Obtusa Plantation Research Articles

Enhancing Overland Flow Infiltration through Sustainable Well-Managed Thinning: Contour-Aligned Felled Log Placement in a Chamaecyparis obtusa Plantation

Contour felling is a restoration method used to decrease overland flow (OF) and soil erosion in the world. However, the impact of thinning and the placement of felled logs on OF remains inconclusive. Low ground cover and soil permeability promote OF in Chamaecyparis obtusa (Siebold et Zucc.) Endl plantations, making thinning a method for reducing runoff. We examined the relationship between OF and ground cover in a C. obtusa plantation in Japan. Event-based runoff was monitored in three plots from 2016 to 2021, with 40% thinning conducted in 2019. In plot T1, logs were randomly scattered, and, in T2, logs followed contour lines, while control plots stayed the same. After thinning, both treatment plots showed lower OF than the control plot. The ANCOVA test shows a significant slope reduction in treatment plots compared to the control plot from pre-thinning to post-thinning (T1: 0.67 to 0.26, T2: 0.66 to 0.12, p < 0.001, Tukey HSD test). However, in plot T2, OF remained stable for two years post-thinning, affirming the enduring effectiveness of contour-aligned log placement. This study backs the notion that aligning fallen logs with contour lines boosts long-term OF infiltration, supporting sustainable forest and soil management.

The Differences in Water Repellency in Root Mat (Biomat) and Soil Horizons of Thinned and Non-thinned Chamaecyparis obtusa (Siebold et Zucc.) Endl. Plantations

Water repellency (WR) is one cause of root mat (biomat) flow and soil surface runoff in dense Chamaecyparis obutsa (Siebold et Zucc.) Endl. plantations. However, the changes in WR of biomat and soil horizons are unclear in the thinned C. obtusa plantations. This study compares the WR of biomat and soil horizons in the thinned and non-thinned C. obtusa plantations by considering the water content and surface temperature of biomat and soil from July 2021 to June 2022. We selected one plot in each thinned and non-thinned area in a catchment at Obora Experimental Forest in Japan. Our results showed that the 40% thinned plot lacked a biomat horizon, whereas the non-thinned plot had a ca. 3 cm depth of biomat. The biomat WR of the non-thinned plot (none to very strong) was higher than the soil WR of the thinned plot (none to strong). There was no relationship between WR and both water content and surface temperature of biomat and/or soil in either thinned or non-thinned plots. Our findings show that the biomat horizon had an essential role in the severity of WR in C. obtusa plantations. The lack of biomat after thinning could substantially impact soil surface hydrology.

Effects of advance regeneration and germinated seedlings on forest recovery after clearcutting of Chamaecyparis obtusa plantations in Southern Kyushu, Southwestern Japan

We clarified the effect of advance regeneration on natural forest recovery after clearcutting of conifer plantations over the mid-term observation period (12–14 years to allow formation of the forest canopy). We established understory-intact plot (UI-plot), where advance regeneration (AR; DBH more than 1 cm before clearcutting) were retained, and understory-cleared plot (UC-plot), where all ARs were removed at felling of conifer crops. We surveyed individual density, species richness, and tree height with reference to different regeneration origins 1 year after and 12 or 14 years after clearcutting. Then, we compared the structural changes in UI-plot with that in UC-plot. The resprouted AR in UC-plot has provided the same effect as the retained AR in UI-plot in forming their height distribution patterns and stratification over a mid-term recovery process. We also found that individual density and species richness attributed by the individuals of newly established seedlings after clearcutting (SE), have contributed to the stand development in the both plots. Furthermore, SE was found to have a large contribution to forest recovery in terms of tree density and species number, while its significance for the recovery of gravity-dispersal, lucidophyllous trees was limited. We concluded that the advantage of AR retention is limited to the fast recovery of forest structure at the early stage after clearcutting, and mostly disappeared over a mid-term observation period as far as abundant advance regeneration was sufficiently accumulated and surrounding seed sources were effectively secured.

Communities of arbuscular mycorrhizal fungi in forest ecosystems in Japan's temperate region may be primarily constituted by limited fungal taxa.

We investigated arbuscular mycorrhizal (AM) fungal communities in secondary forests and/or Chamaecyparis obtusa plantations at eight study sites in Japan's temperate region. In the secondary forests, AM plants of the families Lauraceae, Sapindaceae, Rutaceae, Araliaceae, Rosaceae, Magnoliaceae, Cornaceae, Piperaceae, and Anacardiaceae were found. The AM fungal communities were evaluated based on compositions of the AM fungal operational taxonomic units (OTUs), which were clustered at a 97% similarity threshold of the sequences of a partial small subunit of a nuclear ribosomal RNA gene obtained from the plant roots. The compositions of AM fungal OTUs were significantly correlated with the plant family compositions and were significantly differentiated among the study sites and between the study forests. Interestingly, only 19 OTUs remained after selecting for those that had more than 1.0% of the total reads, and these 19 OTUs accounted for 86.3% of the total rarefied reads that were classified into 121 OTUs. Furthermore, three dominant OTUs constituted 48.0% of the total reads, and the most dominant OTU was found at all study sites, except at one. These results indicate that AM fungal communities are primarily constituted by limited AM fungal taxa in the forest ecosystems with diverse plant taxa in Japan's temperate region. The results of basic local algorithm search tool (BLAST) searches against MaarjAM, a database of AM fungal sequences, also revealed that the AM fungi which were the three dominant OTUs are distributed in forest ecosystems on a worldwide scale.

筑波山のスギ・ヒノキ人工林におけるコケ植物,シダ植物,顕花植物の分布と微地形との関係

筑波山のスギ・ヒノキ人工林におけるコケ植物,シダ植物,顕花植物の分布と微地形との関係

Effect of surface soil conservation by litter from shelterbelts on Chamaecyparis obtusa plantation

ABSTRACTWe investigated forest floor cover, the amount of transported soil, and litter fall in a hinoki plantation adjacent to an evergreen broadleaf forest set as the shelterbelt on a ridge in order to evaluate the edge effect on surface soil conservation for the hinoki plantation by the litter from the shelterbelt. High values of broadleaf litter fall and forest floor cover, and a low value of transported soil, were observed closer to the edge. Generalized linear modeling suggested that transported soil was strongly affected by the forest floor cover, the percentage of which was largely dependent on the broadleaf litter fall, which was mainly determined by the distance from the edge. These results suggested that the direct supply of litter from the shelterbelt conserves the surface soil of the hinoki plantation around the forest edge.

A new approach to estimate fine root production, mortality, and decomposition using litter bag experiments and soil core techniques

A new approach is proposed to estimate fine root production, mortality, and decomposition that occur simultaneously in terrestrial ecosystems utilizing sequential soil core sampling or ingrowth core techniques. The calculation assumes knowledge of the decomposition rate of dead fine roots during a given time period from a litter bag experiment. A mass balance model of organic matter derived from live fine roots is applied with an assumption about fine root mortality and decomposition to estimate decomposed dead fine roots from variables that can be quantified. Comparison of the estimated fine root dynamics with the decision matrix method and three new methods (forward estimate, continuous inflow estimate, and backward estimate) in a ca. 80-year-old Chamaecyparis obtusa plantation in central Japan showed that the decision matrix nearly always underestimated production, mortality, and decomposition by underscoring the values of the forward estimate, which theoretically underestimates the true value. The fine root production and mortality obtained by the decision matrix were on average 14% and 38% lower than those calculated by the continuous inflow estimate method. In addition, the values by the continuous inflow estimate method were always between those calculated by the forward estimate and backward estimate methods. The latter is known to overestimate the true value. Therefore, we consider that the continuous inflow estimate method provides the best estimates of fine root production, mortality, and decomposition among the four approaches compared.

急傾斜ヒノキ人工林における伐採方法の違いによる細土, 土砂, リター移動量の変化

急傾斜ヒノキ人工林における伐採方法の違いによる細土, 土砂, リター移動量の変化

Analyses of factors affecting the dynamics of coverage and number of species in understories in Chamaecyparis obtusa plantations

Analyses of factors affecting the dynamics of coverage and number of species in understories in Chamaecyparis obtusa plantations

Specific arbuscular mycorrhizal fungi associated with non-photosynthetic Petrosavia sakuraii (Petrosaviaceae)

Mycorrhizal fungi in roots of the achlorophyllous Petrosavia sakuraii (Petrosaviaceae) were identified by molecular methods. Habitats examined were plantations of the Japanese cypress Chamaecyparis obtusa in Honshu, an evergreen broad-leaved forest in Amami Island in Japan and a mixed deciduous and evergreen forest in China. Aseptate hyphal coils were observed in root cortical cells of P. sakuraii, suggesting Paris-type arbuscular mycorrhiza (AM). Furthermore, hyphal coils that had degenerated to amorphous clumps were found in various layers of the root cortex. Despite extensive sampling of P. sakuraii from various sites in Japan and China, most of the obtained AM fungal sequences of the nuclear small subunit ribosomal RNA gene were nearly identical and phylogenetic analysis revealed that they formed a single clade in the Glomus group A lineage. This suggests that the symbiotic relationship is highly specific. AM fungi of P. sakuraii were phylogenetically different from those previously detected in the roots of some mycoheterotrophic plants. In a habitat in C. obtusa plantation, approximately half of the AM fungi detected in roots of C. obtusa surrounding P. sakuraii belonged to the same clade as that of P. sakuraii. This indicates that particular AM fungi are selected by P. sakuraii from diverse indigenous AM fungi. The same AM fungi can colonize both plant species, and photosynthates of C. obtusa may be supplied to P. sakuraii through a shared AM fungal mycelial network. Although C. obtusa plantations are widely distributed throughout Japan, P. petrosavia is a rare plant species, probably because of its high specificity towards particular AM fungi.

Tree damages caused by Sika deer（Cervus nippon）bark-stripping on Chamaecyparis obtusa plantations in the Fuji-san National Forest, central Japan.

Tree damages caused by Sika deer（Cervus nippon）bark-stripping on Chamaecyparis obtusa plantations in the Fuji-san National Forest, central Japan.

Estimation of whole-stem respiration, incorporating vertical and seasonal variations in stem CO2 efflux rate, of Chamaecyparis obtusa trees

We examined vertical and seasonal variations in stem respiration rates in a 50-year-old plantation of Japanese cypress, Chamaecyparis obtusa (Sieb. et Zucc.) Endl., in central Japan, and discuss a practical and precise method to scale a point-measured stem CO2 efflux rate up to whole-stem respiration. For five selected trees, stem CO2 efflux rates were measured at breast height (1.3 m) and at five or six points above breast height (at approximately 2 m intervals) every 1 or 2 months over two consecutive years. Daily total stem respiration rate (surface area basis) was greater inside the crown than below the crown, especially during the growing season. By incorporating the vertical profile of the respiration rate, annual whole-stem respiration was estimated for each sample tree (Ry). We then compared this estimate (Ry) with another estimate of annual whole-stem respiration (R′y) obtained using a conventional method; it is assumed that the area-based respiration rate at breast height is constant throughout the stem. The ratio of these two estimates (R′y/Ry) was usually less than 1, indicating that the assumptions used to calculate R′y underestimate annual whole-stem respiration. We found that R′y/Ry was negatively correlated with the ratio of crown length to tree height (crown ratio). These results suggest that annual whole-stem respiration in this C. obtusa plantation is substantially affected by the relative proportion of within-crown stem with higher respiratory activity. Methodologically, our results imply that incorporating the crown ratio into the conventional method would improve the accuracy of annual whole-stem respiration estimates.

식생유형이 토양무척추동물 분포에 미치는 영향

전형적인 농촌지역에 발달해 있는 여러 가지 식생유형에서 함정트랩을 이용하여 토양무척추동물의 분포조사를 실시하였다. 그 결과, 채집된 토양무척추동물은 3문 6강 18목 82과 137종이었다. 출현종수는 편백이 밀식되어 있는 식재림 St. 6지점(33종)이 가장 낮았다. 목별 개체수 분포에서는 산림지역에서는 벌목이 많고, 진드기목과 딱정벌레목은 다른 지역보다 높게 나타났다. 저수지 주변 식생에서는 톡토기목이 높게 나타났고, 파리목은 다른 지역보다 높게 나타났다. 농경지에서는 거미목, 톡토기목, 벌목의 개체수가 많았다. 거미목의 경우에는 저수지와 농경지에서 월등이 높게 나타났다. 생물종다양성의 측면에서는 식생 및 서식지 유형별로 큰 차이를 나타내지 않았지만, 조사지점별로 졸참나무와 상수리나무가 혼생하는 산림지역 St. 2지점의 다양도지수가 가장 높았고, 농경지 밭둑인 St. 11이 가장 낮은 다양도지수를 나타냈다. 생물종다양성의 차이가 나타나지 않는 것에 반하여 토양무척추동물은 서식지 유형 및 식생유형별로 명확하게 4군(낙엽활엽수혼효림, 식재림 및 단순림, 저수지, 농경지)으로 구분되었다. 이러한 결과는 서식지유형별 및 식생유형에 따라서 그곳에 적응한 토양무척추동물들의 군집이 형성이 된다는 것을 의미하는 것이다. The aim of this study was to investigate whether differences in the distribution of soil invertebrates among different vegetation types (forest, reservoir, and crop land types) in rural area. A total of 18 orders and 137 species were collected by pitfall traps. Species numbers were the lowest (33 species) at the Chamaecyparis obtusa plantation (St. 6). On the forest sites, the individual number of Hymenoptera was the most abundant, and Acari and Coleoptera was the relatively more abundant than the other sites. On the reservoir sites (Salix chaenomeloides community), the individual number of Collembola was the most abundant, and Diptera was the relatively more abundant than the other sites. On the crop land sites, the individual numbers of Collembola, Hymenoptera, and Araneae were the relatively more abundant than the other orders. The density of Araneae was higher in the reservoir and crop land sites than in the forest sites. From a point of view of biodiversity, although the diversity index(H') was the highest in the mixed broad-leaved forest type (St. 2) with Quercus serrata and Q. acutissima, and the lowest in the upland levee of crop land(St. 11), there was no significant difference among the habitat or vegetation types. According to the community analysis, the soil invertebrates could be divided into 4 groups, the mixed broad-leaved forest type (A group), the plantation or pure forest type (B group), the reservoir type (C group), and the crop land type (D group).

Estimation of Soil Organic Carbon Stocks in Plantation Forest Soils of Northern Taiwan

The possibility of estimating the global carbon pools on the earth has attracted scientists for decades. In Taiwan, among remaining forested areas, 14% (about 420,000 ha) are plantation forests. There are few investigations of the soil organic carbon (SOC) pool of plantation forests in Taiwan. Nine plantation tree species, including 3 broadleaf species and 6 coniferous species were selected to estimate the SOC pools in selected plantation forest soils in northern Taiwan. The uncertainty of the estimates was examined, and strategies to obtain more-precise database for SOC pool management are proposed in this study. The results showed that only 2 Soil Orders, Inceptisols and Ultisols, were found at the study sites, and values of the soil bulk density (Bd) in broadleaf plantation forests were relatively higher than those in coniferous plantation forests. The stone contents were about 17 and 14% (0~30 cm) on average in the broadleaf and coniferous plantations, respectively. The average SOC was about 28 g kg^(-1) (0~30 cm) in the broadleaf plantations and about 48 g kg^(-1) (0~30 cm) in the coniferous plantations. The SOC pool was lowest in the Aleurites fordii plantation forest and highest in the Chamaecyparis obtusa plantation forest. We calculated that the average values of the SOC pool in the broadleaf plantation forest were about 6.5 (0~30 cm), 8.2 (0~50 cm), and 9.6 kg m^(-2) (0~100 cm). In coniferous plantation forests, they were about 7.4, 9.7, and 12 kg m^(-2), respectively. Estimation of the SOC pools in this study was potentially compromised by measurement errors of soil Bd, soil volume calculations, C determinations, and the stoniness of the soils. These sources of error might have introduced a bias, when comparing SOC contents among studies in the literature where different methodologies were applied. In conclusion, we suggest that the database of lower taxonomic categories (i.e., greater detail) for Soil Taxonomy and the SOC variability within and among pedons of the same soil type strongly need estimates of soil C stocks in Taiwan.

Effect of understory vegetations on species richness of oribatid mites in abandoned Chamaecyparis obtusa plantation within Ochozu watershed

Effect of understory vegetations on species richness of oribatid mites in abandoned Chamaecyparis obtusa plantation within Ochozu watershed

Seasonal variations of litter falls and primary consumption by herbivorous insects in Chamaecyparis obtusa plantations in Owase, Mie Prefecture and Kamikitayama, Nara Prefecture

Seasonal variations of litter falls and primary consumption by herbivorous insects in Chamaecyparis obtusa plantations in Owase, Mie Prefecture and Kamikitayama, Nara Prefecture

The influences of understories on infiltration rates in Chamaecyparis obtusa plantations (II) Laboratory experiments

The influences of understories on infiltration rates in Chamaecyparis obtusa plantations (II) Laboratory experiments

The influences of understories on the infiltration capacities of Chamaecyparis obtusa plantations (I) Experimental results using a mist type rainfall simulator

The influences of understories on the infiltration capacities of Chamaecyparis obtusa plantations (I) Experimental results using a mist type rainfall simulator

The role of different sources of tree regeneration in the initial stages of natural forest recovery after logging of conifer plantation in a warm-temperate region

We analyzed the role of regeneration type (surviving from advanced regeneration, resprouting from advanced regeneration, or newly recruited seedlings) in determining the quantity and quality of individuals in reestablishing a natural forest following clear-cutting of a conifer plantation. We experimentally clear-cut a plantation and undertook a detailed tree census before and after clear-cutting. After clear-cutting, a species composition partially representing warm-temperate evergreen broadleaf forest was present in the form of surviving and resprouted individuals originating from advanced regeneration that had established in the Chamaecyparis obtusa plantation. On the other hand, seedlings that established after clear-cutting were dominated by pioneer species, and the number of seedlings was far greater than the number of individuals originating from advanced regeneration. Our results suggest that the role of regeneration type would differ in relation to the objectives for forest recovery. When any kind of woody cover of the ground surface after clear-cutting would suffice, we suggest that the contribution of pioneer seedlings originating from buried seeds would be important. If the recovery objective is to form a simple evergreen broadleaf forest, such as a coppice woodland, all three sources of regeneration would play a similar role, provided the understory before clear-cutting was as well developed as the one in this study. If rapid establishment of a lucidophyllous forest with diverse species composition is desired, the role of the surviving and resprouting individuals originating from the advanced regeneration would be much more important.

Attraction of female Japanese horntail Urocerus japonicus (Hymenoptera: Siricidae) to α-pinene

The attraction of Urocerus japonicus to volatile chemicals, which discolors the wood of conifers, was examined in the field. Attracting effects of α-pinene and ethanol that were suggested to be effective as attractants were compared to U. japonicus with Hodoron®, which has been used as an attractant for woodwasps. Adults of U. japonicus were captured in chemically treated adhesive traps, which were set up in a hinoki Cypress Chamaecyparis obtusa plantation. More female adults of U. japonicus were captured in traps with α-pinene or Hodoron® than in those without chemicals. There was no significant difference between the number of captured females in traps with α-pinene and those with Hodoron®. There were also no significant differences in the number of captured males among treatments. Traps with ethanol did not attract either sex of U. japonicus. It was indicated that both α-pinene and Hodoron® have attracting effects on female U. japonicus.