Ikutaro Tsuyama

Climatic controls of a keystone understory species, Sasamorpha borealis, and an impact assessment of climate change in Japan

IntroductionThe aims of this study were to identify the climatic conditions controlling the distribution of Sasamorpha borealis and to assess the impact of climate change on the species in Japan.Materials and methodsThe relationship between S. borealis distribution and climatic variables in the Japanese Archipelago was explored using classification tree analysis. Potential habitat maps under the current and future climates were generated at about 1-km spatial resolution.ResultsThe model was highly accurate. Although snow cover has been thought to be the most important factor controlling S. borealis distribution, we revealed that the species requires high precipitation during the growing season even in humid Japanese environments. Areas with high summer (May–September) precipitation (PRS) were classified as potential habitat irrespective of other climatic conditions. In areas with moderate PRS, potential habitat was limited to cooler and less snow-covered areas and areas with low PRS were classified as non-habitat. The high fitness of the predicted to the observed distributions suggested that S. borealis could have survived throughout the Japanese Archipelago during the glacial period.ConclusionIn future climates, 29.0–39.1% of the current potential habitat was predicted to change to non-habitat due to increasing dryness in the growing season. Areas with high precipitation remained a potential habitat for S. borealis.

The effects of future nationwide forest transition to discharge in the 21st century with regard to general circulation model climate change scenarios

Forest disturbance (or land-cover change) and climatic variability are commonly recognised as two major drivers interactively influencing hydrology in forested watersheds. Future climate changes and corresponding changes in forest type and distribution are expected to generate changes in rainfall runoff that pose a threat to river catchments. It is therefore important to understand how future climate changes will effect average rainfall distribution and temperature and what effect this will have upon forest types across Japan. Recent deforestation of the present-day coniferous forest and expected increases in evergreen forest are shown to influence runoff processes and, therefore, to influence future runoff conditions. We strongly recommend that variations in forest type be considered in future plans to ameliorate projected climate changes. This will help to improve water retention and storage capacities, enhance the flood protection function of forests, and improve human health. We qualitatively assessed future changes in runoff including the effects of variation in forest type across Japan. Four general circulation models (GCMs) were selected from the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble to provide the driving fields: the Model for Interdisciplinary Research on Climate (MIROC), the Meteorological Research Institute Atmospheric General Circulation Model (MRI-GCM), the Hadley Centre Global Environment Model (HadGEM), and the Geophysical Fluid Dynamics Laboratory (GFDL) climate model. The simulations consisted of an ensemble including multiple physics configurations and different reference concentration pathways (RCP2.6, 4.5, and 8.5), the results of which have produced monthly data sets for the whole of Japan. The impacts of future climate changes on forest type in Japan are based on the balance amongst changes in rainfall distribution, temperature and hydrological factors. Methods for assessing the impact of such changes include the Catchment Simulator modelling frameworks based on the Minimal Advanced Treatments of Surface Interaction and Runoff (MATSIRO) model, which was expanded to estimate discharge by incorporating the effects of forest-type transition across the whole of Japan. The results indicated that, by the 2090s, annual runoff will increase above present-day values. Increases in annual variation in runoff by the 2090s was predicted to be around 14.1% when using the MRI-GCM data and 44.4% when using the HadGEM data. Analysis by long-term projection showed the largest increases in runoff in the 2090s were related to the type of forest, such as evergreen. Increased runoff can have negative effects on both society and the environment, including increased flooding events, worsened water quality, habitat destruction and changes to the forest moisture-retaining function. Prediction of the impacts of future climate change on water generation is crucial for effective environmental planning and management.

Land abandonment and changes in snow cover period accelerate range expansions of sika deer

Abstract Ongoing climate change and land‐use change have the potential to substantially alter the distribution of large herbivores. This may result in drastic changes in ecosystems by changing plant–herbivore interactions. Here, we developed a model explaining sika deer persistence and colonization between 25 years in terms of neighborhood occupancy and habitat suitability. We used climatic, land‐use, and topographic variables to calculate the habitat suitability and evaluated the contributions of the variables to past range changes of sika deer. We used this model to predict the changes in the range of sika deer over the next 100 years under four scenario groups with the combination of land‐use change and climate change. Our results showed that both climate change and land‐use change had affected the range of sika deer in the past 25 years. Habitat suitability increased in northern or mountainous regions, which account for 71.6% of Japan, in line with a decrease in the snow cover period. Habitat suitability decreased in suburban areas, which account for 28.4% of Japan, corresponding to land‐use changes related to urbanization. In the next 100 years, the decrease in snow cover period and the increase in land abandonment were predicted to accelerate the range expansion of sika deer. Comparison of these two driving factors revealed that climate change will contribute more to range expansion, particularly from the 2070s onward. In scenarios that assumed the influence of both climate change and land‐use change, the total sika deer range increased by between +4.6% and +11.9% from the baseline scenario. Climate change and land‐use change will require additional efforts for future management of sika deer, particularly in the long term.

Projecting spatiotemporal changes in suitable climate conditions to regenerate trees using niche differences between adult and juvenile trees

Assessing suitable climate conditions to regenerate trees over a large area is of great importance to investigate potential impacts of climate change. In this study, we developed a size-based species distribution model (SBSDM) to assess spatiotemporal changes in the tree regeneration niche separately from the growth niche in adults. Siebold’s beech (Fagus crenata) was selected as the target species. We projected (1) areas where adult and juvenile potential habitats (PHs) overlapped, (2)only-adult PHs, (3) only-juvenile PHs, and (4) non-habitats for 2080–2099 using the SBSDM, a distribution dataset from the Phytosociological Relevé Database of Japan, and a future climatic dataset from 24 general circulation models (GCMs). We also projected juvenile PHs for all decades between 2011 and 2099 using four representative GCMs to assess potential lost decades of the regeneration niche. The SBSDM provided sufficient projections of adult and juvenile tree distributions as well as their niche differences under the current climate. Overlapping areas and only-adult PHs were projected to decrease by the end of this century. An increase in only-juvenile PHs was projected to occur in snowy regions, with juvenile PHs starting to decrease in warm and less snowy regions. Furthermore, juvenile PHs are expected to decrease widely around 2060 as well as at the end of this century due to considerable rapid warming around those times. We conclude that regeneration of F. crenata will start to decline in 2060, but snowy conditions will postpone the timing of the regeneration loss, causing an increase in only-juvenile PHs.

Fine-resolution assessment of potential refugia for a dominant fir species (Abies mariesii) of subalpine coniferous forests after climate change

The questions “Will the environment surrounding moorlands become refugia for a Japanese subalpine coniferous species, Abies mariesii Mast., after climate change?” and “How does the spatial resolution of a species distribution model affect the global warming predictions?” have been discussed in this study. This study was conducted at Hakkoda Mountains, the northern side of Honshu Island, Japan. We constructed 50-m mesh model using a climate variable, two topography variables and two variables relating to moorlands. We applied the model to eight global warming scenarios, including decreasing or non-decreasing scenarios of moorlands. We also constructed a coarse-resolution model at approximately 1-km resolution and compared the model predictions with the fine ones. The results showed that the coarse-resolution model tended to overestimate the range of suitable habitats for A. mariesii. On the other hand, some suitable habitats around moorlands could only be predicted by the fine-resolution model. The fine-resolution model indicated that the peripheries of the moorlands are the most important potential refugia for A. mariesii on Hakkoda Mountains. Although these suitable areas were notable in the +2°C scenario, all suitable habitats completely disappeared in the +4°C scenario. We concluded that it would be effective to conserve the A. mariesii populations around moorlands which are likely to persist after global warming, as well as moorlands themselves. This assessment could only be achieved by fine-resolution models that incorporate non-climatic variables including topography and moorland-related variables with climatic variables. In contrast, a coarse-resolution model overestimated the suitable habitats whilst underestimating potential local refugia. Thus, fine-resolution models are more effective for developing practical adaptation of conservation measures.

Vulnerability of subalpine fir species to climate change: using species distribution modeling to assess the future efficiency of current protected areas in the Korean Peninsula

To facilitate the adaptive management of subalpine ecosystems in the Korean Peninsula under climate change conditions, we identified the climatic factors that determine the distribution of two dominant subalpine firs (Abies koreana and A. nephrolepis). We also identified sustainable and vulnerable habitats for these species inside and outside of current protected areas under climate change scenarios. The minimum temperature of the coldest month, and the amount of precipitation in the warmest quarter were the most important climatic variables that determined the distribution of these two Abies species. Potential habitats for A. koreana and A. nephrolepis were predicted to decrease to 3.3% and 36.4% of the current areas due to climate change, irrespective of whether inside or outside the protected areas. It was predicted that the potential habitats for A. nephrolepis would be maintained in the northern part of the Korean Peninsula, and sustainable potential habitats outside the protected areas were predicted in central parts of the Korean Peninsula. The potential habitats for A. koreana were predicted to disappear from Is. Jeju and shrink significantly in the Korean Peninsula. These results suggest that, in central parts of the Korean Peninsula, revision of protected areas would be effective in preserving A. nephrolepis under conditions of future climate change. In contrast, revision of protected areas would be insufficient to conserve A. koreana due to their high vulnerability and limited populations. Active management is required to ensure the survival of A. koreana under future climate conditions.

Potential impact of climate change on canopy tree species composition of cool-temperate forests in Japan using a multivariate classification tree model

Climate change will likely change the species composition or abundance of plant communities, and it is important to anticipate these changes to develop climate change adaptation policies. We chose beech (Fagus crenata Blume) and its competitive tree species as target species to evaluate potential turnover in forest types under climate change using a multivariate classification tree model. To construct the model, geographical presence/absence data for nine target species were used as multivariate response variables, with five climatic factors were used as predictor variables. Current and future distribution probabilities for the target species were calculated, and the 15 dominant forest types were subjectively classified in approximately 1-km2 grid cells within the area of the current beech forest distribution. All 16,398 grid cells of the beech-dominant forest type (FCR-QCR) were projected to be replaced in the future by five Quercus crispula-dominant types (59% of FCR-QCR grid cells), four Q. serrata types (22%), two Q. salicina types (8%), or two Abies firma types (0.1%). The FCR-QCR type remained unchanged (stable) in only 11.4% of grid cells; these were mainly distributed at high elevations in snowy areas on the Sea of Japan side of the country. In contrast, vulnerable habitats (future probability of beech occurrence less than 1.0%) were found at low elevations on both the Sea of Japan and the Pacific Ocean sides. Northwards or upwards range expansions or increases of Quercus spp., in particular, need to be carefully monitored.