Allelopathic interaction in forest ecosystems

Allelopathy, i.e. any direct or indirect, harmful or beneficial effect of one plant on another through the production of chemical compounds that escape in the environment, have been widely investigated in forest systems, especially when adverse impacts of understorey species on tree species are suspected. Dense ericaceous stands have been then suspected to inhibit germination and early growth of coniferous seedlings in numerous situations. Tree species (deciduous as well as coniferous) have also been identified as allelochemical producers. Plant secondary metabolites have also inhibitory properties towards soil microorganisms, and are suspected to influence N cycling by their effects on soil nitrifiers and immobilization of N under organic forms. Some applied aspects of this complex ecological process conclude this contribution. The search for causes of failure (or success) of natural regeneration often constituted a main axis of investigation on vegetation dynamics in forest ecosystems. In this context, to explanations implicating competition processes (for water, nutrients, light) or seeds and seedlings predation, succeeded complementary hypothesis on the effect of organic substances located in seedbed, reducing or inhibiting seedlings development (Fisher 1987): such biochemical interactions are named "allelopathy".