Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

We have reviewed publications on the physiological and ecological features of the growth and regeneration processes of Juniperus sabina L. which grows in semiarid sandy land in the Ordos plateau in northern China where desertification has progressed over time. J. sabina is a key native plant species used for ecological restoration in this region. The life history of J. sabina in this sandy land that has been revealed through this review includes several unique features: (1) both vegetative and seed propagations are observed, but seed propagation is not successful in the location where the mature J. sabina stands. Instead, seed propagation can occur at a different place with different landscapes from the mature stands. (2) Nurse plants play an important role in providing the microclimatic environment necessary for the growth of J. sabina seedlings and young plants. (3) During the horizontal and vertical growth processes of the J. sabina patch, the root system was affected by burial in shifting sand and consequently acquired greater access to the water supply in deeper soil horizons, which could support larger growth. These characteristics suggested that the regeneration by seed propagation and growth strategy of J. sabina in this region was strongly affected by sand movement and the landscape that is generated by sand movement.

DOI： 10.1007/s11355-021-00453-y

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

<title>Abstract</title>
<sec>
<title>Background and Aims</title>
Interspecific difference in pollinators (pollinator isolation) is important for reproductive isolation in flowering plants. Species-specific pollination by fungus gnats has been discovered in several plant taxa, suggesting that they can contribute to reproductive isolation. Nevertheless, their contribution has not been studied in detail, partly because they are too small for field observations during flower visitation. To quantify their flower visitation, we used the genus Arisaema (Araceae) because the pitcher-like spathe of Arisaema can trap all floral visitors.


</sec>
<sec>
<title>Methods</title>
We evaluated floral visitor assemblage in an altitudinal gradient including five Arisaema species. We also examined interspecific differences in altitudinal distribution (geographic isolation) and flowering phenology (phenological isolation). To exclude the effect of interspecific differences in altitudinal distribution on floral visitor assemblage, we established ten experimental plots including the five Arisaema species in high- and low-altitude areas and collected floral visitors. We also collected floral visitors in three additional sites. Finally, we estimated the strength and contribution of these three reproductive barriers using a unified formula for reproductive isolation.


</sec>
<sec>
<title>Key Results</title>
Each Arisaema species selectively attracted different fungus gnats in the altitudinal gradient, experimental plots and additional sites. Altitudinal distribution and flowering phenology differed among the five Arisaema species, whereas the strength of geographic and phenological isolations were distinctly weaker than those in pollinator isolation. Nevertheless, the absolute contribution of pollinator isolation to total reproductive isolation was weaker than geographic and phenological isolations, because pollinator isolation functions after the two early-acting barriers in plant life history.


</sec>
<sec>
<title>Conclusions</title>
Our results suggest that selective pollination by fungus gnats potentially contributes to reproductive isolation. Since geographic and phenological isolations can be disrupted by habitat disturbance and interannual climate change, the strong and stable pollinator isolation might compensate for the weakened early-acting barriers as an alternative reproductive isolation among the five Arisaema species.


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DOI： 10.1093/aob/mcaa204

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Other Link： http://academic.oup.com/aob/article-pdf/127/5/633/37118519/mcaa204.pdf

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

Mercury (Hg) is a pollutant that can affect human and ecosystem health. The transport and fate of Hg in the environment are dynamic and complex, but our understanding remains unclear for Japanese forest ecosystems. Here, we report the first country-wide survey of Hg concentrations in litter and surface mineral soil layers in 42 forest stands across Japan. The median concentrations of Hg in the litter layer and 0-10 cm of mineral soils were 99 (range: 56.7-297) and 145 (range: 22.8-294) mu g kg(-1), respectively, and tended to decrease down to 50 cm. There was a positive relationship between the Hg and total organic carbon concentrations in soil, suggesting that organic carbon strongly binds with Hg in soil. There was a significant positive correlation between the Hg and lead concentrations in the litter layer. Partial least square regression analysis indicated that the soil and litter properties as well as the atmospheric and geological Hg concentrations and some soil characteristics such as soil pH, organic matter properties and soil physical factors were effective explanatory variables of the country-wide spatial patterns of Hg concentrations in litter and mineral soil. In addition, we found the influence of atmospheric Hg is stronger in litter layer, whereas the influences of geological and soil factors are stronger in mineral soil. These results suggest that air pollution partly affects the spatial patterns of Hg concentrations in litter and soil of Japanese forests under the given geological and soil conditions at the country scale.

DOI： 10.1080/13416979.2020.1865510

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Premise The genus Arisaema (Araceae) has rapidly diversified in Japan, and multiple species often coexist in the field. Although Japanese Arisaema species hybridize from artificial crossing, hybrid individuals are rare in mixed populations; suggesting the presence of effective pre-pollination barriers. We examined the following reproductive barriers between A. sikokianum and A. tosaense: habitat, phenology, and pollinator isolations. Methods Habitat isolation was examined by interspecific comparisons of microhabitat conditions at a mixed site and of altitude at the sampling site of herbarium specimens. Phenological isolation was evaluated by comparing seasonal transition in apparent spathe condition and frequency of insect visitation. Pollinator isolation was examined by comparing floral visitor assemblages between the two Arisaema species. To avoid overestimation of pollinator isolation due to seasonal changes in insect assemblages, we also compared visitor assemblages between natural and late-flowering A. sikokianum, where the latter was experimentally introduced and blooming with a natural A. tosaense population. Results Microhabitat conditions and sampling elevations of herbarium specimens overlapped between the two Arisaema species. At the population level, A. sikokianum and A. tosaense flowered for 39 and 52 days, respectively, with 13 days overlap. Insect visitation in A. sikokianum decreased before the seasonal overlap. Floral visitor assemblages differed between the two Arisaema species, while the difference between natural and late-flowering A. sikokianum was less distinct. Conclusions Phenological and pollinator isolation contribute to reproductive isolation between the two Arisaema species and should enable the two species to coexist in this area.

DOI： 10.1002/ajb2.1389

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DOI： 10.1080/13416979.2019.1678708

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Language：Japanese   Publisher：日本緑化工学会  

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.foreco.2018.12.034

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Aboveground biomass is often restricted by water availability; therefore, water acquisition strategies have important roles in determining biomass volume and distribution under arid conditions. In cold Asian rangelands, the large tussock grass Achnatherum splendens is the most important forage for maintaining livestock under severe winter conditions. However, A. splendens distribution is restricted to the middle of the slopes of ephemeral streams, making it difficult to manage winter foraging. To understand the mechanisms behind the specific distribution and maintenance of a large A. splendens biomass under arid conditions, we established four typical vegetative plots along a riverside slope with different A. splendens density levels and elevations: river bottom with no A. splendens, riverbank with a large A. splendens community, upper slope with an isolated A. splendens community, and flat plain with no A. splendens. We measured the soil pH and electric conductivity (EC) of the plots and investigated the vertical biomass and root distribution of A. splendens. We also investigated the water source for the A. splendens communities using isotope techniques. The soil pH was not different among plots, while the soil EC was significantly higher in the river bottom because of salt accumulation. However, low soil EC levels were found under the A. splendens communities. In the ground below the A. splendens communities, plant stems were buried deeply. The belowground biomass and buried stem depths decreased at the sites of the isolated A. splendens communities in the upper slope. The aboveground biomass of A. splendens increased as the stem burial depths and, therefore, the adventitious roots depths increased. The water source of A. splendens was estimated to be at a depth of more than 30 cm. Thus, A. splendens prefers a habitat with a low level of soil salinity and a high level of water availability, which may increase with the sand burial depth because of the increasing accessibility of a substantial water source in the deeper soil layer. Sand burial may affect the water acquisition strategy and maintenance of large biomasses of tussock grass species that act as important winter forage in cold Asian rangelands.

DOI： 10.1002/ecs2.2511

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Rejuvenation by sprouting is a possible solution to prevent abandoned coppice forests in Japan from outbreaks of oak wilt disease. Applying this approach requires examining the sprouting capacity of large-sized oak trees. Therefore, the present study investigated the effects of stump size, sprout characteristics (emerging time and origin position), and environmental factors (slope, convexity, soil moisture, soil net nitrogen mineralization rate (Net-NMR) and canopy closure) on sprout regeneration of the two widely distributed oaks in Japan, Quercus serrata and Quercus acutissima, in the first growing season after cutting. In November 2013, a study plot (40x90m) was set, and canopy trees within the plot and edge areas were cut. We recorded sprout emergence, sprout origin position, sprout survival, and length from May to October 2014. Our data indicated that both species (ca. 60years old) have not yet lost their ability of sprouting. In Q. acutissima, the sprouting probability increased with light availability and was higher in concave area, and its number of living sprouts was positively related to stump diameter. In Q. serrata, the number of living sprouts increased with light availability. Sprouts emerged earlier and/or originated from the lower part of stump exhibited a higher survival probability. Emerging time substantially influenced sprout growth pattern and its effect followed a similar tendency in both species. Our results evidence that the ability of sprouting and the number of living sprouts might not be reduced in large-sized trees, and the increasing of light availability could promote sprout regeneration.

DOI： 10.1080/13416979.2018.1498288

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The seedling stage is critical in the life cycle of trees, and performance is controlled by both abiotic and biotic factors, which are spatially heterogeneous. We investigated the relationships between the seedling survival or growth of Fagus crenata and seven potentially influencing factors (culm density of dwarf bamboo, slope angle, topographic convexity, distance from the nearest conspecific adult, and local density of F. crenata seedlings, and seedling size and age), under consideration of the changes in direction and strength of the microtopographic effects across space. In 2011, we identified all F. crenata seedlings (maximum stem length &lt;50cm) within a 90x30-m plot in a cool-temperate forest in western Japan and then recorded their survival and growth of stem length in 2012. The best model based on Akaike's information criterion indicated that the size, age, and distance had positive effects on the survival while slope and convexity had negative effects, and that the strength of the negative effect of convexity varied spatially even within our plot. Meanwhile, the size and culm density had positive and negative effects on the growth, respectively. These results suggest that F. crenata seedlings have more chance to survive at the site on a gentle slope with planar or relatively concave undulations, where the conspecific adults stood apart, and that the seedlings show higher growth rate at the sites without dense dwarf bamboo. Furthermore, we demonstrate that the spatially nonstationary effect of microtopography controls the spatial pattern of seedling survival.

DOI： 10.1080/13416979.2017.1354749

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Seedling genotype is one of the major factors affecting seedling survival when the rate of damage by natural enemies depends on a host genotype. However, to our knowledge, no previous study has examined the mortality of seedlings adjacent to conspecific adults, considering intraspecific variation in seedling genotypes. On the basis of the assumption that natural enemies adapt to adult trees having a unique genotype, we tested the hypothesis that seedling survival decreases when they are more closely genetically related to neighboring adults, by measuring the mortality rate of seedlings of Fagus crenata growing in a cool-temperate forest in Japan. We estimated the genetic relatedness of seedlings (2 and 6 years old) to the neighboring adult F. crenata using microsatellite analysis and measured seedling survival. We determined that there was a non-significant negative correlation between seedling survival and genetic relatedness in the 2-year-old seedling cohort, and a non-significant but positive correlation in the 6-year-old seedlings. Our results call for further studies on the potential relationship between seedling survival and genetic relatedness to neighboring adults.

DOI： 10.1007/s11258-016-0591-z

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Dendrochronological approaches enable us to understand forest stand dynamics by estimation of disturbance history and age structure. The present study was conducted in an old-growth beech forest in a forest reserve in western Japan. Increment cores were taken for tree ring analysis from all canopy trees in a 50 m x 130 m study plot. Radial growth release criteria were developed to identify significant growth releases in each tree ring series and to characterize the disturbance history of the study site. The age structure of the forest was indicative of continuous establishment by Fagus crenata and simultaneous establishment by Magnolia obovata. A variety of low-intensity disturbances were identified in each decade, especially after the 1900s, but the occurrence of high-intensity catastrophic disturbance was rare, and likely played an important role in maintaining species diversity in the existing forest canopy. The results also suggest that F. crenata regenerates gradually before and after both large- and small-scale disturbances, whereas M. obovata and Betula grossa regenerate only after large-scale catastrophic disturbances.

DOI： 10.1007/s10310-015-0514-1

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DOI： 10.1007/s10310-016-0526-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

Dwarf bamboo is a major understory vegetation in Japanese forests, and is recognized to be an ecological filter for the seedlings of overstory tree species. However, the effects of dwarf bamboo cover on the entire understory tree community, including shrubs, have not been fully assessed. Using spatial analysis by distance indices (SADIE), we analyzed the spatial distributions of, and the spatial associations between, Sasa palmata cover and understory trees (diameter at breast height &lt; 2 cm, height a parts per thousand yen50 cm) in a cool-temperate deciduous broadleaf forest dominated by Fagus crenata. In a 20 m x 240 m area, we found 49 total species, among 11,686 stems. Cephalotaxus harringtonia var. nana, plus Lindera umbellata and F. crenata stems accounted for about 50 % of the overall total. The SADIE analysis based on 5 m x 5 m quadrats demonstrated that most species, among the 20 tree species we examined, showed significantly aggregated distributions (P &lt; 0.05) and/or significant spatial dissociations (P &lt; 0.05) with S. palmata cover. However, for C. harringtonia var. nana, L. umbellata, Meliosma tenuis, and Ligustrum tschonoskii, their spatial distributions were independent, or significantly associated (P &lt; 0.05) with S. palmata cover. Our results indicates that dwarf bamboo acts as an ecological filter, not only for the seedlings of overstory tree species but also for other understory trees, in the cool-temperate deciduous broadleaf forest.

DOI： 10.1007/s10310-015-0480-7

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Language：Japanese   Publisher：JAPANESE SOCIETY OF REVEGETATION TECHNOLOGY  

We investigated the effect of soil surface environmental conditions on the stand structure of Artemisia ordosica Krasch., which is a deciduous semi shrub and one of the revegetation plant in semiarid area, China. The effect of Juniperus sabina L., which has prostrate life-form and often distributed with A. ordosica was also considered. Individual density, position, size, existence of fruits, and soil surface conditions were measured. The results suggested that both species exclude with each other and the A. ordosica community on the fixed sand dune was influenced by the competition to get the resources with J. sabina rather than the nutrient conditions of soil surface.

DOI： 10.7211/jjsrt.41.56

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Language：Japanese   Publisher：JAPANESE SOCIETY OF REVEGETATION TECHNOLOGY  

We estimated establishment process of the secondary deciduous broad-leaved forest, based on the establishment and growth processes of dominant tree species detected by tree ring analysis. In the period of coppicing, many trees frequently showed releases, which suggest many remaining individuals abruptly grew by the disturbance of coppicing. Around the beginning of the abandonment, it is likely that Quercus serrata and Prunus jamasakura were most frequently established. Ratios of individuals showing suppressed growth increased in the succession after the abandonment. On the other hand, releases discontinuously occurred, which suggests disturbances by fallen trees occurred in the process of succession.

DOI： 10.7211/jjsrt.41.103

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Small-scale soil heterogeneity relates to productivity and biodiversity and is crucial to understand. Soil heterogeneity could be affected by vegetation structure, and large mammal grazers could modify it through herbivory and excretion. The objective is to clarify the effects of livestock grazing on the small-scale (similar to 3 m) soil heterogeneity in three types of Mongolian grasslands.
We sampled soils from inside (ungrazed) and outside (grazed) exclosures in three vegetation types: forest-steppe, shrub-steppe, and desert-steppe. We measured laboratory rates of soil net nitrogen (N) mineralization and net nitrification and geostatistically analyzed heterogeneity.
Average rates of net N mineralization and net nitrification were lower at shrub-steppe and desert-steppe and were decreased by grazing. Semivariograms showed vegetation-induced heterogeneity in ungrazed plots, except for net nitrification at forest-steppe. We found linear change with distance under dense and uniform vegetation at forest-steppe, 1.3 m patch under patchy vegetation at shrub-steppe, and linear change, but with much smaller semivariance, under sparse and poor vegetation at desert-steppe. At forest-steppe, grazing randomized the spatial patterns of net N mineralization and net nitrification. At shrub-steppe and desert-steppe, grazing greatly decreased the semivariances of net N mineralization and net nitrification as well as their averages, and the soil heterogeneity was virtually disappeared.
Grazing in Mongolian grasslands homogenized the spatial patterns of net N mineralization and net nitrification, irrespective of their original spatial patterns determined by the differences in vegetation structure.

DOI： 10.1007/s11368-013-0702-6

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Language：English   Publishing type：Research paper (scientific journal)  

To examine the effects of frequent fires on species composition of the boreal forest in northern Mongolia, we investigated regeneration patterns, including reproductive pathways, post-fire seed sources, and site preferences, of four common tree species (Betula platyphylla, Larix sibirica, Picea obovata, and Pinus sibirica). Regeneration patterns differed among B. platyphylla, L. sibirica, and the two evergreen conifers. B. platyphylla regenerated vigorously only after fire irrespective of the presence/absence of nearby seed sources, whereas post-fire regeneration of L. sibirica was more dependent on the presence of nearby seed sources. These two species did not regenerate in mature stands where mature trees of these species were growing. In contrast, no post-fire recruitment of P. obovata and P. sibirica was observed, whereas continuous recruitment of these species was observed in mature stands. The frequent fires that accompany illegal logging may result in larger burned areas and increase the risk of local extinctions of seed sources. The enlargement of burned areas is likely to favor post-fire recruitment of B. platyphylla. Seed dispersal limitation seems to have less effect on B. platyphylla than on the other species because of the wider seed dispersal range and vegetative reproduction capability of this species. Consequently, fires in the northern Mongolian boreal forest likely promote the relative dominance of B. platyphylla and threaten the existence of the evergreen conifers. © 2012 The Japanese Forest Society and Springer.

DOI： 10.1007/s10310-012-0345-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Plant physiological traits and their relation to soil N availability was investigated as regulators of the distribution of understory shrub species along a slope in a Japanese cedar (Cryptomeria japonica) plantation in central Japan.At the study site, previous studies demonstrated that both net and gross soil nitrification rates are high on the lower slope and there are dramatic declines in different sections of the slope gradient. We examined the distributions of understory plant species and their nitrate (NO (3) (-) -N) use traits, and compared the results with the soil traits.Our results show that boundaries between different dominant understory species correspond to boundaries between different soil types. Leucosceptrum stellipilum occurs on soil with high net and gross nitrification rates. Hydrangea hirta is dominant on soil with high net and low gross nitrification rates. Pieris japonica occurs on soil with very low net and gross nitrification rates. Dominant understory species have species-specific physiological traits in their use of NO (3) (-) -N. Pieris japonica lacks the capacity to use NO (3) (-) -N as a N source, but other species do use NO (3) (-) -N. Lindera triloba, whose distribution is unrelated to soil NO (3) (-) -N availability, changes the extent to which it uses NO (3) (-) -N in response to soil NO (3) (-) -N availability.Our results indicate that differences in the physiological capabilities and adaptabilities of plant species in using NO (3) (-) -N as a N source regulate their distribution ranges. The identity of the major form of available soil N is therefore an environmental factor that influences plant distributions.

DOI： 10.1007/s11104-012-1257-9

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DOI： 10.20660/applfor.22.1_7

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We investigated the effects of disturbances on the dynamics of white birch-dominated forests at the southern boundary of the Mongolian forest-steppe. Dendroecological techniques were used to assess regeneration patterns and recent mortality trends in three stands with no evidence of recent anthropogenic disturbance (undisturbed) and four stands with evidence of cutting or fire (disturbed). In the undisturbed stands, only one distinct stem establishment was observed in the period between 1910 and 1950, and no establishment has been observed since then. In the disturbed stands, however, high establishment mainly by sprouting was observed in the period between 1960 and 1980. Percentages of standing dead stems were higher in the undisturbed stands than in the disturbed stands. Mean ages at death in the undisturbed stands were ≥70 years old. The high mortality was likely induced by the death of smaller stems due to light competition, whereas the mortality of larger stems was likely the result of tree senescence. In summary, the undisturbed stands seem to be in danger of decline due to a lack of regeneration during the last half of the previous century and recent high mortality rates of older stems, while the disturbed stands may be maintained for the next several decades by the younger cohort established between 1960 and 1980. White birch-dominated forests at the southern boundary of Mongolian forest-steppe have probably relied on relatively short disturbance intervals in the past because of the disturbance-dependent regeneration trait and relatively short longevity of Betula species. © 2011 The Japanese Forest Society and Springer.

DOI： 10.1007/s10310-011-0324-z

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

Dwarf bamboos are major understory plants in subalpine and temperate forests of Japan. Several microphysical factors are known to influence their coarse-scale distribution, including slope angle, convexity, and proportion of gravel on the soil surface (hereafter gravel cover), but the effects of these factors on local variations in distribution are unclear. To elucidate these effects we examined relationships between local variations in Sasa palmata distribution and the 3 mentioned microphysical environmental factors within a 20- x 20-m plot divided into 0.5- x 0.5-m quadrats in a cool-temperate deciduous broadleaf forest, applying intrinsic conditional autoregressive models at 3 spatial resolutions (0.5 x 0.5 m, 1.0 x 1.0 m, and 2.0 x 2.0 m). The models show that the 3 microphysical factors, known to affect the distribution of S. palmata at coarser scales, also affect its distribution at fine scales. Slope angle and gravel cover had negative effects, while convexity had positive effects on its abundance. However, the strength of their effects depended on the spatial resolution: convexity had the strongest effects at 2-m scale, while slope angle and gravel cover had stronger effects at the finer scales. These findings provide indications of scale-dependent effects of environmental factors that may contribute both to fundamental understanding of forest dynamics and to efforts to enhance the regeneration and conservation of target species.

DOI： 10.2980/20-4-3640

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Arbuscular mycorrhizal fungi (AMF) have been observed in deep soil layers in arid lands. However, change in AMF community structure with soil depth and vertical distributions of the other root-associated microorganisms are unclear. Here, we examined colonization by AMF and dark septate fungi (DSF), as well as the community structure of AMF and endophytic fungi (EF) and endophytic bacteria (EB) in association with soil depth in a semiarid desert with shallow groundwater. Roots of Sabina vulgaris and soils were collected from surface to groundwater level at 20-cm intervals. Soil chemistry (water content, total N, and available P) and colonization of AMF and DSF were measured. Community structures of AMF, EF, and EB were examined by terminal restriction fragment length polymorphism analysis. AMF colonization decreased with soil depth, although it was mostly higher than 50%. Number of AMF phylotypes decreased with soil depth, but more than five phylotypes were observed at depths up to 100 cm. Number of AMF phylotypes had a significant and positive relationship with soil moisture level within 0-15% of soil water content. DSF colonization was high but limited to soil surface. Number of phylotypes of EF and EB were diverse even in deep soil layers, and the community composition was associated with the colonization and community composition of AMF. This study indicates that AMF species richness in roots decreases but is maintained in deep soil layers in semiarid regions, and change in AMF colonization and community structure associates with community structure of the other root-associated microorganisms.

DOI： 10.1007/s00572-011-0417-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

In arid and semiarid regions, variations in "islands of fertility" accompanied by discontinuous vegetation is frequently observed. However, the effects of vegetation patches on soil, including the influence of canopy size, are not fully understood, particularly under conditions of severe grazing. We examined the effects of patches of mound-forming shrub, Caragana microphylla, and the plant's canopy size on these islands of fertility in a heavily grazed Mongolian grassland. In 11 patches with various canopy sizes (32.5-180 cm in diameter), we compared the chemical properties of soils among three microsites: Mound, Below, and Around, which were inside, below, and outside of C. microphylla mounds, respectively. Total carbon (C) and most essential elements for the plants were more concentrated in Mound, but total nitrogen (N) and nonlimiting elements, such as exchangeable sodium (Na), did not significantly differ among microsites. Larger canopies more strongly affected the enrichment of total C and most essential elements, including total N, in Mound. These results suggest that C. microphylla patches substantially enrich total C and most essential elements and that the extent of enrichment was intensified with canopy size. However, under severe grazing, total N may be relatively more affected by the redistribution of resources through grazing, particularly when the canopy size is small.

DOI： 10.1007/s11355-010-0133-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Purpose Fire is a primary form of disturbance in boreal ecosystems. Charcoal is an important by-product of forest fire and has been reported to have the potential to influence the plant community establishing after fire. To date, however, no study has effectively tested the relationship between charcoal and plant regeneration in the actual post-fire forests. To determine the contribution of charcoal to soil properties and plant regeneration after forest fires, we conducted in situ investigations concerning the relationship between charcoal and the plant-soil system.
Materials and methods We conducted a field investigation in a recently burnt Gmelin larch (Larix gmelinii)/Scots pine (Pinus sylvestris) forest in the Russian Far East to investigate charcoal contents, pH, water contents, and nutrient availability in soil together with the regeneration of larch and pine seedlings.
Results and discussion Positive correlations were found between charcoal contents and soil pH, water contents, and available P contents. Additionally, charcoal contents and the number of pine seedlings were positively correlated. There was, however, no significant relationship between charcoal content and extractable NH(4) (+) content or the number of larch seedlings. These results suggest that while charcoal influences are somewhat obscure in the field, charcoal significantly contributes to the amelioration of water and nutrient availability together with the success of regeneration of pine seedling.
Conclusions Charcoal produced during fire events in Gmelin larch and Scots pine forests of eastern Russia has a modest influence on soil properties, but has the potential to improve regeneration in these fire-prone ecosystems.

DOI： 10.1007/s11368-011-0424-6

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Language：Japanese   Publisher：JAPANESE SOCIETY OF REVEGETATION TECHNOLOGY  

Grazing by large ungulates had both acceleration and deceleration effects on primary productivity and nutrient cycling in grassland ecosystems. The directions of these effects can differ among ecosystems because climate is one of the most important determinant. In Mongolian steppe, the ecosystem type is changed with latitudinal gradient of the aridity from forest-steppe in the north to steppe in the middle to gobi-steppe in the south. Our objective was to clarify the effects of livestock grazing on the surface soil chemical properties in three types of Mongolian steppe ecosystems along an aridity gradient. The soil samples (0.10 cm) were taken from inside and outside of the exclosure fence to analyze soil chemical properties and to determine net nitrogen (N) transformation rates for laboratory incubation. The elements essentially for the plants were decreased and net N transformations were decelerated along aridity with increasing soil pH. The effects of grazing were not prominent for the soil nutrient pools. However, the grazing decelerated net N transformation rates, especially drier incubation condition, and increased soil pH. These results suggested that grazing by large ungulates decelerated nutrient cycling, which might caused by increased alkalinity in Mongolian steppe ecosystems.

DOI： 10.7211/jjsrt.36.406

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Language：Japanese   Publisher：The Japanese Society of Revegetation Technology  

Pleioblastus pubescens Nakai occurs in different light conditions of secondary forests in the warmtemperate zone of Japan. Under different light conditions, we experimentally grew P. pubescence by planting the rhizomes, surveyed emergence, growth and survivorship of culms and leaves, and observed the morphology of leaves. Emerging duration of culms including tillering culms was longer, and the cumulative number of those culms was larger in the high light intensity than in the low light intensity. In the high light intensity, survival number of culms tended to be higher. The culm mortality in the relative light intensity of 1% was the highest In high light intensity, culm elongation rates were slower and the length after the complation elongation tended to be shorter than in the low light intensity. Therefore, it is suggested that P. pubescens has different regimes for invading and dominating the habitats in different light conditions. It is likely that P. pubescence increases the density with short culms in the high light intensity, on the other hand, it increases the length of culms with the low density in the low light intensit In foliage, longevity of leaves in high light intensity is shorter than that in the low light intensity. It was suggested that the foliage in the high light intensity is maintained by longer duration of culm and leaf emergence, and that in low light intensity is maintained by longer leaf longevity. In addition, leaves were smaller and thicker in light conditions.

DOI： 10.7211/jjsrt.34.524

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DOI： 10.7211/jjsrt.34.636

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DOI： 10.7211/jjsrt.35.51

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Language：English   Publisher：Graduate School of Environmental and Life Science, Okayama University  

&nbsp;&nbsp;We compared effects of different growing water potential conditions on physiological and morphological water&ndash;use properties of Sabina vulgaris Ant., which is an evergreen shrub that is widely distributed in arid and semi-arid environments of the Mu Us Sandy Land, China. Measurements were taken of cuttings grown for eight years under -0.02 MPa (control), -0.10 MPa (moderate water stress), and -0.34 MPa (severe water stress) water potential conditions. The transpiration rate (T_r) under moderate stress was significantly lower than that under severe stress and control water conditions (49% and 45% lower, respectively, than severe stress and the control on average). The leaf-specific hydraulic conductivity (LSC) in shrubs growing under moderate water stress was also significantly lower than for those under the severe water potential condition. In contrast, S. vulgaris growing under severe water stress had less leaf biomass than under moderate stress or control conditions. These results suggest that S. vulgaris growing under moderate water stress tends to show a reduced transpiration rate derived from its low LSC; therefore it avoids water loss in response to chronic water stress, while plants growing under severe water stress tends to reduce water loss through decreased leaf biomass. These results suggest that S. vulgaris has a high capacity for acclimation to different water potential conditions through physiological and morphological flexibility.

DOI： 10.3107/jesss.2.27

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

We present results of individual-based root system measurement and analysis applied for Larix gmelinii trees growing on the continuous permafrost region of central Siberia. The data of root excavation taken from the three stands were used for the analyses; young (26 years old), mature (105 years old), and uneven-aged over-mature stand (220 years old). In this article, we highlight two topics: (1) factors affecting spatio-temporal pattern of root system development, and (2) interactions between aboveground (i.e., crown) and belowground (i.e., root) competition. For the first topic, the detailed observation of lateral roots was applied to one sample tree of the overmature stand. The tree constructed a superficial (&lt; 30 cm in depth) and rather asymmetric root system, and each lateral root expanded mainly into elevated mounds rather than depressed troughs. This indicated that spatial development of an individual root system was largely affected by microtopography (i.e., earth hummocks). For these lateral roots, elongation growth curves were reconstructed using annual-ring data, and annual growth rates and patterns were compared among them. The comparison suggested that temporal root system development is associated with differences in carbon allocation among the lateral roots. For the second topic, we examined relationships between individual crown projection area (CA) and horizontal rooting area (RA) for the sample trees of each stand. RA was almost equal to CA in the young stand, while RA was much larger (three or four times) than CA in the mature and overmature stands. Two measures of stand-level space occupation, crown area index (aboveground: CAI; sum of CAs per unit land area) and rooting area index (belowground: RAI; sum of RAs), were estimated in each stand. The estimates of RA1 (1.3-1.8 m(2) m(-2)) exceeded unity in all stands. In contrast, CAI exceeded unity (1.3 m(2) m(-2)) only in the young stand, and was much smaller (&lt; 0.3 m(2) m(-2)) in the two older stands. These between-stand differences in RAI-CAI relationships suggest that intertree competition for both aboveground and belowground spaces occurred in the young stand, but only belowground competition still occurred in the two older stands. Based on this finding, we hypothesized that competition below the ground may become predominant as a stand ages in L. gmelinii forests. Methodological limitations of our analysis are also discussed, especially for the analysis using the two indices of space occupation (CAI, RAI).

DOI： 10.1007/s10310-006-0259-y

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Language：English   Publisher：JAPAN SOCIETY OF TROPICAL ECOLOGY  

We conducted a comparative study of nitrogen (N) dynamics in soil by examining a dry dipterocarp forest (DDF) and a dry evergreen forest (DEF), under similar climatic conditions, in northeastern Thailand. The soil N dynamics were described by measuring seasonal N mineralization and nitrification rates, soil microbial biomass, and the size of inorganic N pools and extractable organic N and C pools. We estimated the fluxes and production of inorganic N in soil using the ion exchange resin core and buried bag methods. Carbon and N accumulations were higher in the DEF than in DDF; DEF had likely been protected from fire for a longer time than DDF. We also found temporal and vertical differences in soil N dynamics between DDF and DEF. The greatest inorganic N flux in the soil occurred at the onset of the wet season in DDF, whereas inorganic N was produced throughout the wet season in DEF. N uptake occurred in the uppermost soil horizon in DDF, whereas N uptake in DEF occurred in the deeper soil horizon. The mean residence time of inorganic N was greater in DEF than in DDF. These results suggest that N cycles were faster in DDF than in DEF. During long-term incubation experiments, the dominant inorganic N form changed from NH₄⁺ to NO₃^-, coinciding with declining extractable organic C (EOC) concentrations at both sites. Shortages of EOC occurred earlier in DDF than in DEF. This finding indicates that EOC may be a useful index of C availability for soil N dynamics.

DOI： 10.3759/tropics.16.323

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Language：English   Publisher：The Japanese Society of Revegetation Technology  

Our interests are in detecting the spatial pattern of Phyllostachys nigra var. henonis culms within growth stages -sprouts, current-year culms, and 5-year-old culms- and discussing the changes among them. The analysis used Ripley's univariate L(t) function. Change in the spatial pattern among growth stages was not observed in the intermediate and edge parts of bamboo forest where culms were less aggregated from early stage. In the interior, sprouts and current-year culms had clumped distribution at almost all distances in years with high annual culm production, Spatial pattern changes were observed from a clumped distribution of current-year culms into a less aggregated distribution of 5-year-old culms. We infer that the density is a determinant in forming the spatial pattern of culm stage of P. nigra v. henonis through competition in the stand with high density culms.

DOI： 10.7211/jjsrt.33.65

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Water-extractable organic carbon (WEOC) drives the C and N cycles in forest ecosystems via microbial activity. However, few studies have considered both then spatial and temporal patterns of WEOC in forest soils. We investigated the spatial and temporal variation in WEOC along a topographic sequence in a cool temperate deciduous forest. The concentrations of WEOC, carbohydrates, total phenols, and other organics were 126 +/- 51, 40 +/- 15, 1.5 +/- 0.5 and 85 +/- 43 mg C kg dry soil(-1), respectively. Carbohydrates and phenols accounted for 33 +/- 11 and 1.5 +/- 1.0% of WEOC, respectively. The effect of season on the WEOC concentration was stronger than that of slope position the growing season, although most of the soil properties varied markedly with slope position. The concentration of carbohydrates in WEOC showed similar seasonal patterns across slope positions. The carbohydrate concentration peaked in May and August. The results suggest that carbohydrates are controlled by the recent production of C, rather than by organic C that has accumulated in soil. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.soilbio.2004.04.030

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

In a lowland tropical rain forest in Sarawak, leaf-litter decomposition and the initial litter chemistry of 15 tree species were studied. During 13 months of field experiment, weight loss of litter samples was between 44% and 91%, and calculated decomposition rate constants (k) ranged from 0.38 to 2.36 year(-1). The initial litter chemistry also varied widely (coefficients of variation: 19%-74%) and showed low N and P concentrations and high acid-insoluble residue (AIS) concentration. For nutrient-related litter chemistry, correlations with the decomposition rate were significant only for P concentration, C/P ratio, and AIS/P ratio (r(s) = 0.59, -0.62, and -0.68, n = 15, P &lt; 0.05, respectively). For organic constituents, correlations were significant for concentrations of AIS and total carbohydrates, and AIS/acid-soluble carbohydrate ratio (r(s) = -0.81, 0.51, and -0.76, n = 15, P &lt; 0.05, respectively). These results suggested that the relatively slow mean rate of decomposition (k = 1.10) was presumably due to the low litter quality (low P concentration and high AIS concentration), and that P might influence the decomposition rate; but organic constituents, especially the concentration of AIS, were more important components of initial litter chemistry than nutrient concentrations.

DOI： 10.1007/s10310-004-0087-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

The effects of tree species on the dynamics of nutrient transformations during leaf-litter decomposition are not well understood in tropical rain forests. To examine differences in the dynamics of C, nutrients, and organic constituents during decomposition among tree species, the leaf-litter decomposition of 15 trees was assessed using a litter-bag method in a lowland tropical rain forest in Sarawak. The dynamics of C was parallel to that of weight loss. The dynamics of nutrients were grouped into three patterns. The dynamics of K was characterized by a high leaching loss in the initial stages, and that of Ca and Mg generally showed a gradual decrease over the course of decomposition. The dynamics of N and P showed highly different patterns with the weight loss, and was characterized by relatively higher remaining mass at the end of the experiment. The variations or exceptions of nutrient dynamics among tree species were considered to be related to the initial concentration of each nutrient. For the dynamics of organic constituents, water-soluble carbohydrates disappeared quickly at the initial stages, and acid-soluble carbohydrates were the second fastest decomposing fraction; the decomposition of acid-insoluble residue (AIS) was the slowest. The release of limiting nutrients (N and P) generally followed the disappearance of AIS, but was independent of the disappearance of AIS when the initial concentrations of these nutrients were very low.

DOI： 10.1007/s10310-004-0088-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

Soil inorganic nitrogen supply and fine root mass in the top layers of mineral soil (0-5 and 5-10 cm) were investigated at upper and lower sites of a cool temperate forest where Fagus crenata and Quercus crispula dominate. At both sites, soil inorganic nitrogen supply was greatest in the 0-5 cm layer. The predominant forms of soil inorganic nitrogen supply were NH(4) (+)-N at the upper site and NO(3)(-)-N at the lower site. Fine roots were concentrated in the 0-5 cm layer at the upper site, but not at the lower site. The form of supplied soil inorganic nitrogen supply can be important in determining the vertical distribution of fine roots.

DOI： 10.1111/j.1440-1703.2004.00669.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG  

Measurement of nitrogen isotopic composition (delta(15)N) of plants and soil nitrogen might allow the characteristics of N transformation in an ecosystem to be detected. We tested the measurement of delta(15)N for its ability to provide a picture of N dynamics at the ecosystem level by doing a simple comparison of delta(15)N between soil N pools and plants, and by using an existing model. delta(15)N of plants and soil N was measured together with foliar nitrate reductase activity (NRA) and the foliar NO3- pool at two sites with different nitrification rates in a temperature forest in Japan. delta(15)N of plants was similar to that of soil NO3- in the high-nitrification site. Because of high foliar NRA and the large foliar NO3- pool at this site, we concluded that plant delta(15) N indicated a great reliance of plants on soil NO3- there. However, many delta(15)N of soil N overlapped each other at the other site, and delta(15)N could not provide definitive evidence of the N source. The existing model was verified by measured delta(15) N of soil inorganic N and it explained the variations of plant delta(15)N between the two sites in the context of relative importance of nitrification, but more information about isotopic fractionations during plant N uptake is required for quantitative discussions about the plant N source. The model applied here can provide a basis to compare delta(15) N signatures from different ecosystems and to understand N dynamics.

DOI： 10.1007/s10021-002-0132-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

Spatial patterns of soil nitrogen (N) transformations were examined using geostatistical analysis in three adjacent stands with different fire history (0, 10 and 35 years since the latest fire, respectively) in a dry tropical forest in Thailand. A larger pool of total inorganic N and a faster rate of N mineralization were recorded in the stand with longer fire prevention. At the spatial scale analyzed, the proportion of spatially dependent variance to the total variance of N mineralization and nitrification increased from 0.39 to 0.73, and from 0.40 to 0.77, respectively, with the time since the latest fire. The spatial autocorrelation ranges of N mineralization and nitrification decreased from greater than or equal to9.0 to 3.28m, and greater than or equal to9.0 to 2.77 m, respectively, with the time since the latest fire. These results suggested that fire history affected not only the level of available soil N, but also the spatial heterogeneity of soil N transformations, presumably due to the difference in plant influences on soil.

DOI： 10.1023/A:1022804326662

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING ASIA  

To examine the influence of microbial carbon (C) availability on the internal soil nitrogen (N) cycles under moder and mull forest floor types within the same slope sequence, surface mineral soils (0-5 cm depth) taken at upper (moder-type forest floor) and lower (mull-type forest floor) positions on a slope in a Cryptomeria japonica D. Don plantation were incubated for 300 days. During the incubation, changes in net and gross N transformations, the organic C and N pools, and microbial respiration were monitored. Despite relatively small differences in net N mineralization in both soils, very rapid rates of gross N transformations were found in mull soil during the initial 15 days of the experiment. A rapid net nitrification occurred after days 150 and 100 in moder and mull soils, respectively, presumably because of decreased microbial C availability. However, a rapid net nitrification also occurred in the mull soil during the initial 15 days when microbial C availability was high, and gross nitrification was detected in both soils, except at day 0 in the moder soil. Changes in gross N transformations and in organic C and N pools over the experiment suggested that the start of rapid net nitrification might be influenced not only by microbial C availability, but also by the microbial availability of N relative to C.

DOI： 10.1046/j.1440-1703.2003.00532.x

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DOI： 10.11353/sesj1988.16.227

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

Although Artemisia ordosica Krasch. and Sabina vulgaris Ant. are the dominant shrub species in the Mu-us desert ecosystem, they differ in their botanical traits. We investigated the spatial patterns of soil properties using geostatistical analysis to examine the effect of plant species on these spatial patterns. Comparison among three microsite types (under A. ordosica, under S. vulgaris, and the opening between vegetation) showed that A. ordosica generally had less effect than S. vulgaris on local soil properties. The long life-span, prostrate life-form, and evergreen leaf-habit of S. vulgaris may lead to a higher accumulation of organic and fine materials under S. vulgaris. The range of spatial autocorrelation found in the mass of organic matter on the soil surface was smaller than that of the coverage of S. vulgaris (11.5 m) which corresponded to the canopy patch size of this species, and was longer than the canopy patch size of A. ordosica. The ranges of total C and N, and pH (11.7-15.6 m) were similar to that of S. vulgaris. The range of available P (106.3 m) was comparable to that of the coverage of A. ordosica (86.2 m) considered to be the scale of the distribution of this species. The ranges of silt+clay and exchangeable K, Ca, and Mg (31.0-46.7 m) were not related to plant presence, and were similar to that of topography (43.1 m).

DOI： 10.1023/A:1017943030924

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DOI： 10.20660/applfor.10.2_19

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Language：English   Publisher：Japanese Forestry Society  

Soil N transformation was investigated using ^<15>N dilution method along a slope on a conifer plantation forest. Although there was no significant difference in the net N mineralization rates by laboratory incubation, net nitrification rates increased downslope. Gross N transformation by ^<15>N dilution method showed a distinct difference not only on the rates, but also on the main process between the lower and the upper of the slope. Half of minelarized N was immobilized and the other half was left in NH_4^+ pool at the upper part of the slope, while all of mineralized N was used for immobilization or nitrification and NH_4^+ pool decreased at the lower of the slope. Soil N transformations were classified into two groups : one was shown below 773 m and the other was shown above 782 m. The incubation with nitrification inhibitor showed that nitrification was mainly conducted by autotrophs irrespective of the position of the slope. Microbial biomass and microbial C/N were similar among the sites. However, the gross mineralization rate was higher below 773 m than above 782 m under similar respiration rates. This suggests that the substrate quality may be one of the controlling factors for soil N transformation. Extractable organic C/N was similar to microbial C/N at the lower of the slope. It indicated that the substrate was more decomposable below 773 m. It is considered that soil N transformation is affected by topographical gradient of moisture and nutrient which makes plant growth and decomposition rate different.

DOI： 10.1007/BF02762758

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Language：English  

DOI： 10.1016/S1164-5563(00)88649-5

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER  

The soil N transformation pattern depended on the topographic positions along a forest slope. Nitrate was the dominant inorganic N in the net mineralized N during incubation of the soil of the lower of the slope, and ammonium was the dominant in the soil of the upper of the slope. The middle of the slope was the boundary of the lower and upper soils. In the boundary, soil N transformation patterns seemed to depend on the local environmental conditions. Thus, the relationships between soil N transformation and soil properties were examined by correlation analysis. Net N mineralization rate highly correlated with total C, C/N ratio and pH, while net nitrification highly correlated with water content and 2M KCl extractable organic C and N.

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