Exploitation of endophytes for sustainable agricultural intensification

Intensive agriculture, which depends on unsustainable levels of agrochemical inputs, is environmentally harmful, and the expansion of these practices to meet future needs is not economically feasible. Other options should be considered to meet the global food security challenge. The plant microbiome has been linked to improved plant productivity and, in this microreview, we consider the endosphere – a subdivision of the plant microbiome. We suggest a new definition of microbial endophyte status, the need for synergy between fungal and bacterial endophyte research efforts, as well as potential strategies for endophyte application to agricultural systems.     

农业可持续集约化评价的研究进展与展望

农业可持续集约化是保障全球粮食安全,应对饥荒、贫困和气候变化的现实路径。本文采用文献资料法、归纳演绎法等,探索性构建了农业可持续集约化的研究框架,并从概念源起、指标体系、研究尺度和评价方法4个方面系统回顾研究进展,进而探讨未来发展路径,以期为深化多学科交叉视角下的农业可持续集约化评价及其相关研究提供参考。国际上农业可持续集约化研究成果多样,基于生产力、经济、环境、社会等多个维度赋予了其丰富内涵。农业可持续集约化评价涉及生产力、经济、环境、人类和社会等多个方面,形成了包括物质投入、资源生产率、环境经济效率等多元指标的综合评价体系。评价方法主要包括要素综合评价法和指数模型评价法两类。国内相关研究相对较少,有待进一步丰富,未来应突破传统理论方法框架的约束,瞄准国际发展所带来的变革性科学议题,探索多学科交叉融合下的农业可持续集约化研究范式。     

Sustainable intensification in agricultural systems

BackgroundAgricultural systems are amended ecosystems with a variety of properties. Modern agroecosystems have tended towards high through-flow systems, with energy supplied by fossil fuels directed out of the system (either deliberately for harvests or accidentally through side effects). In the coming decades, resource constraints over water, soil, biodiversity and land will affect agricultural systems. Sustainable agroecosystems are those tending to have a positive impact on natural, social and human capital, while unsustainable systems feed back to deplete these assets, leaving fewer for the future. Sustainable intensification (SI) is defined as a process or system where agricultural yields are increased without adverse environmental impact and without the conversion of additional non-agricultural land. The concept does not articulate or privilege any particular vision or method of agricultural production. Rather, it emphasizes ends rather than means, and does not pre-determine technologies, species mix or particular design components. The combination of the terms ‘sustainable’ and ‘intensification’ is an attempt to indicate that desirable outcomes around both more food and improved environmental goods and services could be achieved by a variety of means. Nonetheless, it remains controversial to some.

Scope and Conclusions

This review analyses recent evidence of the impacts of SI in both developing and industrialized countries, and demonstrates that both yield and natural capital dividends can occur. The review begins with analysis of the emergence of combined agricultural–environmental systems, the environmental and social outcomes of recent agricultural revolutions, and analyses the challenges for food production this century as populations grow and consumption patterns change. Emergent criticisms are highlighted, and the positive impacts of SI on food outputs and renewable capital assets detailed. It concludes with observations on policies and incentives necessary for the wider adoption of SI, and indicates how SI could both promote transitions towards greener economies as well as benefit from progress in other sectors.     

Ecological degradation and agricultural intensification in the Andean highlands

Andean cultural ecologists have made two claims in recent years: ecological decomposition is absent due to effective indigenous management of communal resources, and agricultural intensification is inversely related to altitude. Drawing on material from the Jukumani Indians of Northern Potosi, Bolivia, these assertions are challenged. First, there is little evidence to prove or disprove ecological degradation. Second, the location of agricultural intensification, as the Jukumani data suggests, is influenced by altitude as well as by the presence of market.Fieldwork in Bolivia was carried out between January 1979 and May 1981. This essay was originally presented at a conference entitled, How Communities Resolve Common Property Problems, sponsored by the Harvard Institute for International Development and the Center for Population Studies of Harvard University in the spring semester of 1983.     

Arthropod biodiversity in olive groves under two soil management systems: presence versus absence of herbaceous cover crop

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Comparative landscape genetics of two frugivorous bats in a biological corridor undergoing agricultural intensification

Agricultural intensification in tropical landscapes poses a new threat to the ability of biological corridors to maintain functional connectivity for native species. We use a landscape genetics approach to evaluate impacts of expanding pineapple plantations on two widespread and abundant frugivorous bats in a biological corridor in Costa Rica. We hypothesize that the larger, more mobile Artibeus jamaicensis will be less impacted by pineapple than the smaller Carollia castanea. In 2012 and 2013, we sampled 735 bats in 26 remnant forest patches surrounded by different proportions of forest, pasture, crops and pineapple. We used 10 microsatellite loci for A. jamaicensis and 16 microsatellite loci for C. castanea to estimate genetic diversity and gene flow. Canonical correspondence analyses indicate that land cover type surrounding patches has no impact on genetic diversity of A. jamaicensis. However, for C. castanea, both percentage forest and pineapple surrounding patches explained a significant proportion of the variation in genetic diversity. Least‐cost transect analyses (LCTA) and pairwise G″st suggest that for A. jamaicensis, pineapple is more permeable to gene flow than expected, while as expected, forest is the most permeable land cover for gene flow of C. castanea. For both species, LCTA indicate that development may play a role in inhibiting gene flow. The current study answers the call for landscape genetic research focused on tropical and agricultural landscapes, highlights the value of comparative landscape genetics in biological corridor design and management and is one of the few studies of biological corridors in any ecosystem to implement a genetic approach to test corridor efficacy.     

气候变化下旱区农业生态系统的可持续性

农业生产是将自然资源不断转化为农产品的过程.简单的说就是将阳光、空气、水和土壤等无机资源转化为可以供人类消费的有机产物.农业生态系统必须对全球气候变化、市场竞争、自然环境的恶化、经济等政策法规和人民的需求等因素做出灵活的应对策略,同时还要保证自然生态系统的稳定性.在发展中国家,有超过20 亿的人口每天收入低于2 美元,他们收入中绝大部分都用于解决温饱.这些人大部分生活在干旱、半干旱地区,并以农业生产作为生活的主要来源.由于这些地区水资源匮乏、土壤贫瘠,粮食安全问题一直是该地区人类生存的关键.中澳两国都把干旱、半干旱地区的农牧业发展作为研究的重点.两国的专家都致力于恢复和维护干旱半干旱地区脆弱的农业生态系统.气候变化正在使农业生态系统可持续发展面临严峻挑战.因此,迫切需要农学,生态学,环境学,社会经济学等多学科的共同发展和融合解决这一问题.     

Soil oribatid mite communities under three species of legumes in an ultisol in Brazil

Oribatid mite densities in the topsoil and their activity at the soil surface were monitored under three species of perennial legume cover crops namely, Arachis pintoi, Macroptilium atropupureum and Pueraria phaseoloides, grass (Panicum maximum) and bare plots on three occasions in 1998 and 1999 in a derived savanna zone in Brazil. Both densities and activity at the soil surface were higher in the early but cool dry season in April 1998 than in the early wet but warm season in November 1998 and 1999. Three taxonomic groups of macropyline oribatid mites, namely Nothrus, Archegozetes and Masthermannia as well as a brachypyline taxon, Scheloribates were suggested as possible indicators of effect of legumes on soil biota because their populations increased under the legumes and/or their residues. Nothrus in particular increased in abundance more than any other taxon in the presence of residues of A. pintoi. Each legume supported a unique oribatid mite community in terms of species composition and relative abundance. The large numbers of Archegozetes trapped from all the legume and grass plots in April and November 1998 were also attributed to highly conducive conditions provided by the vegetation cover and their residues. The results suggest that the oribatid mite community of the study area was numerically stable as the peak populations of different species were not synchronized. Many taxonomic groups of pycnonotic brachypyline mites were absent. Legume cover crops, especially A. pintoi, and their residues have potential in restoring oribatid mite populations to precultivation levels. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pasture intensification is insufficient to relieve pressure on conservation priority areas in open agricultural markets

Agricultural expansion is a leading driver of biodiversity loss across the world, but little is known on how future land‐use change may encroach on remaining natural vegetation. This uncertainty is, in part, due to unknown levels of future agricultural intensification and international trade. Using an economic land‐use model, we assessed potential future losses of natural vegetation with a focus on how these may threaten biodiversity hotspots and intact forest landscapes. We analysed agricultural expansion under proactive and reactive biodiversity protection scenarios, and for different rates of pasture intensification. We found growing food demand to lead to a significant expansion of cropland at the expense of pastures and natural vegetation. In our reference scenario, global cropland area increased by more than 400 Mha between 2015 and 2050, mostly in Africa and Latin America. Grazing intensification was a main determinant of future land‐use change. In Africa, higher rates of pasture intensification resulted in smaller losses of natural vegetation, and reduced pressure on biodiversity hotspots and intact forest landscapes. Investments into raising pasture productivity in conjunction with proactive land‐use planning appear essential in Africa to reduce further losses of areas with high conservation value. In Latin America, in contrast, higher pasture productivity resulted in increased livestock exports, highlighting that unchecked trade can reduce the land savings of pasture intensification. Reactive protection of sensitive areas significantly reduced the conversion of natural ecosystems in Latin America. We conclude that protection strategies need to adapt to region‐specific trade positions. In regions with a high involvement in international trade, area‐based conservation measures should be preferred over strategies aimed at increasing pasture productivity, which by themselves might not be sufficient to protect biodiversity effectively.     

EAM会议专刊辑述评——气候变化下旱区农业生态系统的可持续性

农业生产是将自然资源不断转化为农产品的过程。简单的说就是将阳光、空气、水和土壤等无机资源转化为可以供人类消费的有机产物。农业生态系统必须对全球气候变化、市场竞争、自然环境的恶化、经济等政策法规和人民的需求等因素做出灵活的应对策略,同时还要保证自然生态系统的稳定性。在发展中国家,有超过20亿的人口每天收入低于2美元,他们收入中绝大部分都用于解决温饱。这些人大部分生活在干旱、半干旱地区,并以农业生产作为生活的主要来源。由于这些地区水资源匮乏、土壤贫瘠,粮食安全问题一直是该地区人类生存的关键。中澳两国都把干旱、半干旱地区的农牧业发展作为研究的重点。两国的专家都致力于恢复和维护干旱半干旱地区脆弱的农业生态系统。气候变化正在使农业生态系统可持续发展面临严峻挑战。因此,迫切需要农学,生态学,环境学,社会经济学等多学科的共同发展和融合解决这一问题。2010年7月20—25日在兰州大学举办了以“气候变化和旱区农业生态系统管理”为主题的“第二届生态系统评估与管理（EAM）国际会议”。国内外众多知名专家参与了此次会议,并共同讨论在全球气候变化背景下如何提高干旱半干旱地区脆弱农业生态系统生产力与可持续性。本次会议的议题是：(1）半干旱地区旱作雨养农业生态系统评估与管理,(2）干旱地区绿洲农业生态系统评估与管理。此次会议由兰州大学和澳大利亚西澳大学联合主办,中国科学院生态环境研究中心协办,由国家教育部和国家外专局联合支持、兰州大学干旱与草地生态教育部重点实验室承担的“旱寒生态学”学科创新引智基地和西澳大学农业研究院、FAO属下的叙利亚国际旱地农业研究中心(ICARDA)联合提供资金支持。会议期间,25位专家就干旱、半干旱地区植物土壤互作关系作了报告。另外还有18位在干旱半干旱地区科研一线工作的青年学者汇报了研究进展,并与专家进行了广泛交流。报告会之后,大会组织专家分别对典型旱区农业进行了考察,分别是兰州大学黄土高原旱地农业生态实验站(榆中)和甘肃武威市民勤绿洲农业生态系统。此次大会遴选出35篇学术论文,以专刊的形式发表于《生态学报》第31卷第9期。会议遴选出的其它英文文章将于2011年在《Plant and Soil》和《Crop and Pasture Science》上发表,敬请期待。我们相信,本专刊的出版将会对气候变化背景下旱区农业生态系统的研究和发展产生重要的推动作用。     

Land-use intensification systematically alters the size structure of aquatic communities in the Neotropics

Land-use and land-cover transitions can affect biodiversity and ecosystem functioning in a myriad of ways, including how energy is transferred within food-webs. Size spectra (i.e. relationships between body size and biomass or abundance) provide a means to assess how food-webs respond to environmental stressors by depicting how energy is transferred from small to larger organisms. Here, we investigated changes in the size spectrum of aquatic macroinvertebrates along a broad land-use intensification gradient (from Atlantic Forest to mechanized agriculture) in 30 Brazilian streams. We expected to find a steeper size spectrum slope and lower total biomass in more disturbed streams due to higher energetic expenditure in physiologically stressful conditions, which has a disproportionate impact on large individuals. As expected, we found that more disturbed streams had fewer small organisms than pristine forest streams, but, surprisingly, they had shallower size spectrum slopes, which indicates that energy might be transferred more efficiently in disturbed streams. Disturbed streams were also less taxonomically diverse, suggesting that the potentially higher energy transfer in these webs might be channelled via a few efficient trophic links. However, because total biomass was higher in pristine streams, these sites still supported a greater number of larger organisms and longer food chains (i.e. larger size range). Our results indicate that land-use intensification decreases ecosystem stability and enhances vulnerability to population extinctions by reducing the possible energetic pathways while enhancing efficiency between the remaining food-web linkages. Our study represents a step forward in understanding how land-use intensification affects trophic interactions and ecosystem functioning in aquatic systems.     

Strategies and models for agricultural sustainability in developing Asian countries

The green revolution of the 1960s and 1970s which resulted in dramatic yield increases in the developing Asian countries is now showing signs of fatigue in productivity gains. Intensive agriculture practiced without adherence to the scientific principles and ecological aspects has led to loss of soil health, and depletion of freshwater resources and agrobiodiversity. With progressive diversion of arable land for non-agricultural purposes, the challenge of feeding the growing population without, at the same time, annexing more forestland and depleting the rest of life is indeed daunting. Further, even with food availability through production/procurement, millions of marginal farming, fishing and landless rural families have very low or no access to food due to lack of income-generating livelihoods. Approximately 200 million rural women, children and men in India alone fall in this category. Under these circumstances, the evergreen revolution (pro-nature, pro-poor, pro-women and pro-employment/livelihood oriented ecoagriculture) under varied terms are proposed for achieving productivity in perpetuity. In the proposed 'biovillage paradigm', eco-friendly agriculture is promoted along with on- and non-farm eco-enterprises based on sustainable management of natural resources. Concurrently, the modern ICT-based village knowledge centres provide time- and locale-specific, demand-driven information needed for evergreen revolution and ecotechnologies. With a system of 'farm and marine production by masses', the twin goals of ecoagriculture and eco-livelihoods are addressed. The principles, strategies and models of these are briefly discussed in this paper.     

Changes in soil organic carbon under perennial crops

This study evaluates the dynamics of soil organic carbon (SOC) under perennial crops across the globe. It quantifies the effect of change from annual to perennial crops and the subsequent temporal changes in SOC stocks during the perennial crop cycle. It also presents an empirical model to estimate changes in the SOC content under crops as a function of time, land use, and site characteristics. We used a harmonized global dataset containing paired‐comparison empirical values of SOC and different types of perennial crops (perennial grasses, palms, and woody plants) with different end uses: bioenergy, food, other bio‐products, and short rotation coppice. Salient outcomes include: a 20‐year period encompassing a change from annual to perennial crops led to an average 20% increase in SOC at 0–30 cm (6.0 ± 4.6 Mg/ha gain) and a total 10% increase over the 0–100 cm soil profile (5.7 ± 10.9 Mg/ha). A change from natural pasture to perennial crop decreased SOC stocks by 1% over 0–30 cm (?2.5 ± 4.2 Mg/ha) and 10% over 0–100 cm (?13.6 ± 8.9 Mg/ha). The effect of a land use change from forest to perennial crops did not show significant impacts, probably due to the limited number of plots; but the data indicated that while a 2% increase in SOC was observed at 0–30 cm (16.81 ± 55.1 Mg/ha), a decrease in 24% was observed at 30–100 cm (?40.1 ± 16.8 Mg/ha). Perennial crops generally accumulate SOC through time, especially woody crops; and temperature was the main driver explaining differences in SOC dynamics, followed by crop age, soil bulk density, clay content, and depth. We present empirical evidence showing that the FAO perennialization strategy is reasonable, underscoring the role of perennial crops as a useful component of climate change mitigation strategies.     

Rise of toxic cyanobacterial blooms is promoted by agricultural intensification in the basin of a large subtropical river of South America

Toxic cyanobacterial blooms are globally increasing with negative effects on aquatic ecosystems, water use and human health. Blooms' main driving forces are eutrophication, dam construction, urban waste, replacement of natural vegetation with croplands and climate change and variability. The relative effects of each driver have not still been properly addressed, particularly in large river basins. Here, we performed a historical analysis of cyanobacterial abundance in a large and important ecosystem of South America (Uruguay river, ca 1900 km long, 365,000 km² basin). We evaluated the interannual relationships between cyanobacterial abundance and land use change, river flow, urban sewage, temperature and precipitation from 1963 to the present. Our results indicated an exponential increase in cyanobacterial abundance during the last two decades, congruent with an increase in phosphorus concentration. A sharp shift in the cyanobacterial abundance rate of increase after the year 2000 was identified, resulting in abundance levels above public health alert since 2010. Path analyses showed a strong positive correlation between cyanobacteria and cropland area at the entire catchment level, while precipitation, temperature and water flow effects were negligible. Present results help to identify high nutrient input agricultural practices and nutrient enrichment as the main factors driving toxic bloom formation. These practices are already exerting severe effects on both aquatic ecosystems and human health and projections suggest these trends will be intensified in the future. To avoid further water degradation and health risk for future generations, a large-scale (transboundary) change in agricultural management towards agroecological practices will be required.     

Complexity within an oil palm monoculture: The effects of habitat variability and rainfall on adult dragonfly (Odonata) communities

Recent expansion of oil palm agriculture has resulted in loss of forest habitat and forest-dependent species. However, large numbers of species—particularly insects—can persist within plantations. This study focuses on Odonata (dragonflies and damselflies): a charismatic indicator taxon and a potentially valuable pest control agent. We surveyed adult Odonata populations biannually over three years within an industrial oil palm plantation in Sumatra, Indonesia. We assessed the effects of rainfall (including an El Niño Southern Oscillation-associated drought), the role of roadside ditches, and the importance of understory vegetation on Odonata populations. To assess the impacts of vegetation, we took advantage of a long-term vegetation management experiment that is part of the Biodiversity and Ecosystem Function in Tropical Agriculture (BEFTA) Programme. We found 41 Odonata species, and communities varied between plantation core and roadside edge microhabitats, and between seasons. Abundance was significantly related to rainfall levels four months before surveys, probably indicating the importance of high water levels in roadside ditches for successful larval development. We found no significant effect of the BEFTA understory vegetation treatments on Odonata abundance, and only limited effects on community composition, suggesting that local understory vegetation structure plays a relatively unimportant role in determining communities. Our findings highlight that there are large numbers of Odonata species present within oil palm plantations and suggest that their abundance could potentially be increased by maintaining or establishing waterbodies. As Odonata are predators, this could bring pest control benefits, in addition to enhancing biodiversity within intensive agricultural landscapes.     

Between‐year variations in Little Bustard Tetrax tetrax population densities are influenced by agricultural intensification and rainfall

The Little Bustard is suffering a widespread population decline mainly due to agricultural intensification. This study evaluates the effects of intensification level, habitat availability and rainfall on the population dynamics of this species. The population density of males was monitored for 7 years (2002–2008) at 184 points located within three sites with contrasting levels of agricultural intensification in southern Portugal. Densities decreased along the intensification gradient from 8.2 to 2.3 males / km². Overall, there was an approximately 50% population decline during the period 2002–2008, driven by a decline observed in one of the less intensive sites, whereas in the other two sites densities remained fairly constant. Yearly variations in male densities were influenced by intensification level, amount of grassland habitat and rainfall patterns. Thus, agricultural intensification is having a negative effect on population densities of this threatened species, particularly through the loss of grasslands (fallow fields and pastures) suitable for displaying males. The results also suggest a positive impact of rainfall on male densities, although this is more likely in grasslands within less intensive agricultural regions of poorer soil quality, where higher breeding male densities occur. Grassland habitat quality, driven by both climate and human management, probably plays a major role in the population dynamics of this threatened steppe bird in its strongholds.     

Differences in carbon stocks along an elevational gradient in tropical mountain forests of Colombia

Tropical mountain forests provide an exceptional opportunity to evaluate the patterns of variation in carbon stocks along elevational gradients that correspond to well‐defined temperature gradients. We predicted that carbon stored in live aboveground biomass, aboveground necromass, and soil components of forests on the eastern flank of the Colombian Andes would change with elevation along this gradient extending from 750 to 2,800 m above sea level. The rationale was that the corresponding change in temperature (14–26°C) would influence tree growth and decomposition of organic matter. To address this hypothesis, we examined the carbon stored in these three components using data from 20 0.25‐ha plots located along this elevational gradient. The mean total carbon stock found in the study region was 241.3 ± 37.5 Mg C/ha. Aboveground carbon stocks decreased with elevation (p = 0.001), as did necromass carbon stocks (p = 0.016). Although soil organic carbon stocks did not differ significantly along the gradient (p = 0.153), they contributed proportionately more at higher than at lower elevations, counterbalancing the opposite trends in aboveground carbon and necromass carbon stocks. As such, total carbon stocks did not vary significantly along the elevational gradient (p = 0.576).