Soil properties in a hilly area following different harvesting management practices

In this work, the short-term effects of different forestry practices on soil properties were evaluated. A total of 62 pine ( Pinus radiata) plantations from Northern Spain, located in sites with similar climatic conditions on slopes exceeding 35% were studied. In all cases, the soils had similar initial properties and were developed over argillite. The plots studied included mature forest plantations and harvested plots with different management practices for harvesting (stem only or whole tree) and seed-bed preparation (logging slash left on the ground, removal of residues, mixing of horizons or accumulation of soil material from road construction). The study was conducted 5–6 months following harvesting and site preparation and after a period of intense precipitation. In conventionally managed and harvested soils, where the humus layer and abundant logging residues remained on-site, minimal changes in physical and chemical properties were detected. Significant modifications in physical properties and in fertility were evident after whole tree harvesting and intense seed-bed preparation. These practices resulted in increases in bulk density (17%), as well as in decreases in the content of organic matter (65%), total nitrogen (65%), sulphur (39%) and exchangeable calcium (80%) in the upper layer. Decreases in organic matter led to a higher potential for soil erosion. Depletions in effective CEC and exchangeable Mg and K were also found although they were not significant. These alterations were mainly attributed to the mixing of soil layers and soil loss by erosion. Accelerated leaching of nutrient ions may also have occurred because climatic conditions (high moisture and temperature) may favor mineralization, also because of the absence of vegetation, which may have acted as a sink for nutrients. The results of this study showed that, under conditions of the plots studied (high slopes, abundant precipitation and acid, fine textured soils) intense harvesting management affects some soil properties which are important for early growth of later rotations and for conservation of soil and waters.