Exportação e reposição nutricional no primeiro desbaste de um povoamento de <i>Pinus taeda</i> L. em área de segunda rotação

Abstract

RESUMOO trabalho tem por objetivo quantificar a biomassa, exportação e reposição dos nutrientes em árvores do primeiro desbaste de um povoamento de Pinus taeda, em Cambará do Sul, RS. Para isso, foi realizado um inventário em três parcelas (60 m x 60 m), sendo abatidas 3 árvores por parcela. Foram mensuradas acículas 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 acículas vivas, 6,1% de galho morto, 3,5% de ponteira com casca e 0,5% de acícula 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 dependerá do tipo da exploração. Se ocorrer remoção total da biomassa, a quantidade de adubos a ser reposto será de 391 kg ha -1 , e se considerar apenas a retirada da madeira esta reposição será aproximadamente 60% inferior, 169 kg ha -1 . Palavras-chave: exportação de nutrientes; tipos de colheita; formas de manejo. ABSTRACTThis study aimed to quantify biomass, the export and nutrient replacement in trees of a first thinning Pinus taeda L. stand, in Cambará 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 .

Sequential Management of Commercial Rosewood (Aniba rosaeodora Ducke) Plantations in Central Amazonia: Seeking Sustainable Models for Essential Oil Production

“…The results obtained confirm the findings of previous studies, where variations in nutrient concentration were linked to differences in tissue age and nutrient mobility [23,58]. Greater or lesser concentrations of some nutrients in the regrowing tissues occurs as a result of increased metabolic activity linked with the capacity of translocated nutrients from subterranean organs to above ground plant parts [59,60], which was observed in managed rosewood plantations.…”

“…In terms of need for nutritional replacement, it is important to recognize that the exported nutrients were stored by the plants throughout their cycle and the use of incorrect fertilization techniques can generate both economic and environmental losses [23]. As trees do not have the capacity to absorb and store large quantities of readily available nutrients, unabsorbed elements may enter in the soil solution, percolate deeply and then contaminate water resources.…”

“…Currently, harvesting occurs via removal of 100% of the crown [15][16][17], or of the entire tree, after cutting the trunk 50 cm above the soil [10,17], and then extracting the essential oil from all parts of the tree [18][19][20][21]. Clearly, at the moment of harvest, all nutrients assimilated from the soil by the plant are lost to future biogeochemical cycles at the growth site [22][23][24][25], leading to an export of nutrients that can compromise ecosystem productivity during future crop rotations [26][27][28].…”