ARS | Publication request: Quantification of net annual C input in terrestrial ecosystems of the Italian Peninsula under different land-uses

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 10, 2009
Publication Date: July 1, 2009
Citation: Inglima, I., Papale, D., Lecain, D.R., Miglietta, F., Cotrufo, M. 2009. Quantification of net annual C input in terrestrial ecosystems of the Italian Peninsula under different land-uses. Meeting Abstract.

Technical Abstract: Soil organic matter (SOM) is a very important compartment of the biosphere: it represents the largest dynamic carbon (C) pool where the C is stored for the longest time period. Root inputs, as exudates and root slush, represent a major, where not the largest, annual contribution to soil C input. Root C input has generally turn-over times of few days; however a fraction of it can be stabilized in the SOM on the long-term. Despite, root growth and exchange may constitute the fate of the largest part of C assimilated by vegetation; the correct measuring method of belowground net annual C input is a still object of discussion. The objective of the present study is to estimate net annual belowground C inputs in a range of ecosystem under different climates, land uses and vegetation types, in the Italian peninsula. This information is very important to constrain ecosystem C balance measured by Eddy covariance, and to accurately quantify the contribution of belowground C input to soil carbon sequestration. Isotope mass balance was used to measure net annual soil C input from roots. In the autumn of 2006, C4 soil ('13C ˜ -17‰) cores were implanted in 10 ecosystems characterized by C3 vegetation ('13C ˜ -26‰) of different types and land-use. Cores were incubated in the field for one year, before being sampled and total C and 13C in each core analysed, by depth intervals. Cores were 30 cm high and 4 cm in diameter, and made of a PVC net of 2 mm mesh size to allow the ingrowth of only fine roots, which are the most metabolically active. Net annual C input ranged from 750 to 200 g C/m2 in forest ecosystems, from 590 to 120 g C/m2 in Macchia ecosystems and from 418 to 274 g C/m2 in grassland. Generally below-ground C input is higher in the upper soil layer (0-15 cm) than in the lower one (15-30 cm), according with the relative density of fine roots. The relative contribution of new C was the highest in forest ecosystem, where it accounted for 0.11-0.38 % of total soil C. Our approach does not allow to determine whether this new C correspond to a net sequestration of C to the soil or if it C replacing existing one. Comparison of this data with data on ecosystem C balance measured by Eddy covariance at the sites will allow answering to this question.