Other species - species description

In addition to the commercial species described above also pueraria and some species of the spontaneous vegetation (together referred to as "non-commercial" species) were analyzed chemically.

Pueraria (Pueraria phaseoloides (Roxb.) Benth.) (Fig. 1) (tropical kudzu (international), puero (Australia.)) is a legume which already occurred throughout many parts of the experimental area since it was sown as cover crop also at the former rubber-experiment. Before planting the present experiment H. Preisinger found pueraria in about 69% of the plots of SHIFT (Preisinger et al. 1994). Pueraria is a "twining and climbing, slightly woody, hairy perennial legume, deep rooting and rather slender" (Skerman 1988). Main stalks are reported to be up to 0.6 cm in diameter - those in our experiment were found to be up to about 1 cm.

Pueraria is native in Asia, Malaysia, and Indonesia, but is now widespread throughout the tropics. It grows optimally under hot and wet tropical conditions. Soil can be acid, sandy to clayey, not too heavy; the species can stand short periods of flooding. Pueraria is highly competitive; it smoothes out weeds and even invading trees (Szott et al. 1991). Data about the amount of N₂ fixed vary considerably, which is understandable since growth and fixation rate vary largely, too. About 150 kg/ha and year is a typical value (Giller & Wilson 1991, referring to different authors and Skerman 1988). Pueraria responds well to fertilization, in soils very poor in Ca, P, K or Mg it performs badly; too much available N reduces N₂-fixation. The species is "remarkably free of diseases" (Skerman 1988).

Mandioca (Manihot esculenta Crantz, Euphorbiaceae) (Fig. 1),(cassava, manioc (Engl.), Maniok, Kassava, Kassave (German), mandioca, yuca (Spanish), manioc (French)) is the highest yielding of all tuber crops even under poor soil conditions (Rehm & Espig 1984). It is naturally inhabited from Amazônia to Mexico but now cultivated worldwide throughout the tropics. World average yield is given as about 9 t/ha, but a maximum of 60 to 80 t/ha is possible in commercial plantings (Rehm & Espig 1984). Mandioca protects its tubers with the substance linamarin which releases the toxic HCN when damaged. The tubers are rasped and watered several times to wash out the substance prior to further use. Tapioca, the starch of mandioca, is an important product on the worlds agrar-market. Besides the linamarin-rich "bitter" varieties, varieties with low toxicity, known as "sweet" cassava are grown; these can be eaten directly after having been boiled. The leaves of the plant are often used as vegetable. Mandioca is a generalist regarding its demand to climate and soil.

Mandioca was planted between the rows of the AF-System plots in 1993 only.

Clidemia hirta (Melastomataceae) occurred in about 69% of the plots of SHIFT by 1993 (Preisinger et al. 1994). Clidemia h. is a dicot plant of the spontaneous vegetation within the plots. In the plots it is about half a meter to a meter high.

Vismia guianensis (Clusiaceae), was found in about 44% of the plots of SHIFT (Preisinger et al. 1994). Vismia g. is a shrub or small tree of the secondary vegetation. As Schmidt (1996) states the species obviously needs full sun, as it was not found in shade. From its spontaneous appearance and fast growth, it can be concluded, that the Vismia g. is well adapted to the poor, acid terra firme soils. The species probably could become important in medicine; investigations on an effect on cancer are being carried out. The orange resin is used by local population for disinfecting superficial wounds.

Cecropia spp. (Urticaceae) (Fig. 1) occurred in about 54% of the plots of SHIFT (Preisinger et al. 1994). In this study samples of Cecropia uleia and Cecropia concolor were analyzed. The perennial species of Cecropia are typical for disturbed open habitats as abandoned fields and between streets and surrounding forest as well as in the varzea along rivers. It grows to heights of more than 20m. Economic use is unknown; the stem has a high water content and shows separated hollow internodes. Many species live in symbiosis with tree-defending ants providing protection in the internodes and offering foodboddies at the base of the petiole (Bell 1991). As the Vismia species also the two species of Cecropia analyzed here seem to be well adapted to the unfavorable soil conditions encountered in the unfertilized plots of the SHIFT-Experiment.