Sophie Thiam

Dr. Sophie Thiam


Research Focus & Metrics

Academic Career Length

5Years (2022-Present)

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

Representative Publications

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1 January 2004 in Environmental Pollution
Verified
Journal Article
Closed access
Lammert KooistraLammert Kooistra
Lammert Kooistra
Eric SalasEric Salas
Eric Salas
JCJan Clevers
Jan Clevers
RWR Wehrens
R Wehrens
RLR. S. E. W. Leuven
R. S. E. W. Leuven
LBL.M.C Buydens
L.M.C Buydens

1 October 2004 in International Journal of Remote Sensing
Verified
Journal Article
Closed access
JCJan Clevers
Jan Clevers
Lammert KooistraLammert Kooistra
Lammert Kooistra
Eric SalasEric Salas
Eric Salas
One of the major environmental problems resulting from the regular flooding of rivers in Europe is the heavy metal contamination of soils. Various studies have shown that soil contamination may influence plant physiology and, through changes in leaf pigment concentrations, influence reflectance spectra. The main objective of this case study was to study whether the red-edge position (REP) of vegetation spectra may provide information on soil contamination by heavy metals in river floodplains. The use of the maximum first derivative, smoothing methods (like polynomial fitting and the inverted Gaussian function) and interpolation methods based on just a few spectral bands were evaluated for a test site in the floodplain of the river Waal in the Netherlands. On selected transects, heavy metal concentrations of soil samples and reflectance spectra of the growing vegetation using a field spectroradiometer were measured. A significant negative correlation between the REP and heavy metal concentration was found using the maximum first derivative method (R 2=0.64). The first derivative spectra in this study showed the presence of more than one peak within the red-edge region, as found by other authors. This phenomenon requires further detailed research using very fine spectral measurements.

22 May 2020 in Geo-spatial Information Science
Verified
Journal Article
Open access
Eric SalasEric Salas
Eric Salas
Researchers continually demonstrated through published literature how LiDAR could create unparalleled measurements of ecosystem structure and forest height. There are a number of studies conducted utilizing waveform LiDAR products for terrestrial monitoring, but those that deal specifically with the assessment of space-borne waveform LiDAR for monitoring and modeling of phenology is very limited. This review highlights the waveform LiDAR system and looks into satellite sensors that could link waveform LiDAR and vegetation phenology, such as the proposed NASA’s Global Ecosystem Dynamics Investigation (GEDI) and the Japanese Experimental Module (JEM)-borne LiDAR sensor named MOLI (Multi-footprint Observation LIDAR and Imager). Further, this work examines the richness and utility of the waveform returns and proposes a spline-function-derived model that could be exploited for estimating the leaf-shooting date. The new approach may be utilized for ecosystem-level phenological studies.

24 April 2018 in Ecology and Evolution
Verified
Journal Article
Open access
PDF file
Eric SalasEric Salas
Eric Salas
RVRaul Valdez
Raul Valdez
SMStefan Michel
Stefan Michel
KBKenneth G. Boykin
Kenneth G. Boykin
Identifying the factors predicting the high‐elevation suitable habitats of Central Asian argali wild sheep and how these suitable habitats are affected by the changing climate regimes could help address conservation and management efforts and identify future critical habitat for the species in eastern Tajikistan. This study used environmental niche models (ENMs) to map and compare potential present and future distributions of suitable environmental conditions for Marco Polo argali. Argali occurrence points were collected during field surveys conducted from 2009 to 2016. Our models showed that terrain ruggedness and annual mean temperature had strong correlations on argali distribution. We then used two greenhouse gas concentration trajectories (RCP 4.5 and RCP 8.5) for two future time periods (2050 and 2070) to model the impacts of climate change on Marco Polo argali habitat. Results indicated a decline of suitable habitat with majority of losses observed at lower elevations (3,300–4,300 m). Models that considered all variables (climatic and nonclimatic) predicted losses of present suitable areas of 60.6% (6,928 km2) and 63.2% (7,219 km2) by 2050 and 2070, respectively. Results also showed averaged habitat gains of 46.2% (6,106 km2) at much higher elevations (4,500–6,900 m) and that elevational shifts of habitat use could occur in the future. Our results could provide information for conservation planning for this near threatened species in the region.

21 January 2016 in Remote Sensing
Verified
Journal Article
Open access
PDF file
Eric SalasEric Salas
Eric Salas
KBKenneth Boykin
Kenneth Boykin
RVRaul Valdez
Raul Valdez
We tested the Moment Distance Index (MDI) in combination with texture features for the summer vegetation mapping in the eastern Pamir Mountains, Tajikistan using the 2014 Landsat OLI (Operational Land Imager) image. The five major classes identified were sparse vegetation, medium-dense vegetation, dense vegetation, barren land, and water bodies. By utilizing object features in a random forest (RF) classifier, the overall classification accuracy of the land cover maps were 92% using a set of variables including texture features and MDI, and 84% using a set of variables including texture but without MDI. A decrease of the Kappa statistics, from 0.89 to 0.79, was observed when MDI was removed from the set of predictor variables. McNemar’s test showed that the increase in the classification accuracy due to the addition of MDI was statistically significant (p < 0.05). The proposed method provides an effective way of discriminating sparse vegetation from barren land in an arid environment, such as the Pamir Mountains.

31 March 2022 in Sustainability
Verified
Journal Article
Open access
PDF file
Eric SalasEric Salas
Eric Salas
STSophie Thiam
Sophie Thiam
NHNina Rholan Hounguè
Nina Rholan Hounguè
Adrian AlmoradieAdrian Almoradie
Adrian Almoradie
SVSarah Verleysdonk
Sarah Verleysdonk
KKKossi KOMI
Kossi KOMI
Integrating both modeling approach and stakeholders’ perspectives to derive past and future trends of land use land cover (LULC) is a key to creating more realistic results on LULC change trajectories and can lead to the implementation of appropriate management measures. This article assessed the past changes of LULC in the Mono River catchment using Landsat images from the years 1986, 2000, 2010, and 2020 by performing Machine Learning Classification Method Random Forest (RF) technique, and using Markov chain method and stakeholder’s perspective to simulate future LULC changes for the years 2030 and 2050. LULC was classified as savanna, cropland, forest, water bodies, and settlement. The results showed that croplands and forests areas declined from 2020 to 2050 with decreases of −7.8% and −1.9%, respectively, a modest increase in settlement (1.3%), and savanna was the dominant LULC in the study region with an increase of 8.5%. From stakeholders’ perspective, rapid population growth, deforestation, rainfall variability/flood, urbanization, and agricultural expansion were the most important drivers associated with the observed LULC changes in the area. Other factors, such as lack of political commitment, distance to river, and elevation were also mentioned. Additionally, most the land-use scenarios identified by stakeholders would intensify land degradation and reduce ecosystem services in the area. By considering all of these potential LULC changes, decision-makers need to develop and implement appropriate solutions (e.g., land use planning strategies, reforestation campaigns, forest protection measures) in order to limit the negative effects of future LULC changes.