Decadal assessment of agricultural drought in the context of land use land cover change using MODIS multivariate spectral index time-series data
16
Citation
73
Reference
10
Related Paper
Citation Trend
Abstract:
Using a multivariate drought index that incorporates important environmental variables and is suitable for a specific geographical region is essential to fully understanding the pattern and impacts of drought severity. This study applied feature scaling algorithms to MODIS time-series imagery to develop an integrated Multivariate Drought Index (iMDI). The iMDI incorporates the vegetation condition index (VCI), the temperature condition index (TCI), and the evaporative stress index (ESI). The 54,474 km2 Vietnamese Central Highlands region, which has been significantly affected by drought severity for several decades, was selected as a test site to assess the feasibility of the iMDI. Spearman correlation between the iMDI and other commonly used spectral drought indices (i.e. the Drought Severity Index (DSI–12) and the annual Vegetation Health Index (VHI–12)) and ground-based drought indices (i.e. the Standardized Precipitation Index (SPI–12) and the Reconnaissance Drought Index (RDI–12)) was employed to evaluate performance of the proposed drought index. Pixel-based linear regression together with clustering models of the iMDI time-series was applied to characterize the spatiotemporal pattern of drought from 2001 to 2020. In addition, a persistent area of LULC types (i.e. forests, croplands, and shrubland) during the 2001–2020 period was used to understand drought variation in relation to LULC. Results suggested that the iMDI outperformed the other spectral drought indices (r > 0.6; p < 0.005). The analysis revealed an increase in drought risk in some provinces of the Central Highlands including Gia Lai, Kon Tum, and Dak Lak. It was also found that changes in LULC patterns could minimize (reforestation) or exacerbate (deforestation) the impacts of drought. Our study suggests that applying a multivariate drought index enables a better understanding of drought patterns at the local scale. This provides valuable information for the development of appropriate land and environmental management practices that can affect and mitigate climate change effects.Keywords:
Land Cover
Shrubland
Shrubland
Pine barrens
Cite
Citations (19)
Land cover change monitoring is important for climate and environmental research. An automated approach for updating land cover maps derived from Landsat-like data is urgently needed to process large amounts of data. Change detection is an important part of the updating approach; however, pseudo-changes commonly occur because satellite images acquired in different seasons can capture phenological differences. Change detection based on normalized difference vegetation index (NDVI) time series data could avoid this problem; nevertheless it suffers from the much lower spatial resolution of the NDVI data. To address the resolution issue, this study improves an automated land cover updating approach by integrating downscaled NDVI time series data. First, Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI data at 250-m resolution are downscaled to 30 m using the NDVI linear mixing growth model. Then, the NDVI-based change detection method is used to detect the changed/unchanged areas, and the unchanged areas are removed from the changed areas that were detected using the original land cover updating approach. A case study shows that the NDVI-based change detection module sufficiently removed the pseudo-change caused by seasonal differences and improved the land cover updating result, with an increase in overall accuracy from 76.6% to 89.6%.
Land Cover
Moderate-resolution imaging spectroradiometer
Cite
Citations (30)
This year's catastrophic wildfires in southern California highlight the need for effective planning and management for fire-prone landscapes. Fire frequency analysis of several hundred wildfires over a broad expanse of California shrublands reveals that there is generally not, as is commonly assumed, a strong relationship between fuel age and fire probabilities. Instead, the hazard of burning in most locations increases only moderately with time since the last fire, and a marked age effect of fuels is observed only in limited areas. Results indicate a serious need for a re-evaluation of current fire management and policy, which is based largely on eliminating older stands of shrubland vegetation. In many shrubland ecosystems exposed to extreme fire weather, large and intense wildfires may need to be factored in as inevitable events.
Shrubland
Prescribed burn
Fire regime
Fire hazard
Cite
Citations (165)