Influence of soil compaction on the growth of silver fir (Abies alba Mill.) under a forest canopy

In the study, the influence of soil compaction on the growth of silver fir seedlings (Abies alba Mill.) was evaluated; the soil compaction being measured using a cone penetrometer. The studies were conducted under a forest canopy, where the exploratory units with different soil compactions exerting a unit pressure of 50, 100, 150, 200, and 250 kPa, as well as the control units (without pressure), were prepared. Selected units were sown with seeds of silver fir, and from the remaining units, the soil samples were collected and their compaction measured using a cone penetrometer. After 5 months, the seedlings were collected and their growth analyzed. Increasing the unit pressure resulted in soil compaction characterized by the compaction in the layer up to 15 cm, in which the roots of the growing seedlings were found. Different variants of the pressure significantly affected the analyzed parameters of seedlings. Negative and statistically significant correlation was reported between increasing compaction of the soil, the length of the primary root, and the total length of seedlings (-0.46 and -0.35, respectively), while the positive correlation was found for the length of the stem (+0.32). Similarly, there was a statistically significant negative correlation between the increased soil compaction and the dry weight of the root system (-0.29), and positive correlation in the case of the stem dry weight (0.26). Increasing soil compaction, however, did not affect significantly the size of assimilation apparatus