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| Titel |
Longevity of contributions to SOC stocks from roots and aboveground plant litter below a Miscanthus plantation |
| VerfasserIn |
Andrew Robertson, Pete Smith, Christian Davies, Emily Bottoms, Niall McNamara |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250073317
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| Zusammenfassung |
| Miscanthus is a lignocellulosic crop that uses the Hatch-Slack (C4) photosynthetic pathway
as opposed to most C3 vegetation native to the UK. Miscanthus can be grown for a number of
practical end-uses but recently interest has increased in its viability as a bioenergy
crop; both providing a renewable source of energy and helping to limit climate
change by improving the carbon (C) budgets associated with energy generation.
Recent studies have shown that Miscanthus plantations may increase stocks of
soil organic carbon (SOC), however the longevity and origin of this ’new’ SOC
must be assessed. Consequently, we combined an input manipulation experiment
with physio-chemical soil fractionation to quantify new SOC and CO2 emissions
from Miscanthus roots, decomposing plant litter and soil individually. Further,
fractionation of SOC from the top 30 cm gave insight into the longevity of that
SOC.
In January 2009 twenty-five 2 m2 plots were set up in a three-year old 11 hectare
Miscanthus plantation in Lincolnshire, UK; with five replicates of five treatments. These
treatments varied plant input to the soil by way of controlled exclusion techniques.
Treatments excluded roots only (“No Roots”), surface litter only (“No Litter”), both roots and
surface litter (”No Roots or Litter”) or had double the litter amount added to the soil surface
(“Double Litter”). A fifth treatment was a control with undisturbed roots and an average
amount of litter added. Monthly measurements of CO2 emissions were taken at the soil
surface from each treatment between March 2009 and March 2013, and soil C from the top
30 cm was monitored in all plots over the same period. Miscanthus-derived SOC was
determined using the isotopic discrimination between C4 plant matter and C3 soil, and soil
fractionation was then used to establish the longevity of that Miscanthus-derived
SOC.
Ongoing results for CO2 emissions indicate a strong seasonal variation; litter
decomposition forms a large portion of the CO2 emissions in winter and spring whereas root
respiration dominates the summer and autumn fluxes. Additionally, the “No Roots or Litter”
and “No Litter” treatments have significantly less Miscanthus-derived C and therefore
significantly less CO2 emitted from decomposing ’new’ C. Results from soil fractionation
concur with these findings and also suggest that most Miscanthus-derived SOC has fairly
short mean residence times within the soil.
We hypothesised that the high C input treatments would stimulate large outputs but also
increase soil C stocks. However, whilst CO2 efflux varies significantly between treatments,
results from the first two years of the experiment do not suggest that any increase in SOC is
significant. Four years of continuous monitoring, chemical and physical soil fractionation and
ecosystem C cycle modelling will allow a more comprehensive analysis of the longevity of
Miscanthus-derived SOC and estimation of SOC stock change with time and plant inputs. |
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