Dinâmica do carbono orgânico em espécies arbóreas de uma floresta estacional decidual no Rio Grande do Sul

Abstract

The carbon fixation potentials from some forest species from Seasonal Deciduous Forest, in Santa Tereza, RS, were studied. Based on the biomass accumulation data, which were sampled through the cut of five individuals of each specie, distributed in the diameter variation from each one and segregated in five different fractions (leaves, live branches, dead branches, bark and wood) and its respective amount of organic carbon, obtained through laboratorial analysis; as well as the in growth evaluations from the arboreous individuals with Circunference at Breast Height Q 10 cm, done in 1996, 1999 and 2003, in permanent plots; models were elaborated to describe the carbon accumulation for seven arboreous species. For Matayba eleagnoides, the selected models for carbon amount description were: C=b0+b1.hc 2 (leaves), C=b0+b1.hc 2+ b2 1/1,3-d (branches), C=b0+b1.d (barks) and C=b0+b1.d2 (live branches and wood). For Machaerium stiptatum: lnCf=b0+b1.d2hc (leaves); lnCgv=b0+b1.d2+b2.1/d2 (live branches), Cc=b0+b1.ht 2 (barks) and Cm=b0+b1.ht+b2.ht 2+b3.1/ht (wood). For Trichilia claussenii: C=b0+b1.d (leaves and barks), lnCgv=b0+b1.d (live branches) and lnCm=b0+b1.1/d2 (wood). For Allophilus edulis: Cf=b0+b1.d3 (leaves), Cgv=b0+b1.d (live branches), Cgm=b0+b1.1/hc 2 (dead branches); Cc=b0+b1.d2 (barks) and Cm=b0+b1.d+b2.d2 (wood). For Campomanesia xanthocarpa: Cf=b0+b1.d3 (leaves), lnCgv=b0+b1.d2+b2.hc 2+b3.1/hc (live branches), lnC=b0+b1.1/d2 (barks and wood). For Gymnanthes concolor: Cf=b0+b1.d3 (leaves), lnCgv=b0+b1.d2+b2.1/d2+b3.1/hc 2 (live branches), Cc=b0+b1.1/d2 (barks) and Cm=b0+b1.d2 (wood). For Trichilia elegans: Cf=b0+b1.hc (leaves), Cgv=b0+b1.1/1,3-d+b2.1/1,3-hc (live branches) and Cm=b0+b1.d3 (wood). Based on these models, the carbon accumulation was estimated (kg ha-1) in different fractions, for Matayba elaeagnoides: 6,1; 256,4; 20,0; 203,7; 1389,8 and 1876,0, respectively, for leaves, live branches, dead branches, bark, wood and total biomass For Machaerium paraguariense, in 1,2; 41,1; 16,5; 143,8 and 202,6, respectively, without dead branches in this specie. For Trichilia claussenii, in 96,8; 192,1; 33,1; 347,6 and 669,6, respectively, without dead branches. For Allophilus edulis, in 58,5; 527,2; 78,6; 133,8; 1995,0 and 2793, 1, respectively. For Campomanesia xanthocarpa in 27,2; 567,6; 55,0; 670,5 and 1320,3, respectively, without dead branches. For Gymnanthes concolor, in 9,9; 38,2; 5,0; 45,8 and 98,9, respectively, without dead branches. For Trichilia elegans, in 24,9; 95,9; 151,4; 471,0 and 743,2, respectively, also without dead branches. The species totalized, in Secondary Forest, 7,7 Mg ha-1 of carbon in the biomass; the accumulation decreases in the following way: : Allophilus edulis, Matayba elaeagnoides, Campomanesia xanthocarpa, Trichilia elegans, Trichilia claussenii, Machaerium paraguariense and Gymnanthes concolor. The biomass fractions that compose the studied species showed a preferential accumulation in the following sequence: wood>live branches>barks>leaves>dead branches. The species that showed the higher amounts of carbon in the leaves were Matayba elaeagnoides and Trichilia claussenii. For dead and live branches, also Matayba elaeagnoides. For bark was Trichilia elegans. For wood there were not statistical differences among the amounts of carbon. The carbon accumulation varied a lot in function of the input taxes and also the mortality of the species, during the evaluation period and also as a function of the individuals growth and consequently change in diameter class.