Abstract
Little is known about the effect of perennial biomass crops (PBCs) removal on soil C dynamics. The belowground biomass (BGB) that is composed by plant belowground organs (PBO) such as rhizomes in the herbaceous PBCs and stumps in woody PBCs should be considered, together with fine roots (FR), as a huge input of exogenous organic matter (EOM) that is incorporated into the soil at the reversion. In this study, we mimic the incorporation of BGB of PBCs through a soil-residues incubation under controlled conditions to investigate the effects of adding FR and PBO (at real field rates) on soil C and N mineralization dynamics, and to understand decomposition controlling factors. A modified RothC model version, encompassing a better description of decomposable (DEOM) and resistant (REOM) pools, was fitted to C mineralization curves of respiration measured by CO2 evolution in incubated soil to quantify partitioning factors and decomposition rates of PBCs BGB components. After 1 month, PBO showed higher mineralization rates (498 µg CO2-C gsoil−1) than FR (196 µg CO2-C gsoil−1), with black locust having the highest amount of C respired (38% of added C). The emission peak occurred within 3 days from the beginning of the experiment for PBO and after 1 day for FR. Generally, according to the modified version of RothC model, PBO had higher proportion of REOM than FR, except for black locust. The decomposition constant rates from the optimized RothC model were higher for PBO (kDEOM: 20.9 y−1, kREOM: 12.1 y−1) than FR (kDEOM: 0.4 y−1, kREOM: 0.1 y−1), indicating that FR are less decomposable than PBO. The C/N ratio is not the main controlling factor of decomposition when residue N is not a limiting factor, while the availability of easily decomposable substrates (DEOM/REOM ratio) and cell-wall composition decomposition is a strong predictor of C and N mineralization of these EOM types. The explicit inclusion of crop-specific DEOM/REOM ratios within RothC or a similar soil C model will help to improve the predictions of long-term C sequestration trajectories (half-life > 30 years) associated with PBCs cultivation, especially when dismission of such perennial cropping systems is addressed.
Highlights
Perennial biomass crops (PBCs) are low-input crops with the potential to mitigate climate change by sequestering soil organic carbon (SOC) [1,2] and to sustain the provision of multiple ecosystem services [3,4,5]
The cumulative amount of CO2-C mineralized from plant belowground organs (PBO) after 60 days of incubation was on average 24.2% ranging from 13.8% in the case of giant reed to 38.2% in the case of black locust (Figures 2a and 3a)
The dynamics of mineralization rate of PBO showed a very distinct pattern: black locust showed a sharp peak after about 7 h followed by a steady decrease and by a further lower, but broader, peak with a maximum reached after about 3 days (Figure 3a)
Summary
Perennial biomass crops (PBCs) are low-input crops with the potential to mitigate climate change by sequestering soil organic carbon (SOC) [1,2] and to sustain the provision of multiple ecosystem services [3,4,5]. Martani et al [2] reported, for example, that C sequestered in BGB (18 Mg C ha−1) after 11 y in 0–30 cm soil layer by BGB is almost two times higher than the amount of C sequestered in soil The fate of this C pool after reversion and its impact on SOC-cycling after reversion are still unknown. That the reversion can lead to a fast decrease in soil quality [16], offsetting at least partially the climate benefits of PBCs [9], but the pulse incorporation of BGB in soil has the potential to save C after the reversion [2]. Flow of C (in terms of quantity and quality) through the soil drives soil multifunctionality [20,21], and supports microbially-mediated SOM formation [22,23]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
