The invasive forb Brassica nigra (black mustard) and the native tree Juglans californica (black walnut) are allelopathic species that suppress the growth of neighboring plants. This study evaluates how allocation to root, reproductive, and photosynthetic biomass in B. nigra was affected with proximity to J. californica. We hypothesized that a joint suppressive effect would lead to lower root biomass allocation in B. nigra near J. californica due to reduced interspecific competition. Our results indicate that B. nigra plants growing near J. californica had significantly lower root : total biomass ratios, and provide insights into how to effectively control this invasive species.
Key words: Allelopathy, competition, invasive species biology, principle of allocation, Santa Monica Mountains.
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