Abstract
In temperate Europe, oak-dominated forests are widespread, supporting high biodiversity and providing important ecosystem services. Insufficient natural regeneration has, however, been a concern for over a century. The objective of this study was to gain insights into differences in regeneration success using artificial and natural regeneration techniques for reforestation of oak (Quercus robur L.) stands. We monitored seedlings following planting, direct seeding and natural regeneration over five years in a randomized block experiment in southern Sweden with fenced and non-fenced plots. Fencing had a strong positive effect on height growth, especially for planted seedlings that were taller than the other seedlings and more frequently browsed in non-fenced plots. In contrast, there was little effect of fencing on survival, establishment rate and recruitment rate of seedlings. Due to aboveground damage on seedlings from voles, protection of acorns did not improve establishment rate following direct seeding. Under current circumstances at the site with a sparse shelterwood of old oaks, we conclude that natural regeneration was the most cost-efficient regeneration method. It resulted in the most seedlings at the lowest cost. However, regeneration success was heavily influenced by interference from herbaceous vegetation. With a small additional investment in vegetation control, the results might have been improved for planting and direct seeding.
Highlights
Pedunculate and sessile oak (Quercus robur L. and Q. petraea (Matt.) Liebl.) are foundational species in European temperate forests where they support more biodiversity than most other tree species (Mölder et al 2019; Sundberg et al 2019)
Since there were different ages and origins of seedlings in the four regeneration techniques, we evaluated the effect of fencing on height separately for each technique (PL, natural regeneration (NR), direct seeding (DS) − P and DS + P) using linear mixed models
We studied the combined effect of the fencing and of the regeneration technique on the relative growth rate (RGR) with a linear mixed model
Summary
Pedunculate and sessile oak (Quercus robur L. and Q. petraea (Matt.) Liebl.) are foundational species in European temperate forests where they support more biodiversity than most other tree species (Mölder et al 2019; Sundberg et al 2019). Insufficient natural regeneration of oak has been a concern for over a century (Watt 1919; Korstian 1927). It is well-known that pedunculate and sessile oak are light-demanding species (Röhrig et al 2006; Ligot et al 2013; Leuschner and Ellenberg 2018; Kohler et al 2020). Their regeneration depends on relatively open forests, forest edges or savanna-like grasslands with
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