Document: MAR-3-67-22
Edaphic factors in succession: Interactions between Bidens polylepis and Oenothera biennis.
MCKENNA, M.A.*, J.ABRAHAM and T.COLLINS
Howard University, Washington, D.C. 20059 USA 1
Abstract:
Tickseed sunflower (Bidens polylepis) Blake, Asteraceae, is an annual that frequently colonizes disturbed sites in northern Virginia, where it forms dense, persistent populations. We have been investigating the factors that promote persistence in this annual. Other members of this genus are known to produce compounds that inhibit growth of agricultural species. In previous studies we examined interactions between B. polylepis and evening primrose (Oenothera biennis) L., Onagraceae, a common biennial. We established that O. biennis seedling growth is inhibited when grown in commercial soil mix with B. polylepis. Growth of O. biennis is also inhibited in soil collected from B. polylepsis populations. Since inhibition in natural soil could result from many biotic and abiotic factors, this study examined O. biennis seedling growth in commercial soil mix "conditioned" by previous growth of B. polylepsis. O. biennis seeds were planted at two density levels in three soil treatments: 1) Control soil (Promix + fertilizer); 2) Short duration "conditioned" Promix + fertilizer; and 3) Long duration "conditioned" Promix + fertilizer. Seedlings were grown under controlled temperature and light conditions for eight weeks. Dry shoot weight was compared by ANOVA. Plants at low density were significantly heavier than high density treatments. Plants in control soil were significantly heavier than "conditioned" soil treatments. Plants in short duration conditioned soil were significantly heavier than long duration conditioned soil. These results suggest that B. polylepis may inhibit growth and establishment of O.biennis through physical or biochemical modification of the edaphic environment. These edaphic factors may influence the process of succession in microhabitats.
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This abstract is being presented at: 3:30 PM in session:
Poster Session #17: Vegetative Analysis.