Evaluation of cogon (Imperate cylindrica (L.) Beauv.) as a seral stage in Philippine vegetational succession. 1. The cogonal seral stage and plant succession. 2. Autecological studies on cogon

The extensive and persistent occurrence of I. cylindrica all over the Philippines has profound implications on range management and improvement, land conservation, watershed management and reforestation. Results of quantitative analyses of vegetation structure of plant communities representing different stages of plant succession at Siniloan, Quezon-Laguna, showed that a 5-year-old I. cylindrica community which developed from a shifting agriculture area assumed an Imperata/Solanum/Nephrolepis association if uncut for 2 years. An area of similar age and origin left undisturbed after logging assumed a Ficus/Macaranga/Solanum/Histiopteris association. Paspalum conjugatum was significantly and positively associated with I. cylindrica. Seeds of I. cylindrica show no dormancy but were sensitive to light quality and quantity, and germination was promoted by a pH of <5. I. cylindrica has a low top:root/rhizome ratio, thus providing a DM source for rapid top regrowth after cutting or burning. An allelopathic interaction with some other species may also aid its persistence. Tillering was positively correlated with net photosynthesis. Generally I. cylindrica has low light saturation (8000 ft c), a high CO2 compensation point, exhibits photorespiration and shows relatively low net photosynthesis.