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Solute transport in a narrow space is the most elemental process in chromatography and biological pattern formation. However, the observation of such transport has been quite difficult, and theoretical investigations have therefore preponderated. Here, using a space- and time-resolved surface plasmon resonance (SPR) method, we measured the nanoscale near-wall (next to the wall) transport rate in a narrow channel after a solution and its solvent had come into contact. By combining the SPR method with a capillary injection method, which enables two solution plugs to flow immediately after they have made contact, we were able to measure the solute concentration evolution at the channel wall. We tested three combinations of two plugs of solution-water-glucose, sodium chloride-water, and glucose-sodium chloride-and succeeded in measuring diffusion-coefficient-dependent changes in the concentration of solute flowing through a rectangular microchannel in less than 0.4 s. A numerical analysis of this system revealed the acceleration of the solute/solution boundary moving on the wall and its deceleration at the center of the channel cross section. The observed experimental transport rate agreed with the numerical result quantitatively. These results show that the solute transport followed a laminar flow with a no-slip model and that the molecules were transported in the order of their diffusivity. In the third combination, when the two solutions made contact and started flowing, the interdiffusion of the solutes resulted in temporal concentrations lower than either of the solutions before contact, which indicated that the contact between the two solutions quickly led to separation by the advection-diffusion processes. We found that such a concentration profile could actually be measured. Our techniques are simple and applicable to a wide range of molecules; the method opens the way to direct observation of the space-time near-wall solute transport process and can be used for the rapid determination of diffusivity.

Amendment by biochar made by thermal degradation of biomass is expected to enhance carbon sequestration through stimulating carbon assimilation by plants. We clarified the effect of biochar amendme...

Differences in dominant tree species affect ecosystem carbon budgets in forests, but their independent impacts have not been fully recognized. We aimed to clarify the interannual variation in net p...

The role of biochar in the mitigation of CO2 emissions has been extensively studied in agricultural soils but is not well understood in Japanese forest soils, especially in relation to CO2 emission...

Soil carbon dioxide emission: soil respiration is representing a major contributor of accumulating carbon dioxide in the atmosphere that aids to accelerate global warming and altering the climate. Soil temperature, soil water content, sun light and vegetation are considered most common regulators of soil respiration variations in ecosystem. The soil respiration was measured in grassland intended to examine how the soil respiration changed with varying climatic factors, for two years (2015 and 2016) in temperate grassland of Annapurna Conservation Area (ACA), Nepal. In the study, soil temperature accounted exponential function of soil respiration variation at 42.9%, 19.1% and 23.3%, and temperature sensitivity of the soil respiration (Q10) obtained at 6.2, 1.4 and 1.8 in October 2015 and April 2016 and both the measurements were combined, respectively. Significant negative (R2 = 0.50, p < 0.05, October 2015) and positive (R2 = 0.084, p < 0.05, April 2016) exponential function of soil respiration and soil water content were determined, where high soil respiration values were always measured between 30% and 35% of the soil water content. However, linear significant relationship was determined (R2 = 0.376, p < 0.05) between soil respiration and photosynthetic photon flux density (PPFD). Soil respiration value averaged in October 2015 was 357 mg CO2 m-2 h-1 and in April 2016 it was 444.6 mg CO2 m-2 h-1. Above- and below-ground plant biomasses were obtained at 231.1 g d w m-2 and 1538.8 g d w m-2 in October, and at 449.9 g d w m-2 and 349.0 g d w m-2 in April, respectively. This study showed variation of soil respiration in relation to the factors such as soil temperature, soil water content and photosynthetic photon flux density signifying their importance in governing ecosystem function and carbon balance of the temperate grassland ecosystem.

Few studies have evaluated the application of biochar to forest ecosystems and their responses under field conditions. We manually spread grounded biochar on the forest floor, at rates of 0 (control), 5, and 10 Mg ha&minus, 1 (C0, C5 and C10, respectively), of an oak forest in central Japan to test the effects of biochar on tree growth and productivity. The relative growth rate of the diameter at breast height (dbh) of canopy oak trees (dbh &gt, 20 cm) significantly increased in C10 compared with that of the control (C0), but not in C5, in the second to third years after application. Despite the increasing growth rate of canopy trees, foliage production (NPPF) and woody production (NPPW) did not respond to biochar application. Conversely, the production of reproductive organs (NPPR, mainly oak acorns) increased in line with the biochar application rate gradients (1.04 &plusmn, 0.09 Mg ha&minus, 1 yr&minus, 1 in C0, 1.30 &plusmn, 0.08 Mg ha&minus, 1 in C5, and 1.47 &plusmn, 0.13 Mg ha&minus, 1 in C10). Since the contribution of NPPR to total NPP was fairly small, there were no significant differences in total NPP (=NPPW + NPPF + NPPR) for C5 (14.57 &plusmn, 0.20 Mg ha&minus, 1) or C10 (16.11 &plusmn, 0.73 Mg ha&minus, 1) compared with the control (15.07 &plusmn, 0.48 Mg ha&minus, 1).

The variation in CO2 flux from the forest floor is important in understanding the role of mangrove forests as a carbon sink. To clarify the effects of soil temperature and tidal conditions on variation in CO2 flux, sediment–atmosphere CO2 fluxes were measured between June 2012 and May 2013. We used the closed chamber method for two plots, with a 0.5 m difference in elevation (B, high elevation; R-B, low elevation), in a mangrove forest in south-western Japan. CO2 fluxes were highest in the warm season and showed a weak positive correlation with soil temperature in both forests. Estimated monthly CO2 flux showed moderate seasonal variation in accordance with the exposure duration of the soil surface under tidal fluctuation. Additionally, measured CO2 flux and soil temperature were slightly higher in the R-B plot than the B plot, although estimated annual CO2 flux was higher in the B plot than the R-B plot due to different exposure durations. These results suggest that variation in the exposure duration of the forest floor, which changes seasonally and microgeographically, is important in evaluating the annual CO2 flux at a local scale and understanding the role of mangrove ecosystems as regulators of atmospheric CO2.

The effect of the sintering temperature of Ce3+-doped Lu3Al5O12 (Ce-LuAG) phosphors on the emission and properties of the crystal structure was studied. A cathodoluminescence peak at 317 nm, which was assigned to lattice defects, was exhibited in addition to emission peaks at 508 and 540 nm for the Ce-LuAG phosphors. The intensities of the 317 nm emission peak for the phosphors with mean particle diameters of 5.0 and 10.0 µm formed at a low sintering temperature of 1430 °C were higher than those for the phosphors with mean particle diameters of 18.0 and 20.5 µm formed at a high sintering temperature of 1550 °C. In contrast, the electroluminescence spectra for fabricated white-light-emitting diodes (LEDs) using the phosphors revealed that the intensity of the peak at 540 nm was strong for the mean particle diameters of 18.0 and 20.5 µm. The intensity of the 540 nm peak, which is attributed to the 4f→5d transition of the Ce3+ activator, showed a dependence on the sintering temperature. The relationship between the optical properties and the lattice defects is discussed.

The chamber method with plant clipping has been widely used for measuring soil respiration (SR) in grassland ecosystems. However, plant clipping may cause overestimation of SR by changing the environmental factors and injuring the plants. To solve these problems, we developed a new non-destructive method using multiple-microchambers (3 cm diameter, 8 cm height), which enables measurement of SR without plant clipping by installing chambers into gaps among the grasses. The new method was compared with the conventional method at various flow rates in vitro to assess the accuracy of SR measurement. The new method overestimated the SR rate; however, the ratio of overestimation to the conventional method was constant for each flow rate. These ratios fitted the logarithmic curve, indicating the potential for correction of the SR rate measured by the new method using the logarithmic equation. The corrected SR rate obtained by the new method was equal to the rate by the conventional method. This suggests that accurate measurement of SR in grassland ecosystems is possible using the multiple-microchambers method. We then compared the non-destructive method and the destructive method in situ on summer season and found that the destructive method overestimated SR rate in the grassland ecosystem by about 276% on average. There were two possible reasons for this overestimation; first, the clipping treatment may change environmental conditions such as soil temperature and soil water content, and second, it may directly increase plant respiration.

We examined two hypotheses based on laboratory amendment experiments: (1) that development of the soil microbial community on volcanic deserts was regulated by substrate limitation; and (2) that the type and the extent of substrate limitation would change along the succession gradient. Soils were collected from the early (Stage B) and the late (Stage F) stages of primary succession of a subalpine volcanic desert on Mt. Fuji and they were amended with three carbon (C) sources (glucose, cellulose, or lignin), inorganic nitrogen (N), or phosphorus (P) sources alone or in a mixture. Respiration rates were monitored for 25 days and changes in microbial biomass and community structure were examined using the content and composition of phospholipid fatty acids. For both soils, the magnitude of the microbial response differed depending on the type of C source and it decreased in the following order reflecting the availability to microorganisms: glucose > cellulose > lignin. For Stage B soil, although any single amendment did not affect the microbial properties, combined amendment of C (glucose) and N increased microbial respiration and biomass and shifted the microbial community structure. In contrast, microbial properties in Stage F soils responded positively to single amendments of C source. Our results suggest that the microbial community in the early stage of succession is primarily limited by simultaneous shortage of C and N sources but the quality of the C source becomes more important in the late successional stages, which have large, but recalcitrant, organic matter pools in the soil.

To quantify the contribution of soil moisture to seasonal and annual variations in soil CO2 efflux in a cool-humid deciduous broadleaf forest, we measured soil CO2 efflux during the snow-free seasons of 2005–2008 using an automated chamber technique. This worked much better than manual chambers employing the same steady-state through-flow method. Soil CO2 efflux (g C m−2 period−1) during the snow-free season ranged from 979.8 ± 49.0 in 2005 to 1131.2 ± 56.6 in 2008 with a coefficient variation of 6.4 % among the 4 years. We established two-parameter (soil temperature and moisture) empirical models, finding that while soil temperature and moisture explained 69–86 % and 10–13 % of the temporal variability, respectively. Soil moisture had the effect of modifying the temporal variability of soil CO2 efflux, particularly during summer and early fall after episodic rainfall events; greater soil moisture enhanced soil CO2 efflux in the surface soil layers. High soil moisture conditions did not suppress soil CO2 efflux, leading to a positive correlation between normalized soil CO2 efflux (ratio of the measured to predicted efflux using a temperature-dependent Q 10 function) and soil moisture. Therefore, enhanced daily soil CO2 efflux following heavy rainfall events could significantly reduce net ecosystem exchange (i.e. daily net ecosystem production) by 32 % on some days. Our results highlight the importance of precisely estimating the response of soil CO2 efflux to changes in soil moisture following rainfall events when modeling seasonal carbon dynamics in response to climate change, even in humid monsoon regions.

Soil organic layer samples of two different forest types were observed using compact MRI to visualize internal structure and clarify physical properties of forest soil. Soil pores and organic materials were distinguished by differences in proton mobility and visualized with a spatial resolution of 234 µm. Soil pore ratios and water mobility were calculated by image processing, and their differences between the two forest soils were detected. Our results suggest that compact MRI has potential for non-destructive analysis of soil physical properties and is expected to have significant applications in ecological studies.

The ecological effects of management treatments on the carbon cycles of secondary forests remain poorly understood. Here, we compared carbon cycles at three sites, a managed understory harvesting site (UH), a managed understory harvesting and litter raking site (LR), and an unmanaged site that served as a control (Um). We considered the harvests of understory and litter biomass as bioenergy sources, and made compartment models for the carbon cycle in units of carbon. Management increased the net primary production from 6.7 tC ha−1 year−1 for the Um site to 7.2 tC ha−1 year−1 for the UH site and 7.8 tC ha−1 year−1 for the LR site. Concurrently, management reduced the decomposition rate from 5.1 tC ha−1 year−1 for the Um site to 3.7 tC ha−1 year−1 for the UH site and 3.8 tC ha−1 year−1 for the LR site. Management also reduced fossil fuel use by 0.7 tC ha−1 year−1 for the UH site and 3.5 tC ha−1 year−1 for the LR site. These values suggest that harvesting had positive effects on net ecosystem production (NEP). In contrast, bioenergy use released 1.3 tC ha−1 year−1 into the atmosphere (in the form of carbon dioxide) for the UH site and 6.9 tC ha−1 year−1 for the LR site. These values suggest that harvesting had negative effects on NEP. We conclude that understory harvesting without litter raking (UH) maximized NEP at 2.9 tC ha−1 year−1. Our findings underscore the importance of a balanced ecological approach to forest management.

We studied interannual variations in single-leaf phenology, i.e., temporal changes in leaf ecophysiological parameters that are responsible for forest canopy function, in a cool-temperate deciduous broadleaf forest at Takayama, central Japan. We conducted long-term in situ research from 2003 to 2010 (excluding 2008). We measured leaf mass per unit area (LMA), leaf chlorophyll and nitrogen contents, and leaf photosynthetic and respiratory characteristics [dark respiration, light-saturated photosynthetic rate (A max), maximum carboxylation rate (V cmax), and electron transport rate (J max)] of leaves of mature canopy trees of Betula ermanii Cham. and Quercus crispula Blume, from leaf expansion to senescence. All leaf characteristics changed markedly from leaf expansion (late May) through senescence (mid–late October). The photosynthetic capacity of B. ermanii leaves rapidly increased during leaf expansion and decreased during senescence, while that of Q. crispula leaves changed gradually. The relationships among LMA, photosynthetic capacity, and nitrogen content changed throughout the season. The timings (calendar dates) of leaf expansion, maturity, and senescence differed among the 7 years, indicating that interannual variations in micrometeorological conditions strongly affected leaf phenological events. We examined the seasonal changes as a function of the date or cumulative air temperatures. From leaf expansion to maturity, the increases in chlorophyll content, A max, V cmax, J max, and LMA were explained well by the growing-degree days, and their decreases in autumn were explained well by chilling-degree days. Our findings will be useful for predicting the effects of current variations in climatic conditions and future climate change on forest canopy structure and function.

An adaptive Kalman filter-based fusion algorithm capable of estimating respiration rate for unobtrusive respiratory monitoring is proposed. Using both signal characteristics and a priori information, the Kalman filter is adaptively optimized to improve accuracy. Furthermore, the system is able to combine the respiration-related signals extracted from a textile ECG sensor and an accelerometer to create a single robust measurement. We measured derived respiratory rates and, when compared to a reference, found root-mean-square error of 2.11 breaths-per-minute (BrPM) while lying down, 2.30 BrPM while sitting, 5.97 BrPM while walking, and 5.98 BrPM while running. These results demonstrate that the proposed system is applicable to unobtrusive monitoring for various applications.

Carbon sequestration and carbon emission are processes of ecosystem carbon cycling that can be affected while land area converted to grassland resulting in increased soil carbon storage and below-ground respiration. Discerning the importance of carbon cycle in grassland, we aimed to estimate carbon sequestration in photosynthesis and carbon emission in respiration from soil, root, and microbes, for four consecutive years (2007–2010) in a warm-season perennial grassland, Japan. Soil carbon emission increased with increasing growing season temperature which ranged from 438 to 1642 mg CO2 m−2 h−1. Four years’ average soil carbon emission for growing season, nongrowing season, and annual emission was 1123, 364, and 1488 g C m−2, respectively. Nongrowing and snow covered season soil carbon emission contributed 23–25% and 14–17% to the annual emission. Above-ground biomass varied seasonally and variation in green biomass affected soil carbon emission with increasing temperature and precipitation. Temperature effect on root carbon emission contributed about 1/4th of the total soil carbon emission. Variation in soil and root carbon emission is affected by below-ground biomass. Long-term estimation concluded that seasonal and interannual variations in carbon sequestration and emission are very common in grassland ecosystem.

To assess soil microbial response to global warming in cool temperate semi-natural grassland, we conducted an in situ warming experiment in grassland located in the mountains of central Japan. Five pairs of plots (control and warmed) of Zoysia japonica were established. For each pair of plots, one was warmed by ca. 2 °C using infrared heaters during the growing seasons of 2009–2011. Above-ground biomass of Z. japonica was estimated using the modified point-frame method. Soil organic matter contents, soil total carbon and nitrogen contents, as well as inorganic nitrogen (ammonium and nitrate) contents were determined from soil samples. Total phospholipid fatty acid (PLFA) contents and PLFA compositions were determined and used as indices for total microbial biomass and community structure, respectively. Analyses showed that the warming increased the above-ground biomass of Z. japonica significantly. Soil organic matter and soil total nitrogen contents were significantly decreased, while soil ammonium content was significantly increased in the warmed plots. Soil microbial biomass (especially fungal biomass) was lower in the warmed plots, probably reflecting higher temperature, lower soil water content, and/or depletion in available nutrients. The significant decrease in fungal biomass, in combination with our PLFA composition data, suggests that the soil microbial community structure shifted from a fungal-dominated to a bacteria-dominated one, causing changes in community-level physiological activity.

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.

Livestock dung provides an important direct pathway by which carbon and nutrients enter soils in pasture ecosystems and affects carbon and nitrogen cycling indirectly through changes in soil and plant properties. Here, we quantify dung deposition, decomposition, and the effects of dung on soil and plants in a Zoysia japonica grassland in Japan. We determined (1) the distribution of dung, (2) the mass loss rate of dung and the amount of carbon respired as CO2, and (3) changes in soil properties and aboveground biomass of Z. japonica. Dung deposition was 4.0–9.7 g C and 0.4–1.0 g N m−2 year−1 and distributed patchily (Morishita’s I δ > 1). Most (71 %) of the carbon in dung deposited in June was lost within a single grazing period by aerobic decomposition, more than mass loss rate of Z. japonica litter in the first year (about 50 %), suggesting that grazing and defecation can accelerate carbon cycling compared with the typical litterfall–decomposition regime. Nitrogen in dung mass entered the soil as ammonium nitrogen and was nitrified. The spatiotemporal distribution of these processes corresponded to that of stimulated Z. japonica growth. These results suggested that dung deposition significantly affected the inorganic nitrogen status of soil and, therefore, the growth of Z. japonica. However, these effects were very restricted temporally (July–August) and spatially (within 10 cm from dung edge). Thus, such spatiotemporally restricted effects combined with the patchy distribution of dung may contribute to the heterogeneous structure of pasture ecosystems.

Coarse woody debris (CWD) is an important component of the forest carbon cycle, acting as a carbon pool and a source of CO2 in temperate forest ecosystems. We used a soda-lime closed-chamber method to measure CO2 efflux from downed CWD (diameter ≥5 cm) and to examine CWD respiration (RCWD) under field conditions over 1 year in a temperate secondary pioneer forest in Takayama forest. We also investigated tree mortality (input to the CWD pool) from the data obtained from the annual tree census, which commenced in 2000. We developed an exponential function of temperature to predict RCWD in each decay class (R2 = 0.81–0.97). The sensitivity of RCWD to changing temperature, expressed as Q10, ranged from 2.12 to 2.92 and was relatively high in decay class III. Annual C flux from CWD (FCWD) was extrapolated using continuous air temperature measurements and CWD necromass pools in the three decay classes. FCWD was 3.0 (class I), 17.8 (class II), and 13.7 g C m−2 year−1 (class III) and totaled 34 g C m−2 year−1 in 2009. Annual input to CWD averaged 77 g C m−2 year−1 from 2000 to 2009. The budget of the CWD pool in the Takayama forest, including tree mortality inputs and respiratory outputs, was 0.43 Mg C ha−1 year−1 (net C sink) owing to high tree mortality in the mature pioneer forest. The potential CWD sink is important for the carbon cycle in temperate successional forests.

At the Takayama deciduous broadleaved forest Asiaflux site in Japan, the ecosystem carbon dynamics have been studied for more than two decades. In 2005, we installed non-dispersive infrared CO2 sensors in the soil below the site’s flux tower to systematically study vertical soil–air CO2 dynamics and explain the behavior of soil surface CO2 efflux. Soil–air CO2 concentrations measured from June 2005 through May 2006 showed sinusoidal variation, with maxima in July and minima in winter, similar to the soil CO2 effluxes measured simultaneously using open-flow chambers. Soil–air CO2 concentrations increased with soil depth from 5 to 50 cm: from 2,000 to 8,000 ppm in the summer and from 2,000 to 3,000 ppm in the winter under snow. Summer soil–air CO2 concentrations were positively correlated with soil moisture on daily and weekly scales, indicating that the Oi, Oe, and A horizons, where decomposition is accelerated by high-moisture conditions, contributed substantially to CO2 emissions. This result is consistent with the short residence time (about 2 h) of CO2 in the soil and larger emissions in shallow soil layers based on our diffusion model. We revealed for the first time that soil–air CO2 concentrations in winter were correlated with both snow depth and wind speed. CO2 transfer through the snow was hundreds of times the gas diffusion rates in the soil. Our estimate of the CO2 efflux during the snow-cover season was larger than previous estimates at TKY, and confirmed the important contribution of the snow-cover season to the site’s carbon dynamics.

Trenching (Tr), root biomass regression (RR), and root excising (RE) methods were used to estimate the contribution of root (RR) and heterotrophic (HR) respiration to soil respiration (SR) in a cool-temperate deciduous forest in central Japan. The contribution ratios of RR to SR were 23 % (−16 to 46 %), 11 % (−19 to 61 %), and 115 % (20 to 393 %), as estimated by the Tr, RR, and RE methods, respectively. The contribution ratio showed clear seasonal variation with high values in summer for the Tr method, while they were undetectable for the RR and RE methods because of some methodological problems. These results suggest the Tr method is the best of the three methods used to estimate the contribution ratio of RR and HR to SR in the forest. Annual SR, RR, and HR rates, estimated by the Tr method, were 479, 369, 110 gC m−2 year−1, respectively. The seasonal variation of SR was mainly influenced by HR (77 %) throughout the year, while the influence of RR on SR was strongest in summer (46 %). This effect occurred because RR (Q 10 = 7.5) is more sensitive to temperature than HR (Q 10 = 3.2). Also, the contribution of fine RR to total RR was higher than that of coarse RR because of high respiratory activity (Q 10 and R 10) as well as the large biomass of fine roots. These results suggest that each component of SR responds differently to the same environmental factors and their relative influence on SR changes across the seasons.

A technique to improve sensitivity of the CW photoacoustic spectroscopy has been developed and verified by measuring absorbance of water at different temperatures. The technique utilizes coupling between acoustic standing waves or acoustic resonant modes and the photoacoustic source distribution in the sample. By choosing proper acoustic resonant mode, the sensitivity can be enhanced approximately fivefold. The results imply that the method can be applied to low levels of glucose for non-invasive monitoring.

We demonstrate the detection of physiological-range glucose in a multicomponent aqueous solution through multivariate analysis of broadband dielectric spectra from 500 MHz to 50 GHz. To enhance the selectivity to glucose, we applied spectral preprocessing on dielectric spectra to extract the feature values of glucose and bovine serum albumin (BSA). Using the regression models derived from different concentrations of glucose and BSA, the analysis was carried out on the solutions with the physiological range of both components. The prediction error of glucose concentration was estimated at less than 73 mg/dL even in various concentrations of BSA. This technique is easily implemented with a microwave blood glucose sensor or in other biomedical applications that essentially require multicomponent analysis.