BOLETIM DA FACULDADE DE CIÊNCIAS AGRÁRIAS DO PARÁ. n. 28, jul./dez. 1997.

Abstract

1) The objective ofthis work was to study the floristic composition, aggregation and the structure of natural regeneration of a forest, in a plot measuring 500m x 20m (lha), subdivided in 100 subplots of lOm x lOm, placed in Cauaxi Farm, at Paragominas-Pa. The plot was located in the center of stand V which is being used by the Tropical Forest Foundation (TFF) to accomplish research works on low impact forest logging and management, with 100 ha and it works as a plot of permanent preservation. In the subplots were identified, measured and whole maped the plants with DBH lOcm. In 10 of those subplots were classified, measured and mapped ali the individuais 5,1 and 9,9cm DBH, and settled 50 microplots measuring 4 m2 (2m x 2m), in which were enumerated and classified whole the plants with less than 5cm DBH, which were considered as natural regeneration. The floristic composition of the plot inventoried was formed by 34 botanical families, 58 genera, 75 species and 1.055 individuais, of which 569 were trees, 295 were lianas, 182 were bushes and 9 were palm trees. The families better represented in the area was Maranthaceae (120 plants), Mimosaceae (113 plants), Bignoniaceae and Caesalpiniaceae (107 plants), and Sapotaceae (102 plants), accounting for about 52% of the whole population. The species better distributed were Arrahidae agensis (97 plants), Rinorea guianensis (93 plants), Bauhinia splendens (87 plants), Pouteria guianensis and Salada insignis (70 plants), Calaihea capilata (69 plants) and Inga edulis (68 plants), representing 52% ofthe individuais' total. The percentile of species with less than 4 individuals/ha were of 40%. The values of the homogeneity degree and of the Jentsch" mixture quotient evidenced a vegetable community with high heterogeneity. The Mc Guiness' index revealed a larger number of species with tendency to the grouping, while the Fracker' & Brischle' index showed a larger amount of grouping species.

2) The aim of this study was to evaluate the initial behavior of Aniba rosaeodora Ducke (rosewood), under different shading conditions. Seedlings of rosewood from natural regeneration were kept in shade houses instaled in nursery conditions, at 0%, 30% , 50%, 70% of shading, during ten months. The experiment design was carried out in a randomized completblock, in split-plot, with three replicates, where the shading conditions were the principal factor and the three provenances of rosewood (Manicoré, Floresta Nacional do Tapajós-FLONA and Curuá-Una) were the secondary factor. It was found that the growth (stem height, diameter, leafarea, numberof leaves) and biomass allocation patterns, varied sensibly in response to shading. This specie showed superior growth at 50% of shading, in relation to anothers shade conditions. On the other hand, the survival decreased with increasing in light intensity. Under 0% of shading, for example, the survival was 65,2% for seedling from Manicoré, 62,1% for FLONA and 55,6% for Curuá-Una. These preliminary results indicated that during the juvenile phase, the ^4. rosaeodora, showed caracteristics of tolerant specie.

3) This paper presents an structural analysis ofsecondary successions on fallows of 6 years old after clear out and 17 and 30 years old after wood selective harvesting, at CEPLACs Experimenta! Station 17 km near Belem, Pará, Brazil. The vegetation lOcm height and above were sampled by three plot sizes; I) Plots 20mx50m, with subplots 10mx20m, where plants 20cm dbh and more were measured; II) Four plots lOmxlOm size, in each 20mx50m plots, where plants ffom 5cm to 20cm dbh were measured; and III) Plots 2mx2m, in each 1 Omx1 Om plots, where plants 1 Ocm height and up to 5cm dbh were counted on three size classes. The structure of ecosystems was analysed according to IV1A (Amplified Importance Value Index) that shows horizontal and vertical forest aspects. In 6 years fallow, with 42 species, the only individual more than 20cm dbh belonging to Schizolobium amazonicum produced a hight IVIA, even without natural regeneration. The 17 years fallow was 65 species rich, 5 of which are more than 20cm dbh and prevail over in terms of IVIA, with 83%. Between 6 and 17 years fallows there were 24 species, that account for 13,2% and 78,7% of IVIA, respectively. The 30 years fallow is 67 species rich, 27 of which are 20cm dbh and more, standing ontPouwuma cecropiaefolia for 16,9% in terms of IVIA. Comparing 6 and 30 years fallows shows that 20 species were in beginning of succession. The 17 and 30 years fallows shows 42 species in common. There was a great floristic variation among 6 and 30years fallows, increasing according to age. The 6 years secondary forest is still developing on the contrary on 30 years one that showed trails iike a mature forest.

4) The effect of indole-3-butyric acid (IBA) on the rooting of Tachi-branco (Sclerolobiumpaniculatum Vogel) cuttings was investigated. Tachi is a tree of the family Caesalpinaceae, found in Peru, Suriname, region North, Northeast and Central of Brazil. The Tachi branco's timber is used to fuelwood and building. Cuttings were taking from seedlings of Tachi, with approximately 70 cm of height. Cutting length was standardized to 10 cm, two leaflets with per cutting. After to trimming their leaf area to approximately 50%, the cuttings were treated immediately with four indole-3-butyric acid concentrations: 0% (only ethanol), 2.000 ppm, 4.000 ppm e 6.000 ppm. A total of 200 cuttings, were randomly arranged 5 plots and 4 treatments. It was found that the treatments containing indole-3-butyric acid, estimulated adventitious rooting formation, accelerate the rooting and increase the number of cuttings rooted in stem cuttings of Tachi branco. These result indicated that propagation of Sclerolobium paniculatum, by stem cuttings take from juvenile material, is technically viable, if the cuttings were treated with 4.000 ppm of IBA.

5) This paper evaluates the incidence of weeds in the sequence rice-corn-cowpea as affected by fertilization and methods of weed control. The study was performed in the county of Santo Antonio do Tauá, Pará state, on médium textured Latosol soil (oxisol). The climat is Ami under Kõppen classification. The experimental design was inrandomized blocks with four replications and a split plot arrangement oftreatments. The main plots evaluated three weed control methods: a) two weed cutting by hoe in each crop; b) mulch at 5 ton/ha; c) one application of herbicide for crop. In the sub-plots three fertilization conditions were tested: a - no fertilzer; b - composted manure; c - NPK fertilizer. The weed control was evaluated by total dry matter in an area of 0,5 m2 and the dry matter production ofthe four predominam weed species. The results showed that weed control methods have a similar effects on the weeds total dry matter, production but different effects on the weed species. The cutting by hoe stimulated the growth oíDigitaria sp, the mulching stimulated the growth of Commelina sp. and de Propanil herbicide the developpement ofthe Eragostis sp. Manuring and NPK fertilizer increased the weed incidence as compared with no fertilizers treatment and affected the growth ofthe weed species. Manure increased the growth ofEleusine sp. and the NPK fertilizer the growth ofDigitaria sp.

6) The largest part ofthe Brazilian forest resources are in the Amazon Region, which cover about 260 million hectares. More than 90% of this area is covered by terrafirme and várzea forests, with a very rich occurrence of timber species. As the heterogeneity is a strong feature of tropical regions, the timber species in these forests have wood with great variability on their properties. These properties vary within the same species, according to its natural habitat, or site where it was introduced, and other factors as for example genetics and silviculture, among others. Therefore, its is necessary to know better the wood properties in relation to silviculture, mainly for commercial species and for those with potential characteristics for future marketing. Some native species have been planted because they present a fast growth rate, but few information about wood properties and its relation to silvicultural system or silvicultural method of planting are available. In order to contribute to improve information on interation between wood properties and silviculture, this work had as main objective to study the mechanical wood properties ofBagassa guianensis Aubl. in four spacement, in a sixteen-year-old plantation of 5.75 ha at CPATU Experimental Station in Belterra, Para State. Considering the various uses of Bagassa guianensis, from buildings to shipping and fumiture, the results of this work showed that the species can be planted in different spacing, according with its proposed final use. For example, to obtain wood for building it is suggested to plant in spacing of4m x 4m, and for producing veneer and fumiture the suggestion is to plant in smaller spacements (2m x 3m or 3m x 3m).

7) General Circulation ModePs (GCM's) show for the next decade an increase in green house gases concentration as well as for the global warming, between 1.5 a 4.5 °C, with on likelihood decreasing of rain on the Amazon ecosystems. Considering this tendency, this work had the objective to evaluate the effect of water stress intensification, on dry season, through of treatments for restriction of rain, on C02 production from soil of primary forest of upland, Two statistic designs are utilised, to make a descriptive analysis between one plot lOm x 10 m, that to be received a treatment of restriction of rainfall for 4 year compared to a control, descriptive design; and ANOVA analysis in five blocks (block design) with three treatment of moisture: 100, 50 e 0% of rain exclusion, on a primary forest in Paragominas {2o59' S, 4703 TW), State of Pará. The soil moisture was measured with time domain reflectometry (TDR) and the gavimetric method, the month measurement of soil C02 fluxes was to make in the field through of air circulation between static soil chamber and a infrared gas analyser-(LiCor). The results revealed an increase of dead roots mass, decrease in root growth and soil C02 flux will decrease of soil moisture. Through of this evidence, we can suggest that a decrease of soil moisture in Paragominas primary forest, will be able in the future to promove the increase on probability of this forest became inflammable and therefor an increase on CO, flux in the atmosphere.

8) An experiment was conducted at Companhia Real Agroindustrial, Tailândia, Pará State, in yellow latosol, to determine the dry matter production and concentration of macronutrients of Pueraria phaseoloides L., according to its age in palm oi! plantation, The experiment design was a randomized with four replicates. The results showed that the dry matter production decreased throughout the years, in a progressive order. The concentrations ofN, P, Ca, Mg and S in Pueraria phaseoloides varied with age. The variation in K concentration was observed only in the green tissue. The concentration of N, P and K were higher in the green tissue, where as the Ca, Mg and S concentrations were higher in the dead tissue. The sequence of prevalent levei was N > K > Ca > Mg > P > S, in the green tissue.In the dead tissue the sequence was: N > Ca > Mg > K > S > P.

9) We study phenological processes of Hevea brasiliensis M. Arg and Sapium curupita Hub in the flood plain of Amazon river at Para Island, Afua, Para (0o 3'S, 51° 10' W) based on the phenophases of flowering, fruiting, dissemination and leaf fali of six ideotypes of each specie. The tree species subpopulations (N=12) was selected in transect of 10 m x 2000 m (2 ha) and monitored for 15 months. The H brasiliensis showed flowering phenophase in the dry season lasting three months with peak in July showing an annual pattem. The S curupita started flowering in the end of dry season lasting until the beginning of wet season lasting two months with peak in February with dissemination phase in March and April. Both species showed leaf fali deciduous pattem.

10) The objective of this research was to evaluate the residual soil moisture content ofa red yellow Latosol under two different soil uses. secundary native forest and a cultivated area. In each area it were collected soil simples, in each soil depths of 0-20, 20-40,40-60, 60-80 e de 80-100 cm, for particle-size analysis, bulk density, soil porosity and water retention capacity. In four selected periods (april, july, november/1996 and january/1997) and in each area it were collected soil simples for soil moisture content. The cultivated treatment was that presented the least values of residual soil moisture content in relation to the secundary native forest in every selected periods. The difference of soil moisture content between the two soil uses was statistically significam according to the t test. This fact means that there was effect ofsoil use in amount ofwater retention of the two soils.