Dwarf Bamboo Research Articles

Unveiling the Hidden Responses: Metagenomic Insights into Dwarf Bamboo (Fargesia denudata) Rhizosphere under Drought and Nitrogen Challenges.

Dwarf bamboo (Fargesia denudata) is a crucial food source for the giant pandas. With its shallow root system and rapid growth, dwarf bamboo is highly sensitive to drought stress and nitrogen deposition, both major concerns of global climate change affecting plant growth and rhizosphere environments. However, few reports address the response mechanisms of the dwarf bamboo rhizosphere environment to these two factors. Therefore, this study investigated the effects of drought stress and nitrogen deposition on the physicochemical properties and microbial community composition of the arrow bamboo rhizosphere soil, using metagenomic sequencing to analyze functional genes involved in carbon and nitrogen cycles. Both drought stress and nitrogen deposition significantly altered the soil nutrient content, but their combination had no significant impact on these indicators. Nitrogen deposition increased the relative abundance of the microbial functional gene nrfA, while decreasing the abundances of nirK, nosZ, norB, and nifH. Drought stress inhibited the functional genes of key microbial enzymes involved in starch and sucrose metabolism, but promoted those involved in galactose metabolism, inositol phosphate metabolism, and hemicellulose degradation. NO3--N showed the highest correlation with N-cycling functional genes (p < 0.01). Total C and total N had the greatest impact on the relative abundance of key enzyme functional genes involved in carbon degradation. This research provides theoretical and technical references for the sustainable management and conservation of dwarf bamboo forests in giant panda habitats under global climate change.

Scarification under the canopy of Japanese oak: should pre-harvest treatment coincide with the masting year of acorns?

ABSTRACT The regeneration of Japanese oak (Quercus crispula Blume) has turned even more pressing in recent years. The pre-harvest treatment, which accumulates advanced seedlings, is essential for its natural regeneration in stands with a dense dwarf bamboo cover. Such pre-harvest treatment is considered particularly effective when done in conjunction with a mast year of acorns, but it is difficult to adjust the operation to specific timing. If there is no mast year for several years after the pre-harvest treatment, there is concern that the “priority effect” from other plant species may inhibit Japanese oak regeneration. The objective of this study was to determine whether scarification under the canopy of Japanese oaks, treated several years before the masting of acorns, is effective for its regeneration. Seedlings and vegetation were surveyed at sites scarified four years before (PRE) and just before masting (MAST) to compare the effects of treatments, i.e. differences in scarification years on the number and/or size of tall trees and other plant species. PRE could limit the predominance of dwarf bamboos and birches, and sufficient number of seedlings (>10 stems m−2) for future development was observed in the fifth year after masting. Since Japanese oak generally has a masting cycle of less than 5 years at most, we can conclude that the timing of pre-harvest treatment is not constrained by the masting year. Further studies are required to determine the details of priority effects of competitive plants on oak seedlings to establish a natural forest management for Japanese oak.

Wood Mice Utilize Understory Vegetation of Leafless Dead Dwarf Bamboo Culms as a Habitat and Foraging Site

Wood Mice Utilize Understory Vegetation of Leafless Dead Dwarf Bamboo Culms as a Habitat and Foraging Site

Effects of Human Harvesting, Residences, and Forage Abundance on Deer Spatial Distribution.

It has been known that harvesting by humans strongly influences individual within-home range habitat selection of many deer species; however, little is known about the effect of harvesting on coarse-scale habitat selection (i.e., spatial distribution). We examined the summer spatial distribution of sika deer Cervus nippon in relation to human harvesting and other factors, such as human residences, forage abundance, and cover, using pellet group counts at Mount Fuji, central Japan, in 2018. In the study area, harvesting is conducted at medium elevation areas throughout the year, but not at high or low elevation areas where access is difficult or harvesting is prohibited. Spatial distribution of deer was significantly biased to non-harvesting areas and far from residential areas, suggesting that they avoid riskier spaces by establishing a landscape of fear. High-quality food resources (deciduous broad-leaved trees and forbs) were more abundant in harvesting areas than in non-harvesting areas, suggesting that foraging pressure by deer reduce them. However, there were no differences in abundances of more fibrous dwarf bamboo between harvesting and non-harvesting areas, and spatial distribution of deer was significantly biased to higher dwarf bamboo abundance areas, suggesting that the dwarf bamboo is an alternative food resource in non-harvesting areas where supplies of high-quality food were limited. Our results suggest that human harvesting pressure and residences shifted the spatial distribution of deer from the montane forests to subalpine/alpine zones, which may increase damage to vulnerable ecosystems due to severe foraging pressure.

Eight-Year Survival and Growth of Sakhalin Fir (Abies sachalinensis) Seedlings with One Weeding Operation: Impact of Mechanical Site Preparation, Vegetation Release, Summer Planting, Stock Type, and Forwarder Trail

In Hokkaido, northern Japan, bareroot Sakhalin fir seedlings are conventionally planted in spring and fall, following strip site preparation that alternates managed and unmanaged strips. However, this method requires seven years of weeding due to encroachment of evergreen dwarf bamboo. Given diminishing forest labor availability, a shortage of workers for planting and weeding operations has become a problem in reforestation following clearcutting. We examined whether comprehensive mechanical site preparation (MSP) could reduce weeding frequency by preventing regrowth of dwarf bamboo and whether container seedlings could extend the planting season into summer. Over eight years, the survival and growth of summer-planted bareroot and container seedlings were examined on a fully MSP-treated site with only one weeding operation in the fifth year. Full-site MSP resulted in a shift of the vegetation from dwarf bamboo to deciduous plants, leading to high survival and growth rates of Sakhalin fir seedlings despite minimal weeding. Container seedlings exhibited superior establishment and maintained higher survival rates over eight years than bareroot seedlings. However, planting on the forwarder trail decreased seedling growth, and ultimately decreased survival under rare summer drought. Our findings indicate that container seedling summer planting and full-site MSP may represent an alternative approach to reforestation of Sakhalin fir, potentially reducing the need for weeding and extending the planting season.

Reponses of morphological and biochemical traits of bamboo trees under elevated atmospheric O3 enrichment

Dwarf bamboo (Indocalamus decorus) is an O3-tolerant plant species. To identify the possible mechanism and response of leaf morphological, antioxidant, and anatomical characteristics to elevated atmospheric O3 (EO3) concentrations, we exposed three-year-old I. decorus seedlings to three O3 levels (low O3-LO: ambient air; medium O3-MO: Ambient air+70 ppb high O3–HO: Ambient air+140 ppb O3) over a growing season using open-top chambers. Leaf shape and stomatal characteristics, and leaf microscopic structure of I. decorus were examined. The results indicated that 1) the stomata O3 flux (Fst) of HO decreased more rapidly under EO3 as the exposure time increased. The foliar O3 injury of HO and MO occurred when AOT40 was 26.62 ppm h and 33.20 ppm h, respectively, 2) under EO3, leaf number, leaf mass per area, leaf area, and stomata length/width all decreased, while leaf thickness, stomatal density, width, and area increased compared to the control, 3) MDA and total soluble protein contents all showed significantly increase under HO (36.57% and 32.77%) and MO(31.91% and 19.52%) while proline contents only increased under HO(33.27%). 4) MO and HO increased bulliform cells numbers in the leaves by 6.28% and 23.01%, respectively. HO reduced the transverse area of bulliform cells by 13.73%, while MO treatments had no effect, and 5) the number of fusoid cells interspace, the transverse area of fusoid cells interspace, and mesophyll thickness of HO significantly increased by 11.16%, 28.58%, and 13.42%, respectively. In conclusion, I. decorus exhibits strong O3 tolerance characteristics, which stem from adaptions in the leaf's morphological, structural, antioxidant, and anatomical features. One critical attribute was the enlargement of the bulliform cell transverse area and the transverse area of fusoid cells interspace that drove this resistance to O3. Local bamboo species with high resistance to O3 pollution thus need to be promoted for sustained productivity and ecosystem services in areas with high O3 pollution.

Microorganisms facilitated the saline‐alkali soil remediation by biochar: Soil properties, microbial communities, and plant responses

AbstractSaline‐alkali soil degradation is a significant environmental problem with a negative impact on sustainable agroforestry development. Therefore, efficient remediation methods are urgently required. A potential solution to this problem is using biochar produced from bamboo waste and inoculated with plant growth‐promoting microbes as cleaner production materials for saline‐alkali soil. The present study investigated the potential of combining biochar, microbes, and dwarf bamboo to improve saline‐alkali soil. Different application rates (1%, 3%, and 5% of soil mass) of biochar were added to coastal saline soil planted with dwarf bamboo (Pleioblastus argenteastriatus) in pot experiments. Soil physicochemical properties, microbial communities, and plant responses were systematically studied. Bamboo and microbial‐modified biochar effectively decreased soil pH and electrical conductivity and increased soil nutrient contents. Compared with untreated soil, the relative abundance of the dominant bacterial phyla Acidobacteria, Actinobacteria, and Chloroflexi, and dominant fungal phyla Basidiomycota increased after applying biochar and modified biochar. With the increase in application concentration, the antioxidant activities of modified biochar decreased, biochar peroxidase and catalase content decreased, and the malondialdehyde content of bamboo biochar and microbial‐modified bamboo biochar decreased. The biomass of bamboo with added biochar and modified biochar was significantly higher than that of untreated soil. Comprehensive correlation and redundancy analyses showed that the bacterial and fungal communities were greatly affected by soil factors, especially soil pH, electrical conductivity, total organic carbon, potassium, and sodium ions. The findings of this study suggest that 5% bamboo biochar and 3% modified biochar benefit soil remediation, improve the stress resistance of dwarf bamboo, and enhance plant growth. Therefore, combined biochar–microbe remediation has great potential for the sustainable improvement of saline‐alkali soil.

The Impact of Phenological Gaps on Leaf Characteristics and Foliage Dynamics of an Understory Dwarf Bamboo, Sasa kurilensis.

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.

Comparison of four performance models in quantifying the inequality of leaf and fruit size distribution.

The inequality in leaf and fruit size distribution per plant can be quantified using the Gini index, which is linked to the Lorenz curve depicting the cumulative proportion of leaf (or fruit) size against the cumulative proportion of the number of leaves (or fruits). Prior researches have predominantly employed empirical models-specifically the original performance equation (PE-1) and its generalized counterpart (GPE-1)-to fit rotated and right-shifted Lorenz curves. Notably, another potential performance equation (PE-2), capable of generating similar curves to PE-1, has been overlooked and not systematically compared with PE-1 and GPE-1. Furthermore, PE-2 has been extended into a generalized version (GPE-2). In the present study, we conducted a comparative analysis of these four performance equations, evaluating their applicability in describing Lorenz curves related to plant organ (leaf and fruit) size. Leaf area was measured on 240 culms of dwarf bamboo (Shibataea chinensis Nakai), and fruit volume was measured on 31 field muskmelon plants (Cucumis melo L. var. agrestis Naud.). Across both datasets, the root-mean-square errors of all four performance models were consistently smaller than 0.05. Paired t-tests indicated that GPE-1 exhibited the lowest root-mean-square error and Akaike information criterion value among the four performance equations. However, PE-2 gave the best close-to-linear behavior based on relative curvature measures. This study presents a valuable tool for assessing the inequality of plant organ size distribution.

Broad-leaved and mixed cooltemperate forests from the class Fagetea crenatae Miyawaki, Ohba et Murase 1964 on Kunashir Island (the Kurils archipelago)

This study presents the classification and description of three new associations of cool-temperate zonal forests of the vegetation class Fagetea crenatae Miyawaki, Ohba et Murase 1964 on Kunashir and Hokkaido islands. The Filipendulo camtschaticae–Aceretum mayrii ass. nov. encompasses broad-leaved forests in eutrophic moist ecotopes dominated by Acer mono subsp. mayrii. The Abieti sachalinensis–Quercetum crispulae ass. nov. represents zonal mixed forests dominated by Quercus mongolica var. crispula with an admixture of coniferous tree species Abies sachalinensis, Taxus cuspidata, and Picea jezoensis (the latter only on Kunashir Island, in forests of the subass. piceetosum jezoensis). The Hydrangeo paniculatae–Quercetum crispulae ass. nov. includes secondary species-poor forests dominated by Q. mongolica var. crispula, Betula ermanii, or B. pendula subsp. mandshurica. All associations feature a dense understory of dwarf bamboo species Sasa spp., with the densest tickets found in Hydrangeo paniculatae–Quercetum crispulae forests. We also validated the union Carpino cordatae–Quercion crispulae Takeda, Uemura et Nakanishi ex Korznikov, Dzizyurova et Petrenko all. nov. which represents the zonal cool-temperate broad-leaved and mixed forests in Hokkaido, Sakhalin, Iturup and Kunashir. Broad-leaved forests of Kunashir exhibit lower species diversity compared to Hokkaido, missing typical temperate tree species such as Acer palmatum, Carpinus cordata, and Tilia japonica.

Reconstruction of Regeneration Process Using Selective Cutting Practice in a &lt;i&gt;Chamaecyparis obtusa&lt;/i&gt; Forest with an Undergrowth Lacking Dwarf Bamboo by Tree-ring Analysis

Reconstruction of Regeneration Process Using Selective Cutting Practice in a &lt;i&gt;Chamaecyparis obtusa&lt;/i&gt; Forest with an Undergrowth Lacking Dwarf Bamboo by Tree-ring Analysis

Risk-spreading strategies of two dwarf bamboos in heterogeneous Pb (lead) environments

As a typical clonal plant, dwarf bamboo has potential applications in the remediation of Pb (lead) -contaminated soils; however, the environmental risk-spreading strategies of dwarf bamboo in heterogeneous Pb-contaminated environments are not known. To this end, we conducted hydroponic experiments on two species of groundcover bamboo, Sasa fortunei (Van Houtte) Fiori (SF) and Sasa auricoma (Mitford) E.G. Camus (SU), with seven treatments including two environments, homogeneous and heterogeneous. The results showed that SF protected the distal ramets (DRs) and that SU did the opposite in a homogeneous Pb environment. In the heterogeneous Pb environment, the NTR of both bamboos (RSISF = 0.64/0.44, RSISU = 0.40/0.33) was higher than that under the heterogeneous high-concentration environment (RSISF = 0.15/0.28, RSISU = 0.26/0.26). Moreover, the total Pb concentration of SF was as high as 80123.5 mg/kg and that of SU was as high as 53333.33 mg/kg, and in general, SF was more capable of absorbing Pb. In the heterogeneous low-Pb environment, the ascorbic acid and proline levels of the TRs (Pb-treated ramets) were elevated to alleviate oxidative stress; in contrast, antioxidant enzyme activities of SU were all reduced due to the damage caused by Pb absorption. The results of the experiments showed that SF had a greater risk-spreading capacity and higher Pb concentrations than SU in heterogeneous environments, and therefore, SF had better Pb bioenrichment and tolerance than SU. We proposed a novel metric (RSI) to assess the ability of plants to spread risk, and the results of the study provid a basis for dwarf bamboo phytoremediation in heterogeneous Pb environments.

Competitive ability of dwarf bamboo (Sasa borealis) through long‐term clonal growth in mixed dwarf bamboo communities in the understory of a temperate deciduous forest

AbstractWe investigated the clonal competition of three co‐occurring dwarf bamboo species, Sasa borealis, Sasa nipponica, and Sasaella ramosa, for 32 years in an old‐growth beech forest in central Japan. A study plot (10 m × 24 m) was established to examine the culm dynamics of these species. Sasa borealis had a competitive advantage over the other species. It invaded the other bamboo populations at a rate of 0.84–0.89 m/y from 1988 to 2020, while S. nipponica invaded at a rate of 0.17 m/y until 2003. After that, S. nipponica started to retreat at a rate of 0.85 m/y along with the invasion of S. borealis until 2020. The invasion rate of S. borealis did not change before and after the competition with S. nipponica. Our results showed that it would take 13.9–14.8 years from S. borealis invasion for S. nipponica to disappear. The density of S. ramosa decreased but it did not disappear from the plot because it retreated at a slow rate of 0.08 m/y. Sasa borealis almost achieved its potential maximum culm density, but the other two bamboo species did not. If stable conditions were maintained, S. borealis would continue to invade, dominate, and eliminate the other bamboo species. The ecological traits of dwarf bamboo species, such as the maximum density, size, and longevity of culms, are good indicators for assessing their competitiveness. Our findings demonstrate that dwarf bamboo species are actually replaced by another bamboo species in the forest understory during a long period.

How much do field mice prefer dwarf bamboo seeds? Two-choice experiments between seeds of Sasa borealis and several tree species on the forest floor.

Bambusoideae is a taxon of mass-flowering monocarpic perennials with a long life cycle. Forest ecosystems are affected by Bambusoideae seeding and death events in various ways, including an increased abundance of Apodemus spp. The utilization and preference of dwarf bamboo seeds over tree seeds by field mice remain elusive. Therefore, we aimed to determine whether field mice prefer dwarf bamboo to tree seeds. We examined one dwarf bamboo species (Sasa borealis) against four tree species with varying acorn/fruit traits (Castanea crenata, Quercus crispula, Fagus crenata, and Lindera triloba). The seeds were placed in a container in a forest among dead S. borealis culms, with an automatic camera monitoring the setup. The examined seeds were mainly foraged by two field mouse species, Apodemus speciosus and Apodemus argenteus, with preference in the following order: C. crenata, L. triloba, S. borealis, F. crenata, and Q. crispula. Our findings indicated that during S. borealis mast seeding years, predation pressure on F. crenata and Q. crispula seeds could be considerably reduced. This suggests that mast seeding might disrupt the normal pattern of survival, and seed dispersal patterns, potentially altering the forest vegetation composition.

Soil erosion decreases soil microbial respiration in Japanese beech forests with understory vegetation lost by deer

ABSTRACT Increases in the number of wild herbivores resulted in understory degradation because of their overgrazing in forest ecosystems. Deer overgrazing has occurred soil erosion in Japanese beech forests where dwarf bamboo used to be densely covered. Soil erosion can result in a decrease in soil carbon and nutrient contents, causing the soil microbial respiration in such forest ecosystems to be degraded. The objective of this study was to clarify the effects of soil erosion, which sporadically occurs within the forests, on soil properties and microbial activity. Soil erosion indices, such as the maximum height of exposed roots from the soil surface (MAXH), tree and soil properties, microbial basal and substrate-induced respiration, were measured under the canopy of 16 beech trees in each of three deciduous broadleaved forests on southern Kyushu Island, Japan. Soil properties such as the humus mass and the organic matter contents of soil and humus decreased with MAXH. Basal and substrate-induced respiration decreased with increases in MAXH. Soil properties associated with organic matter increased with basal and substrate-induced respiration. These results suggest that soil surface layers that were rich in organic matter ran off because of soil erosion, resulting in the degradation of soil microbial activity. This study suggests that increases in wild herbivore populations degrade soil ecosystem functioning owing to the soil erosion induced by understory disappearance.

Effects of Pleioblastus viridistriatus expansion on species diversity of understory vegetation and soil bacterial community in subtropical forests

As one of the most widely used dwarf bamboos, Pleioblastus viridistriatus has well-developed rhizome and root systems, which can rapidly expand into forest stands. However, little is known about the influence of P. viridistriatus expansion on the undergrowth diversity in subtropical forests of China and its association with the diversity of soil bacterial microbiota. The species diversity and soil bacterial community structure were investigated in a forest where P. viridistriatus was expanding into coniferous and broad-leaved mixed forest. We found that P. viridistriatus expansion reduced species diversity in the shrub and herbaceous layers and had significant effects on major soil physicochemical properties. In addition, the alpha diversity indexes were significantly increased and the abundance of Actinobacteria and Candidatus Saccharibacteria increased, while the abundance of Nitrospirae and Deinococcus-Thermus decreased with the increasing expansion. At the genus level, a total of 25 genera of soil bacteria showed significant difference in abundance. Overall, expansion of P. viridistriatus reduced forest species diversity, while increased soil nutrient accumulation and specific bacterial abundance to improve nutrient acquisition. Our results can provide guidance for controlling dwarf bamboo expansion and help the sustainable forest management.

Reproductive characteristics in an understory bamboo and gradual environmental changes after its dieback provide an extended opportunity for overstory tree regeneration in a mixed cool-temperate forest in central Japan.

The reproductive characteristics of understory bamboo and the effects of dieback on overstory tree seedlings through temporal changes in the environment at the forest floor have only been examined in a few bamboo species, due to the unpredictable occurrence of flowering events and long intervals between them but provide valuable information on tree regeneration and succession in a forest with dense dwarf bamboo cover. We investigated environmental conditions and assessed seedlings (< 30-cm tall) of the dwarf bamboo Sasa borealis and overstory tree species at 44-50 measurement points during 2016-2021, which included a S. borealis mass flowering event in 2017. We also conducted seed germination tests to determine germination rates and patterns in S. borealis. Environmental factors affecting seedling recruitment of S. borealis and of overstory trees were analysed using spatiotemporal generalized linear mixed models in the Bayesian framework. We observed gradual temporal changes in the environment, including increasing canopy openness and decreasing maximum height of dead S. borealis culms. The seeds germinated slowly and the emergence of current-year S. borealis seedlings peaked in spring-summer in 2019. The tree seedling density after 2019 increased significantly compared to that before the dieback. The model results suggest that tree seedling establishment was enhanced by increased light availability. Continuous field observation beginning before S. borealis dieback revealed gradually enhanced tree recruitment in response to slow decay of the remaining dead culms and slow recovery of S. borealis. The seedling regeneration pattern of understory bamboo partly contributes to a prolonged opportunity for overstory tree regeneration.

Presence of understory dwarf bamboo determines ecosystem fine root production in a cool-temperate forest in northern Japan

ABSTRACT Fine root biomass (FRB) and production (FRP) are crucial in forest carbon and nutrient cycling, but the factors controlling FRB and FRP are not well understood. Here, we examined FRB, FRP, aboveground environmental and stand factors, and soil environmental factors in four stands in a forest covered with dense understory vegetation of dwarf bamboo, Sasa senanensis (hereafter, Sasa). The four stands had different tree species composition and included a primary forest (PF), secondary forest (SF), conifer plantation (CP), and Sasa area (SA). We quantified the FRB and FRP of trees and Sasa separately using the ingrowth core method. Total FRP was higher in stands with substantial presence of Sasa (99–130 g m−2 yr−1) than in CP with scarce Sasa (69 g m−2 yr−1). Despite being occupied by Sasa alone, SA had high FRP, suggesting that the presence of Sasa regardless of trees is a key determinant of ecosystem FRP. Tree FRB increased with increasing tree aboveground biomass, tree density, or basal area at breast height, but Sasa FRB and total FRB decreased. Total FRP was also lower at higher values of these aboveground stand factors. In Sasa, specific root length was significantly higher, and root tissue density was significantly lower, than in trees, indicating the capacity of Sasa for explosive growth. Positive correlations between Sasa FRB or FRP and soil inorganic N or ammonium contents (i.e. N availability) were detected. We conclude that Sasa is important in determining FRB and FRP in this northern forest with understory vegetation.

Atmospheric ammonia deposition and its role in a cool-temperate fragmented deciduous broad-leaved forest

Forest fragmentation can increase dry deposition of atmospheric ammonia (NH3) volatilized from agricultural areas, and consequently increase spatial variability of Nr deposition within the forest (“elevated reactive nitrogen (Nr) deposition”). However, little is known about this effect and its impact on forest production in a deciduous broad-leaved forest in Asian countries. Here, we performed the field observations of atmospheric concentration and deposition of inorganic Nr gases and particles in a Japanese fragmented forest from May 2018 to April 2019. Leaf traits and growth of Japanese oak tree and understory vegetation were also measured. Atmospheric concentration and deposition of dissolved inorganic Nr (DIN) to tree canopies were measured via filter sampling and throughfall methods, respectively. Canopy retention/exchange was also estimated as a part of dry deposition using the canopy budget model. The results demonstrated that annual dry deposition of NH3 to tree canopies (4.4 kgN ha−1 y−1) was dominant in the annual total DIN deposition (7.1 kgN ha−1 y−1) at the forest edge, including the elevated Nr deposition of approximately 2 kgN ha−1 y−1. Additionally, agricultural activities such as fertilization in the area surrounding the forest likely enhanced the potential of canopy retention of NH4+, readily absorbed by tree canopy. The growth rates of tree and understory vegetation (dwarf bamboo) were higher at the edge than that at the interior, emphasizing a need for further investigation to quantify the effect of low Nr deposition (<3–5 kgN ha−1 y−1) on forest production, along with the conventional experimental studies under a high Nr deposition.

Culm dynamics of dwarf bamboo (Sasa kurilensis Makino & Shibata) in relation to forest canopy conditions in beech forests

The dynamics of understorey dwarf bamboos are an important factor in forest dynamics. Although there have been a number of recent reports about the regeneration process after the simultaneous flowering and death of bamboos, the long-term dynamics of dwarf bamboos on the forest floor and outside the regeneration process (i.e., non-flowering state) are unclear. The present study aimed to investigate the long-term changes in Sasa kurilensis Makino & Shibata (Poaceae, Bambusoidae) populations in relation to the forest canopy and environmental conditions in the primeval beech forests of Shirakami-Sanchi World Heritage Area, Japan. Ten permanent plots (2 × 5 m) were established at three study sites (1 ha) in beech forests. Each site differed in forest structure. All S. kurilensis culms were censused from 2001 to 2019. The estimated maximum longevity of culms indicated that S. kurilensis culms can survive up to approximately 7000 days, nearly 20 years. The culm density and above-ground biomass varied widely amongst the study plots, and abrupt changes were observed in some plots affected by changes in the forest canopy conditions, such as gap formation. The relationship between canopy closure and culm density in 2001 showed an inverse proportional trend that weakened in 2019, indicating that S. kurilensis developed its population under closed canopies (dark conditions). More attention should be paid to such wide variations and unstable changes in understorey bamboo populations if the dynamics of these forests are to be better understood.