Abstract
Climate changes, especially increased temperatures, and precipitation changes, have significant impacts on vegetation phenology. However, the response of vegetation phenology to the extreme climate in the Loess Plateau in Northwest China remains poorly quantified. The research described here analyzed the spatial change in vegetation phenology and the response of vegetation phenology to climate change in the Loess Plateau from 2001 to 2018, using data from seven extreme climate indices based on the ridge regression method. The results showed that extreme climate indexes, TNn (yearly minimum value of the daily minimum temperature), TXx (yearly maximum value of the daily maximum temperature), and RX5day (yearly maximum consecutive five-day precipitation) progressively increased from 2001 to 2018 in the Loess Plateau region, but decrease trend was found in DRT (diurnal temperature range). The start of the growing season (SOS) of vegetation gradually advanced with precipitation from northwest to southeast, and the rate was +0.38 d/a. The overall vegetation end of the growing season (EOS) was delayed, and the trend was −2.83 d/a. The sensitivity of the different vegetation phenology to different extreme weather indices showed obvious spatial differences, the sensitivity coefficient of SOS being mainly positive in the region, whereas the sensitivity coefficient of EOS was negative generally. More sensitivity was found in the EOS to extreme climate indexes than in the SOS. Forest, shrubland and grassland have similar responses to DRT and TNn; namely, both SOS and EOS are advanced with the increase in DRT and delayed with the increase in TNn (the sensitivity coefficient is quite different) but have different responses to RX5day and TXx. These results reveal that extreme climate events have a greater impact on vegetation EOS than on vegetation SOS, with these effects varying with vegetation types. This research can provide a scientific basis for formulating a scientific basis for regional vegetation restoration strategies and disaster prediction on the Loess Plateau.
Highlights
IntroductionThe IPCC (Intergovernmental Panel on Climate Change) Fifth Assessment Report states that most parts of the world are experiencing climate change, especially sustained warming (the global average surface temperature increased by 0.72 ◦ C from 1951 to 2012) [1,2]
The slope of the diurnal temperature range (DRT) index fell at a rate of −2.5 ◦ C/10a, whereas the temperature indices Max Tmax (TXx), Max Tmin (TNx), Min Tmax (TXn), and Min Tmin (TNn) increased at the rates of +2.4 ◦ C/10a, +3.7 ◦ C/10a, +2.9 ◦ C/10a, and +5.0 ◦ C/10a, respectively
We focused on the phenological change affected by extreme climate indices, but, in the process of analysis, we found that the advance of vegetation start of the growing season (SOS) by extreme climate indices may indirectly lead to the advance of vegetation end of the growing season (EOS); after the vegetation EOS is affected by extreme climate in the current year, it may lead to changes in vegetation SOS in the following year
Summary
The IPCC (Intergovernmental Panel on Climate Change) Fifth Assessment Report states that most parts of the world are experiencing climate change, especially sustained warming (the global average surface temperature increased by 0.72 ◦ C from 1951 to 2012) [1,2]. Climate change includes meaning climate change and extreme climate change [3,4]. Some studies have shown that the impacts of extreme weather events are more obvious and direct than climate averages with increased frequency and intensity of extreme climate events [2,5]. Based on global climate change, more and more scholars devote themselves to research the dynamics of vegetation and its response to climate change [5].
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