The Cation Exchange Capacity of Fibrous Feedstuff and Its Nutritive Characteristics

Current researches on the nutritive characteristics of fibrous feedstuff through determining thefeedstuff cation exchange capacity (CEC) to evaluate its nutritive value at home and abroad were comprehen-sively discribed, and the methods of determining CEC value and the correlation between CEC value and chemi-cal compositions, pH value, and the effect of CEC value on the digestion kinetics in ruminants were also em-phatically introduced. The results of research showed that the CEC values of different feedstuff are different,closely correlated with nitrogen and acid detergent fibre (ADF) and lignin (LIG) content of the feedstuff. Atthe same time, there are markedly effect of CEC value in diet on the nutrients flow of digesta in the digestivetract of ruminants, the degradation rate and digestibility of nutrients in the rumen.     

镁铝双氢氧化物和镁铁铝改性蒙脱土去除水体中磷的吸附效果研究

通过间歇式批实验和动力学实验研究了不同pH条件下磷酸盐在镁铝双氢氧化物(Mg-Al-LDH)、钠基膨润土(Na-Mt)及镁铁铝改性膨润土(Mg-Al-Mt、Fe-Mt和Fe-Al-Mt)的吸附特征。结果表明,在pH4.5～9.0范围内,随着pH的升高,Na-Mt,Fe-Mt和Fe-Al-Mt3种矿物对磷的吸附率相应减少,镁铝双氢氧化物对磷的吸附率有所增加;Mg-Al-LDH、Fe-Mt和Fe-Al-Mt的对磷吸附率约为95%,比Mg-Al-Mt高40%,比Na-Mt高80%。用Langmuir方程描述磷的等温吸附过程,最大吸附容量(Qm)大小顺序为Fe-Al-Mt>Fe-Mt>Mg-Al-LDH>Mg-Al-Mt>Na-Mt,b值大小依次为Mg-Al-LDH>Fe-Mt>Fe-Al-Mt>Mg-Al-Mt>Na-Mt,最大缓冲容量(Qmb)以Mg-Al-LDH的为最大,Na-Mt的为最小;Freundlich等温吸附方程参数KF代表相对吸附容量,以Mg-Al-LDH的KF值最高,依次是Fe-Mt、Fe-Al-Mt和Mg-Al-Mt,Na-Mt的KF值最小,这与Qmb的结果一致;决定系数(R2)表明,Langm...     

围海造田水稻土磷吸附动力学特征及其机理

沿海农田N、P排放是沿海湿地和近海水质污染源之一.研究围海造田土壤P化学行为对评价其水质污染风险,制定兼顾农业生产和环境保护P肥管理措施具有实际意义.本研究以浙江省慈溪市3个代表性时期(宋代,明代,现代)围海造田水稻田土壤为研究对象,研究了3种温度条件下(15℃,25℃,35℃)土壤P吸附动力学,并获得了其热力学参数....     

No UV enhancement of litter decomposition observed on dry samples under controlled laboratory conditions

In field studies, various workers have observed a stimulation of organic matter breakdown by visible light and UV radiation. We aimed to confirm the involvement of UV radiation under controlled laboratory conditions and quantify the magnitude of any stimulation. Grass and pine foliage samples were oven-dried and continuously exposed to UV radiation at room temperature for up to 60 days. A range of UV flux densities was established using shading to different levels. After UV exposure under air-dry conditions, samples were rewetted and incubated in the dark with microbial inoculums to investigate whether UV exposure had rendered samples more susceptible to subsequent microbial decomposition.However, we found no weight loss associated with different UV flux densities. The same finding held true for grass and pine litter samples. Similarly, microbial decomposition of either grass or pine litter was not enhanced by prior UV exposure. These findings suggest that UV-induced photooxidation of dry materials cannot be responsible for the observed apparent enhancement of weight loss of litter samples under UV exposure in the field.     

Characterisation of cold-tolerant fungi from a decomposing High Arctic moss

Given that changes in the patterns of vegetation and size of carbon (C) pools in the Arctic are likely to be profound by the end of this century, it is necessary to characterise the identity and ecological groupings, in terms of temperature response and C substrate utilisation, of saprotrophic (decomposer) fungi in organic matter in Arctic soils. Thus, the aims of this study were: (1) to identify the fungi isolated from standing-dead material of Schistidium apocarpum, as an example of a High Arctic moss, (2) to determine mycelial extension rates of these fungi at a range of temperatures (4, 10 and 25 °C), and (3) to characterise the functional potential, defined by C substrate utilisation at 6 °C, of fungal taxa.Fungi were isolated at 4 °C from standing-dead material of S. apocarpum from an area of polar semi-desert (79 degrees N), close to Ny-Ålesund, Svalbard, in the High Arctic. From a collection of 662 isolates, 43 pure cultures were identified by DNA extraction, amplification, and sequencing. Phoma sclerotioides, previously known as a temperate snow mould, was isolated most frequently. The ecology of fifteen fungal isolates was characterised in detail. In terms of temperature response, two groups were apparent, one of truly psychrophilic/psychrotrophic fungi and one of more mesophilic fungi which were generally less frequently isolated. In terms of carbon substrate utilisation in semi-defined solid media, most fungi could utilise a variety of carbon substrates (degradation of casein, cellulose and starch was widespread), except for tannic acid (degraded by only two of the five P. sclerotioides isolates and Scytalidium lignicola) and lignin and chitin (not decomposed by any isolate). The majority of isolates had been recorded previously from polar environments and/or as being able to survive at low temperatures.Fungi in tundra ecosystems, therefore, have significant potential to mineralise C at temperatures below 10 °C. A better understanding of the ecology of these fungi will allow us to improve predictions of C dynamics in arctic biomes in the future.     

Soil classification provides a poor indicator of carbon turnover rates in soil

Most soil surveys are based on soil geomorphic, physical and chemical properties, while many classifications are based on morphological properties in soil profile. Typically, microbial properties of the soil (e.g. biomass and functional diversity) or soil biological quality indicators (SBQIs) are not directly considered in soil taxonomic keys, yet soil classification schemes are often used to infer soil biological function relating to policy (e.g. soil pollution attenuation, climate change mitigation). To critically address this, our aim was to assess whether rates of carbon turnover in a diverse range of UK soils (n > 500) could effectively be described and sub-divided according to broadly defined soil groups by conventional soil classification schemes. Carbon turnover in each soil over a 90 d period was assessed by monitoring the mineralisation of either a labile (¹⁴C-labelled artificial root exudates) or more recalcitrant C source (¹⁴C-labelled plant leaves) in soil held at field capacity at 10 °C. A double exponential first order kinetic model was then fitted to the mineralisation profile for each individual substrate and soil. ANOVA of the modelled rate constants and pool sizes revealed significant differences between soil groups; however, these differences were small regardless of substrate type. Principle component and cluster analysis further separated some soil groups; however, the definition of the class limits remained ambiguous. Exclusive reference values for each soil group could not be established since the model parameter ranges greatly overlapped. We conclude that conventional soil classification provides a poor predictor of C residence time in soil, at least over short time periods. We ascribe this lack of observed difference to the high degree of microbial functional redundancy in soil, the strong influence of environmental factors and the uncertainties inherent in the use of short term biological assays to represent pedogenic processes which have taken ca. 10,000 y to become manifest.     

Soil fauna feeding activity in temperate grassland soils increases with legume and grass species richness

Edaphic fauna contributes to important ecosystem functions in grassland soils such as decomposition and nutrient mineralization. Since this functional role is likely to be altered by global change and associated shifts in plant communities, a thorough understanding of large scale drivers on below-ground processes independent of regional differences in soil type or climate is essential. We investigated the relationship between abiotic (soil properties, management practices) and biotic (plant functional group composition, vegetation characteristics, soil fauna abundance) predictors and feeding activity of soil fauna after accounting for sample year and study region. Our study was carried out over a period of two consecutive years in 92 agricultural grasslands in three regions of Germany, spanning a latitudinal gradient of more than 500 km. A structural equation model suggests that feeding activity of soil fauna as measured by the bait-lamina test was positively related to legume and grass species richness in both years. Most probably, a diverse vegetation promotes feeding activity of soil fauna via alterations of both microclimate and resource availability. Feeding activity of soil fauna also increased with earthworm biomass via a pathway over Collembola abundance. The effect of earthworms on the feeding activity in soil may be attributed to their important role as ecosystem engineers. As no additional effects of agricultural management such as fertilization, livestock density or number of cuts on bait consumption were observed, our results suggest that the positive effect of legume and grass species richness on the feeding activity in soil fauna is a general one that will not be overruled by regional differences in management or environmental conditions. We thus suggest that agri-environment schemes aiming at the protection of belowground activity and associated ecosystem functions in temperate grasslands may generally focus on maintaining plant diversity, especially with regard to the potential effects of climate change on future vegetation structure.     

生物质焦的水蒸气汽化动力学研究

生物质气化包括生物质的热解及随后的生物质焦的水蒸汽气化过程。为了给生物质气化反应器的设计提供基础数据,利用热天平试验装置对1?273?K制备的生物质焦行了水蒸汽气化反应性试验,研究了气化温度对气化反应性、平均比气化速率、反应速率等的影响。并且利用均相模型和缩芯模型拟合试验数据求得了相应的动力学参数。得出结论：随着温度的增加,焦炭气化反应性增加,平均比气化速率增加。由均相模型所算得活化能为181.24 kJ/mol,指前因子为5.19×105 min-1,缩芯模型所算得活化能为192.87 kJ/ mol,指前因子为1.60×106 min-1。在转化率为10%～75%范围内,均相模型和缩芯模型均可以很好的描述生物质焦的水蒸汽气化行为,但是缩芯模型比均相模型的拟合效果要好。     

新疆几种耕地土壤钾吸附与解吸特性研究

采用连续液流法研究新疆 6种不同土类的耕地土壤 K 吸附与解吸的动力学特性。结果表明 :1不同土类土壤 K 吸附与解吸的反应平衡时间有很大不同 ,其中 ,水稻土、灰漠土达到吸附和解吸的平衡时间与灰钙土达到解吸平衡的时间比其它土类达到平衡的时间要长 ,且平衡以后 ,K 的吸附量或解吸量仍有明显的增加。 6种土类的吸附、解吸时间及平衡吸附、解吸量同土壤粘粒含量有关。 2平衡前不同时段的吸附、解吸速度和吸附、解吸率与反应时间 lnt有极显著的线性相关 ,且与土壤粘粒含量密切相关。 3一级反应方程是描述土壤 K 吸附与解吸反应的最佳动力学模型     

乙酰甲胺磷水解动力学研究

采用气谱-质谱联用的分析方法,研究了乙酰甲胺磷在不同pH和温度条件下的水解动力学.结果表明,乙酰甲胺磷在酸性条件下比较稳定,不易水解,在碱性条件下水解速率较快,25℃时,乙酰甲胺磷在pH5.0,7.0,9.0水解速率常数分别为5.3×10-3,1.99×10-2,7.42×10-2 d-1,半衰期分别为130.8,34.83,9.34 d;50℃时,水解速率常数为1.012×10-1,2.04×10-1,7.542×10-1 d-1,半衰期为6.85,3.40,0.92 d.温度升高有利于乙酰甲胺磷的水解反应,pH5.0,7.0,9.0缓冲溶液中的水解活化能分别为94.38,74.47,74.19 kJ/mol;在酸性环境中,水解速率受温度影响更为显著.