Abstract: With the reform of forest rights system in Sichuan Province, the management mode of forest plantations in expressway area has become diversified. We investigated the effects of different forest managements (UP: understory planting; PT: plow tillage; MO: mowing; AC: abandoned cultivation; CK: control, no management activity) on poplar plantations along expressway areas around Chengdu, aiming at providing theoretical reference for scientific forest management. The field survey was conducted in midJuly 2020, using typical plot sampling method. We measured each tree in the sampling plots, recorded understory species composition, calculated α diversity, and measured several soil characteristics, including soil water content, soil bulk density, total potassium, available potassium, total nitrogen, total phosphorus, available phosphorus, organic matter, soil pH. The treatments of UP, MO and AC significantly reduced species diversity of shrub layer, while PT increased species diversity of herb layer. There was no difference in soil bulk density, total potassium, and total phosphorus across different forest management modes. UP, PT, MO, and AC significantly reduced the concentrations of available phosphorus, total nitrogen and available potassium. UP and MO evidently increased soil pH. UP, PT, and AC decreased soil water content, while MO reduced organic matter content. Moreover, available phosphorus, soil water content, soil pH, total nitrogen and available potassium significantly affected species diversity of herb layer, while available phosphorus, available potassium and total nitrogen affected species diversity of shrub layer. Our results demonstrate that ecological effects differed among forest management modes of poplar plantations. Except CK, all forest management modes significantly reduced the contents of soil available phosphorus, total nitrogen, and available potassium. The change of understory species diversity in poplar plantations could be explained by the change of soil available phosphorus, total nitrogen, and available potassium.

Key words: road-region forest, forest management, species diversity, soil physicochemical property, redundancy analysis.