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Agricultural Systems (agricultural + system)
Selected AbstractsDecomposing the Value of Agricultural Multifunctionality: Combining Contingent Valuation and the Analytical Hierarchy ProcessJOURNAL OF AGRICULTURAL ECONOMICS, Issue 2 2007Zein Kallas Q18; Q11; Q25 Abstract Agricultural multifunctionality is the recognition of the joint exercise of economic, environmental and social functions by this sector. Nevertheless, not all these contributions to society are valued in markets, moreover a large share of them are public goods. For this reason, in order to make this concept of multifunctionality operative for the design of public policies, it is necessary to estimate the social demand of such functions. The objective of this article was to implement an empirical application along these lines. For this purpose, the agricultural system of cereal steppes in Tierra de Campos in Spain is taken as a case study. The economic valuation technique used relies on a combined implementation of contingent valuation and the analytical hierarchy process. The results obtained demonstrate the existence of a significant demand for the different attributes included in the multifunctionality concept, although this demand is heterogeneous and is based on the socioeconomic characteristics of individual persons. [source] Nitrogen Sources and Sinks Within the Middle Rio Grande, New Mexico,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2007Gretchen P. Oelsner Abstract:, Relationships between discharge, land use, and nitrogen sources and sinks were developed using 5 years of synoptic sampling along a 300 km reach of the Rio Grande in central New Mexico. Average river discharge was higher during 2001 and 2005 "wet years" (15 m3/s) than during the drought years of 2002-04 "dry years" (8.9 m3/s), but there were no differences in nitrogen loading from wastewater treatment plants (WWTPs) which were the largest and most consistent source of nitrogen to the river (1,330 kg/day). Average total dissolved nitrogen (TDN) concentrations remained elevated for 180 km downstream of the Albuquerque WWTP averaging 1.2 mg/l in wet years and 0.52 mg/l in dry years. Possible explanations for the constant elevated TDN concentrations downstream of the major point source include reduced nitrogen retention capacity, minimal contact with riparian or channel vegetation, large suspended sediment loads, and low algal biomass. Somewhat surprisingly, agricultural return flows had lower average nitrogen concentrations than river water originally diverted to agriculture in both wet (0.81 mg/l) and dry years (0.19 mg/l), indicating that the agricultural system is a sink for nitrogen. Lower average nitrogen concentrations in the river during the dry years can be explained by the input of agricultural returns which comprise the majority of river flow in dry years. [source] Changes in soil C-isotopic composition in an agroecosystem under Free Air Carbon dioxide Enrichment (FACE) treatment during a crop rotation period,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2005Anette Giesemann FACE (Free Air Carbon dioxide Enrichment) has been used since 1999 to evaluate the effects of future atmospheric CO2 concentrations on an arable crop agroecosystem. The experiment conducted at the Institute of Agroecology at the Federal Research Centre in Braunschweig consists of a typical local crop rotation of winter barley, a cover crop, sugar beet and winter wheat. The atmospheric CO2 concentration of ambient air is about 375 ppm with a ,13C value of ,7 to ,9,, and 550,ppm (,13C value,=,,20.2,) during daylight hours in the rings fumigated with additional CO2. Thus, the surplus C can be traced in the agricultural system. Over the course of the first experimental period (3-year crop rotation period), the C-isotopic composition and the C concentration in soil were monitored monthly. Plant samples were analysed according to the relevant developmental stages of the crop under cultivation. A 13C depletion was observed in plant parts, as well as in soil samples from the FACE rings under CO2 enrichment, indicating that labelled C has reached both respective ecosystem compartments. Albeit farming management practice (especially ploughing) leads to a mixing of ,old' and ,new' C compounds throughout all soil horizons down to the end of the ploughing layer and resulted in a heterogeneous distribution of newly formed C compounds in the soil, isotope analysis of soil C reflected where the surplus C went. Copyright © 2005 John Wiley & Sons, Ltd. [source] Atmospheric CO2 enrichment facilitates cation release from soilECOLOGY LETTERS, Issue 3 2010L. Cheng Ecology Letters (2010) 13: 284,291 Abstract Atmospheric CO2 enrichment generally stimulates plant photosynthesis and nutrient uptake, modifying the local and global cycling of bioactive elements. Although nutrient cations affect the long-term productivity and carbon balance of terrestrial ecosystems, little is known about the effect of CO2 enrichment on cation availability in soil. In this study, we present evidence for a novel mechanism of CO2 -enhancement of cation release from soil in rice agricultural systems. Elevated CO2 increased organic C allocation belowground and net H+ excretion from roots, and stimulated root and microbial respiration, reducing soil redox potential and increasing Fe2+ and Mn2+ in soil solutions. Increased H+, Fe2+, and Mn2+ promoted Ca2+ and Mg2+ release from soil cation exchange sites. These results indicate that over the short term, elevated CO2 may stimulate cation release from soil and enhance plant growth. Over the long-term, however, CO2 -induced cation release may facilitate cation losses and soil acidification, negatively feeding back to the productivity of terrestrial ecosystems. [source] A review of nitrogen enrichment effects on three biogenic GHGs: the CO2 sink may be largely offset by stimulated N2O and CH4 emissionECOLOGY LETTERS, Issue 10 2009Lingli Liu Abstract Anthropogenic nitrogen (N) enrichment of ecosystems, mainly from fuel combustion and fertilizer application, alters biogeochemical cycling of ecosystems in a way that leads to altered flux of biogenic greenhouse gases (GHGs). Our meta-analysis of 313 observations across 109 studies evaluated the effect of N addition on the flux of three major GHGs: CO2, CH4 and N2O. The objective was to quantitatively synthesize data from agricultural and non-agricultural terrestrial ecosystems across the globe and examine whether factors, such as ecosystem type, N addition level and chemical form of N addition influence the direction and magnitude of GHG fluxes. Results indicate that N addition increased ecosystem carbon content of forests by 6%, marginally increased soil organic carbon of agricultural systems by 2%, but had no significant effect on net ecosystem CO2 exchange for non-forest natural ecosystems. Across all ecosystems, N addition increased CH4 emission by 97%, reduced CH4 uptake by 38% and increased N2O emission by 216%. The net effect of N on the global GHG budget is calculated and this topic is reviewed. Most often N addition is considered to increase forest C sequestration without consideration of N stimulation of GHG production in other ecosystems. However, our study indicated that although N addition increased the global terrestrial C sink, the CO2 reduction could be largely offset (53,76%) by N stimulation of global CH4 and N2O emission from multiple ecosystems. [source] Spillover edge effects: the dispersal of agriculturally subsidized insect natural enemies into adjacent natural habitatsECOLOGY LETTERS, Issue 5 2006Tatyana A. Rand Abstract The cross-edge spillover of subsidized predators from anthropogenic to natural habitats is an important process affecting wildlife, especially bird, populations in fragmented landscapes. However, the importance of the spillover of insect natural enemies from agricultural to natural habitats is unknown, despite the abundance of studies examining movement in the opposite direction. Here, we synthesize studies from various ecological sub-disciplines to suggest that spillover of agriculturally subsidized insect natural enemies may be an important process affecting prey populations in natural habitat fragments. This contention is based on (1) the ubiquity of agricultural,natural edges in human dominated landscapes; (2) the substantial literature illustrating that crop and natural habitats share important insect predators; and (3) the clear importance of the landscape matrix, specifically distance to ecological edges, in influencing predator impacts in agroecosystems. Further support emerges from theory on the importance of cross-boundary subsidies for within site consumer,resource dynamics. In particular, high productivity and temporally variable resource abundance in agricultural systems are predicted to result in strong spillover effects. More empirical work examining the prevalence and significance of such natural enemy spillover will be critical to a broader understanding of fragmentation impacts on insect predator,prey interactions. [source] Dissipation kinetics and mobility of chlortetracycline, tylosin, and monensin in an agricultural soil in Northumberland County, Ontario, CanadaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2006Jules C. Carlson Abstract A robust high-throughput method was refined to extract three growth-promoting antibiotics, tylosin (TYL), chlortetracycline (CTC), and monensin (MON), from soil. Analysis was performed by electrospray liquid chromatography tandem mass spectrometry. Soil dissipation rate studies were performed in a farm field soil for antibiotics applied with and without manure. Tylosin, CTC, and MON followed first-order dissipation kinetics with half-lives of 4.5, 24, and 3.3 d, respectively, with the addition of manure and 6.1, 21, and 3.8 d, respectively, without manure. Manure application significantly increased TYL dissipation rate, perhaps because of the introduced microbial flora, but had no significant effect on CTC or MON. Monensin dissipation half-life was found to be much shorter in the field study than in a controlled laboratory study, perhaps because of differences in microbial communities. The antimicrobials were not highly mobile. Chlortetracycline was the only antibiotic detected at 25 to 35 cm depth and only up to 2% of the initial concentration in a sandy loam soil. These antibiotics are therefore expected to degrade primarily in agricultural soils before moving to greater depths or to groundwater in significant concentrations in most agricultural systems. [source] Multiple stressors and regime shifts in shallow aquatic ecosystems in antipodean landscapesFRESHWATER BIOLOGY, Issue 2010JENNY DAVIS Summary 1. Changes in land management (land use and land cover) and water management (including extraction of ground water and diversion of surface waters for irrigation) driven by increases in agricultural production and urban expansion (and fundamentally by population growth) have created multiple stressors on global freshwater ecosystems that we can no longer ignore. 2. The development and testing of conceptual ecological models that examine the impact of stressors on aquatic ecosystems, and recognise that responses may be nonlinear, is now essential for identifying critical processes and predicting changes, particularly the possibility of catastrophic regime shifts or ,ecological surprises'. 3. Models depicting gradual ecological change and three types of regime shift (simple thresholds, hysteresis and irreversible changes) were examined in the context of shallow inland aquatic ecosystems (wetlands, shallow lakes and temporary river pools) in southwestern Australia subject to multiple anthropogenic impacts (hydrological change, eutrophication, salinisation and acidification). 4. Changes in hydrological processes, particularly the balance between groundwater-dominated versus surface water-dominated inputs and a change from seasonal to permanent water regimes appeared to be the major drivers influencing ecological regime change and the impacts of eutrophication and acidification (in urban systems) and salinisation and acidification (in agricultural systems). 5. In the absence of hydrological change, urban wetlands undergoing eutrophication and agricultural wetlands experiencing salinisation appeared to fit threshold models. Models encompassing alternative regimes and hysteresis appeared to be applicable where a change from a seasonal to permanent hydrological regime had occurred. 6. Irreversible ecological change has potentially occurred in agricultural landscapes because the external economic driver, agricultural productivity, persists independently of the impact on aquatic ecosystems. 7. Thematic implications: multiple stressors can create multiple thresholds that may act in a hierarchical fashion in shallow, lentic systems. The resulting regime shifts may follow different models and trajectories of recovery. Challenges for ecosystem managers and researchers include determining how close a system may be to critical thresholds and which processes are essential to maintaining or restoring the system. This requires an understanding of both external drivers and internal ecosystem dynamics, and the interactions between them, at appropriate spatial and temporal scales. [source] Soil greenhouse gas fluxes and global warming potential in four high-yielding maize systemsGLOBAL CHANGE BIOLOGY, Issue 9 2007M. A. A. ADVIENTO-BORBE Abstract Crop intensification is often thought to increase greenhouse gas (GHG) emissions, but studies in which crop management is optimized to exploit crop yield potential are rare. We conducted a field study in eastern Nebraska, USA to quantify GHG emissions, changes in soil organic carbon (SOC) and the net global warming potential (GWP) in four irrigated systems: continuous maize with recommended best management practices (CC-rec) or intensive management (CC-int) and maize,soybean rotation with recommended (CS-rec) or intensive management (CS-int). Grain yields of maize and soybean were generally within 80,100% of the estimated site yield potential. Large soil surface carbon dioxide (CO2) fluxes were mostly associated with rapid crop growth, high temperature and high soil water content. Within each crop rotation, soil CO2 efflux under intensive management was not consistently higher than with recommended management. Owing to differences in residue inputs, SOC increased in the two continuous maize systems, but decreased in CS-rec or remained unchanged in CS-int. N2O emission peaks were mainly associated with high temperature and high soil water content resulting from rainfall or irrigation events, but less clearly related to soil NO3 -N levels. N2O fluxes in intensively managed systems were only occasionally greater than those measured in the CC-rec and CS-rec systems. Fertilizer-induced N2O emissions ranged from 1.9% to 3.5% in 2003, from 0.8% to 1.5% in 2004 and from 0.4% to 0.5% in 2005, with no consistent differences among the four systems. All four cropping systems where net sources of GHG. However, due to increased soil C sequestration continuous maize systems had lower GWP than maize,soybean systems and intensive management did not cause a significant increase in GWP. Converting maize grain to ethanol in the two continuous maize systems resulted in a net reduction in life cycle GHG emissions of maize ethanol relative to petrol-based gasoline by 33,38%. Our study provided evidence that net GHG emissions from agricultural systems can be kept low when management is optimized toward better exploitation of the yield potential. Major components for this included (i) choosing the right combination of adopted varieties, planting date and plant population to maximize crop biomass productivity, (ii) tactical water and nitrogen (N) management decisions that contributed to high N use efficiency and avoided extreme N2O emissions, and (iii) a deep tillage and residue management approach that favored the build-up of soil organic matter from large amounts of crop residues returned. [source] Elevated carbon dioxide and irrigation effects on water stable aggregates in a Sorghum field: a possible role for arbuscular mycorrhizal fungiGLOBAL CHANGE BIOLOGY, Issue 3 2001Matthias C. Rillig Summary While soil biota and processes are becoming increasingly appreciated as important parameters for consideration in global change studies, the fundamental characteristic of soil structure is a neglected area of research. In a sorghum [Sorghum bicolor (L.) Moench] field experiment in which CO2[supplied using free-air CO2 enrichment (FACE) technology] was crossed factorially with an irrigation treatment, soil aggregate (1,2 mm) water stability increased in response to elevated CO2. Aggregate water stability was increased by 40% and 20% in response to CO2, at ample and limited water supply treatments, respectively. Soil hyphal lengths of arbuscular mycorrhizal fungi (AMF) increased strongly (with a threefold increase in the dry treatment) in response to CO2, and the concentrations of one fraction (easily extractable glomalin, EEG) of the AMF-produced protein glomalin were also increased. Two fractions of glomalin, and AMF hyphal lengths were all positively correlated with soil aggregate water stability. The present results further support the hypothesis that AMF can become important in global change scenarios. Although in this field study a causal relationship between hyphal length, glomalin and aggregate stability cannot be demonstrated, the present data do suggest that AMF could mediate changes in soil structure under elevated CO2. This could be of great importance in agricultural systems threatened by erosional soil loss. [source] TOPCAT-NP: a minimum information requirement model for simulation of flow and nutrient transport from agricultural systemsHYDROLOGICAL PROCESSES, Issue 14 2008P. F. Quinn Abstract Future catchment planning requires a good understanding of the impacts of land use and management, especially with regard to nutrient pollution. A range of readily usable tools, including models, can play a critical role in underpinning robust decision-making. Modelling tools must articulate our process understanding, make links to a range of catchment characteristics and scales and have the capability to reflect future land-use management changes. Hence, the model application can play an important part in giving confidence to policy makers that positive outcomes will arise from any proposed land-use changes. Here, a minimum information requirement (MIR) modelling approach is presented that creates simple, parsimonious models based on more complex physically based models, which makes the model more appropriate to catchment-scale applications. This paper shows three separate MIR models that represent flow, nitrate losses and phosphorus losses. These models are integrated into a single catchment model (TOPCAT-NP), which has the advantage that certain model components (such as soil type and flow paths) are shared by all three MIR models. The integrated model can simulate a number of land-use activities that relate to typical land-use management practices. The modelling process also gives insight into the seasonal and event nature of nutrient losses exhibited at a range of catchment scales. Three case studies are presented to reflect the range of applicability of the model. The three studies show how different runoff and nutrient loss regimes in different soil/geological and global locations can be simulated using the same model. The first case study models intense agricultural land uses in Denmark (Gjern, 114 km2), the second is an intense agricultural area dominated by high superphosphate applications in Australia (Ellen Brook, 66 km2) and the third is a small research-scale catchment in the UK (Bollington Hall, 2 km2). Copyright © 2007 John Wiley & Sons, Ltd. [source] Use of thermodynamic functions for expressing some relevant aspects of sustainabilityINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2005Simone Bastianoni Abstract Sustainability is a key concept for our future and the role of thermodynamics in its assessment is fundamental. The use of energy and matter must be considered not only from a microscopic viewpoint (the use of a single fuel or material, or the presence of a single pollutant) but also by means of holistic approaches able to synthesize all the characteristics of a single process. Exergy is a suitable function for this purpose. The exergy concept can also be applied to natural systems and to systems at the interface between natural and artificial ones. In this context also emergy can express very helpful indications. Four different efficiency indices are here examined to better understand different aspects of the sustainability of processes and systems. An application to two similar agricultural systems (wine production in Italy) shows how these indices work in real case studies. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effects of predatory ants on lower trophic levels across a gradient of coffee management complexityJOURNAL OF ANIMAL ECOLOGY, Issue 3 2008S. M. Philpott Summary 1Ants are important predators in agricultural systems, and have complex and often strong effects on lower trophic levels. Agricultural intensification reduces habitat complexity, food web diversity and structure, and affects predator communities. Theory predicts that strong top-down cascades are less likely to occur as habitat and food web complexity decrease. 2To examine relationships between habitat complexity and predator effects, we excluded ants from coffee plants in coffee agroecosystems varying in vegetation complexity. Specifically, we studied the effects of eliminating ants on arthropod assemblages, herbivory, damage by the coffee berry borer and coffee yields in four sites differing in management intensification. We also sampled ant assemblages in each management type to see whether changes in ant assemblages relate to any observed changes in top-down effects. 3Removing ants did not change total arthropod densities, herbivory, coffee berry borer damage or coffee yields. Ants did affect densities of some arthropod orders, but did not affect densities of different feeding groups. The effects of ants on lower trophic levels did not change with coffee management intensity. 4Diversity and activity of ants on experimental plants did not change with coffee intensification, but the ant species composition differed. 5Although variation in habitat complexity may affect trophic cascades, manipulating predatory ants across a range of coffee agroecosystems varying in management intensity did not result in differing effects on arthropod assemblages, herbivory, coffee berry borer attack or coffee yields. Thus, there is no clear pattern that top-down effects of ants in coffee agroecosystems intensify or dampen with decreased habitat complexity. [source] Habitat connectivity and matrix restoration: the wider implications of agri-environment schemesJOURNAL OF APPLIED ECOLOGY, Issue 2 2006PAUL F. DONALD Summary 1The spread and intensification of agriculture are recognized as two of the most important global threats to wildlife. There are clear links between agricultural change and declines in biodiversity across a wide range of agricultural systems, and convincing evidence that reversing these changes leads to a recovery in wildlife populations. 2Nearly 4 billion euros are now paid annually through agri-environment schemes (AES) to farmers in Europe and North America to make environmental improvements to their land. Where appropriately designed and targeted, these schemes have proved successful in reversing declines in farmland wildlife populations. 3We argue that insights gained from island biogeography and metapopulation theory, and from theoretical and empirical assessments of landscape connectivity suggest that AES may carry substantial wider benefits, which so far have not been considered in the design and deployment of such schemes. ,Softening' agricultural land could offset some of the negative impacts on biodiversity of the loss and fragmentation of non-agricultural habitats; could allow species to adapt to climate change; could slow the spread of alien and invasive species; and could contribute positively to the coherence of key biodiversity and protected area networks. Indeed, AES might represent the only viable way to counter these threats. 4We outline a number of ways in which these wider benefits could be taken account of in the design of AES and suggest a number of characteristics of the species most likely to benefit from them. 5Synthesis and applications. Agri-environment schemes might bring significant environmental benefits to habitats other than farmland by restoring the agricultural matrix that separates them. Theoretical and empirical research suggests that matrix restoration improves a number of ecosystem functions. Where they are available, AES might therefore represent a viable mechanism for addressing a range of pandemic environmental problems such as global climate change. Little consideration has so far been given to these wider conservation applications in the design, deployment and monitoring of AES. [source] Meeting the ecological challenges of agricultural change: editors' introductionJOURNAL OF APPLIED ECOLOGY, Issue 6 2003S. J. Ormerod Summary 1The global need for agricultural production has never been greater. Nor has it ever been more complex due to the needs to balance global food security, optimum production, technological innovation, the preservation of environmental functions and the protection of biodiversity. The role of ecologists in finding this balance is pivotal. 2In support of this role, ecologists now have very substantial experience of agricultural systems. We can understand, recognize and sometimes predict, at least qualitatively, the effects of pesticide applications, fertilizer use, drainage, crop choices and habitat modifications on farmland organisms, agro-ecosystems or other ecosystems influenced by agricultural land. 3In instances of greater uncertainty, for example under changing climates, where environmental stresses on ecosystems are interactive, and where ecosystem management or restoration must adapt to new technologies, the investigative skills and experience of ecologists are even more crucial in problem solving. 4There are, nevertheless, contrasting examples of good and bad practice in knowledge-transfer between ecologists and the communities who need our knowledge. The UK farm-scale evaluations of genetically modified crops, for example, involved ecologists at all stages from design and data collection to advocating policy. By contrast, many European agri-environment projects appear to have been developed and evaluated with only modest ecological advice. We advocate fuller involvement of ecologists in the development and evaluation of the European Union Common Agricultural Policy. 5This special profile of seven agriculturally related papers illustrates effectively the array of approaches used by applied ecologists in addressing agricultural questions: modelling, meta-analysis, surveys, transect studies, classical experiments, seedbank assays and process studies based on modern ecological methods. With over 20% of recent papers in the Journal of Applied Ecology reflecting agricultural issues, agro-ecology continues to represent one of the pre-eminent areas of applied ecology that is unlikely to diminish in importance. [source] Editors' Introduction: Birds and AgricultureJOURNAL OF APPLIED ECOLOGY, Issue 5 2000S.J. Ormerod 1.,Around 10% of recent papers in the Journal of Applied Ecology have examined interactions between birds and agriculture. This statistic reveals the important role now played by ecologists in assessing the effects of agricultural development worldwide. It also reflects the position of birds as both indicators and targets of agricultural change: their patterns of behaviour, distribution, seasonal phenology and demography track closely onto the spatial and temporal scales of agricultural intensification. 2.,Papers in this Special Profile illustrate how research in this sphere has shifted towards assessing the processes by which birds are affected ecologically by agricultural change. The works examine spatial patterns in extinction; assess long-term trends in bird abundance and agricultural practice; reveal how foraging and breeding performance in farmland birds varies between habitats; and evaluate the role of large-scale modelling in examining hypotheses about the influences of land management on birds. The final paper shows that birds can have intrinsically positive value in agricultural systems. 3.,All the papers propose management prescriptions for agricultural areas that blend the microscopic , for example, how to modify local land structure to benefit birds , and the macroscopic , for example, by suggested inputs into land-use policy. Perhaps most pertinent is the key conclusion that agricultural change is multivariate, so that straightforward univariate effects on birds are unlikely. Restoration of impacted populations might therefore require holistic strategies that encourage appropriately scaled agricultural extensification. Success would be most likely if farmers, conservationists and other key players were engaged collaboratively in the process. 4.,Current ideas about restoring farmland bird populations share a common assumption: if agricultural practice has reduced populations hitherto, then agricultural practice can restore the losses. We suggest that this assumption carries a range of predictions that now require testing through sustainable farm management , a situation ideally suited to ,BACI' style experiments. 5.,We reiterate the need to expand work on other groups of organisms affected negatively or positively by agricultural management to allow a broader perspective of impacts or benefits. [source] Environmental stresses mediate endophyte,grass interactions in a boreal archipelagoJOURNAL OF ECOLOGY, Issue 2 2010Nora M. Saona Summary 1.,Both evolutionary theory and empirical evidence from agricultural research support the view that asexual, vertically transmitted fungal endophytes are typically plant mutualists that develop high infection frequencies within host grass populations. In contrast, endophyte,grass interactions in natural ecosystems are more variable, spanning the range from mutualism to antagonism and comparatively little is known about their range of response to environmental stress. 2.,We examined patterns in endophyte prevalence and endophyte,grass interactions across nutrient and grazing (from Greylag and Canada geese) gradients in 15 sites with different soil moisture levels in 13 island populations of the widespread grass Festuca rubra in a boreal archipelago in Sweden. 3.,In the field, endophyte prevalence levels were generally low (range = 10,53%) compared with those reported from agricultural systems. Under mesic-moist conditions endophyte prevalence was constantly low (mean prevalence = 15%) and was not affected by grazing pressure or nutrient availability. In contrast, under conditions of drought, endophyte prevalence increased from 10% to 53% with increasing nutrient availability and increasing grazing pressure. 4.,In the field, we measured the production of flowering culms, as a proxy for host fitness, to determine how endophyte-infected plants differed from uninfected plants. At dry sites, endophyte infection did not affect flowering culm production. In contrast, at mesic-moist sites production of flowering culms in endophyte-infected plants increased with the covarying effects of increasing nutrient availability and grazing pressure, indicating that the interaction switched from antagonistic to mutualistic. 5.,A concurrent glasshouse experiment showed that in most situations, the host appears to incur some costs for harbouring endophytes. Uninfected grasses generally outperformed infected grasses (antagonistic interaction), while infected grasses outperformed uninfected grasses (mutualistic interaction) only in dry, nutrient-rich conditions. Nutrient and water addition affected tiller production, leaf number and leaf length differently, suggesting that tillers responded with different strategies. This emphasizes that several response variables are needed to evaluate the interaction. 6.,Synthesis. This study found complex patterns in endophyte prevalence that were not always correlated with culm production. These contrasting patterns suggest that the direction and strength of selection on infected plants is highly variable and depends upon a suite of interacting environmental variables that may fluctuate in the intensity of their impact, during the course of the host life cycle. [source] Ecosystem science and human,environment interactions in the Hawaiian archipelagoJOURNAL OF ECOLOGY, Issue 3 2006PETER VITOUSEK Summary 1Tansley's ecosystem concept remains a vital framework for ecological research in part because the approach facilitates interdisciplinary analyses of ecological systems. 2Features of the Hawaiian Islands , particularly the nearly orthogonal variation in many of the factors that control variation among ecosystems elsewhere , make the archipelago a useful model system for interdisciplinary research designed to understand fundamental controls on the state and dynamics of ecosystems, and their consequences for human societies. 3Analyses of rain forest sites arrayed on a substrate age gradient from c. 300 years to over 4 million years across the Hawaiian archipelago demonstrate that the sources of calcium and other essential cations shift from > 80% rock-derived in young sites to > 80% derived from marine aerosol on substrates older than 100 000 years. Rock-derived phosphorus is retained longer within ecosystems, but eventually long-distance transport of continental dust from Asia becomes the most important source of phosphorus. 4A biogeochemical feedback from low nutrient availability to efficient resource use by trees to slow decomposition and nutrient regeneration accentuates the geochemically driven pattern of low phosphorus availability and phosphorus limitation to net primary productivity in the oldest site. 5Variations in ecosystem biogeochemistry across the archipelago shaped the development and sustainability of Polynesian agricultural systems in the millennium between their discovery of Hawai'i and contact by Europeans. Irrigated pondfields were largely confined to stream valleys on the older islands, while rain-fed dryland systems occupied a narrow zone of fertile, well-watered soils on the younger islands. 6The ecosystem approach often represents the most appropriate level of organization for analyses of human influences on ecological systems; it can play a central role in the design and analysis of alternative agricultural, industrial and residential systems that could reduce the human footprint on the Earth. [source] Floodplain agricultural systems: functionality, heritage and conservationJOURNAL OF FLOOD RISK MANAGEMENT, Issue 3 2010H.F. Cook Abstract Floodplain infrastructural features reduce flood risk and have the potential to enhance habitat, biodiversity, water quality and provide societal benefits. Man-made water management systems common in southern England are both flood tolerant and form part of the functional floodplain. Historic floodplain features should be incorporated into agri-environmental policy, as climate change and increasing climate variability makes flood detention areas ever more desirable. Of major importance are floodplain meadows, grazing marshes, water meadows and riparian vegetation, and there is a trend to restore river channels to more natural conditions. This paper describes the operation of historic floodplain water management systems and considers the features associated with canals and mills. The major themes in achieving conservation and restoration goals are presented, and it is demonstrated that a refinement of policies on the ground is required. [source] Mycorrhizal fungi as mediators of defence against insect pests in agricultural systemsAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2009Rachel L. Vannette Abstract 1Below-ground organisms influence above-ground interactions in both natural and agricultural ecosystems. Among the most important below-ground organisms are mycorrhizal fungi, comprising ubiquitous and ancient plant mutualists that have significant effects on plant growth and fitness mediated by resource exchange with plants. In the present study, we focus on the effects of arbuscular mycorrhizal fungi (AMF) on crop defence against insect pests. 2AMF alter the availability of resources used by crop plants to manufacture defences against pests and to compensate for pest damage. However, AMF also provide plants with nutrients that are known to increase insect performance. Through potentially opposing effects on plant nutritional quality and defence, mycorrhizal fungi can positively or negatively affect pest performance. 3Additionally, AMF may directly affect gene expression and plant defence signalling pathways involved in the construction and induction of plant defences, and these effects are apparently independent of those caused by nutrient availability. In this way, AMF may still influence plant defences in the fertilized and highly managed systems typical of agribusiness. 4Because AMF can affect plant tolerance to pest damage, they may have a significant impact on the shape of damage,yield relationships in crops. Potential mechanisms for this effect are suggested. 5We highlight the need for continuing research on the effects of AMF identity and the abundance on crop defences and tolerance to pest attack. Much work is needed on the potential effects of mycorrhizal colonization on plant signalling and the induction of direct and indirect defences that may protect against pest damage. [source] Insecticidal activity of garlic juice in two dipteran pestsAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2006Gareth M. Prowse Abstract 1Botanical products excluding pyrethroids constitute a small, but growing portion of the U.K. pesticides market. With increasing legislative pressure upon chemical pesticides such as organophosphates, interest in this sector is increasing steadily. 2Garlic Allium sativum L. juices and extracts form the basis of several commercially available pest control products, but the performance of these products is variable, possibly due to lack of quality control upon batches of materials in the manufacturing process. 3Some garlic products designed for use in the food industry are subjected to rigorous batch-control to ensure organoleptic consistency. We studied the insecticidal efficacy of a commercially produced food grade garlic juice using two target dipteran pests, Delia radicum (L.) and Musca domestica L. 4Exposure of the two species to different concentrations of garlic juice revealed variability in insecticidal effect across life stages. LC50 values recorded for D. radicum were: eggs (7-day exposure) 0.8%; larvae (24-h exposure) 26.4%; larvae (48-h exposure) 6.8%; and adults (24-h exposure) 0.4%. LC50 values recorded for M. domestica were: eggs (7-day exposure) 1.6%; larvae (24-h exposure) 10.1%; larvae (24-h exposure) 4.5%; and adults (24-h exposure) 2.2%. 5Mortality rates caused by the garlic juice were comparable with those obtained with the organophosphate pesticide Birlane®, indicating parity of effect at various concentrations depending on life stage. 6We conclude that this product may provide an effective, naturally-derived insecticide for use in agricultural systems against dipteran pests. [source] Leaf beetle grazing does not induce willow trichome defence in the coppicing willow Salix viminalisAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2004Peter Dalin Abstract 1,Willows are frequently attacked and defoliated by adult leaf beetles (Phratora vulgatissima L.) early in the season and the plants are then attacked again when new larvae emerge. The native willow Salix cinerea has previously been shown to respond to adult grazing by producing new leaves with an increased trichome density. Subsequent larval feeding was reduced on new leaves. This type of induced plant response may reduce insect damage and could potentially be utilized for plant protection in agricultural systems. 2,Here, we investigated if the willow species most commonly used for biomass production in short rotation coppice, Salix viminalis, also responds to adult beetle grazing by increasing trichome density. Larval performance and feeding behaviour on plants previously exposed to adult beetles was compared with that on undefoliated control plants in a greenhouse. 3,We found an overall decrease in trichome density within all the plants (i.e. trichome density was lower on new leaves compared to that for older basal leaves on S. viminalis). However, leaves of beetle defoliated plants had a higher trichome density compared to control plants. Larval growth and feeding was not affected by this difference between treatments. Larvae appeared to remove trichomes when feeding on S. viminalis, a behaviour that might explain the lack of difference between treatments. [source] Using Home Gardens to Decipher Health and Healing in the Andes.MEDICAL ANTHROPOLOGY QUARTERLY, Issue 4 2003Ruthbeth Finerman Home gardens are a pervasive component of Andean agricultural systems, but have been ignored in anthropological and agronomic research. Recent research in the indigenous community of Saraguro, Ecuador, employed a combination of in-depth interviews, free-listing, videotaped walk-throughs, and mapping to explore the role of home gardens, which are established and controlled by women. Findings reveal that, although gardens offer multiple benefits, they are overwhelmingly devoted to the cultivation of medicinal plants, operating as de facto medicine cabinets that supply women with most of the resources they need to treat family illnesses. Results also suggest that the natural history of home gardens mirrors transformations within the family, and that Saraguro women study the contents of their neighbors' gardens, using this knowledge as a foundation for deciphering the owners' economic and health status. New threats to the sustainability of home gardens threaten the foundation of Saraguro's ethnomedical system and women's authority in the home and community. [ethnobotany, gardens, Ecuador, women healers, family health] [source] Agroecosystem modeling and optimal economic decisions: Implications for sustainable agricultureOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 1 2008Craig A. Bond Abstract We adapt a biogeochemical model of an agroecosystem to account for optimal economic behavior on the part of agricultural producers. Two institutional management regimes are considered: one in which a representative producer does not account for stock pollution caused by use of agricultural inputs, and one in which the externality is internalized. Comparative statics of the steady state of the former problem are analyzed in order to gain insight into the effects of potential policy and technological changes. Results show that a more realistic ecosystem component that includes nutrient cycling can qualitatively change optimal management practices relative to a one-state representation, potentially rendering systems ,unsustainable' under some criteria and leading to policy instruments that exacerbate, rather than mitigate, external damages or the resource base. Moreover, the qualitative effect of changes in model parameters are not necessarily uniform across different agricultural systems, implying that a prescription for the so-called ,sustainable' management under one system may have unintended consequences under another system. Copyright © 2007 John Wiley & Sons, Ltd. [source] The presence of Rickettsia is associated with increased susceptibility of Bemisia tabaci (Homoptera: Aleyrodidae) to insecticidesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 8 2008Svetlana Kontsedalov Abstract BACKGROUND: The presence of certain symbiotic microorganisms may be associated with insecticide resistance in insects. The authors compared the susceptibility of two isofemale lines, Rickettsia -plus and Rickettsia -free, of the sweet potato whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) to major insecticides from different chemical groups, including imidacloprid, acetamiprid, thiamethoxam, pyriproxyfen, spiromesifen and diafenthiuron. RESULTS: While the Rickettsia -plus and Rickettsia -free lines showed no differences in their susceptibility to imidacloprid and diafenthiuron, higher susceptibility of the Rickettsia -plus line to acetamiprid, thiamethoxam, spiromesifen and especially pyriproxyfen was observed. LC90 values indicated that the Rickettsia -free line was 15-fold more resistant to pyriproxyfen than the Rickettsia -plus line. CONCLUSION: Findings indicate that the infection status of B. tabaci populations by Rickettsia is an important consideration that should be taken into account when performing resistance monitoring studies, and may help in understanding the dynamics of B. tabaci resistance, symbiont-pest associations in agricultural systems and the biological impact of Rickettsia on whitefly biology. Copyright © 2008 Society of Chemical Industry [source] Paraquat and sustainable agriculturePEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 4 2004Richard H Bromilow Abstract Sustainable agriculture is essential for man's survival, especially given our rapidly increasing population. Expansion of agriculture into remaining areas of natural vegetation is undesirable, as this would reduce biodiversity on the planet. Maintaining or indeed improving crop yields on existing farmed land, whether on a smallholder scale or on larger farms, is thus necessary. One of the limiting factors is often weed control; biological control of weeds is generally of limited use and mechanical control is either often difficult with machinery or very laborious by hand. Thus the use of herbicides has become very important. Minimum cultivation can also be important, as it reduces the power required to work the soil, limits erosion and helps to maintain the organic matter content of the soil. This last aspect helps preserve both the structure of soil and its populations of organisms, and also sustains the Earth's soil as a massive sink for carbon, an important consideration in the light of global warming. The introduction of the bipyridinium herbicide paraquat in the early 1960s greatly facilitated weed control in many crops. Paraquat has the unusual property of being active only by direct spray onto plants and not by uptake from soil in which strong binding deactivates it. Together with its rapid action in light in killing green plant tissue, such properties allow paraquat to be used in many crops, including those grown by low-tillage methods. This paper reviews the ways in which agricultural systems have been and are being developed to make use of these properties, and provides a risk/benefit analysis of the world-wide use of paraquat over nearly 40 years. Copyright © 2004 Society of Chemical Industry [source] Effects of elevated CO2, drought and temperature on the water relations and gas exchange of groundnut (Arachis hypogaea) stands grown in controlled environment glasshousesPHYSIOLOGIA PLANTARUM, Issue 1 2000Sean C. Clifford Stands of groundnut (Arachis hypogaea L. cv. Kadiri-3) were grown in controlled environment glasshouses at mean atmospheric CO2 concentrations of 375 or 700 ,mol mol,1 and daily mean air temperatures of 28 or 32°C on irrigated or drying soil profiles. Leaf water (,l) and solute potential (,s), relative water content (RWC), stomatal conductance (gl) and net photosynthesis (Pn) were measured at midday for the youngest mature leaf throughout the growing season. Elevated CO2 and temperature had no detectable effect on the water relations of irrigated plants, but higher values of RWC, ,l and ,s were maintained for longer under elevated CO2 during progressive drought. Turgor potential (,p) reached zero when ,l declined to ,1.6 to ,1.8 MPa in all treatments; turgor was lost sooner when droughted plants were grown under ambient CO2. A 4°C increase in mean air temperature had no effect on ,s in droughted plants, but elicited a small increase in ,l; midday gl values were lower under elevated than under ambient CO2, and ,l and gl declined below ,1.5 MPa and 0.25 cm s,1, respectively, as the soil dried. Despite the low gl values recorded for droughted plants late in the season, Pn was maintained under elevated CO2, but declined to zero 3 weeks before final harvest under ambient CO2. Concurrent reductions in gl and increases in water use efficiency under elevated CO2 prolonged photosynthetic activity during drought and increased pod yields relative to plants grown under ambient CO2. The implications of future increases in atmospheric CO2 for the productivity of indeterminate C3 crops grown in rainfed subsistence agricultural systems in the semi-arid tropics are discussed. [source] Does avian species richness in natural patch mosaics follow the forest fragmentation paradigm?ANIMAL CONSERVATION, Issue 1 2007D. C. Pavlacky Jr. Abstract As one approaches the north-eastern limit of pinyon (Pinus spp.) juniper (Juniperus spp.) vegetation on the Colorado Plateau, USA, woodland patches become increasingly disjunct, grading into sagebrush (Artemisia spp.)-dominated landscapes. Patterns of avian species richness in naturally heterogeneous forests may or may not respond to patch discontinuity in the same manner as bird assemblages in fragmented agricultural systems. We used observational data from naturally patchy woodlands and predictions derived from studies of human-modified agricultural forests to estimate the effects of patch area, shape, isolation and distance to contiguous woodland on avian species richness. We predicted that patterns of species richness in naturally patchy juniper woodlands would differ from those observed in fragmented agricultural systems. Our objectives were to (1) estimate the effect of naturally occurring patch structure on avian species richness with respect to habitat affinity and migratory strategy and (2) assess the concordance of the effects to predictions from agricultural forest systems. We used the analogy between populations and communities to estimate species richness, where species are treated as individuals in the application of traditional capture,recapture theory. Information-theoretic model selection showed that overall species richness was explained primarily by the species area relationship. There was some support for a model with greater complexity than the equilibrium theory of island biogeography where the isolation of large patches resulted in greater species richness. Species richness of woodland-dwelling birds was best explained by the equilibrium hypothesis with partial landscape complementation by open-country species in isolated patches. Species richness within specific migratory strategies showed concomitant increases and no shifts in species composition along the patch area gradient. Our results indicate that many patterns of species richness considered to be fragmentation effects may be general consequences of patch discontinuity and are ubiquitous in naturally heterogeneous systems. There was no evidence for the effects of patch shape and distance to contiguous woodland in juniper woodland, suggesting edge effects and dependence upon regional species pools are characteristics of fragmented agricultural systems. Natural patch mosaics may provide benchmarks for evaluating fragmentation effects and managing forests by mimicking natural landscape patterns. [source] Environmental change and adaptation in degraded agro-ecosystems: the case of highland MadagascarAREA, Issue 3 2010Jon Unruh While the view that the poorer agricultural populations in developing countries will be at the forefront of negative consequences due to environmental change is widely accepted, this perspective must become considerably more nuanced in order to recognise and take advantage of emerging opportunities for realistic adaptation. This paper presents a case from Madagascar that suggests adaptation opportunities involve more than looking for alternatives to what are presently perceived to be negative socio-ecologic processes. In Madagascar the severe erosion occurring on the deforested central plateau actually appears to create, over time, opportunities for increased food security and environmental management compared with uneroded portions of the same landscape. The paper proposes that while concern and action are needed to attend to the problems that the poor of the developing world will face due to impacts from environmental change, the repercussions of such change on agricultural systems also need to be looked at in ways that involve recognising the local and aggregate potential opportunities that they may present in certain systems, in order to realise the prospects for adaptation. [source] Do virus-resistant plants pose a threat to non-target ecosystems?AUSTRAL ECOLOGY, Issue 5 2009Abstract It has been widely argued that the acquisition of novel disease resistance genes by wild host populations following the release of novel pathogen-resistant plants into agricultural systems could pose a significant threat to non-target plant communities. However, predicting the magnitude of ecological release in wild plant populations following the removal of disease remains a major challenge. In this paper we report on the second phase of a tiered risk assessment designed to investigate the role of disease on host growth, survival, fecundity and fitness in a model pathosystem (the pasture species Trifolium repens infected with Clover yellow vein virus, ClYVV) and to assess the level of risk posed to at-risk native plant communities in southeast Australia by newly developed genetically modified and conventionally bred virus-resistant T. repens genotypes. Multi-year field experiments conducted in woodland and grassland environments using host-pathogen arrays derived from 14 ClYVV isolates and 21 T. repens genotypes indicate that viral infection reduces fecundity, growth and survival of wild T. repens plants but that the severity of these effects depends on host tolerance to infection, isolate aggressiveness and specific spatial and temporal environmental conditions. Demographic modelling showed that by reducing host survival and growth, ClYVV also limits the intrinsic population growth rate and niche size of wild T. repens populations. Given the significant fitness cost associated with viral infection we conclude that virus-resistant T. repens genotypes may pose a threat to some high conservation-value non-target ecosystems in SE Australia. We also argue that long-term, multi-tiered experiments conducted in a range of controlled and non-controlled environments are necessary to detect and accurately quantify risks associated with the release of disease-resistant plants in general. [source] | ||||||||||||||||||||||||||||||||||