Pot experiments with woody species – a review

Pot experiments, as a complement to field measurements, allow the investigation of plants under controlled conditions without distracting effects of heterogeneous environmental factors. Due to the longevity and larger dimensions of tree species, pot experiments with trees raise more problems than studies with herbaceous plants. We analysed 93 studies on pot experiments with woody forest species and provide an overview of their practical implementation. The literature review revealed that various factors should be taken into account in providing good growing conditions for pot experiments, including pot size, substrate, plant age and origin, and transplanting effects. Many studies did not follow existing recommendations, e.g. an appropriate pot size. Therefore, the transferability of the experimental results to natural conditions is limited and could be improved. We propose that investigation of tree response in pot experiments should be combined with additional measurements under natural conditions. Unfortunately, many papers using pot experiments did not provide complete information on the experimental set-up, making an evaluation on the quality of pot experiments difficult. We conclude that authors should provide more detailed information on the methodology that can be used to repeat or design future pot experiments.