Wirth, S. und Hoffmann, M. und Beßler, H. und Engels, C. und Jochheim, H. und Sommer, M. und Augustin, J.
(2017)
Combining a root exclusion technique with continuous measurements of CO2 by chambers and inside soil for a pin-point separation of ecosystem respiration in croplands.
In: Jahrestagung der DBG 2017: Horizonte des Bodens, 02.-07.09.2017, Göttingen.
Kurzfassung
To better assess ecosystem C budgets of croplands and understand their potential response to climate and management changes, detailed information on the mechanisms and environmental controls driving the individual C flux components are needed. This accounts in particular for the ecosystem respiration (Reco) and its components, the autotrophic (Ra) and heterotrophic respiration (Rh) which vary tremendously in time and space. Therefore, we developed and tested a method to separate Reco into Ra (as the sum of Ra (shoot) and Ra (root)) and Rh in order to detect temporal and small-scale spatial dynamics within their relative contribution to overall Reco. Investigations were carried out for winter wheat (Triticum aestivum) during the crop season 2015 at an experimental plot (CarboZALF-D) located in the hummocky ground moraine landscape of NE Germany. Reco was derived from CO2 flux measurements from plant stand and soil during nighttime using automatic chambers. Rh was derived from CO2 efflux measurements from fallow next to the automatic chambers using CO2 sampling tubes in 10 cm soil depth. Ra (root) was calculated as the difference between CO2 efflux measurements in planted soil and Rh. Ra (shoot) was calculated as Reco - Ra (root) - Rh. Reco varied seasonally from <1 to 9.5 g C m-2 d-1, and was higher in adult (a) and reproductive (r) than juvenile (j) stands (g C m-2 d-1: j 1.2, a 4.6, r 5.3). Observed Ra and Rh were in general smaller compared to the independently measured Reco, contributing in average 56 % and 44 % to Reco. However, both varied strongly regarding their environmental drivers and particular contribution throughout the study period, following the seasonal development of soil temperature and moisture (Rh) as well as crop development (Ra). Thus, our results consistently revealed temporal dynamics regarding the relative contribution of Ra (root) and Ra (shoot) to Ra, as well as of Ra and Rh to Reco. Based on the observed results, implications for partitioning of Reco in croplands are given, which requires a spatial and temporal pin-point approach to increase reliability.
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