CARBON STORAGE IN Eucalyptus ssp. FORESTS IN DIFFERENT AGES IN SMALL RURAL AREAS IN SOUTH BRAZIL

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1 CARBON STORAGE IN Eucalyptus ssp. FORESTS IN DIFFERENT AGES IN SMALL RURAL AREAS IN SOUTH BRAZIL Mauro Valdir Schumacher 1, Rudi Witschoreck 2, Francine Neves Calil 3 1. INTRODUCTION Nowadays, the eucalyptus is the most used specie in reforestation, and Brazil has the most planted area, which is equivalent to almost 50% of the world area (Leão, 2000). In the area where this study was conducted, the reforestations with eucalyptus show many positive aspects. Economically, the eucalyptus forests give, cheap biomass that allows activities that need this source of energy. Ecologically, besides decrease the pression under the rare remaining natural forests, the plantings of eucalyptus allow a better area utilization, this way poorest areas, bad drained or with accidental topography. Nowadays, the faster grown forests, mainly the ones with eucalyptus, are being characterized as atmospheric carbon drainages. Since the industrial revolution, due to the fossil fuels utilization and the forests destruction, there was an elevation of more than 20% in the carbon dioxide (CO 2 ) concentration in the atmosphere (Lal et al,.1998). The greenhouse effect, is a natural phenomenon, from which the carbon dioxide is one of the components, that can cause environmental problems (Odum, 1988). As the plants has the capacity to fix carbon in its organic structure, due to photosynthesis, the forest plantings are a alternative to the carbon sequestration. In global way, the biomass contais about 650 Gt of carbon, similar value as found in the atmosphere 755 Gt, and less than the half carbon in the soil, that is about 1720 Gt. After the LISTOSFERA with millions of Gt, the oceans are the main carbon reserve, with Gt, Krapfenbauer (1991); Sombroek et al. (1993); Brown et al. (1996). It is estimated that in each year, 6 Gt of carbon are because of the burnt of fossil fuels and 2 to 4 Gt due to the forest destruction. From this total, 6 Gt are fixed in the oceans 1 Dr. nat. techn. Professor Adjunto do Departamento de Ciências Florestais. Laboratório de Ecologia Florestal, UFSM, RS, Brasil. schuma@ccr.ufsm.br 2 Engenheiro Florestal. Laboratório de Ecologia Florestal, UFSM, RS, Brasil. rwitschoreck@yahoo.com.br 3 MSc. em Engenharia Florestal. Laboratório de Ecologia Florestal, UFSM, Brasil. francine.calil@terra.com.br

2 by the carbon cycle and about 3 Gt keep in the atmosphere increasing the greenhouse effect. With the objective to establish the reduction of gases emission, in 1997, in Japan was assigned the Kyoto protocol. This document has as objective to reduce the gases in about 5 to 8%, based on the emissions in 1990, between 2008 and 2012 (first period). Besides, the Kyoto protocol offers information to the market (between countries), to the projects dedicated to carbon sequestration (FAO, 2002). To establish an international market that negotiate quotes of this new commodity, this study had as objective to begin the obtention of data, to do estimatives of carbon storage in Eucalyptus ssp. stands in the small rural areas in three states of the south of Brazil. 2. MATERIAL AND METHODS 2.1 Site characteristics The data collection of this study was carried out in small rural area in the city of Vera Cruz, in the state of Rio Grande do Sul, Brazil. Due to Köppen, the area conceives the weather Cfa, which corresponds to subtropical (Moreno, 1961). The average annual rainfall is about mm. The soils of the region have as original material sandstone, silt and clay, prevailing from the class Alisoil (Streck et al., 2002). 2.2 Forest Inventory The forest inventory was conducted in 2,4,6 and 8 years old Eucalyptus spp. Forests, with surveys of four 12 m x 20 m plots in each of the stands, where all the diameters at breast height (DBH) and 20% from the total heights were measured.

3 2.3 Soil and biomass sampling Based on the forest inventory data, the diametric variation observed in each one of the stands, was separated in 3 diametric classes (DBH), being cut two trees with mean diameter in each class, totalizing 6 trees in each stand. After the cut, the biomass was divided in the following components: leaf, live and dead branch, wood, bark and root. Concomitantly to the bark and wood biomass determination a stem cubing was done. To facilitate the weight and the diameter obtention with and without bark, the stem was cut in the cubing points. Each log was weighed with and without bark, to the wood and bark biomass obtention. The last biomass component to be collected was the root system; it was done due to excavation, washing and weight. To the biomass and carbon quantification in each tree, a sample of the components: leaf, dead and live branch and root was collected; and three samples of bark and wood, in the following positions along the stem: DBH (1, 30 m from de tree base), 50% and 75% of the total height. This way of sampling wood and bark, had as objective to cover some possible variations along the stem. In this study was considered as understorey all kind of vegetation, native or exotic. In the center of each one of the forest inventory plots were marked out a 4 m x 3 m plot, where was collected all the biomass above and below ground (root), weighed and sampled. To estimate the litter 10 samples of 25 cm x 25 cm were collected, in each one of the plots from the forest inventory, totalizing 40 samples by stand. Each one of the biomass samples collected were weighed in digital balance 0,1 g, identified and stored in paper bags. For the soil density and carbon content evaluation, samples were collected in each 10 cm, until the depth of 1 m, in 4 trenches, totalizing 40 samples in each stand. The method used in soil density determination is Kopecky (Embrapa, 1997), and the amounts of carbon due to Tedesco et al. (1995).

4 2.4 Carbon quantification In the lab, the biomass samples were dried in stove (75 C) during 72 hours. After the dry, the samples were weighed in electronic balance 0,1 g, to the dry mass determination. After the dry, the samples were milled in Wiley mill with sieve 20 mesch. The carbon contents determination was conducted in the Forest Ecology Laboratory from the Federal University of Santa Maria due to the methodology (humid way) described by Tedesco et al. (1995). The individual mass of carbon in each component or compartment sampled was obtained by the result of biomass and carbon content. The estimative of carbon storage, in eucalyptus compartment, was possible due to the regression equations adjustment correlating individual values of carbon in each component with dendrometric variables as dbh and total height of the tree. The carbon storage in understorey and in the litter was quantification due to extrapolation, in function of the average obtained values in the units of measurement, and in the soil, due to the result between the carbon amount, volume and soil density. 3. RESULTS AND DISCUSSION stands. Table 1 shows some dendrometric characteristics of the Eucalyptus ssp. studied Table 1. Dendrometric characteristics of the studied stands. Dendrometric measure Stand age (years) (unit) Mean dbh * (cm) 6,5 6,8 12,8 13,2 Density (tree ha -1 ) 2645,8 3569,4 2354,2 2375,0 Dominant height (m) 11,9 14,0 27,4 28,6 Wood volume with bark (m³ ha -1 ) 48,4 80,2 344,4 414,0 *dbh= diameter at breast height.

5 In carbon storage estimative in the biomass components, regression equations were used, showed in Table 2. It is observed that the carbon storage (kg/tree) is highly correlated with the dendrometric variables total height (h) and diameter at breast height (dbh). Table 2. Regression equations used to estimate the carbon in different biomass components of eucalyptus. Equation 1/ R²aj. Leaf logy = -1, , logd - 1, logh 0,91 20,4 Live branch logy = -1, , logd - 1, logh 0,92 18,3 Dead branch logy = -3, , logh 2/ 0,71 39,2 Bark logy = -2, , logd + 0, logh 0,99 7,9 Wood logy = -2, , logd + 1, logh 0,99 2,4 Root logy = -2, , logd + 0, logh 0,99 9,0 Total biomass logy = -1, , logd + 0, logh 0,99 3,8 log = logarithm, d= diameter at breast height, h= total height; 1/ significantly in 1% of probability; 2/ adjusted equations only to 2 and 4 years old stand data. Syx (%) The dead branch, is the tree component that shows the less expressive values due to the statistical parameters that measure the adjust level of the regression equations, followed by the leaves and the live branch, which is linked to the higher availability of individual biomass values of this components when compared to bark and wood. Due to the carbon contents in eucalyptus biomass, it is verified the same pattern in different ages, which follows this decrescent sequence: leaf > wood > root > live branch > dead branch > bark (Table 3). The amounts of carbon in understorey vegetation are lower than the eucalyptus biomass, the contents above ground are upper to the roots. The litter characteristics are linked to the nature of the constituent material, as leaves, branches and bark. The proportion of each constituent, as well as, the level of decomposition, that is affected by the soil characteristics, will condition the amount of carbon in this compartment.

6 Table 3. Average carbon content in eucalyptus biomass, understorey, litter and soil. Compartment/ component Stand age (years) Average Leaf 469,8 460,9 460,6 462,4 463,4 Live branch 410,8 406,4 401,2 406,4 406,2 Eucalyptus Dead branch 405,1 400,0 402,6 Bark 364,3 363,1 361,3 358,8 361,9 Wood 414,3 425,8 423,3 425,7 422,3 Root 412,3 414,0 424,1 425,6 419,0 Understorey Above ground 384,2 361,2 386,4 372,0 375,9 Root 339,0 320,8 387,1 379,7 356,6 Litter 408,6 439,1 404,6 448,1 425,1 Soil 5,9 3,6 6,6 4,6 5,2 Excepted the wood, all the other componets showed a decrease in percentage in carbon storage in these compartments, with an age increasing. Do to the understorey, as well as the age increases, will form openings in the canopy of the forest, allowing the light entrance, intensifying the development in understorey, increasing the importance of this compartment in the total storage of carbon in the eucalyptus stands (Table 4). The litter deposition in eucalyptus stands shows a season variability. Mainly are weather factors as temperature and humidity that influence the intensity of deposition in different seasons of the year. The leaves constitute the higher parts of the wastes that fall on the soil, and this percentage increases with the age, until a certain point, where so, decreases due to the increase in the fall of branches (Reis & Barros, 1990). The litter values tend to increase with the age of the stand until get the balance point when the deposition and decomposition taxes are equivalent (Table 4).

7 Table 4. Carbon storage (Mg ha -1 ) in eucalyptus biomass, understorey, litter and soil (until 1 m depth). Compartment/ component Eucalyptus Understorey Stand age (years) Leaf 1,26 1,85 2,78 3,17 Live branch 2,21 3,26 5,01 5,62 Dead branch 0,22 0,39 Bark 0,77 1,26 4,28 5,02 Wood 5,28 9,49 59,95 73,35 Root 1,38 2,30 8,89 10,70 Total 11,12 (11,1) 1/ 18,55 (23,0) 80,91 (44,5) 97,86 (55,2) Above ground 0,61 0,46 0,67 1,22 Root 0,10 0,08 0,18 0,34 Total 0,71 (0,7) 0,54 (0,7) 0,85 (0,5) 1,56 (0,9) Litter 1,65 (1,6) 2,62 (3,3) 4,78 (2,6) 5,50 (3,1) Soil 86,45 (86,6) 58,72 (72,9) 95,30 (52,4) 72,09 (40,6) Total 99,88 80,52 181,72 177,36 1/ values in brackets refer to the % contribution, related to the total carbon storage of the stand, from the respective compartment. As we can verify in Table 4, the soil represents a huge reservatory of carbon. The manageable component of this element is the organic matter of the soil, that has as main sources, the litter deposition, the root deposition and the forest harvests wastes. The content of organic matter of the soil is condicionated by the edaphoclimate factors, but also, is very sensible to the management practices, mainly in tropical and subtropical conditions, where prevails a condition of high temperature and rainfall. Due to this data, is evidenciated the importance of management practices that improves the entrance of organic wastes to the soil, or on the other hand, slow the organic matter decomposition, what will improve the carbon fixation by this compartment.

8 4. CONCLUSIONS The carbon storage in the 2, 4, 6 and 8 years old stands, was respectively, in the eucalyptus biomass: 11,12; 18,55; 80,91 and 97,86 Mg ha -1, understorey: 0,71; 0,54; 0,85 and 1,56 Mg ha -1, in the litter: 1,65; 2,62; 4,78 and 5,50 Mg ha -1 and in the soil: 86,45; 58,72; 95,30 and 72,09 Mg ha -1, The eucalyptus forests show a great capacity of production of biomass, what makes them an excellent drains of atmospheric carbon. 5. REFERENCES BROWN, S. et al. Management of forests for mitigation of greenhouse gas emissions. In: WATSON, R.T.; ZINYOWERA, M.C.; MOSS, R.H. (eds.) Climate change 1995, impacts, adaptations and mitigation of climate change: scientific-technical analyses. Report of Working Group II, Assessment Report, IPCC, p Cambridge, Reino Unido, Cambridge University Press, EMBRAPA. Centro Nacional de Pesquisa de Solos (Rio de Janeiro, RJ). Manual de métodos de análise de solo. 2. ed. Rio de Janeiro, p. FAO. Organización de las naciones unidas para la agricultura y la alimentación. Perspectivas mundiales del suministro futuro de madera procedente de plantaciones forestales. Roma, Italia, KRAPFENBAUER, A. A importância da floresta no equilíbrio do dióxido de carbono. In: SEMINÁRIO SOBRE A PRODUÇÃO DE CELULOSE NO BRASIL E O MEIO AMBIENTE. Curitiba, 1991.

9 LAL, R.; KIMBLE, J.; FOLLETT, R.F. Pedospheric processes and the carbon cycle. In: LAL, R.; KIMBLE, J.; FOLLETT, R.F.; STEWART, B.A. (eds.) Soil processes and the carbon cycle. CRC Press LLC, 1998, p LEÃO, R.M. A floresta e o homem. São Paulo: Instituto de Pesquisa e Estudos Florestais, p. MORENO, J.A. Clima do Rio Grande do Sul. Porto Alegre: Secretaria da Agricultura, p. ODUM, E.P. Ecologia. Rio de Janeiro: Guanabara Koogan, REIS, M.G.F.; BARROS, N.F. Ciclagem de nutrientes em plantios de eucalipto. In: BARROS, N.F.; NOVAIS, R.F. (eds.). Relação solo eucalipto. Viçosa: Ed. Folha de Viçosa, cap.7, p SOMBROEK, W.G.; NACHTERGAELE, F.O.; HEBER, A. Amounts, dynamics and sequestering of carbon in tropical and subtropical soils. Ambio, v.22, n.7, p , STRECK, E.V.; KÄMPF, N.; DALMOLIN, R.S.D. et al. Solos do Rio Grande do Sul. Porto Alegre: UFRGS, EMATER/RS, p. TEDESCO, M.J.; GIANELLO, C.; BISSANI, C.A.; BOHNEN, H.; VOLKWEISS, S.J. Análise de solo, plantas e outros materiais. Porto Alegre, Departamento de Solos, UFRGS, p. (Boletim Técnico n.5). VIEIRA, E.F. Rio Grande do Sul: geografia física e vegetação. Porto Alegre: Sagras, p.