Effect of Topping Trees on Biomass and Nitrogen Removal in the Thinning of Norway Spruce Stands

Christoph Huber,Maximilian Kastner,Karl Stampfer,Eduard Hochbichler

doi:10.3390/su9101856

Christoph Huber, Maximilian Kastner + Show 2 more

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https://doi.org/10.3390/su9101856

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Abstract

In Central Europe, full-tree (FT) harvesting is an increasingly common harvesting method in steep terrain harvesting due to the increased use of highly economical processor tower yarders. In conventional FT harvesting, nutrient removal from harvest sites is substantially higher than in cut-to-length (CTL) harvesting due to the extraction of nutrient-rich branches and foliage. One strategy to reduce the adverse impact of FT harvesting is to cut off the tops of felled trees prior to extraction (topping). The purpose of this study was to assess the effect of implementing topping treatments in FT harvesting on biomass and nutrient removal. The effect of conventional FT harvesting on the amount of logging residues left on the site was assessed in three different Norway spruce (Picea abies)-dominated stands following cable yarding operations by collecting logging residues from the forest floor. The additional effect of topping trees on the amount of logging residues was assessed by using biomass models. These models were created based on the data of 25 sample trees, which were felled and sampled destructively within the stands. The results show that conventional FT harvesting considerably increases nutrient removal in comparison to CTL, but still do not remove all nutrients from the sites. After conventional FT harvesting, 5–18% of the nutrients remained on the sites. Topping trees at a diameter of 8 cm substantially increased the amount of remaining nutrients to 30–34%.

Highlights

In Central Europe, full-tree (FT) harvesting, which involves the removal of most of the nutrient-rich components of a tree from the harvesting site, has become more common in steep terrain harvesting
The effect of conventional FT harvesting on the amount of logging residues left on the site was assessed in three different Norway spruce (Picea abies)-dominated stands following cable yarding operations by collecting logging residues from the forest floor
The results show that conventional FT harvesting considerably increases nutrient removal in comparison to CTL, but still do not remove all nutrients from the sites

Summary

Introduction

In Central Europe, full-tree (FT) harvesting, which involves the removal of most of the nutrient-rich components of a tree from the harvesting site, has become more common in steep terrain harvesting. The main reason for the popularity of FT cable yarding is the development of so-called “processor tower yarders” in the late 1970s, which are equipped with boom-mounted processors The use of these yarders resulted in cost-savings of about 40% for FT harvesting [1]. Processor tower yarders working with FT harvesting represent the state-of-the-art technology in steep terrain harvesting [1] and have largely replaced motor-manual cut-to-length (CTL) systems, where trees are delimbed and crosscut with chainsaws within the forest stands. Another reason for the increased use of FT harvesting was the steadily growing interest in producing bioenergy from renewable resources [2]. The procurement costs of this material for further use is reduced because material collection and piling in the field is not necessary

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