Deciduous Broad-leaved Forest In Japan 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.

Vegetation and climate histories between MIS 63 and 53 in the Early Pleistocene in central Japan based on plant macrofossil evidences

Among the Early Pleistocene fluvial sediments in Japan that yield plant macrofossils, the Uonuma Group in the Niigata sedimentary basin provides the most continuous profile without any conspicuous hiatuses and is therefore suitable for high-resolution reconstructions of environmental and vegetation histories based on tephro- and magneto-stratigraphy. Based on the species composition of plant macrofossil assemblages, along with previously reported results on sedimentary environments and pollen records, we performed a reconstruction of changes in paleovegetation and paleotemperatures between MIS 63 and 53. Macrofossil assemblages identified from 33 samples include 89 arboreal and 88 herbaceous taxa in total, of which 9 taxa are extinct from Japan. Assemblages from the peat deposits in fluvial backmarshes during glacial stages are composed mainly of wetland herbaceous plants, whereas those from the sandy channel-fill deposits are characterized by a higher diversity in life forms and habitat preferences. During the interval from MIS 63 to 53, paleotemperatures fluctuated between a coldest-month mean temperature of −4.6 °C and −0.9 °C and between a mean annual temperature of 6.6 °C and 11.0 °C, which is within the present range for cool-temperate, deciduous broad-leaved forests in Japan. MIS 60 was the coldest of the glacial stages with temperatures nearly equivalent to those during the last glacial maximum. Major plant extinctions in and around MIS 60 were not recorded in the sedimentary basin in response to the temperature decline. The relatively indistinct floral changes in and around MIS 60 are attributed to easier recovery of flora by migration from glacial refugia in the southern basins after termination of the glacial stage. Interglacial temperatures during MIS 57, 55, and 53 were higher than during MIS 63, 61, and 59. The presence of a maritime environment during the interglacial periods between MIS 57 and 53 may have resulted from a greater extent of marine transgression and heat provided by the Tsushima Warm Current flowing into the Sea of Japan after MIS 59.

Seasonal leaf phenology data for 12 tree species in a cool‐temperate deciduous broadleaved forest in Japan from 2005 to 2014

AbstractThis paper reports seasonal data regarding leaf number, leaf length and width, leaf area, leaf angle, and SPAD (leaf chlorophyll content index) for 11 genera (12 species) in a cool‐temperate deciduous broadleaved forest in Japan. Knowing the leaf phenology of tree species is important for accurately evaluating the temporal variability of ecosystem functions (e.g., photosynthesis and evapotranspiration) under rapid climate change. However, there is a lack of freely available long‐term observation data regarding leaf phenological characteristics for many tree species. We collected leaf phenological data from tagged shoots every 1–4 weeks from April or May to October or November each year from 2005 to 2014 in Takayama, Japan (36°08′46″N, 137°25′23″E, 1420 m a.s.l.). We targeted typical dominant, codominant, and understory tree species at the site. To evaluate differences among individuals and between sunlit and shaded leaves, we measured one to four shoots of some species and individuals. Our data provide input, calibration, and validation parameters for a terrestrial ecosystem and for radiative‐transfer models and remote‐sensing observations.

Uncertainties involved in leaf fall phenology detected by digital camera

We evaluated the uncertainty in the estimation of year-to-year variability in the timing of leaf fall detected by the analysis of red, green and blue (RGB) values extracted from daily phenological images in a deciduous broad-leaved forest in Japan. We examined (1) the spatial distribution of individual tree species within a 1-ha permanent plot and the spatio-temporal variability of leaf litter of various species for 8years; and (2) the relationship between the year-to-year variability of leaf fall detected by leaf litter and that detected by phenological images of various species. Uncertainties were caused by (1) the heterogeneous distribution of each species within the whole forest community; (2) the year-to-year variability of the timing of leaf fall among species; and (3) differences in leaf colouring and leaf fall patterns among species. Our results indicate the importance of integrating RGB analysis of each species and of the whole canopy on the basis of spatial locations of individuals and proportions of tree species within a forest to reduce uncertainty.

Relationship between the decomposition process of coarse woody debris and fungal community structure as detected by high-throughput sequencing in a deciduous broad-leaved forest in Japan.

We examined the relationship between the community structure of wood-decaying fungi, detected by high-throughput sequencing, and the decomposition rate using 13 years of data from a forest dynamics plot. For molecular analysis and wood density measurements, drill dust samples were collected from logs and stumps of Fagus and Quercus in the plot. Regression using a negative exponential model between wood density and time since death revealed that the decomposition rate of Fagus was greater than that of Quercus. The residual between the expected value obtained from the regression curve and the observed wood density was used as a decomposition rate index. Principal component analysis showed that the fungal community compositions of both Fagus and Quercus changed with time since death. Principal component analysis axis scores were used as an index of fungal community composition. A structural equation model for each wood genus was used to assess the effect of fungal community structure traits on the decomposition rate and how the fungal community structure was determined by the traits of coarse woody debris. Results of the structural equation model suggested that the decomposition rate of Fagus was affected by two fungal community composition components: one that was affected by time since death and another that was not affected by the traits of coarse woody debris. In contrast, the decomposition rate of Quercus was not affected by coarse woody debris traits or fungal community structure. These findings suggest that, in the case of Fagus coarse woody debris, the fungal community structure is related to the decomposition process of its host substrate. Because fungal community structure is affected partly by the decay stage and wood density of its substrate, these factors influence each other. Further research on interactive effects is needed to improve our understanding of the relationship between fungal community structure and the woody debris decomposition process.

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.

Linkages between diurnal patterns of root respiration and leaf photosynthesis in Quercus crispula and Fagus crenata seedlings

The physiological traits of tree roots have been considered associating with photosynthetic capacity; however, the linkages between diurnal patterns of root respiration and assimilation in individual leaves are poorly understood. Our objectives were to investigate the diurnal patterns of tree root respiration and the assimilation under natural luminous environments and to explore the potential environmental drivers of root respiration and the assimilation by relating trees' diurnal cycle to commonly measured variables. We simultaneously and continuously measured individual leaf assimilation and root respiration in 3-year-old seedlings of Quercus crispula and Fagus crenata, which are commonly the dominant tree species in deciduous broad-leaved forests in Japan, in full-sun and in the dark. Net assimilation rates followed a diurnal pattern in both species, with a marked decline in the morning that corresponded to a rapid increase in photosynthetic photon flux density, an increase in leaf temperature, and a vapor pressure deficit. Similarly, root respiration rates in both species decreased around noon in the sun treatment, although the soil temperature continued to increase. Seedlings in the sun treatment had significantly higher rates of root respiration than seedlings that were kept in the dark. Our results suggest that the midday depression of leaf assimilation could lead to downward transport of photosynthetic products, causing a midday depression in root respiration on a diurnal time scale. Furthermore, the effects of changes in the assimilated carbon supply on root respiration are likely to vary with light conditions experienced by leaves.

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.

Comparative phylogeography of four component species of deciduous broad-leaved forests in Japan based on chloroplast DNA variation

A phylogeographic study of four tree species (Padus grayana, Euonymus oxyphyllus, Magnolia hypoleuca, and Carpinus laxiflora) growing in Japanese deciduous broad-leaved forests was conducted based on chloroplast DNA (cpDNA) variations. Using nucleotide sequences of 702-1,059 bp of intergenic spacers of cpDNA, 20, 27, eight, and eight haplotypes were detected among 251, 251, 226, and 262 individuals sampled from 67, 79, 75, and 71 populations of the above species, respectively. The geographical pattern of the cpDNA variations was highly structured in each species, and the following three regional populations were genetically highly differentiated among all four species: (1) the Sea of Japan-side area, (2) the Kanto region, and (3) southwestern Japan. Based on some interspecific similarities among the phylogeographic patterns, the following migration scenario of Japanese deciduous broad-leaved forests was postulated. During the last glacial maximum (LGM), the forests were separately distributed in six regions. After LGM, as the climate warmed, the forests in eastern Japan separately expanded from each of the refugia along the Sea of Japan-side or along the Pacific Ocean-side. In contrast, those in southwestern Japan retreated and moved to high altitudes from each of the continuous forests.

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.

Scaling‐up technique for net ecosystem productivity of deciduous broadleaved forests in Japan using MODIS data

AbstractWe attempted to obtain carbon sequestration maps of deciduous forests in Japan using detectable parameters from the Moderate Resolution Imaging Spectrometer (MODIS) sensor and to determine how the spatial pattern of carbon sequestration differs within the same forest ecosystem type. For this investigation, we firstly parameterized the MODIS algorithm at one flux tower site, Takayama, for the years 2002–2003. The MODIS algorithm could link flux‐based net ecosystem productivity (NEP) with simple functions controlled by a thermal infrared band and a vegetation index. Second, the performance of the MODIS algorithm was validated through comparisons with the flux‐based NEP at another flux tower site, Hitsujigaoka. The MODIS‐based NEP at Hitsujigaoka was also within an accuracy of a flux‐based NEP with R2 of 0.879 and root mean square error of 1.64 gC m−2 day−1, regardless of canopy structure and age. The MODIS algorithm was noteworthy for its general applicability in different locations. Finally, we used the MODIS algorithm for the same forest ecosystem type in Japan for regional extrapolation of NEP. The MODIS‐based NEP of deciduous forests in Japan showed great variance with 347 ± 288 gC m−2 year−1 in 2002, according to the stand structure and climatic condition of the year. Studies for quantification of ecosystem carbon balance need to consider variance, frequency and spatial distributions of NEP. Satellite remote sensing demonstrated the potential for the large‐scale mapping of NEP.

Separation of soil respiration into CO2 emission sources using 13C natural abundance in a deciduous broad-leaved forest in Japan

In determining the soil and ecosystem carbon balance, it is necessary to distinguish between autotrophic respiration and heterotrophic respiration. We attempted to measure the contribution of CO2 emissions from plant roots (RRHI), from soil organic matter (RSOM), and from litter (RL) to CO2 emissions from the forest floor (soil respiration; RS) in a deciduous forest of oak (Quercus serrata Thunb.) and hornbeams (Carpinus laxiflora Sieb. et Zucc. Bl., Carpinus tschonoskii Maxim. and Carpinus japonica Bl.) on Andosols in Japan, using a 13C natural abundance technique. The 13C natural abundances of roots (δRHI), litter (δL) and SOM (δSOM) in the surface soil were −28.9, −30.1 and −24.3‰, respectively. This means that the differences between δSOM and δRHI are large enough to calculate the contributions of RRHI, RSOM and RL to RS based on the mass balance of the CO2 isotope ratios. RRHI and RSOM had close relationships with soil temperature, and RL was influenced by soil temperature and moisture. In summer, under high soil temperatures, RRHI and RSOM were the predominant sources of RS and the proportion of RRHI to RSOM to RL was 51:44:5. In winter, RL was predominant and the proportion of RRHI to RSOM to RL was 20:11:69. The estimated annual emissions of RRHI, RSOM and RL were 1.45, 2.10 and 1.30 Mg C ha−1, respectively; thus, the proportion of RRHI to RSOM to RL was 30:43:27 on a whole-year basis.

Intraspecific sequence variation of chloroplast DNA among the component species of deciduous broad-leaved forests in Japan

To select appropriate plant materials for a phylogeography of deciduous broad-leaved forests in Japan, we surveyed intraspecific chloroplast DNA variation in 34 species found in these forests. A relatively large number of intraspecific cpDNA variations were detected in ten species: Carpinus japonica (nucleotide diversity pi=0.00083), C. laxiflora (pi=0.00221), Magnolia obovata (pi=0.00134), Lindera triloba (pi=0.00255), L. obtusiloba (pi=0.00289), Pourthiaea villosa var. leavis (pi=0.00263), Acer japonicum (pi=0.00170), A. micranthum (pi=0.00237), Euonymus oxyphyllus (pi=0.00322) and Styrax obassia (pi=0.00100).

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.

Leaf-fall phenology along a topography-mediated environmental gradient in a cool—temperate deciduous broad-leaved forest in Japan

Leaf-fall phenology was studied in a cool—temperate deciduous broad-leaved forest in central Japan in relation to the topographic environmental gradients that occur along a short mountain slope. Leaf-fall phenology was described quantitatively using data from leaf litter collected along the slope. In autumn, leaf fall at the study site tended to occur slightly earlier on the upper slope than on the lower slope. This pattern was found at both the stand and the species levels. Our results suggest that leaf-fall phenology may be affected by difference in microclimatic conditions, because environmental conditions are thought to be more severe on the upper slope than on the lower slope. The less intensive methods used in this study, the litter trap method, and Dixon's model succeeded in quantifying the phenological patterns of leaf fall within stands and within species along the short mountain slope.