生物入侵对生物多样性以及草地农业生态系统的影响

从生物入侵的原理、生物多样性的概念以及草地农业生态系统的健康评价方面对三者的内在生态关系进行了分析和探讨,以期达到合理引入外来物种、保持生物多样性和稳定草地农业生态系统的三重效应.并在此基础之上提出如何保持生态平衡,使草地农业生态系统能够达到经济、社会和生态三盈,做到可持续的发展.     

草地农业:从结构性描述到精确化发展刍议

从草地农业的雏形--草原学,发展到草业科学,历史发展的脉络反映出,草地农业历经了草原分类,草原生产流程,草地农业生态系统的结构、界面论、时间地带性等结构性描述的过程,正步入精确化发展阶段.这是生产和科学本身发展的需要,也是生产和科学发展过程中提出的命题.提出了:1)包括生态服务价值评价、健康评价在内的生态经济评价理论与方法的探索,将成为草地资源精确化评价的新方向;2)综合运用多种非线性科学方法解决草地农业生态系统的系统耦合和系统相悖的数量化工作可能是系统耦合和系统相悖理论研究和实践的一个非常有前途的方向;3)研究草地农业3个界面的动力学机制的草地农业生态动力学(Pastoral agroecosystem dynamics)将为草地农业精确化发展提供有力的技术支持.     

Functional diversity of cover crop mixtures enhances biomass yield and weed suppression in a Mediterranean agroecosystem

Functional diversity of cover crop mixtures is thought to improve biomass production and weed suppression, two key agroecosystem services in organic systems. To test this hypothesis, we selected eight cover crop species belonging to four functional groups: (i) vining growing large-seeded legumes (field pea, common vetch), (ii) erect growing small-seeded legumes (crimson clover, squarrosum clover), (iii) grasses (barley, oats) and (iv) Brassicaceae (radish, black mustard). Nine cover crop mixtures were designed to create a gradient of diversity in terms of number of species and number of functional groups. A control treatment and all monocrops were included in the trial. Regarding cover crop biomass, mixtures outyielded monocrops by an average of 37%. Both functional identity and composition (i.e. trait complementarity) influenced biomass production and weed suppression provided by cover crops. Regression analysis showed that increase in both species diversity and functional diversity in cover crop mixtures improved the provision of agroecosystem services. Results from this study show that complementarity of species functional traits in cover crop mixtures can be used as a strategy to ensure high biomass production and good weed suppression in changing agroecosystems.     

HOW MULTISPECIES INTERCROP ADVANTAGE RESPONDS TO WATER STRESS: A YIELD-COMPONENT ECOLOGICAL FRAMEWORK AND ITS EXPERIMENTAL APPLICATION

● A framework for multicrop advantage under varying watering conditions is provided. ● This framework clarifies the relation between multicrop overyielding and land use efficiency. ● A novel experimental setup was used to evaluate these theoretical developments. ● Theory and experiment conveyed precise understanding of overyielding scenarios. Absolute yield and land use efficiency can be higher in multicrops. Though this phenomenon is common, it is not always the case. Also, these two benefits are frequently confused and do not necessarily occur together. Cropping choices become more complex when considering that multicrops are subject to strong spatial and temporal variation in average soil moisture, which will worsen with climate change. Intercropping in agroecosystems is expected to buffer this impact by favoring resistance to reduced humidity, but there are few empirical/experimental studies to validate this claim. It is not clear if relatively higher multicrop yield and land use efficiency will persist in the face of reduced soil moisture, and how the relation between these benefits might change. Here, we present a relatively simple framework for analyzing this situation. We propose a relative multicrop resistance (RMR) index that captures all possible scenarios of absolute and relative multicrop overyield under water stress. We dissect the ecological components of RMR to understand the relation between higher multicrop yield and land use efficiency and the ecological causes of different overyield scenarios. We demonstrate the use of this framework with data from a 128 microplot greenhouse experiment with small annual crops, arranged as seven-species multicrops and their corresponding monocrops, all under two contrasting watering regimes. We applied simple but robust statistical procedures to resulting data (based on bootstrap methods) to compare RMR, and its components, between different plants/plant parts. We also provide simple graphical tools to analyze the data.     

农业生态系统内在持续性机制及其调控

本文从农业生态学角度,研究探讨了农业生态系统资源利用的可持续性和农业生态系统内在的能量流动、物质循环、种群调控和动态平衡等功能的持续性机制,并对其调控途径做了初步探讨。     

Carbon and nitrogen emission in agroecosystems of Eastern Siberia

A contribution of agroecosystems of Eastern Siberia to the emission of CO₂ and gaseous nitrogen compounds into the atmosphere has been quantitatively estimated. It has been experimentally demonstrated that agroecosystems are one of the most significant sources of carbon and nitrogen release into the air because of their open cycles. In Eastern Siberia characterized by a highly continental climate the emission of gases from agroecosystems is determined by a complex interaction of natural, anthropogenic and industrial factors. Industrial soil pollution enhances mineralization and reduces immobilization, thus causing gradual humus degradation.     

Phosphorus fertilization alters complexity of paddy soil dissolved organic matter

The structural complexity of soil dissolved organic matter(DOM) may reflect soil biogeochemical processes due to its spectral characteristics. However, the features of DOM structural complexity in paddy soil amended with long-term chemical P fertilization are still unclear, which may limit understanding of nutrient-related soil C cycle. We collected soil samples from field experiments receiving application of 0, 30, 60, and 90 kg P ha~(–1) yr~(–1) to assess the effect of exogenous P on the complexity of soil DOM structure. Three-dimensional excitation-emission matrix fluorescence analysis and enzymatic activity assay were used to determine the features of soil DOM molecular structure and the associated microbial reactions. The results showed that P input increased the biodegradability of DOM, indicating by the increased lower molecular weight components and decreased humic degree in the DOM. P input also reduced the structural complexity of DOM with blue shifts of fluorescent signals. The fluorescence index and β/α index of DOM increased with increasing P application by 4–5% and 3–11%, respectively, while humification index decreased by 8–13%. The P input increased the abundance of bacteria and fungi by 34–167% and 159–964%, respectively, while 29–54% increments were found for the β-1,4-glucosidase activities. These results implicated that P fertilization accelerated the soil DOM cycle, although the structural complexity of DOM declined, which potentially benefits soil C sequestration in paddy fields and may be a C sequestration mechanism in the P-dependent paddy.     

农林产品产地环境生物多样性研究探讨

食品安全是当今世界关注的一个热点,农业生态系统产地环境质量的好坏直接影响着农林产品的质量安全。保护和利用产地环境生物多样性对维持农业生态系统稳定和可持续发展具有重要意义。从生物多样性出发,探讨了产地环境生物多样性现状、丧失原因,提出了产地环境生物多样性的保护措施,旨在促进农业生态系统健康的培育与优质农林产品的实现,为中国农林业可持续发展提供参考。     

Species richness in Mediterranean agroecosystems: Spatial and temporal analysis for biodiversity conservation

We used dung beetles as an indicator group to identify the most important habitats for biodiversity conservation in a Mediterranean traditional agroecosystem. The relationships between traditional grazing and farming activities and biodiversity were analysed by comparing species richness and temporal turnover across three different habitat types, defined according to vegetation structure and human land use. In this study, both spatial (landscape, among-habitats) and temporal (intra-annual, seasonal) analyses were contemplated at mesoscale.The measurement and use of temporal beta diversity (i.e. an index of temporal species turnover) in conservation biology showed that it is a simple method to characterize and compare different habitat species-assemblages, particularly when time seems to be a significant factor in explaining biodiversity features.Our results showed open mosaic areas as the richest and most temporally heterogeneous habitats. We suggest the maintenance of traditional human activities carried out in these areas, since they have been a significant diversification agent, to avoid the loss of the high Mediterranean biological diversity.