Environment-tree growth relationships of plantation grown tropical tree species as a basis for sustainable timber production in mixed culture systems in Central Amazonia.

This comparative study on environment-tree growth relationships of the high quality native tree species Swietenia macrophylla King (mogno) and Carapa guianensis Aubl. (andiroba) is part of the development of sustainable landuse systems on "terra firme" sites of the Central Amazon within the Brazilian-German research cooperation SHIFT. As to get information on the site demands and the growth characteristics of plantation systems of mogno and andiroba: (1) monoculture system, and (2) an enrichment system (both stablished in 1992 at the experimental site of the Embrapa Amazonia Ocidental, Manaus-AM). The water balance of the plantations was quantified by evaporation and transpiration/xylem flux measurements as well as the calculation of the water run-through in the soil (Cl-method). The K supply of the trees was investigated by quantified input (precipitation, throughfall, stemflow, litterfall) and output (K uptake of the vegetation, leaching out of the soil). The cambial growth dynamics of the trees was dated in one-month-intervals by the pinning method - period April 1995 until December 1996). A reduced soil water content with a suction force in the upper soil layer (depth 20cm) of 500 hPa to 900 hPa was found from August until November in both plantation systems. High evaporation and water run-through caused short periods with low soil water contents (300 hPa to 400 hPa) even during the wet season in monoculture systems. A cambial dormancy or a reduced rate of cambial cell divisions of mogno was found during the drier season from August to December whereas the cambial growth dynamics of andiroba was not correlated with the annual course of the soil water content. K cycling was improved in the enrichment system compared to the monoculture system, whereas the K supply of the soil was reduced. The reduced xylem production of mogno in the enrichment system compared to the monoculture system was correlated with the low K content of the soil in this system. From these results i was concluded that andiroba is more competitive for sustainable growth on this site than mogno.