Impact of Native Black Locust and Invasive Tree of Heaven on Tree Regeneration and Diversity

Many invasive plant species colonize disturbed sites and interact with early successional native species. The outcomes of these interactions (i.e., competition and/or benefit) among native and nonnative species may affect the future growth of trees and other plants in the invaded communities, potentially leading to different species compositions and ecological conditions that may represent new stable states.

The native black locust (Robinia pseudoacacia) is an early-successional, nitrogen fixing tree while tree of heaven (Ailanthus altissima) is an invasive tree that may inhibit the growth of other trees around it. Scientists studied how having both species in a forest ecosystem affected the regeneration, basal area, and diversity of the forest at local and regional scales.

Key Findings

• Native black locust (R. pseudoacacia) and invasive tree of heaven (A. altissima) are more likely to be found growing next to each other than separately (i.e., they are positively associated) and affect each other’s regeneration.
• The relationship between black locust and tree of heaven endures across later stages in forest succession.
• Tree of heaven inhibits native tree regeneration and diversity at both local and regional scales.

The study assessed the influences of black locust and tree of heaven on tree regeneration and diversity across both local and regional scales.  At the local scale, all woody stems were meticulously mapped in two mid-successional sites located in Virginia. Data from the USDA Forest Inventory and Analysis program was used for the regional analysis which covered the entire native range of black locust.

Study findings indicated a positive association between the native black locust and the invasive tree of heaven. This association persisted through mid- and late-successional stages in forest succession. In addition, tree of heaven consistently exhibited an inhibitory effect on native tree regeneration and diversity at both local and regional scales.