Impact of 40 years poplar cultivation on soil carbon stocks and greenhouse gas fluxes

Abstract. Within the JRC Kyoto Experiment in the Regional Park and UN-Biosphere Reserve "Parco Ticino" (North-Italy, near Pavia), the soil carbon stocks and fluxes of CO2, N2O, and CH4 were measured in a poplar plantation in comparison with a natural mesohygrophilous deciduous forest nearby, which represents the pristine land cover of the area. Soil fluxes were measured using the static and dynamic closed chamber techniques for CH4 N2O, and CO2, respectively. We made further a pedological study to relate the spatial variability found with soil parameters. Annual emission fluxes of N2O and CO2 and deposition fluxes of CH4 were calculated for the year 2003 for the poplar plantation and compared to those measured at the natural forest site. N2O emissions at the poplar plantation were 0.15$plusmn;0.1 g N2O m-2 y-1 and the difference to the emissions at the natural forest of 0.07±0.06 g N2O m-2 y-1 are partly due to a period of high emissions after the flooding of the site at the end of 2002. CH4 consumption at the natural forest was twice as large as at the poplar plantation. In comparison to the relict forest, carbon stocks in the soil under the poplar plantation were depleted by 61% of surface (10 cm) carbon and by 25% down the profile under tillage (45 cm). Soil respiration rates were not significant different at both sites with 1608±1053 and 2200±791 g CO2 m-2 y-1 at the poplar plantation and natural forest, respectively, indicating that soil organic carbon is much more stable in the natural forest. In terms of the greenhouse gas budget, the non-CO2 gases contributed minor to the overall soil balance with only 0.9% (N2O) and -0.3% (CH4 of CO2-eq emissions in the natural forest, and 2.7% (N2O) and -0.2% of CO2-eq. emissions in the poplar plantation. The very high spatial variability of soil fluxes within the two sites was related to the morphology of the floodplain area, which was formed by the historic course of the Ticino river and led to a small-scale (tenth of meters) variability in soil texture and to small-scale differences in elevation. Differences of site conditions are reflected by differences of inundation patterns, ecosystem productivity, CO2 and N2O emission rates, and soil contents of carbon and nitrogen. Additional variability was observed during a flooding event and after fertilisation at the poplar site. Despite of this variability, the two sites are comparable as both originate from alluvial deposits. The study shows that changes in soil carbon stocks and related fertility are the most visible phenomena after 40 years of land use change from a pristine forest to a fast growing poplar plantation. Therefore, the conservation and careful management of existing carbon stocks deserves highest priority in the context of the Kyoto Protocol.

[1]  E. Schulze,et al.  Carbon stocks and soil respiration rates during deforestation, grassland use and subsequent Norway spruce afforestation in the Southern Alps, Italy. , 2000, Tree physiology.

[2]  I. Jolliffe.  Principal Component Analysis , 2002 .

[3]  Markus Reichstein,et al.  Modeling temporal and large‐scale spatial variability of soil respiration from soil water availability, temperature and vegetation productivity indices , 2003 .

[4]  L. Verchot,et al.  Methane and Nitrogen Oxide Fluxes in Tropical Agricultural Soils: Sources, Sinks and Mechanisms , 2004 .

[5]  Pete Smith,et al.  Carbon sequestration in the agricultural soils of Europe , 2004 .

[6]  Jürgen Augustin,et al.  Automated Gas Chromatographic System for Rapid Analysis of the Atmospheric Trace Gases Methane, Carbon Dioxide, and Nitrous Oxide , 1997 .

[7]  J. Doran,et al.  Effect of water-filled pore space on carbon dioxide and nitrous oxide production in tilled and nontilled soils [Maize; Illinois; Kentucky; Minnesota; Nebraska] , 1984 .

[8]  K. Dobbie,et al.  The effects of temperature, water‐filled pore space and land use on N2O emissions from an imperfectly drained gleysol , 2001 .

[9]  H. Neue,et al.  The formation of the trace gases NO and N2O in soils by the coupled processes of nitrification and denitrification: results of kinetic 15N tracer investigations , 2000 .

[10]  J. Tenhunen,et al.  Severe drought effects on ecosystem CO2 and H2O fluxes at three Mediterranean evergreen sites: revision of current hypotheses? , 2002 .

[11]  J. Tisdall,et al.  Organic matter and water‐stable aggregates in soils , 1982 .

[12]  D. B. Nedwell,et al.  Methane oxidation in temperate soils: effects of inorganic N , 2004 .

[13]  E. Davidson,et al.  Microbiological basis of NO and N2O production and consumption in soil. , 1989 .

[14]  Ü. Rannik,et al.  Respiration as the main determinant of carbon balance in European forests , 2000, Nature.

[15]  T. Rosswall,et al.  Relationships between soil moisture content and nitrous oxide production during nitrification and denitrification , 1988, Biology and Fertility of Soils.

[16]  D. Keeney,et al.  Nitrous oxide production in aerobic soils under varying pH, temperature and water content , 1984 .

[17]  J. Arah,et al.  Steady-state denitrification in aggregated soils: a mathematical model , 1989 .

[18]  S. Frolking,et al.  N2O emissions from humid tropical agricultural soils: effects of soil moisture, texture and nitrogen availability , 2001 .

[19]  Joanne H. Shorter,et al.  Landfill methane emissions measured by enclosure and atmospheric tracer methods , 1996 .

[20]  Keith A. Smith,et al.  The control of nitrous oxide emissions from agricultural and natural soils , 2000 .

[21]  P. Ciais,et al.  The carbon budget of terrestrial ecosystems at country-scale – a European case study , 2004 .

[22]  Klaus Butterbach-Bahl,et al.  Carbon Sequestration in Arable Soils is Likely to Increase Nitrous Oxide Emissions, Offsetting Reductions in Climate Radiative Forcing , 2005 .

[23]  F. Beese,et al.  Nitrous oxide emission and methane consumption following compaction of forest soils , 2004 .

[24]  P. Ambus,et al.  Measurement of N2O emission from a fertilized grassland: An analysis of spatial variability , 1994 .

[25]  P. Anthoni,et al.  Forest and agricultural land‐use‐dependent CO2 exchange in Thuringia, Germany , 2004 .

[26]  Keith A. Smith,et al.  General CH4 oxidation model and comparisons of CH4 Oxidation in natural and managed systems , 2000 .

[27]  Pete Smith,et al.  Europe's Terrestrial Biosphere Absorbs 7 to 12% of European Anthropogenic CO2 Emissions , 2003, Science.

[28]  T. Granli,et al.  Nitrous oxide from agriculture , 1994 .

[29]  S. Nesbit,et al.  A laboratory study of factors influencing methane uptake by soils , 1992 .

[30]  Ü. Rannik,et al.  Productivity overshadows temperature in determining soil and ecosystem respiration across European forests , 2001 .

[31]  J. Cortez,et al.  Decomposition of mediterranean leaf litters: A microcosm experiment investigating relationships between decomposition rates and litter quality , 1996 .

[32]  M. Aubinet,et al.  Soil CO2 efflux measurements in a mixed forest: impact of chamber disturbances, spatial variability and seasonal evolution , 2000 .

[33]  Pete Smith.  Carbon sequestration in croplands: The potential in Europe and the global context , 2004 .

[34]  Jean-François Ponge,et al.  Classification of forest humus forms: a French proposal , 1995 .

[35]  G. King,et al.  Effects of Temperature on Methane Consumption in a Forest Soil and in Pure Cultures of the Methanotroph Methylomonas rubra , 1992, Applied and environmental microbiology.

[36]  K. Butterbach‐Bahl,et al.  Methane oxidation by soils of an N limited and N fertilized spruce forest in the Black Forest, Germany , 2001 .

[37]  J. Turner,et al.  Change in organic carbon in forest plantation soils in eastern Australia. , 2000 .

[38]  M. Bradford,et al.  Controlling factors and effects of chronic nitrogen and sulphur deposition on methane oxidation in a temperate forest soil , 2001 .

[39]  H. Tiessen,et al.  The role of soil organic matter in sustaining soil fertility , 1994, Nature.

[40]  I. Levin,et al.  Methane consumption in aerated soils of the temperate zone , 1990 .

[41]  D. B. Nedwell,et al.  Effect of tree species on methane and ammonium oxidation capacity in forest soils , 2005 .

[42]  D. Howard,et al.  Carbon storage in forest soils , 1995 .

[43]  Keith A. Smith,et al.  Micrometeorological and chamber methods for measurement of nitrous oxide fluxes between soils and the atmosphere : overview and conclusions , 1994 .

[44]  Christian Körner,et al.  Slow in, Rapid out--Carbon Flux Studies and Kyoto Targets , 2003, Science.

[45]  T. Parkin.  Characterizing the Variability of Soil Denitrification , 1990 .

[46]  Alain Albrecht,et al.  Carbon sequestration in tropical agroforestry systems , 2003 .