Opportunities for tree improvement : a paper prepared for the environment projection and monitoring course for Nyayo Tea Zone managers.

Abstract

Forest biodiversity refers to the wealth of life in a forest and has an intrinsic value globally and nationally. These values may be genetic, ecological, social, economic, cultural, recreational, aesthetic and educational in nature. Generally, biodiversity may be considered at three levels: the number of ecosystems with their interacting species and ecological processes; the number of species; and the genetic variability within a species. In Kenya, although closed canopy forests cover only 2% of Kenya's land area, they harbour a disproportionally large percentage of the nations biodiversity: 50% of woody plants, 40% of large mammals, 30% of birds and 35% of butterflies. These different life forms exist in a delicate, intricate and closely interwoven web. A decline in biodiversity and/or loss of a species results in a reduction of future stock and an imbalance of the closely interwoven web offorest life. It is therefore essential that forest biodiversity be conserved in its entirely from the ecosystem to the gene level. Such conservation would ensure that a representative sample of ecosystems and species are maintained, and that biodiversity and variation within a species is not diminished. The current rapid increase in population has resulted in an increase in demand for forest products and competition for forest land by other land uses especially agriculture and settlement. Because of this, there has been an alarming decrease in forest cover, environmental degradation and loss of biodiversity. One of the strategies that has been developed to combat deforestation is establishment of woodlots on farms and large scale plantations offast growing species. However, the success of such a programme depends largely on use of tree improvement techniques. The main objectives of a tree improvement programme is to maximise returns and improve quality of forest products. To fulfil this objective, both genetic improvement and silvicultural techniques have to be used. These techniques include the use of genetically improved seed; use of high quality planting stock (vigorous, healthy seedlings); and proper management of plantations (adequate site preparation, suitable planting techniques, and adequate tending). This paper summarises the genetic techniques used in tree improvement and highlights how genetic variation found in natural stands, plantations and woodlots may be used for the production of genetically improved seed