types

    Simensen, Trond / Horvath, Peter / Vollering, Julien / Erikstad, Lars / Halvorsen, Rune / Bryn, Anders

    Diversity & distributions. 2020 Aug., v. 26, no. 8

    2020  

    Abstract: AIM: Distribution modelling is a useful approach to obtain knowledge about the spatial distribution of biodiversity, required for, for example, red‐list assessments. While distribution modelling methods have been applied mostly to single species, ... ...

    Abstract AIM: Distribution modelling is a useful approach to obtain knowledge about the spatial distribution of biodiversity, required for, for example, red‐list assessments. While distribution modelling methods have been applied mostly to single species, modelling of communities and ecosystems (EDM; ecosystem‐level distribution modelling) produces results that are more directly relevant for management and decision‐making. Although the choice of predictors is a pivotal part of the modelling process, few studies have compared the suitability of different sets of predictors for EDM. In this study, we compare the performance of 50 single environmental variables with that of 11 composite landscape gradients (CLGs) for prediction of ecosystem types. The CLGs represent gradients in landscape element composition derived from multivariate analyses, for example “inner‐outer coast” and “land use intensity.” LOCATION: Norway. METHODS: We used data from field‐based ecosystem‐type mapping of nine ecosystem types, and environmental variables with a resolution of 100 × 100 m. We built nine models for each ecosystem type with variables from different predictor sets. Logistic regression with forward selection of variables was used for EDM. Models were evaluated with independently collected data. RESULTS: Most ecosystem types could be predicted reliably, although model performance differed among ecosystem types. We identified significant differences in predictive power and model parsimony across models built from different predictor sets. Climatic variables alone performed poorly, indicating that the current climate alone is not sufficient to predict the current distribution of ecosystems. Used alone, the CLGs resulted in parsimonious models with relatively high predictive power. Used together with other variables, they consistently improved the models. MAIN CONCLUSIONS: Our study highlights the importance of variable selection in EDM. We argue that the use of composite variables as proxies for complex environmental gradients has the potential to improve predictions from EDMs and thus to inform conservation planning as well as improve the precision and credibility of red lists and global change assessments.
    Keywords biodiversity ; climatic factors ; decision making ; ecosystems ; elemental composition ; global change ; land use ; landscapes ; model validation ; models ; planning ; prediction ; regression analysis ; Norway
    Language English
    Dates of publication 2020-08
    Size p. 928-943.
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ZDB-ID 2020139-4
    ISSN 1472-4642 ; 1366-9516
    ISSN (online) 1472-4642
    ISSN 1366-9516
    DOI 10.1111/ddi.13060
    Database NAL-Catalogue (AGRICOLA)

    More links

    Kategorien

  5. Article: Towards a systematics of ecodiversity: The EcoSyst framework

    Halvorsen, Rune / Skarpaas, Olav / Bryn, Anders / Bratli, Harald / Erikstad, Lars / Simensen, Trond / Lieungh, Eva

    Global ecology and biogeography. 2020 Nov., v. 29, no. 11

    2020  

    Abstract: BACKGROUND: Although a standard taxonomy of organisms has existed for nearly 300 years, no consensus has yet been reached on principles for systematization of ecological diversity (i.e., the co‐ordinated variation of abiotic and biotic components of ... ...

    Abstract BACKGROUND: Although a standard taxonomy of organisms has existed for nearly 300 years, no consensus has yet been reached on principles for systematization of ecological diversity (i.e., the co‐ordinated variation of abiotic and biotic components of natural diversity). In a rapidly changing world, where nature is under constant pressure, standardized terms and methods for characterization of ecological diversity are urgently needed (e.g., to enhance precision and credibility of global change assessments). AIM: The aim is to present the EcoSyst framework, a set of general principles and methods for systematization of natural diversity that simultaneously addresses biotic and abiotic variation, and to discuss perspectives opened by this framework. INNOVATION: EcoSyst provides a framework for systematizing natural variation in a consistent manner across different levels of organization. At each ecodiversity level, EcoSyst principles can be used to establish: (a) an extensive attribute system with descriptive variables that cover all relevant sources of variation; (b) a hierarchical‐type system; and (c) a set of guidelines for land‐cover mapping that is consistent across spatial scales. EcoSyst type systems can be conceptualized as multidimensional models, by which a key characteristic (the response) is related to variation in one or more key sources of variation (predictors). EcoSyst type hierarchies are developed by a gradient‐based iterative procedure, by which the “ecodiversity distance” (i.e., the extent to which the key characteristic differs between adjacent candidate types) is standardized and the ecological processes behind observed patterns are explicitly taken into account. APPLICATION: We present “Nature in Norway” (NiN), an implementation of the EcoSyst framework for Norway for the ecosystem and landscape levels of ecodiversity. Examples of applications to research and management are given. CONCLUSION: The EcoSyst framework provides a theoretical platform, principles and methods that can complement and enhance initiatives towards a global‐scale systematics of ecodiversity.
    Keywords ecosystems ; global change ; guidelines ; land cover ; landscapes ; models ; taxonomy ; Norway
    Language English
    Dates of publication 2020-11
    Size p. 1887-1906.
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ZDB-ID 2021283-5
    ISSN 1466-8238 ; 1466-822X ; 0960-7447
    ISSN (online) 1466-8238
    ISSN 1466-822X ; 0960-7447
    DOI 10.1111/geb.13164
    Database NAL-Catalogue (AGRICOLA)

    More links

    Kategorien

  6. Article ; Online: What explains inconsistencies in field‐based ecosystem mapping?

    Naas, Adam Eindride / Halvorsen, Rune / Horvath, Peter / Wollan, Anders Kvalvåg / Bratli, Harald / Brynildsrud, Katrine / Finne, Eirik Aasmo / Keetz, Lasse Torben / Lieungh, Eva / Olson, Christine / Simensen, Trond / Skarpaas, Olav / Tandstad, Hilde Riksheim / Torma, Michal / Værland, Espen Sommer / Bryn, Anders

    Applied Vegetation Science. 2023 Jan., v. 26, no. 1 p.e12715-

    2023  

    Abstract: QUESTIONS: Field‐based ecosystem mapping is prone to observer bias, typically resulting in a mismatch between maps made by different mappers, that is, inconsistency. Experimental studies testing the influence of site, mapping scale, and differences in ... ...

    Abstract QUESTIONS: Field‐based ecosystem mapping is prone to observer bias, typically resulting in a mismatch between maps made by different mappers, that is, inconsistency. Experimental studies testing the influence of site, mapping scale, and differences in experience level on inconsistency in field‐based ecosystem mapping are lacking. Here, we study how inconsistencies in field‐based ecosystem maps depend on these factors. LOCATION: Iškoras and Guollemuorsuolu, northeastern Norway, and Landsvik and Lygra, western Norway. METHODS: In a balanced experiment, four sites were field‐mapped wall‐to‐wall to scales 1:5000 and 1:20,000 by 12 mappers, representing three experience levels. Thematic inconsistency was calculated by overlay analysis of map pairs from the same site, mapped to the same scale. We tested for significant differences between sites, scales, and experience‐level groups. Principal components analysis was used in an analysis of additional map inconsistencies and their relationships with site, scale and differences in experience level and time consumption were analysed with redundancy analysis. RESULTS: On average, thematic inconsistency was 51%. The most important predictor for thematic inconsistency, and for all map inconsistencies, was site. Scale and its interaction with site predicted map inconsistencies, but only the latter were important for thematic inconsistency. The only experience‐level group that differed significantly from the mean thematic inconsistency was that of the most experienced mappers, with nine percentage points. Experience had no significant effect on map inconsistency as a whole. CONCLUSION: Thematic inconsistency was high for all but the dominant thematic units, with potentially adverse consequences for mapping ecosystems that are fragmented or have low coverage. Interactions between site and mapping system properties are considered the main reasons why no relationships between scale and thematic inconsistency were observed. More controlled experiments are needed to quantify the effect of other factors on inconsistency in field‐based mapping.
    Keywords ecosystems ; vegetation ; Norway
    Language English
    Dates of publication 2023-01
    Publishing place John Wiley & Sons, Ltd
    Document type Article ; Online
    Note JOURNAL ARTICLE
    ZDB-ID 1445659-x
    ISSN 1402-2001
    ISSN 1402-2001
    DOI 10.1111/avsc.12715
    Database NAL-Catalogue (AGRICOLA)

    More links

    Kategorien

To top