Trends of freezing period and its main cause on the Qinghai-Tibetan Plateau from 1961 to 2018

Abstract

The ecosystems of Qinghai-Tibetan Plateau (QTP) are very sensitive to climate change because of their unique structure and function. However, little attention has been paid to variations in cold non-growing season. In this study, based on daily mean temperature from 63 meteorological stations throughout the QTP during the period 1961−2018, the spatial and temporal variations in the freezing period (FP) were investigated. The FP was de ned as the period between the date of the rst autumn freeze and the date of the rst spring thaw in the second year. Understanding how the FP changes are imperative in predicting future climate change and decision-making for implementing ecological conservation on the plateau. The results showed that the start of freezing period (SFP) exhibited a pronounced increasing trend with a rate of 0.0704 days year −1 and the end of freezing period (EFP) showed an obviously decreasing trend with a rate of −0.2537 days year −1 at the regional scale. The length of freezing period (LFP) presented a signi cant negative trend at a rate of −0.3256 days year −1 for regional scale, which was mainly attributed to the earlier EFP. Spatially, earlier EFP and shorter LFP mainly occurred in the south and north of the QTP. Furthermore, this study found that the variations in the SFP, EFP, and LFP were highly dependent on the elevation with EFP and LFP are positively correlated with elevation, while SFP is negatively correlated with elevation.

Spatial and Temporal Variability of Key Bio-Temperature Indicators and Their Effects on Vegetation Dynamics in the Great Lakes Region of Central Asia

“…An increase in DT 0 implies a decrease in frost days. Thus, a slight increase in temperature would exert a positive impact on regional vegetation growth by reducing frost days and extending the growing season [37,70]. At the same time, a significant positive correlation between annual NDVI and temperature indicators was observed at high elevations in the southeast because cold temperature is a serious constraint to vegetation growth in the region [19].…”

How much aboveground net primary production can be used for human activities in the alpine grasslands in the Three Rivers Source Region (TRSR), China?

“…The thawing of the active layer in seasonally frozen ground provides a material source for soil erosion (Gao et al 2021), whereas permafrost is rarely thawed. The ANPP WIEP of the seasonally frozen ground is similar to that of permafrost, possibly because the TRSR is dry, cold, and windy in winter, and wind erosion mainly occurs from December to April (Gong 2014), when both seasonally frozen ground and permafrost regions are in the freezing period (Zhao et al 2021) and covered by snows (Che et al 2008). The UANPP in Maqeen, which supports the majority of the plateau's population, was negative and exhibited a downward trend, which is an early warning for policy-makers.…”