Effect of rosewood plantation chronosequence on soil attributes in Central Amazonia

Rosewood (Aniba rosaeodora Ducke) is an endangered Amazonian tree species that produces a commercially valuable essential oil, used mainly in cosmetics and fine fragrances production. The species can also be used in reforestation programs, which generate jobs and as a source of income and reduce the pressure of exploitation on natural rosewood populations. The objective of this study was to verify the influence of rosewood stands on physical and chemical soil attributes. This study was conducted at a rural farm in the Males municipality, 350 km from Manaus, Amazonas State, Brazil. Samples were collected in five areas; 4-, 10- and 20-year-old rosewood stands, and 15- and 60-year-old secondary forests. The latter two served as control treatments, reflecting natural spontaneous succession conditions over time. Soil was sampled at 10 equidistant points within each area to measure physicochemical attributes, and at the center of each one, a soil profile was dug for description and classification of morphological characteristics. Based on the profile description, the soils were classified as Xanthic Hapludox. The results show that soil conditions under 20-year-old rosewood stand resembled those beneath the 60-year-old secondary forest, and likewise for the soil under the 10-year-old rosewood stand and the 15-year-old secondary forest. The soil bulk density ranged from 0.81 to 0.99 g cm(-3) among all areas and no significant difference was found (P = 0.052). With exception to 4-year-old stand, the organic matter (2.68-5.87%) and carbon stock (18.57-31.71 Mg ha(-1)) did not differ significantly between stands and control treatments. For the soil macronutrients, nitrogen (0.10-0.22%), phosphorus (1.17-11.70 mg kg(-1)), calcium (0.03-0.31 mg kg(-1)) and magnesium (0.02-0.16 mg kg(-1)) were higher or equal in the rosewood stands in comparison to the two controls, while the potassium values (0.03-0.36 mg kg(-1)) were significantly higher in 60-year-old secondary forests only compared to the 10-year-old rosewood stands (P = 0.005). The soil beneath the 4-year-old rosewood stand, however, differed from the other four areas, having significantly higher natural clay content ( > 600 g kg(-1)) and higher topsoil chemical concentrations, associated with the more recent burning. This result represents the first step in addressing concern about sustainable soil use in rosewood forestry economics. Consequently, this kind of rosewood plantation can be recommended as an appropriate use of historically exploited areas, providing economic return from local biodiversity. (AU)