Cool-temperate Deciduous Broad-leaved Forest Research Articles

Effects of the Co-Application of Glucose, Nitrogen, and Elevated Temperature on Buried Black Soil Carbon in a Cool Temperate Deciduous Broad-Leaved Forest

Accurately predicting the feedback mechanisms between forest ecosystem carbon cycling and climate change is crucial for effective climate mitigation. Understanding soil organic carbon (SOC) responses to the combined impacts of plant biomass, litter, and nitrogen deposition, especially regarding temperature sensitivity, is essential but remains poorly understood. We conducted incubation experiments using buried black soil from a cool temperate deciduous broad-leaved forest in Japan, which has high C content and a highly stable molecular structure. The stepwise addition of glucose and a temperature increase from 15 to 35 °C accelerated SOC mineralization by 74.0 mg C kg−1 with a positive priming effect (PE) during the 49-day incubation period, while the simultaneous addition of nitrogen had no significant effect on this phenomenon, with SOC mineralization measured at 75.5 mg C kg−1. Conversely, glucose mineralization was significantly accelerated by 10%, from 241.0 to 261.3 mg C kg−1, by stepwise nitrogen addition and temperature increase. Under the combined impacts, the Q10 value of the soil increased significantly from 1.6 to 2.0 compared to that in the unmodified conditions, primarily due to the stepwise addition of glucose. We also found a strong positive correlation between activation energy (Ea) and Q10. This result strongly supports the carbon quality–temperature (CQT) hypothesis. These results likely stem from interactions between SOC quality and carbon availability, suggesting that, in the future, climate change is likely to have a positive feedback effect, especially on buried black soils.

The Nitrogen Cycle of a Cool-Temperate Deciduous Broad-Leaved Forest

The nitrogen (N) cycle, a major biogeochemical cycle in forest ecosystems, notably affects ecosystem multifunctionality. However, the magnitude and role of organic N and the snow season remain uncertain in this cycle. We assessed the N flux and pool data of a temperate deciduous broad-leaved forest to clarify N cycle processes. The results showed that the most important component of the N pool was the soil N pool. The N demand of the site amounted to 139.4 kg N ha−1 year−1 and was divided into tree production (83.8%) and bamboo production (16.2%). We clarified that retranslocation (37.4%), mineralization at a soil depth of 0–5 cm (15.3%), litter leachate (4.6%), throughfall (2.3%), and canopy uptake (0.5%) provided 60.1% of the N demand. In terms of soil at 0–5 cm in depth, the net mineralization rate during the snow season contributed to 30% of the annual mineralization. We concluded that the study site was not N-saturated as a result of a positive N input–output flux budget. More than half of the total N was accounted for by dissolved organic N flowing through several pathways, indicating that organic N plays a vital role in the cycle. The mineralization rate in the soil layer during the snow season is an important link in the N cycle.

Detection of the different characteristics of year-to-year variation in foliage phenology among deciduous broad-leaved tree species by using daily continuous canopy surface images

Clarification of species-specific year-to-year variations of the timings of the start of leaf-expansion (SLE) and the end of leaf-fall (ELF) is an important and challenging task because these timings may alter spatial and temporal variations in ecosystem services such as carbon stock and climate control. Although many previous studies have applied automatically captured digital camera images to observe the timings of SLE and ELF, the evaluation of the long-term variation in both timings of each tree species based on image analysis has not yet been sufficiently investigated. In this study, we investigated the year-to-year variation in the timings of SLE and ELF for multiple deciduous broad-leaved tree species in a cool-temperate deciduous broad-leaved forest in Japan by using long-term and daily hemispherical (“fish-eye”) canopy surface images from 2004 to 2013. We found that (1) differences in the characteristics of year-to-year variations in the timing of ELF among the tree species were more apparent than those of the timing of SLE among the tree species, (2) the threshold value of the camera-based index (green excess index) for detecting the timing of ELF varied depending on the spatial and temporal distribution of understories and the visual distortion of the fish-eye images, and (3) the phenological sensitivity of the timing of ELF to air temperature was lower than that of the timing of SLE. Our results indicate that it might be helpful for ecologists to use daily continuous canopy surface images for monitoring of species-specific characteristics of spatial and temporal changes in foliage phenology in mixed-species deciduous broad-leaved forests.

Relationship between spatio-temporal characteristics of leaf-fall phenology and seasonal variations in near surface- and satellite-observed vegetation indices in a cool-temperate deciduous broad-leaved forest in Japan

We examined the relationship between the spatio-temporal distribution of leaf litter for each species and the seasonal patterns of in situ and satellite-observed daily vegetation indices in a cool-temperate deciduous broad-leaved forest. The timing and distribution of leaf-fall revealed spatio-temporal relationships with species and topography. Values of the normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and green–red vegetation index (GRVI), measured both in situ and by satellite, and those of the in situ-measured leaf area index (LAI), rapidly declined at the peak of leaf-fall. At the late stage of leaf-fall, in situ-measured values of NDVI, EVI, and LAI declined but those of GRVI changed from decreasing to increasing. The peak timing of leaf-fall, when 50–73% of the leaf litter had fallen, corresponds to LAI = 1.80–0.81, NDVI = 0.61–0.54, EVI = 0.29–0.25, and GRVI = 0.01 ∼ ‒0.07. Although the distribution of leaf litter among species displayed spatial characteristics at the peak of leaf-fall, spatial heterogeneity of amount of leaf litter at the peak timing of leaf-fall was less than that at the beginning and end. These facts suggest that the criterion for determining the timing of leaf-fall from vegetation indices should be a value corresponding to the peak of leaf-fall rather than its end. In a high-biodiversity forest, such as this study forest, the effect of spatial heterogeneity on the timing and patterns of leaf-fall on vegetation indices can be reduced by observing only the seasonal variation in colour on the canopy surface by using GRVI, which consists of visible reflectance bands, rather than that of both leaf area and colour of the canopy surface by using NDVI and EVI, which consist of visible and near-infrared reflectance bands.

The necessity and availability of noise-free daily satellite-observed NDVI during rapid phenological changes in terrestrial ecosystems in East Asia

General, global, long-term, and comprehensive phenological observations are required to evaluate the variability of photosynthetic activities due to environmental changes in terrestrial ecosystems. The observation of seasonal changes and detection of interannual variation in canopy phenology over regional and global scales require satellite data with high temporal resolution (i.e. a daily time step). However, satellite data often include noise caused by snow cover on vegetation, cloud contamination, and atmospheric aerosols. To accurately detect the timing of leaf-expansion and leaf-fall, which occur rapidly, and their rates, it is necessary to examine the observational frequency of noise-free satellite-observed vegetation index data during each phenological period. In this study, we investigated the spatio-temporal distribution of the number of observational days (NUMdays) in the Terra/MODIS (Moderate Resolution Imaging Spectroradiometer)-observed daily high-quality normalized difference vegetation index (NDVIhigh) data with no effects of snow cover, cloud contamination, or atmospheric noise. These data were examined for each month over 10 years in the various ecosystems of East Asia. To ground-truth the relationship between the Terra/MODIS-observed daily NDVIhigh data and canopy surface images, we performed a long-term continuous field study in a cool-temperate deciduous broad-leaved forest in central Japan. During the leaf-expansion and leaf-fall periods, the NUMdays for NDVIhigh data in southern Russia, northeastern China, the Tibetan Plateau, Korea, and maritime Japan was about 3–7 for each month. The NUMdays for NDVIhigh data exceeded 10 for each month in arid regions during the growing season and in the subtropical region including northeastern India, Myanmar, and southwestern China during the dry season. In contrast, the NUMdays for NDVIhigh data was almost 0 for each month in southeastern China throughout the year and in the subtropical region during the southeastern monsoon season (July and August). By considering observations from both the Terra/MODIS and Aqua/MODIS satellites, the NUMdays for NDVIhigh data in the deciduous broad-leaved forest in Japan was increased by 40% compared with only Terra/MODIS satellite observations. Our findings indicate that daily NDVI data from multiple satellites detect the seasonal changes in the various ecosystems of East Asia more accurately than 8-day or biweekly composite NDVI data.

An evaluation of empirical regression models for predicting temporal variations in soil respiration in a cool-temperate deciduous broad-leaved forest

Soil respiration (<TEX>$R_S$</TEX>) is a critical component of the annual carbon balance of forests, but few studies thus far have attempted to evaluate empirical regression models in <TEX>$R_S$</TEX>. The principal objectives of this study were to evaluate the relationship between <TEX>$R_S$</TEX> rates and soil temperature (ST) and soil water content (SWC) in soil from a cool-temperate deciduous broad-leaved forest, and to evaluate empirical regression models for the prediction of <TEX>$R_S$</TEX> using ST and SWC. We have been measuring <TEX>$R_S$</TEX>, using an open-flow gas-exchange system with an infrared gas analyzer during the snowfree season from 1999 to 2001 at the Takayama Forest, Japan. To evaluate the empirical regression models used for the prediction of <TEX>$R_S$</TEX>, we compared a simple exponential regression (flux = <TEX>$ae^{bt}$</TEX>Eq. [1]) and two polynomial multiple-regression models (flux = <TEX>$ae^{bt}{\times}({\theta}{\nu}-c){\times}(d-{\theta}{\nu})^f:$</TEX> Eq. [2] and flux = <TEX>$ae^{bt}{\times}(1-(1-({\theta}{\nu}/c))^2)$</TEX>: Eq. [3]) that included two variables (ST: t and SWC: <TEX>${\theta}{\nu}$</TEX>) and that utilized hourly data for <TEX>$R_S$</TEX>. In general, daily mean <TEX>$R_S$</TEX> rates were positively well-correlated with ST, but no significant correlations were observed with any significant frequency between the ST and <TEX>$R_S$</TEX> rates on periods of a day based on the hourly <TEX>$R_S$</TEX> data. Eq. (2) has many more site-specific parameters than Eq. (3) and resulted in some significant underestimation. The empirical regression, Eq. (3) was best explained by temporal variations, as it provided a more unbiased fit to the data compared to Eq. (2). The Eq. (3) (ST <TEX>$\times$</TEX> SWC function) also increased the predictive ability as compared to Eq. (1) (only ST exponential function), increasing the <TEX>$R^2$</TEX> from 0.71 to 0.78.

The ratio of transmitted near-infrared radiation to photosynthetically active radiation (PAR) increases in proportion to the adsorbed PAR in the canopy

The daily total photosynthetically active radiation (400-700nm, PAR) and near-infrared radiation (700-1000nm, NIR) were measured in the understory beneath the canopy (PARt and NIRt) and above the canopy (PARi and NIRi) of a Japanese cool-temperate deciduous broad-leaved forest during the snow-free period (May to November). The integration of spectral radiation for NIR and that for PAR, and the daily integrations of instantaneous NIR and PAR, reduced the noises from the optical difference in spectrum and from canopy structure heterogeneity, sky condition and solar elevation. PARi/PARt was linearly related to NIRt/PARt (R²=0.96). The effect of cloudiness was negligible, because the fluctuation of NIRi/PARi was quite small regardless of season and weather conditions compared with the range of NIRt/PARt in the forest. The ratio of NIRt/PARt beneath the canopy was log-linearly related to the in situ leaf area index (LAI) with a wide range from 0 to 5.25 (R²=0.97). We conclude that seasonal changes in fAPAR (=1-PARt/PARi) and LAI of a canopy can be estimated with high accuracy by transmitted NIRt and PARt beneath the canopy.

Greenhouse Gas Budget of a Cool-Temperate Deciduous Broad-Leaved Forest in Japan Estimated Using a Process-Based Model

A terrestrial ecosystem model, called the Vegetation Integrative Simulator for Trace gases model (VISIT), which fully integrates biogeochemical carbon and nitrogen cycles, was developed to simulate atmosphere–ecosystem exchanges of greenhouse gases (CO2, CH4, and N2O), and to determine the global warming potential (GWP) taking into account the radiative forcing effect of each gas. The model was then applied to a cool-temperate deciduous broad-leaved forest in Takayama, central Japan (36°08′N, 137°25′E, 1420 m above sea level). Simulations were conducted at a daily time step from 1948 to 2008, using time-series meteorological and nitrogen deposition data. VISIT accurately captured the carbon and nitrogen cycles of this typical Japanese forest, as validated by tower and chamber flux measurements. During the last 10 years of the simulation, the model estimated that the forest was a net greenhouse gas sink, having a GWP equivalent of 1025.7 g CO2 m−2 y−1, most of which (1016.9 g CO2 m−2 y−1) was accounted for by net CO2 sequestration into forest biomass regrowth. CH4 oxidation by the forest soil made a small contribution to the net sink (11.9 g CO2-eq. m−2 y−1), whereas N2O emissions were a very small source (3.2 g CO2-eq. m−2 y−1), as expected for a volcanic soil in a humid climate. Analysis of the sensitivity of GWP to changes in temperature, precipitation, and nitrogen deposition indicated that warming temperatures would decrease the size of the sink, mainly as a result of increased CO2 release due to increased ecosystem respiration.

What makes the satellite‐based EVI–GPP relationship unclear in a deciduous broad‐leaved forest?

AbstractRecent studies have suggested that gross primary production (GPP) of terrestrial vegetation can be estimated directly with the satellite‐based Enhanced Vegetation Index (EVI). However, the reported EVI–GPP relationships showed wide variability, with the regression functions showing widely scattered data. In the present study, we examined the possible reasons for this variability in the EVI–GPP relationship using daily EVI values from satellite and field measurements and daily flux‐based GPP in a cool‐temperate deciduous broad‐leaved forest in Japan. The variability appears to be caused by noise due to cloud contamination in the satellite data as well as the different seasonality of EVI and GPP, especially during the leaf‐expansion period. Our findings indicate that improvement of cloud screening and consideration of the leaf‐expansion period are critical when applying the EVI–GPP relationship.

Field experiments to test the use of the normalized-difference vegetation index for phenology detection

Some previous studies have detected the timing of leaf expansion and defoliation using the normalized-difference vegetation index (NDVI), but to examine tree phenology using satellite data, NDVI results should be confirmed using ground-truthing. We examined the relationship between NDVI and tree phenology during leaf expansion and defoliation by simultaneously observing the spectral reflectance of the canopy surface and canopy surface images in a cool-temperate deciduous broad-leaved forest. To define the timing of leaf expansion and defoliation using NDVI, the index should meet three criteria: (1) NDVI should exhibit a monotonous increase or decrease (monotonicity). (2) The relationship between NDVI and the forest canopy's status should be unique (uniqueness). (3) The method is robust against the systematic noise (bias) (robustness). In the spring, NDVI values of 0.2–0.3 (relative values: 0.15–0.28) and 0.6–0.7 (relative values: 0.65–0.78) satisfied all three criteria. NDVI values of 0.6–0.7 can serve as potential criteria for detecting the timing of leaf expansion. In autumn, no NDVI values satisfied all three criteria. Thus, NDVI does not appear to be useful for detecting the timing of defoliation. For an area where evergreen vegetation or snow covers the forest floor in winter, our results suggest that previous uses of NDVI to identify the timing of leaf expansion and defoliation on the basis of the date of the maximum rate of growth or reduction of NDVI and the date with a value midway between the year's maximum and minimum values are misleading.

The effect of root system in cool-temperate deciduous broad-leaved forest on the slope stability

The effect of root system in cool-temperate deciduous broad-leaved forest on the slope stability

Effects of Phenological Changes of Canopy Leaf on the Spatial and Seasonal Variations of Understory Light Environment in a Cool-temperate Deciduous Broad-leaved Forest.

Effects of Phenological Changes of Canopy Leaf on the Spatial and Seasonal Variations of Understory Light Environment in a Cool-temperate Deciduous Broad-leaved Forest.

Examination of model-estimated ecosystem respiration using flux measurements from a cool-temperate deciduous broad-leaved forest in central Japan

Examination of model-estimated ecosystem respiration using flux measurements from a cool-temperate deciduous broad-leaved forest in central Japan

Examination of model-estimated ecosystem respiration using flux measurements from a cool-temperate deciduous broad-leaved forest in central Japan

Reducing uncertainty in the emission of carbon dioxide (CO2) from plants and microbes is critically important in determining carbon budgets. We examined properties of net ecosystem CO2 exchange (NEE) derived from a processbased model that simulates an ecosystem carbon cycle, focusing on nighttime flux determined from ecosystem respiration and soil efflux. The model simulated autotrophic and heterotrophic respiration using semi-empirical ecophysiological parameterizations. In a cool-temperate deciduous broad-leaved forest in central Japan, simulation results from 1998 to 2005 were compared with measurement of the forest made using eddy-covariance and chamber methods. The model estimated annual ecosystem respiration as 1397 g Cm-2 yr-1, of which 67% was from the soil surface, with a clear seasonal cycle. Compared to flux observations, the model appropriately captured daytime NEE, but produced substantial differences from the observed nighttime NEE. The differences were evident under stable atmospheric conditions (at low friction velocity), implying a problem with the observations. With regard to soil-surface CO2 efflux (soil respiration), the model estimation was consistent with chamber observations, except in winter periods with thick snow cover. We discuss whether the model is applicable for estimating ecosystem respiration rates, and what is required to improve the predictability of the model.

A107 MODISデータを用いた大八賀川流域植生フェノロジーの可視化

The purpose of this study is to evaluate phenomenons of the plant physiology and ecology using the satellite observation data in a cool-temperate deciduous broad-leaved forest in central Japan. We compared the satellite observation data (Normalized Difference Vegetation Index: NDVI) with the ground observation data (shoot phenology change, litter fall, and SPAD). The seasonal variability of satellite-based NDVI showed good correlations with those of LAI (Leaf Area Index) and photosynthetic capacity.

Modeling of gross and net carbon dioxide exchange over a cool-temperate deciduous broad-leaved forest in Japan: Analysis of seasonal and interannual change

A process-based model was developed to simulate daily gross carbon dioxide (CO 2) fluxes by photosynthesis and respiration, and net ecosystem CO 2 exchange of a cool-temperate deciduous broad-leaved forest in Takayama, Japan, one of the AsiaFlux sites. The model was derived from a simple carbon cycle model (called Sim-CYCLE), with several modifications to capture seasonal and interannual variability in the CO 2 fluxes, which are regulated at the physiological level. The model for the Takayama site is composed of 12 carbon pools of canopy trees (deciduous), floor plants (evergreen), and soil organic carbon (litter and mineral soil), while the net ecosystem exchange ( F NEE) is obtained from the difference between gross primary production ( F GPP) and autotrophic ( F AR) and heterotrophic ( F HR) respiration. F GPP is estimated by using the Monsi–Saeki model, including regulation of the photosynthetic capacity by temperature, CO 2, and soil water content. F AR is composed of growth and maintenance components, each of which is regulated independently. F HR is a function of temperature and soil water content. Leaf phenology (display in spring and shedding in autumn) of the canopy deciduous trees is empirically determined by the cumulative temperature. The model simulation was conducted for the period from 1948 to 2002, and the results for 1991–2002 were analyzed. Daily F NEE simulated by the model were quantitatively consistent with observations by the eddy covariance method, implying model feasibility to capture the temporal variation in the carbon cycle: +1 g C m −2 day −1 (source) in late autumn to −4 g C m −2 day −1 (sink) in early summer. Because of a past disturbance and environmental change, the Takayama site was evaluated to be a net sink of atmospheric CO 2 (1991–2002 average, −206 g C m −2 yr −1). Leaf phenology of the canopy trees brought about a drastic seasonal change in the light environment and CO 2 budget of the floor plants. A sensitivity analysis indicated that the critical ecophysiological parameters for the net ecosystem exchange of Takayama site were the maximum photosynthetic rate, minimum temperature of photosynthesis, specific leaf maintenance respiration rate, and temperature dependence of maintenance respiration. Finally, several possible applications of the model are presented, and further model modifications are discussed.

Seasonal and annual variations in soil respiration in a cool-temperate deciduous broad-leaved forest in Japan

We investigated the seasonal and annual variations in soil respiration in a cool-temperate oak–birch forest in central Japan and, in particular, to reveal factors determining seasonal variations in the temperature dependence of respiration based on soil CO 2 efflux data for 1999–2002. The daily soil carbon efflux was moderate in late spring (1.8–2.9 g C m −2 day −1 in May), increased sharply to a peak in summer (4.6–6.0 g C m −2 day −1 in August), and decreased in autumn (1.5–2.5 g C m −2 day −1 in November). In winter, the carbon efflux from the snow surface was low (0.29–0.71 g C m −2 day −1). Soil temperature exerted principle control on the seasonal and annual variation of soil respiration. Furthermore, reduced soil water content decreased soil respiration in summer when droughts occurred. The temperature function driven on a seasonal scale showed large variations in seasonal Q 10 and R 0 (simulated soil respiration at a soil temperature of 0 °C), e.g. a higher Q 10 and lower R 0 in spring and a lower Q 10 and higher R 0 in autumn. These large variations in seasonal Q 10 and R 0 might reflect confounding effects of temperature sensitivity and seasonal changes in physiological activities induced by root phenology, microbial biomass, and other factors. These results suggest that if the objective is to simulate soil respiration in a particular season, a seasonal Q 10 function derived from the target period must be used, especially in a forest ecosystem possessing distinct seasonal changes. Conversely, the annual Q 10 function derived from all measurements of daily soil temperature at −1 cm across the 4 years ( Q 10 = 3.8) was adequate for estimating total annual soil respiration because it may integrate all processes that influence soil carbon efflux, despite the fact it may under- or overestimate daily soil carbon efflux on a seasonal scale. Based on this single annual Q 10 function, the annual mean soil respiration in 1999–2002 was estimated to be 853.5 ± 42.4 g C m −2 without topography correction, and 725.5 ± 36.0 g C m −2 with topography correction for a 1 ha experimental area. The estimated annual soil respiration (1999–2002) gave coefficient of variation (CV) value of less than 10%, suggesting a small inter-annual variability in annual soil respiration during 1999–2002 in this forest, since the annual mean temperature was similar in the 4 years of the survey. Carbon efflux from the snow surface accounted for 10% of the annual soil respiration, with a value of 84.3 ± 7.0 g C m −2, indicating the importance of quantifying winter CO 2 efflux within a forest ecosystem in a cold and snowy region.

Refixation of respired CO 2 by understory vegetation in a cool-temperate deciduous forest in Japan

CO 2 released by respiration is either lost from the forest through turbulent mixing or refixed by photosynthesis within the canopy (CO 2 recycling). CO 2 concentration ([CO 2]) in a forest generally increases from canopy layer toward the soil surface due to the high [CO 2] by plant and soil respiration. Therefore, the understory vegetation is capable of fixing the respired CO 2 through photosynthesis, and this process would influence the carbon dynamics within a forest. In this study, in order to evaluate the magnitude of CO 2 recycling by understory vegetation under different environmental conditions and co-occurring photosynthetic/respiratory activity in understory between summer and autumn (after defoliation of forest canopy), we measured [CO 2] and carbon isotope ratios ( δ 13C) of CO 2 and plant organic matter in a cool-temperate deciduous broad-leaved forest at Takayama Experimental Site from the top of the forest canopy to understory layer. The forest canopy is dominated by birch ( Betula ermanii) and oak ( Quercus crispula), and the understory is dominated by an evergreen dwarf bamboo grass ( Sasa senanensis). [CO 2] and δ 13C of CO 2 were vertically stratified in the forest in mid-summer (August), with maximum [CO 2] (ca. 478 ppm) and most negative δ 13C value (−12.5‰) near the soil surface. The diurnal variations of [CO 2] and δ 13C were also clearly observed in the forest; daytime [CO 2] was considerably lower than that in night due to photosynthetic CO 2 uptake in the daytime while respiratory CO 2 efflux and its accumulation occurred around the dense understory vegetation in night. Based on the Sternberg's model [Sternberg, L., 1989. A model to estimate carbon dioxide recycling in forests using 13C/ 12C ratios and concentrations of ambient carbon dioxide. Agric. Forest Meteorol. 48, 163–173; Sternberg, L., Moreia, M.Z., Martinelli, L.A., Victoria, R.L., Barbsoa, E.M., Bonates, L.C.M., Nepstad D.C., 1997. Carbon dioxide recycling in two Amazonian tropical forests. Agric. Forest Meteorol. 88, 259–268] using the data of [CO 2] and δ 13C values of CO 2 and leaves in the forest, we calculated the fraction of respired CO 2 that was refixed photosynthetically by S. senanensis. The percentage of respired CO 2 refixed by S. senanensis was 15% in summer. After the forest canopy defoliation in autumn (October), [CO 2] and δ 13C showed small diurnal variation and small vertical gradients. Although the photosynthetic activity of S. senanensis is enhanced due to sunlight readily reaching the ground surface, the percentage of refixed CO 2 recycled by S. senanensis was 1%. Our result suggests that the dense understory vegetation have an important role in refixing the respired CO 2 in a cool-temperate deciduous forest.

Pedogenic characteristics of soils distributed under Warm-temperate forest climate in Nyu mountains, Fukui Prefecture, Central Japan

The bioclimatic conditions, profile morphology and physico-chemical properties of five different soils under the Warm-temperate deciduous broad-leaved forest climate, Warm-temperate lucidophyllous forest climate, and Cool-temperate deciduous broad-leaved forest climate in the northern part of the Nyu mountains in Fukui Pref., Central Japan were examined. The outline of the results is as follows: 1) The Dark red soil, Kunimidake series, derived from pyroxene andesite may have been formed by the hydrothermal action of volcanism. 2) The Dry brown forest soil, Takasu-1 series, showed a brighter colour in the Bw horizon and a sudden decrease in the humus content below the AB horizon, suggesting that this soil was similar to Yellow-Brown Forest soils rather than to Brown Forest soils. 3) The Dry brown forest soil (reddish), Tega series, is likely to be a Yellow-Brown Forest soil derived from the loess which covered the underlying paleo-red soil. 4) The Red soil, Oshibayama series, was a paleo-red soil in which the upper part had been lost by erosion. 5) The Yellow soil, Yada series, on the Takasu coastal terrace was also considered to be a Yellow-Brown Forest soil affected by the seawater components from the neighboring coast. 6) It was suggested that zonal soils formed under the Warm-temperate deciduous broad-leaved forest climate in the northern part of the Nyu mountains, in the northwestern region of Fukui Pref. were Yellow-Brown Forest soils like those under the Warm-temperate lucidophyllous forest climate.

Characteristics of free sesquioxides and humic acids in soil distributed under Warm-temperate forest climate in Nyu mountains, Fukui Prefecture, Central Japan

The activity and crystallinity ratios of free iron oxides, and the ΔlogK and RF values of humic acids were analyzed in five soil types in the Nyu mountains, Fukui Prefecture, to examine the relation between the zonality of soils and the bioclimatic conditions under the Warm-temperate deciduous broad-leaved forest climate. The characteristics of free iron oxides and humic acids were as follows: The Dark red soil, Kunimidake series was a Dark Red soil under the Cool-temperate deciduous broad-leaved forest climate; the Dry brown forest soil (reddish), Tega series was a Yellow-Brown Forest soil under the Warm-temperate deciduous broad-leaved forest climate; the Dry brown forest soil, Takasu-1 series and the Yellow soil, Yada series were Yellow-Brown Forest soils under the Warm-temperate lucidophyllous forest climate; and the Red soil, Oshibayama series and the lower parts of the Tega series were paleo-red soils. These results indicated that zonal soils under the Warm-temperate deciduous broad-leaved forest climate were Yellow-Brown Forest soils in the Nyu mountains, Fukui Prefecture. The Dark red soil, Kunimidake series corresponded to a Hyperdystri-Rhodic Cambisol of World Reference Base for Soil Resources, WRB (FAO, ISRIC, and ISSS: World Soil Resources Reports 84, 1998). The Dry brown forest soil (reddish), Tega series, the Dry brown forest soil, Takasu-1 series, and the Red soil, Oshibayama series were compared with the Hyperdystri-Chromic Cambisol (WRB). The Yellow soil, Yada series was a Hypereutri-Chromic Cambisol (WRB).