Success factors for high-quality oak forest (Quercus robur, Q. petraea) regeneration

Abstract

Background: Within the framework of close-to-nature forestry, oak forest (Quercus robur, Q. petraea) regeneration techniques that consider both silvicultural and nature conservation demands have become a very important issue. While there are many experimental and local studies that aim at disentangling the relationships between different environmental and silvicultural factors and the success of oak regeneration, systematic supra-regional studies at the greater landscape level are missing so far. Against this background, the first objective (a) of this study was to present an efficient and sufficiently accurate sampling scheme for supra-regional forest regrowth inventories, which we applied to young oaks stands. The second, and major, objective (b) was to identify the crucial success factors for high-quality oak forest regeneration in northwest Germany. Results: Objective (a): Factors that have been identified as potentially crucial for the success or failure of oak regeneration were either included in a field inventory procedure or extracted from forest inventory databases. We found that the collected data were suitable to be analyzed in a three-step success model, which was aimed at identifying the crucial success factors for high-quality oak forest regeneration. Objective (b): Our modeling procedure, which included a Bayesian estimation approach with spike-and-slab priors, revealed that competitive pressure from the secondary tree species was the most decisive success factor; no competition, or low competition by secondary tree species appeared to be particularly beneficial for the success of high-quality oak regeneration. Also fencing and the absence of competitive vegetation (weeds, grass, bracken) seemed to be beneficial factors for the success of oak regeneration. Conclusions: Trusting in biological automation was found to be mostly useless regarding economically viable oak forest regeneration. To efficiently organize oak regeneration planning and silvicultural decision-making within a forest enterprise, it is strongly recommended to initially evaluate the annual financial and personnel capacities for carrying out young growth tending or pre-commercial thinning and only then to decide on the extent of regenerated oak stands. Careful and adaptive regeneration planning is also indispensable to secure the long-term ecological continuity in oak forests. Oak regeneration should therefore preferably take place within the close vicinity of old oak stands or directly in them. The retention of habitat trees is urgently advised.

On the knowns and unknowns of natural regeneration of silviculturally managed sessile oak (Quercus petraea (Matt.) Liebl.) forests—a literature review

“…This number of publications appears to be rather low, but the majority of studies were limited to a single or only very few different site types, respectively. Only five studies systematically integrated site quality into the experimental design (Annighöfer et al 2015;Bilke 2004;Götmark et al 2011;Ligot 2014;Mölder et al 2019b). Thus, we cannot draw general conclusions about the effect of site conditions based on the available literature.…”

“…Only a small proportion of oak forests in Central Europe is of natural origin. For example, a recent study found that about 90% of a large sample of nearly 300 young oak stands assessed in Central and north-western Germany were established by artificial regeneration such as planting or seeding (Mölder et al 2019b). Natural regeneration of oak is more common in France and Belgium (e.g.…”

“…In summary, it appears that a number of factors have a critical influence on the success or failure of silvicultural approaches to regenerate Q. petraea naturally (e.g. Mölder et al 2019b;Watt 1919). These factors include prevailing site conditions, microclimate including late frost and light availability, competition by accompanying vegetation and browsing pressure.…”

Regeneration Dynamics and Development of Seedlings in Sessile Oak Forests in Relation to the Light Availability and Competing Vegetation

“…In addition to microclimatic conditions, the competition from woody species and ground vegetation significantly affects the initial development of seedlings and the dynamics of regeneration of sessile oak forests. The degree of competition in the medium and long term can hinder the process of natural regeneration of sessile oak forests and is often identified as one of the main reasons for the death of sessile oak seedlings [2,4,32,33]. In the area of Serbia in Southeast Europe, hornbeam (Carpinus betulus L.), white linden (Tilia tomentosa L.), and common ash (Fraxinus excelsior L.) are the strongest competitors among woody species in the process of natural regeneration of sessile oak forests in moist habitats, while it is manna ash (Fraxinus ornus L.) in drier habitats.…”

Environmental and anthropogenic factors affecting natural regeneration of degraded dry Afromontane forest

“…Still, studies that have evaluated the effects of environmental conditions and human disturbance on natural regeneration are rare, despite their importance for informing forest restoration and sustainable management. Most of the available studies are either focused on a specific tree species and/or gradient (Ceccon et al 2006; Cierjacks et al 2008; Plieninger et al 2010; Mölder et al 2019) or on a human disturbance at the landscape level (Zamorano‐Elgueta et al 2014). An exception to this is the work of Bose et al (2016).…”