Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Katayama Ayumi Last modified date:2020.06.03

Assistant Professor / Department of Agro-environmental Sciences / Faculty of Agriculture


Papers
1. Mioko Ataka, Lijuan Sun, Tatsuro Nakaji, Ayumi Katayama, Tsutom Hiura, Five-year nitrogen addition affects fine root exudation and its correlation with root respiration in a dominant species, Quercus crispula, of a cool temperate forest, Japan, Tree physiology, 10.1093/treephys/tpz143, 40, 3, 367-376, 2020.01.
2. Izuki Endo, Tomonori Kume, Lip Khoon Kho, Ayumi Katayama, Naoki Makita, Hidetoshi Ikeno, Junichiro Ide, Mizue Ohashi, Spatial and temporal patterns of root dynamics in a Bornean tropical rainforest monitored using the root scanner method, Plant and Soil, 10.1007/s11104-019-04203-w, 443, 1-2, 323-335, 2019.08, Aims: Root phenology patterns in tropical regions are poorly understood because limited data are available. Using the root scanner method, the aims of this study were to clarify 1) the temporal phenology of root production and decomposition, 2) the spatial variability of the root phenology, and 3) the contribution of different root diameter classes to root production and decomposition. Methods: Image acquisition was conducted monthly from April 2014 to May 2015 at five sites in a Bornean tropical rainforest. The projected area and length of root production and decomposition were derived manually from images using image-processing software and were grouped into 0.5-mm-diameter intervals. Results: The spatial distribution of root production and decomposition differed among the sites. Monthly projected root length indicated that the number and timing of peak root production and decomposition differed with each site. A substantial proportion of root production and decomposition was dominated by very fine roots (<0.5 mm diameter). Conclusions: The scanner method was useful to monitor the root phenology at the root system scale though the scanner images cover only a portion of the root systems of mature trees. Different patterns of root phenology among the sites might be associated with the high diversity and the indistinct seasonality of the Bornean tropical rainforest..
3. Ayumi Katayama, Tomonori Kume, Ryuji Ichihashi, Michiko Nakagawa, Vertical variation in wood CO2 efflux is not uniformly related to height
measurement across various species and sizes of Bornean tropical rainforest trees, Tree physiology, 10.1093/treephys/tpz022, 39, 6, 1000-1008, 2019.06, Limited knowledge about vertical variation in wood CO2 efflux (Rwood) is still a cause of uncertainty in Rwood estimates at individual and ecosystem scales. Although previous studies found higher Rwood in the canopy, they examined several tree species of similar size. In contrast, in the present study, we measured vertical variation in Rwood for 18 trees including 13 species, using a canopy crane for a more precise determination of the vertical variation in Rwood, for various species and sizes of trees in order to examine the factors affecting vertical variation in Rwood and thus, to better understand the effect of taking into account the vertical and inter-individual variation on estimates of Rwood at the individual scale. We did not find any clear pattern of vertical variation; Rwood increased significantly with measurement height for only one tree, while it decreased for two more trees, and was not significantly related with measurement height in 15 other trees. Canopy to breast height Rwood ratio was not related to diameter at breast height or crown ratio, which supposedly are factors affecting vertical variation in Rwood. On average, Rwood estimates at individual scale, considering inter-individual variation but ignoring vertical variation, were only 6% higher than estimates considering both forms of variation. However, estimates considering vertical variation, while ignoring inter-individual variation, were 13% higher than estimates considering both forms of variation. These results suggest that individual measurements at breast height are more important for estimating Rwood at the individual scale, and that any error in Rwood estimation at this scale, due to the absence of any more measurements along tree height, is really quite negligible. This study measured various species and sizes of trees, which may be attributed to no clear vertical variation because factors causing vertical variation can differ among species and sizes..
4. Mizue Ohashi, Naoki Makita, Ayumi Katayama, Tomonori Kume, Kazuho Matsumoto, Tomo’omi Kumagai, Izuki Endo, Lip Khoon Kho, Characteristics of root decomposition based on in situ experiments in a tropical rainforest in Sarawak, Malaysia
impacts of root diameter and soil biota, Plant and Soil, 10.1007/s11104-018-03929-3, 436, 1-2, 439-448, 2019.03, Aims: Tropical forests contribute significantly to the stability of global carbon (C) balance; however, little is known about root litter decomposition in tropical rainforests. In this study, we aimed to (1) characterise the effect of soil depth, root diameter and soil organisms on root litter decomposition and (2) estimate the contribution of root decomposition to soil carbon dioxide (CO
2
) efflux in a tropical rainforest in Malaysian Borneo. Methods: We incubated soil chambers with fine and coarse root litterbags at varying soil depths. Soil chambers were covered with nets of different mesh sizes, and CO
2
efflux was monitored from the top of each soil chamber during the incubation. Results: Our results showed that coarse roots decomposed faster than fine roots. There was no impact of soil depth, but soil animals and fungi had a significant impact on coarse root decomposition from 398 days after the start of the experiment. Soil CO
2
efflux increased linearly with C loss from root decomposition, indicating that 40% of the CO
2
efflux originates from root litter. Conclusions: The variation in root decomposition rates suggests the possible role of root litter in soil C storage and emission in a tropical rainforest..
5. Ayumi Katayama, Lip Khoon Kho, Naoki Makita, Tomonori Kume, Kazuho Matsumoto, Mizue Ohashi, Estimating fine root production from ingrowth cores and decomposed roots in a Bornean tropical rainforest, Forests, 10.3390/f10010036, 10, 1, 2019.01, Research highlights: Estimates of fine root production using ingrowth cores are strongly influenced by decomposed roots in the cores during the incubation period and should be accounted for when calculating fine root production (FRP). Background and Objectives: The ingrowth core method is often used to estimate fine root production; however, decomposed roots are often overlooked in estimates of FRP. Uncertainty remains on how long ingrowth cores should be installed and how FRP should be calculated in tropical forests. Here, we aimed to estimate FRP by taking decomposed fine roots into consideration. Specifically, we compared FRP estimates at different sampling intervals and using different calculation methods in a tropical rainforest in Borneo. Materials and Methods: Ingrowth cores were installed with root litter bags and collected after 3, 6, 12 and 24 months. FRP was estimated based on (1) the difference in biomass at different sampling times (differential method) and (2) sampled biomass at just one sampling time (simple method). Results: Using the differential method, FRP was estimated at 447.4 ± 67.4 g m
-2
year
-1
after 12 months, with decomposed fine roots accounting for 25% of FRP. Using the simple method, FRP was slightly higher than that in the differential method after 12 months (516.3 ± 45.0 g m
-2
year
-1
). FRP estimates for both calculation methods using data obtained in the first half of the year were much higher than those using data after 12-months of installation, because of the rapid increase in fine root biomass and necromass after installation. Conclusions: Therefore, FRP estimates vary with the timing of sampling, calculation method and presence of decomposed roots. Overall, the ratio of net primary production (NPP) of fine roots to total NPP in this study was higher than that previously reported in the Neotropics, indicating high belowground carbon allocation in this forest..
6. Ayumi Katayama, Tsutomu Enoki, Tomonori Kume, Kyoichi Otsuki, Characteristics of soil respiration in upper and lower slope positions with different aboveground biomass
A case study in a Japanese cypress forest, J. AGRICULTURAL METEOROLOGY, 10.2480/agrmet.D-17-00019, 74, 2, 63-70, 2018.01, Differences in aboveground biomass alonga slope position are often overserved because of varyinglevels of nutrient availability. Such differences can affect the spatial variation in soil respiration (Rsoil) via changes in biological factors (e.g., fine root biomass and litter mass), in addition to environmental factors. This study clarified the differences in Rsoil and the factors affecting Rsoil, between the upper and lower slope positions with contrastingaboveground biomass, within a small watershed covered by a Japanese cypress forest. The soil water content (SWC) was lower, whereas the soil temperature (Tsoil) and fine root biomass were higher in the upper plot (UP) than in the lower plot (LP). Rsoil was negatively correlated with SWC, but positively correlated with Tsoil and fine root biomass. These results gave rise to a positive effect of Rsoil on the UP. However, Rsoil was comparable between the plots. The results from a multiple linear regression model indicated that factors other than SWC, Tsoil, and fine root biomass increased Rsoil in the LP. We speculate that high litterfall could enhance Rsoil in the LP, as litterfall is an important source of decomposed respiration. The higher aboveground net primary production and lower fine root biomass in the LP suggest that more carbon was allocated aboveground and less carbon was allocated belowground, resultingin comparable Rsoil but different contribution of aboveground and belowground sources on Rsoil between the plots. It is considered that differences in phosphorus availability between the plots caused the different carbon allocation patterns, even at a small spatial scale of less than 100 m..
7. Tomonori Kume, Mizue Ohashi, Naoki Makita, Lip Khoon Kho, Ayumi Katayama, Izuki Endo, Kazuho Matsumoto, Hidetoshi Ikeno, Image analysis procedure for the optical scanning of fine-root dynamics
Errors depending on the observer and root-viewing window size, Tree physiology, 10.1093/treephys/tpy124, 38, 12, 1927-1938, 2018.01, Clarifying the dynamics of fine roots is critical to understanding carbon and nutrient cycling in forest ecosystems. An optical scanner can potentially be used in studying fine-root dynamics in forest ecosystems. The present study examined image analysis procedures suitable for an optical scanner having a large (210 mm × 297 mm) root-viewing window. We proposed a protocol for analyzing whole soil images obtained by an optical scanner that cover depths of 0–210 mm. We tested our protocol using six observers with different experience in studying roots. The observers obtained data from the manual digitization of sequential soil images recorded for a Bornean tropical forest according to the protocol. Additionally, the study examined the potential tradeoff between the soil image size and accuracy of estimates of fine-root dynamics in a simple exercise. The six observers learned the protocol and obtained similar temporal patterns of fine-root growth and biomass with error of 10–20% regardless of their experience. However, there were large errors in decomposition owing to the low visibility of decomposed fine roots. The simple exercise revealed that a smaller root-viewing window (smaller than 60% of the original window) produces patterns of fine-root dynamics that are different from those for the original window size. The study showed the high applicability of our image analysis approach for whole soil images taken by optical scanners in estimating the fine-root dynamics of forest ecosystems..
8. Tomonori Kume, Kenji Tsuruta, Hikaru Komatsu, Yoshinori Shinohara, Ayumi Katayama, Junichiro Ide, Kyoichi Otsuki, Differences in sap flux-based stand transpiration between upper and lower slope positions in a Japanese cypress plantation watershed, Ecohydrology, 10.1002/eco.1709, 9, 6, 1105-1116, 2016.09, This study investigated the difference in stand transpiration (E) between upper (UP) and lower (LP) slope plots of a Japanese cypress (Chamaecyparis obtusa) watershed to obtain catchment-scale E estimates. Sap flux-based stand-scale E estimates were conducted on the UP and LP, which had contrasting stand structures (diameter at breast height and tree height) despite being the same age. The plant area index was similar in the UP and LP, while the total sapwood area (AS_stand) and the mean sap flux density (JS) in the UP were 23% and ~30% lower, respectively, than those of the LP. Stand-scale E is the product of the AS_stand and JS in a stand. As a result, E in the UP was ~50% lower than that in the LP. This ratio was relatively constant throughout the year, which was supported by a similar decline in E, which resulted from soil water decline in the UP and LP. Canopy conductance (GC) in the UP was ~50% smaller than that of the LP. In contrast to previous studies that showed a consistent JS along a slope, the differences in E between the UP and LP were caused by differences in AS_stand and JS, probably because the UP exhibited a lower GC per unit leaf area than the LP. Additionally, evapotranspiration (ET), the sum of sap flux-scaled E plus rainfall interception, was 8–14% lower than the catchment water balance ET (precipitation minus runoff), which suggests the feasibility of calculating sap flux-scaled E for the two slope positions..
9. Chen Wei Chiu, Hikaru Komatsu, Ayumi Katayama, Kyoichi Otsuki, Scaling-up from tree to stand transpiration for a warm-temperate multi-specific broadleaved forest with a wide variation in stem diameter, Journal of Forest Research, 10.1007/s10310-016-0532-7, 21, 4, 161-169, 2016.08, Previous studies have demonstrated a clear relationship between diameter at breast height (DBH) and tree transpiration (QT) in multi-specific broadleaved forests. However, these studies were conducted with a limited range of tree sizes and species, and thus many multi-specific broadleaved forests fall outside these conditions. Therefore, this study examined the relationship between DBH and QT in a warm-temperate multi-specific broadleaved forest (n = 12 species) with a wide range of tree sizes (5.0–70.0 cm DBH) using the Granier-type heat dissipation method. The results showed that, although sap flow density varied between individual trees and species, there was a significant relationship between log QT and log DBH (r2 = 0.66, P < 0.001) because of the strong dependence of sapwood area on DBH. This study confirmed the applicability of the relationship for the stand transpiration (EC) estimates even in a multi-specific broadleaved forest with a wide variation in DBH. Our results also revealed that selecting the sample trees in descending order of DBH effectively reduced potential errors in EC estimates for a specific sample size, as larger trees contribute more to EC. This information should be useful for future studies investigating the transpiration of multi-specific broadleaved forests, reducing errors during the scaling-up procedure..
10. Katayama, A., Kume, T., Ohashi, M., Matsumoto, K., Nakagawa, M., Saito, T., Kumagai, T., Otsuki, K., Characteristics of wood CO2 efflux in a Bornean tropical rainforest, Agricultural and Forest Meteorology, 220, 15, 190-199, 2016.04.
11. Ayumi Katayama, Tomonori Kume, Mizue Ohashi, Kazuho Matsumoto, Michiko Nakagawa, Takami Saito, Tomo'omi Kumagai, Kyoichi Otsuki, Characteristics of wood CO2 efflux in a Bornean tropical rainforest, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2016.01.140, 220, 190-199, 2016.04, Wood CO2 efflux (Rwood) is an important carbon cycling process in forest ecosystems and is less understood in Bornean tropical rainforests compared with that in Neotropics, which have differing biotic and abiotic characteristics. Bornean tropical rainforests have particularly higher aboveground biomass because of high stand densities of tall emergent trees, and no regular seasonal dry period. These properties may reflect specific Rwood variation and higher annual Rwood at the ecosystem scale (annual-Rwood) in Borneo. Hence, in this study, we investigated factors that affect inter-individual variation in chamber-based Rwood on stem surfaces at breast height (chamber-Rwood) and estimated Rwood at the ecosystem scale (ecosystem-Rwood) in a Bornean tropical rainforest. Subsequently, we examined temporal variation in ecosystem-Rwood with environmental factors, estimated annual-Rwood, and then evaluated the effects of large trees on ecosystem-Rwood. Stem growth rates were the most significant predictor of inter-individual variation in chamber-Rwood during all five measurement periods between 2012 and 2014. Accordingly, stem growth rates allowed accurate estimates of ecosystem-Rwood, although chamber-Rwood varied with diameter at breast height (DBH) and tree species in some measurement campaigns. Ecosystem-Rwood decreased with soil moisture. Considering the inter-individual and temporal variation, annual-Rwood was estimated at 7.06 ± 2.09 MgC ha-1 year-1. This value was comparable to those determined in Neotropical forests, even though aboveground biomass in the present study site was approximately twice of those in Neotropical sites. Large trees with DBH >70 cm comprised 38% of aboveground biomass but accounted for only 23% of ecosystem-Rwood because of the small portion of woody tissue surface area of the large trees. These data indicate that the stand density of large trees can considerably affect aboveground biomass but exert less influence on variation in ecosystem-Rwood among various forests..
12. Masaaki Chiwa, Shoko Ikezaki, Ayumi Katayama, Tsutomu Enoki, Topographic Influence on Plant Nitrogen and Phosphorus Stoichiometry in a Temperate Forested Watershed, Water, Air, and Soil Pollution, 10.1007/s11270-015-2701-2, 227, 1, 2016.01, Plant stoichiometry has been used to diagnose phosphorus (P) limitation caused by increased atmospheric nitrogen (N) deposition. Spatial variability of N/P stoichiometry within a forested watershed has not yet been evaluated. This study conducted synoptic sampling of leaf matter in 27 plots within a temperate forested watershed on low P availability rock (serpentine bedrock) with a moderately high atmospheric N deposition (16 kg N ha-1 year-1) to assess the effects of spatial topographic variation on N/P stoichiometry. Leaf N and P concentrations and N/P ratios of Japanese cypress were assessed, and their spatial variations were evaluated across a catchment. Average leaf P concentration was low (0.66 ± 0.16 mg g-1) across the sites, while leaf N concentration was high (13.0 ± 1.5 mg g-1); subsequently, N/P ratios were high (21 ± 5). In addition, the aboveground biomass growth of Japanese cypress positively correlated with litter P, implying the P limitation of Japanese cypress at the study site. Leaf P concentrations responded to the index of convexity (IC) values more than those of N. Subsequently, the N/P ratio correlated with IC, suggesting that N/P ratios are susceptible to topographic features. This could be partly caused by smaller spatial variability of N availability compared with P, owing to increased atmospheric N deposition. Thus, topography should be taken into consideration when diagnosing P limitation caused by N deposition..
13. Kume T, Tsuruta K, Komatsu H, Shinohara Y, Katayama A, Ide J, Otsuki K., Differences in sap flux based stand transpiration between upper and lower slope positions in a Japanese cypress plantation watershed, Ecohydrology, 2015.12.
14. Ayumi Katayama, Tomonori Kume, Hikaru Komatsu, Mizue Ohashi, Kazuho Matsumoto, Ryuji Ichihashi, Tomo'Omi Kumagai, Kyoichi Otsuki, Vertical variations in wood CO2 efflux for live emergent trees in a Bornean tropical rainforest, Tree Physiology, 10.1093/treephys/tpu041, 34, 5, 503-512, 2014.05, Difficult access to 40-m-tall emergent trees in tropical rainforests has resulted in a lack of data related to vertical variations in wood CO2 efflux, even though significant variations in wood CO2 efflux are an important source of errors when estimating whole-tree total wood CO2 efflux. This study aimed to clarify vertical variations in wood CO2 efflux for emergent trees and to document the impact of the variations on the whole-tree estimates of stem and branch CO2 efflux. First, we measured wood CO2 efflux and factors related to tree morphology and environment for seven live emergent trees of two dipterocarp species at four to seven heights of up to ~40 m for each tree using ladders and a crane. No systematic tendencies in vertical variations were observed for all the trees. Wood CO2 efflux was not affected by stem and air temperature, stem diameter, stem height or stem growth. The ratios of wood CO2 efflux at the treetop to that at breast height were larger in emergent trees with relatively smaller diameters at breast height. Second, we compared whole-tree stem CO2 efflux estimates using vertical measurements with those based on solely breast height measurements. We found similar whole-tree stem CO2 efflux estimates regardless of the patterns of vertical variations in CO2 efflux because the surface area in the canopy, where wood CO2 efflux often differed from that at breast height, was very small compared with that at low stem heights, resulting in little effect of the vertical variations on the estimate. Additionally, whole-tree branch CO2 efflux estimates using measured wood CO2 efflux in the canopy were considerably different from those measured using only breast height measurements. Uncertainties in wood CO2 efflux in the canopy did not cause any bias in stem CO2 efflux scaling, but affected branch CO2 efflux..
15. Toyama H., Tagane S., Chhang P., Samreth V., Ma V., Sokh H., Kajisa T., Katayama A., Itadani H., Tateishi M., Tachiki Y., Sakata K., Ichihashi R., Onoda Y., Mizoue N, Tachida H. Yahara T., Inventory of Woody Flora in Permanent Plots of Kampong Thom and Kampong Chhnang Provinces, Camboria (Taxonomy of trees in permanent plots of Kampong Thom and Kampong Chhnang Provinces, Cambodia), 64, 45-105, 2013.08.
16. Ayumi Katayama, Tomonori Kume, Hikaru Komatsu, Taku M. Saitoh, Mizue Ohashi, Michiko Nakagawa, Masakazu Suzuki, Kyoichi Otsuki, Tomo'omi Kumagai, Carbon allocation in a Bornean tropical rainforest without dry seasons, Journal of Plant Research, 10.1007/s10265-012-0544-0, 126, 4, 505-515, 2013.07, To clarify characteristics of carbon (C) allocation in a Bornean tropical rainforest without dry seasons, gross primary production (GPP) and C allocation, i.e., above-ground net primary production (ANPP), aboveground plant respiration (APR), and total below-ground carbon flux (TBCF) for the forest were examined and compared with those from Amazonian tropical rainforests with dry seasons. GPP (30.61 MgC ha-1 year-1, eddy covariance measurements; 34.40 MgC ha-1 year-1, biometric measurements) was comparable to those for Amazonian rainforests. ANPP (6.76 MgC ha-1 year-1) was comparable to, and APR (8.01 MgC ha-1 year-1) was slightly lower than, their respective values for Amazonian rainforests, even though aboveground biomass was greater at our site. TBCF (19.63 MgC ha-1 year-1) was higher than those for Amazonian forests. The comparable ANPP and higher TBCF were unexpected, since higher water availability would suggest less fine root competition for water, giving higher ANPP and lower TBCF to GPP. Low nutrient availability may explain the comparable ANPP and higher TBCF. These data show that there are variations in C allocation patterns among mature tropical rainforests, and the variations cannot be explained solely by differences in soil water availability..
17. Hironori Toyama, Hiroki Itadani, Makiko Tateishi, Yuuya Tachiki, Keiko Mase, Yusuke Onoda, Nobuya Mizoue, Hidenori Tachida, Tetsukazu Yahara, Shuichiro Tagane, Phourin Chhang, Tsuyoshi Kajisa, Ryuji Ichihashi, Vanna Samreth, Ma Vuthy, Heng Sokh, Ayumi Katayama, Inventory of the Woody Flora in Permanent Plots of Kampong Thom and Kampong Chhnang Provinces, Cambodia, Acta Phytotaxonomica et Geobotanica, 10.18942/apg.KJ00008877422, 64, 2, 45-105, 2013, To improve our knowledge of the woody flora of Cambodia, we collected specimens of trees, shrubs and woody vines within and near permanent plots of evergreen and deciduous tropical forests in lowland Cambodia. We sequenced rbcL and matK for most specimens, searched for species having high homologies with those sequences and then identified the collections using taxonomic literature and herbarium specimens. As a result, we identified 325 species in 69 families, including 163 trees, 90 shrubs, 67 vines, four palms and an epiphytic parasite. The frequencies of correct identification of BLAST searched sequences were low at the species level (about 15%), but high at the family and generic levels (about 100% and 75%, respectively). Twenty-one species were new to Cambodia. We corrected many previous misidentifications in the plot records..
18. Michiko Nakagawa, Michinari Matsushita, Hiroko Kurokawa, Hiromitsu Samejima, Yayoi Takeuchi, Masahiro Aiba, Ayumi Katayama, Yuji Tokumoto, Tomonori Kume, Natsuko Yoshifuji, Koichiro Kuraji, Hidetoshi Nagamasu, Shoko Sakai, Tohru Nakashizuka, Possible Negative Effect of General Flowering on Tree Growth and Aboveground Biomass Increment in a Bornean Tropical Rain Forest, Biotropica, 10.1111/j.1744-7429.2012.00907.x, 44, 6, 715-719, 2012.11, We tested the effect of general flowering (GF), community-wide masting, and drought stress on current-year tree diameter growth and aboveground biomass increment (ABI). General flowering but not drought had a marginally significant negative effect on tree growth and ABI at the community level. Analyses of dominant species clarified this pattern..
19. Katayama A., Kume T., Komatsu H., Ohashi M., Nakagawa M., Yamashita M., Otsuki K., Suzuki M., Kumagai T., Effect of forest structure on the spatial variation in soil respiration in a Bornean tropical rainforest, Agricultural Forest meteorology, 2009.10.
20. Ayumi Katayama, Tomonori Kume, Hikaru Komatsu, Mizue Ohashi, Michiko Nakagawa, Megumi Yamashita, Kyoichi Otsuki, Masakazu Suzuki, Tomo'omi Kumagai, Effect of forest structure on the spatial variation in soil respiration in a Bornean tropical rainforest, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2009.05.007, 149, 10, 1666-1673, 2009.10, This study was undertaken to identify critical and practical factors explaining spatial variations in soil respiration and to estimate stand-scale soil respiration in an aseasonal tropical rainforest on Borneo Island. To this aim, we conducted soil respiration measurements at 25 points in a 40 m × 40 m subplot of a 4 ha study plot between 2002 and 2006, and examined the spatial variation in soil respiration averaged over the 4 years in relation to soil, root, and forest structural factors. In addition, we examined the spatial representativeness of soil respiration measured in the subplot using a specific scaling procedure. Consequently, we found significant positive correlation between the soil respiration and forest structural parameters such as the mean diameter at breast height (DBH), total basal area, and maximum DBH within 6 m of the measurement points. The most important factor was the mean DBH within 6 m of the measurement points, which had a significant linear relationship with soil respiration. Using the derived linear regression and an inventory dataset, we estimated the 4 ha plot-scale soil respiration. The 4 ha plot-scale estimation (6.0 μmol m-2 s-1) was nearly identical to the subplot-scale measurements (5.7 μmol m-2 s-1), which were roughly comparable to the nocturnal CO2 fluxes calculated using the eddy covariance technique. In addition, we discuss characteristics of the stand-scale soil respiration at this site by comparing with those of other forests reported in previous literature in terms of the soil C balance. Soil respiration at our site was noticeably greater, relative to the incident litterfall amount, than soil respiration in other tropical and temperate forests probably owing to the larger total belowground C allocation by emergent trees. Overall, this study suggests the arrangement of emergent trees with larger DBH and their belowground C allocation could be primary factors controlling spatial variations in soil respiration in the tropical rainforest..
21. Komatsu H., Katayama A., Hirose S., Kume A., Higashi N., Ogawa S., Otsuki K., Reduction in soil water availability and tree transpiration in a forest with pedestrian trampling, AGRICULTURAL AND FOREST METEOROLOGY, 10.1016/j.agrformet.2007.04.014, 146, 1-2, 107-114, 2007.09.
22. Hikaru Komatsu, Ayumi Katayama, Shigeki Hirose, Atsushi Kume, Naoko Higashi, Shigeru Ogawa, Kyoichi Otsuki, Reduction in soil water availability and tree transpiration in a forest with pedestrian trampling, Agricultural and Forest Meteorology, 10.1016/j.agrformet.2007.04.014, 146, 1-2, 107-114, 2007.09, Many studies have reported tree growth reduction in forests with pedestrian trampling, implying a reduction of tree transpiration in such forests. We undertook observations of tree transpiration based on the heat-pulse method in a forest (Lithocarpus edulis) with pedestrian trampling. We prepared trampled and control plots in the forest. Tree transpiration in the trampled plot was reduced compared to that in the control plot after precipitation with a small-precipitation period preceding this. No difference was observed between plots in the small-precipitation period itself; during which tree transpiration was limited in both plots. After the period, tree transpiration recovery was not as complete in the trampled plot as in the control plot. This was caused by incomplete soil matric potential recovery at 20 cm and deeper in the trampled plot due to a lower infiltration rate. We believe this study is the first to report reduction of tree transpiration in a forest with pedestrian trampling..
23. Komatsu H., Katayama A., Kume T., Otsuki K., Sap-flow velocity reduction by soil water deficit observed in a Lithocarpus edulis forest on Kyushu Island, Japan, Bulletin of Kyushu University Forest., 2007.03.