Successful European beech (Fagus sylvatica L.) regeneration is both of great ecological and economical importance in European forest ecosystems and severely threatened by climate change impacts. To ...increase our knowledge of beech regeneration dynamics under climate change and the potential for controlling it through forest management, we studied interactive effects of solar radiation (PHAR), water and nutrient availability on the height growth of artificially (AR) and naturally regenerated (NR) beech seedlings. The study was conducted in the framework of experimental canopy gaps, under the influence of the 2018/19 drought and heatwaves. We measured PHAR by means of hemispherical photography, approximated water availability based on the inverse of modeled fine root density distributions of overstorey beech (BGRB) and oak (BGRO) and approximated nutrient availability based on soil fertility (SF), derived from forest site mapping. Results indicate that seedling resource availability and resulting growth responses increase with canopy gap size and vary among locations within the gap. Multiplicative non-linear mixed models suggest that AR and NR relative height growth (RI) was best explained by interactive effects of PHAR, BGRB, BGRO and SF, which reflect complementary resource use patterns of beech seedlings. At optimal resource availability, AR reached a potential RI of 174%, which is about 20% higher compared to NR. While the low light growth responses of AR and NR both reflect saturation at 5 to 15% PHAR, depending on individual size and the availability of the remaining resources, NR showed a higher RI than AR at intermediate and high PHAR levels in cases of limited BGR and SF. In contrast to AR, NR growth was affected to a lesser extent by SF and BGRB and not significantly affected by BGRO. These results suggest that overstorey oaks have a lower effect on water availability of beech seedlings than overstorey beeches. Additionally, NR showed higher tolerance to water and nutrient limitation than AR, probably due to better root system development. In conclusion, site-specific potential for mitigating the effects of climate change on beech regeneration through forest management lies in the adaptation of silvicultural systems, i.e., the creation of canopy gaps larger than 200 m2, thus significantly exceeding the average gap size of the natural disturbance regime, and the choice of the regeneration method.
•Beech seedling height growth depends on multiple, interactive resources.•Seedling performance increased over light, water and nutrient availability in gaps.•Natural regeneration showed higher growth rates than artificial regeneration.•Overstorey trees caused species specific water limitation for seedlings (beech>oak).•Larger gaps (>200 m2) may help mitigate climate change threats to beech regeneration.
Silvicultural practices can alter forest genetic resources in unpredictable ways, thereby influencing the adaptive and evolutionary potential of forest populations. This is especially alarming in the ...case of species with more northern distribution centers, due to the lack of area that can be colonized further north. In this article, we studied the genetic diversity of the Scots pine seed tree stand in Poland, its natural regeneration, and two artificially established progeny plantations. The research aimed to determine whether the regeneration mode had affected the efficiency of the gene pool transmission from the maternal seed stand to its offspring. Using nuclear microsatellite markers we compared the parameters of genetic variation and allelic composition among the studied stands. The results showed that all stands represent a common genetic pool with slightly higher values of observed heterozygosity in the case of progeny plantations. Inbreeding was significant only in natural regeneration. All stands have gained and lost rare alleles compared to the maternal seed stand. Nevertheless, the analysis of population differentiation showed that the gene pool of the maternal stand had been transmitted more efficiently to the natural regeneration, though the difference was only minimal. Possible reasons for the differences in transmission efficiency between natural regeneration and artificially established progeny plantations mainly include variations in the number of mother trees and crossing patterns in different reproductive seasons. Furthermore, some individuals that grow in the studied progeny plantations may be natural regeneration of the neighboring stands. In light of the obtained results, we discuss the genetic considerations for establishing and using seeds from progeny plantations in Poland.
We experimentally excluded deer and removed an invasive shrub (Amur honeysuckle) to determine their effects on the survival of planted tree seedlings and the abundance and diversity of natural ...seedlings. The presence of honeysuckle or deer alone resulted in similar declines in the survivorship of planted oak seedlings, but the presence of deer alone resulted in lower survival of planted chestnut seedlings than the presence of honeysuckle alone. While deer and honeysuckle did not affect the abundance or diversity of natural seedlings, the presence of both factors increased the dominance of shade-tolerant, unpalatable, and/or browse tolerant species.
Abstract
Underplanting tree seedlings in areas where natural regeneration is limited may offer a tool by which desired overstory composition can be maintained or restored in forests. However, invasive plant species and ungulate browsing may limit the effectiveness of underplanting, and in-turn, the successful restoration of forest ecosystems. Individually, the invasive shrub Lonicera maackii and browsing by white-tailed deer (Odocoileus virginianus) have been found to negatively affect the regeneration of native tree species in the Midwestern United States, but few studies have examined their interactive or cumulative effects. Using exclosures and shrub removal at five sites, we examined the effects of white-tailed deer and L. maackii both on underplanted seedlings of Castanea dentata and Quercus rubra and on the composition, species richness and diversity of naturally regenerated native tree seedlings. Individually, both deer and L. maackii had negative effects on the survival of underplanted seedlings, but we identified no interactive effects. The presence of L. maackii or deer alone resulted in similar declines in the survivorship of Q. rubra seedlings, but the presence of deer alone resulted in lower survival of C. dentata seedlings than the presence of L. maackii alone. Lonicera maackii reduced light levels, increased seedling moisture stress and decreased relative basal diameter growth for Q. rubra seedlings. Deer reduced the relative growth in height of underplanted C. dentata and Q. rubra seedlings and increased moisture stress of C. dentata seedlings. No effects of L. maackii or deer were found on soil or foliar nitrogen or the overall abundance, species richness and diversity of naturally regenerated seedlings. However, L. maackii and white-tailed deer did affect the abundance of individual tree species, shifting composition of the regeneration layer towards shade tolerant and unpalatable and/or browse tolerant species.
Excessive slash loading could pose a problem for the regeneration of the serotinous lodgpole pine especially in forests at higher elevation where soil temperature is limiting. In the past, these ...forests have commonly been harvested using full-tree harvesting where trees are processed at roadside; however, recently cut-to-length harvesting has become a more frequent harvesting method. In cut-to-length harvesting the harvested trees are processed in the block, as a result slash accumulation is much higher on these cutblocks. In an experimental field trial, the cone distribution, natural lodgepole pine regeneration, and the growth and establishment of planted lodgepole pine were evaluated in response to slash load, drag scarification, and mounding after cut-to-length harvesting of high elevation lodgepole pine stands in the Rocky Mountains. Twelve sites were established, each contained six plots which were randomly assigned to six treatment combinations of two slash removal (slash and slash removed) and three mechanical soil preparation treatments (no soil preparation, drag scarifying, and mounding). The slash removal reduced slash volume by more than 50% but also reduced the number of lodgepole pine cones available for regeneration by over 33%. However, soil mechanical treatments offset this effect as fewer cones were necessary to achieve high natural pine regeneration densities. Drag scarification of plots resulted in 12 times the number of pine seedlings compared to the non-prepared plots. Although slash removal did not have an effect on the number of naturally regenerated lodgepole pine seedlings, it had a positive effect on their growth performance. Conversely, planted pine seedlings had lower mortality and better growth in soils that had been mechanically prepared and had the slash removed; however, the growth effects became only apparent 4 years after planting. While slash removal and mechanical soil preparation did increase soil temperatures; the slash removal treatment had a more transient effect on soil temperatures than soil preparation. Differences in soil temperature decreased over time which appeared to be mostly driven by a warming of the soils in the plots with no soil preparation, likely a result of the decomposition of the finer slash and feathermosses. Overall, it appears that surface disturbance on these high elevation sites had a far greater effect on lodgepole pine regeneration and growth than the increased accumulation of slash as a result of cut-to-length harvesting.
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