Abstracts of Nippon Nojohiryogaku Zasshi

Abstract

P type humic acid which has absorption bands near 615, 570, and 450 run due to the presence of dihydroxyperylenequinone (DHPQ) was investigated by gel-chromatography. Humic acid samples were fractionated using Sephadex G-50 as gel material and 0.1 n NaOH, with or without 1.5 m urea, as eluent. The absorption spectra of the effluent fractions were measured, and elution curves were drawn on the basis of the optical density at 600 nm.

In general, the intensity of the absorption bands due to DHPQ increased with increasing fraction number, accompanied by a change in effluent color from brown, greenish brown to green. Based on the elution curves, the effluent fractions of a humic acid containing a large amount of the green fraction were divided into six groups: B₁, B₂, BG, G₁, G₂, and G₃. These fraction groups, especially the G groups and cercosporin, a dihydroxyperylenequinone pig ment, were compared by absorption spectroscopy, ultrafiltration, ultimate analysis, TLC, and gel-chromatography.

The green fraction was composed of a non-humic, relatively lower-molecular weight polymer containing a considerable amount of DHPQ nucleus, while the brown humic fraction still maintained the characteristic light absorption due to DHPQ. It may be tentatively con cluded that the green fraction is not only a co-extracted impurity, but is also firmly associated with dark-colored humic substances.     

Chemical studies on soil humic acids

Abstract

Relationships between elementary compositions and types of humic acids or the "degrees of humification were studied statistically using 39 humic acids prepared from various types of soils. Mean values of C%. H%. N%, 0%, H/C, N/C, and O/C of the different types of humic acids (A. B. Rp(l), Rp(2). and Po) were compared. The elementary compositions of various types of humic acids were proven by variance analyses to be significantly distinct. Linear regression analyses of C%, H%, N%. 0%, H/C, N/C, or O/C on RF or AlogK values were also carried out on 35 humic acids excluding the P_+~+++ type humic acids. The linear associations were found to be significant between C%-RF (5% level), H%-RF, H%-?logK, H/C-RF and HIC-?logK (0.1% level), N/C-RF(O.1% level). N%-RF(l% level), N%-?logK N/C-?logK(5% level), and ?logK (1% level), while no significant relationship was found with regard to C%;-?logK, 0%-?logK (both 5% level) and O/C-RF and O/C-?logK (l0% level). Carbon and oxygen contents of humic acids may be apt to reflect the different conditions of soils. The deeper the visible light absorption of humic acids and so the higher the degrees of humification, the lower the hydrogen contents of humic acids were. Though nitrogen content showed a trend similar to the trend of hydrogen content against RF values as a whole. the nitrogen content of less humified humic acids (Rp type) varied from very low to very high values. suggesting the enrichment of nitrogen into humic acid molecules in the early stage of humification. In the H/C versus O/C diagram, humic acids occupied an area reserved for the oxydation products of lignins. The area was fairly wide and “J”-shaped, that is, in the early to the middle stage of humification humic acids were arranged in the direction of dehydrogenation or demethanation, and in the later stage they were arranged in the direction of dehydration.     

Stand-scale transpiration estimates in a Moso bamboo forest: II. Comparison with coniferous forests

In western Japan, Moso bamboo (Phyllostachys pubescens) forests have been expanding by replacing surrounding vegetation such as coniferous plantation forests and natural broadleaved forests. It has been speculated that the replacement of surrounding vegetation by bamboo forests could alter the vegetation water cycle and available water resources. We quantified stand-scale transpiration (E) in a bamboo forest on the basis of sap-flux measurements and compared the E value with values for coniferous forests. The annual E was estimated to be 567 mm. Seasonal trends in E primarily corresponded to seasonal trends in the vapor pressure deficit. Annual E for the bamboo forest was higher than that for the coniferous forests by 12% of annual precipitation (P). This difference in annual E is comparable with the difference in annual interception evaporation (I) relative to P between bamboo and coniferous forests; previous studies reported lower I for bamboo forests by ∼10% of P. Thus, the sum of E and I was comparable for bamboo and coniferous forests. As this study is the first measuring E of bamboo forests, further studies are required to examine the generality of our results.     

Transpiration and canopy conductance at two slope positions in a Japanese cedar forest watershed

Plant–soil system patterns and processes along a slope are among the greatest causes of uncertainty in estimating watershed-scale transpiration (E). Tree-to-tree and radial variations in xylem sap flux density (F_d), in addition to tree biometrics, were measured over a 2-year period (2005–2006) in two slope stand positions. The areas of interest consisted of an upper slope plot (UP) and a lower slope plot (LP) in a Japanese cedar (Cryptomeria japonica D. Don) forest watershed and the environmental controls of stand E for each plot were compared. Canopy stand E (E_C) and canopy stomatal conductance (G_C) in the UP were less than those in the LP during the growing season, while those in the UP were greater than those in the LP over winter. In addition, mean stand F_d (J_S) in the UP was greater than that in the LP over winter, but J_S values were similar in the UP and LP except in the winter, which allows us to extrapolate watershed-scale E based on J_S estimated from F_d measurements of a partial stand in the watershed. However, this relationship contains a bias and differed between 2005 and 2006. Although there were significant differences in soil moisture conditions between the UP and LP in both years, a systematic relationship between the similarity in J_S and soil moisture conditions was not found. The bias was due to a tendency for J_S in the LP to be greater than that in the UP in 2006. This tendency was amplified because J_S in the LP was greater than that in the UP around an atmospheric humidity deficit (D) of 1–1.5 kPa and frequencies of this D range were higher in 2006 than in 2005. The greater J_S in the LP at D  1–1.5 kPa could be explained by the difference in the response of G_C to D between the UP and LP. Our results suggest this to be the cause of the similarity in J_S values for the UP and LP and for the occasional abortion of its similarity. However, even when the bias or the occasional deviation is disregarded, the error in estimating stand E from a partial stand is so small that it is comparable to an F_d measurement error. For example, the error when using only the LP was 6.6% for stand E.     

Seasonal changes of azimuthal,radial, and tree-to-tree variations in sap flux affect stand transpiration estimates in a <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> forest,central Taiwan

Stand transpiration (E) estimated using the sap flux methods is affected by the azimuthal, radial, and tree-to-tree variations of sap flux. Although several studies have examined the relative importance of the three variations in estimating E, the seasonality of the three variations remains unknown. In the current study, we attempted to clarify whether the relative importance of these three variations could show seasonal changes. Using sap flux data measured in a subtropical cloud forest from August 2010 to July 2011, we calculated the differences resulting from omitting the three variations in estimating E. The effects of the three variations in estimating E showed seasonality. The azimuthal and tree-to-tree variations were more pronounced during winter, whereas the radial variation was more pronounced during summer. However, the effect of tree-to-tree variation was consistently much larger than the other two variations throughout the study period. The tree-to-tree variation is more important in estimating E monthly, seasonally and annually than both the azimuthal and radial variations, although all three variations have shown seasonality. In addition, the sensor allocation for summer would be acceptable for the practical estimation of E if aiming at the long time scale.     

Rainfall interception in a moso bamboo (Phyllostachys pubescens) forest

In recent years, moso bamboo (Phyllostachys pubescens) forest areas in Japan have rapidly expanded, and bamboo is now invading nearby natural or plantation forests. To date, only one study has examined the rainfall interception of a moso bamboo forest. In that study, it was reported that the interception ratio (interception/rainfall) of the bamboo forest did not exceed the interception ratios of other natural and plantation forests (n = 4) in Japan. To expand the current state of knowledge about rainfall interception of bamboo forests, we measured throughfall and stemflow at another bamboo forest site. Annual rainfall (Rf), throughfall (Tf), and stemflow (Sf) during the measurement period were 2,105, 1,556, and 322 mm, respectively. Annual rainfall interception at the plot (I) was 228 mm. Tf/Rf, Sf/Rf, and I/Rf were 73.9, 15.3, 10.8%, respectively. I/Rf was less than 20% throughout the year except in October, the month with lowest rainfall. We also summarized rainfall interception data from 19 other natural and plantation forests. The I/Rf value of our site did not exceed the I/Rf values of these natural and plantation forests (n = 19). Our data will be useful for assessing changes in water resources that result from replacement of natural or plantation forests by bamboo forests.     

Aromatic constituents of humic acids released by na-amalgam reductive cleavage,koh fusion and zinc dust fusion

Eight humic acids showing different degree of humification were treated with HCI (1:1). The hydrolyzed humic acids were subjected to reductive cleavage with Na-amalgam, KOH fusion and zinc dust fusion. The yields of degradation products were determined by colorimetry gas chromatography.

The perimental results Were summarized as follows:

l. The amounts of ether-soluble substances obtained by reductive cleavage with Naamlagan ranged from 21.6% for Kuragari (A type) to 7.8% for Kisokoma B₂ (Rp type). The yields of phenolic substances expressed in terms of vanillic acid content ranged from 3.0% for Kuragari (A type) to 1.8% for Kisokoma B₂ (Rp type). Resorcinol. p.hydroxybenzoic acid, vanillic acid, protocatechuic acid and syringic acid were detected in the gas chromatograms of the ethe-soluble substances and their total yield comprised less than 0.6% of the Kisokoma F (Rp type).

2. The KOH fusion of humic acid yielded a larger amount of degradation products as compared to reductive cleavage. The amount of ether-soluble substances ranged from 42.7% for Kisokoma F (Rp type) to 12.6% for Sochiken 1 (A type). The yields of phenolic substances, expressed in terms of amount of protocatechuic acid, ranged from 10.6% for Kisokoma F (Rp type) to 4.6% for Inogashira (A type). Exept for syringic acid, the same compounds released after ramged from 2.1% for Sochiken 2 (B type) to 0.4% for Sochiken 1 (A type).

3. The amounts of benzene-soluble substances and hydrocarbons obtained from Goshikigahara (P type) by zinc dust fusion were 20.9% and 5.2%, respectively. The yields of the hydrocarbons tended to increase in the order; P type > Rp type ≥ B type. Perylene and 2-methylanthracene were detected in the gas chromatograms of the hydrocarbons fractions and, in the case of Goshikigahara (P type), their yields were 0.031% and 0.010%, respectively.     

Elementary composition of humic acids

The author made a study of the elementary composition of various humic acids; L and SrL humic acids used in the previous report¹⁾, and two lowmoor humic acids.     

Combination reaction between humic acid and calcium ions

In the previous paper (1), liming an acid humus volcanic ash soil resulted in the formation of humic acids combined with calcium, but had no significant effect on acid brown forest soils containing humic acids of a lower degree of humification. Subsequently, the authors examined the humus composition of the soils treated with calcium acetate, and conducted some experiments on the combination reaction between humic acid and calcium ions. The results obtained are presented in this paper.     

Mineralization of physically fractionated rotten plant residues under upland conditions

A well-rotten mixture of rice straw and calcium cyanamide (rice straw compost prepared indoors) was separated physically into four fractions using a combination of methods which involved sieving, sedimentation and centrifugation. The four fractions obtained were Fl-3 (>0.043 mm), F4 (sedimented at 4°C), F5 (sedimented by centrifugation at 10⁴ × g for 10 min) and F6 (supernatant). The air-dried and pulverized fractions were mixed with upland soils and incubated for 4 weeks at 30°C under upland conditions. The amount of nitrogen mineralized in each fraction was determined, In a red yellow soil, 11.2% of the organic nitrogen present in the unfractionated, air-dried sample was mineralized, compared with 6.8% in volcanic ash soil. The contribution of fraction F5 to the total amount of mineralized nitrogen in wet compost was the highest, followed by F6. Fraction Fl-3 showed immobilization of inorganic nitrogen in both soil types. On the other hand, fractionated samples obtained after air-drying the wet compost showed no immobilization for Fl-3, although the values obtained for other fractions were similar to those obtained for the corresponding fractions of wet compost.

Well-rotten plant residues such as rice straw (compost prepared outdoors), Timothy and Ladino clover were air-dried, then separated into fractions and analyzed for elementary composition as well as inorganic nitrogen content using the same procedures. Although the amounts of mineralized nitrogen were higher in fractions F5 and F6 compared with other fractions, the values were much lower compared with those of undecomposed plant residues.

It was found that the amount of organic nitrogen mineralized in soil was affected not only by the C/N ratio of the plant residues but also by the differences in characteristics or properties of the plant materials and soils.