Trond Simensen

Dr. Trond Simensen

orcid

Research Focus & Metrics

Academic Career Length

7Years (2020-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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21 August 2022 in Remote Sensing
Verified
Journal Article
Open access
PDF file
ZVZander Venter
Zander Venter
DBDavid N. Barton
David N. Barton
TCTC Chakraborty
TC Chakraborty
TSTrond Simensen
Trond Simensen
GSGeethen Singh
Geethen Singh
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.

11 March 2021 in Norsk Geografisk Tidsskrift - Norwegian Journal of Geography
Verified
Journal Article
Open access
TSTrond Simensen
Trond Simensen
LELars Erikstad
Lars Erikstad
RHRune Halvorsen
Rune Halvorsen
Norwegian landscapes are changing at an increasingly rapid rate and therefore systematically structured information about observable landscape variation is required for knowledge-based management of landscape diversity. The purpose of the article is to present the first version of a complete, area covering, evidence-based, landscape type map of Norway, simultaneously addressing geoecological, bioecological and land use related variations. The type system used for the mapping is supported by systematically structured empirical evidence. The results of the mapping procedure, including the geographical distribution and descriptive statistics (abundance and areal coverage), are presented for each of the nine identified major landscape types identified based on coarse-scale landform variation. Within six inland and coastal major types, a large number of minor landscape types are defined based on the composition of geoecological, bioecological, and land use related landscape properties. The results provide new insights into the geography of Norwegian marine, coastal and inland landscapes. The authors discuss potential errors, uncertainties and limitations of the landscape type maps, and address the potential value of the new tool for research, management and planning purposes. They conclude that the results of the study might contribute to knowledge-based spatial planning and management of the unique landscape diversity of Norway.

27 June 2024 in Data in Brief
Verified
Journal Article
Open access
DTDominik Thom
Dominik Thom
WRWerner Rammer
Werner Rammer
KAKatharina Albrich
Katharina Albrich
KBKristin Braziunas
Kristin Braziunas
LDLaura Dobor
Laura Dobor
RSRupert Seidl
Rupert Seidl
Understanding the impacts of changing climate and disturbance regimes on forest ecosystems is greatly aided by the use of process-based models. Such models simulate processes based on first principles of ecology, which requires parameterization. Parameterization is an important step in model development and application, defining the characteristics of trees and their responses to the environment, i.e., their traits. For species-specific models, parameterization is usually done at the level of individual species. Parameterization is indispensable for accurately modeling demographic processes, including growth, mortality, and regeneration of trees, along with their intra- and inter-specific interactions. As it is time-demanding to compile the parameters required to simulate forest ecosystems in complex models, simulations are often restricted to the most common tree species, genera, or plant-functional types. Yet, as tree species composition might change in the future, it is important to account for a broad range of species and their individual responses to drivers of change explicitly in simulations. Thus, species-specific parameterization is a critical task for making accurate projections about future forest trajectories, yet species parameters often remain poorly documented in simulation studies. We compiled and harmonized all existing tree species parameters available for the individual-based forest landscape and disturbance model (iLand). Since its first publication in 2012, iLand has been applied in 50 peer-reviewed publications across three continents throughout the Northern Hemisphere (i.e., Europe, North America, and Asia). The model operates at individual-tree level and simulates ecosystem processes at multiple spatial scales, making it a capable process-based model for studying forest change. However, the extensive number of processes and their interactions as well as the wide range of spatio-temporal scales considered in iLand require intensive parameterization, with tree species characterized by 66 unique parameters in the model. The database presented here includes parameters for 150 temperate and boreal tree species and provenances (i.e., regional variations). Excluding missing values, the database includes a total of 9,249 individual parameter entries. In addition, we provide parameters for the individual susceptibility of tree species to wind disturbance (five parameters) for a subset of 104 tree species and provenances (498 parameter entries). To guide further model parameterization efforts, we provide an estimate of uncertainty for each species based on how thoroughly simulations with the respective parameters were evaluated against independent data. Our dataset aids the future parameterization and application of iLand, and sets a new standard in documenting parameters used in process-based forest simulations. This dataset will support model application in previously unstudied areas and can facilitate the investigation of new tree species being introduced to well-studied systems (e.g., simulating assisted migration in the context of rapid climate change). Given that many process-based models rely on similar underlying processes our harmonized parameter set will be of relevance beyond the iLand community. Our work could catalyze further research into improving the parameterization of process-based forest models, increasing the robustness of projections of climate change impacts and adaptation strategies.

10 June 2023 in Geoheritage
Verified
Journal Article
Open access
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LELars Erikstad
Lars Erikstad
DHDagmar Hagen
Dagmar Hagen
TSTrond Simensen
Trond Simensen
The Svea coal mines in Svalbard have been closed, and the area is under restoration. The goal of the landscape restoration was to enable dynamic ecological and geomorphological processes by removing roads, housing, industrial facilities, airports, landfills, and quarries that once dominated the area. Cultural heritage features, such as pre-1946 buildings, structures, and mining traces, have been preserved, while the rest of the landscape has been restored to a near-natural state. The focus has been restoring geodiversity in this arctic environment, where biotic processes are slow. Geomorphological processes such as glacial, slope, fluvial, coastal, and permafrost processes dominate and give the landscape its geological character. The objective of the restoration is not merely to re-create the landscape’s previous appearance but rather to ensure that natural processes can function as they did in the past, contributing to the ongoing development and evolution of all restored land surfaces. As of 2023, most of the area has already been restored. In areas with rapid geomorphological processes, the land will soon be dominated by these processes. Revegetation is one of the major ecological processes the restoration seeks to facilitate. Revegetation is a slow process in arctic environments, and it will take many decades before vegetation covers restored bare surfaces. The project forms a valuable baseline for studying and discussing geomorphology, landscape dynamics, geodiversity, biodiversity, and ecology for nature management and landscape restoration.

23 January 2024 in Ecosystem Services
Verified
Journal Article
Open access
ZVZander Venter
Zander Venter
BCBálint Czúcz
Bálint Czúcz
ESErik Stange
Erik Stange
MNMegan S. Nowell
Megan S. Nowell
TSTrond Simensen
Trond Simensen
DBDavid N. Barton
David N. Barton
1

1 August 2020 in Diversity and Distributions
Verified
Journal Article
Open access
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TSTrond Simensen
Trond Simensen
PHPeter Horvath
Peter Horvath
JVJulien Vollering
Julien Vollering
LELars Erikstad
Lars Erikstad
RHRune Halvorsen
Rune Halvorsen
Anders BrynAnders Bryn
Anders Bryn
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 x 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.