Wood density of trees in open savannas of the Brazilian Amazon

Abstract

Studies on basic density of woody species in Amazonian savannas are needed to convert data on woody volume to biomass. These ecosystems, which have large carbon stocks, emit greenhouse gases annually due to frequent burnings. Basic density (g cm −3: oven-dry weight/wet volume), measured from complete sample disks (bark, sapwood and heartwood), was calculated for the most abundant woody species in three types of open savannas (Sg: grassy-woody savanna; Sp: savanna parkland; Tp: steppe-like parkland) in Roraima, a state in the northern part of Brazil’s Amazon region. The species selected represent 90–95% of the woody biomass estimated in these ecosystem types. Seven additional species were lumped in an “others” group. In total, we sampled 107 trees: 40 in Sg, 37 in Sp and 30 in Tp. Bowdichia virgilioides (0.516 ± 0.021 (S.E.) g cm −3) was the species with the highest basic density, followed by the “others” group (0.485 ± 0.057 g cm −3), Curatella americana (0.413 ± 0.028 g cm −3), Byrsonima crassifolia + B. coccolobifolia (0.394 ± 0.019 g cm −3), Himatanthus articulatus (0.375 ± 0.020 g cm −3) and B. verbascifolia (0.332 ± 0.020 g cm −3). Basic density of the species with the greatest woody biomass in Roraima’s open savannas ( C. americana and B. crassifolia + B. coccolobifolia) did not differ significantly at the 5% level (ANOVA) among the three ecosystem types studied. Wood basic density in these savannas (weighted mean = 0.404 ± 0.025 g cm −3) is lower than that in Amazonian forests (weighted mean = 0.680 g cm −3). These results reduce uncertainty in calculations of carbon stocks and of greenhouse gas emissions from clearing and burning tropical savanna.