Antifungal clerodane diterpenes from Macaranga monandra (L) Muell. et Arg. (Euphorbiaceae)

Hexane and ethyl acetate phases of the methanol extract of Macaranga monandra showed fungal growth inhibition of Colletotrichum acutatum, C. fragariae and C. gloeosporioides, Fusarium oxysporum, Botrytis cinerea, Phomopsis obscurans, and P. viticola. Bioassay-guided fractionation led to the isolation of two active clerodane-type diterpenes that were elucidated by spectroscopic methods (1D-, 2D-NMR, and MS) as kolavenic acid and 2-oxo-kolavenic acid. A 96-well microbioassay revealed that kolavenic acid and 2-oxo-kolavenic acid produced moderate growth inhibition in Phomopsis viticola and Botrytis cinerea.     

坡改梯的水土保持效益研究

主要研究了坡耕地、新梯田、老梯田的各种水土保持指标,对比分析坡改梯后的水土保持效果。研究结果表明,坡改梯后土壤水分、土壤贮水量、地表径流量、入渗性能、土壤物理性状等指标都得到明显的改善。     

Aluminium and uptake of base cations by tree roots: A critique of the model proposed by Sverdrup et al.

Sverdrupet al. (1992) proposed a model intended to evaluate effects of soil solution (Ca²⁺+Mg²⁺/Al³⁺ ratios on the uptake of Ca²⁺ and Mg²⁺ (here called base cations=BC) by tree roots. They considered the adsorption of BC on exchange sites on root surfaces to be a major step, and the competition between Al³⁺ and BC for exchange sites on roots to be crucial. Although this may certainly affect the rates of uptake, it will not exclude base cations from entering the root cells through ion channels or by carriers. Above all, the model overlooks important gradients in the rhizosphere, e.g. pH-gradients and root exudates, which have profound influences on the speciation of Al. One should instead consider modifying existing models accounting for processes in a buffered soil medium and handling gradients in the rhizosphere (e.g. Nye and Tinker, 1977). This would also require considerations on mycorrhizas and possible changes in the capacity for uptake of certain ions, which could be induced by deficiencies.     

Modelling decomposition of standard plant material along an altitudinal gradient: A re-analysis of data of Coûteaux et al. (2002)

We explored an alternative method to analyse data of Coûteaux et al. [2002, Soil Biology and Biochemistry 34, 69-78] on the decomposition of a standard organic material in six soils along an altitudinal gradient in the Venezuelan Andes (65-3968 m a.s.l.). Coûteaux et al., fitted separate two-component decomposition models to data of the individual sites, allowing the initial size of the labile and the resistant component to differ between sites. This procedure led them to conclude that the initial size of the resistant component and its decomposition rate depend on temperature while decomposition rate of the labile component does not, which seems biologically unlikely and at variance with literature. As an alternative we fitted a single two-component model to the whole data set, using identical initial component sizes for all sites. We found no statistical ground for using variable initial component sizes. It appeared that the data does not allow a conclusion on the effect of temperature on the decomposition of the labile component. We also investigated alternatives for the values of Q₁₀ and T_opt that were used by Coûteaux et al., and found that temperature explains a larger part of the differences in decomposition rate among sites when using a Q₁₀ value of 3.75 instead of 2.2 and a T_opt value of 27 °C instead of 25 °C. We discuss the arguments used in model selection and the consequences for predictions of long-term accumulation of soil carbon. Our analysis suggests an even stronger positive feedback between global warming and soil carbon emission than the analysis by Coûteaux et al.     

Response to the Views and Opinions of Maningat,Seib, and Bassi Regarding McCleary et al (2013)

Phosphate cross‐linked starch, referred to as resistant starch 4 (RS₄) is hydrolyzed much more rapidly under physiological conditions (i.e., pH 6, 37°C, pancreatic α‐amylase) than under the conditions used in AOAC dietary fiber method 985.29/AACC International Approved Method 32‐45.01 (the Prosky method), in which samples are incubated with thermostable bacterial α‐amylase at 95–100°C. For this reason, the author concludes that the Prosky method overestimates the dietary fiber content of these materials. A more accurate estimate of dietary fiber content is obtained with AOAC Method 2009.01/AACCI Approved Method 32‐45.01.     

Comment on the comment by Amthor et al. on “Appropriate experimental ecosystem warming methods” by Aronson and McNulty

In a recent comment on the paper by Aronson and McNulty (2009) about “Appropriate experimental ecosystem warming methods by ecosystem, objective, and practicality”, Amthor et al. (2010) state that infrared lamps do not warm open-field plots by the mechanism expected with global warming. While this statement is correct, in the aftermath of their comment, confusion exists about how warming with infrared heaters can be related to global warming. This comment illustrates how infrared heating at “constant temperature rise” relates in a quantitative way to anticipated global warming. Amthor et al. (2010) also state that changes in vapor pressure gradient from leaf to atmosphere are an issue with infrared heating, but this problem can be minimized with supplemental irrigations in controlled amounts. Therefore, “constant temperature rise” infrared warming experiments with supplemental irrigations are a viable T-FACE (temperature free-air controlled enhancement) that can be used in combination with CO₂-FACE to produce conditions more representative of future open-fields than can be done with chambers with their many known artifacts.