E3 Journal of Environmental Research and Management

E3 Journal of Environmental Research and Management Vol. 4 (7) pp. 0293-0298, August 2013; © E3 Journals; ISSN 2141-7466

The effects of intra-specific competition on survival in a Casuarina Equisetifolia spacing trial in Gede, Malindi, Kenya

Abstract

Competition for resources (light, water and nutrients) is one of the major causes of poor growth, suppression and delayed harvests in woodlots. In severe cases it may lead to death altogether. While many authors have reported on the possible mechanisms and effects of inter-specific competition (between different species), few studies in Kenya have looked at competition effects between similar species (intra-specific competition) and how this phenomenon affects tree survival. Intra-specific competition can be made worse by planting trees very close together; a very common practice among many farmers who grow Casuarina at the Coast. Casuarina equisetifolia is one of the most important agroforestry/farm-forestry tree species along the Kenyan Coast. In a spacing trial of C. equisetifolia established in 2003, trees grown at 1-by-1m spacing showed poor growth (data not shown), with more deaths (78 %) after a prolonged drought spell in 2005. Meanwhile, trees in the same area grown at 2.5-by-2.5m spacing had higher survival. It can be elucidated that the increased deaths resulted from increased intra-specific competition. Farmers are therefore, advised not to use very close spacing to avoid loss of growth and avoidable tree death from severe intra-specific competition, especially in dry sites and/or during prolonged droughts.

Keywords: Casuarina equisetifolia, Intra-specific competition, spacing, drought, mortality