A COMPILATION OF POTENTIAL ALTERNATE SHADE TREE SPECIES FOR TEA PLANTATIONS

Abstract

Tea (Camellia sinensis) is a shade loving plant, which is usually grown as amono crop, under a canopy of shade trees throughout its life. Variousphysiological functions of tea are facilitated by shade, leading to sustain itsvigour, yield and quality of the final produce. The 'tea - shade tree'ecosystem is manipulated to possess a microenvironment resembling forestcharacteristics. Of the four different tea growing agro-climatic regions in SriLanka, the recommended shade trees are confined to eight species: Grevillearobusta, Albizzia moluccana and Albizzia chinensis as high shade and Acaciapruinosa, Acacia decurrens, Erythrina lithosperma, Calliandra calothrysusand Gliricidia sepium as medium shade. One species each from the twocategories is usually grown at each location; pollarding and periodic loppingof high and medium shade respectively are practiced to ascertain the optimalshade levels of 10-40%. In order to achieve ecological, environmental andeconomic stability of the system and sustainable productivity per unit areaover monocultural systems, exploitation of more number of species is of vitalimportance. This also imparts direct benefits of harbouring natural enemiesof pests, moisture retention, nutrient and energy trapping, soil erosioncontrol, biomass energy and organic matter addition and indirect benefits ofC sequestration and opportunities for 'fair trade labeling' and eco tourism,biodiversity improvement, floral and aesthetic values and income generation.

The present exercise explored the alternative species considering climaticsuitability and natural habitat, growth rate, plant height, root characteristics,pollarding/ lopping ability, stem and branching characteristics, canopyarchitecture, leaf characteristics such as angle, size, shape, orientation andshedding. In addition, competitiveness with tea for water and nutrients,biomass production, nitrogen fixation, availability of information onpropagation and other silvicultural practices, harbouring pests and diseases oftea, food, timber, fuel wood values etc. were considered. Initial databaseresulted in over 230 potential species with native and introduced originsexcluding trees for intercropping and diversification purposes. The mostprobable species identified in the initial exercise were Adenenthera pavonina,Adina cordifolia, Albizzia odorissima, Alstonia macrophylla, Alstoniascholaris, Bauhinia racemosa, Bauhinia variegata, Berrya cordifolia, Bhesa zeylanica, Cananga odo rata , Canthium montanum, Carallia brachiata,Cassia javanica, Cassia spectabilis, Cedrella odorata, Chukrasia tabularis,Dalbergia sissoo, Elaecarpus amoenus, Elaeocarpus glandulifer,Enterolobium cylocarpum, Erythrina edulis, Erythrina fusca, Erythrinapoeppigiana, Erythrina variegata, Filicium decipiens, Khaya senegalensis,Macademia temifolia, Mallotus tetraeocevs, Mangifera zeylanica, Micheliachampaca, Muntingia calabura, Parkinsonia aculeata, Paulownia fortunei,Peltophorum dasyrachis, Pentaclethra macroloba, Pongamia pinnata,Pterocarpus indicus, Sapindus emarginatus, Tecoma stans, Temstroemiagymnanthera and Trema orientalis, which belong to the families Anonaceae,Apocynaceae, Bignonaceae, Elaeocarpaceae, Euphorbiaceae, Fabaceae,Magnoliaceae, Meliaceae, Paulowinaceae, Proteaceae, Rhizophoraceae,Rubiaceae, Sapindacea, Theaceae, Tiliaceae and Ulmaceae.

The species will be exposed to further screening processes and pilot scalefield evaluations at the Tea Research Institute and different tea growing areasrespectively, prior to releasing the most promising selections for field use.