• Authors:
    • Chen, J.
    • Burke, J.
  • Source: PLOS ONE
  • Volume: 10
  • Issue: 4
  • Year: 2015
  • Summary: Comparison of average crop yields with reported record yields has shown that major crops exhibit annual average yields three-to seven-fold lower than record yields because of unfavorable environments. The current study investigated the enhancement of pollen heat tolerance through expressing an Arabidopsis thaliana heat shock protein 101 (AtHSP101) that is not normally expressed in pollen but reported to play a crucial role in vegetative thermotolerance. The AtHSP101 construct under the control of the constitutive ocs/mas 'superpromoter' was transformed into cotton Coker 312 and tobacco SRI lines via Agrobacterium mediated transformation. Thermotolerance of pollen was evaluated by in vitro pollen germination studies. Comparing with those of wild type and transgenic null lines, pollen from AtHSP101 transgenic tobacco and cotton lines exhibited significantly higher germination rate and much greater pollen tube elongation under elevated temperatures or after a heat exposure. In addition, significant increases in boll set and seed numbers were also observed in transgenic cotton lines exposed to elevated day and night temperatures in both greenhouse and field studies. The results of this study suggest that enhancing heat tolerance of reproductive tissues in plant holds promise in the development of crops with improved yield production and yield sustainability in unfavorable environments.
  • Authors:
    • Damerau,Kerstin
    • van Vliet,Oscar P. R.
    • Patt,Anthony G.
  • Source: Climatic Change
  • Volume: 130
  • Issue: 2
  • Year: 2015
  • Summary: The Middle East and North Africa (MENA) region stands out globally both for the immensity of its energy resources, and the paucity of its freshwater resources. Most energy extraction and conversion technologies have associated freshwater demand, and in the MENA region these account for 2 % of the available sustainable supply. We examine how this demand could change over the 21st century, assuming growth in population and economic output, and considering three alternative pathways for energy efficiency, carbon intensity, and energy exports from the region. We find that in the pathway marked by improved efficiency, a transition to renewable energy sources, and declining energy exports, water consumption for energy is twice as high as today's values by the end of the century. By contrast, in the pathway marked by continued commitment to fossil resource extraction, use, and export, water demand for energy might rise by a factor of five. If the region were to maintain high levels of energy exports, but would substitute the export of fossil fuels by an equivalent amount of electricity derived from sunlight, a freshwater volume comparable to the household needs of up to 195 million people could be saved.
  • Authors:
    • QiFe, H.
    • Luo GePing
    • Madaminov, A. A.
    • Maisupova, B.
    • Chen, X.
    • Zhang, C.
    • Li, C.
    • Djenbaev, B. M.
  • Source: Primary Research Article
  • Volume: 21
  • Issue: 5
  • Year: 2015
  • Summary: Central Asia has a land area of 5.6*10 6 km 2 and contains 80-90% of the world's temperate deserts. Yet it is one of the least characterized areas in the estimation of the global carbon (C) stock/balance. This study assessed the sizes and spatiotemporal patterns of C pools in Central Asia using both inventory (based on 353 biomass and 284 soil samples) and process-based modeling approaches. The results showed that the C stock in Central Asia was 31.34-34.16 Pg in the top 1-m soil with another 10.42-11.43 Pg stored in deep soil (1-3 m) of the temperate deserts. They amounted to 18-24% of the global C stock in deserts and dry shrublands. The C stock was comparable to that of the neighboring regions in Eurasia or major drylands around the world (e.g. Australia). However, 90% of Central Asia C pool was stored in soil, and the fraction was much higher than in other regions. Compared to hot deserts of the world, the temperate deserts in Central Asia had relatively high soil organic carbon density. The C stock in Central Asia is under threat from dramatic climate change. During a decadal drought between 1998 and 2008, which was possibly related to protracted La Nina episodes, the dryland lost approximately 0.46 Pg C from 1979 to 2011. The largest C losses were found in northern Kazakhstan, where annual precipitation declined at a rate of 90 mm decade -1. The regional C dynamics were mainly determined by changes in the vegetation C pool, and the SOC pool was stable due to the balance between reduced plant-derived C influx and inhibited respiration.
  • Authors:
    • Kanninen, M.
    • Negash, M.
  • Source: Article
  • Volume: 203
  • Year: 2015
  • Summary: The fifth assessment report of the intergovernmental panel on climate change (IPCC) estimated that by 2040 agroforestry would offer high potential of carbon (C) sequestration in developing countries. However, the role of tropical agroforestry in C sequestration and in climate change mitigation has only recently been recognized by United Nations Framework Convention on Climate Change (UNFCCC). This is partly due to the lack of reliable estimates on the sequestration potential in biomass and soil carbon pools over time. The aim of this study was to analyze the changes in the biomass and soil carbon pools of three indigenous agroforestry systems in south-eastern Rift Valley escrapment of Ethiopia using CO2FIX (v. 3.2) model. The agroforestry systems studied were Enset ( Ensete ventricosum)-tree, Enset-coffee-tree, and Tree-coffee systems. To run the model, empirical data collected from 60 farms (20 farms for each agroforestry system) and literature were used as inputs to parameterize the model. Simulations were run over a period of 50 years. Average simulated total biomass C stocks was the highest for Tree-coffee system (122 Mg C ha -1), followed by the Enset-coffee-tree (114 Mg C ha -1) and Enset-tree system (76 Mg C ha -1). The tree cohort accounted for 89-97% of the total biomass C stocks in all the studied systems, and the reminder was shared by Enset and coffee cohorts. The total average simulated total C stocks (biomass and soil) were 209, 286 and 301 Mg C ha -1 for Enset-tree, Enset-coffee-tree and Tree-coffee systems, respectively. The soil organic carbon (SOC) stocks accounted for 60-64% of the total carbon in the studied systems. Model validation results showed that long-term (10-40 years) simulated biomass C stocks were within the range of measured biomass C stocks for Enset-tree and Enset-coffee-tree systems, but significantly differed for the Tree-coffee system. The simulated soil and total C stocks were within the range of measured values for all the three systems. The CO2FIX model accurately predicted the SOC and total C stocks in the studied indigenous agroforestry systems, but the prediction of the biomass C stocks could be improved by acquiring more accurate input parameter values for running the model.
  • Authors:
    • Rubenstein, D.
    • Notenbaert, A.
    • Beringer, T.
    • Thornton, P. K.
    • Estes, L.
    • Searchinger, T. D.
    • Heimlich, R.
    • Licker, R.
    • Herrero, M.
  • Source: Article
  • Volume: 5
  • Issue: 5
  • Year: 2015
  • Summary: Do the wet savannahs and shrublands of Africa provide a large reserve of potential croplands to produce food staples or bioenergy with low carbon and biodiversity costs? We find that only small percentages of these lands have meaningful potential to be low-carbon sources of maize (1/42%) or soybeans (9.5-11.5%), meaning that their conversion would release at least one-third less carbon per ton of crop than released on average for the production of those crops on existing croplands. Factoring in land-use change, less than 1% is likely to produce cellulosic ethanol that would meet European standards for greenhouse gas reductions. Biodiversity effects of converting these lands are also likely to be significant as bird and mammal richness is comparable to that of the world's tropical forest regions. Our findings contrast with influential studies that assume these lands provide a large, low-environmental-cost cropland reserve. © 2015 Macmillan Publishers Limited. All rights reserved.
  • Authors:
    • Wang, E.
    • Luo, Z.
    • King, D.
    • Bryan, B. A.
    • Zhao, G.
    • Yu, Q.
  • Source: GCB Bioenergy
  • Volume: 7
  • Issue: 3
  • Year: 2015
  • Summary: The use of crop residues for bioenergy production needs to be carefully assessed because of the potential negative impact on the level of soil organic carbon (SOC) stocks. The impact varies with environmental conditions and crop management practices and needs to be considered when harvesting the residue for bioenergy productions. Here, we defined the sustainable harvest limits as the maximum rates that do not diminish SOC and quantified sustainable harvest limits for wheat residue across Australia's agricultural lands. We divided the study area into 9432 climate-soil (CS) units and simulated the dynamics of SOC in a continuous wheat cropping system over 122years (1889 - 2010) using the Agricultural Production Systems sIMulator (APSIM). We simulated management practices including six fertilization rates (0, 25, 50, 75, 100, and 200kg Nha(-1)) and five residue harvest rates (0, 25, 50, 75, and 100%). We mapped the sustainable limits for each fertilization rate and assessed the effects of fertilization and three key environmental variables - initial SOC, temperature, and precipitation - on sustainable residue harvest rates. We found that, with up to 75kg Nha(-1) fertilization, up to 75% and 50% of crop residue could be sustainably harvested in south-western and south-eastern Australia, respectively. Higher fertilization rates achieved little further increase in sustainable residue harvest rates. Sustainable residue harvest rates were principally determined by climate and soil conditions, especially the initial SOC content and temperature. We conclude that environmental conditions and management practices should be considered to guide the harvest of crop residue for bioenergy production and thereby reduce greenhouse gas emissions during the life cycle of bioenergy production.
  • Authors:
    • Salahvarzi, Y.
    • Goldani, M.
    • Tehranifar, A.
    • Shour, M.
    • Kamali, M.
  • Source: Journal of Science
  • Volume: 5
  • Issue: 20
  • Year: 2015
  • Summary: High carbon dioxide (CO2) concentration in atmosphere has direct effects on plants activities. In order to investigate the effect of increased CO2 concentration from 380 to 700 and 1050 mg/L on some chemical and physiological characteristics of Amaranthus tricolor under three salinity treatments (0, 150, and 300 mM NaCl), an experiment was conducted in Research Greenhouse of Ferdowsi University of Mashhad, Iran. The results showed that interaction of salinity and CO2 in traits such as total dry weight, electrolyte leakage, relative water content and Na+uptake was significant at 1% probability level. However, interaction of CO2 and salt stress in plant traits such as proline and total carbohydrates did not show any significant difference (p<0.01). The highest relative water content was measured in 700 mg/L CO2 treatment, when the plants were irrigated with distilled water (no salinity stress). Application of 700 and 1050 mg/L CO2 treatments, at the highest salinity level, reduced electrolyte leakage by 26 and 19 percent, respectively, as compared to CO2 control treatment.
  • Authors:
    • Buerkert, Andreas
    • Bruentrup, Michael
    • Lamers, John P. A.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 1
  • Year: 2015
  • Summary: Low concentrations of phosphorus (P) also limit crop production on the acid, sandy soils in Sudano-Sahelian West Africa (SSWA). An increased P-use is thus a key leverage for enhancing food security and alleviating poverty. Therefore, P-imports into the predominating agro-pastoral farming systems are indispensable, but most smallholders are cash-poor and risk averse, face labor-constraints, and P-fertiliser responses are site-specific. Key to the adoption of any new technology is a high financial performance with low risk levels of failure, low demands of labor and cash, and adaptation to the prevailing farming systems. Financial performances were assessed from nine, annually applied fertilising practices during 4 years in five SSWA zones. Information about the farming systems, labor demands, and input-output prices stem from secondary sources. The profitability largely depended on rainfall and location-specific soil conditions, but those of annually repeated mineral and organic P-strategies increased over time. Several P-fertilisations were profitable on a per land unit basis, but could not compete with farmers' practices on a per labor unit basis. Mulching with and without P (13 kg P ha(-1)) were not financially superior, but the broadcast application of 13 kg P ha(-1) became profitable over time. Hill-placed P (4 kg P ha(-1)), also known as micro-dosing, was a profitable alternative to farmers' practices particularly in the intermediate rainfall zone. The results showed the importance of recommendations following rainfall zones, which are of interest across a spectrum of users including policy makers, land use practitioners, private firms, NGOs and research for development implementers.
  • Authors:
    • Zhan DongXia
    • Zhang Chao
    • Yang Ying
    • Luo HongHai
    • Zhang YaLi
    • Zhang WangFeng
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Little is known about how water deficit affects cotton ( Gossypium hirsutum L.) canopy architecture and the vertical distribution of photosynthesis within the canopy. The objective of this 2-yr field experiment was to determine the effects of reduced water supply on (i) surface area distribution within a cotton canopy, (ii) the transmission of photosynthetically active radiation (PAR) within the canopy, and (iii) the contribution of leaves and non-leaf organs at different positions within the canopy to whole-canopy photosynthesis. The results showed that compared with conventional irrigation, water deficit reduced leaf surface area in the upper canopy layer by 20 to 46% and increased PAR transmission into the mid-canopy layer by 38 to 73%. Slight water deficit reduced leaf photosynthetic rates in the upper canopy layer by 24%, but increased leaf photosynthetic rates in the mid-canopy layer by 23% and the lower canopy layer by 79%. Compared with conventional irrigation, slight water deficit had no significant effect on yield, whereas moderate water deficit significantly reduced both variables. Leaves, especially those in the upper canopy layer, were the main drivers of whole-canopy photosynthesis. On a percentage basis, non-leaf organs accounted for <26% of whole-canopy photosynthesis. Future research is needed to learn more about the photosynthetic potential of non-leaf organs and their response to water deficit.
  • Authors:
    • Baudron,F.
    • Aynalem Mamo
    • Dereje Tirfessa
    • Mekuria Argaw
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 207
  • Year: 2015
  • Summary: Livestock provides numerous benefits to smallholders in sub-Saharan Africa, but also represents a potential agent of environmental degradation. Exclosures have been implemented in grazing areas for the past decades in Ethiopia and have been effective in regenerating natural vegetation, controlling soil erosion and increasing soil fertility. More recently, the principles of exclosure have been applied to farmland in pilot areas of Ethiopia. This paper analyzes the impact of eight years of farmland exclosure in the Central Rift Valley of Ethiopia. The performance of 'exclosed farms' (EF) - in which livestock was excluded from the farmland throughout the year - was compared to the performance of neighboring 'open grazing farms' (OF) - in which fields were open for aftermath grazing in winter. EF and OF had significantly different feed and fuel use strategies. Compared to OF, EF relied less on cereal residues, farmland grass, and livestock dung, and more on biomass produced in the communal grazing area (trees and grass) and tree biomass produced on-farm. Because of these different patterns of feed and fuel use, more biomass - in the form of crop residue, manure and compost - was available as soil amendment in EF. This translated into significantly more fertile soils and significantly higher tef yields in EF as compared to OF (1980644 kg ha -1 in EF vs. 1173434 kg ha -1 in OF). These results demonstrate that farmland exclosure is a practical pathway toward sustainable intensification. However, attention should be drawn to three points: (1) the approach impacted positively on crop productivity, but had a negligible impact on livestock productivity, (2) EF livestock still depended partially on grazing (outside of the exclosure) for their acquisition of feed, pointing at the fact that zero-grazing sensu stricto may not be realistic in semi-arid areas of Ethiopia, and (3) land rehabilitation through controlled grazing may only be feasible in particular geographic locations ( e.g., physical barriers preventing outside livestock to access the area, and presence of alternative grazing areas in the vicinity).