TY - JOUR

T1 - Fate of rice shoot and root residues, rhizodeposits, and microbe-assimilated carbon in paddy soil - Part 1: Decomposition and priming effect

AU - Zhu, Zhenke

AU - Zeng, Guanjun

AU - Ge, Tida

AU - Hu, Yajun

AU - Tong, Chengli

AU - Shibistova, Olga

AU - He, Xinhua

AU - Wang, Juan

AU - Guggenberger, Georg

AU - Wu, Jinshui

N1 - Funding information: The present study was supported by the National Natural Science Foundation of China (41430860, 41371304), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB15020401), the Open Foundation of Key Laboratory of Agro-ecological Processes in Subtropical Region, the Chinese Academy of Sciences Institute of Subtropical Agriculture (ISA2015101), and the Recruitment Program of High-End Foreign Experts of the State Administration of Foreign Experts Affairs, awarded to Georg Guggenberger (GDT20154300073).

PY - 2016/8/11

Y1 - 2016/8/11

N2 - The input of recently photosynthesized C has significant implications on soil organic C sequestration, and in paddy soils, both plants and soil microbes contribute to the overall C input. In the present study, we investigated the fate and priming effect of organic C from different sources by conducting a 300-day incubation study with four different 13C-labelled substrates: rice shoots (shoot-C), rice roots (root-C), rice rhizodeposits (rhizo-C), and microbe-assimilated C (micro-C). The efflux of both 13CO2 and 13CH4 indicated that the mineralization of C in shoot-C-, root-C-, rhizo-C-, and micro-C-treated soils rapidly increased at the beginning of the incubation and decreased gradually afterwards. The highest cumulative C mineralization was observed in root-C-treated soil (45.4%), followed by shoot-C- (31.9%), rhizo-C- (7.90%), and micro-C-treated (7.70%) soils, which corresponded with mean residence times of 39.5, 50.3, 66.2, and 195 days, respectively. Shoot and root addition increased C emission from native soil organic carbon (SOC), up to 11.4 and 2.3 times higher than that of the control soil by day 20, and decreased thereafter. Throughout the incubation period, the priming effect of shoot-C on CO2 and CH4 emission was strongly positive; however, root-C did not exhibit a significant positive priming effect. Although the total C contents of rhizo-C-(1.89%) and micro-C-treated soils (1.90%) were higher than those of untreated soil (1.81%), no significant differences in cumulative C emissions were observed. Given that about 0.3 and 0.1% of the cumulative C emission were derived from labelled rhizo-C and micro-C, we concluded that the soil organic C-derived emissions were lower in rhizo-C- and micro-C-treated soils than in untreated soil. This indicates that rhizodeposits and microbe-assimilated C could be used to reduce the mineralization of native SOC and to effectively improve soil C sequestration. The contrasting behaviour of the different photosynthesized C substrates suggests that recycling rice roots in paddies is more beneficial than recycling shoots and demonstrates the importance of increasing rhizodeposits and microbe-assimilated C in paddy soils via nutrient management.

AB - The input of recently photosynthesized C has significant implications on soil organic C sequestration, and in paddy soils, both plants and soil microbes contribute to the overall C input. In the present study, we investigated the fate and priming effect of organic C from different sources by conducting a 300-day incubation study with four different 13C-labelled substrates: rice shoots (shoot-C), rice roots (root-C), rice rhizodeposits (rhizo-C), and microbe-assimilated C (micro-C). The efflux of both 13CO2 and 13CH4 indicated that the mineralization of C in shoot-C-, root-C-, rhizo-C-, and micro-C-treated soils rapidly increased at the beginning of the incubation and decreased gradually afterwards. The highest cumulative C mineralization was observed in root-C-treated soil (45.4%), followed by shoot-C- (31.9%), rhizo-C- (7.90%), and micro-C-treated (7.70%) soils, which corresponded with mean residence times of 39.5, 50.3, 66.2, and 195 days, respectively. Shoot and root addition increased C emission from native soil organic carbon (SOC), up to 11.4 and 2.3 times higher than that of the control soil by day 20, and decreased thereafter. Throughout the incubation period, the priming effect of shoot-C on CO2 and CH4 emission was strongly positive; however, root-C did not exhibit a significant positive priming effect. Although the total C contents of rhizo-C-(1.89%) and micro-C-treated soils (1.90%) were higher than those of untreated soil (1.81%), no significant differences in cumulative C emissions were observed. Given that about 0.3 and 0.1% of the cumulative C emission were derived from labelled rhizo-C and micro-C, we concluded that the soil organic C-derived emissions were lower in rhizo-C- and micro-C-treated soils than in untreated soil. This indicates that rhizodeposits and microbe-assimilated C could be used to reduce the mineralization of native SOC and to effectively improve soil C sequestration. The contrasting behaviour of the different photosynthesized C substrates suggests that recycling rice roots in paddies is more beneficial than recycling shoots and demonstrates the importance of increasing rhizodeposits and microbe-assimilated C in paddy soils via nutrient management.

UR - http://www.scopus.com/inward/record.url?scp=84982190161&partnerID=8YFLogxK

U2 - 10.5194/bg-13-4481-2016

DO - 10.5194/bg-13-4481-2016

M3 - Article

AN - SCOPUS:84982190161

VL - 13

SP - 4481

EP - 4489

JO - BIOGEOSCIENCES

JF - BIOGEOSCIENCES

SN - 1726-4170

IS - 15

ER -