Abstract
Eucalypt cultivation is an important economic activity worldwide. In Portugal, Eucalyptus globulus plantations account for one-third of the total forested area. The nutritional requirements of this crop have been well studied, and nitrogen (N) is one of the most important elements required for vegetal growth. N dynamics in soils are influenced by microorganisms, such as diazotrophic bacteria (DB) that are responsible for biological nitrogen fixation (BNF), so the aim of this study was to evaluate and identity the main groups of DB in E. globulus plantations. Samples of soil and root systems were collected in winter and summer from three different Portuguese regions (Penafiel, Gavião and Odemira). We observed that DB communities were affected by season, N fertilization and moisture. Furthermore Bradyrhizobium and Burkholderia were the most prevalent genera in these three regions. This is the first study describing the dynamic of these bacteria in E. globulus plantations, and these data will likely contribute to a better understanding of the nutritional requirements of eucalypt cultivation and associated organic matter turnover.
Highlights
Eucalyptus globulus Labill. occurs naturally in Tasmania and southwest Australia and was introduced into Portugal in the 1950s
Quantification of culturable diazotrophic bacteria (DB) Culturable diazotrophic bacteria were found in all studied areas
We found the principal bacterial community present in the eucalyptus forests to be Proteobacteria (Figure 5), one of the most diverse, which comprises various classes that contain at least one species of N-fixing bacteria [30]
Summary
Eucalyptus globulus Labill. occurs naturally in Tasmania and southwest Australia and was introduced into Portugal in the 1950s. The genus Eucalyptus belongs to the family Myrtaceae and is comprised of a variety of species distributed throughout the world and grown under a wide variety of environmental conditions [1]. Eucalypts are cultivated primarily for the production of cellulose, paper, boards, plywood sheets, charcoal and pharmaceuticals [1]. It is estimated that in 2030, due to strong demand, annual lumber consumption by industries will reach 2.44 billion m3, which represents a 45% increase over consumption in 2005 [2]. The rapid growth of eucalypts demands high availability of soil nutrients, especially nitrogen (N), which is absorbed and accumulated in large quantities [3,4]. The productivity of eucalypt forests is directly related to the nutrient balance of the soil
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