scholarly journals Alpine Cold Vegetation Response to Climate Change in the Western Nyainqentanglha Range in 1972–2009

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Xu Wang ◽  
Ziyong Sun ◽  
Ai-Guo Zhou
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Remote Sensing Data ◽  
Vegetation Coverage ◽  
Ecosystem Change ◽  
The Tibetan Plateau ◽  
Mountain Areas ◽  
Vegetation Fraction ◽  
The Past ◽  
Spectral Mixture

The Tibetan Plateau is regarded as one of the most climatic-sensitive regions all over the world. Long-term remote sensing data enable us to monitor spatial-temporal change in this area. The vegetation changes of the western Nyainqentanglha region were detected by using RS and GIS techniques. And the vegetation coverage was derived by the NDVI-SMA (spectral mixture analysis) methods. An incensement of vegetation was observed in the mountain areas during 1972–2009 with a mean vegetation coverage of 24.87%, 35.89%, and 42.88% in 30/09/1972, 14/09/1991, and 30/08/2009, respectively. The vegetation fraction increased by 18% in the period of 1972–2009. The bin with the elevation between 4400 and 5200 m had the highest vegetation coverage. This may be the result of the mountain effect. Alpine vegetation had a trend to increase and expand to higher altitudes with the climate change in the past 40 years. The variation appears to be associated with an increase in mean temperature of 0.05°C per year and an increase in precipitation of 1.83 mm per year in the growing season of the past four decades. The results provide further evidence of alpine ecosystem change due to climate change in the central Tibetan Plateau.

scholarly journals Modeling CH4 Emissions from Natural Wetlands on the Tibetan Plateau over the Past 60 Years: Influence of Climate Change and Wetland Loss

Atmosphere ◽  
2016 ◽  
Vol 7 (7) ◽  
pp. 90 ◽  
Author(s):  
Tingting Li ◽  
Qing Zhang ◽  
Zhigang Cheng ◽  
Zhenfeng Ma ◽  
Jia Liu ◽  
...  
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Wetland Loss ◽  
The Tibetan Plateau ◽  
Ch4 Emissions ◽  
The Past ◽  
Natural Wetlands

scholarly journals Comparison of Different Multispectral Sensors for Photosynthetic and Non-Photosynthetic Vegetation-Fraction Retrieval

2020 ◽  
Vol 12 (1) ◽  
pp. 115 ◽  
Author(s):  
Cuicui Ji ◽  
Xiaosong Li ◽  
Huaidong Wei ◽  
Sike Li
Keyword(s):  
Mixture Model ◽  
Near Infrared ◽  
Scale Effects ◽  
Remote Sensing Data ◽  
Vegetation Coverage ◽  
Landsat 8 ◽  
Wide Field ◽  
Vegetation Fraction ◽  
Spectral Mixture ◽  
Multispectral Sensors

It is very difficult and complex to acquire photosynthetic vegetation (PV) and non-PV (NPV) fractions (fPV and fNPV) using multispectral satellite sensors because estimations of fPV and fNPV are influenced by many factors, such as background-noise interference of pixel-, spatial-, and spectral-scale effects. In this study, comparisons between Sentinel-2A Multispectral Instrument (S2 MSI), Landsat-8 Operational Land Imager (L8 OLI), and GF1 Wide Field View (GF1 WFV) sensors for retrieving sparse photosynthetic and non-photosynthetic vegetation coverage are presented. The analysis employed a linear spectral-mixture model (LSMM) and nonlinear spectral-mixture model (NSMM) to unmix pixels with different spectral and spatial resolution images based on field endmembers; the estimated endmember fractions were later validated with reference to fraction measurements. The results demonstrated that: (1) with higher spatial and spectral resolution, the S2 MSI sensor had a clear advantage for retrieving PV and NPV fractions compared to L8 OLI and GF1 WFV sensors; (2) through incorporating more red edge (RE) and near-infrared (NIR) bands, the accuracy of NPV fraction estimation could be greatly improved; (3) nonlinear spectral mixing effects were not obvious on the 10–30 m spatial scale for desert vegetation; (4) in arid regions, a shadow endmember is a significant factor for sparse vegetation coverage estimated with remote-sensing data. The estimated NPV fractions were especially affected by the shadow effects and could increase root mean square by 50%. The utilized approaches in the study could effectively assess the performance of major multispectral sensors to extract fPV and fNPV through the novel method of spectral-mixture analysis.

scholarly journals New perspective on spring vegetation phenology and global climate change based on Tibetan Plateau tree-ring data

2017 ◽  
Vol 114 (27) ◽  
pp. 6966-6971 ◽  
Author(s):  
Bao Yang ◽  
Minhui He ◽  
Vladimir Shishov ◽  
Ivan Tychkov ◽  
Eugene Vaganov ◽  
...  
Keyword(s):  
Climate Change ◽  
Remote Sensing ◽  
Tibetan Plateau ◽  
Tree Ring ◽  
Remote Sensing Data ◽  
Growing Season ◽  
The Tibetan Plateau ◽  
Vegetation Phenology ◽  
Sensing Data ◽  
Tree Ring Data

Phenological responses of vegetation to climate, in particular to the ongoing warming trend, have received much attention. However, divergent results from the analyses of remote sensing data have been obtained for the Tibetan Plateau (TP), the world’s largest high-elevation region. This study provides a perspective on vegetation phenology shifts during 1960–2014, gained using an innovative approach based on a well-validated, process-based, tree-ring growth model that is independent of temporal changes in technical properties and image quality of remote sensing products. Twenty composite site chronologies were analyzed, comprising about 3,000 trees from forested areas across the TP. We found that the start of the growing season (SOS) has advanced, on average, by 0.28 d/y over the period 1960–2014. The end of the growing season (EOS) has been delayed, by an estimated 0.33 d/y during 1982–2014. No significant changes in SOS or EOS were observed during 1960–1981. April–June and August–September minimum temperatures are the main climatic drivers for SOS and EOS, respectively. An increase of 1 °C in April–June minimum temperature shifted the dates of xylem phenology by 6 to 7 d, lengthening the period of tree-ring formation. This study extends the chronology of TP phenology farther back in time and reconciles the disparate views on SOS derived from remote sensing data. Scaling up this analysis may improve understanding of climate change effects and related phenological and plant productivity on a global scale.

scholarly journals Contrasting Evolution Patterns of Endorheic and Exorheic Lakes on the Central Tibetan Plateau and Climate Cause Analysis during 1988–2017

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1962
Author(s):  
Zhilong Zhao ◽  
Yue Zhang ◽  
Zengzeng Hu ◽  
Xuanhua Nie
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Climatic Factors ◽  
Global Climate ◽  
Rapid Expansion ◽  
Annual Precipitation ◽  
The Tibetan Plateau ◽  
Lake Area ◽  
Climate Change Research ◽  
Mean Temperature

The alpine lakes on the Tibetan Plateau (TP) are indicators of climate change. The assessment of lake dynamics on the TP is an important component of global climate change research. With a focus on lakes in the 33° N zone of the central TP, this study investigates the temporal evolution patterns of the lake areas of different types of lakes, i.e., non-glacier-fed endorheic lakes and non-glacier-fed exorheic lakes, during 1988–2017, and examines their relationship with changes in climatic factors. From 1988 to 2017, two endorheic lakes (Lake Yagenco and Lake Zhamcomaqiong) in the study area expanded significantly, i.e., by more than 50%. Over the same period, two exorheic lakes within the study area also exhibited spatio-temporal variability: Lake Gaeencuonama increased by 5.48%, and the change in Lake Zhamuco was not significant. The 2000s was a period of rapid expansion of both the closed lakes (endorheic lakes) and open lakes (exorheic lakes) in the study area. However, the endorheic lakes maintained the increase in lake area after the period of rapid expansion, while the exorheic lakes decreased after significant expansion. During 1988–2017, the annual mean temperature significantly increased at a rate of 0.04 °C/a, while the annual precipitation slightly increased at a rate of 2.23 mm/a. Furthermore, the annual precipitation significantly increased at a rate of 14.28 mm/a during 1995–2008. The results of this study demonstrate that the change in precipitation was responsible for the observed changes in the lake areas of the two exorheic lakes within the study area, while the changes in the lake areas of the two endorheic lakes were more sensitive to the annual mean temperature between 1988 and 2017. Given the importance of lakes to the TP, these are not trivial issues, and we now need accelerated research based on long-term and continuous remote sensing data.

Spring phenology outweighed climate change in determining autumn phenology on the Tibetan Plateau

2021 ◽  
Vol 41 (6) ◽  
pp. 3725-3742
Author(s):  
Jie Peng ◽  
Chaoyang Wu ◽  
Xiaoyue Wang ◽  
Linlin Lu
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
The Tibetan Plateau ◽  
Spring Phenology

scholarly journals Seasonal Response of Grasslands to Climate Change on the Tibetan Plateau

PLoS ONE ◽  
2012 ◽  
Vol 7 (11) ◽  
pp. e49230 ◽  
Author(s):  
Haiying Yu ◽  
Jianchu Xu ◽  
Erick Okuto ◽  
Eike Luedeling
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
The Tibetan Plateau
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