真菌腐朽及潮湿环境对定向刨花板力学性能的影响

探讨和分析了室外用定向刨花板(OSB)在真菌腐朽及潮湿条件下力学性能的变化规律。植菌试件在25～30℃、相对湿度90％条件下放置20周后,测试结果表明,两种褐腐菌Gloeophyllum trabeum(G、T．)、Postia placenta(P．P．)和一种白腐菌Trametes versitcolor(T．V．)都以较小的质量损失对静曲强度(MOR)和弹性模量(MOE)造成严重破坏,其中,G．T．和T．V．在板材表面生长较旺盛,造成的强度损失程度类似,且部大于P．P．。但P．P．腐朽导致的单位质量损失具有最大破坏力。未种植真菌的试件处于温湿状态下同样产生显著的强度下降,表明室外用人造板材料除防腐处理外,还应注意采取防潮湿保护措施。     

不同SO2保鲜剂对先锋甜樱桃采后保鲜效果的研究

以采后先锋甜樱桃果实为试材,研究不同SO2保鲜剂(1/2或1/4张SO2速释保鲜纸,6包SO2缓释保鲜片,1/4张SO2速释保鲜纸+3包缓释保鲜片)的保鲜效果。结果表明,在0℃结合MAP包装(装量5 kg)条件下,采用1/4张SO2速释保鲜纸+3包缓释保鲜剂处理的先锋甜樱桃贮藏60 d,果实色泽良好,果梗鲜绿,药害轻微,腐烂率显著低于对照(P<0.05),好果率可达90%以上。     

Effect of Different Temperature and Anaerobic/Aerobic Conditions on the Decay Characteristics of PAOs

In order to analyze the effect of different temperatures on PAOs decay, a lab scale EBPR culture with PAOs over 90%±2% of the entire bacterial was used under different conditions (10℃ anaerobic, 10℃ aerobic, 20℃ anaerobic, 20℃ aerobic). The results show that the decay rate increases with the increase of temperature; the average rate during 1~9 days is (respectively: 10℃ anaerobic, 10℃ aerobic, 20℃ anaerobic, 20℃ aerobic) 0.053/d, 0.50/d, 0.072/d, and 0.145/d; the cell death rate is 0.019/d, 0.017/d, 0.019/d, and 0.03/d, which accounts for 35.8%, 34%, 26.4%, and 20.7% of the decay rate, respectively. The concentration of PHA and glycogen decreases during the decay period. And Glycogen degrades quickly in anaerobic conditions than in aerobic conditions under the same temperature. The glycogen degrade rate is higher with the increase of temperature under the same anaerobic and aerobic conditions.     

利用变性梯度凝胶电泳分析正红菇菌根围土壤真菌群落多样性

以正红菇（Russula griseocarnosa）菌根围土壤为研究对象,通过提取土壤基因组DNA,以通用引物扩增真菌18S rRNA基因V1+V2区,将PCR产物进行变性梯度凝胶电泳（Denaturing Gradient Gel Electrophoresis）,获得土壤微生物群落的DNA特征指纹图谱,并对图谱中的优势条带回收测序,通过Blast进行同源性比对并构建系统发育树,进而分析正红菇菌根围真菌群落组成及多样性。同源性比对结果表明,在回收测序的19条DGGE条带中,4条为非真菌真核生物序列,系统发育分析显示全部序列可以分为4类菌群,GroupⅠ主要为担子菌门（Basidiomycota）真菌,GroupⅡ主要为子囊菌门（Ascomycota）真菌,GroupⅢ为未知真菌,GroupⅣ主要为节肢动物门生物（Arthropoda）。     

Decomposition Dynamics and Nutrient Release Pattern from Leaf Litters of Five Commonly Occurring Homegarden Tree Species in Mizoram,India

Leaf litter decomposition and nutrient release patterns from five common multipurpose tree species—viz., Artocarpus heterophyllus, Mangifera indica, Areca catechu, Citrus sp., and Tamarindus indica, found in homegardens of Mizoram—were evaluated using a litter bag technique. The result of the study indicates a varying pattern of decomposition and nutrient release (N&P) among the species. Citrus sp. and T. indica were found to be the most labile species with comparatively much higher decay constant and faster nutrient release. Initial nitrogen concentration, lignin content, and lignin/N ratio of foliage litter showed significantly higher (p < .01) correlation with the decay coefficient and were found to be the important determinants in the decay process. The initial slow release and immobilization of N in A. heterophyllus and M. indica leaf litter reflect their potential as a source of nitrogen storage and effective mulching material. While litter from T. indica and Citrus sp. can provide the short-term nutrient need, foliage for the other three species may supply the long-term nutrient requirement for the understory crops in such agroforestry systems.     

Chemical modification of wood: A short review

Abstract

For most markets for wood, it is used without any treatments or modifications. When wood is used in adverse environments, it may be treated with chemicals to help prevent decay, improve water resistance, reduce the effects of ultraviolet radiation or increase fire retardancy. Many of these treatments involve the use of toxic or corrosive chemicals that can harm the environment. Chemical modification of wood provides an alternative by providing protection against water, decay, UV and thermal degradations by bonding chemicals to the cell wall polymers that do not leach out. Dimensional stability and decay resistance are two major properties that can be greatly improved by simple reactions with acetic anhydride.     

Effect of fungal exposure on the strength of thermally modified Norway spruce and Scots pine

Abstract

Thermal modification at elevated temperatures changes the chemical, biological and physical properties of wood. In this study, the effects of the level of thermal modification and the decay exposure (natural durability against soft-rot microfungi) on the modulus of elasticity (MOE) and modulus of rupture (MOR) of the sapwood and heartwood of Scots pine and Norway spruce were investigated with a static bending test using a central loading method in accordance with EN 408 (1995). The results were compared with four reference wood species: Siberian larch, bangkirai, merbau and western red cedar. In general, both the thermal modification and the decay exposure decreased the strength properties. On average, the higher the thermal modification temperature, the more MOE and MOR decreased with unexposed samples and increased with decayed samples, compared with the unmodified reference samples. The strength of bangkirai was least reduced in the group of the reference wood species. On average, untreated wood material will be stronger than thermally modified wood material until wood is exposed to decaying fungi. Thermal modification at high temperatures over 210°C very effectively prevents wood from decay; however, strength properties are then affected by thermal modification itself.     

Decay resistance of sapwood and heartwood of untreated and thermally modified Scots pine and Norway spruce compared with some other wood species

Abstract

Thermal modification has been developed for an industrial method to increase the biological durability and dimensional stability of wood. In this study the effects of thermal modification on resistance against soft- and brown-rot fungi of sapwood and heartwood of Scots pine and Norway spruce were investigated using laboratory test methods. Natural durability against soft-rot microfungi was determined according to CEN/TS 15083-2 (2005) by measuring the mass loss and modulus of elasticity (MOE) loss after an incubation period of 32 weeks. An agar block test was used to determine the resistance to two brown-rot fungi using two exposure periods. In particular, the effect of the temperature of the thermal modification was studied, and the results were compared with results from untreated pine and spruce samples. The decay resistance of reference untreated wood species (Siberian larch, bangkirai, merbau and western red cedar) was also studied in the soft-rot test. On average, the soft-rot and brown-rot tests gave quite similar results. In general, the untreated heartwood of pine was more resistant to decay than the sapwood of pine and the sapwood and heartwood of spruce. Thermal modification increased the biological durability of all samples. The effect of thermal modification seemed to be most effective within pine heartwood. However, very high thermal modification temperature over 230°C was needed to reach resistance against decay comparable with the durability classes of “durable” or “very durable” in the soft-rot test. The brown-rot test gave slightly better durability classes than the soft-rot test. The most durable untreated wood species was merbau, the durability of which could be evaluated as equal to the durability class “moderately durable”.     

Durability of thermally modified Norway spruce and Scots pine in above-ground conditions

Abstract

One of the main objectives of thermal modification is to increase the biological durability of wood. In this study the fungal resistance of Norway spruce and Scots pine, thermally modified at 195°C and 210°C, was studied with a lap-joint field test. Untreated pine and spruce and pine impregnated with tributyl tin oxide (TBTO) and copper, chromium and arsenic (CCA) were selected as reference materials. The evaluations were carried out after 1, 2 and 9 years of exposure. After 1 and 2 years of exposure mainly discoloration was detected. Only the untreated pine was slightly affected by decay fungi. There were significant differences in the decay ratings of untreated and thermally modified wood materials after 9 years in the field. While the untreated wood materials were severely attacked by decay fungi or reached failure rating, only small areas of incipient decay were detected in the thermally modified samples. Thermally modified pine was slightly more decayed than thermally modified spruce. The only wood material without any signs of decay was CCA-treated pine, since some of the TBTO-treated pine samples were also moderately attacked by fungal decay. The results of the lap-joint test had a good correlation with mass losses in a laboratory test with brown-rot fungi.     

Fungal–copper interactions in wood examined with large field of view synchrotron-based X-ray fluorescence microscopy

ABSTRACT

The goal of this study was to demonstrate how synchrotron-based X-ray fluorescence microscopy (XFM) can be used to better understand the mechanisms of copper tolerance in wood decay fungi. Copper is a major component in commercial wood preservatives as it is toxic to many wood decay fungi. However, certain fungi are copper tolerant and can attack preservative-treated wood, resulting in structural damage to treated wood members. Here we used large-field XFM to visualize six different elements (K, Ca, Mn, Fe, Cu, and Zn) in the mycelia and wood inoculated with four different species of brown rot wood decay fungi. Wood blocks were partially dipped into a solution of copper sulfate, exposed to fungi in malt extract agar petri dish assays for nine weeks, and then imaged and compared to blocks that were partially dipped in water. The blocks were imaged immediately adjacent to an end-matched control that was placed in malt extract agar petri dish assays for 9 weeks, but not exposed to the fungi so that the differences in the elemental distributions could be directly compared. The colonized wood and mycelia were rich in K, Ca, Mn, and Fe; however, the elements and the spatial distribution in the mycelia and wood differed across fungal species. The most interesting results were the maps showing the copper distribution. While three of the four fungi grew on the copper-rich region of the wood, only one species, Fibroporia radiculosa, dramatically reduced the copper concentration in the region of fungal growth.