Manipulating overstory density and mineral soil exposure for optimal natural regeneration of Scots pine

In northern boreal region the growth of forests is slow, and yield and profit are low, which is why low refor-estation costs are important for profitable forestry. If natural regeneration is successful, expensive artificial forest regeneration (planting or direct seeding) can be avoided. In this study, we look at the impact of overstory density and site preparation on natural regeneration and seedling growth of Scots pine. Study stands were established in different parts of Northern Finland and in each stand following treatments: 50, 150 and 250 trees ha-1 or unthinned control, where the stand density was >= 250 trees ha-1, were randomly allocated to experimental plots. In addition, site preparation (disc trenching, 4000-5000 m ha-1) was carried out on two experimental plots in which tree density was either 50 or 150 trees ha-1. In the experimental stands seedling number, age and growth were monitored for 11 years. Monitoring revealed that the number of seedlings increased with decreasing tree density. Average seedling height growth was very low or even non-existent in the unthinned control and in the densest (250 trees ha-1) treatment, but increased when the density of trees decreased. The highest seedling number and the highest growth were achieved when the tree density was 50 trees ha-1 and the soil was prepared to expose mineral soil. Achieving e.g. 2000 seedlings ha-1, would need about 40% exposition of mineral soil. The required low tree density implies that not only seed supply from seed trees and site preparation is important for regeneration success in northern boreal Scots pine forests but also the reduction of competition by mature trees

Effects of site preparation and reindeer grazing on the early-stage success of Scots pine regeneration from seeds in northern Finland and Sweden

The importance of sufficient soil scarification to ensure the regeneration of Scots pine on sub-dry and more fertile sites has been emphasized in many studies. Here we aimed to study, how site preparation intensity affects the early success of natural regeneration and sowing (bare seeds and seed pellets) of Scots pine with or without the reindeer grazing. The study area was located in northern Finland and Sweden where five site preparation methods were compared: unprepared control, logging machine tracks, Huminmix (mixing the mineral soil and organic layer), disc trenching and intensive disc trenching. In each of these we used direct seeding, seed pellets and natural regeneration. Results revealed that even the lightest site preparation methods can provide sufficient regeneration results while the reindeer grazing limits the optimal regeneration result. Huminmix and even the track of the logging machine could provide satisfactory regeneration results both in direct seeding and natural regeneration. This could facilitate the coexistence of forest management, reindeer herding and other land use forms in the same stands and area. The use of seed pellets needs further research, but it may have potential due to lower consumption of seeds and less need for site preparation

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peerReviewe

Manipulating overstory density and mineral soil exposure for optimal natural regeneration of Scots pine

In northern boreal region the growth of forests is slow, and yield and profit are low, which is why low refor-estation costs are important for profitable forestry. If natural regeneration is successful, expensive artificial forest regeneration (planting or direct seeding) can be avoided. In this study, we look at the impact of overstory density and site preparation on natural regeneration and seedling growth of Scots pine. Study stands were established in different parts of Northern Finland and in each stand following treatments: 50, 150 and 250 trees ha-1 or unthinned control, where the stand density was >= 250 trees ha-1, were randomly allocated to experimental plots. In addition, site preparation (disc trenching, 4000-5000 m ha-1) was carried out on two experimental plots in which tree density was either 50 or 150 trees ha-1. In the experimental stands seedling number, age and growth were monitored for 11 years. Monitoring revealed that the number of seedlings increased with decreasing tree density. Average seedling height growth was very low or even non-existent in the unthinned control and in the densest (250 trees ha-1) treatment, but increased when the density of trees decreased. The highest seedling number and the highest growth were achieved when the tree density was 50 trees ha-1 and the soil was prepared to expose mineral soil. Achieving e.g. 2000 seedlings ha-1, would need about 40% exposition of mineral soil. The required low tree density implies that not only seed supply from seed trees and site preparation is important for regeneration success in northern boreal Scots pine forests but also the reduction of competition by mature trees.Peer reviewe

Genetic effects on the timing of parturition and links to fetal birth weight

The timing of parturition is crucial for neonatal survival and infant health. Yet, its genetic basis remains largely unresolved. We present a maternal genome-wide meta-analysis of gestational duration (n = 195,555), identifying 22 associated loci (24 independent variants) and an enrichment in genes differentially expressed during labor. A meta-analysis of preterm delivery (18,797 cases, 260,246 controls) revealed six associated loci and large genetic similarities with gestational duration. Analysis of the parental transmitted and nontransmitted alleles (n = 136,833) shows that 15 of the gestational duration genetic variants act through the maternal genome, whereas 7 act both through the maternal and fetal genomes and 2 act only via the fetal genome. Finally, the maternal effects on gestational duration show signs of antagonistic pleiotropy with the fetal effects on birth weight: maternal alleles that increase gestational duration have negative fetal effects on birth weight. The present study provides insights into the genetic effects on the timing of parturition and the complex maternal-fetal relationship between gestational duration and birth weight.Maternal genome-wide analyses identify variants associated with gestational duration and preterm delivery. Maternal alleles positively associated with gestational duration exhibit negative fetal effects on birth weight, likely reflecting antagonistic pleiotropy.Peer reviewe