• Authors:
    • Jones, L. E.
    • Maddison, A. L.
    • Castle, M.
    • Barraclough, T. J. P.
    • Purdy, S. J.
    • Cunniff, J.
    • Shield, I. F.
    • Gregory, A. S.
    • Karp, A.
  • Source: Science Article
  • Volume: 80
  • Year: 2015
  • Summary: Willows ( Salix spp.) grown as short rotation coppice (SRC) are viewed as a sustainable source of biomass with a positive greenhouse gas (GHG) balance due to their potential to fix and accumulate carbon (C) below ground. However, exploiting this potential has been limited by the paucity of data available on below ground biomass allocation and the extent to which it varies between genotypes. Furthermore, it is likely that allocation can be altered considerably by environment. To investigate the role of genotype and environment on allocation, four willow genotypes were grown at two replicated field sites in southeast England and west Wales, UK. Above and below ground biomass was intensively measured over two two-year rotations. Significant genotypic differences in biomass allocation were identified, with below ground allocation differing by up to 10% between genotypes. Importantly, the genotype with the highest below ground biomass also had the highest above ground yield. Furthermore, leaf area was found to be a good predictor of below ground biomass. Growth environment significantly impacted allocation; the willow genotypes grown in west Wales had up to 94% more biomass below ground by the end of the second rotation. A single investigation into fine roots showed the same pattern with double the volume of fine roots present. This greater below ground allocation may be attributed primarily to higher wind speeds, plus differences in humidity and soil characteristics. These results demonstrate that the capacity exists to breed plants with both high yields and high potential for C accumulation.
  • Authors:
    • Mahdavi, B.
    • Modarres-Sanavy, S. A. M.
    • Dehshiri, A.
  • Source: Agronomy Article
  • Volume: 61
  • Issue: 10
  • Year: 2015
  • Summary: This study was done to evaluate the effects of increasing concentrations of CO2 (CC) on rapeseed. Pot experiments were done with three cultivars (Okapi, Zarfam and RGS003) of rapeseed (Brassica napus) for salinity tolerance. Four levels of salinity (0, 5, 10 and 15dS m(-1)) were tested on the three cultivars at three CC (350, 700 and 1050mmolL(-1)) at the greenhouse of Tarbiat Modares University, Iran, during the crop seasons of 2010 to 2011. Three CCs were considered as three environments and the other two treatments (salinity and cultivar) were tested within these environments in a complete block design arranged as a factorial. Results indicated that photosynthetic rates declined with increasing levels of salinity. Elevated CC significantly increased rates of photosynthesis. The highest CC reduced the impact of salinity on photosynthesis. Increased CC reduced the rate of transpiration, which had the effects of increasing rates of photosynthesis and water use efficiency (WUE); these effects increased vegetative growth and reduced the adverse effects of salinity. Increased CC and salinity reduced harvest index. WUE increased with CC increment, and decreased with salinity elevation.
  • Authors:
    • Adams,H. D.
    • Collins,A. D.
    • Briggs,S. P.
    • Vennetier,M.
    • Dickman,L. T.
    • Sevanto,S. A.
    • Garcia-Forner,N.
    • Powers,H. H.
    • McDowell,N. G.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 11
  • Year: 2015
  • Summary: Higher temperatures associated with climate change are anticipated to trigger an earlier start to the growing season, which could increase the terrestrial C sink strength. Greater variability in the amount and timing of precipitation is also expected with higher temperatures, bringing increased drought stress to many ecosystems. We experimentally assessed the effects of higher temperature and drought on the foliar phenology and shoot growth of mature trees of two semiarid conifer species. We exposed field-grown trees to a ~45% reduction in precipitation with a rain-out structure ('drought'), a ~4.8 °C temperature increase with open-top chambers ('heat'), and a combination of both simultaneously ('drought+heat'). Over the 2013 growing season, drought, heat, and drought+heat treatments reduced shoot and needle growth in pinon pine ( Pinus edulis) by ≥39%, while juniper ( Juniperus monosperma) had low growth and little response to these treatments. Needle emergence on primary axis branches of pinon pine was delayed in heat, drought, and drought+heat treatments by 19-57 days, while secondary axis branches were less likely to produce needles in the heat treatment, and produced no needles at all in the drought+heat treatment. Growth of shoots and needles, and the timing of needle emergence correlated inversely with xylem water tension and positively with nonstructural carbohydrate concentrations. Our findings demonstrate the potential for delayed phenological development and reduced growth with higher temperatures and drought in tree species that are vulnerable to drought and reveal potential mechanistic links to physiological stress responses. Climate change projections of an earlier and longer growing season with higher temperatures, and consequent increases in terrestrial C sink strength, may be incorrect for regions where plants will face increased drought stress with climate change.
  • Authors:
    • Chauhan,Y. S.
    • Thorburn,P.
    • Biggs,J. S.
    • Wright,G. C.
  • Source: Research Article
  • Volume: 66
  • Issue: 11
  • Year: 2015
  • Summary: With the aim of increasing peanut production in Australia, the Australian peanut industry has recently considered growing peanuts in rotation with maize at Katherine in the Northern Territory - a location with a semi-arid tropical climate and surplus irrigation capacity. We used the well-validated APSIM model to examine potential agronomic benefits and long-term risks of this strategy under the current and warmer climates of the new region. Yield of the two crops, irrigation requirement, total soil organic carbon (SOC), nitrogen (N) losses and greenhouse gas (GHG) emissions were simulated. Sixteen climate stressors were used; these were generated by using global climate models ECHAM5, GFDL2.1, GFDL2.0 and MRIGCM232 with a median sensitivity under two Special Report of Emissions Scenarios over the 2030 and 2050 timeframes plus current climate (baseline) for Katherine. Effects were compared at three levels of irrigation and three levels of N fertiliser applied to maize grown in rotations of wet-season peanut and dry-season maize (WPDM), and wet-season maize and dry-season peanut (WMDP). The climate stressors projected average temperature increases of 1°C to 2.8°C in the dry (baseline 24.4°C) and wet (baseline 29.5°C) seasons for the 2030 and 2050 timeframes, respectively. Increased temperature caused a reduction in yield of both crops in both rotations. However, the overall yield advantage of WPDM increased from 41% to up to 53% compared with the industry-preferred sequence of WMDP under the worst climate projection. Increased temperature increased the irrigation requirement by up to 11% in WPDM, but caused a smaller reduction in total SOC accumulation and smaller increases in N losses and GHG emission compared with WMDP. We conclude that although increased temperature will reduce productivity and total SOC accumulation, and increase N losses and GHG emissions in Katherine or similar northern Australian environments, the WPDM sequence should be preferable over the industry-preferred sequence because of its overall yield and sustainability advantages in warmer climates. Any limitations of irrigation resulting from climate change could, however, limit these advantages.
  • Authors:
    • Wang, Z.
    • Wang, S.
    • Li, M.
    • Chen, H.
    • Wang, X.
    • Tian, X.
    • Liu, T.
    • Chen, Y.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Revealing the response of cereal yield and water use efficiency (WUE) to water management practices is crucial for achieving high and stable grain yields in drylands. A 3-yr field study was conducted to develop a high-yield, water-saving cultivation strategy for winter wheat in the Loess Plateau of China. The study's treatments included (i) a control (CK), that is, no mulch or fertilizer, (ii) nitrogen and phosphorus fertilizers (NP), (iii) plastic film mulch plus fertilizers (NP+PF), (iv) straw mulch plus fertilizers (NP+S), and (v) plastic film combined with straw mulch plus fertilizers (NP+PF+S). The results indicated that, compared with CK, the NP treatment improved the grain yield (112%) and WUE (96%) of winter wheat but resulted in a 12% reduction in soil water storage after the jointing stage. With the NP+S treatment, there was no difference recorded in grain yield, yield components, or WUE of winter wheat (relative to the NP treatment). With the NP+PF treatment, there was a 53% increase in grain yield, a 46% increase in WUE, and a 21% increase in soil water storage after jointing compared to the NP treatment. The plastic film could also modify soil temperature, resulting in maximized soil water retention. Additionally, the NP+PF and NP+PF+S treatments resulted in similar results. Taking into account agricultural, environmental, and economic factors, in addition to optimal fertilization (NP), plastic film mulch is the recommended practice for maximum yield and water retention in tablelands, whereas plastic film combined with straw mulch is recommended in terraces.
  • Authors:
    • Mango, N.
    • Nyamangara, J.
    • Nyamugafata, P.
    • Dunjana, N.
    • Gwenzi, W.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Crop water productivity is often regarded as indicating the water use efficiency of crops, an important aspect, particularly under erratic rainfall conditions. This study investigated the effects of cattle manure and mineral-N fertilizer application on maize ( Zea mays L.) water productivity (MWP) on clay and sandy soils in a smallholder farming area of Zimbabwe. Four fields previously exhibiting heterogeneous fertility were managed under the following treatments: control (no amendment) and cattle manure (5, 15, and 25 Mg ha -1)+100 kg ha -1 mineral-N fertilizer for 7 yr. Thereafter, the effects of fertility treatment on MWP were expressed as actual maize grain yield produced per unit of seasonal transpiration modeled using AquaCrop. Furthermore, the relationship of MWP to physical soil properties was determined using principal component analysis. The MWP significantly ( P<0.05) improved with an increase in cattle manure plus mineral-N fertilizer application over control on both soils ranging between 0.5 and 1.7 kg m -3 and between 0.24 and 1.1 kg m -3 on clay and sandy soils, respectively. The MWP was significantly correlated ( P<0.05) with the steady-state infiltration rate on the clay soil and with soil organic C on the sandy soil. We concluded that cattle manure and mineral-N fertilizer application is key to MWP improvement in rainfed smallholder cropping systems and is closely coupled with improvements in physical soil properties on clay soil than sandy soil. Therefore, the observations attest to the importance of site-specific management that could contribute to efficient resource use in resource-constrained farming areas.
  • Authors:
    • Duniway, M. C.
    • Munson, S. M.
    • Bradford, J. B.
    • Gremer, J. R.
  • Source: Primary Research Article
  • Volume: 21
  • Issue: 11
  • Year: 2015
  • Summary: Climate change predictions include warming and drying trends, which are expected to be particularly pronounced in the southwestern United States. In this region, grassland dynamics are tightly linked to available moisture, yet it has proven difficult to resolve what aspects of climate drive vegetation change. In part, this is because it is unclear how heterogeneity in soils affects plant responses to climate. Here, we combine climate and soil properties with a mechanistic soil water model to explain temporal fluctuations in perennial grass cover, quantify where and the degree to which incorporating soil water dynamics enhances our ability to understand temporal patterns, and explore the potential consequences of climate change by assessing future trajectories of important climate and soil water variables. Our analyses focused on long-term (20-56 years) perennial grass dynamics across the Colorado Plateau, Sonoran, and Chihuahuan Desert regions. Our results suggest that climate variability has negative effects on grass cover, and that precipitation subsidies that extend growing seasons are beneficial. Soil water metrics, including the number of dry days and availability of water from deeper (>30 cm) soil layers, explained additional grass cover variability. While individual climate variables were ranked as more important in explaining grass cover, collectively soil water accounted for 40-60% of the total explained variance. Soil water conditions were more useful for understanding the responses of C 3 than C 4 grass species. Projections of water balance variables under climate change indicate that conditions that currently support perennial grasses will be less common in the future, and these altered conditions will be more pronounced in the Chihuahuan Desert and Colorado Plateau. We conclude that incorporating multiple aspects of climate and accounting for soil variability can improve our ability to understand patterns, identify areas of vulnerability, and predict the future of desert grasslands.
  • Authors:
    • Chapman, S.
    • McLean, G.
    • Zheng, B.
    • Chenu, K.
    • Hammer, G.
    • Lobell, D.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 11
  • Year: 2015
  • Summary: Characterization of drought environment types (ETs) has proven useful for breeding crops for drought-prone regions. Here, we consider how changes in climate and atmospheric carbon dioxide (CO 2) concentrations will affect drought ET frequencies in sorghum and wheat systems of northeast Australia. We also modify APSIM (the Agricultural Production Systems Simulator) to incorporate extreme heat effects on grain number and weight, and then evaluate changes in the occurrence of heat-induced yield losses of more than 10%, as well as the co-occurrence of drought and heat. More than six million simulations spanning representative locations, soil types, management systems, and 33 climate projections led to three key findings. First, the projected frequency of drought decreased slightly for most climate projections for both sorghum and wheat, but for different reasons. In sorghum, warming exacerbated drought stresses by raising the atmospheric vapor pressure deficit and reducing transpiration efficiency (TE), but an increase in TE due to elevated CO 2 more than offset these effects. In wheat, warming reduced drought stress during spring by hastening development through winter and reducing exposure to terminal drought. Elevated CO 2 increased TE but also raised radiation-use efficiency and overall growth rates and water use, thereby offsetting much of the drought reduction from warming. Second, adding explicit effects of heat on grain number and grain size often switched projected yield impacts from positive to negative. Finally, although average yield losses associated with drought will remain generally higher than that for heat stress for the next half century, the relative importance of heat is steadily growing. This trend, as well as the likely high degree of genetic variability in heat tolerance, suggests that more emphasis on heat tolerance is warranted in breeding programs. At the same time, work on drought tolerance should continue with an emphasis on drought that co-occurs with extreme heat.
  • Authors:
    • Calder, G.
  • Source: Climatic Change
  • Volume: 133
  • Issue: 3
  • Year: 2015
  • Summary: It is banal to say that different beliefs provide the basis for different conceptions of the good and diverse ways of life, the protection of which will seem to many to be paramount as a matter of justice. But what happens when those beliefs are about global processes of the magnitude of those involved in climate change, with the scale of their implications? How, and to what extent, should the diversity of local beliefs about factors relevant to climate change be factored into a normative response to the challenges it poses? This article is framed in response to the companion piece 'Local perceptions in climate change debates', which presents detailed contrasts between such beliefs in Peru and the South Tyrol. Focusing on perceptions of the nature/culture relationship as an example, I contrast 'globalist' and 'localist' normative responses to evidence of such diversity in belief. Both are limited, to the extent that they dwell on the fair treatment of beliefs. I argue that normatively speaking, what is crucial is not accommodating diversity in belief - as if beliefs about the factors implicated in climate change were on a par with other beliefs about the nature of the good - but acknowledging the requirement to make 'thick' commitments about which such beliefs are most adequate. Alongside their fascinating contributions in other respects, anthropological findings can be crucial in this one. They will help furnish the kind of understanding of human/nature relations on which a political philosophy of climate change must depend.
  • Authors:
    • Pritchard, D.
    • Biswas, W.
    • Engelbrecht, D.
    • Ahmad, W.
  • Source: Remote Sensing Applications: Society and Environment
  • Volume: 2
  • Year: 2015
  • Summary: The causes and implications of climate change are currently at the forefront of many researching agendas. Countries that have ratified the Kyoto Protocol are bound by agreements to focus on and reduce greenhouse gas emissions which impact on the natural and anthropogenic environment. Internationally agriculture contributes to environmental impacts such as land use change, loss of biodiversity, greenhouse gas emissions, increased soil salinity, soil acidity and soil erosion. To combat and control the greenhouse gas emissions generated during agricultural production, methodologies are being developed and investigated worldwide. Agriculture is the second largest emitter of greenhouse gases in Australia and consequently the integrated spatial technology was developed using data from a crop rotation project conducted by the Department of Agriculture and Food, Western Australia. The aim of the integrated spatial technology was to combine remote sensing, geographical information systems and life cycle assessment, to ascertain the component or system within the agricultural production cycle, generating the most greenhouse gases. Cleaner production strategies were then used to develop mitigation measures for the reduction of greenhouse gases within the integrated spatial technology. © 2015 Elsevier B.V.