BOLETIM DA FACULDADE DE CIÊNCIAS AGRÁRIAS DO PARÁ, n. 26, jul/dez. 1996

Abstract

1) This paper presents a grouping proposal for terra-firme equatorial tree species, near Manaus(Brazil), to facilitate the silvicultural decisions. The criterion for tree grouping was a combination ofdiameter distribution shape and amplitude with natural regeneration amount, obtained in survey on undisturbed forest. It resulted in three ecofisiological groups: shade tolerants species; intermediary species; and shade intolerant species. Shade tolerant and intermediary species were predominant (more than 90% of tree species DBH=25cm), indicating that the forest is in mature phase.

2) This paper presents a grouping proposal for terra-firme equatorial tree species, near Manaus(Brazil), to facilitate the silvicultural decisions. The criterion for tree grouping was a combination of diameter distribution shape and amplitude with natural regeneration amount, obtained in survey on undisturbed forest. It resulted in three ecofisiological groups: shade tolerants species; intermediary species; and shade intolerant species. Shade tolerant and intermediary species were predominant (more than 90% of tree species DBH=25cm), indicating that the forest is in mature phase.

3) The objective of this study was to evaluate the response of three tropical herbaceous leguminous, Mucuna preta (Stizolobium aterrimum), Mucuna cinza (Stizolobium cochinchinensis) Feijão de porco (Canavalia ensiformes) submitted to different leveis of triple superphosphate (0, 25 and 45 ppm P) and dolomitic limestone (0,4 and 8 t/ha) in greenhouse conditions. The experimental design was a rondomized block where the treatments were applied in a 3x3x3 factorial with two replicates. Age of plants was introduced as a treatment in order to determine the rate of lenght of growth ofbranches and the experimental design was transformed to a 3x3x3x4 factorial. The parameters analysed were leaf area and dry matter. The mucuna cinza showed in the first 30 days a higher superior growth in relation to anothers species studied. After 45 days of the start of the experiment liming increased plant growth. The leveis of liming and phosphorus caused a statistical significam increment (P>0,05) of leaf area. The interaction phosphorus x liming increased (P<0,05) the dry matter production of the aerial parts of the plants.

4) P adsorption by the surface horizon (0-15cm depth) of plinthic soíls wilh different ciay leveis from the Marajó island, Pará, Brazil, was determined using a batch-type technique. Soil samples were equilibrated with 0,01M CaCl2, solutions having from 0 to 25 mg.l-1 P in a randomized experiment with three replicates/treatment. Adsorption maxima and affinity constants for P adsorption were calculated from the linear form of the Langmuir adsorption equation, Results showed that P adsorption increased with concentration of P in the equilibrium solution and with the clay levei of the soil sample. Highest value for P adsorption (838 mg. kg-1 of soil) was oblained in the plinthic soil with 10% clay whereas the highest affinity constant (0.215 l.mg-1) for the plinthic soil with 4% clay, suggesting that there were differences in the mineralogical composition of the soil samples used.

5) Trenchs to the depth of 2 meters were open to determine changes in chemical properties of an yellow latosol, medium textured, under secondary forest (FS) 40 years-old, slash an bum of secondary forest (DQ), cocoa plantation (CC) and degraded pasture (PA). pH, sum of bases, exchangeable Al, available P. organic C and total N were determined in soil samples collected in Ap, AB, BA and B horizons at each management system. Results showed that the chemical properties, weth the exception of Al, decreased with depth of samplmg. The slash and burn of secondary forest had the highest values of bases (25.1 mmol /kg soil), pH (5.7) and the lowest level of Al (0.9 mmol /kg soil) in the Ap horizon. Highest values of available P (15.5 mg/kg soil) was found in the Ap horizon of the cocoa plantation. Highest leveis of organic matter (33.7 g/kg soil) and total N (1.2 g/kg soil) were found in the Ap horizon of degraded pasture and secondary forest, respectivelly.

6) The objective of this experiment was to evaluate the growth and accumulation of macronutrients tn seedlings of Eucalyptus urophylla with a 6 months of age. The experiment was done at greenhouse conditions with a completely randomyzed design having 8 treatments and 6 replications. The substracts used were horizons (Ap and AB) of an amazon Latosol, which was previously submited to the following soil managements; secondary forest (FS), slash and buming (DQ), cacao crop (CC) and abondoned glassland (PA). The best results of dry matter production of aereal part of Eucalyptus were found in the Ap horizon of the PA system with values of 14.24 g/pot for the leaves and 15.04 g/pot for the stem. The horizon AB of the FS system with 1.71 and 1.42 g/ pot for the leaves and stem respectivelly. The greatest production of dry matter of leaves and stem were proporcioned in the horizon Ap and the least values of dry matter in the horizon AB independently of the soil management used. The greatest concentrations of nutrients N, P, K, Ca and Mg in the leaves of the Eucalyptus seedling did not correspond to the greatest dry matter production. The nutrients requested to the seedlings were taken in the following decreased order: N (17.3 g/kg dry matter) > K (8.1 g/kg dry matter) > Ca (6.3 g/kg dry matter) > Mg (1.4 g/kg dry matter) > P (0.8 g/kg dry matter).