Mapping and Attributing Normalized Difference Vegetation Index Trends for Nepal

Krakauer, Nir Y.; Lakhankar, Tarendra; Anadón, José D.

doi:10.20944/preprints201709.0032.v1

Cited by 9 publications

(4 citation statements)

References 51 publications

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“…Similar types of relationships, i.e., positive with respect to temperature and negative with respect to precipitation between NDVI and climate were reported in global and regional-scale research [16,22,84,92]. Besides the temperature and precipitation, the vegetation can also be influenced by other factors in Nepal which are related to CO 2 [44], topography and human disturbance [85], moisture limitation [93], nitrogen deposition, irrigation, change in croplands, land use practices and ecological restoration. A previous study discovered positive NDVI trends in Nepal which were mainly attributed to CO 2 fertilization [44].…”

Section: Discussionsupporting

confidence: 70%

“…In our study, we also found positive NDVI trends and a strong correlation with temperature compared to the precipitation. In addition, we derived positive BCD (t C/ha) trends based on NDVI which is added value and different from the study carried out by [44] in Nepal. Nepal is a country of diverse topography, with a high climatic gradient and complex network of ecosystems where multiple factors might influence vegetation changes.…”

Section: Discussionmentioning

confidence: 98%

“…Besides the temperature and precipitation, the vegetation can also be influenced by other factors in Nepal which are related to CO 2 [44], topography and human disturbance [85], moisture limitation [93], nitrogen deposition, irrigation, change in croplands, land use practices and ecological restoration. A previous study discovered positive NDVI trends in Nepal which were mainly attributed to CO 2 fertilization [44]. In our study, we also found positive NDVI trends and a strong correlation with temperature compared to the precipitation.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Spatial and Temporal Variation of NDVI in Response to Climate Change and the Implication for Carbon Dynamics in Nepal

Baniya

Tang

Huang

et al. 2018

Forests

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Abstract:Nepal is a country of contrast, with varying altitude, climate and vegetation from the top of high mountains to the tropical forest in low lands. The terrestrial vegetation has rapidly been altered by climate change in Nepal. The spatial and temporal evolution of vegetation and its linkage to climatic variables were analyzed using the Normalized Difference Vegetation Index (NDVI) obtained from Advanced Very High Resolution Radiometer (AVHRR) sensors. A linear regression model and Sen's slope method were used to estimate NDVI trends and the Pearson correlation between NDVI and climatic variable, i.e., temperature and precipitation were calculated to identify the role of climate in vegetation changes. The carbon dynamics were also measured using a biomass carbon density estimation model. Results showed that NDVI experienced an overall increasing trend in Nepal from 1982-2015. The NDVI significantly increased at the rate of 0.0008 year −1 (p < 0.05) with seasonal variation of 0.0004 year −1 , p > 0.05; 0.0007 year −1 , p < 0.05; 0.0008 year −1 , p < 0.05 and 0.0007 year −1 , p > 0.05 in winter, pre-monsoon, monsoon and post-monsoon seasons, respectively. The NDVI relative change ratio (RCR) was 6.29% during last 34 years in Nepal. The correlation between NDVI and temperature was significantly positive (r = 0.36, p = 0.03), but there was a negative correlation with precipitation (r = −0.21, p = 0.28). Altogether, 82.20% of the study areas showed a positive correlation with temperature in which 34.97% was significant and 69.23% of the area had a negative correlation (16.35% significant, p < 0.05) with precipitation. In addition, NDVI-based carbon estimation showed that Nepal's forest total carbon stock is 685.45 × 10 6 t C (i.e., an average of 115.392 t C/ha) with an annual carbon sequestration rate of 0.10 t C/ha from 1982-2015. The results suggest that NDVI variation is more sensitive to temperature than precipitation and it is valuable to measure carbon dynamics in Nepal.

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Section: Discussionsupporting

confidence: 70%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Spatial and Temporal Variation of NDVI in Response to Climate Change and the Implication for Carbon Dynamics in Nepal

Baniya

Tang

Huang

et al. 2018

Forests

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“…e remotely sensed Normalized Difference Vegetation Index (NDVI), which is generally used as a proxy for terrestrial vegetation productivity-allowing for continuous and long-term monitoring of information on the relationship between vegetation and climate-is now one of the most widely used indicators in studies involving vegetation dynamics and ecosystem health [6][7][8]. A large number of studies have been carried out to assess the vegetation patterns around the world based on NDVI time series data [7][8][9][10][11][12][13][14]. Many scholars have explored the relationship between NDVI and climate at varying scales; however, our understanding of these processes and interactions is still limited in many areas [14,15].…”

Section: Introductionmentioning

confidence: 99%

Vegetation Response to Recent Trends in Climate and Landuse Dynamics in a Typical Humid and Dry Tropical Region under Global Change

Adepoju

Adelabu

Fashae

2019

Advances in Meteorology

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e influence of global change on vegetation cover and processes has drawn increasing attention in the past few decades. In this study, we used remotely sensed rainfall and land surface temperature to investigate the spatiotemporal pattern and trend in vegetation condition using NDVI as proxy from 2001 to 2017 in a humid and dry tropical region. We also determined the partial correlation coefficient of temperature and rainfall with NDVI and the response of NDVI to changes in landcover categories due to human activities. We found that the mean annual maximum NDVI was 0.42, decreasing at a rate of 0.06 per decade. About 27.4% of the area was found to have experienced a significant negative trend in vegetation cover, while only 0.34% exhibited significant increasing vegetation vigour. Land surface temperature increased at a mean rate of 0.75°C/decade, with higher rates in agriculture, savanna, settlements, woodlands, and riparian vegetation than in forest and mangrove vegetations. Precipitation also reduced at a mean rate of 58.69 mm/decade, with higher rates in agriculture savanna and riparian vegetation than in sahelian grasslands, mangrove, forest, and woodlands. NDVI was negatively correlated with temperature in savanna, settlements, degraded forest, and sahelian grasslands providing confirmation of ongoing land degradation. It was concluded that vegetation vigour will continue to decline under rainfall and increasing temperature conditions especially in dryer regions. e use of land surface temperature in this study is particularly valuable in highlighting areas where changes in NDVI occurred as a result of synergistic action between climate and human-induced landcover changes. Our findings underscore the importance of landuse policies that account for spatial variation in synergistic relationships between the nexus of climate and land conversion processes that influence vegetation cover change in different landcover types in tropical regions.

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Precipitation Trends over the Indus Basin

Krakauer

Lakhankar

Dars

2019

Climate

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A large population relies on water input to the Indus basin, yet basinwide precipitation amounts and trends are not well quantified. Gridded precipitation data sets covering different time periods and based on either station observations, satellite remote sensing, or reanalysis were compared with available station observations and analyzed for basinwide precipitation trends. Compared to observations, some data sets tended to greatly underestimate precipitation, while others overestimate it. Additionally, the discrepancies between data set and station precipitation showed significant time trends in such cases, suggesting that the precipitation trends of those data sets were not consistent with station data. Among the data sets considered, the station-based Global Precipitation Climatology Centre (GPCC) gridded data set showed good agreement with observations in terms of mean amount, trend, and spatial and temporal pattern. GPCC had average precipitation of about 500 mm per year over the basin and an increase in mean precipitation of about 15% between 1891 and 2016. For the more recent past, since 1958 or 1979, no significant precipitation trend was seen. Among the remote sensing based data sets, the Tropical Rainfall Measuring Mission Multi-Satellite Precipitation Analysis (TMPA) compared best to station observations and, though available for a shorter time period than station-based data sets such as GPCC, may be especially valuable for parts of the basin without station data. The reanalyses tended to have substantial biases in precipitation mean amount or trend relative to the station data. This assessment of precipitation data set quality and precipitation trends over the Indus basin may be helpful for water planning and management.

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Mapping and Attributing Normalized Difference Vegetation Index Trends for Nepal

Abstract: Global change affects vegetation cover and processes through multiple pathways. Long

Cited by 9 publications

References 51 publications

Spatial and Temporal Variation of NDVI in Response to Climate Change and the Implication for Carbon Dynamics in Nepal

Spatial and Temporal Variation of NDVI in Response to Climate Change and the Implication for Carbon Dynamics in Nepal

Vegetation Response to Recent Trends in Climate and Landuse Dynamics in a Typical Humid and Dry Tropical Region under Global Change

Precipitation Trends over the Indus Basin

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