Measuring the rhizodeposition of carbon by rice: an approach based on carbon flux observations

摘要

Rhizodeposition is an important component of carbon cycling in terrestrial ecosystems. However, there remains tremendous uncertainty in its quantification due to the methodological limitations. In the present study, we propose a method to evaluate the rhizodeposition by plants by observing carbon flux. We investigated the ecosystem CO2 flux variability and calculated the rhizodeposition of carbon by the rice rhizosphere, by using the carbon flux, meteorological data, and biomass observation from 2003 to 2011 at the Taoyuan Agro-ecological Experimental Station, a representative subtropical paddy ecosystem. Our data indicated that the process of rhizodeposition is the major reason for the discrepancy between the biomass and net primary productivity of the paddy ecosystem under intensive human interference. Both the amount and ratio of rhizodeposition of carbon in this paddy ecosystem were assessed; this provides important theoretical and methodological support for further investigating rhizodeposition by rice under field conditions. The rhizodeposition amount in the growing season of early rice, late rice, and for the entire planting period was 0.52-2.56, 0.74-3.75, and 1.61-5.24 t ha(-1), respectively, with the corresponding mean (+/- SD) rhizodeposition ratios of 23.16 +/- 8.87%, 28.16 +/- 12.94%, and 27.00 +/- 9.3%. This method enabled us to calculate rhizodeposition under in situ conditions, and the results showed that the growing season of late rice was the primary period for rhizodeposition in rice ecosystem.