Modelling natural regeneration of European beech in Saxony, Germany: identifying factors influencing the occurrence and density of regeneration

Abstract

The potential utilisation of natural regeneration of European beech (Fagus sylvatica L.) for forest conversion has received little attention to date. Ecological knowledge is necessary to understand and predict successful natural regeneration of beech. The objective of this study was to improve understanding of what drives the occurrence of beech regeneration and, once regeneration is present, what drives its density. In the study, we utilised a forest inventory dataset provided by Sachsenforst, the state forestry service of Saxony, Germany. The dataset was derived from 8725 permanent plots. Zero-altered negative binomial models (ZANB) with spatial random effects were used to analyse factors influencing occurrence and density simultaneously. The results provided by the spatial ZANB models revealed that the probability of the occurrence of beech regeneration is highly dependent on seed availability, i.e. dependent on source trees in close proximity to a plot. The probability of beech regeneration rises with the increasing diameter of a potential seed tree and decreases with increasing distance to the nearest potential seed source. The occurrence of regeneration is affected by overstorey composition and competition exerted by spruce regeneration. Where sites are affected by groundwater or temporary waterlogging, the impact on the occurrence of regeneration is negative. Although distance to the nearest potential seed source has an influence on occurrence, this variable exerts no influence on density. A high regeneration density arises in conjunction with a high beech basal area in the overstorey. Beech regeneration density, but not occurrence, is negatively affected by browsing intensity. These variables can be used to predict the occurrence and density of beech regeneration in space to a high level of precision. The established statistical tool can be used for decision-making when planning forest conversion using natural regeneration.

How do sapling and adult demography explain beech predominance along environmental gradients in Central European forests?

“…Although the Ellenberg theory is taken as given throughout research to date (e.g., Barna & Bosela, 2015;Mellert et al, 2016;Leuschner, 2020;Cailleret et al, 2020), only some elements of the theory have been confirmed. The predicted pattern of Fagus' predominance under mesic environmental conditions has been supported by numerous descriptions of natural forests (Peters, 1997;Leuschner et al, 2006;Bolte et al, 2007;Axer et al, 2021; but see minor modifications by Leuschner & Ellenberg, 2017b).…”

“…Specifically, studies have shown physiological constraints on Fagus in highly acidic soil conditions (Leuschner et al, 2006;Aertsen et al, 2012), but not in calcareous soils (Ljungström et al, 1990). Also in wet, waterlogged soils, Fagus experiences reduced physiological functioning (Dreyer, 1994;Schmull & Thomas, 2000;Scharnweber et al, 2013;Axer et al, 2021), leading to increased adult mortality (Gorzelak et al, 2000). While Fagus is moderately drought-tolerant (Niinemets & Valladares, 2006;Rötzer et al, 2017;Leuschner, 2020), extreme drought conditions make saplings susceptible to embolism (Tomasella et al, 2019), reduce nitrogen uptake (Fotelli et al, 2001;Geßler et al, 2006;Leuschner, 2020), and inhibit adult growth (Ciais et al, 2005).…”

Optimal Selection of Seed-Trees Using the Multi-Objective NSGA-II Algorithm and a Seed Dispersal Model

“…While our study focuses on a specific stand of Pinus canariensis in Tenerife, the methodology we employed provides a framework applicable to similar forest ecosystems. However, it is crucial to acknowledge the potential effect of other site-specific factors, such as topography, climate, and species traits, on the regeneration success [52][53][54].…”

Modelling natural regeneration of Oak in Saxony, Germany: identifying factors influencing the occurrence and density of regeneration

“…While beech regeneration is less frequent on temporarily waterlogged sites (Axer et al 2021a), no difference between welldrained sites and temporarily waterlogged sites can be demonstrated for oak regeneration (Tab. 1).…”

“…Information obtained from the plots are quadratic mean diameter (d q ), total basal area, tree species-specific basal areas, stand density index (SDI) and a spatially interpolated browsing percentage on rowan. For further information on the inventory design, please refer to Axer et al (2021a). Since seed dispersal also extends the radius of the plot (Kurek & Dobrowolska 2016), remote sensing data were incor-porated to determine distances to the nearest potential seed trees.…”