Regeneration Dynamics Following the Formation of Understory Gaps in a Slovakian Beech Virgin Forest

Abstract

The frequency and size of canopy gaps largely determine light transmission to lower canopy strata, controlling structuring processes in the understory. However, quantitative data from temperate virgin forests on the structure of regeneration in gaps and its dynamics over time are scarce. We studied the structure and height growth of tree regeneration by means of sapling density, shoot length growth and cumulative biomass in 17 understory gaps (29 to 931 m2 in size) in a Slovakian beech (Fagus sylvatica L.) virgin forest, and compared the gaps with the regeneration under closed-canopy conditions. Spatial differences in regeneration structure and growth rate within a gap and in the gap periphery were analyzed for their dependence on the relative intensities of direct and diffuse radiation (high vs. low). We tested the hypotheses that (i) the density and cumulative biomass of saplings are higher in gaps than in closed-canopy patches, (ii) the position in a gap influences the density and height growth of saplings, and (iii) height growth of saplings increases with gap size. Sapling density and biomass were significantly higher in understory gaps than under closed canopy. Density of saplings was positively affected by comparatively high direct, but low diffuse radiation, resulting in pronounced spatial differences. In contrast, sapling shoot length growth was positively affected by higher levels of diffuse radiation and also depended on sapling size, while direct radiation intensity was not influential. Conclusively, in this forest, regeneration likely becomes suppressed after a short period by lateral canopy expansion in small gaps (<100 m2), resulting in a heterogeneous understory structure. In larger gaps (≥100 m2) saplings may be capable even at low plant densities to fill the gap, often forming a cohort-like regeneration layer. Thus, gaps of different sizes imprint on the resulting canopy structure in different ways, enhancing spatial heterogeneity.

Effects of Gap Size and Cardinal Directions on Natural Regeneration, Growth Dynamics of Trees outside the Gaps and Soil Properties in European Beech Forests of Southern Italy

“…Mountford et al [86], in a managed beechwood in southern England, and Gálhidy et al [87], in a temperate deciduous forest found more prolific beech regeneration in small and medium gaps. Our results are also consistent with previous studies [32,88], reporting that European beech grew optimally in gap openings minor than 500 m 2 . In short, our result highlighted that in the small and medium gaps, the combination of moderate levels of diffuse light and relatively low levels of direct light created more favorable conditions in soil moisture and nutrients, particularly for nitrogen and potassium whose presence is important for beech natural regeneration (species shade tolerant), confirming previous observations of other authors [58,89,90].…”

Impact of Canopy Gap Ecology on the Diversity and Dynamics of Natural Regeneration in a Tropical Moist Semi-Deciduous Forest, Ghana

“…Non-pioneer light demanding (NPLD) recorded the highest number of 38 species, followed by pioneers with 30 species, whereas shade-tolerant attained the lowest representatives of 17 species in regenerated species composition. This finding supports the long-standing notion that light-tolerant species prefer open space environments for optimum regeneration [5] while those environments normally impede regeneration of shadeadapted species [2]. Pioneers-Terminalia superba (frequency, regeneration density, relative density = 97, 774 trees/ha, 6.61%) and Daniella ogea (85, 678 trees/ha, 5.79%), NPLD-Mansonia altissima (75, 598 trees/ha, 5.11%), and Blighia sapida (70, 558 trees/ha, 4.77%), and shade-tolerant-Nesogordonia papaverifer (340, 2711 trees/ha, 23.16%), Celtis mildbraedii (188, 1499 trees/ha, 12.81%) and Baphia nitida (185, 1475 trees/ha, 12.60%) were the predominant tree species found almost in all gaps.…”

“…Generally, canopy gaps influence forest regeneration cycles by offering local resource-rich niches for understory tree species [1]. Differences among tree species in establishment, germination, development, survival, growth, and canopy recruitment within gap sites explain the crucial role of canopy gaps in shaping forest composition [1,2]. This very important role of canopy gaps had been well documented in numerous gap regeneration studies conducted in temperate [3] and tropical [4] forest ecosystems.…”

Logging effects on seedling regeneration and diversity in a tropical moist semi-deciduous forest in Ghana

“…This positive trend has already been confirmed by Olson and Wagner (2011), who attributed resource availability (i.e., light) in the disturbed environment as the major factor responsible for seedling regeneration. According to Feldmann et al (2020), light transmission to the lower strata influences structuring processes, including seedling regeneration. Logging creates a heterogeneous canopy with different microenvironments that differ in light intensity and different degrees of soil disturbance, advantageous for seedling regeneration (Duah-Gyamfi et al, 2014).…”