Effects of differences in forest floor and canopy vegetation on ectomycorrhizas ofBetula platyphylla var.japonica: A test using seedlings planted into soils taken from various sites

Effects of different forest floor vegetation types in secondary forest and of conversion to plantation on the quality and quantity of ectomycorrhizas are mostly unknown.Betula platyphylla var.japonica seedlings were used for bioassays of ectomycorrhizal fungal inoculum using soils from four 50-year-oldB. platyphylla var.japonica forests that had different types of forest floor vegetation: two with shrub types, one with aSasa type, and one with a grass type. Seedlings were also grown in soil from a nearby monospecific plantation ofChamaecyparis obtusa. Ectomycorrhizas formed 13 to 26% of root length of seedlings grown in soil from the five different sites. The maximum percentage of ectomycorrhizal formation was obtained from the grass-type forest. The dominant type of ectomycorrhiza in the two shrub-type forest soils was the same as that in theSasa-type forest soil. The dominant types of ectomycorrhizas in the grass-type forest soil and in theC. obtusa plantation soil were different from that in the two shrub-type forest soils and in theSasa-type forest soil. The results of this investigation suggest that the type of forest floor vegetation, accompanied with changes in thickness of the A₀ horizon, might affect the ectomycorrhizal fungi in the soils ofB. platyphylla var.japonica forests. Establishment of artificial plantations ofC. obtusa might change the ectomycorrhizal fungi that could associate withB. platyphylla var.japonica seedlings in soil.     

The relationship between sap flow rate and diurnal change of tangential strain on inner bark in Cryptomeria japonica saplings

The relationship between sap flow rates and diurnal fluctuation of stems was investigated in cloned 3-year-old saplings of Cryptomeria japonica D. Don grown in a phytotron with irrigation every 2 days. The improved stem heat balance method and a strain gauge were used to measure sap flow rate and diurnal fluctuation of the stem. The sap flow rate reacted to lighting conditions, increasing and decreasing immediately after lights-on and lights-off, respectively. The tangential strain on the surface of the inner bark exhibited a reaction that followed but opposed the reaction of the sap flow rate to lighting conditions. Based on the changes in sap flow rate, there seemed to be four phases in diurnal sap flow: phase A₁ began with lights-on, when the sap flow rate increased, and lasted about 2 hours. In the following phase, A₂, the sap flow rate remained almost constant at 1.3 g/min for about 10 h, and then declined for about 2 h as lights-off approached. In phase B, the early period of darkness, the sap flow declined quickly and then more slowly, for about 4 h, until the start of the second dark period, phase C, when the sap flow rate became almost constant at 0.05 g/min for about 6 h. The first derivative of each sap flow rate and the corresponding tangential strain were calculated, and the results indicated a negative correlation between the two variables in all periods. In particular, the relationship between the first derivative values exhibited a highly negative correlation in phases A₁ and B, expressed as a primary formula. Sap flow rate was found to continue for some time after lights-off, and this compensated for reduced evaporative effects, albeit at a slow rate, over 4 h. The total amount of sap flow in the dark was only about 9% of that in the light, disregarding transpiration in the dark for simplicity. Thus, the total amount of sap flow responsible for swelling of the stem was about 9% of that consumed in transpiration during the light period.     

Dihydroroseoside, a new cyclohexanone glucoside, from the leaves of shirakamba (Betula platyphylla Sukatchev var.japonica Hara)

A new cyclohexanone glucoside (II) and a known cyclohexenone glucoside roseoside [I, (6S, 9S)-6-hydroxy-6-(9--D-glucopyranosyloxy-trans-7-butenyl)-1,5,5-trimethyl-1-cyclohexenone] were isolated from an ethanol extract of shirakamba (Betula platyphylla Sukatchev var.japonica Hara) leaves. The structure ofII was determined to be (6S, 9R)-6-hydroxy-6-(9-O--D-glucopyranosyloxy-trans-7-butenyl)-1, 5,5-trimethyl-1-cyclohexanone by¹H-NMR and¹³C-NMR spectroscopic analyses. It was named dihydroroseoside.     

Recovery of canopy trees and root collar sprout growth in response to changes in the condition of the parent tree after a fire in a cool-temperate forest

The relationship between the recovery of canopy trees after fire and root collar sprout dynamics was investigated during 1998–2000 in a secondary cool-temperate broad-leaved forest consisting of Quercus mongolica var. grosseserrata and Betula platyphylla var. japonica trees, in northern Hokkaido, Japan, which burned in April 1998. All of the Betula trees that were severely damaged, two-thirds of those slightly damaged, and half of those intact in 1998, died within three growing seasons after the fire. By contrast, half of the Quercus trees that were slightly damaged and half of those severely damaged recovered their foliage, and no slightly damaged or intact trees died during the three growing seasons after the fire. Many Betula trees developed several fruiting bodies of wood-destroying fungi on their stems, irrespective of damage severity. Fungi also infected some of the surviving Quercus, although the crowns tended to recover. Although many sprouting Betula were observed in 1998, the number of sprouts declined rapidly over the study period. Multiple regression analyses showed that the survival and growth of Betula sprouts were positively influenced by the number of sprouts in 1998, damage severity in 1998, and the degree of recover or decline during the study period, and were negatively influenced by parent tree size. On the other hand, a few sprouts of Quercus remained alive. Quercus remained dominant and the dominance of Betula was rapidly reduced after the fire. However, many Betula sprouts remained alive. Stand structure will change drastically for the time being.     

Distribution of ectomycorrhizas and ectomycorrhizal fungal inoculum with soil depth in a birch forest

The distributions of ectomycorrhizas and ectomycorrhizal fungal inoculum with soil depth (0–45 cm) were determined in a 40-year-oldBetula platyphylla var.japonica forest. Mycorrhizal and non-mycorrhizal fine roots were measured in each soil core sample that was collected at soil depths of 0–5, 5–10, 10–15, 15–20, 20–25, 30–35, and 40–45 cm. The ectomycorrhizas were mainly distributed (>50%) in the top soil (0–5 cm) of organic forest floor horizons. Below 5 cm the quantity of ectomycorrhizas decreased sharply. The percentage of fine roots which were ectomycorrhizal gradually declined with the depth of soil. The ectomycorrhizal fungal inoculum was evaluated by a bioassay method, measuring the lengths of the entire root system and of the ectomycorrhizal roots of birch seedlings planted in each soil sample. The soil samples were collected from 0–5, 10–15, 20–25, 30–35, and 40–45 cm depths of the soil profile. Ectomycorrhizal formation on birch seedling roots in the bioassay was high in both the soil depth intervals 0–5 cm and 10–15 cm, while the amount was lower in the soil depth interval from 20–45 cm. The results of these investigations show that the amount of the ectomycorrhizas in soil, and the ectomycorrhizal fungal inoculum potential as determined by bioassay, are not always consistent with each other.     

Comparison of terpenes in extracts from the resin and the bark of the resinous stem canker of Chamaecyparis obtusa and Thujopsis dolabrata var. hondae

A monoterpene and 15 diterpenes were isolated from the ethyl acetate extracts of the bark-glued resin from the resinous stem canker ofThujopsis dolabrata var.hondae Makino. A monoterpene (nezukone20) and 4 diterpenes (acetyl torulosol5, acetyl isocupressic acid8, acetyl abietinol11, and 7-methoxytotarol18) were characteristic constituents of the ethyl acetate extracts but were absent in then-hexane extracts from the resinous stem canker ofT. dolabrata var.hondae. These terpenes were first isolated fromT. dolabrata var.hondae andT. dolabrata. The available literature suggests that diterpene18 is a new compound. The resinous stem canker ofChamaecyparis obtusa Endlicher contained larger amounts of manool1,trans-communic acid6, and ferruginol12 and smaller amounts of isocupressic acid7 and abietinol10 than the resinous stem canker ofT. dolabrata var.hondae. The concentration of18 was less than 2% in the extracts, and the resinous stem canker ofC. obtusa lacked this compound. The resinous stem cankers ofC. obtusa andT. dolabrata var.hondae provided extracts 15.6 and 4.96 times, respectively, heavier than the healthy ones. Large differences in the ratios and compositions of terpenes were also observed between the resinous stem canker and the healthy trees. Terpenes isolated from the extracts contained many kinds of diterpene, especially the labdane-type diterpenes, in these diseased trees. These results suggest that the presence of labdane-type diterpenes is closely associated with the resinous stem canker or the causal fungi of this disease.Part of this report was presented at the 50th annual meeting of the Japan Wood Research Society, Kyoto, April 2000     

Hypoglycemic and antidiabetic activities on the stem bark aqueous and ethanol extracts of Musanga cecropioides in normal and alloxan-induced diabetic rats

Daily oral administration of the aqueous and ethanolic extracts of Musanga cecropioides stem bark in normal and diabetic rats at doses of 250, 500 and 1000 mg/kg/day, for 14 days significantly lowered the fasting plasma glucose levels in normal and alloxan-induced diabetic rats in dose-dependent fashion. The ethanol extract induced more significant antidiabetic effect than the aqueous extract.     

Effects of the absorption of artificial acidic solutions on the root systems of Japanese red cedar (Cryptomeria japonica D. Don) cutting and saplings

The effects of the absorption of artificial acidic solutions only from below-ground parts on root systems were examined for 60 days in summer and 72 days in fall using cuttings and saplings of Japanese red cedar (Cryptomeria japonica D. Don). Cuttings and saplings absorbed the solutions through the potted soils from the reservoir of an autoirrigator and/or a simplified-autoirrigator. Nitric acid solutions of pH 2.0, 4.0 and 6.0 and distilled water (control) were used in summer, mixtures of H₂SO₄ and HNO₃ solutions of pH 2.0, 3.0 and 4.0, HNO₃ solution of pH 3.0, H₂SO₄ solution of pH 3.0 and distilled water (control) were used in fall. Although no detrimental effects of acidic solutions on saplings were observed, the rooting rate of cuttings treated at pH 2.0 in summer was significantly lower than that of the control. Root lengths and root dry weight per cutting at pH 2.0 in summer and fall were smaller than those of the control, and the difference in fall was significant. The present study revealed that the acidic treatment only from below-ground parts had detrimental effects on the root systems of cuttings, suggesting the importance of quantification of the effects on below-ground parts, as well as on above-ground parts, to evaluate the effects of acidic precipitation on trees.     

Relationship between resistance to vole browsing and content of ether extract in the bark of larch species and hybrids

We determined the survival rate of tree families produced by the intra- and interspecific crossing of larch species damaged by browsing of vole (Clethrionomys rufocanus bedfordiae Thomas) and the contents of ether extracts (EE) in their bark. The average survival ofLarix gmelini var.japonica Pilg. (L. gmelini)×L. gmelini (G×G) was highest, followed by the hybridL. gmelini×L. leptolepis Gordon (G×L). The families of the hybrid G×L, which is considered suitable for silviculture in Hokkaido, Japan, showed significant differences in survival rates, suggesting that it is possible to produce improved varieties of the hybrid which are more resistant to vole browsing. The EE contents of the bark were under strong hereditary control, and the rank of the EE content among the various families hardly fluctuated between the location of the test fields. The correlation coefficient between the survival rates and the EE contents was highly significant (r=0.89,n=24,p<0.01), indicating that the EE content in the bark may be used as a possible index of resistance or susceptibility to vole browsing in larch plantations. A part of this report was presented at the 106th Annual Meeting of the Japanese Forestry Society, at Sapporo, April, 1995.     

Distinction of resin compounds between the healthy bark and the resinous stem canker of <Emphasis Type="Italic">Thujopsis dolabrata</Emphasis> var. <Emphasis Type="Italic">hondae</Emphasis>

Methyl esters of higher fatty acids were detected from the healthy bark of Thujopsis dolabrata var. hondae but not from the bark of the resinous stem canker of T. dolabrata var. hondae. This difference enabled us to distinguish healthy trees from diseased ones. Fourteen diterpenes were also isolated from the n-hexane extracts of the bark-glued resin taken from the resinous stem canker of T. dolabrata var. hondae. Of these diterpenes, abietane diterpenes [abieta-7,13-diene (1), abietinol (2), dehydroabietinol (4)], pimarane diterpene [sandaracopimaric acid (8)], and labdane diterpenes [manool (10), torulosol (11), torulosal (12), cupressic acid (13)] were first isolated from T. dolabrata var. hondae.Part of this paper was presented at the 47th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999     

The process of decline of an endangered tree species,Pinus armandii Franch. var.amamiana (Koidz.) Hatusima, on the southern slope of Mt. Hasa-dake in Yaku-shima Island

The process of decline of an endangered tree species,Pinus armandii var.amamiana, was monitored on the southern slope of Mt. Hasa-dake in Yaku-shima Island from 1994 to 1998. There are 163 trees ofP. armandii var.amamiana over 1.3 m in height. They are distributed on steep ridges and rocks with a thin soil layer mostly consisting of friable granite. During the monitoring period, 21 trees ofP. armandii var.amamiana died and the mortality rate was 12.9%. Dead trees were categorized into three types: standing, uprooted and landslide. The uprooted- and landslide-typed dead trees were found only after a severe typhoon struck Yaku-shima Island. This suggests that the combination of fragile site conditions and severe typhoons play an important role in the process of decline ofP. armandii var.amamiana. The standing-typed dead trees were presumed to have been killed by pine wilt disease, accounting for 71.4% of the dead trees. However,Bursaphelenchus xylophilus, the cause of pine wilt disease, was not detected from any of the wood chips or branch samples from the standing-typed dead trees ofP. armandii var.amamiana. This might indicate that some factor(s) other than pine wilt disease could be responsible for the standing-typed death ofP. armandii var.amamiana in natural habitats. A part of this paper was presented at the 109th Meeting of the Japanese Forestry Society.     

Effects of deer browsing on the survival and growth of <Emphasis Type="Italic">Abies homolepis</Emphasis> and <Emphasis Type="Italic">Picea jezoensis</Emphasis> var. <Emphasis Type="Italic">hondoensis</Emphasis> seedlings after fencing on Mt. Ohdaigahara

We evaluated the survival and growth of Abies homolepis and Picea jezoensis var. hondoensis seedlings on Mt. Ohdaigahara, where the population of sika deer (Cervus nippon) is high and an experimental fence has been in place for 13 years. No significant differences were detected in the survival of small seedlings between fenced and unfenced plots. The growth of A. homolepis was significantly higher in the fenced plot, but growth of P. jezoensis var. hondoensis did not show significant differences between fenced and unfenced plots. Seedlings of height ≤5 cm in the forest floor vegetation of the unfenced plot were probably too small for deer to find and browse, so they survived.