scholarly journals Spatiotemporal Variation of NDVI in the Vegetation Growing Season in the Source Region of the Yellow River, China

2020 ◽  
Vol 9 (4) ◽  
pp. 282 ◽  
Author(s):  
Mingyue Wang ◽  
Jun’e Fu ◽  
Zhitao Wu ◽  
Zhiguo Pang
Keyword(s):  
Climate Change ◽  
Vegetation Change ◽  
Yellow River ◽  
Source Region ◽  
Growing Season ◽  
The Yellow River ◽  
The Past ◽  
Significant Relationships ◽  
Precipitation And Temperature ◽  
Vegetation Variation

Research on vegetation variation is an important aspect of global warming studies. The quantification of the relationship between vegetation change and climate change has become a central topic and challenge in current global change studies. The source region of the Yellow River (SRYR) is an appropriate area to study global change because of its unique natural conditions and vulnerable terrestrial ecosystem. Therefore, we chose the SRYR for a case study to determine the driving forces behind vegetation variation under global warming. Using the Normalized Difference Vegetation Index (NDVI) and climate data, we investigated the NDVI variation in the growing season in the region from 1998 to 2016 and its response to climate change based on trend analysis, the Mann–Kendall trend test and partial correlation analysis. Finally, an NDVI–climate mathematical model was built to predict the NDVI trends from 2020 to 2038. The results indicated the following: (1) over the past 19 years, the NDVI showed an increasing trend, with a growth rate of 0.00204/a. There was an upward trend in NDVI over 71.40% of the region. (2) Both the precipitation and temperature in the growing season showed upward trends over the last 19 years. NDVI was positively correlated with precipitation and temperature. The areas with significant relationships with precipitation covered 31.01% of the region, while those with significant relationships with temperature covered 56.40%. The sensitivity of the NDVI to temperature was higher than that to precipitation. Over half (56.58%) of the areas were found to exhibit negative impacts of human activities on the NDVI. (3) According to the simulation, the NDVI will increase slightly over the next 19 years, with a linear tendency of 0.00096/a. From the perspective of spatiotemporal changes, we combined the past and future variations in vegetation, which could adequately reflect the long-term vegetation trends. The results provide a theoretical basis and reference for the sustainable development of the natural environment and a response to vegetation change under the background of climate change in the study area.

scholarly journals SPATIOTEMPORAL VARIATION OF NDVI IN THE YELLOW RIVER SOURCE REGION FROM 1998 TO 2016

2020 ◽  
Vol V-3-2020 ◽  
pp. 739-744
Author(s):  
J. Fu ◽  
M. Wang ◽  
Z. Pang ◽  
W. Jiang ◽  
J. Lu ◽  
...  
Keyword(s):  
Climate Change ◽  
Vegetation Index ◽  
Yellow River ◽  
Source Region ◽  
Growing Season ◽  
Series Data ◽  
The Yellow River ◽  
Upward Trend ◽  
Yellow River Source ◽  
Precipitation And Temperature

Abstract. Quantification of vegetation change and its coupling relationship with climate change has become the central topic in current global change researches. The Normalized Difference Vegetation Index (NDVI) time series data and meteorological data from 1998 to 2016 were collected to investigate the temporal and spatial variations of NDVI in growing season in the Yellow River source region and its response to climate change, based on the trend analysis, Mann-Kendall test and correlation analysis．The results indicated that: (1) In the past 19 years, the average NDVI in the region showed a slow increase, with a growth rate of 0.002/a and a catastrophe point in 2005, and the area with an upward trend accounted for 71.4% of the total area. (2) The climate of the area had been becoming warm and moist since the recent 19 years, both precipitation and temperature in growing season showed an upward trend. The partial correlation analysis showed that NDVI was positively correlated with precipitation and temperature, significantly relevant area accounting for 31.01% and 56.40% of the total area individually. The sensitivity of NDVI to temperature was higher than that of precipitation. According to residual analysis over the 19 years, human activities had negative effects on NDVI accounting 53.58% of the study area, and the implementation of a series of ecological protection engineering measures was the main cause leading to an increasing trend of NDVI after 2005.

scholarly journals Impact of Land Cover Types on Riverine CO2 Outgassing in the Yellow River Source Region

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2243
Author(s):  
Mingyang Tian ◽  
Xiankun Yang ◽  
Lishan Ran ◽  
Yuanrong Su ◽  
Lingyu Li ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Cover ◽  
Yellow River ◽  
Stream Water ◽  
Source Region ◽  
The Yellow River ◽  
Co2 Efflux ◽  
Land Cover Types ◽  
Yellow River Source ◽  
Alpine Rivers

Under the context of climate change, studying CO2 emissions in alpine rivers is important because of the large carbon storage in these terrestrial ecosystems. In this study, riverine partial pressure of CO2 (pCO2) and CO2 emission flux (FCO2) in the Yellow River source region (YRSR) under different landcover types, including glaciers, permafrost, peatlands, and grasslands, were systematically investigated in April, June, August, and October 2016. Relevant chemical and environmental parameters were analyzed to explore the primary controlling factors. The results showed that most of the rivers in the YRSR were net CO2 source, with the pCO2 ranging from 181 to 2441 μatm and the FCO2 ranging from −50 to 1574 mmol m−2 d−1. Both pCO2 and FCO2 showed strong spatial and temporal variations. The highest average FCO2 was observed in August, while the lowest average was observed in June. Spatially, the lowest FCO2 were observed in the permafrost regions while the highest FCO2 were observed in peatland. By integrating seasonal changes of the water surface area, total CO2 efflux was estimated to be 0.30 Tg C year−1. This indicates that the YRSR was a net carbon source for the atmosphere, which contradicts previous studies that conclude the YRSR as a carbon sink. More frequent measurements of CO2 fluxes, particularly through several diel cycles, are necessary to confirm this conclusion. Furthermore, our study suggested that the riverine dissolved organic carbon (DOC) in permafrost (5.0 ± 2.4 mg L−1) is possibly derived from old carbon released from permafrost melting, which is equivalent to that in peatland regions (5.1 ± 3.7 mg L−1). The degradation of DOC may have played an important role in supporting riverine CO2, especially in permafrost and glacier-covered regions. The percent coverage of corresponding land cover types is a good indicator for estimating riverine pCO2 in the YRSR. In view of the extensive distribution of alpine rivers in the world and their sensitivity to climate change, future studies on dynamics of stream water pCO2 and CO2 outgassing are strongly needed to better understand the global carbon cycle.

scholarly journals Using Budyko-Type Equations for Separating the Impacts of Climate and Vegetation Change on Runoff in the Source Area of the Yellow River

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3418
Author(s):  
Dan Yan ◽  
Zhizhu Lai ◽  
Guangxing Ji
Keyword(s):  
Climate Change ◽  
Human Activities ◽  
Vegetation Change ◽  
Yellow River ◽  
Climatic Factors ◽  
Source Area ◽  
The Yellow River ◽  
Vegetation Changes ◽  
Potential Evaporation ◽  
Runoff Change

Assessing the contribution rates of climate change and human activities to the runoff change in the source area of the Yellow River can provide support for water management in the Yellow River Basin. This paper firstly uses a multiple linear regression method to evaluate the contribution rates of climate change and human activities to the vegetation change in the source area of the Yellow River. Next, the paper uses the Budyko hypothesis method to calculate the contribution rates of climatic factors (including precipitation, potential evaporation, and subsequent vegetation changes) and vegetation changes caused by human activities to the runoff change of the Tangnaihai Hydrometric Station. The results showed that: (1) the annual runoff and precipitation in the source area of the Yellow River have a downward trend, while the annual potential evaporation and NDVI (Normalized Difference Vegetation Index) show an increasing trend; (2) The contribution rates of climate change and human activities to the vegetation change in the source area of the Yellow River is 62.79% and 37.21%, respectively; (3) The runoff change became more and more sensitive to changes in climate and underlying surface characteristic parameters; (4) The contribution rates of climatic factors (including precipitation, potential evaporation, and subsequent vegetation changes) and vegetation changes caused by human activities to the runoff change at Tangnaihai Hydrological Station are 75.33% and 24.67%, respectively; (5) The impact of precipitation on runoff reduction is more substantial than that of potential evaporation.

scholarly journals RESEARCH ON THE VARIATION CHARACTERISTICS OF VEGETATION CHANGE AND ITS TERRAIN INFLUENCE FACTORS IN ALPINE GRASSLAND IN THE SOURCE REGION OF THE YELLOW RIVER

2020 ◽  
Vol XLII-3/W10 ◽  
pp. 479-485
Author(s):  
Q. T. Qin ◽  
J. J. Chen
Keyword(s):  
Spatial Distribution ◽  
Vegetation Change ◽  
Yellow River ◽  
Source Region ◽  
Synthesis Method ◽  
Alpine Grassland ◽  
Ecological Environment ◽  
Vegetation Coverage ◽  
The Yellow River ◽  
Variation Characteristics

Abstract. The source region of the Yellow River is an important ecological barrier in China. Since the 1990s, under the influence of various factors, its runoff has decreased and the ecological environment has deteriorated, which has attracted great attention of governments. Vegetation is the general term of plant communities covering the surface, which is the natural link between the atmosphere, water and soil. It plays an important role in air regulation, soil conservation and maintaining the stability of the whole ecosystem. Therefore, the study on the differential characteristics and topographic influencing factors of alpine grassland change in the source region of the Yellow River can provide reference for the ecological environment protection in -this region in the future. Based on the remote sensing data of MODIS NDVI, we studied the spatial distribution pattern and temporal variation characteristics of vegetation coverage in the source region of the Yellow River from 2000 to 2009 by means of maximum synthesis method, pixel dichotomy model method and trend analysis method. Furthermore, combined with DEM topographic elevation data, we discussed the influence of topographic factors such as elevation, slope and aspect on fractional vegetation cover (FVC) change. The results showed that: (1) From 2000 to 2009, the FVC in the source region of the Yellow River fluctuated upward, showing the spatial distribution characteristics of the southeast region > the central region > the northwest region; (2) During the ten years from 2000 to 2009, the almost constant of FVC accounted for the largest area, and the areas with increasing FVC mainly concentrated in the northeast and northwest of the studied region, the areas with reduced vegetation coverage were scattered in various places in the studied region, mainly in the form of minimal patches or spots; (3) Different terrain factors had different effects on FVC and the effect of altitude on FVC changes was significantly greater than that of slope and aspect. With the increase of altitude, the proportion of significant reduction in FVC increased firstly and then decreased, while the proportion of significant increase in FVC was decreasing and the proportion of almost unchanged in FVC was increasing; With the increase of slope, the proportion in the above three cases (significant reduction, significant increase and almost unchanged in FVC) was increased, decreased gradually and fluctuated respectively. Under different aspect, the proportion in the above three cases varied little, fluctuating only within 1%.

Impacts of climate change on hydrology in the Yellow River source region, China

2018 ◽  
Vol 11 (3) ◽  
pp. 916-930 ◽  
Author(s):  
Junliang Jin ◽  
Guoqing Wang ◽  
Jianyun Zhang ◽  
Qinli Yang ◽  
Cuishan Liu ◽  
...  
Keyword(s):  
Climate Change ◽  
Yellow River ◽  
Source Region ◽  
Maximum Temperature ◽  
Daily Minimum Temperature ◽  
The Yellow River ◽  
Vic Model ◽  
Increasing Trend ◽  
The Future ◽  
Yellow River Source

Abstract Variations of precipitation, temperature, and runoff in the Yellow River source region were analyzed with the Mann–Kendall and Spearman rank correlation tests over the past 60 years. Based on the seven climate scenarios from CMIP5 climate models under RCP2.6, RCP4.5, and RCP8.5, responses of hydrological process to climate change were simulated using the Variable Infiltration Capacity (VIC) model. Variation analysis results indicated that recorded temperature presented significant increasing trend. Daily minimum temperature presented higher increasing trend than daily maximum temperature. Annual gross precipitation presented minor increasing and annual runoff presented minor decreasing. The VIC model performed well on simulating monthly discharge at Tangnaihai station, with NSE of 0.91 and 0.93 in calibration and validation periods, respectively. The projected annual mean temperature would rise (with 25th and 75th percentiles) 1.07–1.32 °C, 1.76–2.33 °C, 3.45–4.29 °C, annual precipitation is expected to increase 3.43%–11.77%, 8.05%–17.27%, 12.84%–27.89%, and runoff would moderately increase with high variability of 0.82%–14.26%, −3.41%–19.14%, 1.43%–38.26% relative to the baseline of 1961–1990 under each RCP in the 2080s, respectively. The inhomogeneity of runoff may increase in the future. Many more droughts and floods under climate change may threaten social development in this region in the future.

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