Abstract

Interactions between tree seedlings and herbaceaous vegetation are widely assumed to be important factors affecting the growth and performance of seedlings. However, few experimental studies have been conducted to investigate the importance of such phenomena. This study was carried out to determine if the herbaceous ground flora in deforested areas can be used to indicate the suitability of sites for the natural establishment or planting of various tree seedling species. It examined recruitment (density, relative growth rate, mortality), species composition, diversity and richness of the natural tree seedling community and their association with the herbaceous ground flora vegetation communities on deforested sites. Three major types of dominant ground flora communities were selected for the quantitative investigation (Eupatorium adenophorum Spreng. (Compositae); Imperata cylindrica (L.) P. Beauv. var. major (Nees) C.E. Hubb. ex Hubb. & Vaugh. (Gramineae); Pteridium aquilinum (L.) Kuhn ssp. aquilinum var. wightianum (Ag.) Try. (Dennstaedtiaceae) and two additional sites were selected for qualitative study i.e. Imperata cylindrica dominated site, and mixed ground flora species (Pennisetum pedicellatum Schumach.; Setaria parviflora (Poir.) Kerg., Microstegium vaganas (Nees ex Steud.) A. camus (all Graminae), and Eupatorium adenophorum dominated site. A total of 48 quadrats of 2 x 2m were laid down in 50 x 50m permanent plots. The quadrats were inspected every 2 months over 10 months.

Tree seedling diversity (N1) was highest in the Eupatorium-dominated site (10.23) followed by the Imperata-dominated site (7.52) and the Pteridium-dominated site (5.59). Moreover, the Eupatorium site had the lowest seedling mortality (21.7% over 10 months) followed by the Pteridium site (25.7%) and the Imperata site (30%). For most tree seedlings species, growth rates were highest in the Eupatorium site and lowest in the Pteridium site. There were no significant associations between any of the tree seedling species found in the Imperata and Pteridium-dominated sites with the dominant herbaceous ground flora species and in the Eupatorium-dominated site, only three tree seedling species [Castanopsis diversifolia King ex Hk. f. (Fagaceae), Leea indica (Burm. f.) Merr. (Leeaceae) and Phoebe lanceolata (Nees) Nees (Lauraceae)] showed significant association. There were no significant differences among sites in soil parameters. Out of the four vegetation types, Eupatorium adenophorum seems to provide the best conditions for tree seedling establishment and growth and provides a reliable indicator for success of C. diversifolia, L. indica and P. lanceolata seedlings. In general, however, dominant ground flora did not provide a reliable indication of the tree seedling community or the soil conditions, since few positive associations were found and the soil conditions were very similar at all three sites.