Implementing Continuous Cover Forestry in Planted Forests: Experience with Sitka Spruce (Picea Sitchensis) in the British Isles

William Mason

doi:10.3390/f6040879

Abstract

Planted forests of Sitka spruce, a non-native species from north-west America, are the major forest type in Great Britain and Ireland. Standard management involves even-aged stands, rotations of 40–50 years and a patch clear-felling system with artificial regeneration. However, forest policies support managing these forests for multifunctional objectives with increased diversity of species composition and stand structure. Continuous cover forestry (CCF) is an alternative silvicultural approach used to provide such diversity, but the amount of CCF forest is under 10% of the forest area, and less in Sitka spruce forests; This paper reviews research carried out in the last two decades to support the implementation of CCF in Sitka spruce planted forests; Stand structures and microclimate favouring natural regeneration are understood. Harvesting systems have been adapted for use in CCF stands, a single-tree growth model has been calibrated, comparative costs and revenues have been determined, and operational trials established. The interaction between thinning and wind stability in irregular stands is problematic, together with the lack of suitable species for growing in mixture with Sitka spruce; Introduction of an alternative silvicultural approach may take decades and must overcome technical challenges and cultural resistance.

Highlights

A major land-use change in the British Isles in the previous century was the expansion of the forest area through the establishment of extensive planted forests of non-native conifers in the uplandForests 2015, 6 zones of both Britain and Ireland [1,2]
There are few reports of Continuous cover forestry (CCF) being actively deployed in the management of planted forests of non-native species since these are normally intensively managed for wood production using even-aged management
The results reviewed in this paper illustrate the suite of information requirements and research challenges that need to be overcome if an alternative approach is to be successfully introduced into the management of planted forests, such as those of Sitka spruce in the British Isles

Summary

Introduction

A major land-use change in the British Isles in the previous century was the expansion of the forest area through the establishment of extensive planted forests of non-native conifers in the uplandForests 2015, 6 zones of both Britain and Ireland [1,2]. There was recognition that meeting these multi-functional objectives in planted forests would require a move away from the simple structures and single species stands characteristic of patch clear-felling regimes towards more irregular forests composed of a range of tree sizes and of a mixture of species [9]. Such varied structures are considered to be beneficial for biodiversity [10] and to be preferred by visitors [11]. The implementation of more complex and diversified forests is explicitly supported in forest policy documents in various countries of the British Isles such as Ireland, Scotland and Wales [14,15,16]

Results

Discussion

Conclusion