Nature of secondary succession in the abandoned Eucalyptus plantations of Neyyar (Kerala) in Peninsular India

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 thepattern of abundance can be linked to the vital attributes of the species? Height andgirth 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 belongingto 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, Oleadioica, Aporusa lindleyana, Symplocos spicata, Terminalia paniculata and Macaranga peltata) had importance value indexes greater than or equal to 20. Few ruderalspecies were present at the site. Diversity index values were comparable with thoseof a mature forest stand of the Western Ghats. Girth class frequency distributionshowed an inverse 'J' shaped curve and the height-diameter relationships showedequitable distribution of trees on either side of a reference line : h = l00.d,suggesting the forest has adequate regeneration and the E. tereticornis overstorey hasnot influenced forest development. The current suite of species includes many withlight weight, wind dispersed seeds and a mix of shade tolerant and intolerantspecies. The abundance of evergreen heliophytes with deciduous species suggestseventual development into a semi evergreen forest type. The present state of thestand may be characterized as a "pre-equilibrium" stage in forest development.