超高产夏玉米田土壤微生物与土壤酶的动态变化

为揭示超高产夏玉米田（产量>15 000 kg·hm^-2）土壤微生物与土壤酶活性动态变化特性,在国家玉米工程技术研究中心（山东）试验场进行夏玉米生长季农田土壤微生物与土壤酶活性研究. 在连续3年产量15 000 kg·hm^-2以上的超高产夏玉米田中选择一块超高产田（HF, 产量为20 322 kg·hm^-2）与常规生产田（CF, 产量为8920.1 kg·hm^-2）进行对比分析,主要测定0～20 cm土层土壤细菌、真菌与放线菌数量及脲酶和转化酶活性. 结果表明：播种后超高产田与常规生产田土壤微生物（细菌、真菌与放线菌）数量均表现出先升高后下降的趋势,超高产田在玉米生长后期土壤微生物数量低于常规生产田,细菌与放线菌表现尤其明显,收获期超高产田B/F值（细菌与真菌数量比）比播种期高2.03倍,比常规生产田高3.02倍,常规生产田收获期与播种期的B/F值变化不显著;超高产田土壤脲酶活性在播种31 d（拔节期）后低于常规生产田,转化酶活性播种58 d（开花期）后快速下降,低于常规生产田.     

Vertical Profile of Phosphatase Activity in the Sundarban Mangrove Forest,North East Coast of Bay of Bengal,India

Impact of phosphate solubilizing bacteria along with soil phosphatase activity on phosphorous cycle was found to be quiet interesting in the Sundarban mangrove ecosystem. Soil phosphatase activity showed a decreasing pattern with increase in depth [soil phosphatase activity (μg pnp produced g^?1 dry wt of soil) = 906.85 – 5.6316 Depth (cm)] from the deep forest region of the Sundarban forest ecosystem. Soil salinity showed a very little effect on soil phosphatase activity whereas soil temperature and pH was found to show significant impact on the soil phosphatase activity. This ensured that the microbes associated with phosphate mineralization present in the Sundarban forest ecosystem are more tolerant to fluctuation in salinity than that of temperature and pH. A direct correlation was perceptible between the number of phosphate solubilizing bacteria and phosphatase activity in the soil during the study period from 2007 to 2012. Soil phosphate concentration was found to be directly governed by the soil phosphatase activity [The regression equation is: avg PO₄^?3-P (μg g^?1 dry wt of soil) = 0.0311 + 0.000606 soil phosphatase activity (μg pnp produced g^?1 dry wt of soil); R² = 63.2%, p < 0.001, n = 62].     

Activity and species composition of aerobic methanotrophic communities in tundra soils

The low-temperature, methane-oxidizing activities and species composition of methanotrophic communities in various tundra bog soils were investigated by radioisotopic and immunofluorescent methods. Methanotrophic bacteria carried out the methane oxidation process through all horizons of seasonally thawed layers down to permafrost. The highest activity of the process has been observed in the water surface layer of overmoistured soils and in water-logged moss covers. Up to 40% of¹⁴CH₄ added was converted into¹⁴CO₂, bacterial biomass, and organic exometabolites. By immunofluoresecent analysis it was demonstrated that the representatives of I+X (Methylomonas, Methylobacter, andMethylococcus) and II (Methylosinus, Methylocystis) methanotrophic groups occurred simultaneously in all samples at 61.6% and 38.4%, respectively. The number of methane-oxidizing bacteria in the ecosystems studied was 0.1–22.9×10⁶ cells per gram of soil. Methanotrophic organisms ranged from 1% to 23% of the total bacterial number.     

Effects of clear-cutting and burning on characteristics of nitrogen mineralization and microbes in the forest soil of a Pinus massoniana plantation in Southern China

The aim of this study was to clarify the effects of clear-cutting and burning (CCB) on soil fertility in a Pinus massoniana (Masson pine) plantation after CCB in Fujian Province, China. We investigated changes in nitrogen (N) mineralization potential (N₀), N mineralization rate constant (k) and the apparent activation energy (Ea) of the soil, with a mathematical analysis using a kinetics model based on the results of in vitro incubation. Changes in the amount of microbial biomass nitrogen (MBN), as well as the number of heterotrophic and nitrite-oxidizing bacteria, were also investigated. The N₀, MBN and the number of fungi and actinomycetes in forest soil was reduced for at least 18 months after CCB. The number of heterotrophic and nitrite-oxidizing bacteria increased, and k, Ea and N mineralization became greater after 6 months of CCB, compared with the control plots. Because there were few young trees planted, which would have taken up mineralized N in the post-CCB site, it is probable that a high proportion of the mineralized N that accumulated in the soil may have been lost during the summer rainy season. Therefore, it is suggested that CCB led to a deficiency in available N during short rotations, which resulted in soil degradation.     

Activity of nitrifiers in relation to nitrogen nutrition of plants in natural ecosystems

Three aspects of the nitrate production in natural ecosystems are discussed,i.e. the population biology of nitrifying bacteria, the nitrate-producing activity of these organisms and the uptake of nitrate by higher plants. It is concluded that the three methods used in enumerating the nitrifying bacteria,i.e. the Most Probable Number method, the Fluorescent Antibody technique and the Potential Nitrification Rate, all have serious drawbacks and count different segments of the nitrifying populations.From the number of nitrifying bacteria no reliable estimate of the rate production can be obtained and also estimates that are made using field-incubation and¹⁵N–NH ₄ ⁺ techniques do not yield reliable data. Possibly the best results can be obtained using Schimel's method to estimate the actual nitrification rate using¹⁵N–NO ₃ ^– , but this method has still not been tested under different sets of soil conditions.From the nitrate reductase activity and the chemical composition of the plant a picture can be obtained of the quantities of nitrate and ammonium that have been taken up. However, it is shown that nitrate and ammonium are taken up in different proportions that they are produced. It is concluded that the various parameters have to be studied simultaneously, preferably in defined systems with plants, in which the participating organisms are known.     

降香黄檀土壤微生物数量的时空动态特征

【目的】研究降香黄檀土壤微生物数量在时间和空间上的动态特征,可为降香黄檀栽培技术的完善提供数据支持。【方法】采用稀释平板涂布法,比较分析降香黄檀根际和非根际土壤微生物三大类群(细菌、放线菌、真菌)数量的季节及垂直分布情况。【结果】(1)降香黄檀根际和非根际土壤均表现为春季细菌、真菌数量较多,冬季细菌数量较少,秋季真菌数量较少;非根际土壤放线菌冬季数量较多,秋季数量较少。(2)细菌的根际效应最为明显,其R/S为0.12~62.96;真菌次之,其R/S为0.22~2.46;放线菌的根际效应较小,其R/S为0.32~1.01。(3)降香黄檀上层土(0~20 cm)的微生物数量普遍高于其他土层;随着土层加深,微生物数量表现为逐渐下降或先下降后升高2种变化趋势。【结论】降香黄檀土壤微生物数量的分布受季节和土层的影响。     

Sulfur dynamics in mineral horizons of two northern hardwood soils. A column study with 35S

Sulfur dynamics of two Spodosols were ascertained using soil columns constructed from homogenized mineral soil from nothern hardwood ecosystems at the Huntington Forest (HF) in the Adirondack Mountains of New York and Bear Brook Watershed in Maine (BBWM). Columns were leached for 20 weeks with a simulated throughfall solution with³⁵SO₄ ^2-. Sulfur constituents were similar to those of other Spodosols, with the organic S fractions (C-bonded S and ester sulfate) constituting over 90% of total S. HF soil columns had higher total S (14.9 mol S g^-1) than that for the BBWM soil columns (7.4 mol g^-1) primarily due to higher C-bonded S in the former.Initially, adsorbed SO₄ ^- accounted for 5 and 4% of total S for the BBWM and HF soil columns, respectively. After 20 weeks, adsorbed SO₄ ^2- decreased (81%) in BBWM and increased (33%) in HF soil columns. For both HF and BBWM soil columns, C-bonded S increased and ester sulfate decreased, but only for HF columns was there a net mineralization of organic S (5.6% of total S). The greatest decrease in ester sulfate occurred at the top of the columns.Leaching of³⁵S was less than 0.5% of the³⁵S added due to its retention in various S constituents. There was an exponential decrease in³⁵S with column depth and most of the radioisotope was found in C-bonded S (70–88 and 70–91% for BBWM and HF, respectively). The rapid turnover of adsorbed SO^2- ₄ was reflected in its high specific activity (834 and 26 kBq mol^-1 S for BBWM and HF, respectively). The lower specific activity of adsorbed SO₄ ^2- in HF was attributable to greater isotopic dilution by non-radioactive SO^2- ₄ derived from greater organic S mineralization in the HF versus the BBWM columns.Both soil columns initially had high levels of NO^- ₃ which resulted in the generation of H⁺ and net retention of SO₄ ^2- in the early phase of the experiment due to pH dependent sulfate adsorption; later NO₃ ^- decreased and SO₄ ^2- was desorbed. Leaching of NIO₃ ^- and SO₄ ^2- was correlated with losses of Mg²⁺ and Ca²⁺ of which the latter was the dominant cation.Analyses using both S mass balances and radioisotopes corroborate that for BBWM soil columns, SO^2- ₄ adsorption-desorption dominated the S biogeochemistry while in HF soil columns, organic S mineralization-immobilization processes were more important. It is suggested that similar techniques can be applied to soils in the field to ascertain the relative importances of SO₄ ^2- adsorption processes and organic S dynamics.     

Dynamics of viable nitrifier community and nutrient availability in dry tropical forest habitat as affected by cultivation and soil texture

Seasonal dynamics of N-mineralization and the size of the viable community of nitrifying bacteria were studied for a forest site and an adjoining cropland site. The forest site was dominated by Boswellia serrata and Acacia catechu in the tree layer, and by Nyctanthes arbortristis and Zizyphus glaberrima in the shrub layer. Crop sequence on the cropland site was Oryza sativa/Lens culinaris. The soil type in both the sites was ultisol (USDA). The cropland soil had significantly higher bulk density, and clay content but lower organic C, total N and total P than forest soil. The soil moisture content, numbers of ammonia-and nitrite oxidizing bacteria and N-mineralization rates were highest in the wet season and lowest in the dry season, while the size of mineral N and P pools showed a reverse trend in both sites. The numbers of free-living cells of ammonia-and nitrite oxidizing bacteria were significantly related with each other as well as with the soil moisture content and N-mineralization rates. In N-mineralization, NO ₃ ^– was the dominating form in the forest site during rainy season, while in other seasons in this site and in all the seasons in the cropland site, NH ₄ ⁺ -N was predominant. The N-mineralization rate and the number of viable nitrifying cells were consistently higher for the forest soil compared to the clay-rich cropland soil. The combination of low soil organic matter and high clay content suppressed the number of free-living cells of nitrifying bacteria and N-mineralization rates in the cropland site.     

Chemical Fruit Thinning in Loquat with NAAm:Dosage, Timing, and Wetting Agent Effects

Effects of an increased lead (Pb) content in soil on growth, photosynthesis (P _N) and anatomical parameters of Plantago major L. plants grown under controlled conditions were studied. The total dry weights of plants at 500 and 2000 mg kg^–1 Pb in soil were correspondingly 70% and 54% of those of control plants. A reduced leaf area and changed leaf structure caused a decrease in P _N in the whole plant. The specific leaf weight (SLW) increased as compared with that of control plants. An increasing Pb content in soil caused a larger number of chloroplasts and larger sizes of protoplasts, a decrease in the chlorophyll a+b contents and a larger number of stomata per unit leaf area based both in adaxial and abaxial epidermis, as compared with control plants. However their conductance was from 40% to 50% lower than that in control plants. It was noted that the dimensions of conducting bundles decreased mainly because of the reduced xylem area. The lower functional activity and the changes at different structural levels of the photosynthetic apparatus caused a decrease in the growth rate of plants at a high Pb content in soil.     

Antibacterial,antioxidant and hypoglycaemic effects of Thymus capitatus (L.) Hoffmanns. et Link leaves' fractions

Abstract

The aim of this study was to examine the bioactivity of the methanol fraction (MF) and n-hexane fraction (HF) of Thymus capitatus leaves in relation to their constituents analysed by gas chromatography and gas chromatography-mass spectrometry. The effects of T. capitatus on the growth of pathogenic bacteria associated with respiratory diseases (13 gram-positive and 4 gram-negative) were determined using a microdilution method. The MF was particularly effective on Streptococcus pneumoniae and Moraxella catarrhalis. The antioxidant activity was evaluated by 2,2-diphenyl-1-picrylhydrazyl, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid), ferric-reducing antioxidant power and β-carotene bleaching assays. A strong activity using β-carotene bleaching test was observed with the MF (IC₅₀ of 0.7?μg/mL after 30?min of incubation). In the hypoglycaemic test, a selective α-amylase inhibitory activity was detected with the HF begging the most active (IC₅₀ of 422.5?μg/mL). T. capitatus may represent a source of natural bioactive compounds.     

Changes in microbial activity and composition in a pasture ecosystem exposed to elevated atmospheric carbon dioxide

Elevated atmospheric CO₂ increases aboveground plant growth and productivity. However, carbon dioxide-induced alterations in plant growth are also likely to affect belowground processes, including the composition of soil biota. We investigated the influence of increased atmospheric CO₂on bacterial numbers and activity, and on soil microbial community composition in a pasture ecosystem under Free-Air Carbon Dioxide Enrichment (FACE). Composition of the soil microbial communities, in rhizosphere and bulk soil, under two atmospheric CO₂ levels was evaluated by using phospholipid fatty acid analysis (PLFA), and total and respiring bacteria counts were determined by epifluorescence microscopy. While populations increased with elevated atmospheric CO₂ in bulk soil of white clover (Trifolium repens L.), a higher atmospheric CO₂ concentration did not affect total or metabolically active bacteria in bulk soil of perennial ryegrass (Lolium perenne L.). There was no effect of atmospheric CO₂ on total bacteria populations per gram of rhizosphere soil. The combined effect of elevated CO₂ on total root length of each species and the bacterial population in these rhizospheres, however, resulted in an 85% increase in total rhizosphere bacteria and a 170% increase in respiring rhizosphere bacteria for the two plant species, when assessed on a per unit land area basis. Differences in microbial community composition between rhizosphere and bulk soil were evident in samples from white clover, and these communities changed in response to CO₂ enrichment. Results of this study indicate that changes in soil microbial activity, numbers, and community composition are likely to occur under elevated atmospheric CO₂, but the extent of those changes depend on plant species and the distance that microbes are from the immediate vicinity of the plant root surface.     

Seasonal fluctuations in the population of denitrifying and N2-fixing bacteria in an acid soil of a Norway spruce forest

The seasonal fluctuations in the concentration of cultured denitrifying and N₂-fixing bacteria were followed in an ammonium fertilised and a control soil of a Norway spruce forest near Villingen/Black Forest from December 1994 to August 1998. The horizontal distribution of bacteria in three layers was determined by the MPN-method and by molecular probing (colony hybridisation) using specific 0.4–0.7 kb DNA probes for denitrification steps (narG, nirS, nirK and nosZ) and for N₂-fixation (nifH). The data showed that highest bacterial counts and higher numbers of denitrifying and N₂-fixing bacteria were generally detectable in the upper (= 5 cm) soil layer and that their amount decreased with soil depth. The concentration of these cultured bacteria showed seasonal fluctuations with highest numbers in autumn/winter/early spring and with low counts in summer. Denitrifying and N₂-fixing bacteria amounted to less than 10% of the total number of cultured bacteria determined by the MPN-method. Fertilisation with ammonium did not cause a shift in the population of these bacteria. These findings were corroborated by hybridisation experiments with genomic DNA isolated from the different layers. Strongest DNA–DNA hybridisation band intensities were obtained in the upper soil layer and their intensities decreased with soil depth. Soil samples from Villingen assayed in the laboratory produced N₂O (in dependence of nitrate and C₂H₂ added to the vessels) and utilised this gas with higher activities in the assays with the fertilised soil. It is concluded that molecular techniques can successfully be applied for assessing seasonal fluctuations of bacterial populations in soil. Relative abundance of denitrifying and N₂-fixing bacteria can be determined from experiments with DNA isolated from soils. Attempts to transform these results to the total population of soil bacteria on a single cell basis are faced with many uncertainties.     

Land Consolidation with Seedling Cultivation Could Decrease Soil Microbial PLFA Diversity

The impact of land consolidation on the soil microbial PLFA diversity is of great importance for understanding the effective arable land usage, improving agricultural ecological conditions and environment. In this study, we collected the soil samples (0–20 cm) in experimental plots with 0 (Z₀), 1 (Z_1a) and 4 (Z_4a) years of land consolidation in the forest station of Ningbo City, Zhejiang Province, southeastern China. The results were analyzed using ANOVA for randomized block design. Compared with control (Z₀), the soil pH value under Z_1a treatment increased by 14.6%, soil organic carbon (SOC) content decreased by 65.4%, so did the PLFA contents and relative abundance of all the microbial PLFA diversity (P < 0.05), respectively. Meanwhile, for the Z_1a treatment, the ratio of fungi to bacteria (F/B) significantly decreased by 35.9% (P < 0.05), while the ratio of Gram-positive bacteria to Gram-negative bacteria (G+/G−) signific antly increased by 56.1%. This was strongly related to the increased soil pH values and the decrease of SOC. The Shannon index (H) and evenness index (E) of soil microbial PLFA diversity were significantly decreased after land consolidation (P < 0.05). Compared to the Z₁ treatment, the microbial PLFA diversity was improved slightly. Therefore, the land consolidation could significantly affect the composition of soil microbial PLFA diversity, and decrease the soil ecosystem stability.     

火烧强度对中亚热带人工造林初期土壤呼吸的影响

在热带和亚热带森林中,火烧是一种清理采伐迹地的有效管理措施。尽管许多研究表明,火烧刺激了土壤的碳排放,但对亚热带火强度对土壤呼吸的影响还缺乏了解。在中亚热带米槠常绿阔叶次生林采伐迹地上,设置高火烧强度（HF）、低火烧强度（LF）炼山造林处理,利用LI-8100对造林初期（2012年3月-2012年12月）土壤呼吸进行测定,同时监测观测期土壤温度、含水量以及降雨量等气象因子,分析不同火烧强度对中亚热带造林初期土壤呼吸及排放量的影响,同时探讨影响土壤呼吸变化的主要因素。结果表明：（1）观测期间不同火烧强度对土壤呼吸的影响呈现出明显的时间变化特征：与对照（CT）相比,土壤呼吸在火烧后2个月以内显著增加（P<0.05）,HF和LF分别增加76.3%和55.3%;在火烧后2-5个月内三种处理间没有显著差异（P>0.05）;但之后,火烧处理土壤呼吸显著低于CT （P<0.05）,HF和LF分别降低40%和32.6%;在观测期间火烧处理没有导致土壤CO₂累计排放量的增加。（2）火烧处理下,仅HF处理中土壤呼吸与土壤温度显著相关（P<0.05）,但拟合决定系数较低。（3）单次降水事件会导致火烧处理下土壤呼吸的增加,而对照无明显增加;但连续性降水事件中,降雨早期促进土壤呼吸,而后期呈现出抑制作用。     

Chronological approach of diet-induced alterations in muscle mitochondrial functions in rats

Objective: Mitochondrial dysfunction might predispose individuals to develop insulin resistance. Our objective was to determine whether mitochondrial dysfunction or insulin resistance was the primary event during high‐fat (HF) diet. Research Methods and Procedures: Rats were fed an HF diet for 0, 3, 6, 9, 14, 20, or 40 days and compared with control. Soleus and tibialis muscle mitochondrial activity were assessed using permeabilized fiber technique. Insulin [area under the curve for insulin (AUC_I)] and glucose [area under the curve for glucose (AUC_G)] responses to intraperitoneal glucose tolerance test as well as fasting plasma non‐esterified fatty acids (NEFAs), triglyceride, and glycerol concentrations were determined. Results: AUC_I and AUC_G were altered from Day 6 (p < 0.01 vs. Day 0). In soleus, oxidative phosphorylation (OXPHOS) activity was transiently enhanced by 26% after 14 days of HF diet (p < 0.05 vs. Day 0) conjointly with 62% increase in NEFA concentration (p < 0.05 vs. Day 0). This was associated with normalized AUC_G at Day 14 and with a decline of plasma NEFA concentration together with stabilization of intra‐abdominal adiposity at Day 20. Prolongation of HF diet again caused an increase in plasma NEFA concentration, intra‐abdominal adiposity, AUC_I, and AUC_G. At Day 40, significant decrease in OXPHOS activity was observed in soleus. Discussion: Mitochondria first adapt to overfeeding in oxidative muscle limiting excess fat deposition. This potentially contributes to maintain glucose homeostasis. Persistent overfeeding causes insulin resistance and results in a slow decline in oxidative muscle OXPHOS activity. This shows that the involvement of mitochondria in the predisposition to insulin resistance is mainly due to an inability to face prolonged excess fat delivery.     

BIOLOGICAL NITROGEN INFLUX IN AN OHIO RELICT PRAIRIE

The principal contributors of biologically fixed N in natural grassland ecosystems appear to be asymbiotic bacteria and heterocystous cyanobacteria. The environmental factors of light, moisture, and temperature play important roles in the magnitude of the N₂-fixation activity. Biological N₂-fixation was measured in the Elizabeth's Prairie section of the Lynx Prairie Preserve, Adams County, Ohio, during 15 site visits beginning 29 March through 8 November 1980. In situ N₂-fixation activity was measured using the acetylene-reduction technique. The percentage cover of cyanobacterial colonies (Nostoc sp.) was determined using Point-Frame Analysis. Soil and air temperatures and soil water potentials also were measured. Intact soil cores with a surface cover of Nostoc were collected and returned to the laboratory to quantify the effect of decreasing water potential on the N₂(C₂H₂)ase activity of Nostoc. The N₂(C₂H₂)ase activity of Nostoc on the intact soil cores displayed a linear response of approximately 10% decrease in N₂(C₂H₂)ase activity per one bar decrease in soil water potential. The cyanobacteria contributed almost all of the biologically fixed N at the site until late June. From late June through to mid September, heterotrophic diazotrophs played the major role in the N₂-fixation activity. These changes are attributed to fluctuations in Nostoc sp. colony cover, temperature, and soil water potentials. Extrapolation of the measured rates, and assuming an average of 10 hr per day of activity, Nostoc sp. is shown to have contributed 4.60 ± 1.17 kg N ha⁻¹ yr⁻¹. Heterotrophic diazotrophs contributed an estimated 3.19 ± 1.18 kg N ha⁻¹ yr⁻¹. The total biological N₂-fixation for the site was calculated at 8.2 ± 2.55 kg N ha⁻¹ yr⁻¹, from additional measurements which estimated total diazotrophic activity of the site. These rates of N₂-fixation are among the highest reported for temperate grassland habitats.     

Role of hydrogen generation by <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> in the oral cavity

Some gastrointestinal bacteria synthesize hydrogen (H₂) by fermentation. Despite the presence of bactericidal factors in human saliva, a large number of bacteria also live in the oral cavity. It has never been shown that oral bacteria also produce H₂ or what role H₂ might play in the oral cavity. It was found that a significant amount of H₂ is synthesized in the oral cavity of healthy human subjects, and that its generation is enhanced by the presence of glucose but inhibited by either teeth brushing or sterilization with povidone iodine. These observations suggest the presence of H₂-generating bacteria in the oral cavity. The screening of commensal bacteria in the oral cavity revealed that a variety of anaerobic bacteria generate H₂. Among them, Klebsiella pneumoniae (K. pneumoniae) generated significantly large amounts of H₂ in the presence of glucose. Biochemical analysis revealed that various proteins in K. pneumoniae are carbonylated under standard culture conditions, and that oxidative stress induced by the presence of Fe⁺⁺ and H₂O₂ increases the number of carbonylated proteins, particularly when their hydrogenase activity is inhibited by KCN. Inhibition of H₂ generation markedly suppresses the growth of K. pneumoniae. These observations suggest that H₂ generation and/or the reduction of oxidative stress is important for the survival and growth of K. pneumoniae in the oral cavity.     

Can biochar reduce soil greenhouse gas emissions from a Miscanthus bioenergy crop?

Energy production from bioenergy crops may significantly reduce greenhouse gas (GHG) emissions through substitution of fossil fuels. Biochar amendment to soil may further decrease the net climate forcing of bioenergy crop production, however, this has not yet been assessed under field conditions. Significant suppression of soil nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions following biochar amendment has been demonstrated in short‐term laboratory incubations by a number of authors, yet evidence from long‐term field trials has been contradictory. This study investigated whether biochar amendment could suppress soil GHG emissions under field and controlled conditions in a Miscanthus × Giganteus crop and whether suppression would be sustained during the first 2 years following amendment. In the field, biochar amendment suppressed soil CO₂ emissions by 33% and annual net soil CO₂ equivalent (eq.) emissions (CO₂, N₂O and methane, CH₄) by 37% over 2 years. In the laboratory, under controlled temperature and equalised gravimetric water content, biochar amendment suppressed soil CO₂ emissions by 53% and net soil CO₂ eq. emissions by 55%. Soil N₂O emissions were not significantly suppressed with biochar amendment, although they were generally low. Soil CH₄ fluxes were below minimum detectable limits in both experiments. These findings demonstrate that biochar amendment has the potential to suppress net soil CO₂ eq. emissions in bioenergy crop systems for up to 2 years after addition, primarily through reduced CO₂ emissions. Suppression of soil CO₂ emissions may be due to a combined effect of reduced enzymatic activity, the increased carbon‐use efficiency from the co‐location of soil microbes, soil organic matter and nutrients and the precipitation of CO₂ onto the biochar surface. We conclude that hardwood biochar has the potential to improve the GHG balance of bioenergy crops through reductions in net soil CO₂ eq. emissions.     

Distribution pattern of rare earth elements in fern

All the lanthanide elements (REE) in fern (Matteuccia) and in soil were determined with inductively coupled plasma mass spectrometer (ICP-MS) in order to discuss REE behavior in fern. The fern sample was divided into three parts: root, stem, and leaf; the soil of the same site was also sampled and the soil sample was divided into two parts: HCl and HNO₃ soluble part (soil[HCl]) and HF soluble part (soil[HF]). REE in each part was determined by ICP-MS after solvent extraction separation. The overall variation of the REE pattern of the root does not resemble that of the whole soil, but that of the HF soluble part. A tetrad effect variation (W-type) was found in the REE patterns of root, stem and leaf; more conspicuous tetrad effect variation was observed in HREE region than in LREE region, and was so in stem and leaf than in root. Negative anomalies of Ce were observed in the REE patterns of root, stem and leaf, with bigger anomalies in stem and leaf than in root. The results of this study suggest that REE in fern has come from silicates of soil and has once been in dissolved state.