Joint Forest Management (JFM) is a form of participatory forest governance that aims for protection, conservation and sustainable use of forest resources by involving local communities. The JFM reforms have been promoted to address forest and land degradation, as vital in reducing institutional uncertainty in complex environments and strengthening cooperation among resource users. We draw on theories of collective action and transaction costs assuming that the overharvesting problem can be reduced by efficient and effective rules that support cooperation between forest users in using common pool resources at the group level and explore how forest users respond to policies that aim to reduce overharvesting in Tajikistan. To this end, we used a framed field experiment involving actual forest resource users. We find a strong impact of rules and the associated transaction costs in dealing with environmental and institutional uncertainties. The experiment results indicate that the harvesting rate is likely to decrease when institutionalized mechanisms are introduced to coordinate the interdependence among resource users. The overall results suggest that the rule determining harvest on a rotational basis is effective in reducing harvesting under environmental uncertainty regardless of the existence of communication and under institutional uncertainty when communication is permitted.