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.