Abstract
The effects of stand age, site index and parent material on soil biochemical properties related to biomass (extractable C, microbial C and metabolic quotient) were examined in the 0-15 cm mineral soil layers of Pinus pinaster and Pinus sylvestris stands from NW Spain. Two productivity levels (low and high site index), two ages (young and old) and two parent soil materials (granite and acid schists) were considered. The data indicated that there were differences in microbial parameters in soils under different species. In general in P. pinaster forest higher values of biochemical parameters, expressed on organic C basis, were observed in the stands of high site index as compared with the low ones; in contrast, in P. sylvestris no differences among stand site index were detected. In both species different results were also observed depending on parent material and a significant effect of stand age was detected for extractable C and microbial C in P. pinaster forest developed over granite. The data seem to indicate that measured parameters may have the potential to be used as indicators of the effect of forest management on soil organic matter quality.
Highlights
Forest soils play an important role in sustaining stand productivity and forest values by regulating water uptake, root environment and nutrient cycling; a judicious management of soils forms an important component of sustainable forest management (Khanna and Madeira, 2002)
For the matrix of Pinus pinaster data, the analysis of variance (ANOVA 3) showed a significant effect of parent material, stand age and site index on extractable C values expressed as absolute values, which explained 12, 7 and 10% of variance, respectively (Table 3); these factors were not independent as indicated by the significant effect of all the possible interactions among them
Our results showed that in the P. pinaster forest developed on granite, microbial biomass and extractable C values were significantly higher in soils from stands with high site index than those with low site index
Summary
Forest soils play an important role in sustaining stand productivity and forest values by regulating water uptake, root environment and nutrient cycling; a judicious management of soils forms an important component of sustainable forest management (Khanna and Madeira, 2002). Since microorganisms reflect soil environment, the microbial component and, the ratio of microbial C and N to total organic C and N have been considered to be the most promising early indicators for monitoring changes in soil quality due to land use and management effects before changes in total soil C and N can be detected (Sparling, 1998). Knowledge about soil microorganisms and soil biological processes may improve the scientific basis of forest management decisions, e.g. on the types of species for planting in the area. On this premise, it is surprising to note the scarcity of studies on soil microbial parameters in relation to forest management and productivity
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