Perennial grasslands enhance biodiversity and multiple ecosystem services in bioenergy landscapes

Agriculture is being challenged to provide food, and increasingly fuel, for an expanding global population. Producing bioenergy crops on marginal lands—farmland suboptimal for food crops—could help meet energy goals while minimizing competition with food production. However, the ecological costs and benefits of growing bioenergy feedstocks—primarily annual grain crops—on marginal lands have been questioned. Here we show that perennial bioenergy crops provide an alternative to annual grains that increases biodiversity of multiple taxa and sustain a variety of ecosystem functions, promoting the creation of multifunctional agricultural landscapes. We found that switchgrass and prairie plantings harbored significantly greater plant, methanotrophic bacteria, arthropod, and bird diversity than maize. Although biomass production was greater in maize, all other ecosystem services, including methane consumption, pest suppression, pollination, and conservation of grassland birds, were higher in perennial grasslands. Moreover, we found that the linkage between biodiversity and ecosystem services is dependent not only on the choice of bioenergy crop but also on its location relative to other habitats, with local landscape context as important as crop choice in determining provision of some services. Our study suggests that bioenergy policy that supports coordinated land use can diversify agricultural landscapes and sustain multiple critical ecosystem services.In agricultural landscapes, balancing the provisioning of food and energy with maintenance of biodiversity and ecosystem functions is a global challenge. To avoid impacts on food production, attention is increasingly being focused on the potential for marginal lands to support bioenergy production (1). Marginal lands, those suboptimal for food production, may consist of relatively small areas within generally productive landscapes or larger regions where conditions generally limit crop productivity. However, there is increasing recognition that these lands are already performing a variety of useful functions, and their conversion to bioenergy cropping could reduce these services. For example, in the north central United States, rising commodity prices are predicted to bring marginal croplands—including Conservation Reserve Program lands—into annual crop production with negative impacts on wildlife habitat and water quality (2, 3). With 2013 corn plantings at recent record highs (4) and new reports of grassland and wetland conversion to cropland (5, 6), this may be occurring already.An alternative to annual cropping is conversion of marginal croplands to perennial, cellulosic crops for bioenergy. Although current US biofuel production centers on grain ethanol derived from annual monocultures of maize (Zea mays), this situation could change with full implementation of the 2007 US Energy Independence and Security Act (7), which calls for increased production of cellulosic biofuels. In the Midwest United States, perennial grasses and forbs grown on marginal lands could provide up to 25% of national targets for cellulosic biofuel, with substantial greenhouse gas (GHG) benefits (8). Moreover, increasing the area of perennial cover on the landscape is predicted to positively affect a diverse array of organisms and ecological functions (9–11), leading to important synergies that have not yet informed the ongoing bioenergy debate. Here we provide the most comprehensive empirical evaluation of this hypothesis to date, reporting data that elucidate the impacts of different bioenergy cropping systems on a wide variety of organisms and the ecosystem functions they perform.Previous studies have examined the ability of select bioenergy crops to support specific taxa (12) or individual services such as energy production (13) or GHG mitigation (14), without consideration of the tradeoffs or synergies that can arise when considering entire suites of organisms and ecosystem functions. We report on a unique multidisciplinary study of matched sets of organisms and ecosystem services and show that perennial grass energy crops (switchgrass, Panicum virgatum, and mixed prairie plantings) synergistically enhance diversity of a variety of organisms and levels of the services they provide. We further quantify the importance of landscape context on service provisioning, suggesting that policy supporting intentional design of bioenergy landscapes could increase sustainability of both food and energy production.     

A non-linear optimal greenhouse control problem with heating and ventilation

A simplified non-linear dynamic model of greenhouse crop growth with constraints on the state and the control signal is considered. The weather is assumed to be known. The optimization criterion is to minimize the heating and ventilation cost. In this paper a novel solution is presented for the case when both the heating cost and the ventilation cost are included in the criterion. Important properties of the optimal solutions are clarified. It is found that neighbouring maxima and minima of a particular function of the outside temperature, the solar radiation and the heat transfer coefficient decide whether heating or ventilation has to be applied. A numerical example is given.     

The importance of hydrology in routing terrestrial carbon to the atmosphere via global streams and rivers

The magnitude of stream and river carbon dioxide (CO₂) emission is affected by seasonal changes in watershed biogeochemistry and hydrology. Global estimates of this flux are, however, uncertain, relying on calculated values for CO₂ and lacking spatial accuracy or seasonal variations critical for understanding macroecosystem controls of the flux. Here, we compiled 5,910 direct measurements of fluvial CO₂ partial pressure and modeled them against watershed properties to resolve reach-scale monthly variations of the flux. The direct measurements were then combined with seasonally resolved gas transfer velocity and river surface area estimates from a recent global hydrography dataset to constrain the flux at the monthly scale. Globally, fluvial CO₂ emission varies between 112 and 209 Tg of carbon per month. The monthly flux varies much more in Arctic and northern temperate rivers than in tropical and southern temperate rivers (coefficient of variation: 46 to 95 vs. 6 to 12%). Annual fluvial CO₂ emission to terrestrial gross primary production (GPP) ratio is highly variable across regions, ranging from negligible (<0.2%) to 18%. Nonlinear regressions suggest a saturating increase in GPP and a nonsaturating, steeper increase in fluvial CO₂ emission with discharge across regions, which leads to higher percentages of GPP being shunted into rivers for evasion in wetter regions. This highlights the importance of hydrology, in particular water throughput, in routing terrestrial carbon to the atmosphere via the global drainage networks. Our results suggest the need to account for the differential hydrological responses of terrestrial–atmospheric vs. fluvial–atmospheric carbon exchanges in plumbing the terrestrial carbon budget.

The Earth’s water, carbon, and energy fluxes follow seasonal variations in the Earth’s solar radiation and climate variability (1, 2). As an integral part of terrestrial landscapes, streams and rivers receive significant water and carbon inputs from terrestrial and wetland ecosystems, which are further processed along the river to ocean continuum (3). As the largest carbon flux mediated by fluvial systems, carbon dioxide (CO₂) emission from stream and river surfaces (4–7) is double the lateral carbon transport to oceans (8), yet its spatial and temporal variations are not fully resolved. Stream and river CO₂ evasion changes considerably across space and time due to biogeochemical responses to climatic factors (3), the physics governing the transfer of gas across the water–air interface (9), and seasonal variations in the spatial extent of drainage networks (10, 11). However, seasonal variability of the flux has not been determined at the global scale, limiting our ability to understand controls at the macrosystem level.The rate at which streams and rivers exchange CO₂ with the atmosphere is determined by three factors: dissolved CO₂ concentration (often expressed as an equivalent atmospheric partial pressure [pCO₂]), water surface gas transfer velocity (k), and water surface area. To estimate flux at the monthly scale, all three factors need to be resolved at the same or finer temporal scale(s). To date, existing spatially explicit estimates of riverine CO₂ emission at the global scale (4, 12) relied exclusively on pCO₂ calculated from carbonate equilibria and historical archives of pH and alkalinity measurements. While these data have reasonable spatial coverage, the carbonate equilibria method is subject to inflated pCO₂ estimates due to biased pH measurements (13) and alkalinity contribution from organic acids (14), particularly in low–ionic strength waters. These errors, although reducible within individual datasets (15), are difficult to correct for when scaling globally. This problem has significantly undermined calculations and understanding of the flux at the global scale. More importantly, although global estimates of the stream and river surface area and gas transfer velocity at mean annual discharge have been achieved (4, 16), their seasonal extent, a major driver of within-year variability of riverine CO₂ flux, has not. This is largely because a temporally resolved reach-scale representation of global river hydrology has not been available until recently (17), and new understandings of aquatic surface area extent and water–air gas transfer rates are necessary to incorporate temporal variability into the riverine CO₂ flux estimate.We compiled a dataset of present-day direct pCO₂ measurements in global streams and rivers from the literature. The dataset has 5,910 individual measurements of different months that cover all major freshwater ecoregions of the world (18), despite a small percentage (∼0.5%) of measurements from southern temperate rivers (SI Appendix, Fig. S1). The dataset further has pCO₂ measurements in all months from each freshwater ecoregion (open water months for the polar freshwater ecoregion) except oceanic islands and large river deltas that make up only 0.4% of the global land area (SI Appendix, Fig. S1). These observations allowed for robust validation of the study’s results. Riverine pCO₂ was statistically modeled against a set of watershed properties (SI Appendix, Table S1) in order to understand biogeochemical and geophysical controls on pCO₂. Predictions of pCO₂, k, and surface area were based on a new representation of the global river networks (the Global Reach-Level A Priori Discharge Estimates for Surface Water and Ocean Topography [GRADES] river networks) (17), which contains daily discharge estimates at ∼3 million individual river reaches over a 35-y period. Monthly CO₂ flux estimates were achieved by coupling monthly pCO₂ estimates driven by monthly watershed properties to monthly k and surface area estimates driven by the GRADES discharge. Spatial and temporal variability of the flux was finally investigated to demonstrate a strong modulation of the terrestrial (and wetland) carbon routing to the atmosphere via streams and rivers by hydrology.     

Prevalence and risk factors for MSDs in vegetable greenhouse farmers: a cross-sectional survey from Shandong rural area,China

Purpose: The aim of the research is a cross sectional survey on the prevalence of symptoms related to MSDs in vegetable greenhouse farmers from Shandong rural area and on the risk factors that may influence it. Methods: This cross-sectional survey was selected 249 farmers working in vegetable greenhouse from different districts of Shandong Province, China. The Questionnaire and the Rapid Upper Limb Assessment (RULA) technique were used to identify ergonomic risks. χ² analysis was used to find the relationship between MSDs and various factors. Also, logistic regression methodology was applied to get the most influencing factor for MSDs. Results: The prevalence of MSDs in farmers working in vegetable greenhouse is 87.5%, and the top 3 prevalent areas of MSDs in various parts of the body are: lower back (47.4%), neck (33.3%), and shoulder (31.7%). The results of Logistic regression analysis showed that age, years working in vegetable greenhouses, keeping their backs in the same position for a long time, and working hours greater than 10 hours per day were the risk factors for MSDs in the farmers. The outcome of the RULA grand score had been found to be higher than 5 in the overwhelming majority of the farmers. Conclusions: All findings infer that each task of greenhouse vegetable growing inflicts different levels of disorder in a farmers’ musculoskeletal structure. Interventions should be increased and reduce the bad ergonomic load level as soon as possible, provided to reduce the impact of such disorders.     

温室作业农药暴露对新生儿出生质量的影响

目的了解温室作业这部分特殊人群长期多种农药暴露对新生儿出生质量的影响。方法随机抽取2010年3月-2014年12月期间在潍坊市妇幼保健院等3家单位产科生育住院,在孕前及孕期累计且连续从事温室作业至少2年以上的孕妇439人及其孕产的新生儿431人纳入暴露组,不从事温室作业并且不接触农药的同医院产妇152人及其孕产的新生儿151人为对照组。通过问卷调查和查阅资料等方式获得从事大棚种植女性菜农的农药暴露情况、产妇一般情况等,通过现场调查和历史常规资料分析获得新生儿出生质量资料。根据累积农药暴露指数将蔬菜大棚种植组所有被调查者按暴露水平分为低、中、高暴露三个组。结果新生儿男女性别比是1.09∶1,胎龄(39.46±0.28)周,出生体重平均(3.06±0.86)kg,各项体格发育指标如身高、头围、胸围等均在正常值范围内。临床Agpar评分,1 min评分7分占89.52%,5min评分7分占92.61%,10min评分7分占95.36%。亚健康出生儿103名(占17.70%)、出生缺陷儿7名(占1.89%)。不同农药暴露组之间新生儿胎龄、出生体重、身长、Agpar评分、亚健康儿的差异具有统计学意义,并且对照组和高暴露组之间比较亦具有统计学差异。结论温室作业农药暴露可以引发早产、低出生体重儿、身长和Agpar评分降低等生殖健康损伤以及可能增加后代先天性畸形的风险。     

Adapting agriculture to climate change

The strong trends in climate change already evident, the likelihood of further changes occurring, and the increasing scale of potential climate impacts give urgency to addressing agricultural adaptation more coherently. There are many potential adaptation options available for marginal change of existing agricultural systems, often variations of existing climate risk management. We show that implementation of these options is likely to have substantial benefits under moderate climate change for some cropping systems. However, there are limits to their effectiveness under more severe climate changes. Hence, more systemic changes in resource allocation need to be considered, such as targeted diversification of production systems and livelihoods. We argue that achieving increased adaptation action will necessitate integration of climate change-related issues with other risk factors, such as climate variability and market risk, and with other policy domains, such as sustainable development. Dealing with the many barriers to effective adaptation will require a comprehensive and dynamic policy approach covering a range of scales and issues, for example, from the understanding by farmers of change in risk profiles to the establishment of efficient markets that facilitate response strategies. Science, too, has to adapt. Multidisciplinary problems require multidisciplinary solutions, i.e., a focus on integrated rather than disciplinary science and a strengthening of the interface with decision makers. A crucial component of this approach is the implementation of adaptation assessment frameworks that are relevant, robust, and easily operated by all stakeholders, practitioners, policymakers, and scientists.     

Risk of natural disturbances makes future contribution of Canada's forests to the global carbon cycle highly uncertain

A large carbon sink in northern land surfaces inferred from global carbon cycle inversion models led to concerns during Kyoto Protocol negotiations that countries might be able to avoid efforts to reduce fossil fuel emissions by claiming large sinks in their managed forests. The greenhouse gas balance of Canada's managed forest is strongly affected by naturally occurring fire with high interannual variability in the area burned and by cyclical insect outbreaks. Taking these stochastic future disturbances into account, we used the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) to project that the managed forests of Canada could be a source of between 30 and 245 Mt CO(2)e yr(-1) during the first Kyoto Protocol commitment period (2008-2012). The recent transition from sink to source is the result of large insect outbreaks. The wide range in the predicted greenhouse gas balance (215 Mt CO(2)e yr(-1)) is equivalent to nearly 30% of Canada's emissions in 2005. The increasing impact of natural disturbances, the two major insect outbreaks, and the Kyoto Protocol accounting rules all contributed to Canada's decision not to elect forest management. In Canada, future efforts to influence the carbon balance through forest management could be overwhelmed by natural disturbances. Similar circumstances may arise elsewhere if global change increases natural disturbance rates. Future climate mitigation agreements that do not account for and protect against the impacts of natural disturbances, for example, by accounting for forest management benefits relative to baselines, will fail to encourage changes in forest management aimed at mitigating climate change.     

Effects of land use history and inoculation with <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">cucumberinum</Emphasis> Owen on soil nematodes communities

Summary  A pot culture experiment was carried out to study the effects of land use history and inoculation with Fusarium oxysporum f. sp. cucumberinum Owen (Foc) on soil nematodes communities during the cucumber growing season in 2007. The results showed that land use history and inoculation had significant effects on the abundance and diversity of soil nematodes. Bacterivores were found to be the most dominant group in this study. Irrespective of inoculation, numbers of fungivores, plant-parasites and values of trophic diversity index (TD) and plant-parasites index (PPI) were greater in greenhouse soils (GH) than in open field vegetable soils (OF) during the growth period of cucumber. While, the number of omnivores-predators and values of richness (SR) and maturity index (MI) presented an opposite trend. Foc inoculation had noticeable effects on numbers of plant-parasites and some taxa, such as Helicotylenchus, Epidorlaimus at flowering stage and Aphelenchus, Tobrilus at fruiting stage. Besides, inoculation significantly affected values of PPI at flowering stage and TD at fruiting stage, respectively. The faunal analysis showed that soil food web in GH was highly disturbed and in OF was degraded.     

大棚肺308例临床特征分析

目的探讨大棚作业农民肺(简称大棚肺)的临床特征及影像学特点,减少误诊率。方法采用整群随机抽样方法,对2006年8月至2009年6月沈阳市、新民市、朝阳市及锦州市郊区从事塑料大棚作业的5880例农民进行流行病学调查及肺功能检测,共筛查出大棚肺患者308例,分析其临床表现、体征及影像学特点。结果 (1)308例大棚肺患者临床症状按出现的频率高低分别为咳嗽和(或)咳痰192例(62.34%)、发热和寒战180例(58.44%)、胸闷和(或)气急160例(51.95%)、乏力和体重减轻116例(37.66%)、头晕头痛40例(12.99%);(2)两下肺闻及捻发音为大棚肺患者中的主要体征;(3)153例(49.67%)出现X线胸片改变,高分辨CT显示弥漫微小结节影63例(41.18%)、斑片状磨玻璃样阴影48例(31.37%)、结节状磨玻璃样影36例(23.53%)、局限性空气残留并形成"马赛克"样灌注12例(9.15%)、纤维索条影10例(6.54%)、纤维化2例(1.31%);(4)肺外疾病:出现颈项痛及腰腿酸痛169例、关节炎及关节畸形者116例、过敏性皮肤病96例、静脉曲张37例、消化道疾病32例、眼病(包括急性结膜炎、眼缘炎、过敏性结膜炎等)24例。结论大棚肺的早期临床表现变化迅速、非特异性;大棚肺常合并肺外多系统疾病;根据病程的长短,其肺部影像学特点不同。     

Trading carbon for food: global comparison of carbon stocks vs. crop yields on agricultural land

Expanding croplands to meet the needs of a growing population, changing diets, and biofuel production comes at the cost of reduced carbon stocks in natural vegetation and soils. Here, we present a spatially explicit global analysis of tradeoffs between carbon stocks and current crop yields. The difference among regions is striking. For example, for each unit of land cleared, the tropics lose nearly two times as much carbon (～120 tons·ha(-1) vs. ～63 tons·ha(-1)) and produce less than one-half the annual crop yield compared with temperate regions (1.71 tons·ha(-1)·y(-1) vs. 3.84 tons·ha(-1)·y(-1)). Therefore, newly cleared land in the tropics releases nearly 3 tons of carbon for every 1 ton of annual crop yield compared with a similar area cleared in the temperate zone. By factoring crop yield into the analysis, we specify the tradeoff between carbon stocks and crops for all areas where crops are currently grown and thereby, substantially enhance the spatial resolution relative to previous regional estimates. Particularly in the tropics, emphasis should be placed on increasing yields on existing croplands rather than clearing new lands. Our high-resolution approach can be used to determine the net effect of local land use decisions.