Terra firme

Leopoldo, R, W. Franken, E. Matsui, and M. Roibeiro. 1982. "Estimativa da evapotranspirafao da floresta Amazonica de terra firme." Acta Amazonica 12 23-28. 

Forti, M. C., and L. M. Moreira-Nordemann. 1991. Rainwater and throughfall chemistry in a Terra Firme rain forest Central Amazonia, Journal of Geophysical Research 96 7415-7421. 

Soil versus Biological Controls on Nutrient Cycling in Terra Firme Forests... 

Terra firme forests growing on Oxisols/ Ultisols seem to be primarily limited by phosphorus (Vitousek 1984, Vitousek and Sanford 1986, Cuevas and Medina 1986, Cuevas and Medina 1988), while at the same time being tolerant of high soil concentrations of mobile aluminum (Sprick 1979, Sobrado and Medina 1980). Cuevas and Medina (1988) showed that terra firme forests can also be limited by calcium and magnesium, which corroborated the hypothesis of Furch and Klinge (1989) who measured low Ca and Mg contents in biotic and abiotic compartments in terra firme forests of Amazonia. Plant adaptation to these conditions requires highly efficient uptake and/or utilization of nutrients, especially phosphorus, calcium and magnesium (Marschner 1995). 

Table 4.2 Belowground and aboveground biomass, percent contribution of belowground and root/shoot ratios in terra firme forests.

Measurement of litterfall and its associated fluxes of nutrients is a practical way to evaluate production capacity and availability of nutrients in tropical forests. Mass and nutrient fluxes of litterfall in terra firme forests can vary considerably according to specific loca-... 

Fig. 4.1 Organic matter stocks in soil and litter layer under a terra firme forest in San Carlos de Rio Negro, Venezuela (data from Tiessen et al. 1994a).

Table 4.4 Mass and nutrient fluxes in leaf litter from terra firme forests growing on Ultisols/Oxisols.

Fig. 4.2 Distribution of dry mass/P ratios and P/N ratios from terra firme forests growing on Ultisols/Oxisols (references in Table 4.4). MFS=Medium Fertility Soil...

Production of roots on top of the mineral soil has been explained as a consequence of the low nutrient availability in Amazon forests (Herrera et al. 1978, Cuevas and Medina 1983, Medina and Cuevas 1989). Vertical root distribution results from differential nutrient availability in the soil profile (Berish 1982, Berish and Ewel 1988). Shallow rooted systems may be a result of litter and soil organic matter production and decomposition rates in systems where nutrient input from litter exceeds that of nutrient release by soil weathering, as is the case of Ca, Mg, and P in terra firme forests (Medina and Cuevas 1989). In the Middle Caqueta region of Colombia, for example, Ca and Mg concentrations in the L and F layers are between 15 and 20 times higher than in the mineral soil (Duivenvoorden and Lips 1995). 

Soils under terra firme forests can vary in the amount and availability of Ca and Mg as previously indicated. Cuevas and Medina... 

Table 4.6 Total mass s.d. (live + dead) of fine roots (< 5 ram diameter) in ectorganic horizons and mineral soils at 0-40 cm depth in terra firme forests.

Salcedo et al. (1991), working in an Atlantic coastal forest in Recife, Brazil, showed that phosphoms from the litter/fermentation layer is cycled back to the vegetation via mycor-rhizae-mediated mechanisms. However, 6l% of the added moved down to the mineral soil, where P in the soil solution is controlled by microbial biomass activity. In contrast. Stark and Jordan (1978), working on a P deficient upland terra firme forest in San Carlos de Rio Negro, Venezuela (Cuevas and Medina 1988), found that nearly 100% of the added 32p was retained in the root mat associated with the litter layer, with less than 0.1% moving down to the surface of the mineral soil. 

Amazon terra firme forests are lower than those measured on richer soUs in Costa Rica and Barro Colorado, Panama. In general all the organic N mineralized is subsequently nitrified, leaving little or no free NH4. Under natural conditions, however, NH4 could be incorporated into biomass, immobilized in the soil, or taken up by the vegetation, resulting in a reduction of nitrification rates. 

Cuevas, E., and E. Medina. 1983. Rootproduction and organic matter decomposition in a terra firme forest of the upper Rio negro basin. In International Symp. Root Ecol. and its Practical Applications, ed. L. Kutschera (Gumpenstein, Austria), pp. 653-666. 

Franken, M., U. Irmler, and H. Klinge. 1979. Litterfail in inundation, riverine, and terra firme forests of Central Amazonia. Tropical Ecology 20 225-235. 

Franken, W. 1979. Untersuchungen im Einzugsgebiet des zentralamazonischen Urwaldbaches Barto Branco auf der terra firme, 1. Abflussverhalten des Baches. Amazoniana IV 459-466. 

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