Carbon cycling in a Calluna heathland in The Netherlands: Ecosystem development and drought

Albert Tietema1, Gillian Kopittke1, Emiel van Loon1, Karsten Kalbitz1
1 University of Amsterdam

O 2.2 in Environmental controls on fluxes and processes in ecosystems

15.07.2014, 15:50-16:10, H18

In a long term climate change manipulation experiment in an old Calluna heathland, we measured total and heterotrophic soil respiration after fourteen annual droughts. In addition, total and heterotrophic soil respiration were determined in a neighboring chronosequence of heathlands 11, 18 and 28 years after cutting the vegetation. These field measurements of total and heterotrophic soil respiration were modeled to determine annual Carbon (C) losses and to derive autotrophic root respiration C losses. On the basis of these results on respiration in combination with plant growth and photosynthesis measurements, C cycling during ecosystem development and a sequence of annual droughts could be reconstructed.

There were no heterotrophic respiration differences between the community ages. In contrast, autotrophic respiration was significantly greater on the youngest vegetation (55% of total soil respiration in summer) and decreased as the plants aged (oldest vegetation: 37% of total soil respiration in summer). Total annual soil C loss from the youngest community was estimated to be 650 g C m-2 year-1 and 435 g C m-2 year-1 for the oldest community.

The application of repeated droughts resulted in suppression of the total soil C loss from 392 to 332 g C m-2 year-1 in 2010–2011 and from 427 to 358 g C m-2 year-1 in 2011–2012. Heterotrophic respiration was the greatest contributor to heathland soil C loss (74–76%) and this was suppressed when directly exposed to drought conditions, although not significantly reduced on an annual basis. Annual autotrophic respiration was suppressed by 42% (2010–2011) and 45% (2011–2012) under repeated drought, indicating there was a greater effect of the repeated annual drought on roots than on microbes.

Understanding C fluxes from these ecosystems provided information on the C sink and source strength during ecosystem development and droughts, and on the role of the vegetation and the soil in C sequestration.

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Letzte Änderung 31.03.2014