Abstract
Allelopathic substances were found in vegetative and reproductive structures of cypress (Cupressus lusitanica Mill.); aqueous extracts inhibited seed germination in three weed species: Lepidium costaricensis, Bidens pilosa and Rumex crispus. The amount of the inhibitor produced by cypress decreases significantly during the dry season. No soil persistance of the inhibitor was observed. The weed seeds begin to germinate normally after 8-10 days of treatment with aqueous extracts or after being washed with tap water. However, when seeds were treated with the essential cypress oils, no recovery of germination capacity was observed. The inhibitor did not show any effect on cypress seeds. This study suggests that cypress should not be used for reforestation in areas of steep slopes and heavy rainfall. In these sites the establishment of cypress forest could favor degradation instead of soil improvement.
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