Soil greenhouse gas emissions and soil C dynamics in bioenergy crops

Second generation bioenergy crops short rotation coppice (SRC) willow and Miscanthus x giganteus are the two main bioenergy crops grown in the UK. The first aim of this research was to quantify the in situ soil greenhouse gas (GHG) budget and to establish the drivers of these GHG fluxes for SRC willow and Miscanthus. The second aim of this research was to provide a more in-depth understanding of C cycling under Miscanthus i.e. litter and roots through two field experiments. The main findings were: The results from this work confirmed minimal emissions of CH4 and N2O from soil in second generation crops (non-food crops), SRC willow and Miscanthus. CO2 flux was found to be the major efflux from soils in both crops and showed a positive correlation with temperature and showed a negative correlation with soil moisture content. The majority of total CO2 flux from the soil surface under Miscanthus was from underground processes, with little contribution from aboveground litter decomposition to total flux. Litter played an important part in providing nutrients to the soil, which is vital in these crops since they are not fertilised. The high C:N ratio of Miscanthus litter and the high lignin content of SRC willow, resulted in an accumulation of litter on the soil surface and so may promote long-term C sequestration. Overall, the results from this work, combined with other literature would suggest that these crops offer advantages to first generation crops but more field-based studies are required to be able to say if these crops can offer large-scale GHG savings needed from this renewable energy source

Surficial Geologic Map of the Constantine 7.5-Minute Quadrangle, Kentucky

The Constantine 7.5-minute quadrangle is located west of Elizabethtown along the boundary of Hardin and Breckinridge Counties. The quadrangle lies along the northern section of the Dripping Springs Escarpment, which separates the Mammoth Cave Plateau and Pennyroyal regions of the Mississippian Sinkhole Plain physiographic province (McFarlan, 1943). Topography is mostly characterized by high-elevation plateaus, ridges, and knobs of the Mammoth Cave Plateau (up to 919 ft), which have been intensely dissected by the Rough River and its tributaries (down to 516 ft). A small area of the Pennyroyal extends into the eastern part of the quadrangle, which is marked by a relatively low-relief, low-elevation sinkhole plain. Sable (1964) mapped the bedrock geology of the quadrangle, which was later digitized by Conley (2002). Bedrock throughout the quadrangle is mapped as Upper Mississippian. A series of northeast-trending faults through the southeastern half of the quadrangle (splays from the Rough Creek Fault System) have created a series of horst and graben structures that control bedrock exposure and stream incision. The oldest bedrock lithologic unit mapped is the Ste. Genevieve Limestone, which is overlain by the Paoli Limestone; both are exposed in the Pennyroyal region in the eastern part of the quadrangle and northwest of the fault system. The Mooretown Formation and Beaver Bend Limestone are mostly exposed along steep slopes above the Paoli Limestone; a large area of Mooretown Formation is locally exposed in a broad plain situated northwest of the fault system in the center of the quadrangle. The Sample Sandstone overlies the Beaver Bend Limestone and covers the largest portion of plateaus and ridgetops in the area, mostly northwest of the fault system. The Reelsville Limestone and Golconda Formation overlie the Sample Sandstone and are exposed in isolated knobs and ridges northwest of the fault system, and extensively in the southeastern section of the quadrangle, where they are overlain by the Hardinsburg Sandstone, the youngest unit mapped in the Constantine quadrangle.https://uknowledge.uky.edu/kgs_cr/1002/thumbnail.jp

Surficial Geologic Map of the Flaherty 7.5-Minute Quadrangle, Kentucky

The Flaherty 7.5-minute quadrangle is located southwest of Louisville and northwest of Elizabethtown along the boundary between Hardin and Meade Counties. The quadrangle includes mostly the Pennyroyal region of the Mississippian Plateau and also smaller areas of the Mammoth Cave plateau and the highly dissected Dripping Springs escarpment in the western half of the map area (McDowell, 1986). Topography is mostly characterized by pervasive sinkhole development in a lower elevation and low-relief plain, and high-relief plateaus, ridges, and knobs of the Dripping Springs escarpment scattered along the west side of the quadrangle. Swadley (1963) mapped the bedrock geology of the quadrangle, which was later digitized by Crawford (2002). Mississippian bedrock is exposed throughout the quadrangle and is cut by several normal faults in the south. The St. Louis Limestone and overlying Ste. Genevieve Limestone are the oldest and lowest (stratigraphy and elevation) map units in Flaherty, and underlie the Pennyroyal region. The higher elevation landforms characterizing the Dripping Springs escarpment are predominantly underlain by the Paoli Limestone, Beaver Bend Limestone, and Sample Sandstone, from oldest to youngest respectively. The Mooretown Formation is stratigraphically above the Paoli Limestone and below the Beaver Bend Limestone, and is only exposed along Sand Ridge, a prominent landform in the quadrangle trending northeast to southwest. Previously mapped surficial deposits include alluvium in Otter Creek, Flippin Creek, and a large karst basin, and “slumped sandstone” (colluvium) along Sand Ridge and other smaller areas throughout the quadrangle (Swadley, 1963)

Surficial Geologic Map of the Big Clifty 7.5-Minute Quadrangle, Kentucky

The Big Clifty 7.5-minute quadrangle is located south of Louisville and west of Elizabethtown along the boundary between Hardin and Grayson Counties. The quadrangle lies within the Mammoth Cave plateau of the Mississippian Plateau physiographic region (McDowell, 1986). Topography is characterized by a low relief plain sitting at elevations between 650 to 850 ft above sea level, which is dissected and incised by Rough River, Meeting Creek, Clifty Creek, and their tributaries to below 500 ft. Swadley (1962) mapped the bedrock geology of the quadrangle, which was later digitized by Conley (2002). Mississippian bedrock is exposed throughout the quadrangle and is cut by several vertical faults in the southeast. The oldest bedrock units include the Beaver Bend and Paoli Limestones, Sample Sandstone, and Reelsville Limestone from oldest to youngest, respectively, and are exposed in the lowest sections of river valleys on the west side of the quadrangle. The Golconda Formation (Beech Creek Limestone, Big Clifty Sandstone, and Haney Limestone Members) is primarily exposed along steep slopes of those same river valleys, which lead up to the top of the plateau. The majority of the broad Mammoth Cave plateau is underlain by Hardinsburg Sandstone with local exposures of Glen Dean Limestone and Leitchfield Formation occurring in the southwest corner of the quadrangle. Previously mapped surficial deposits include scattered areas of alluvium in Meeting Creek, Little Meeting Creek, and Clifty Creek (Swadley, 1962)

Surficial Geologic Map of the Summit 7.5-Minute Quadrangle, Kentucky

The Summit 7.5-minute quadrangle is located south of Louisville and west of Elizabethtown along the boundary between Hardin and Grayson Counties and within the Mississippian Plateau physiographic region (McDowell, 1986). Topography is characterized by the low relief Pennyroyal region that sits at elevations between 560 to 650 ft above sea level, the low relief Mammoth Cave plateau at elevations between 750 to 900 ft, and the steep Dripping Springs escarpment that separates the two plains. Moore (1964) mapped the bedrock geology of the quadrangle, which was later digitized by Conley (2002). Mississippian bedrock is exposed throughout the quadrangle and is cut by several vertical faults. The St. Louis Limestone and overlying Ste. Genevieve Limestone underlie the Pennyroyal region and are the oldest bedrock units in the quadrangle. The Beaver Bend and Paoli Limestones, Sample Sandstone, Reelsville Limestone, and Beech Creek Limestone Member of the Golconda Formation are exposed along the Dripping Springs escarpment. The Mammoth Cave plateau region is underlain by the Big Clifty Sandstone and, locally, Haney Limestone Members of the Golconda Formation east of the Summit Fault, and Hardinsburg Sandstone west of the fault. Previously mapped surficial deposits include minor areas of alluvium in tributaries across the Summit quadrangle, and areas of “slumped sandstone” (colluvium) in the Pennyroyal region (Moore, 1964)

Surficial Geologic Map of the Millerstown 7.5-Minute Quadrangle, Kentucky

The Millerstown 7.5-minute quadrangle is located south of Louisville and southwest of Elizabethtown along the boundaries between Hardin, Grayson, and Hart Counties and within the Mississippian Plateau physiographic region (McDowell, 1986). Topography is characterized by the low relief Pennyroyal plain that sits at altitudes below about 650 ft above sea level, the low relief Mammoth Cave plateau at altitudes above about 650 ft, and steep slopes of and isolated knobs of the incised Dripping Springs escarpment that separates the two plains. Moore (1965) mapped the bedrock geology of the quadrangle, which was later digitized by Johnson (2006). Mississippian bedrock and local areas of Pennsylvanian bedrock are exposed throughout most of the quadrangle, all, of which, are cut by several vertical faults. The Ste. Genevieve Limestone is the oldest lithology and underlies the Pennyroyal region in the northeast and southwest corners of the quadrangle, and locally along the Nolin River. The Beaver Bend Limestone, Mooretown Formation, Paoli Limestone, Sample Sandstone, and Reelsville Limestone stratigraphic sequence underlie most of the remaining Pennyroyal plain and several steep slopes of the Dripping Springs escarpment. The Beech Creek Limestone, Big Clifty Sandstone, and Haney Limestone Members of the Golconda Formation are exposed along the Dripping Springs escarpment the edges of the Mammoth Cave plateau region. Most of the Mammoth Cave plateau is underlain by the Hardinsburg Limestone, and, locally in the southwest corner of the quadrangle, the Glen Dean Limestone, Leitchfield Formation, and Pennsylvanian Caseyville Formation. Previously mapped surficial deposits include minor areas of alluvium in tributaries across the Millerstown quadrangle (Moore, 1964)

Surficial Geologic Map of the Upton 7.5-Minute Quadrangle, Kentucky

The Upton 7.5-minute quadrangle is located south of Elizabethtown along the boundaries between Hardin, Hart, and Larue Counties and within the Mississippian Plateau physiographic region (McDowell, 1986). Topography is characterized by the low relief Pennyroyal plain that sits at altitudes below about 750 ft above sea level, the ridges, spurs, and isolated knobs of the intensely dissected Dripping Springs escarpment; the low relief cap of the escarpment landforms is part of the Mammoth Cave plateau region. Moore (1972) mapped the bedrock geology of the quadrangle, which was later digitized by Toth (2006). Mississippian bedrock is exposed throughout most of the quadrangle and is cut by several northwest-southeast trending vertical faults. The Ste. Genevieve Limestone is the oldest lithology and underlies most of the Pennyroyal region. The Beaver Bend Limestone and Paoli Limestone, Sample Sandstone, and Reelsville Limestone stratigraphic sequence underlie the remaining areas of the Pennyroyal, as well as the lower slopes of the Dripping Spring escarpment. The Beech Creek Limestone, Big Clifty Sandstone, and Haney Limestone Members of the Golconda Formation are exposed along the upper slopes of the Dripping Springs escarpment the upper plains of the Mammoth Cave plateau. The Upper Mississippian Hardinsburg Limestone is exposed on the highest ridges of the Dripping Springs, and the Pennsylvanian Caseyville Formation is locally exposed around the highest peak in the southern part of the Upton quadrangle. Previously mapped surficial deposits include minor areas of alluvium in major tributaries, and “slumped” areas across the quadrangle (Moore, 1972)

ELUM Year 2 report for Work Package 3 - Network of field sites to measure soil C dynamics and GHG emissions. Report V2

This report describes the second year of Work Package 3 (WP3) activities within the ETI’s Ecosystem Land Use Modelling Project (“ELUM”). It expands upon information reported in the first year and provides a forward look to WP3 activities for the remainder of the project. The soil C (carbon) and GHG (Greenhouse Gas) measurements recorded as part of WP3 are required to help reduce the uncertainty associated with the sustainability of bioenergy crop deployment across the UK. This data will be used to parameterise and test the underlying process models in the WP4 modelling work, as part of the development of the over-arching meta-model. A full review of all the data collected across the WP3 network sites will be reported in the D3.5 deliverable due in May 2014. Progress with the development and testing of novel methods for GHG measurement is also included in this report; these could offer means of improving monitoring resolution, thereby enhancing the collection of GHG flux data. A complete review of this work will follow in May 2014 with the D3.4 deliverable

Chronosequence methodology approaches in literature, including specific recommendations for sampling for ELUM. Report V1.1

This report presents a critical review of paired site and chronosequence approaches in the literature and provides specific sampling recommendations and a UK sampling roadmap for the Ecosystem Land-Use Modelling project (ELUM). It looks beyond bioenergy plantations to uncover the best practices to determine the effects of Land Use Change (LUC) on soil carbon stocks. Work Package 2 (WP2) will adopt these approaches in the context of the most relevant bioenergy transitions across the UK. Consequently, there is a need to consider the criteria for achieving valid and robust comparisons of LUC, changes in the spatial variability of soil carbon and other soil properties during LUC, and how these relate to UK-relevant bioenergy transitions. The findings from this review will inform the development of a statistically robust sampling framework to meet the assumptions of paired site and chronosequence approaches. Paired site and chronosequence soil sampling will now commence on the range of identified fieldsites across the UK in line with our sampling roadmap and developed methodologies. The review begins with a brief background to the project, including an overview of the importance of LUC to soil carbon and the sustainability of bioenergy transitions, and the specific objectives of Work Package 2 (Section 1). The assumptions behind paired site and chronosequence approaches and the need to represent key soil types and climatic zones are then discussed in the context of achieving valid and robust LUC comparisons (Section 2). Paired site and chronosequence approaches have been used extensively by others to examine changes in soil carbon, particularly when considering longer-term changes. An overview of technical issues associated with changes in the spatial variability of soil properties across LUC transitions is presented (Section 3). Firstly, it deals with issues associated with horizontal variability and discusses sampling strategies that may be used to account for such differences between bioenergy land uses. Secondly, it examines issues associated with changes in vertical strata and sampling depth, and in particular, appraises several methods available to account for bulk density changes and their effect on soil carbon measurements. A summary of the sampling approaches used by others is provided in two graphs. Section 4 considers the potential bioenergy LUC transitions that may occur in the UK and outlines soil changes likely to be important in those transitions most relevant in the UK. A summary of the key findings from the review and associated specific recommendations for WP2 sampling is provided in Sections 5 and 6, respectively. The most important of these is the need to adopt a paired site and chronosequence approach to examine transitions to bioenergy crops. Furthermore, these approaches need to adopt a hierarchical spatial soil sampling strategy, must include samples up to 1 m depth, and must quantify soil carbon stocks on a cumulative and/or equivalent soil mass per unit area basis. These key findings and recommendations are presented in the context of a pilot study which was conducted during Q3 2011 to test different spatial sampling strategies (Appendix I). Finally, in Appendix II we provide an overview of our year 1 sampling roadmap for Work Package 2