Export and nutritional replacement in the first thinning of Pinus taeda L. in a second rotation area

O trabalho tem por objetivo quantificar a biomassa, exporta\ue7\ue3o e reposi\ue7\ue3o dos nutrientes em \ue1rvores do primeiro desbaste de um povoamento de Pinus taeda , em Cambar\ue1 do Sul, RS. Para isso, foi realizado um invent\ue1rio em tr\ueas parcelas (60 m x 60 m), sendo abatidas 3 \ue1rvores por parcela. Foram mensuradas ac\uedculas vivas e mortas, galhos vivos e mortos, casca, madeira comercial e madeira do ponteiro com casca. A biomassa totalizou 44,5 Mg ha-1, com 62,8% de madeira, 10,3% de galhos vivos, 8,9% de casca, 10,1% de ac\uedculas vivas, 6,1% de galho morto, 3,5% de ponteira com casca e 0,5% de ac\uedcula morta. A quantidade total de nutrientes na biomassa, em kg ha-1, foi de: 100,5 de N; 51,1 de Ca; 46,8 de K; 18,2 de S; 14,3 de Mg; 11,7 de P; 0,599 de Mn; 0,158 de Fe; 0,435 de Zn; 0,181 de B e 0,177 de Cu. A quantidade de adubos a serem repostos depender\ue1 do tipo da explora\ue7\ue3o. Se ocorrer remo\ue7\ue3o total da biomassa, a quantidade de adubos a ser reposto ser\ue1 de 391 kg ha-1, e se considerar apenas a retirada da madeira esta reposi\ue7\ue3o ser\ue1 aproximadamente 60% inferior, 169 kg ha-1.This study aimed to quantify biomass, the export and nutrient replacement in trees of a first thinning Pinus taeda L. stand, in Cambar\ue1 do Sul, RS state. To do so, a forest inventory was done in three plots (60 m x 60 m), where three trees were cut in each plot. Live and dead needles, live and dead branches, bark, wood (bole) and wood from tip with bark, were measured. Total biomass was 44,5 Mg ha-1, being 62,8% of bole wood, 10,3% live branches, 8,9% bark, 10,1% live needles, 6,1% dead branches, 3,5% of wood from tip with bark and 0,5% dead needles. Total nutrients in biomass, in kg ha-1, was: 100,5 of N; 51,1 of Ca; 46,8 of K; 18,2 of S; 14,3 of Mg; 11,7 of P; 0,599 of Mn; 0,158 of Fe; 0,435 of Zn; 0,181 of B and 0,177 of Cu. The quantity of the fertilizer to be replaced will depend on the exploration type. If the total biomass occurs, the quantity of the fertilizers to be replaced will be of 391 kg ha-1, and if it is considered just the wood harvest this replacement will be 60% inferior, 169 kg ha-1

CALIBRATION OF MODEL 3-PG FOR Eucalyptus saligna IN THE REGION OF GUA\ucdBA, RIO GRANDE DO SUL STATE

O trabalho teve como objetivo calibrar o modelo 3-PG para Eucalyptus saligna usando as var\ue1veis di\ue2metro a altura do peito (DAP), altura total, volume de madeira e biomassa de galho, casca e lenho. O estudo ocorreu na regi\ue3o de Gua\uedba - RS, sendo utilizados plantios clonais de Eucalyptus saligna, em diversos espa\ue7amentos. Foram selecionadas seis idades ao longo do ciclo de cultivo (2\uba ao 7\uba ano). Realizou-se o invent\ue1rio florestal para a coleta de biomassa (tr\ueas \ue1rvores, sendo fracionadas em: lenho, casca, galhos e folhas). Na \ue1rvore m\ue9dia de cada parcela, mensurou-se a biomassa de ra\uedzes at\ue9 a profundidade de 1 m. An\ue1lises f\uedsicas e qu\uedmicas em amostras de solo foram realizadas nas camadas de 0 a 20 cm, 20 a 40 cm e 40 a 100 cm. A deposi\ue7\ue3o de serapilheira foi estimada atrav\ue9s da aloca\ue7\ue3o de quatro coletores quadrados de 0,5 m\ub2. A \ue1rea foliar foi obtida por fotografias digitais e, a partir destas, estimou-se a \ue1rea foliar espec\uedfica. Os par\ue2metros fisiol\uf3gicos foram mensurados em seis parcelas, uma em cada idade. Os par\ue2metros clim\ue1ticos foram fornecidos pela EEA da UFRGS, localizada em Eldorado do Sul. A valida\ue7\ue3o do modelo n\ue3o foi estatisticamente aceita, mas os seus dados estimados podem ser utilizados para estimar as vari\ue1veis estudadas, evidenciando o potencial do seu uso, por\ue9m, com a necessidade de estudos adicionais.The study aimed to calibrate the model 3-PG for Eucalyptus saligna for the following the diameter variables at breast height (DBH), total height, wood volume and branch, bark and wood biomass. The study took place in the region of Gua\uedba, Rio Grande do Sul state, Brazil. Clonal plantations of Eucalyptus saligna in various spacings were used. Six different ages were selected along the crop cycle (2nd to 7th year). After the forest inventory was carried out, the biomass of three trees fractionated into wood, bark, branches and leaves was collected. The biomass of roots on the average tree of each plot was measured to a depth of 1 m. Physical and chemical analyses were performed in soil samples from the layers: 0 to 20 cm, 20 to 40 cm and 40 to 100 cm. Litter deposition was estimated by allocating 4 square collectors of 0.5 m\ub2. The leaf area was obtained through digital photographs and thus the specific leaf area was estimated. The physiological parameters were measured in six plots, one at each age. Climatic parameters were provided by EEA of UFRGS University, located in Eldorado do Sul, RS state. The model validation was not statistically accepted, but their estimated data can be used to estimate the studied variables, demonstrating the potential of its use although additional studies for the application of the model to this species are still needed