Biochemical properties of acid soils under climax vegetation (Atlantic oakwood) in an area of the European temperate-humid zone (Galicia, NW Spain): specific parameters

The general and specific biochemical parameters of soils are highly sensitive to disturbance of the environment, but their use for diagnosis of soil degradation is limited by lack of comparable published data and lack of accepted methodological standards. With a view to establishing an appropriate data base for the soils of Galicia (NW Spain), we investigated the biochemical properties of O and Ah horizons of 40 native Umbrisols under climax Atlantic oakwood in this region. We report here our results on specific biochemical parameters (i.e. extracellular hydrolytic enzyme activities) characterizing the phosphorus, nitrogen, carbon and sulphur cycles. The enzymes studied were phosphomonoesterase (23.51 +/- 10.37 and 6.62 +/- 3.29 micromol p-nitrophenol g-1 h-1, values for O and Ah horizons, respectively), phosphodiesterase (3.60 +/- 1.95 and 0.96 +/- 0.51 micromol p-nitrophenol g-1 h-1), casein-protease (2.97 +/- 0.83 and 0.94 +/- 0.32 micromol tyrosine g-1 h-1), BAA-protease (23.74 +/- 11.35 and 15.26 + 8.91 micromol NH3 g-1 h-1), urease (24.90 +/- 13.60 and 16.59 +/- 10.61 micromol NH3 g-1 h-1), CM-cellulase (0.59 +/- 0.17 and 0.23 +/- 0.10 micromol glucose g-1 h-1), invertase (12.66 +/- 2.75 and 6.93 +/- 2.14 micromol glucose g-1 h-1), beta-glucosidase (8.43 +/- 5.14 and 1.55 +/- 0.89 micromol p-nitrophenol g-1 h-1), and arylsulfatase (0.67 +/- 0.30 and 0.46 +/- 0.20 micromol p-nitrophenol g-1 h-1). For the variables for which comparable data are available, the values observed are generally within previously published ranges. Principal components analysis of the combined biochemical, physical and chemical data for these soils shows five factors, of which the three most important concern microbial activity and its logical dependence on nutrient content, the accumulation of soil organic matter and the mineralization of soil organic matter.