Objective Laboratory drought simulation and in-situ drought manipulation are two common methods for studying soil ecological processes in response to climate drought. However, the results often differ significantly because laboratory settings simplify environmental factors, whereas in-situ conditions are subject to complex disturbances.

Method The study compared the soil nitrogen mineralization and its driving factors under three drought gradients (ambient, 30% reduction in throughfall, and 50% reduction in throughfall) using laboratory (incubation bottles and PVC tubes) and in-situ (PVC tubes) culture conditions. The study was conducted in a poplar (Populus deltoides) plantation at Dongtai Forest Farm, Jiangsu Province.

Result The results suggested that laboratory incubation experiments exhibited significant differences compared to in-situ simulations experiments when assessing soil pH, inorganic nitrogen, and net ammonification rate. However, the results for the drought effects on microbial biomass and net nitrification rate were consistent between the two conditions. PLS-SEM analysis showed that laboratory incubation experiments could not fully reflect the complex ecological correlations of soil nitrogen mineralization in an in-situ environment, potentially leading to an underestimation or misjudgment of drought's effect on biogeochemical interactions. However, laboratory experiments remained valuable for analyzing the correlation between soil water content and microbes under reduced environmental disturbance. Furthermore, the altered soil physical structure in incubation bottles could underestimate the effect of drought on nitrogen mineralization.

Conclusion In conclusion, the study emphasizes that while laboratory experiments are valuable, they cannot fully replace in-situ experiments. Future research should build upon in-situ findings and integrate results from more judiciously designed laboratory cultures to achieve more accurate understandings of the mechanisms by drought impacts on soil ecological processes.