Comparison of different site preparation techniques: quality of planting spots, seedling growth and pine weevil damage

Kristina Wallertz,Lars-Göran Sundblad,Magnus Petersson,Niklas Björklund,Karin Hjelm

doi:10.1007/s11056-018-9634-8

Kristina Wallertz, Lars-Göran Sundblad + Show 3 more

Open Access

https://doi.org/10.1007/s11056-018-9634-8

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Abstract

In northern Europe, there are high risks of severe pine weevil (Hylobius abietis) damage to newly planted conifer seedlings. Site preparation is one of the most important measures for reducing these risks and as several studies have shown the damage is highly dependent on the amount of pure mineral soil around the seedlings. We investigated effects of three site preparation techniques: (1) disc trenching with a conventional Bracke T26, (2) MidiFlex unit and (3) soil inversion with a Karl Oskar unit on characteristics of the planting spots, growth and pine weevil damage and survival rates of untreated and insecticide treated planted Norway spruce (Picea abies) seedlings. All three site preparation techniques reduced pine weevil damage in comparison with no site preparation, and the proportion of spots with pure mineral soil they created was inversely related to the rate of mortality caused by pine weevil. The results indicate that the quality of the planting spots depends on the technique used. In areas where pine weevil is the major threat to seedling survival, the amount of mineral soil in the planting spots is the most important factor in order to protect the seedling from damage. Without site preparation most planting spots consisted of undisturbed humus. Generally, the Karl-Oskar created the most spots with pure mineral soil, but on very stony soils the Bracke T26 created more mineral soil spots than other methods. Site preparation is a valuable tool in order to improve survival in regeneration areas and it is of great importance to make the right choice of technique depending on the particular circumstances on the actual site.

Highlights

The management of vegetation competition in forests is an integral part of silvicultural practices in many parts of the world (Wagner et al 2006; Richardson et al 2006; Newton 2006)
Various site preparation techniques have different ability to achieve high quality planting spots and it varies with conditions on the site
After preparation using a Bracke T26, most of the planting spots were defined as tracks or patches, regardless of soil moisture class

Summary

Introduction

The management of vegetation competition in forests is an integral part of silvicultural practices in many parts of the world (Wagner et al 2006; Richardson et al 2006; Newton 2006). Several studies have shown that site preparation methods can reduce the damage caused by pine weevils (Lekander and Söderström 1969; von Sydow 1997; Örlander and Nilsson 1999; Sutton; 1993), especially if they result in planted seedlings being surrounded by pure mineral soil (Lindström et al 1986; Björklund et al 2003; Petersson and Örlander 2003; Petersson et al 2005). Pine weevils seem to avoid areas of mineral soil by increasing their speed and moving straighter This reduces the time they remain on the patch resulting in less feeding on those seedlings compared to seedlings planted in humus (Kindvall et al 2000)

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