Ten Years of Provenance Trials and Application of Multivariate Random Forests Predicted the Most Preferable Seed Source for Silviculture of Abies sachalinensis in Hokkaido, Japan

Research highlights: Using 10-year tree height data obtained after planting from the range-wide provenance trials of Abies sachalinensis, we constructed multivariate random forests (MRF), a machine learning algorithm, with climatic variables. The constructed MRF enabled prediction of the optimum seed source to achieve good performance in terms of height growth at every planting site on a fine scale. Background and objectives: Because forest tree species are adapted to the local environment, local seeds are empirically considered as the best sources for planting. However, in some cases, local seed sources show lower performance in height growth than that showed by non-local seed sources. Tree improvement programs aim to identify seed sources for obtaining high-quality timber products by performing provenance trials. Materials and methods: Range-wide provenance trials for one of the most important silvicultural species, Abies sachalinensis, were established in 1980 at nine transplanting experimental sites. We constructed an MRF to estimate the responses of tree height at 10 years after planting at eight climatic variables at 1 km × 1 km resolution. The model was applied for prediction of tree height throughout Hokkaido Island. Results: Our model showed that four environmental variables were major factors affecting height growth—winter solar radiation, warmth index, maximum snow depth, and spring solar radiation. A tree height prediction map revealed that local seeds showed the best performance except in the southernmost region and several parts of northern regions. Moreover, the map of optimum seed provenance suggested that deployment of distant seed sources can outperform local sources in the southernmost and northern regions. Conclusions: We predicted that local seeds showed optimum growth, whereas non-local seeds had the potential to outperform local seeds in some regions. Several deployment options were proposed to improve tree growth

Geographical Gradients of Genetic Diversity and Differentiation among the Southernmost Marginal Populations of Abies sachalinensis Revealed by EST-SSR Polymorphism

Research Highlights: We detected the longitudinal gradients of genetic diversity parameters, such as the number of alleles, effective number of alleles, heterozygosity, and inbreeding coefficient, and found that these might be attributable to climatic conditions, such as temperature and snow depth. Background and Objectives: Genetic diversity among local populations of a plant species at its distributional margin has long been of interest in ecological genetics. Populations at the distribution center grow well in favorable conditions, but those at the range margins are exposed to unfavorable environments, and the environmental conditions at establishment sites might reflect the genetic diversity of local populations. This is known as the central-marginal hypothesis in which marginal populations show lower genetic variation and higher differentiation than in central populations. In addition, genetic variation in a local population is influenced by phylogenetic constraints and the population history of selection under environmental constraints. In this study, we investigated this hypothesis in relation to Abies sachalinensis, a major conifer species in Hokkaido. Materials and Methods: A total of 1189 trees from 25 natural populations were analyzed using 19 EST-SSR loci. Results: The eastern populations, namely, those in the species distribution center, showed greater genetic diversity than did the western peripheral populations. Another important finding is that the southwestern marginal populations were genetically differentiated from the other populations. Conclusions: These differences might be due to genetic drift in the small and isolated populations at the range margin. Therefore, our results indicated that the central-marginal hypothesis held true for the southernmost A. sachalinensis populations in Hokkaido

Influence of soil properties on the heartwood colour of Juglans mandshurica var. sachalinensis in a cool temperate forest

Heartwood colour is often an important factor in determining timber prices. However, the determinants of intraspecific variation in heartwood colour, which is useful information for sustainable wood marketing, are little understood, especially at the local scale in cool temperate forests. Because heartwood is produced as a secondary compound and photosynthesis is regulated by nitrogen (N) in cool temperate forests, we hypothesized that (1) soil conditions determine heartwood colour even at a local scale within a tree species and (2) N, specifically, can be an important driver of the intraspecific variation in heartwood colour in the trees of cool temperate forests. To test these hypotheses, we investigated the relationship between the colour values (luminescence, redness, and yellowness) of heartwood from Juglans mandshurica var. sachalinensis and the soil parameters in a cool temperate forest. Among the soil properties, not soil N but soil magnesium (Mg) contents alone had a significant influence on the redness and yellowness of the heartwood. Higher soil Mg contents resulted in increased redness and yellowness of the heartwood in our study, probably due to the increase in phenolics and the colouring of the tannins in the heartwood with Mg. Our results indicate that even at a local scale, soil condition can determine the intraspecific variation in heartwood colour and that forest managers can utilize edaphic information to predict heartwood colour for timber marketing

Biodiversity can benefit from climate stabilization despite adverse side effects of land-based mitigation

生物多様性保全と温暖化対策は両立できることが判明 --生物多様性の損失は気候安定化の努力で抑えられる--. 京都大学プレスリリース. 2019-12-04.Limiting the magnitude of climate change via stringent greenhouse gas (GHG) mitigation is necessary to prevent further biodiversity loss. However, some strategies to mitigate GHG emission involve greater land-based mitigation efforts, which may cause biodiversity loss from land-use changes. Here we estimate how climate and land-based mitigation efforts interact with global biodiversity by using an integrated assessment model framework to project potential habitat for five major taxonomic groups. We find that stringent GHG mitigation can generally bring a net benefit to global biodiversity even if land-based mitigation is adopted. This trend is strengthened in the latter half of this century. In contrast, some regions projected to experience much growth in land-based mitigation efforts (i.e., Europe and Oceania) are expected to suffer biodiversity loss. Our results support the enactment of stringent GHG mitigation policies in terms of biodiversity. To conserve local biodiversity, however, these policies must be carefully designed in conjunction with land-use regulations and societal transformation in order to minimize the conversion of natural habitats

Eight-Year Survival and Growth of Sakhalin Fir (<i>Abies sachalinensis</i>) Seedlings with One Weeding Operation: Impact of Mechanical Site Preparation, Vegetation Release, Summer Planting, Stock Type, and Forwarder Trail

In Hokkaido, northern Japan, bareroot Sakhalin fir seedlings are conventionally planted in spring and fall, following strip site preparation that alternates managed and unmanaged strips. However, this method requires seven years of weeding due to encroachment of evergreen dwarf bamboo. Given diminishing forest labor availability, a shortage of workers for planting and weeding operations has become a problem in reforestation following clearcutting. We examined whether comprehensive mechanical site preparation (MSP) could reduce weeding frequency by preventing regrowth of dwarf bamboo and whether container seedlings could extend the planting season into summer. Over eight years, the survival and growth of summer-planted bareroot and container seedlings were examined on a fully MSP-treated site with only one weeding operation in the fifth year. Full-site MSP resulted in a shift of the vegetation from dwarf bamboo to deciduous plants, leading to high survival and growth rates of Sakhalin fir seedlings despite minimal weeding. Container seedlings exhibited superior establishment and maintained higher survival rates over eight years than bareroot seedlings. However, planting on the forwarder trail decreased seedling growth, and ultimately decreased survival under rare summer drought. Our findings indicate that container seedling summer planting and full-site MSP may represent an alternative approach to reforestation of Sakhalin fir, potentially reducing the need for weeding and extending the planting season

Modeling future wildlife habitat suitability: serious climate change impacts on the potential distribution of the Rock Ptarmigan Lagopus muta japonica in Japan’s northern Alps

Abstract Background The Rock Ptarmigan Lagopus muta japonica lives in the alpine zones of central Japan, which is the southern limit of the global distribution for this species. This species is highly dependent on alpine habitats, which are considered vulnerable to rapid climate change. This study aimed to assess the impact of climate change on potential L. muta japonica habitat based on predicted changes to alpine vegetation, to identify population vulnerability under future climatic conditions for conservation planning. We developed species distribution models, which considered the structure of the alpine ecosystem by incorporating spatial hierarchy on specific environmental factors to assess the potential habitats for L. muta japonica under current and future climates. We used 24 general circulation models (GCMs) for 2081–2100 as future climate conditions. Results The predicted potential habitat for L. muta japonica was similar to the actual distribution of the territories in the study area of Japan’s northern Alps (36.25–36.5°N, 137.5–137.7°E). Future potential habitat for L. muta japonica was projected to decrease to 0.4% of the current potential habitat in the median of occurrence probabilities under 24 GCMs, due to a decrease in alpine vegetation communities. Some potential habitats in the central and northwestern part of the study area were predicted to be sustained in the future, depending on the GCMs. Conclusions Our model results predicted that the potential habitats for L. muta japonica in Japan’s northern Alps, which provides core habitat for this subspecies, would be vulnerable by 2081–2100. Small sustainable habitats may serve as refugia, facilitating the survival of L. muta japonica populations under future climatic conditions. Impact assessment studies of the effect of climate change on L. muta japonica habitats at a nationwide scale are urgently required to establish effective conservation planning for this species, which includes identifying candidate areas for assisted migration as an adaptive strategy