Gap based silviculture permits to avoid both the environmental degradation associated with large clearcuts and the limited productivity associated with single-tree selection. As gap opening leads to a progressive modification of the factors on which additional root cohesion depends on, root density, size distribution and tensile strength, it is of great relevance to know the dynamics of root features following gap opening in forest stands. In this paper the results of trials carried out in Silver fir-Norway spruce mixed stands in the Italian Central Alps subjected to gap silviculture are presented. Two sites where gap cuttings have been introduced in the last decade in place of single tree selection cutting, were selected. At each site, two stands, undisturbed and disturbed, were located and monitored for four years for root density, size distribution and tensile strength, as well as natural regeneration of forest species to estimate the changes in the root strength induced by gap opening. Four years after cutting, the abundance of natural regeneration inside the gap differed at the two sites, varying from 3.59 to 0.49 seedling m-2. Tensile strength of roots sampled after tree cutting, in terms of rupture force, was proven to be related to root diameter by a power law relationship as in the case of live roots, although the force values showed an increasing spread with time from cutting as consequence of the contemporary presence of decomposed and healthy roots. In the considered cases root decay did not affect root strength for the first two years, whereas the reduction became significant at the second and the third year in the two cases. Root density reduction, became important three years after cutting, even if concerned only fine roots. The root degradation process due to bacteria and fungi, actually, is not uniform, and root degradation has been showed to decrease more rapidly in the shallower layer and for thinner roots, accordingly to literature on decay studies. The additional root cohesion, being a combination of root strength and root diameter distribution, starts to reduce as a consequence of root degradation between two and three years after cutting. As variability in root distribution in the stands is high and hides the effect of the degradation especially in the first year after cutting, future studies should consider the spatial root distribution as a function of the distance from the stem and the diameter of the stem.
Effect of gap opening on soil reinforcement in conifer stands in the Central Alps
MINOTTA, Gianfranco;
2015-01-01
Abstract
Gap based silviculture permits to avoid both the environmental degradation associated with large clearcuts and the limited productivity associated with single-tree selection. As gap opening leads to a progressive modification of the factors on which additional root cohesion depends on, root density, size distribution and tensile strength, it is of great relevance to know the dynamics of root features following gap opening in forest stands. In this paper the results of trials carried out in Silver fir-Norway spruce mixed stands in the Italian Central Alps subjected to gap silviculture are presented. Two sites where gap cuttings have been introduced in the last decade in place of single tree selection cutting, were selected. At each site, two stands, undisturbed and disturbed, were located and monitored for four years for root density, size distribution and tensile strength, as well as natural regeneration of forest species to estimate the changes in the root strength induced by gap opening. Four years after cutting, the abundance of natural regeneration inside the gap differed at the two sites, varying from 3.59 to 0.49 seedling m-2. Tensile strength of roots sampled after tree cutting, in terms of rupture force, was proven to be related to root diameter by a power law relationship as in the case of live roots, although the force values showed an increasing spread with time from cutting as consequence of the contemporary presence of decomposed and healthy roots. In the considered cases root decay did not affect root strength for the first two years, whereas the reduction became significant at the second and the third year in the two cases. Root density reduction, became important three years after cutting, even if concerned only fine roots. The root degradation process due to bacteria and fungi, actually, is not uniform, and root degradation has been showed to decrease more rapidly in the shallower layer and for thinner roots, accordingly to literature on decay studies. The additional root cohesion, being a combination of root strength and root diameter distribution, starts to reduce as a consequence of root degradation between two and three years after cutting. As variability in root distribution in the stands is high and hides the effect of the degradation especially in the first year after cutting, future studies should consider the spatial root distribution as a function of the distance from the stem and the diameter of the stem.
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