Genetic variability of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst.) natural regeneration compared with their maternal stands

Abstract

Abstract:The genetic variability and biodiversity of tree populations ensure the stability and sustainability of forest ecosystems. New research tools based on molecular DNA markers enable precise characterisation of forest genetic resources, i.e. detection of different allele frequencies in mature trees and progeny populations. The paper describes the genetic structure of mature stands of Scots pine (Pinus sylvestris L.) in Oława Forest District and Norway spruce (Picea abies L. Karst.) in Jawor Forest District and stands of their respective progeny.In the Scots pine stand, there was a slight increase (0.6%) in heterozygosity level and a larger increase (4.9%) in the inbreeding coefficient of progeny trees. In the Norway spruce stand, despite a small reduction (0.9%) in heterozygosity, a similar increase (4.6%) in the inbreeding coefficient of progeny was revealed. In both stands, allele richness and the partition probability of basic clustering were high. Both pine and spruce adults and progeny trees were characterised by high levels of genetic similarity (96% and 79%, respectively). Gene flow between the mature and progeny populations was high (N m > 1) for both Scots pine and Norway spruce.Conservation of the gene pool within forest tree stands requires an increase in the proportion of natural regeneration. To estimate the extent to which genes are transmitted between adult trees and their progeny, more studies are needed, especially taking into account the influence of silviculture measures, like selective tree cutting, on the genetic variability of the younger generation.These results confirm that the gene pool was conserved when transmitted between the stands studied, as well as highlight the usefulness of such a study for silvicultural purposes.

Genetic Diversity and Its Spatial Distribution in Self-Regenerating Norway Spruce and Scots Pine Stands

“…Higher genetic diversity in the regeneration indicates that recombination and gene flow from not sampled more distant sources might have outweighed the loss of genetic diversity that has possibly occurred in the investigated sites (i.e., putative maternal stands) due to natural selection during ontogenesis. Similar results were obtained in studies of natural regeneration of Scots pine [30,31] and Norway spruce [31] growing in forest understory. Higher genetic diversity in progenies of various tree species has also been found in other studies [19,20], yet this diversity tended to decrease over time probably because of natural selection [35][36][37].…”

“…The detected high genetic diversity within the studied populations of Norway spruce and Scots pine regardless of the tree age (generation gaps) was of similar level as has been reported in other genetic studies of European populations of these species (e.g., [3][4][5]31,40,66,67]). …”

“…Higher genetic diversity in progenies of various tree species has also been found in other studies [19,20], yet this diversity tended to decrease over time probably because of natural selection [35][36][37]. The regenerating Scots pine seedlings retained the same (Swedish study by Yazdani et al [30]) or a slightly increased level of expected heterozygosity (Polish study by Nowakowska et al [31]) as compared to maternal trees. In a Norway spruce stand, despite a small reduction (0.9%) in heterozygosity, Nowakowska et al [31] found a similar increase (4.6%) in the inbreeding coefficient of the progeny.…”

“…The regenerating Scots pine seedlings retained the same (Swedish study by Yazdani et al [30]) or a slightly increased level of expected heterozygosity (Polish study by Nowakowska et al [31]) as compared to maternal trees. In a Norway spruce stand, despite a small reduction (0.9%) in heterozygosity, Nowakowska et al [31] found a similar increase (4.6%) in the inbreeding coefficient of the progeny. In our study, the observed deviations from the Hardy-Weinberg equilibrium in regenerating juveniles and the lack of homozygosity in both tree species investigated herein might be the result of natural selection during species establishment in disturbed environments, or this might be related to the specific sampling scheme applied (juveniles sampled in compact circular plots).…”

“…Genetic monitoring which has been defined as "tracking of temporal changes in the genetic variation and structure of tree populations" is the only way to verify how well genetic diversity is maintained over time, and how this diversity is affected by climate change and forest management practices [23]. According to Fussi et al [26], there is a lack of experience regarding the evaluation of potential changes between assessments of genetic parameters (repeated genetic analysis of the same population in certain time intervals), although some ideas have been postulated, including the comparison to reference stands [27], interpretation of time series of genetic data [28], and comparison of different generations within stands [29][30][31].…”