We evaluated effects of larch plantations on understory plant diversity by conducting large-area investigations on three types of tree stands, including pure larch plantations (Larix kaempferi, an exotic coniferous deciduous tree species), pure liriodendron plantations (Liriodendron chinense, a native broad-leaved deciduous tree species) and mixed stands (L. kaempferi and L. chinense) in a subtropical forest. A total of 19 plantation areas, 684 quardrats, and 10 environmental factors

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... slope, ratio of light availability (RLA), soil pH, soil water content (SWC), soil organic matter (SOM), soil total nitrogen (STN), soil total phosphorus (STP), soil total potassium (STK)] were surveyed. Species richness and Shannon's diversity were statistically similar in the three types of tree stands but Shannon's diversity was somewhat higher in mixed plantations. Environmental conditions were similar in the three types of tree stands (P﹥0.05). Species richness and Shannon's diversity increased with increasing elevation and understory light availability (P<0.05). Canonical Correspondence Analysis (CCA) showed that distribution of shrubs was determined by elevation, while herb distribution was related primarily to soil fertility followed by elevation. Based on the unchanged environmental conditions after establishment of larch plantations, we conclude that larch plantations had balancing effect on understory plant diversity.