Greening Implication Inferred from Vegetation Dynamics Interacted with Climate Change and Human Activities over the Southeast Qinghai–Tibet Plateau

Abstract

Vegetation dynamics are sensitive to climate change and human activities, as vegetation interacts with the hydrosphere, atmosphere, and biosphere. The Yarlung Zangbo River (YZR) basin, with the vulnerable ecological environment, has experienced a series of natural disasters since the new millennium. Therefore, in this study, the vegetation dynamic variations and their associated responses to environmental changes in the YZR basin were investigated based on Normalized Difference Vegetation Index (NDVI) and Global Land Data Assimilation System (GLDAS) data from 2000 to 2016. Results showed that (1) the YZR basin showed an obvious vegetation greening process with a significant increase of the growing season NDVI (Zc = 2.31, p < 0.05), which was mainly attributed to the wide greening tendency of the downstream region that accounted for over 50% area of the YZR basin. (2) Regions with significant greening accounted for 25.4% of the basin and were mainly concentrated in the Nyang River and Parlung Tsangpo River sub-basins. On the contrary, the browning regions accounted for <25% of the basin and were mostly distributed in the urbanized cities of the midstream, implying a significant influence of human activities on vegetation greening. (3) The elevation dependency of the vegetation in the YZR basin was significant, showing that the vegetation of the low-altitude regions was better than that of the high-altitude regions. The greening rate exhibited a significantly more complicated relationship with the elevation, which increased with elevated altitude (above 3500 m) and decreased with elevated altitude (below 3500 m). (4) Significantly positive correlations between the growing season NDVI and surface air temperature were detected, which were mainly distributed in the snow-dominated sub-basins, indicating that glaciers and snow melting processes induced by global warming play an important role in vegetation growth. Although basin-wide non-significant negative correlations were found between precipitation and growing season NDVI, positive influences of precipitation on vegetation greening occurred in the arid and semi-arid upstream region. These findings could provide important information for ecological environment protection in the YZR basin and other high mountain regions.

Impact of Urban Expansion on Rain Island Effect in Jinan City, North China

“…The impact of urbanization on regional climate is due to variations in atmospheric thermal, dynamic and chemical components [6,7]. The formation of urban rainfall is dominated by urban heat island, changes in surface roughness and aerosol emissions coupled with regional topography and climate features [8][9][10][11][12][13].…”

Quantifying the contribution of climate and underlying surface changes to alpine runoff alterations associated with glacier melting

“…According to previous studies, increases in vegetation would positively contribute to increases in ET , which ultimately results in a negative contribution to runoff. Some studies have indicated that the vegetation in the entire YZRB has improved in recent decades, whereas the improvement of vegetation in the middle region was relatively significant, and variations of vegetation in the upper and lower regions were slight (Li et al, 2019; Liu, Niu, et al, 2019). In the upper region, the decreasing rate of P and the increasing rate of R t was −0.72 and 0.11 mm per year respectively, which were both statistically non‐significant ( |Z c | < 1.96).…”

“…In this study, 1997 was identified as the runoff breakpoint and was chosen as the datum point representing the baseline vegetation period (period I), and the GIMMS‐NDVI3g dataset from 1997 to 2015 was used to analyse the variations in vegetation during the change period (period II) compared to the baseline period (period I) in the upper, middle, and lower regions. An NDVI variation trend analysis coupled with a significance test was implemented according to the method proposed by Li et al (2019), and the categorized criteria of the NDVI trend are shown in Table 6. The spatial distribution of the NDVI variation trend is shown in Figure 6.…”

Modelling of Vegetation Dynamics from Satellite Time Series to Determine Proglacial Primary Succession in the Course of Global Warming—A Case Study in the Upper Martell Valley (Eastern Italian Alps)

“…Even though a general greening trend was reported in the context of climate warming for many mountain ranges in the European Alps [46,127], North America [113], High Mountain Asia [128,129] and Arctic and sub-Arctic environments [130,131], some studies found transforming forces on cold-adapted plant communities and reduction of vegetation cover, most probably related to a climate-induced temperature rise and concomitant drier conditions [129,132,133]. Drought effects can probably be precluded in our study area at least for the study year 2019, as the water potential measurements have shown more than −1.6 MPa moisture (data not shown) and thus, according to Körner [134], sufficient water availability for plants was ensured.…”