Levels of Alien Plant Invasion Depending on Past Severe Disturbances of Habitat: Pine Forests and Forest Plantations

The aim of this study is to assess the impact of past severe habitat disturbances in determining alien plant invasion level into forest communities. We hypothesized that forest plantations formed after severe disturbances should have an increased alien and invasive plant species richness and its proportions than natural forests. To test this hypothesis, we analyzed the materials of 367 vegetation relevés made in urbanized forest habitats within the boundaries of a large city (Yekaterinburg, Middle Urals, southern taiga) and suburban forests. Overall, 315 relevés are made in natural pine (Pinus sylvestris L.) forests and 52 relevés, in forest artificial coniferous plantations. Plantations were defined as communities formed as a result of severe past disturbances such as logging, fire, or agricultural use. It was found that forest plantations had, on average, 1–1.5 more alien plant species than natural pine forests (these differences were statistically significant). Similar differences inalien plants invasion level between forests and plantations were observed in both urbanized habitats and suburban areas. The richness of native species were differ between natural forests and plantations. Thus, we confirmed that severe past habitat disturbances facilitate the establishment of alien plants and increase observed invasion levels.