 |
| Titel |
The variability and environmental drivers of soil respiration in a deciduous forest: A cyclic sampling analysis. |
| VerfasserIn |
Theresa Meacham, Mathew Williams, Andreas Heinemeyer, Edward Eaton, James Morison |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046026
|
|
|
|
|
|
| Zusammenfassung |
| Forests play a critical role in the global carbon (C) cycle as they are an important C sink.
Current predictions of the sequestration of carbon within this sink have large uncertainties,
mainly due to a poor understanding of the individual soil CO2 efflux components and their
environmental responses. Soil respiration (Rs), measured as soil CO2 efflux, is a combination
of both autotrophic and heterotrophic respiration. Rs is often modeled as a single flux
influenced by environmental variables, mainly temperature and moisture, similarly across all
time scales. Recent studies have however shown a tight coupling between above-ground C
assimilation and below-ground respiration from roots and mycorrhizas. Analysis of the
co-variation between Rs, environmental variables and plant productivity at a high spatial
frequency is therefore needed to understand which processes and environmental factors
control its component fluxes. This information can then be incorporated into ecosystem C
models to test and improve model formulations of soil C turnover. We investigated if and
when Rs is predominantly controlled by plant productivity versus environmental
drivers, with a study carried out in a mature oak forest in southern England during
2009-2010.
Three 21m x 21 m cyclic sampling plots consisting of 64 permanent sample points,
separated by 1 m, 2 m and 4 m distances were established in the forest. Within each plot,
the location of each woody plant >5 cm DBH was surveyed and the herbaceous
understory vegetation fully characterised. At each point, measurements of Rs, soil
temperature, soil moisture, leaf litter depth and leaf area index were made at three-monthly
intervals over one year. At the end of the survey, dry mass of coarse and fine roots in
the top 5 cm soil layer was measured for each point. Temporal patterns of rooting
density were measured using rhizotrons and ingrowth cores adjacent to the plots. As a
control, Rs flux measurements were compared with those taken at the same time by
automatic mesh collar chambers, which separated autotrophic from heterotrophic
fluxes.
Forest Rs fluxes were highest during summer months when rooting density was greatest.
Larger Rs fluxes were noted in areas of greater litter depth and furrow areas with a deep
organic layer. The average Rs flux measurements taken manually but infrequently over a
dense network were consistently higher than those taken with the automated chambers with
much fewer samples in space, but many more in time; but this could reflect a measurement
artefact due to higher soil disturbance. Multivariate statistics have been used to
assess which of the measured factors best explained soil Rs and semivariograms
assess the statistical difference between data points according to their separation
distance. This dataset provides a novel insight into the control of Rs by environmental
drivers and plant productivity at different spatial scales, over the course of a season. |
|
|
|
|
|
|