Abstract
BackgroundThe phenomenon of tree dieback in forest ecosystems around the world, which is known to be associated with high temperatures that occur simultaneously with drought, has received much attention. Korea is experiencing a rapid rise in temperature relative to other regions. Particularly in the growth of evergreen conifers, temperature increases in winter and spring can have great influence. In recent years, there have been reports of group dieback of Pinus densiflora trees in Korea, and many studies are being conducted to identify the causes. However, research on techniques to diagnose and monitor drought stress in forest ecosystems on local and regional scales has been lacking.ResultsIn this study, we developed and evaluated an index to identify drought and high-temperature vulnerability in Pinus densiflora forests. We found the Drought Stress Index (DSI) that we developed to be effective in generally assessing the drought-reactive physiology of trees. During 2001–2016, in Korea, we refined the index and produced DSI data from a 1 × 1-km unit grid spanning the entire country. We found that the DSI data correlated with the event data of Pinus densiflora mass dieback compiled in this study. The average DSI value at times of occurrence of Pinus densiflora group dieback was 0.6, which was notably higher than during times of nonoccurrence.ConclusionsOur combination of the Standard Precipitation Index and growing degree days evolved and short- and long-term effects into a new index by which we found meaningful results using dieback event data. Topographical and biological factors and climate data should be considered to improve the DSI. This study serves as the first step in developing an even more robust index to monitor the vulnerability of forest ecosystems in Korea.
Highlights
The phenomenon of tree dieback in forest ecosystems around the world, which is known to be associated with high temperatures that occur simultaneously with drought, has received much attention
We developed a new drought index to monitor and predict stressed Pinus densiflora forests from abnormal climate factors such as high temperature and drought, called the Drought Stress Index, which is calculated from a combination of the Standardized Precipitation Index (SPI) (McKee et al 1993) and growing degree days (GDD)
The increase in autotrophic respiration (AR) due to high temperature and the decrease in gross primary productivity (GPP) caused by drought induced a sudden decline in carbon pool (cPool), which contributed to the dieback events in the two regions
Summary
The phenomenon of tree dieback in forest ecosystems around the world, which is known to be associated with high temperatures that occur simultaneously with drought, has received much attention. The phenomenon of climate-related plant dieback in various parts of the world since the 1990s has received much attention (Huang and Anderegg 2012). Other researchers have reported that the diebacks are related to high temperatures that occurred with drought (Williams et al 2013; Vicente-Serrano et al 2014; Camarero et al 2015). In the 1990s, droughts due to the sudden increase in temperature in the northwestern USA caused much damage (Breshears et al 2005; Williams et al 2010), and during 2012–2014, the strength
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