Influence of forest cover and herbaceous vegetation on the microbiological and biochemical properties of soil under Mediterranean humid climate

The effects of different Mediterranean vegetation cover on the biological and biochemical quality of soil is not well understood. The aim of this work is to evaluate the effects that different types of vegetation (forestry plots, mainly dominated by Spanish black pine (Pinus nigra Arn. ssp salzmannii) and herbaceous plots, where overstorey density is lower and natural herbaceous percentage is higher than in forestry plots) have in the biological properties of soil in Mediterranean humid climate. The impact of these plant communities on the biological soil quality was determined by several sensitive parameters related to the microbial activity of the soil such as soil respiration and some enzyme activities (urease, phosphatase and dehydrogenase). Development of vegetation (herbaceous and pines) was also determined and correlated with microbiological and biochemical indicators. Organic matter content in herbaceous sites was significantly higher than in forestry sites, ranging from 5.27 to 6.70 g 100 g−1 in herbaceous sites to 1.64-2.81 g 100 g−1 in forested areas. Herbaceous sites showed higher values of basal respiration and dehydrogenase activity than pine areas. However, the decrease of organic carbon content in pine areas led microbial activity enrichment per unit of carbon. These results conclude that vegetation cover significantly impacts soil microbial processes in Mediterranean humid climates, herbaceous vegetation having a more positive influence than forest vegetation on the biochemical and microbial activity of the soil, principally due to the higher accumulation of organic matter from plant remains.