'Without bamboo, the land dies': biomass, litterfall, and soil organic matter dynamics of a Javanese bamboo talun-kebun system.
Christanty L., Mailly D., Kimmins J. P.
Author Affiliation: D. Mailly, Faculty of Forestry, Department of Forest Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
Forest Ecology and Management 87 : 75-88
Abstract : Talun-kebun is an upland land use system in which annual food or cash crops (kebun) are alternated sequentially with tree crops (talun). Its overall pattern is similar to that of shifting cultivation, but the length of the fallow period is much shorter and there is a deliberate selection of species used at each stage. It has been used in montane W. Java, Indonesia, for at least six generations, and currently is practised on ~16% of arable land on Java. This study evaluated biomass, litterfall, and soil organic matter dynamics during a complete 6-yr bamboo talun-kebun rotation cycle in Sukajadi village, Soreang district. This cycle consisted of 1 year of mixed species vegetable cropping (kebun) after the removal of bamboo, followed by 1 year of cassava, and 4 years of bamboo fallow (talun): a total cycle length of 6 years. Common bamboo species are Gigantochloa ater [G. atter] and G. verticillata; others frequently found are G. apus and Bambusa vulgaris. Trees are usually found scattered between the bamboo clumps, such as Albizia falcataria [Paraserianthes falcataria], Parkia speciosa, Arenga pinnata (sugar palm), and fruit trees such as Mangifera indica (mango) and durian (Durio zibethinus). In general, fruit and pod biomass constituted the highest percentage (38-68%) of the total crop biomass of 8.4 t/ha which accumulated during the first year of cropping (Dolichos lablab [Lablab purpureus], cucumber and Solanum nigrum). Cassava (Manihot esculenta) yielded a total of 4.6 t/ha of roots and tubers during the second year cropping from a total biomass accumulation of 6.7 t/ha. An experimental second year of cassava cropping without any fertilizers caused a decline in the yield of roots and tubers to 60% less than the comparable value for the first year of cassava. Weeds, which reached a maximum biomass value of 1.8 t/ha at the end of the first year cropping, were all but eliminated from the later stages of the bamboo talun. The total biomass of bamboo increased with increasing age and reached 76.6 t/ha after 6 years. The distribution of total bamboo biomass between above- and below-ground components also varied with age. At 16 months after bamboo harvest, above-ground biomass accounted for 6% of the bamboo total mass. By the end of the 4-year bamboo fallow, 6 years after the bamboo harvest, 59% of the bamboo biomass was above-ground. In the final year of the bamboo talun stage, total above-ground litterfall was estimated at 4.7 t/ha, while the forest floor mass was 13.5 t/ha. There was an increase of ~7 t/ha of soil organic matter in the surface 25 cm of soil during the 4-year fallow. The historical, sustained success of the system with minimal external inputs of fertilizer appears to be closely related to the growth habit and biogeochemical characteristics of the bamboo - rapid biomass accumulation, the accumulation of its litter, and the extremely high biomass of fine roots. This study provides scientific support for the traditional saying of the local farmers, 'without bamboo, the land dies'.