NATURE OF SECONDARY SUCCESSION IN THE ABANDONED <em>EUCALYPTUS</em> PLANTATIONS OF NEYYAR (KERALA) IN PENINSULAR INDIA

Abstract

Vegetation structure and floristic composition of a 15- y - old secondary forest in an abandoned Eucalyptus tereticornis plantation of the Western Ghats (Peninsular India) was analyzed specifically addressing the following questions : (i) Does the stand show a lower floristic diversity than an adjacent mature forest? (ii) Does the young stand display vertical stratification and tree-girth distribution characteristic of uneven-aged forests under similar eco-climatic conditions? and, iii) Whether the pattern of abundance can be linked to the vital attributes of the species? Height and girth of all trees (≥15 cm girth at breast height (GBH)) in one hectare were recorded for phytosociological analyses. Density related diversity indexes were calculated and profiles of 80 x 10 m strip transects at two locations were made to describe stand physiognomy. Seven hundred and twenty-seven individuals belonging to 23 different species (≥15 cm GBH) were recorded from the sampling area. The average basal area for the stand was 12.77 m² ha^-1. Six species (E. tereticornis, Olea dioica, Aporusa lindleyana, Symplocos spicata, Terminalia paniculata and Macaranga peltata) had importance value indexes greater than or equal to 20. Few ruderal species were present at the site. Diversity index values were comparable with those
of a mature forest stand of the Western Ghats. Girth class frequency distribution showed an inverse 'J' shaped curve and the height-diameter relationships showed equitable distribution of trees on either side of a reference line : h = l00.d, suggesting the forest has adequate regeneration and the E. tereticornis overstorey has not influenced forest development. The current suite of species includes many with light weight, wind dispersed seeds and a mix of shade tolerant and intolerant species. The abundance of evergreen heliophytes with deciduous species suggests eventual development into a semi evergreen forest type. The present state of the
stand may be characterized as a "pre-equilibrium" stage in forest development.