The Pontycymer Nursery youngsters were part of a test project in Bridgend.
The children were encouraged to play together and with materials such as buckets and trowels and were discreetly observed by staff.
The trial was led by the Forestry Commission Wales.
A group of nine children spent about three hours every week for a 10-week period at the Rockwood Woodlands for Learning (WfL) centre in Pencoed, Bridgend county.
At their first Play Project session, the children were taught how to carry out a simple risk assessment of the woodland and given basic resources such as buckets, ropes, trowels, mud and water to encourage them to start playing.
The resources were reduced each week until the children just used what they could find in the woods to interact with and use in their games.
The adults with them, play leaders from Woodlands for Learning and the nursery staff, observed the children discreetly and recorded how involved the children were in their play.
Part of the philosophy behind the project is modelled on outdoor learning in Sweden, which aims to encourage independent learning.
WfL education manager Karen Clarke said each child was assessed three times during the session for two minutes each time to analyse how they were interacting with their environment.
She said of the mediation skills the children started showing: "The conflict resolution came along during the project. Withdrawing adult-led interaction, it was a byproduct of the process.
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