Key questions and uncertainties associated with the assessment of the cropland greenhouse gas balance

Published Date
Agriculture, Ecosystems & Environment
15 November 2010, Vol.139(3):293–301, doi:10.1016/j.agee.2010.05.009
The carbon balance of European croplands

• Author 

• Bruce Osborne ^a,,
 
• Matt Saunders ^a
 
• David Walmsley ^a
 
• Michael Jones ^b
 
• Pete Smith ^c

• aUCD School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland
• bDepartment of Botany, School of Natural Sciences, Trinity College, Dublin 2, Ireland
• cInstitute of Biological & Environmental Sciences, School of Biological Sciences, University of Aberdeen, Cruickshank Building, St Machar Drive, Aberdeen AB24 3UU, Scotland, UK

Received 19 August 2009. Revised 25 May 2010. Accepted 26 May 2010. Available online 23 June 2010.

Abstract

The geographic spread of croplands, together with the diversity of crops and management practices, and the largely seasonally-restricted cycle of crop production, complicates a detailed assessment of the cropland carbon or greenhouse gas balance at the European/continental scale. Whilst the major components that contribute to the carbon budget at the ecosystem scale have been identified, a number of additional factors/parameters remain to be quantified, such as a more detailed assessment of both the direct and indirect impacts of volatile organic carbon production. In addition, there are various ways in which improved estimates of the carbon balance might be achieved, some of which are largely specific to croplands, whilst others are of more general relevance. These include a more detailed examination of dissolved organic as well as inorganic carbon fluxes, more extensive measurements of non-carbon greenhouse gases, such as methane and nitrous oxide, and their fluxes between the atmosphere and the soil, rather than just focussing on losses, and improved measurement protocols, particularly the partitioning of heterotrophic and autotrophic respiration. In addition, there is a need for improved spatial resolution, either through more intensive sampling and/or the employment and development of new technology that can be used for making continuous measurements over larger areas of land. Relatively straightforward assessments of the inputs and losses associated with harvests and the use of organic fertilizers are also required. The quantitative significance of fires is also unclear, with a potential complexity of interactions with soil and atmospheric processes that are not reflected in current assessments. Finally, a more comprehensive coverage of the dominant crops/cropping systems are required before we can say that the budgets are truly reflective of the major European cropland ecosystems.

Keywords

Carbon/greenhouse gas budgets

Component fluxes

Cropland diversity

Missing values

Uncertainties

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 Table 1

Table 1.

Fig. 1.

• ⁎ 
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Assessing the nitrous oxide mole fraction of soils from perennial biofuel and corn–soybean fields

Published Date
Agriculture, Ecosystems & Environment
15 August 2010, Vol.138(3):299–305, doi:10.1016/j.agee.2010.06.002

• Author 

• Krishna P. Woli ^a
• Mark B. David ^a,,
• Robert G. Darmody ^a
• Corey A. Mitchell ^a
• Candice M. Smith ^b

• aUniversity of Illinois at Urbana-Champaign, Department of Natural Resources and Environmental Sciences, W-503 Turner Hall, 1102 S. Goodwin Av., Urbana, IL 61801, United States
• bUniversity of Illinois at Urbana-Champaign, Institute of Genomic Biology, 1206 W. Gregory Drive, Urbana, IL 61801, United States

Received 26 January 2010. Revised 27 May 2010. Accepted 1 June 2010. Available online 23 June 2010. 

Abstract

Little is known about how long-term biofuel production might alter soil nitrogen (N) gas emissions. We conducted a laboratory incubation of surface soils (0–16 cm) from perennial biofuel trial plots (established 2002) at sites in Northern (Dekalb, Mollisols), Central (Urbana, Mollisols), and Southern (Dixon Springs, Alfisols) Illinois, USA. Soils from unfertilized plots of Miscanthus (Miscanthus × giganteus) and switchgrass (Panicum virgatum) were compared to fertilized corn–soybean plots during early spring and again in mid-summer. Fresh soils were packed into jars at a bulk density of 1.2 g cm⁻³ and adjusted to a water-filled pore space of 85%. We added about 10 mg NO₃-N kg⁻¹ dry soil in each sample, incubated for 24 h, and collected gas samples at 0, 1, 2, and 4 h to measure production of N₂O and N₂ using a C₂H₂ inhibition technique, which allowed calculation of the N₂O mole fraction (N₂O:(N₂O + N₂)). The mean N₂O mole fraction (MF) was significantly higher for the cropped plot (0.83 and 0.99) than that for Miscanthus (0.48 and 0.31) and switchgrass (0.45 and 0.22) plots at the Southern site in spring and summer, respectively. There were no significant differences in N₂O MF among treatment plots for the Central and Northern sites. Exchangeable soil nitrate concentrations best explained the N₂O MFs for all treatments in both seasons, and production of perennial biofuel feedstock crops did not exhibit an apparent influence on N₂O MFs. It appeared that soil type combined with fertilizer additions were the major factors controlling the MF of N₂O in our fields, and was much more important than the crop grown or any new soil C added.

Keywords

Biofuel

Corn–soybean

Denitrification

Miscanthus × giganteus

N₂O mole fraction

Switchgrass

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 Table 1

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Table 2.

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 Table 3

Table 3.

• ⁎ 
  Corresponding author. Tel.: +1 217 333 4308; fax: +1 217 244 3219.
  
  

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The potential of hyperspectral and multi-spectral imagery to enhance archaeological cropmark detection: a comparative study

Published Date
Journal of Archaeological Science
July 2012, Vol.39(7):1915–1924, doi:10.1016/j.jas.2012.01.034

• Author 

• Syed Ali Aqdus ^a,,,
• William S. Hanson ^b
• Jane Drummond ^a

• aDepartment of Geographical and Earth Sciences, University of Glasgow, Glasgow, Scotland G12 8QQ, United Kingdom
• bDepartment of Archaeology, University of Glasgow, G12 8QQ, United Kingdom

Received 28 August 2010. Revised 17 January 2012. Accepted 26 January 2012. Available online 8 February 2012. 

Abstract

Aerial photography has made the single most important contribution to our improved appreciation of the density, diversity and distribution of archaeological sites in Britain since World War Two. This is particularly the case for areas of intensive lowland agriculture where ploughed-out sites are known mainly from marks in the crops growing above them. However, reconnaissance for such cropmarks is not equally effective throughout the lowlands, because of the particular conditions of drier weather, well-drained soils and arable agriculture required before they become visible, and is highly unpredictable.

Given that the appearance of cropmarks is linked to moisture stress in growing plants, they are potentially detectable at bandwidths outside the visible spectrum and before they become apparent therein. This paper focuses on the application of two spectral enhancement techniques: Principal component analysis and Tasselled cap transformation. Comparing a range of imagery (CASI-2, ATM and digital vertical photographic data) from two case study areas in Lowland Scotland, each with very different environmental, agricultural and archaeological backgrounds to facilitate further comparisons, the paper demonstrates that multi-spectral/hyperspectral imagery can enhance the identification of otherwise invisible archaeological sites, particularly in the near-infrared part of the spectrum. However, the lower spatial resolution of such imagery, compared to photography, can make the often diffuse and incomplete cropmark traces more difficult to determine with confidence.

Highlights

► Hyperspectral data enhances the identification of invisible archaeological sites. ► Archaeological cropmarks are mostly seen in the near-infrared. ► PCA was the most effective tool for visualising the imagery. ► No single image processing technique consistently produced the best results.

Keywords

Aerial archaeology

ATM

CASI

Cropmarks

Clyde valley

Hyperspectral

Inveresk

Multi-spectral

Principal component analysis

Tasselled cap transformation

Scotland

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• ∗ 
  Corresponding author. Tel.: +44 1416388386.
  
  

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Weed species richness in winter wheat increases with landscape heterogeneity

Published Date
Agriculture, Ecosystems & Environment
15 August 2010, Vol.138(3):318–323, doi:10.1016/j.agee.2010.06.005

• Author 

• Sabrina Gaba ^a
• Bruno Chauvel ^a
• Fabrice Dessaint ^a
• Vincent Bretagnolle ^b
• Sandrine Petit ^a,,

• aINRA, UMR1210, Biologie et Gestion des Adventices, F-21000 Dijon cedex, France
• bCNRS, Centre d’Etudes Biologiques de Chizé, F-79360 Beauvoir sur Niort, France

Received 18 September 2009. Revised 3 June 2010. Accepted 8 June 2010. Available online 8 July 2010. 

Abstract

There is empirical evidence that landscape composition and structure can affect the distribution and long-term dynamics of the organisms that live in it. Weeds are no exception and in this paper, we investigated how weed richness and diversity in 123 winter wheat fields within a small agricultural region were affected by the landscape surrounding each field (radii ranging from 100 to 1000 m) and the field properties such as its size and the preceding crop. Landscape was described by its proportion (cover of spring crops, winter crops, woodland, grassland, set-aside) and its structure (number of fields, number of land use types). Akaïke criterion-based models indicated that variations in weeds were best explained at the 200 m radius. At that scale, hierarchical partitioning shows that the independent contributions of field level and landscape level variables were significant for two variables. Weed richness and weed diversity increased significantly as field size decreased and as the number of fields within 200 m increased. This suggests that weed richness and diversity are higher in landscapes that have a finer grain, probably because these landscapes offer more habitat heterogeneity within cultivated areas and contain more crop edges that can shelter many weed species.

Graphical abstract



Research highlights

▶ Variations in weeds were best explained at a 200 m radius. ▶ Weed richness increased as field size decreased and as the number of fields within 200 m increased. ▶ Weed richness and diversity seemed higher in heterogeneous landscapes.

Keywords

Weed communities

Agro-ecosystem

Spatial autocorrelation

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 Table 1

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Fig. 1.

 Table 2

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 Table 3

Table 3.

Fig. 2.

• ⁎ 
  Corresponding author. Tel.: +33 3 80 69 30 32; fax: +33 3 80 69 32 62.
  
  

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