start-ver=1.4 cd-journal=joma no-vol=17 cd-vols= no-issue=1 article-no= start-page=26007 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2026 dt-pub=20260601 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Understory Vegetation Structure in Remnant Natural Forests and Acacia Plantations on Coastal Sand Dunes in North Central Vietnam en-subtitle= kn-subtitle= en-abstract= kn-abstract=In the coastal sand dune forests of North Central Vietnam, vegetation has been seriously damaged by war and overexploitation. To recover ecosystem functions, including sand stabilisation under harsh environments, exotic species like Acacia spp. have been planted as a monoculture. However, the long-term sustainability of this practice remains unclear. To assess the long-term effectiveness of revegetation with Acacia spp., this study aims to understand the differences and similarities in ecological characteristics of remnant natural forests and Acacia plantations on the coastal sand dune of North Central Vietnam by comparing understory vegetation structure and environmental conditions. We investigated the understory vegetation (height < 130 cm) in a total of 54 quadrants (1 m × 1 m), including nine natural forests and nine Acacia plantations. We compared diversity indices by mixed ANOVA and examined the differences in the understory vegetation structure between the two forest types through PERMANOVA. We also determined some abiotic environmental factors (e.g. light and soil water availability, and soil pH). We identified 951 individuals, with 792 found in natural forests and 159 in plantations. The species found in natural forests were well-distributed among Liana phanerophytes (Lp), Microphanerophytes (Mi), Mega-Mesophanerophytes (MM), and Cryptophytes (Cr). In contrast, species found in plantations were predominantly Cr, Hemicryptophytes (Hm), and MM. All diversity indices were significantly higher in natural forests (P < 0.05), and the NMDS analysis confirmed significant differences in the understory vegetation structure between natural forests and plantations. Only soil pH was significantly lower in natural forests (P < 0.05), while none of the environmental factors had a statistically significant impact on the variations in understory vegetation structure. Our results indicate that succession by native tree species does not seem to occur naturally in Acacia plantations. Hence, to restore and sustainably develop coastal sand dune forests in North Central Vietnam, it is essential to establish a scientifically based strategy for managing and protecting the remaining natural remnant forest areas. en-copyright= kn-copyright= en-aut-name=DoanTuan Quoc en-aut-sei=Doan en-aut-mei=Tuan Quoc kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MatsumotoTetsuya K. en-aut-sei=Matsumoto en-aut-mei=Tetsuya K. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=DinhTai Tien en-aut-sei=Dinh en-aut-mei=Tai Tien kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=LeHung Thai en-aut-sei=Le en-aut-mei=Hung Thai kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=HoTuan Ngoc Anh en-aut-sei=Ho en-aut-mei=Tuan Ngoc Anh kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=MikiNaoko H. en-aut-sei=Miki en-aut-mei=Naoko H. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=HoHoang Thai Dac en-aut-sei=Ho en-aut-mei=Hoang Thai Dac kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=HirobeMuneto en-aut-sei=Hirobe en-aut-mei=Muneto kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= affil-num=1 en-affil=Okayama University, Graduate School of Environmental, Life, Natural Science and Technology kn-affil= affil-num=2 en-affil=Ibaraki University, Graduate School of Science and Engineering kn-affil= affil-num=3 en-affil=Hue Union of Science and Technology Associations (HUSTA) kn-affil= affil-num=4 en-affil=Hue University, University of Agriculture and Forestry kn-affil= affil-num=5 en-affil=Hue Union of Science and Technology Associations (HUSTA) kn-affil= affil-num=6 en-affil=Okayama University, Graduate School of Environmental, Life, Natural Science and Technology kn-affil= affil-num=7 en-affil=Hue Union of Science and Technology Associations (HUSTA) kn-affil= affil-num=8 en-affil=Okayama University, Graduate School of Environmental, Life, Natural Science and Technology kn-affil= en-keyword=natural forest kn-keyword=natural forest en-keyword=Acacia plantation kn-keyword=Acacia plantation en-keyword=coastal sand dunes forest kn-keyword=coastal sand dunes forest en-keyword=diversity kn-keyword=diversity en-keyword=understory vegetation kn-keyword=understory vegetation en-keyword=life forms kn-keyword=life forms en-keyword=environmental factor kn-keyword=environmental factor END start-ver=1.4 cd-journal=joma no-vol= cd-vols= no-issue= article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2026 dt-pub=20260521 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Effects of Juniperus sabina coverage on plant community structure in semiarid areas of China en-subtitle= kn-subtitle= en-abstract= kn-abstract=Plant interactions are one of the fundamental processes shaping the structure and function of plant communities and help create species diversity. Species diversity affects the current functioning of ecosystems and their resistance and resilience to future climate change. In harsh environments such as drylands, positive plant–plant interactions are important in promoting species diversity. Juniperus sabina is an evergreen shrub that is native to the semiarid areas of northern China. Because J. sabina can modify some harsh environmental conditions in its role as a nurse plant, it is expected to facilitate species diversity, although it may exhibit allelopathic inhibition. Previous research has only examined effects of J. sabina coverage onα-diversity in a single-year, and its effects on the β-diversity of the plant community structure in the local ecosystem are still unclear. We compared environmental conditions and plant species composition inside and outside of 11 J. sabina patches to evaluate the effects of its coverage on the species diversity of the understory community structure through modifying microhabitat conditions. Water and nutrient conditions were higher inside the patches, whereas light conditions were higher outside. More perennial herbs and C3 plants were found inside and more annual herbs and C4 plants were found outside. There were different trends in α-diversity each year, while β-diversity was consistently greater inside the patches. This research suggests that the coverage of J. sabina can drive different community structures by providing heterogeneous environmental conditions, and would increase plant species diversity in the local ecosystem. en-copyright= kn-copyright= en-aut-name=QinLong en-aut-sei=Qin en-aut-mei=Long kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YamabayashiAyaka en-aut-sei=Yamabayashi en-aut-mei=Ayaka kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=MatsumotoTetsuya K. en-aut-sei=Matsumoto en-aut-mei=Tetsuya K. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=ZhangGuosheng en-aut-sei=Zhang en-aut-mei=Guosheng kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=YamanakaNorikazu en-aut-sei=Yamanaka en-aut-mei=Norikazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=HirobeMuneto en-aut-sei=Hirobe en-aut-mei=Muneto kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=MikiNaoko H. en-aut-sei=Miki en-aut-mei=Naoko H. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= affil-num=1 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=2 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=3 en-affil=Faculty of Environmental and Life Science, Okayama University kn-affil= affil-num=4 en-affil=College of Ecology and Environment, Inner Mongolia Agricultural University kn-affil= affil-num=5 en-affil=Arid Land Research Center, Tottori University kn-affil= affil-num=6 en-affil=Faculty of Environmental and Life Science, Okayama University kn-affil= affil-num=7 en-affil=Faculty of Environmental and Life Science, Okayama University kn-affil= en-keyword=Nurse plant kn-keyword=Nurse plant en-keyword=Plant species diversity kn-keyword=Plant species diversity en-keyword=Plant species coexistence kn-keyword=Plant species coexistence en-keyword=Plant–plant interactions kn-keyword=Plant–plant interactions en-keyword=Mu Us sandy land kn-keyword=Mu Us sandy land END start-ver=1.4 cd-journal=joma no-vol=39 cd-vols= no-issue=8 article-no= start-page=1653 end-page=1660 dt-received= dt-revised= dt-accepted= dt-pub-year=2025 dt-pub=20250527 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Chemical composition of essential oil of Acacia crassicarpa Benth. (Fabaceae) from Vietnam en-subtitle= kn-subtitle= en-abstract= kn-abstract=This research aimed to identify the volatile compounds found in the fresh leaves of Acacia crassicarpa Benth. This is the first phytochemical investigation of this species. Essential oils from the leaves of A. crassicarpa were obtained by hydro-distillation and analyzed by gas chromatography coupled with mass spectrometry (GC/MS). Sixty-one compounds accounting for 95.8% of the leaf oil were identified. The classes of compounds identified in the oil sample were aldehydes (30.7%), sesquiterpene hydrocarbons (25.2%), alkanes (19.1%), oxygenated monoterpenes (3.6%) oxygenated sesquiterpenes (2.3%), monoterpene hydrocarbons (0.8%) and others (14.2%). The major constituents in the leaf oil were tridecanal (24.5%), (E)-caryophyllene (11.7%), n-heneicosane (7.2%), squalene (6.5%), and 7-tetradecenal (5.9%). en-copyright= kn-copyright= en-aut-name=Quoc DoanTuan en-aut-sei=Quoc Doan en-aut-mei=Tuan kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=Tien DinhTai en-aut-sei=Tien Dinh en-aut-mei=Tai kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=K. MatsumotoTetsuya en-aut-sei=K. Matsumoto en-aut-mei=Tetsuya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=DinhDien en-aut-sei=Dinh en-aut-mei=Dien kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=MikiNaoko en-aut-sei=Miki en-aut-mei=Naoko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=HirobeMuneto en-aut-sei=Hirobe en-aut-mei=Muneto kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=Thi NguyenHoai en-aut-sei=Thi Nguyen en-aut-mei=Hoai kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= affil-num=1 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Hue Union of Science and Technology Associations (HUSTA) kn-affil= affil-num=3 en-affil=Graduate School of Science and Engineering, Ibaraki University kn-affil= affil-num=4 en-affil=Phong Dien Nature Reserve, Phong Dien district, Thua Thien Hue province kn-affil= affil-num=5 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= affil-num=6 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= affil-num=7 en-affil=Faculty of Pharmacy, Hue University of Medicine and Pharmacy, Hue University kn-affil= en-keyword=Acacia crassicarpa kn-keyword=Acacia crassicarpa en-keyword=Essential oil kn-keyword=Essential oil en-keyword=Tridecanal kn-keyword=Tridecanal en-keyword=(E)-Caryophyllene kn-keyword=(E)-Caryophyllene END start-ver=1.4 cd-journal=joma no-vol=13 cd-vols= no-issue=5 article-no= start-page=719 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2024 dt-pub=20240304 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=The Impact of Phenological Gaps on Leaf Characteristics and Foliage Dynamics of an Understory Dwarf Bamboo, Sasa kurilensis en-subtitle= kn-subtitle= en-abstract= kn-abstract=Phenological gaps exert a significant influence on the growth of dwarf bamboos. However, how dwarf bamboos respond to and exploit these phenological gaps remain enigmatic. The light environment, soil nutrients, leaf morphology, maximum photosynthetic rate, foliage dynamics, and branching characteristics of Sasa kurilensis were examined under the canopies of Fagus crenata and Magnolia obovata. The goal was to elucidate the adaptive responses of S. kurilensis to phenological gaps in the forest understory. The findings suggest that phenological gaps under an M. obovata canopy augment the available biomass of S. kurilensis, enhancing leaf area, leaf thickness, and carbon content per unit area. However, these gaps do not appreciably influence the maximum photosynthetic rate, total leaf number, leaf lifespan, branch number, and average branch length. These findings underscore the significant impact of annually recurring phenological gaps on various aspects of S. kurilensis growth, such as its aboveground biomass, leaf morphology, and leaf biochemical characteristics. It appears that leaf morphology is a pivotal trait in the response of S. kurilensis to phenological gaps. Given the potential ubiquity of the influence of phenological gaps on dwarf bamboos across most deciduous broadleaf forests, this canopy phenomenon should not be overlooked. en-copyright= kn-copyright= en-aut-name=WuChongyang en-aut-sei=Wu en-aut-mei=Chongyang kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TanakaRyota en-aut-sei=Tanaka en-aut-mei=Ryota kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=FujiyoshiKyohei en-aut-sei=Fujiyoshi en-aut-mei=Kyohei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=AkajiYasuaki en-aut-sei=Akaji en-aut-mei=Yasuaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=HirobeMuneto en-aut-sei=Hirobe en-aut-mei=Muneto kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=MikiNaoko en-aut-sei=Miki en-aut-mei=Naoko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=LiJuan en-aut-sei=Li en-aut-mei=Juan kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=SakamotoKeiji en-aut-sei=Sakamoto en-aut-mei=Keiji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=GaoJian en-aut-sei=Gao en-aut-mei=Jian kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= affil-num=1 en-affil=Beijing for Bamboo & Rattan Science and Technology/International Centre for Bamboo and Rattan, Key Laboratory of National Forestry and Grassland Administration kn-affil= affil-num=2 en-affil=Faculty of Agriculture, Okayama University kn-affil= affil-num=3 en-affil=Faculty of Agriculture, Okayama University kn-affil= affil-num=4 en-affil=Biodiversity Division, National Institute for Environmental Studies kn-affil= affil-num=5 en-affil=Department of Environmental Ecology, Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=6 en-affil=Department of Environmental Ecology, Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=7 en-affil=Beijing for Bamboo & Rattan Science and Technology/International Centre for Bamboo and Rattan, Key Laboratory of National Forestry and Grassland Administration kn-affil= affil-num=8 en-affil=Department of Environmental Ecology, Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=9 en-affil=Beijing for Bamboo & Rattan Science and Technology/International Centre for Bamboo and Rattan, Key Laboratory of National Forestry and Grassland Administration kn-affil= en-keyword=bamboo kn-keyword=bamboo en-keyword=sasa kn-keyword=sasa en-keyword=beech forest kn-keyword=beech forest en-keyword=phenological gap kn-keyword=phenological gap en-keyword=canopy kn-keyword=canopy en-keyword=understory plant kn-keyword=understory plant en-keyword=plant morphology kn-keyword=plant morphology en-keyword=plastically kn-keyword=plastically en-keyword=leaf phenology kn-keyword=leaf phenology END start-ver=1.4 cd-journal=joma no-vol=17 cd-vols= no-issue= article-no= start-page=267 end-page=279 dt-received= dt-revised= dt-accepted= dt-pub-year=2021 dt-pub=20210417 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Effects of large-scale forest fire followed by illegal logging on the regeneration of boreal forests in Mongolia en-subtitle= kn-subtitle= en-abstract= kn-abstract=We aimed to test the hypothesis that large-scale forest fire followed by illegal logging inhibits the regeneration of boreal forests in Mongolia. For this purpose, we compared regeneration of the forest between five stands in a large-scale post-fire site, i.e., (1) undisturbed stand in the unburnt and remaining forest, (2) stand disturbed by illegal logging in the unburnt and remaining forest, (3) stand disturbed by forest fire, (4) stand disturbed by forest fire followed by illegal logging and located in proximity to the remaining forest, which acts as a seed source, and (5) stand disturbed by forest fire followed by illegal logging and located far from the remaining forest, which acts as a seed source. The stand disturbed by logging showed similar species composition of regenerated individuals as the undisturbed stand. In the stand disturbed by logging, Picea obovata and Pinus sibirica were abundant because of advance regeneration on the intact forest floor. In the stand disturbed by forest fire and that disturbed by forest fire followed by illegal logging, Larix sibirica and Betula platyphylla were abundant, and the regenerated individuals of these two species were new individuals after the disturbances. L. sibirica was abundant in the stand disturbed by forest fire because the mother trees survived the forest fire because of their thick bark. B. platyphylla was abundant in the stand disturbed by forest fire followed by illegal logging because the mother trees of L. sibirica were logged and the seeds of B. platyphylla are able to disperse further than that of L. sibirica. However, in the stand disturbed by forest fire followed by illegal logging that was located far from the remaining forest, the regeneration was much reduced because only few seeds, including that of B. platyphylla, were dispersed into this stand and sprouts of B. platyphylla were damaged by the logging operation. In addition, the regeneration of L. sibirica and B. platyphylla was likely to have been reduced for several years after the forest fire because of the loss of safe sites for their invasion by the changes of the forest floor conditions. Therefore, it is likely that large-scale forest fires that are followed by illegal logging inhibit the regeneration in many parts of the post-fire site and those parts will change into open forests of B. platyphylla or grassland. en-copyright= kn-copyright= en-aut-name=SakamotoKeiji en-aut-sei=Sakamoto en-aut-mei=Keiji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TomonariMisaki en-aut-sei=Tomonari en-aut-mei=Misaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=AriyaUyanga en-aut-sei=Ariya en-aut-mei=Uyanga kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=NakagiriErika en-aut-sei=Nakagiri en-aut-mei=Erika kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=MatsumotoTetsuya en-aut-sei=Matsumoto en-aut-mei=Tetsuya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=AkajiYasuaki en-aut-sei=Akaji en-aut-mei=Yasuaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=OtodaTakashi en-aut-sei=Otoda en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=HirobeMuneto en-aut-sei=Hirobe en-aut-mei=Muneto kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=NachinBaatarbileg en-aut-sei=Nachin en-aut-mei=Baatarbileg kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= affil-num=1 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=2 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=3 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=4 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=5 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=6 en-affil=Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies kn-affil= affil-num=7 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=8 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=9 en-affil=School of Engineering and Applied Sciences, National University of Mongolia kn-affil= en-keyword=Disturbance kn-keyword=Disturbance en-keyword=Forest floor kn-keyword=Forest floor en-keyword=Salvage logging kn-keyword=Salvage logging en-keyword=Seed source kn-keyword=Seed source en-keyword=Succession kn-keyword=Succession END start-ver=1.4 cd-journal=joma no-vol=95 cd-vols= no-issue=1 article-no= start-page=93 end-page=95 dt-received= dt-revised= dt-accepted= dt-pub-year=2006 dt-pub=200602 dt-online= en-article= kn-article= en-subject= kn-subject= en-title=Spatial Variabillity of Soil Nitrogen Dynamics slong a Slope in a Cryptomeria japonica D.Don Plantation kn-title=スギ人工林の斜面に沿った土壌窒素動態の空間的変動 en-subtitle= kn-subtitle= en-abstract= kn-abstract=Spatial variabillity of soil nitrogen(N) dynamics was examined along a slope in a 45-year-old Cryptomeria japonica D.Don plantation in the southeastern paet of Shiga Prefecture. Net N mineralization showed no clear gradient along the slope, while net nitrification and percent nitrification were high at lower positions,and very low at upper positions of the slope. Principal component(PC) analysis showed soil properties were divided into three groups which were PC1(water content and pH), and PC3(total C and N). Regressions of net soil N transformations against PCs scores suggested net N mincralization was mainly regulated by PC3, while net nitrification and percent nitrification were mainly regulated by PC1 and PC2. The difference in the main form of inorganic N was expected to affect soil N availability for plants through the difference in the mobility in negatively changed forest soil. We evaluated the soil N availability that reflebted the ion mobility factors by ion exchange resins and found that greater mobility of nitrate lead to greater soil N availability at lower positions of the slope. In addition, gross N transformations were directly measured using 15N isotope dilution, and the influence of microbial caebon (C) availability on the internal soil N cycles were examined by long-term laboratory incubation. Gross nitrifivation was detected in both soils taken at upper and lower positions on the slope, suggesting that nitrification was also an important process at upper positions where almost no net nitrification was detected. Changes in net and gross N transformations, the organic C and N pools, and microbial respiration suggested that start of rapid net nitrifibation might be affected not only by the availability of C for microbial biomass, but also by the relative availability of C and N. en-copyright= kn-copyright= en-aut-name=HirobeMuneto en-aut-sei=Hirobe en-aut-mei=Muneto kn-aut-name=廣部宗 kn-aut-sei=廣部 kn-aut-mei=宗 aut-affil-num=1 ORCID= affil-num=1 en-affil= kn-affil=岡山大学 en-keyword=forest slope kn-keyword=forest slope en-keyword=net and gross soil nitrogen transformations kn-keyword=net and gross soil nitrogen transformations en-keyword=nitrification kn-keyword=nitrification en-keyword=nitrogen mineralization kn-keyword=nitrogen mineralization en-keyword=spatial variability kn-keyword=spatial variability END