2.3 Field experiment design
Separating the drought loss of karst dissolution from a normal state is crucial for quantifying the impact of different intensity droughts on karst dissolution. Therefore, the present study concurrently set up two groups of experiments in forest, cropland, shrubland, and grassland of Site A, Site B, and Site C, respectively. In two groups of experiments, one group has no drought treatment, representing the regular karst dissolution. Correspondingly, the other one has drought control treatments, which simulates the karst dissolution affected by droughts. Consequently, the quantity difference between the two groups of experiments can be regarded as the drought loss of karst dissolution.
Transparent rain shelters were established within each experiment plot as the drought treatment during the field experiment. Each treatment was crossing five intensity of droughts (light, moderate, severe, extreme, and rare). Rain shelters are considered ventilation, sunlight, air temperature, rain shelter effectiveness, and so on. To prevent the impact of severe natural drought on karst dissolution, we have prepared an integral emergency response plan based on the multi-year average climate of experimental areas. To the end, of course, none of these measures be used.
The drought intensity levels were determined by the comprehensive consideration of the occurrence of droughts, and the karst dissolution itself in Southwest China. After carefully trade-off, the study used no precipitation in 30 consecutive days as light drought, no precipitation in 60 consecutive days, 90 consecutive days, 120 consecutive days, and 365 consecutive days as moderate, severe, extreme, and rare, respectively. Accordingly, the dissolution amounts of obtained after buried 30 consecutive days, 60 consecutive days, 90 consecutive days, 120 consecutive days, and 365 consecutive days in drought control treatments be equivalent to the karst dissolution of affected by light, moderate, severe, extreme, and rare drought, respectively. Correspondingly, the dissolution amounts of obtained after experiment 30 consecutive days, 60 consecutive days, 90 consecutive days, 120 consecutive days, and 365 consecutive days in matched groups can be regarded as the karst dissolution amounts without the effect of light, moderate, severe, extreme, and rare drought, respectively. The quantity difference between the parallel groups in each experiment plot is the karst dissolution loss caused by drought.