典型农业生态工程运行机制分析—以山东省西单村为例

通过对典型农业生态工程结构的研究,分析了生态农业系统的运行机制,结果表明,结构多样性与主导性关系的协调问题,是目前制约农业生态系统良性循环的根本问题,山东省西单村农业生态系统之所以以前期能够保持持续稳定发展,后期出现减缓趋势,主要原因也是由于其系统的结构多样性比较高,结构多样性指数最高达0．6556,结构链内部各组分之间的协调性超过90％,而系统实际主导性则较低,结构主导性指数最高为0．2574,系统的最高协调性指数只有0．1327,因此,要保证系统的可持续发展,必须保证系统结构的协调性。     

还田秸秆分解与氮素释放的动态模拟

还田秸秆的分解与氮素释放动态是作物养分管理的重要依据。建立了秸秆分解氮素释放动态的“整吞”式动态模拟模型。模型由秸秆有机质分解和残余有机质含氮率动态模拟两部分组成,有机质分解的温度效应用指数函数描述,水分效应用分段线性函数描述,用“标准天”反映温度与水分的综合影响,残余有机质含氮率动态变化用“标准天”为变量的函数模拟,初始秸秆含氮量与残余秸秆含氮量之差即为秸秆分解的氮素净释放。“整吞”式较之“吃馅饼”式建模构思,所需参数少且易通过实验获得,增加了模型的可用性,利用在淮北滨海地区小麦的试验资料对模型的有效性进行了验证。     

环境因子对农业土壤有机碳分解的影响

为研究环境因子对有机C在农业土壤中分解的影响 ,在不同温度、水分及土壤质地下进行小麦和水稻秸秆及其根培养实验 ,结果表明 ,在同样的水热条件下 ,秸秆有机C的分解量大于根的分解量 .在温度较低情况下 ,升高温度促进了有机C的分解 ;而在温度较高的情况下 ,升高温度对有机C分解的促进作用降低 .在非淹水条件下 ,温度对有机C分解的影响随着时间的延长而逐步减小 .淹水条件下培养一周后 ,温度对有机C分解的影响不随时间而变化 .当含水量为 30 0 g·kg-1和 5 0 0 g·kg-1时 ,有机C分解较快 ,而在 2 0 0 g·kg-1和淹水条件下则分解较慢 ,空白对照培养结果的趋势是分解速率随水分含量的增加而加快 .培养实验的第一个月内 ,小麦秸秆有机C的分解量与土壤粘粒含量呈负相关     

景观水体疏浚底泥的农业利用研究

对运河 (杭州段 )疏浚底泥土地利用的可行性及其生态影响进行了研究 .实验室发芽率测定表明 ,土壤中大量掺入疏浚底泥对种子发芽率有一定的影响 ,但在盆栽中影响很小 .疏浚底泥田间投放量在 2 70t·hm-2 以下 ,对青菜的生长具有促进作用 ,超过 2 70t·hm-2 以上用量对青菜产量有一定影响 .与青菜相比 ,草坪草、园艺花卉对底泥投放量具有更大的耐性 ,表现出明显的促进生长现象 .底泥用量在 10 80t·hm-2 以下时青菜中Cu、Zn含量均未超过食品卫生标准 ,用量为 135 0t·hm-2 时则均超过了标准 .原状土柱淋洗实验发现底泥用量在 4 5 0t·hm-2 以下未造成地下水污染 ,表明运河底泥直接土地利用较一般污水污泥堆肥的危害更小 ,园林投放比农田投放具有更大的可行性 ,土地利用是一种经济可行的疏浚底泥处置方法     

CH4 emissions from rice paddies managed according to farmer's practice in Hunan, China

We measured CH₄ emissions from ricepaddies managed by farmer's practices inChangsha, Hunan Province, China, from 1995 to1997. During the winter season, rice fieldswere left fallow under either drained(C-Fallow) or flooded conditions (C-Flood), andplanted with either Chinese milk vetch (C-GM)or oil-seed rape (C-Rape). The organic manureproduced in the winter (weeds, Chinese milkvetch, or oil-seed rape straw) was incorporatedin situ before the early-ricetransplanting. Both early-rice and late-ricestraws were removed and the soil was notamended with any exogenous organic manure. For1996 to 1997, the average seasonal CH₄emission for the double rice cropping periodwas the highest from the plot that was floodedin the winter (103.5 g CH₄ m^–2) andlowest from the plot planted and incorporatedwith Chinese milk vetch (32.6 gCH₄ m^–2). Precipitation in the winternot only affected growth of green manure, whichwas incorporated in situ, but might alsoaffect CH₄ emissions during the subsequentrice growing period. Therefore, a simplerelationship could not be found between theincorporated amount of green manure andCH₄ emission. In the plots incorporatedwith vetch and oil-seed rape straw CH₄emissions were significantly less during thesubsequent late-rice period than during theearly-rice period. This phenomenon might beattributed to a ``priming effect' of greenmanure, which exhausted soil labile organicmatter. Based on the CH₄ fluxmeasurements, the total CH₄ emissions fromrice fields in Hunan Province during the ricegrowing season were estimated as 1.56 TgCH₄ in 1996 and 1.06 Tg CH₄ in 1997.Large variation of precipitation in the winterwould be an important factor controlling theannual variation of CH₄ emissions from thetreatments.     

Production of xylanases from rice bran by Streptomyces actuosus A-151

In this study, the agricultural waste was used to screen for an organism that is capable of producing enzymes for degrading xylan and cellulose. Results showed that Streptomyces actuosus A-151, isolated from northern Taiwan, produced β-xylanase when rice bran was used as the sole carbon source. Four xylanases, designated as FI-A, FI-B, FII-A, FII-B, were identified and purified from the culture filtrate of S. actuosus A-151. Their specific activities after purification were 41.3, 86.2, 20.4, 85.2 U/mg, respectively. The pH stability of the four enzymes was: FI-A, 5–8; FI-B, 3–8; FII-A, 5–9; and FII-B, 3–9. The optimum pH for FII-B was 4, and the others were near 5–6. The optimum temperatures for enzyme activities were 60 °C for FII-B, and 70 °C for the others. The thermal stability for all four enzymes were up to 60 °C. The molecular weights of FI-A, FI-B, FII-A, and FII-B xylanases were 30,000, 45,000, 26,000, and 20,000, respectively, by sodium dodecylsulfate–polyacrylamide gel electrophoresis and 30,000, 43,000, 25,000, and 21,000, respectively, by gel filtration. Addition of xylan, shrimp and crab shell powder, and orange peel to the culture medium was found to enhance the production of xylanase.     

苦豆碱及顺式氯氰菊酯对莱田蚜虫群落的毒力研究

研究了植物源杀虫剂苦豆碱及顺式氯氰菊酯对菜田蚜虫群落结构的影响 ,并测定了其对第一优势种菜缢管蚜的杀伤毒力。苦豆碱在 1 %浓度下 ,以药膜法和喷雾法 ,测定其击倒作用 ,KT50 分别为2 9 74和 2 5 38min ;顺式氯氰菊酯在 0 1 %浓度下 ,KT50 分别为 1 73和 0 78min。以点滴法测定此两种杀虫剂对菜缢管蚜的触杀作用 ,LD50 分别为 7 7× 1 0 -4 及 9 2 0 1 μg 头 ,田间以 0 1 %喷雾 ,苦豆碱 1 0d校正防效均可达到 80 % ,而顺式氯氰菊酯仅能达到 30 %。结果显示 ,苦豆碱对菜缢管蚜有极强的毒杀作用 ,同时喷药前后菜田蚜虫群落结构也发生着明显的变化。     

Plant distribution patterns related to species characteristics and spatial and temporal habitat heterogeneity in a network of ditch banks

In this study we investigated the relationship between the distributionpatterns of a number of herbaceous plant species and the isolation and age ofhabitat patches. The study was conducted for a network of ditch banks in anagricultural landscape in The Netherlands. Thirteen plant species were selectedrepresenting contrasting dispersal and seed bank characteristics. Isolation ofhabitat patches was determined by the distance to the nearest occupied patchandby the number of occupied patches in circles of increasing radius around thepatches. Age was the number of years since the creation of the ditches. In amultiple logistic regression model the separate effects of age of the habitatand the spatial variables were analyzed. A number of habitat variables wereusedto correct the effect of habitat quality. We concluded that distributionpatterns of plant species were mainly determined by habitat quality and thepresence of seed sources at short distances (< 25 m). Thisconclusion was independent of the dispersal characteristics of the species.Mostspecies had higher occupation frequencies in older than younger ditch banks.Only species with persistent seeds had comparable occupation probabilities inolder and younger habitat patches, indicating the importance of the soil seedbank as a source of colonization after large-scale disturbances. The effect ofage and management on the occupation probabilities of the species was oftendiminished in the regression model, probably due to correlation between somehabitat variables and the age of the patches.     

21世纪初农业生态系统健康研究方向

农业生态系统健康是指农业生态系统免受发生“失调综合症”,处理胁迫的状态和满足持续生产农产品的能力,目前,农业生态系统健康研究范围主要涉及农业生态系统健康评价方法,土壤质量和水质与农业生态系统健康的联系,农业生态系统健康与人类健康的关系,害虫生态管理对农业生态系统健康的贡献,杂草综合管理在农业生态系统健康中的作用,从生态病理学到农业生态系统健康,线虫群落作为农业生态系统健康指示生物的研究,转基因作物对农业生态系统健康的生态影响评价,农业投入政策对农业生态系统健康的影响,景观生态学在农业生态系统健康评价中的应用,农业生态系统健康与绿色食品开发等,首先论述了农业生态系统健康研究的现状,介绍了农业生态系统健康研究实例-土壤健康的生物指标,最后提出了今后农业生态系统健康的研究方向,为保障农产品安全和增进人类健康提供依据。     

The sensitivity of a species-rich flood-meadow plant community to fertilizer nitrogen: the Lužnice river floodplain,Czech Republic

Concerns over the relative stability or sensitivity of biologicallydiverse ecosystems in relation to environmental change include the effects ofland-use intensification on diverse plant communities. This paper examines thesensitivity of a floristically diverse flood-meadow under hay-cutting managementto nitrogen enrichment, this being a key component of intensified agriculturalmanagement. A gradient of fertilizer nitrogen treatments was applied to a sitein the Czech Republic in two successive seasons and plant community response wasmonitored using measures of species diversity, cover and above-ground primaryproduction. Results show that diversity was supported by annual hay-cuttingmanagement and that the community was highly sensitive to nitrogen enrichment.Fertilization at rates consistent with intensive agricultural practice reducedspecies richness significantly within eight weeks, with forbs and mossparticularly susceptible. The cover and biomass of some grasses were stimulatedby fertilization until constrained by litter accumulation. Over two seasons,fertilization significantly reduced species diversity and simplified communitystructure as inter-specific competitive relations shifted. Biologically diverseflood-meadows therefore seem to be vulnerable to agricultural intensificationand other human activities that promote enhanced nitrogen levels.