Celtis tala and Scutia buxifolia leaf litter decomposition by selected fungi in relation to their physical and chemical properties and lignocellulolytic enzyme activity

This study analyzes the relationships between the physical and chemical properties of Celtis tala and Scutia buxifolia leaf litter and their degradation by selected fungi. The litter was analyzed for physical, chemical and enzyme properties such as pH, reducing sugars, aromatic compounds, chromophores, polymerization/polydispersity index and the lignocellulolytic enzyme activity of their water soluble fraction (WSF) after incubating them with fungi for 30 days. C. tala and S. buxifolia leaves were chemically different, with C-to-N ratios of 27 and 17, respectively. Fungi degraded C. tala leaves to a greater extent than those of S. buxifolia, which was directly related to the pH of the WSF. In this regard, properties other than microbial growth affecting substrate N concentration, such as lignin content or lignin-to-N ratio and the availability of nutrients for regulating the expression and activity of depolymerizing enzymes, governed the decomposition. Whereas degradation of S. buxifolia leaves by a group of selected fungi was related to cellobiohydrolase and β-1,4-endoglucanase activities, that of C. tala was related to the β-glucosidase activity. However, the fungi studied showed negligible ligninolytic potential. Still, physical and chemical properties such as pH and reducing sugars or chromophores as well as cellulose-degrading fungal enzymes were reliable indices of decomposition of the C. tala and S. buxifolia leaf litter.     

Five new fawcettimine-related alkaloids from Lycopodium japonicum Thunb

Five new trace alkaloids with fawcettimine-related structures (1–5), i.e., 6-hydroxyl-6,7-dehydrolycoflexine (1), 6-hydroxyl-6,7-dehydro-8-deoxy-13-dehydroserratinine (2), together with three known ones (6–8), were isolated from the club moss Lycopodium japonicum Thunb. Their structures were elucidated by extensive NMR spectroscopic analysis, HRESIMS, CD and comparison with known ones. Compounds 1 and 2 are characterized by the enol moiety that is rarely reported in Lycopodium alkaloids, and Compound 5 is the second example of Lycopodium alkaloids with a C-16–C-4 linkage. A plausible biogenetic pathway for the isolates was proposed.     

Temporal dynamics of microbial communities on decomposing leaf litter of 10 plant species in relation to decomposition rate

Few empirical studies have examined how microbial communities on decomposing litters change in relation to litter chemistry or how microbial community composition is related to the rate of decomposition. We examined the relationships among microbial community composition, litter chemistry, and decomposition rates in a common garden experiment of the decomposition of leaf litters of 10 plant species. Microbial community composition, as measured by phospholipid fatty acids (PLFA), and 7 litter chemistry variables (%N, C:N, four carbon fractions, and lignin:N) were examined at 1, 2, and 8 months into decomposition. Both microbial and litter chemistry variables were reduced to a single axis each through nonmetric multidimensional scaling (NMS) to examine the relationship between microbes, litter chemistry, and decomposition rates. Although microbial communities were separated according initial litter chemistry and lability, individual measures of litter chemistry had limited ability to predict microbial community composition during decomposition. Decomposition rate constants were explained by litter chemistry of initial, 1-, 2- and, 8-month old litters (60–72% of the variance), and by microbial community composition at the 8-month collection date (67%). The results suggest that initial litter chemistry determines the rate of decomposition and microbial community composition early in decomposition while the composition of the microbial community plays a more important role in determining decomposition rate later in decomposition.     

岷江上游径流枯水年时间序列的分形研究

分形是研究复杂自然现象的有力工具之一.本文在分形概念基础上介绍了分形在水文时间序列中的应用。利用多年径流的丰枯时间序列的分形特征,根据岷江上游多年径流丰枯变化的实测资料,对多年径流的丰枯变化长期趋势进行了预测分析,并给出了预测未来短期枯水/丰水年出现年份的方法。结果表明,利用R/S方法预测丰枯变化趋势预测是一条较为有效的途径。     

Quality of soluble organic C,N, and P produced by different types and species of litter: Root litter versus leaf litter

In forested ecosystems, the quality of dissolved organic matter (DOM) produced by freshly senesced litter may differ by litter type and species, and these differences may influence the amount of DOM that is respired versus that which may either contribute to soil organic matter accumulation or be leached from the ecosystem. In this study, we investigated the effect of litter type (including freshly senesced fine root, leaf, fine woody, and reproductive litter) and species (5 species of leaf litter) on several measures of the quality of DOM produced at a site along a primary successional chronosequence at Mt. Shasta, California. We measured differences in solid litter chemistry (C, N, and P concentration) and differences in the concentration of dissolved organic C, N, and P (DOC, DON, and DOP, respectively), water-soluble monomeric carbohydrates, polyphenols, proteins, fractions of DOC, as well as UV absorbance. For several aspects of DOC quality, DOM from fine roots was less labile than DOM from leaf litter. In contrast to DOC quality, soluble material originating from fine roots was high in labile forms of dissolved N and P in comparison to leaf litter. We also found that leaf litter with greater total %N or %P in solid litter had higher DON or DOP concentration (and higher total soluble P concentration). A very high percentage, on average 72% (up to 89%) of the total P in leaf litter was water-soluble and mostly inorganic P. Concentrations of soluble polyphenols were strongly related to DOC, and concentrations of soluble proteins were significantly related to DON in leaf litter of different species. During primary succession at the Mt. Shasta site, an increasing ratio of root to leaf litter production and shifting species composition has been found to occur, and the results of this study suggest that some aspects of DOC quality reflect a decrease in labile forms of DOC originating from both above and belowground litter. In contrast, dissolved N and P reflect an increase in labile forms with increasing inputs of root litter. In particular, our study has demonstrated important differences in the quality of inputs of DOM from freshly senesced root and leaf litter, and these differences have implications for C and nutrient cycling.     

Dynamics of methanogenesis and methanotrophy in tropical paddy soils as influenced by elevated CO2 and temperature interaction

Response of methanogenesis and methanotrophy to elevated carbon dioxide (CO₂) could be affected by changes in soil moisture content and temperature. In soil microcosms contained in glass bottles and incubated under laboratory conditions, we assessed the impact of elevated CO₂ and temperature interactions on methanogenesis and methanotrophy in alluvial and laterite paddy soils of tropical origin. Soil samples were incubated at ambient (370 μmol mol⁻¹) and elevated (600 μmol mol⁻¹) CO₂ concentrations at 25, 35 and 45 °C under non-flooded and flooded conditions for 60 d. Under flooded condition, elevated CO₂ significantly increased methane (CH₄) production while under non-flooded condition, only marginal increase in CH₄ production was observed in both the soils studied and the increase was significantly enhanced by further rise in temperature. Increased methanogenesis as a result of elevated CO₂ and temperature interaction was mostly attributed to decreased soil redox potential, increased readily mineralizable carbon, and also noticeable stimulation of methanogenic bacterial population. In contrast to CH₄ production, CH₄ oxidation was consistently low under elevated CO₂ concentration and the decrease was significant with rise in temperature. The low affinity and high affinity CH₄ oxidation were faster under non-flooded condition as compared to flooded condition. Admittedly, decreased low and high affinity CH₄ oxidation as a result of elevated CO₂ and temperature interaction was related to unfavorable lower redox status of soil and the inhibition of CH₄-oxidizing bacterial population.     

3, 4-seco-Labdane diterpenoids from the leaves of Callicarpa nudiflora and their inhibitory effects on nitric oxide production

As a part of our ongoing search for bioactive compounds from the leaves of Callicarpa nudiflora that inhibit nitric oxide (NO) production, the 90% EtOH fraction eluted by macroporous resin adsorption was found to show significant inhibitory activity against the production of NO in RAW 264.7 stimulated by lipopolysaccharide (LPS). Bioactivity-guided isolation of the fraction yielded three new bioactive diterpenoids, named ent-3, 4-seco-14-carbonyl-15, 16-epoxy-4(18), 8(17), 13(14)-labdatrien-3-oic acid (1), syn-3, 4-seco-12R-hydroxy-15, 16-epoxy-4(18), 8(17), 13(16), 14(15)-labdatetraen-3-oic acid (2) and syn-3, 4-seco-12S-hydroxy-15, 16-epoxy-4(18), 8(17), 13(16), 14(15)-labdatetraen-3-oic acid (3). Their structures and configurations were elucidated by comprehensive spectroscopic analysis. All the three compounds exhibited potent inhibitory activity on NO production in LPS-activated RAW 264.7 macrophage cells.     

基于世界遗产监测经验的全球重要农业文化遗产监测体系构建

为了保护具有全球重要性的传统农业系统,联合国粮农组织于2002年发起全球重要农业文化遗产(GIAHS)保护倡议。经过十几年的发展,中国目前拥有的GIAHS数量最多,但也面临着GIAHS科学保护与有效管理的艰巨任务。作为遗产管理的重要内容,监测对提升遗产管理水平具有重要作用。科学有效的遗产监测不仅可以实现遗产自身的保护及其价值的维护,而且可以实现遗产地的可持续发展。然而,我国的GIAHS监测工作刚刚起步,尚未建立一套科学完善的GIAHS监测体系,也缺乏相关理论研究作为支撑。为此,本文在充分借鉴世界遗产监测经验与实践的基础上,对GIAHS监测概念与内涵、监测范围与内容、数据收集与管理等关键问题进行了详细阐述,并提出由三级监测网络、动态监测系统和两级巡视制度构成的GIAHS监测体系。动态监测系统是GIAHS监测体系的核心组成,包括监测范围、监测内容、监测方法、数据管理的多个方面。三级监测网络和两级巡视制度是GIAHS监测体系的基础保障,不仅有助于形成主动监测与监督巡视相结合的监测巡视机制,而且将监测数据汇交与评估意见反馈形成闭合回路,从而提高GIAHS保护与管理工作的科学性与系统性。研究结果不仅有助于丰富GIAHS监测理论,进一步推动中国的GIAHS监测工作,也能为国际GIAHS监测提供中国经验。     

Chemical Synthesis and Structure-Activity Relationship Study Yield Desotamide a Analogues with Improved Antibacterial Activity

Desotamides A, a cyclohexapeptide produced by the deep-sea-derived Streptomyces scopuliridis SCSIO ZJ46, displays notable antibacterial activities against strains of Streptococcus pnuemoniae, Staphylococcus aureus, and methicillin-resistant Staphylococcus epidermidis (MRSE). In this study, to further explore its antibacterial potential and reveal the antibacterial structure-activity relationship of desotamides, 13 cyclopeptides including 10 new synthetic desotamide A analogues and wollamides B/B1/B2 were synthesized and evaluated for their antibacterial activities against a panel of Gram-positive and -negative pathogens. The bioactivity data reveal that residues at position II and VI greatly impact antibacterial activity. The most potent antibacterial analogues are desotamide A4 (13) and A6 (15) where l-allo-Ile at position II was substituted with l-Ile and Gly at position VI was simultaneously replaced by d-Lys or d-Arg; desotamides A4 (13) and A6 (15) showed a 2–4-fold increase of antibacterial activities against a series of Gram-positive pathogens including the prevalent clinical drug-resistant pathogen methicillin-resistant Staphylococcus aureus (MRSA) with MIC values of 8–32 μg/mL compared to the original desotamide A. The enhanced antibacterial activity, broad antibacterial spectrum of desotamides A4 and A6 highlighted their potential as new antibiotic leads for further development.     

Organic nitrogen mineralisation in two contrasting agro-ecosystems is unchanged by biochar addition

Biochar additions to soil have been reported to enhance soil fertility whilst simultaneously storing carbon (C). We tested whether either fresh or field-conditioned (aged) biochar amendment to two contrasting agricultural soils would alter the mineralisation of organic N compounds. The mineralisation of ¹⁴C-labelled amino acids and peptides were determined over 20 days within each soil. An exponential kinetic decay model was subsequently fitted to the mineralisation data. Overall, statistical analysis revealed significant but small differences between the two biochar treatments and the unamended control treatment. We conclude that biochar has very limited impact on the mineralisation rate of low molecular weight dissolved organic N compounds in these agro-ecosystems.