• Authors:
    • Ross, A.
  • Source: Journal of Agricultural and Food Chemistry
  • Volume: 60
  • Issue: 36
  • Year: 2012
  • Summary: Alkylresorcinols are phenolic lipids, with homologues ranging from C17 to C25, found in high concentrations in whole grain wheat and rye, lower concentrations in barley, and negligible concentrations in refined wheat flour. The analysis of alkylresorcinols is of importance due to their potential as biomarkers of whole grain intake and emerging evidence for some biological effects. Present HPLC methods have insufficient resolution for accurately quantitating the mix of alkyl- and alkenylresorcinols found in rye. An ultrahigh-pressure liquid chromatography method was developed, and three detection methods (CoulArray (CAED), ultraviolet (UV), and fluorescence detection (FD)) were compared for cereal alkylresorcinol analysis. The lower limits of quantitation and detection were 50 and 20 pg injected, 5 pg and 2 pg injected, and 500 and 1250 pg injected for FD, CAED, and UV, respectively. FD and CAED provided similar results, with some bias for higher results with FD (
  • Authors:
    • Lartey, R.
    • Jabro, J.
    • Caesar-Tonthat, T.
    • Lenssen, A.
    • Sainju, U.
    • Evans, R.
    • Allen, B.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 93
  • Issue: 3
  • Year: 2012
  • Summary: Management practices may influence dryland soil N cycling. We evaluated the effects of tillage, crop rotation, and cultural practice on dryland crop biomass (stems and leaves) N, surface residue N, and soil N fractions at the 0-20 cm depth in a Williams loam from 2004 to 2008 in eastern Montana, USA. Treatments were two tillage practices (no-tillage [NT] and conventional tillage [CT]), two crop rotations (continuous spring wheat [ Triticum aestivum L.] [CW] and spring wheat-barley [ Hordeum vulgaris L.] hay-corn [ Zea mays L.]-pea [ Pisum sativum L.] [W-B-C-P]), and two cultural practices (regular [conventional seed rates and plant spacing, conventional planting date, broadcast N fertilization, and reduced stubble height] and ecological [variable seed rates and plant spacing, delayed planting, banded N fertilization, and increased stubble height]). Nitrogen fractions were soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), NH 4-N, and NO 3-N. Crop biomass N was 30% greater in W-B-C-P than in CW in 2005. Surface residue N was 30-34% greater in NT with the regular and ecological practices than in CT with the regular practice. The STN, PON, and MBN at 10-20 and 0-20 cm were 5-41% greater in NT or CW with the regular practice than in CT or CW with the ecological practice. The PNM at 5-10 cm was 22% greater in the regular than in the ecological practice. The NH 4-N and NO 3-N contents at 10-20 and 0-20 cm were greater in CT with W-B-C-P and the regular practice than with most other treatments in 2007. Surface residue and soil N fractions, except PNM and NO 3-N, declined from autumn 2007 to spring 2008. In 2008, NT with W-B-C-P and the regular practice gained 400 kg N ha -1 compared with a loss of 221 kg N ha -1 to a gain of 219 kg N ha -1 in other treatments. No-tillage with the regular cultural practice increased surface residue and soil N storage but conventional tillage with diversified crop rotation and the regular practice increased soil N availability. Because of continuous N mineralization, surface residue and soil N storage decreased without influencing N availability from autumn to the following spring.
  • Authors:
    • Drinkwater, L.
    • Schipanski, M.
  • Source: Plant and Soil
  • Volume: 357
  • Issue: 1/2
  • Year: 2012
  • Summary: Background and aims: The selection of legume species and species mixtures influences agroecosystem nitrogen (N) and carbon cycling. We utilized a fertility gradient to investigate the effects of plant species interactions on biological N fixation of an annual and perennial legume in response to shifting soil resource availability. Methods: Legume N fixation of annual field pea ( Pisum sativum) and perennial red clover ( Trifolium pratense) grown in monoculture and mixtures with oats ( Avena sativa) or orchardgrass ( Dactylis glomerata) was estimated using the 15N natural abundance method across 15 farm fields and we measured six soil N pools ranging from labile to more recalcitrant. Results: Evidence of complementary and facilitative species interactions was stronger for the perennial red clover-orchardgrass mixture than for the annual field pea-oat mixture (N Land Equivalency Ratios were 1.6 and 1.2, respectively). We estimated that the transfer of fixed N from red clover to orchardgrass increased aboveground N fixation estimates by 15% from 33 to 38 kg N ha -1. Despite a more than 2-fold range in soil organic matter levels and more than 3-fold range in labile soil N pools across field sites, the N fertility gradient was not a strong predictor of N fixation. While grass N assimilation was positively correlated with soil N pools, we found only weak, inverse correlations between legume N fixation and soil N availability. In grass-legume mixtures, soil N availability indirectly influenced N fixation through plant competition. Conclusions: These results suggest that increasing diversity of cropping systems, particularly through the incorporation of perennial mixtures into rotations, could improve overall agroecosystem N cycling efficiency.
  • Authors:
    • Szendrei, Z.
  • Source: Entomologia Experimentalis et Applicata
  • Volume: 143
  • Issue: 2
  • Year: 2012
  • Summary: Habitat diversification can influence the interactions of insects with plants and this can be used in agroecosystems for the management of pest populations. Plant diversification can be achieved through planting crops, such as trap crops, or by adjusting weed management. Aster leafhopper, Macrosteles quadrilineatus Forbes (Hemiptera: Cicadellidae), is a polyphagous species that uses cereals, vegetables, and weeds as host plants. The influence of weeds on M. quadrilineatus abundance was investigated experimentally in carrot [ Daucus carota L. cv. Canada (Apiaceae)] field plots by adjusting the level of management of two groups of weeds (broadleaf and grass) and by comparing it to weed-free plots. The preference of M. quadrilineatus for different cereal and weed species relative to carrots was tested in choice test assays. Habitat context influenced the abundance of M. quadrilineatus in the field experiments. The presence of border crops such as oat, rye, barley, wheat, and triticale did not significantly attract or repel this insect to carrot plots compared to the no-border treatment. However, spelt-bordered plots had 42% fewer M. quadrilineatus than three treatments, triticale, wheat, and barley, that had the highest insect abundance. The type of weed management affected M. quadrilineatus abundance in carrot plots, but not the frequency of herbicide application. Plots that had carrot growing with broadleaf-weeds had about 59% fewer M. quadrilineatus compared with those growing with crabgrass or carrot alone. In the greenhouse choice tests, grasses (e.g., cereals) attracted and broadleaf-weeds repelled M. quadrilineatus relative to carrots. In summary, carrot growers may be able to manage this pest by reducing the interaction of cereal cover crops with carrots and eliminating grassy weeds in commercial production fields.
  • Authors:
    • Prior, S. A.
    • Chappelka, A. H.
    • Zhu, W. Q.
    • Ren, W.
    • Liu, M. L.
    • Zhang ,C.
    • Tian, H. Q.
    • Chen, G. S.
    • Lockaby, G. B.
  • Source: CLIMATIC CHANGE
  • Volume: 114
  • Issue: 2
  • Year: 2012
  • Summary: Drought is one of the most devastating natural hazards faced by the Southern United States (SUS). Drought events and their adverse impacts on the economy, society and environment have been extensively reported during 1895-2007. Our aim is thus to characterize drought conditions in the SUS and explore the impacts on terrestrial ecosystem function (i.e., net primary productivity (NPP) and net carbon exchange (NCE)). Standard precipitation index (SPI) was used to characterize drought intensity and duration, and a process-based ecosystem model was used to explore the relationship between drought and ecosystem function. Combining overall information on growing-season SPI, drought area and duration, we concluded there was no significant change in drought conditions for the SUS during 1895-2007. However, increased drought intensity was found for many areas in the east, resulting in significant decreases in NPP for these areas, with the largest decrease up to 40% during extreme droughts. Changes in precipitation patterns increased C emissions of 0.16 Pg (1 Pg = 10(15) g) in the SUS during 1895-2007. The west (dry region) acted as a C sink due to increased precipitation, while the east (water-rich region) acted as a C source due to increased drought intensity. Both NPP and NCE significantly increased along a gradient of declining drought intensity. Changes in precipitation resulted in C sources in forest, wetland, and cropland ecosystems, while C sinks in shrubland and grassland ecosystems. Changes in air temperature could either enhance or reduce drought impacts on NPP and NCE across different vegetation types.
  • Authors:
    • Duffy, P. B.
    • Tebaldi, C.
  • Source: Climatic Change
  • Volume: 111
  • Issue: 2
  • Year: 2012
  • Summary: Human-caused climate change can affect weather and climate extremes, as well as mean climate properties. Analysis of observations and climate model results shows that previously rare (5th percentile) summertime average temperatures are presently occurring with greatly increased frequency in some regions of the 48 contiguous United States. Broad agreement between observations and a mean of results based upon 16 global climate models suggests that this result is more consistent with the consequences of increasing greenhouse gas concentrations than with the effects of natural climate variability. This conclusion is further supported by a statistical analysis based on resampling of observations and model output. The same climate models project that the prevalence of previously extreme summer temperatures will continue to increase, occurring in well over 50% of summers by mid-century.
  • Authors:
    • Dahms, D.
    • Pichler, B.
    • Krebs, R.
    • Favilli, F.
    • Egli, M.
  • Source: GEODERMA
  • Volume: 183
  • Year: 2012
  • Summary: Using published and new chronosequence datasets from the European Alps and the Wind River Range (Rocky Mountains, USA), we report for the first time a chronosequence of more than 1 Ma for soil organic carbon, nitrogen and organic matter (SUM) fractions from alpine soils. The investigated parameters include total carbon and nitrogen as well as the stable (resistant to H2O2 oxidation) C and N fractions. Time trends were analysed and are reported on the basis of stocks and concentrations. The accumulation rates of C and N strongly decreased with increasing soil age. Differences in trends between the European Alps and the Wind River Range might be attributed to the factor climate. For the drier Wind River Range, an asymptotic value of about 15 kg C m(-2) was reached after about 15 ky while an asymptotic value of 20-25 kg C m(-2) was measured for the moister European Alps after about 3 ky. The difference in N stocks between the two regions was less obvious. For both areas, N was in the range of 0.5-2 kg N m(-2). Using the exponential decay model, a steady state of C and N (stable and total) concentrations in the topsoil seemed to be reached after <1 ky (Alps) and 10 ky (Wind River Range). The retardation effect observed for the Wind River Range could probably be due to aeolian influx. For both areas, the asymptotic value of the stable fraction of C and N was in the range of 1-3 kg C m(-2) and 0.2-0.4 kg N m(-2), respectively. The stable organic fraction often has an age close to the age of the soils and consequently can reach thousands of years. The relative proportion of N and amides was higher in the stable organic fraction compared to the bulk soil. The sequestration rates of org. C and N in soils of the European Alps and the Wind River Range can reach very high values in very young soils whereas in old soils sequestration rates are several orders of magnitude lower. Old soils often integrate several cold and warm phases and different vegetation types. Nonetheless, the factor Time seems to be very dominant and covers the track of other factors in old soils.
  • Authors:
    • Randhir, T.
    • Mozumder, P.
    • Flugman, E.
  • Source: CLIMATIC CHANGE
  • Volume: 112
  • Issue: 3-4
  • Year: 2012
  • Summary: Slivers of land amidst the world's third largest barrier reef, the Florida Keys provide unique insights on the emerging challenges associated with adaptation to global climate change. While political will and public awareness are gradually shifting on the imposing risks, analysis of survey responses from experts and decision makers serving the Florida Keys (federal, state and local personnel) reveals insufficient resources, limited direction and leadership, and lack of institutional frameworks to facilitate the adaptation process. Against this backdrop, we investigate experts and decision makers' interest in an array of adaptation measures including their willingness to support a proposed 'Community Adaptation Fund' (CAF) to mobilize resources and lay the foundation for adaptation initiatives in the Florida Keys. We also explore potential funding sources for establishing the proposed CAF, and test the feasibility of a diverse set of financing mechanisms. We discuss implications of our findings in the context of enhancing adaptive capacity in the Florida Keys and beyond.
  • Authors:
    • Lund, J. R.
    • Hanak, E.
  • Source: CLIMATIC CHANGE
  • Volume: 111
  • Issue: 1
  • Year: 2012
  • Summary: California faces significant water management challenges from climate change, affecting water supply, aquatic ecosystems, and flood risks. Fortunately, the state also possesses adaptation tools and institutional capabilities that can limit vulnerability to changing conditions. Water supply managers have begun using underground storage, water transfers, conservation, recycling, and desalination to meet changing demands. These same tools are promising options for responding to a wide range of climate changes. Likewise, many staples of flood management-including reservoir operations, levees, bypasses, insurance, and land-use regulation-are available for the challenges of increased floods. Yet actions are also needed to improve response capacity. For water supply, a central issue is the management of the Sacramento-San Joaquin Delta, where new conveyance, habitat investments, and regulations are needed to sustain water supplies and protect endangered fish species. For flood management, among the least-examined aspects of water management with climate change, needed reforms include forward-looking reservoir operation planning and floodplain mapping, less restrictive rules for raising local funds, and improved public information on flood risks. For water quality, an urgent priority is better science. Although local agencies are central players, adaptation will require strong-willed state leadership to shape institutions, incentives, and regulations capable of responding to change. Federal cooperation often will be essential.
  • Authors:
    • Song, C. K.
    • Park, R. J.
    • Liou, K. N.
    • Gu, Y.
    • Kim, J.
  • Source: CLIMATIC CHANGE
  • Volume: 111
  • Issue: 3-4
  • Year: 2012
  • Summary: The direct and semi-direct radiative effects of anthropogenic aerosols on the radiative transfer and cloud fields in the Western United States (WUS) according to seasonal aerosol optical depth (AOD) and regional climate are examined using a regional climate model (RCM) in conjunction with the aerosol fields from a GEOS-Chem chemical-transport model (CTM) simulation. The two radiative effects cannot be separated within the experimental design in this study, thus the combined direct-and semi-direct effects are called radiative effects hereafter. The CTM shows that the AOD associated with the anthropogenic aerosols is chiefly due to sulfates with minor contributions from black carbon (BC) and that the AOD of the anthropogenic aerosol varies according to local emissions and the seasonal low-level winds. The RCM-simulated anthropogenic aerosol radiative effects vary according to the characteristics of regional climate, in addition to the AOD. The effects on the top of the atmosphere (TOA) outgoing shortwave radiation (OSRT) range from -0.2 Wm(-2) to -1 Wm(-2). In Northwestern US (NWUS), the maximum and minimum impact of anthropogenic aerosols on OSRT occurs in summer and winter, respectively, following the seasonal AOD. In Arizona-New Mexico (AZNM), the effect of anthropogenic sulfates on OSRT shows a bimodal distribution with winter/summer minima and spring/fall maxima, while the effect of anthropogenic BC shows a single peak in summer. The anthropogenic aerosols affect surface insolation range from -0.6 Wm(-2) to -2.4 Wm(-2), with similar variations found for the effects on OSRT except that the radiative effects of anthropogenic BC over AZNM show a bimodal distribution with spring/fall maxima and summer/winter minima. The radiative effects of anthropogenic sulfates on TOA outgoing longwave radiation (OLR) and the surface downward longwave radiation (DLRS) are notable only in summer and are characterized by strong geographical contrasts; the summer OLR in NWUS (AZNM) is reduced (enhanced) by 0.52 Wm(-2) (1.14 Wm(-2)). The anthropogenic sulfates enhance (reduce) summer DLRS by 0.2 Wm(-2) (0.65 Wm(-2)) in NWUS (AZNM). The anthropogenic BC affect DLRS noticeably only in AZNM during summer. The anthropogenic aerosols affect the cloud water path (CWP) and the radiative transfer noticeably only in summer when convective clouds are dominant. Primarily shortwave-reflecting anthropogenic sulfates decrease and increase CWP in AZNM and NWUS, respectively, however, the shortwave-absorbing anthropogenic BC reduces CWP in both regions. Due to strong feedback via convective clouds, the radiative effects of anthropogenic aerosols on the summer radiation field are more closely correlated with the changes in CWP than the AOD. The radiative effect of the total anthropogenic aerosols is dominated by the anthropogenic sulfates that contribute more than 80% of the total AOD associated with the anthropogenic aerosols.