4.3 Response of karst dissolution to drought in different areas
A striking result of the study is that the drought losses of karst dissolution of Site C were sharply lower than Site A and Site B except for cropland. However, in terms of the proportion of losses, the drought losses of Site C are not as small as seems (Table 2). Small karst dissolution loss in Site C may be directly related to the lower natural karst dissolution of Site C. It has long been assumed that the wetter and warmer the area is, the higher the karst dissolution should be. However, the karst dissolution in Site C with wetter and warmer conditions is less than that in Site A and Site B. More than that, the karst dissolution loss of cropland in Site A and Site B is the smallest, while that in Site C cropland becomes the most loss of land cover type.
According to the climate data recorded at Anlong station, which nearly by Site C (Table 5), during the experiment period, there is no severe drought occurred in Site C. Within experiment time, there was only a slight increase in precipitation, while the temperature increased by one ℃. Simultaneously, the largest continuous rainless days are 12 days, and even the largest continuous no effective precipitation days are only 21 days. In other words, during the study period, the climate of Site C has not changed abnormally. So, climate change should not be the main factor of the lower karst dissolution loss for Site C.
Besides, we analyzed the soil environment carefully, and we found that the soil pH value of Site C was lower than that of other regions in total (Tables 4). Furthermore, except for the slightly higher soil organic matter in Site C, there is not much difference in the three sites (Tables 4). According to our data, it is difficult to determine the reason for the lower karst dissolution of Site C. Of course, in other studies, there are also cases where the dissolution environment is pleasant, but the karst dissolution is not as high as expected (Yuan & Cai, 1988). These results suggest that the karst dissolution results from the combined effect of geology, soil, climate, and vegetation. Additionally, it may also relate to the specific experiment site and time.