User:Raf Aerts/Notebook/Open Coffee/2008/09/01
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Field notes on Geruke coffee
A wide variety of coffee production systems exists in Ethiopia. One can differentiate pure wild forest coffee and pure plantation coffee, and many intermediate forms based on the level of intervention by man. Senbeta and Denich (2006) distinguish the relatively undisturbed forest coffee (FC), where little or no human inference is observed, and the disturbed semi-forest coffee (SFC) system.
From a forest perspective, the most important types of intervention in the SFC are canopy management and slashing. Canopy management consists of removing unwanted overstorey species and crown thinning of retained shade trees. Obviously this leads to a simplification of the (vertical) forest structure and to a loss of species diversity (e.g. tree species, climbers and epiphytes). Slashing is carried out to reduce competition in the shrub layer, which is, essentially, coffee. Saplings of overstorey species are also removed during this operation, hereby reducing the potential for succession of the shade trees.
From a coffee genetic diversity perspective, planting is the most important intervention. In the Geruke fragments, almost all coffee shrubs were planted at some point in time, and semi-plantation coffee (SPC) may be a more appropriate name for this system. Naturally established seedlings are rare, if not restricted to the FC systems in the larger forests such as Gera NFPA. Nevertheless, Wild coffee does persist in Geruke, because farmers have used and continue to use coffee wildlings to restock their coffee plantations. These local land races, called begega in Oromo (begedzja), are preferred over introduced races because their coffee beans have a better taste and because the shrubs need less management. But introduced races with unknown origin, called g’brna (Amharic: (from the) government) or locally, qona (Oromo), are more productive, and are specifically selected for their resistance to Coffee Berry Disease (CBD), an anthracnose of coffee fruits caused by the wind- and water-dispersed fungus Colletotrichum coffeanum. Because the distribution of CBD-resistant varieties and other non-local races is a fairly recent practice, old plants with large diameters (with a diameter at breast or coppice height well over 10 cm) are more than likely local land races, established before the installation of the military regime in Ethiopia (1974). In Debye, at the southern edge of Belete NFPA, old coffee shrubs in a plantation established ~35 years ago may therefore still carry the genetic signature of wild Belete coffee. In Qacho, in Gera NFPA, a variety of FC and SFC systems still harbour true wild coffee, with a particularly large wild coffee population in Qacho-Andaracha.
Distribution of seedlings is common practice nowadays. In some rare cases, qona coffee was raised from local seeds, but in most cases, qona is one of the ~21 released CBD-resistant varieties. Resistant varieties are selected from a large coffee collection of the Melko Agricultural Research Centre near Gera NFPA, where CBD-pressure is high. Resistant varieties are propagated by use of tissue culture, because vegetative propagation by cuttings involves too much work (among others, the production of orthotropic shoots on stock plants). The next variety to be introduced is most likely going to be Aba buna, a single F59-74.1 clone created in 1993. It has not yet been released because the F2 generation does not maintain high productivity. Most recently, the Research Centre started focusing on newly emerging diseases such as Tracheomycosis or Coffee Wilt Disease.
For begega, wildings are collected from nearby or distant forest fragments, or from mother trees already transplanted from the wild, usually in private homegardens. In particular seedlings from local mother trees may not qualify (any more) as true wild coffee because of the potential effects of inbreeding and genetic drift (effects of small population sizes) or outbreeding and introgression (effects of introduced varieties). Farmers do not use vegetative propagation for coffee (as opposed to qat).
The coffee forests of Geruke are SFC and SPC with often both begega and qona coffee within the same fragment. Albizia gummifera, Milletia ferruginea and Acacia spp. are among the common permanent shade trees, which are preferentially leguminous, wide branched and deep rooted. Farmers also tend to keep Cordia africana for the timber and sometimes introduce Sesbania sesban as a temporary shade. The forest edges are often lined with small trees such as Brucea antidysenterica or live fences established from Erythrina abyssinica stakes. Overstorey species as well as invasive species such as Calpurnia aurea and Pterolobium stellatum regenerate in the understorey but these seedlings are regularly cleared. Coffee seedlings are transplanted prior to slashing. Rare overstorey species include Prunus africana, Afrocarpus falcatus and Pouteria adolfi-friederici which are mainly appreciated for their timber.