猪衣原体感染的血清学调查报告

通过对平顶山地区6个县(市)29个猪场的3000头种猪血清进行鹦鹉热衣原体的间接血凝(IHA)抗体的检测。结果显示,血清的阳性率为3.2%～8%,平均为4.8%,猪场的阳性率为65%,该病在本地区较为普遍。     

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.     

餐厨垃圾堆肥过程中水解酶活性变化的研究

为了研究餐厨垃圾在静态强制通风条件下堆腐过程的矿质化进度和强度。以小麦秸秆作为膨松剂,比较了不同C/N比（20,25,30）条件下餐厨垃圾堆肥过程中各个阶段纤维素酶、蔗糖酶、脲酶、蛋白酶4种水解酶活性的变化情况。结果表明,不同C/N比处理的温度变化趋势基本相同,40℃以上高温期持续达10天左右。25C/N和30C/N堆肥条件下的纤维素酶活整体比20C/N要高,酶活高峰期出现滞后于温度高峰期;不同C/N条件下,蔗糖酶活性变化趋势基本相似,酶活高峰期与温度高峰期同步;30C/N条件下的脲酶活性峰值出现早于20C/N和25C/N,最终脲酶活性下降到比堆肥初期还要低的程度;高温对蛋白酶活性有抑制作用,25C/N条件下蛋白酶活性峰值出现晚于其他2个处理。从试验结果可以看出,不同营养条件下同类酶活性的变化趋势表现出一定的差异,与堆肥过程中有机物质的转化密切相关,可以作为判断堆肥腐熟度的因素之一。     

Rearrangement of bacterial community structure during peat diagenesis

The relationship between microbial diagenesis of Sphagnum peat (SP) and reed-sedge peat (RSP) and the spatial organization of peat bacterial communities was studied. Peats were aerobically incubated at 18-22 °C for 4 months. Changes in molecular composition of peat organic matter were monitored with solid-state ¹³C NMR, and the respective amount of functional groups was determined by integration of corresponding peaks. No abiotic peat transformation was detected. SP diagenesis caused about a 4% loss of parent materials with a similar yield of ketones, phenols, aromatic, and carbonyl compounds; whereas about 20% of RSP carbohydrates, along with ketones and methoxyl compounds were gradually transformed into carbonyl and aliphatic compounds. SP and RSP substantially varied in bacterial composition. To address spatial community structure, bacterial populations were dissected by a differential elution technique into three fractions based on the degree of their attachment to peat. Community composition was surveyed with T-RFLP (HhaI, MspI, and RsaI). The fragments were further attributed to freely-dispersed (FD), particle-associated (PA), or omnipresent (OMN) bacterial fractions. In both peats, bacterial communities have gradually shifted with the progress of diagenesis. In SP, numbers of exclusively FD or PA bacteria slightly decreased while in RSP their numbers more than doubled after 4-month incubation, and the number of OMN bacteria respectively decreased. The substantially greater changes in the spatial structure of RSP bacterial community compared to SP were consistent with the chemical transformations detected in these peats suggesting the diagenesis-driven divergence of RSP bacterial community into FD and PA sub-communities.     

Long-term organic phosphorus mineralization in Spodosols under forests and its relation to carbon and nitrogen mineralization

In forest soils where a large fraction of total phosphorus (P) is in organic forms, soil micro-organisms play a major role in the P cycle and plant availability since they mediate organic P transformations. However, the correct assessment of organic P mineralization is usually a challenging task because mineralized P is rapidly sorbed and most mineralization fluxes are very weak. The objectives of the present work were to quantify in five forest Spodosols at soil depths of 0-15 cm net mineralization of total organic P and the resulting increase in plant available inorganic P and to verify whether net or gross P mineralization could be estimated using the C or N mineralization rates. Net mineralization of total organic P was derived from the net changes in microbial P and gross mineralization of P in dead soil organic matter. We studied very low P-sorbing soils enabling us to use lower extractants to assess the change in total inorganic P as a result of gross mineralization of P in dead soil organic matter. In addition, to enable detection of gross mineralization of P in dead soil organic matter, a long-term incubation (517 days) experiment was carried out. At the beginning of the experiment, total P contents of the soils were very low (19-51 μg g⁻¹) and were essentially present as organic P (17-44 μg g⁻¹, 85-91%) or microbial P (6-14 μg g⁻¹; 24-39%). Conversely, the initial contents of inorganic P were low (2-7 μg g⁻¹; 9-15%). The net changes in the pool size of microbial P during the 517 days of incubation (4-8 μg g⁻¹) and the amounts of P resulting from gross mineralization of dead soil organic matter (0.001-0.018 μg g⁻¹ day⁻¹; 0.4-9.5 μg g⁻¹ for the entire incubation period) were considerable compared to the initial amounts of organic P and also when compared to the initial diffusive iP fraction (<0.3 μg g⁻¹). Diffusive iP corresponds to the phosphate ions that can be transferred from the solid constituents to the soil solution under a gradient of concentration. Net mineralization of organic P induced an important increase in iP in soil solution (0.6-10 μg g⁻¹; 600-5000% increase) and lower increases in diffusive iP fractions (0.3-5 μg g⁻¹; 300-2000% increase), soil solid constituents having an extremely low reactivity relative to iP. Therefore, soil micro-organisms and organic P transformations play a major role in the bioavailability of P in these forest soils. In our study, the dead soil organic matter was defined as a recalcitrant organic fraction. Probably because gross mineralization of P from this recalcitrant organic fraction was mainly driven by the micro-organisms’ needs for energy, the rates of gross mineralization of C, N and P in the recalcitrant organic fraction were similar. Indirect estimation of gross mineralization of P in dead soil organic matter using the gross C mineralization rate seems thus an alternative method for the studied soils. However, additional studies are needed to verify this alternative method in other soils. No relationships were found between microbial P release and microbial C and N releases.     

Microbial use of organic amendments in saline soils monitored by changes in the C/C ratio

An incubation experiment was carried out to investigate whether salinity at high pH has negative effects on microbial substrate use, i.e. the mineralization of the amendment to CO₂ and inorganic N and the incorporation of amendment C into microbial biomass C. In order to exploit natural differences in the ¹³C/¹²C ratio, substrate from two C₄ plants, i.e. highly decomposed and N-rich sugarcane filter cake and less decomposed N-poor maize leaf straw, were added to two alkaline Pakistani soils differing in salinity, which had previously been cultivated with C₃ plants. In soil 1, the additional CO₂ evolution was equivalent to 65% of the added amount in the maize straw treatment and to 35% in the filter cake treatment. In the more saline soil 2, the respective figures were 56% and 32%. The maize straw amendment led to an identical immobilization of approximately 48 μg N g⁻¹ soil over the 56-day incubation in both soils compared with the control soils. In the filter cake treatment, the amount of inorganic N immobilized was 8.5 μg N g⁻¹ higher in soil 1 than in soil 2 compared with the control soils. In the control treatment, the content of microbial biomass C₃-C in soil 1 was twice that in soil 2 throughout the incubation. This fraction declined by about 30% during the incubation in both soils. The two amendments replaced initially similar absolute amounts of the autochthonous microbial biomass C, i.e. 50% of the original microbial biomass C in soil 1 and almost 90% in soil 2. The highest contents of microbial biomass C₄-C were equivalent to 7% (filter cake) and 11% (maize straw) of the added C. In soil 2, the corresponding values were 14% lower. Increasing salinity had no direct negative effects on microbial substrate use in the present two soils. Consequently, the differences in soil microbial biomass contents are most likely caused indirectly by salinity-induced reduction in plant growth rather than directly by negative effects of salinity on soil microorganisms.     

An experimental study of charcoal degradation in a boreal forest

Degradation rates of pyrogenic carbon (PyC) under natural environmental conditions are largely unknown. Here we present results from a field experiment monitoring the change in mass, C- and N concentrations of a variety of charcoal types in a Norwegian boreal forest over a period of 20 months. The charcoal types represent different feedstock tree species, production temperature regimes, and placements in the forest, i.e. above ground, in the humus layer or in contact with the mineral subsoil. The types of charcoal had different initial C concentrations mainly depending on their production temperature. Nevertheless, all types of charcoal at all placements in the forest showed an initial drop in their C concentrations, which subsequently rose back to reach near initial values in part of the charcoal types. In part of the charcoal types, N concentrations decreased throughout the experiment, exhibiting considerable variation among feedstock species, production temperature regime, and placements in the forest. C/N ratios rose especially in charcoal made from wood of Scots pine (Pinus sylvestris L.), and charcoal that had been stored in contact with the mineral subsoil showed the most rapid mass gain. Our results confirm the important influence of production temperature and feedstock type on the degradation of charcoal, but they also show that microbial activity and environmental conditions play significant roles in charcoal degradation and thus for the fate of pyrogenic carbon under natural conditions.     

普通小麦─大赖草6N二体异附加系的选育与鉴定

根据花粉母细胞减数分裂中期Ⅰ染色体配对情况及染色体Ｃ－分带，在中国春－大赖草杂种回交后代中选育出１个稳定的二体异附加系９２Ｇ４６０。通过分析亲本及９２Ｇ４６０的苗期叶片ＧＯＴ同工酶酶谱表型，推测９２Ｇ４６０中临时编为第１１号的大赖草染色体来自Ｎ染色体组，该染色体携有属于第６部分同源群的同工酶结构基因Ｇｏｔ－Ｎ２，故可以将大赖草中临时编为第１１号的染色体命名为６Ｎ。     

Fractal features of soil particle size distribution and the implication for indicating desertification

Some of the effects of land desertification on soil properties are manifested by the coarsening of the soil particlesize distribution (PSD) and the losses in organic C and nutrients. The changes and characteristics of PSD and selected chemical properties in soils at the 0-15 cm plough layer from different degrees of desertified croplands are analyzed in the semiarid Horqin Sandy Land, northern China. The fractal dimension of the PSD is emanated to characterize the patterns of PSD. The relationships between the fractal dimension of the PSD and selected soil properties are discussed. The results show that: (1) in the transformation from potential desertified cropland to extremely desertified cropland, the sand content at the 0-15 cm soil increased from 69% to 93%, organic C and total N contents decreased by 65% and 69%, respectively; (2) the fractal dimension of PSD ranged from 2.179 to 2.611, the more the contents of sand, the lower the fractal dimension and the higher the desertified degree of farmland. In the desertification process within the studied area, the mean fractal dimension decreased from 2.555 for the potential desertified soils to 2.298 for extremely desertified soils; (3) there existed considerable linear relationships between fractal dimension and soil properties. It was shown that fractal dimensions of PSD are useful parameters able to monitor soil degradation and to estimate the degree of soil desertification.     

芝麻新品种郑芝97C01综合表现及栽培技术研究

对郑芝97C01综合分析结果表明,郑芝97C01是一个高产、稳产、优质、多抗的芝麻新品种,一般生育期90d左右,单产1200kg/hm2以上,脂肪含量56.1%,蛋白质含量19.72%,茎点枯病病情指数2.16,枯萎病病情指数1.63,并提出相关的高产栽培技术。