黄土旱塬24 a不同秸秆还田土壤碳、氮、磷和胞外酶计量特征

探索黄土旱塬区农田土壤碳、氮和磷生物地球化学循环特征,可为农作物高效生产和土地可持续利用提供科学依据和技术支撑.以山西寿阳24 a玉米旱作试验田为对象,研究长期秸秆覆盖还田、直接还田、过腹还田和不还田对土壤元素和胞外酶活性化学计量比的影响,并计算向量角度和长度用于指示微生物面临的资源限制情况,向量角大于45°和小于45°分别表示微生物受磷限制和氮限制,偏离45°越大表示限制程度越大,向量长度越长表示微生物受碳限制越严重.结果表明：(1)长期秸秆还田土壤C/N和C/P分布在9.81～14.28和14.58～21.92之间,均值分别为12.36和17.51,分别较试验初期降低了6.0%和4.2%;土壤N/P分布在1.27～1.57之间,均值为1.42,较初期提高了2.2%.土壤C/N和C/P均呈现出先降低后升高的变化趋势,土壤N/P基本呈现出持平趋势,且不同秸秆还田处理之间土壤元素计量比均无显著性差异.(2)相比24 a长期不还田处理,长期秸秆覆盖还田处理土壤β-1,4-葡萄糖苷酶(BG)和β-1,4-N-乙酰葡糖氨糖苷酶(NAG)活性显著提高了134.4%和107.5%(P<0.0...     

The Spatiotemporal Structure of Rodent Populations in the Steppe Zone of Western Siberia

The spatial structure of populations has been studied in two rodent species inhabiting the subzone of meadow steppes of the steppe zone of Omsk oblast: the narrow-sculled vole (Microtus gregalis Pall.) and steppe lemming (Lagurus lagurus Pall.). Their populations are represented by combinations of territorial family groups whose structure and spatial distribution vary by season depending on population density, the phase of the population cycle, and the status of their members in the population. In the areas cohabited by M. gregalis and L. lagurus, the pattern of territory use and the rhythm of animal activity during the day depend primarily on their total density: under conditions of low density, the population groups of both species are spatially separated; at increased density, they are distributed with respect to the pattern of daily activity. Both species jointly use part of the territory but at different times of day: M. gregalis, mainly at night and in the morning; L. lagurus, in the daytime.     

Strategies for determining soil-loss tolerance

Excessive soil losses due to erosion or lateral displacement by machinery impair productivity. Some soil loss is tolerable, but not so much that plant productivity diminishes. Thus productivity is the dominant concern in determining soil-loss tolerance. The effects of soil loss on productivity, however, are difficult to determine. Therefore, two alternatives are discussed for determining the limits of soil loss, or soil-loss tolerance. These alternatives are the maintenance of soil organic matter and, for shallow and moderately deep soils, the maintenance of soil depth. They are not new strategies, but our rapidly increasing knowledge of the dynamics of soil organic matter and the rates of soil formation from bedrock or consolidated sediments warrants the reconsideration of these alternatives. Reductions in either soil organic matter or the depth of shallow or moderately deep soils will lead to declining productivity. Soil organic matter, considered to be a surrogate for productivity, is much easier to monitor than is productivity. Also, there are many computer models for predicting the effects of management on soil organic matter. Recently compiled data on rates of soil formation suggest that soil losses of 1 t/a (2.24 Mg/ha yr) are greater than the rate of replenishment by the weathering of lithic or paralithic material in all but very wet climates.     

陕西省的地震危险趋势估计

本文应用计算某一地震带(区)上地震复发周期的公式;T_m=m×10~(bm-a)以及灰色系统理论的动态模型对陕西地区进行了地震危险趋势估计。     

Differences in responses of herpetobionts and geobionts to impact from the Kosogorsky Metallurgical Plant (Tula region,Russia)

The influence of the Kosogorsky Metallurgical Plant (KMP; Tula region, Russia) on the abundance and biodiversity of carabid beetles and soil macrofauna and on the trophic activity of soil biota was studied. Metal concentrations in the impact plot were many times higher than those in the control plot located on the same transect. As the transect approached KMP, both the abundance of soil invertebrates (geobionts) and trophic activity of the soil biota remained unchanged, whereas the abundance and diversity of carabids (herpetobionts) decreased drastically. It is suggested that the impact of the KMP on herpetobionts is accounted for by modification of the structure of ecosystems and that herpetobiontic and geobiontic groups of the macrofauna respond differently to this impact because of differences in the ecological mechanisms of population response.     

Environmental 238U and 232Th concentration measurements in an area of high level natural background radiation at Palong, Johor, Malaysia

Concentrations of uranium-238 and thorium-232 in soil, water, grass, moss and oil-palm fruit samples collected from an area of high background radiation were determined using neutron activation analysis (NAA). U-238 concentration in soil ranged from 4.9 mg kg(-1) (58.8 Bq kg(-1)) to 40.4 mg kg(-1) (484.8 Bq kg(-1)), Th-232 concentration ranged from 14.9 mg kg(-1) (59.6 Bq kg(-1)) to 301.0 mg kg(-1) (1204 Bq kg(-1)). The concentration of U-238 in grass samples ranged from below the detection limit to 0.076 mg kg(-1) (912 mBq kg(-1)), and Th-232 ranged from 0.008 mg kg(-1) (32 mBq kg(-1)) to 0.343 mg kg(-1) (1.372 Bq kg(-1)). U-238 content in water samples ranged from 0.33 mg kg(-1) (4.0 Bq L(-1)) to 1.40 mg kg(-1) (16.8 Bq L(-1)), and Th-232 ranged from 0.19 mg kg(-1) (0.76 Bq L(-1)) to 0.66 mg kg(-1) (2.64 Bq L(-1)). It can be said that the concentrations of environmental U-238 and Th-232 in grass and water samples in the study area are insignificant. Mosses were found to be possible bio-radiological indicators due to their high absorption of the heavy radioelements from the environment.     

晋陕蒙接壤地区的水土流失灾害及其防治

本文对晋陕蒙接壤地区的水土流失情况进行了简要论述,对水土流失的根源进行了探讨,并在此基础上提出了防治水土流失的基本措施。     

高效厌氧产甲烷颗粒污泥中微生物多样性及定量化研究

以小试高效厌氧反应器不同运行阶段的颗粒污泥为对象,利用变性梯度凝胶电泳(DGGE)、荧光原位杂交(FISH)和实时定量链式聚合酶反应(RTQ-PCR)等技术研究了其中微生物种群的多样性、特征微生物的空间分布和定量关系,结果表明:随着反应器有机负荷逐渐提高,颗粒污泥中古菌的群落结构的变化较细菌更为明显;细菌多分布在颗粒外层,而古菌则主要分布在颗粒内层;古菌含量略少于细菌,但有逐渐增多的趋势;产甲烷丝菌在古菌中的含量增加明显.     

电极构型对空气阴极生物燃料电池发电性能的影响

在空气阴极生物燃料电池(ACMFC)中,从阴极扩散进入阳极的氧气能够被兼性微生物作为电子受体还原,进而导致电子损失严重.本研究利用葡萄糖作底物,对2种不同电极构型的空气阴极生物燃料电池ACMFC1和ACMFC2的功率输出和电子回收进行了比较研究.结果表明,ACMFC1的内阻为302.14Ω,阳极电位为-323mV,最大功率密度为3 070 mW/m³;ACMFC2的内阻为107.79Ω,阳极电位为-442mV,最大功率密度达到9 800 mW/m³.在间歇条件下,ACMFC2可以连续运行220h,电子回收率为30.1%;而ACMFC1只能运行不到50h,电子回收率为9.78%.因此,合理的设计空气阴极生物燃料电池电极构型可以减小内阻,增大电池电动势进而增大功率输出,提高电子回收率.