Microcalorimetric study of changes in the microbial activity in a humic Cambisol after reforestation with eucalyptus in Galicia (NW Spain)

• Published in: Soil biology & biochemistry 2006, Vol.38 (1), p.115-124
• Main Authors: Núñez-Regueira, Lisardo, Rodríguez-Añón, José A., Proupín-Castiñeiras, J., Núñez-Fernández, O.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; calorimetry; Chemical, physicochemical, biochemical and biological properties; Fast growing forest species; Fertility; forest soils; Fundamental and applied biological sciences. Psychology; indicator species; Microbial activity; Microbiology; Microcalorimetry; Physics, chemistry, biochemistry and biology of agricultural and forest soils; reforestation; Reforestations; seasonal variation; soil biological properties; soil chemical properties; soil physical properties; soil quality; Soil science
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2005.04.031

The microcalorimetric technique was used to analyse the influence of successive reforestations with Eucalyptus globulus Labill, a fast growing species, on the microbial activity in soil. With this aim, samples of similar origin soils, humic-eutrophic Cambisol, were collected from two adjacent land plots. One of the plots, to be taken as the reference, was not subjected to man activities for the last 100 years. The other plot was subjected to two reforestations in the last 20 years. For collection of the two samples, 100 m 2 homogeneous and perfectly defined zones were chosen in each of the adjacent land plots to obtain final representative bulk samples of 400 g each. The study was carried out using the microbial population as a bioindicator of the productive potential in soil. The experiments were carried out using 1 g soil samples that were treated with 1.25 mg glucose and stored at 4 °C for 3 months. The analysis was complemented by the determination of physical, chemical, and biological properties and environmental parameters. The study was performed over 1 year and samples were seasonally collected (spring, summer, autumn and winter) in the same zone situated in Viveiro (Galicia, NW Spain) with the objective of checking the influence of environmental conditions on the microbial activity in the two soils studied. From the measured results, it can be observed that soils subjected to reforestations suffer not only important changes in physical structure, such as an increase in bulk density, from 600 to 660 kg m −3, a reduction in hydraulic conductivity, from 8.85×10 −3 to 4.4×10 −3 m s −1, or a decrease in the C-to-N ratio, from 13 to 8, but also they have lower microbial activity, for example 2.84 J g −1 in the reforested soil versus 6.14 J g −1 in the reference soil, in spring, thus presenting a lower productive potential that suggests the use of both amendments and adequate management techniques to ensure a sustainable exploitation, thus avoiding future degradation of soil.