The difference between small, controlled lab experiments and ecosystem-scale experiments primarily relates to the applicability of the results.
In small, controlled lab experiments, conditions can be tightly regulated to isolate specific variables, which helps in understanding particular mechanisms or processes. However, the findings may not always be directly applicable to larger, more complex ecosystems where many factors interact. Ecosystem-scale experiments, on the other hand, take place in natural or semi-natural settings, allowing for the observation of interactions in a more realistic context, though they may involve more variables and less control over specific conditions.