1 Introduction
Karst dissolution is one of the most fundamental issues in understanding the formation and evolution of karst topography (Ren & Liu, 1983; Dixon et al., 2001; Phillips, 2005; Ford & Williams, 2007). At the same time, the karst dissolution process is also an essential part of the global carbon cycle, which plays a pivotal role in global carbon balance and carbon sink estimation (Yuan, 1995; Gombert, 2002; Goudie, & Viles, 2012; Zeng, Liu, & Kaufmann, 2019). The key to solving all these problems is to obtain a more realistic amount of karst dissolution.
Understanding and quantifying the influence of different factors on the karst dissolution is the basis of obtaining a proper amount of karst dissolution. Among these factors, the effect of drought on karst dissolution is an important factor that cannot be ignored, especially in global climate change. Observation results indicated that the drought is one of the most frequent natural disasters worldwide (Qiu, 2010; Dai, 2013; Trenberth et al., 2014; Naumann et al., 2018), which has a substantial impact on social economy and the natural environment. Tens of thousands of studies have shown that droughts are becoming more frequent and severe with climate warming (Easterling et al., 2000; IPCC, 2014; Sherwood, & Fu, 2014). Therefore, investigating the drought loss of karst dissolution has become particularly urgent and vital for karst research.
The essential characteristic of drought is the deficiency of precipitation, which is the key to the karst dissolution. Some previous studies have observed the effects of droughts on the karst dissolution, mainly caused by precipitation reduction. For example, Zhang (2010) and Wang et al. (2007) found that the karst dissolution in the dry season and rainy season have a noticeable difference. Li et al. (2012) and Lan et al. (2013) also found that the karst dissolution has a more or less decline in the dry season. Nevertheless, the specific amount of karst dissolution loss caused by drought has not been examined in detail, particularly the karst dissolution loss caused by different intensity droughts.
Many methods have developed for karst dissolution estimates and measurements over the past decades (Yuan & Cai, 1988; Plan, 2005; Ford & Williams, 2007; Gabrovšek, 2009; Moses, Robinson, & Barlow, 2014; Kirstein et al., 2016; Pardo-Igúzquiza, Dowd, & Telbisz, 2020). More popular methods to estimate and measure the karst dissolution are (1) Calculation of solutional denudation by a formula; (2) Weight loss measurement using standard tablets; (3) Short-term lowering of limestone surfaces determined by micrometric measurements; (4) Long-term lowering of bare-rock surfaces determined by measurement of surface irregularities; and (5) Cosmogenic chlorine-36 measurements. Each method has its advantages and disadvantages (Ford & Williams, 2007; Gabrovšek, 2009; Liu, 2011; Wang, Zhang, & Qin, 2013), and it might be suitable for different situations. Among these approaches, weight loss measurement using standard carbonate tablets is one of the simplest and most effective ways of estimating the karst dissolution under various environmental conditions (Yuan & Cai, 1988; Dixon et al., 2001; Plan, 2005). This method is not only the most direct way, but also can be compared with each other, and is widely used in karst research (Yuan & Cai, 1988; Dixon et al., 2001; Plan, 2005; Zhang, 2010; Hattanji et al., 2014; Krklec et al., 2016).
The karst regions of Southwest China are the most developed karst topography areas, including almost all types of karst landforms in the world. Southwest China has approximately 5.1×105 km2of karst areas in exposed or outcropped carbonate rock (Jiang, Lian, & Qin, 2014). It is about 5.8% of the total land and is distributed mainly in Guizhou and surrounding areas. This area is also a typical ecologically fragile area facing severe ecological and environmental problems (Cai, 1996; Yuan, 1997; Wang, Liu, & Zhang, 2004; Jiang, Lian, & Qin, 2014). Because of the particularity of the geological environment and climatic conditions of Southwest China karst regions, karstification is very strong and highly sensitive to changes in the external environment, especially the changes in climate conditions. Unfortunately, drought is also one of the most common natural disasters in central Southwest China (Chen, & Zhai, 2014; Han et al., 2016), known as ”Nine droughts in ten years.” Moreover, droughts in this area have an apparent upward trend in recent years (Lin et al., 2015; Liu et al., 2016). As a result, it is of great significance to study the effect of drought on karst dissolution in central Southwest China.
The present study is a first attempt to quantifying the loss impact of drought on karst dissolution and associated impact mechanism using standard carbonate tablets in a field comparative control experiment. This study focuses mainly on the amount of karst dissolution loss caused by different intensity droughts in various areas of central Southwest China. This information is crucial to the study of karst topography, protection of the karst landscape, and the karst carbon balance estimation. At the same time, we will discuss the impact mechanism of drought on karst dissolution loss, which could shed light on studying the karst process in the future.