Examining spatiotemporal salinity dynamics in the Mekong River Delta using Landsat time series imagery and a spatial regression approach

Tran, Thuong V.; Tran, Duy X.; Myint, Soe W.; Huang, Chin Wei; Pham, Hoa Viet; Luu, Tung H.; Vo, T.M.T

doi:10.1016/j.scitotenv.2019.06.056

Cited by 44 publications

(38 citation statements)

References 58 publications

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“…Vietnam is currently experiencing increasing variability in the local climate due to global changes and the growing severity of the El Nino-Southern Oscillation phenomenon, creating notable inter-annual variations in precipitation ranging from severe drought to large-scale oods (Yen et al 2019). The Mekong River Delta region is an essential region for rice production globally, but the adverse effects of salinisation have damaged rice production in recent decades (Tran et al 2019). In addition, long-term trends in rainfall and temperature patterns have been identi ed in areas with a high proportion of agricultural land.…”

Section: Discussionmentioning

confidence: 99%

Resequencing of 672 native rice accessions to explore genetic diversity and trait associations along Vietnam

Higgins

Santos

Khanh

et al. 2020

Preprint

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BACKGROUND: Vietnam possesses a vast diversity of rice landraces due to its geographical situation, latitudinal range, and a variety of ecosystems. This genetic diversity constitutes a highly valuable resource at a time when the highest rice production areas in the low-lying Mekong and Red River Deltas are enduring increasing threats from climate changes, particularly in rainfall and temperature patterns. RESULTS: We analysed 672 Vietnamese rice genomes, 616 newly sequenced, that encompass the range of rice varieties grown in the diverse ecosystems found throughout Vietnam. We described four Japonica and five Indica subpopulations within Vietnam likely adapted to the region of origin. We compared the population structure and genetic diversity of these Vietnamese rice genomes to the 3,000 genomes of Asian cultivated rice. The named Indica-5 (I5) subpopulation was expanded in Vietnam and contained lowland Indica accessions, which had with very low shared ancestry with accessions from any other subpopulation and were previously overlooked as admixtures. We scored phenotypic measurements for nineteen traits and identified 453 unique genotype-phenotype significant associations comprising twenty-one QTLs (quantitative trait loci). The strongest associations were observed for grain size traits, while weaker associations were observed for a range of characteristics, including panicle length, heading date and leaf width. CONCLUSIONS: Our results highlight differences in genome composition and trait associations among traditional Vietnamese rice accessions, which are likely the product of adaption to multiple environmental conditions and regional preferences in a very diverse country. Our results highlighted traits and their associated genomic regions that are a potential source of novel loci and alleles to breed a new generation of sustainable and resilient rice.

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Section: Discussionmentioning

confidence: 99%

Resequencing of 672 native rice accessions to explore genetic diversity and trait associations along Vietnam

Higgins

Santos

Khanh

et al. 2020

Preprint

View full text Add to dashboard Cite

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“…The space-time model can be used to examine the trend of environmental changes in the sense that the analysis generates slope coefficient values that represent the mean annual change of each environmental parameter [57]. In addition, the model includes the Mann-Kendal (MK) significance test, a tool to evaluate the statistical significance of the spatiotemporal trend.…”

Section: Spatiotemporal Regression Analysismentioning

confidence: 99%

“…Besides, a limited number of meteorological stations in the MRD also creates a challenge to monitor drought at the pixel level. Although the climatic conditions and vegetation are quite similar over this delta, criteria such as land use and land cover (LULC) types and pattern play a crucial role in drought variations [57,73,80]. Hence, it is recommended to define appropriate drought index for the region based on the multi-parameter perspective and through the application of remote sensing data and techniques.…”

Section: Assessment Of the Enhanced Drought Severity Indexmentioning

confidence: 99%

“…Among these sensors, MODIS has great temporal resolution of 1-2 days with high radiometric resolution image (12 bit) and collects data for 36 spectral bands [54,55]. Whereas, higher spatial resolution data such as Landsat (30 m) is challenged in providing an appropriate number of high-quality images [51,56] and Sentinel data is not sufficient to investigate long-term analysis as it has only been available since 2015 [57]. In fact, several studies revealed the effectiveness of MODIS data for agricultural drought assessment in tropical delta, particularly in the Mekong River Delta (MRD) as adapting to challenges of persistent cloud cover due to its advantages of temporal resolution [33,58,59].…”

mentioning

confidence: 99%

“…ET, PET, EVI, and LST), (ii) assessment of the local correlation among each other (considering also their standardized values), (iii) development of a new drought index based on the concept of the drought severity index (DSI) [24], and (iv) pattern dynamics and trend analysis in agricultural drought. The Mekong River Delta was selected as a case study because of the impact of drought along with salinity during the dry season on the region [57,73]. Besides, the comparison of EDSI and other drought indices was performed to test our hypothesis and to enhance its capabilities.…”

mentioning

confidence: 99%

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Assessing Spatiotemporal Drought Dynamics and Its Related Environmental Issues in the Mekong River Delta

Tran

Myint

et al. 2019

Remote Sensing

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Drought is a major natural disaster that creates a negative impact on socio-economic development and environment. Drought indices are typically applied to characterize drought events in a meaningful way. This study aims at examining variations in agricultural drought severity based on the relationship between standardized ratio of actual and potential evapotranspiration (ET and PET), enhanced vegetation index (EVI), and land surface temperature (LST) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) platform. A new drought index, called the enhanced drought severity index (EDSI), was developed by applying spatiotemporal regression methods and time-series biophysical data derived from remote sensing. In addition, time-series trend analysis in the 2001-2018 period, along with the Mann-Kendal (MK) significance test and the Theil Sen (TS) slope, were used to examine the spatiotemporal dynamics of environmental parameters (i.e., LST, EVI, ET, and PET), and geographically weighted regression (GWR) was subsequently applied in order to analyze the local correlations among them. Results showed that a significant correlation was discovered among LST, EVI, ET, and PET, as well as their standardized ratios (|r| > 0.8, p < 0.01). Additionally, a high performance of the new developed drought index, showing a strong correlation between EDSI and meteorological drought indices (i.e., standardized precipitation index (SPI) or the reconnaissance drought index (RDI)), measured at meteorological stations, giving r > 0.7 and a statistical significance p < 0.01. Besides, it was found that the temporal tendency of this phenomenon was the increase in intensity of drought, and that coastal areas in the study area were more vulnerable to this phenomenon. This study demonstrates the effectiveness of EDSI and the potential application of integrating spatial regression and time-series data for assessing regional drought conditions.

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Characterising spatiotemporal vegetation variations using LANDSAT time‐series and Hurst exponent index in the Mekong River Delta

Tran

Nguyen

et al. 2021

Land Degrad Dev

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Spatiotemporal analysis and monitoring of vegetation help us investigate ecological health and guide better forest conservation and land management practices for sustainable development. This paper proposes the use of spatial analysis approaches (i.e., ordinary least squares [OLS] and the Hurst exponent) combined with time-series analysis using enhanced vegetation index (EVI) data, derived from LANDSAT via the Google Earth Engine, to estimate the trends and sustainability of vegetation dynamics in the Tra Vinh Province in the Mekong River Delta. We also assessed the EVI changes connected to land change issues to examine the influence of land use conversion on vegetation dynamics. Results show that a large portion of the study area was covered by abundant vegetation (over 50% of the total area), and the increased EVI area was about 5.5-times greater than the area of EVI reduction. Additionally, vegetation sustainability was being seriously compromised (e.g., a decrease in the total area of 8,275 ha) due to several land conversion drivers such as shrimp farming, urbanisation, and industrialisation. Furthermore, results obtained from this research provide insight into the spatiotemporal dynamics of vegetation coverage and reveal the consistency of future vegetation trends. Moreover, the study also quantitatively assessed the positive impacts of Buddhist doctrines on reducing the negative trend of vegetation change in the study area. These findings can lay the ground to formulate sustainable land and environmental plans that meet the 11th, 13th and 15th Sustainable Development Goals (SDGs) (i.e., the sustainable cities and communities, the climate actions, and the life on land). Besides, the analytical procedure adopted in this study can also be applicable to any other coastal areas that require the accurate assessment of vegetation status over time.

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Examining spatiotemporal salinity dynamics in the Mekong River Delta using Landsat time series imagery and a spatial regression approach

Cited by 44 publications

References 58 publications

Resequencing of 672 native rice accessions to explore genetic diversity and trait associations along Vietnam

Resequencing of 672 native rice accessions to explore genetic diversity and trait associations along Vietnam

Assessing Spatiotemporal Drought Dynamics and Its Related Environmental Issues in the Mekong River Delta

Characterising spatiotemporal vegetation variations using LANDSAT time‐series and Hurst exponent index in the Mekong River Delta

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