Effects of gap size and soil chemical properties on the natural regeneration in black pine (Pinus nigra Arn.) stands.

摘要

This paper deals with the problem of black pine (Pinus nigra Arn.) stand re-naturalization in the Apennines of Central Italy. Gap cuttings of two different sizes (gap diameter (D) to stand height (H) ratios were 0.75 and 1.0) in age class stands (50 and 90 years old) have been carried out, studying the soil properties and the tree regeneration dynamics in the different gaps 7 years after the beginning of the experiment. The small gaps D:H=0.75 had the greater concentrations of total phenols, polyphenols and fulvic acids. In contrast, a greater amount of humic acids was detected in the medium gaps D:H=1. Results indicate that black pine was the best regenerated species in gaps with D:H=1 and its presence was increasing. Some broadleaves, pubescent oak (Quercus pubescens) and holm oak (Quercus ilex) particularly and hop-hornbeam (Ostrya carpinifolia) and manna-ash (Fraxinus ornus) in a subordinate way, were also present in the gaps. These results confirm that the gap cutting system represents an effective tool for the natural regeneration priming and a treatment with low environmental impact which provides suitable condition for the re-naturalization of the conifer monocultures.