Understanding how conservation tillage promotes soil carbon accumulation: Insights into extracellular enzyme activities and carbon flows between aggregate fractions.
Sci Total Environ
; 897: 165408, 2023 Nov 01.
Article
em En
| MEDLINE
| ID: mdl-37429476
ABSTRACT
Conservation tillage has been shown to mitigate climate change by promoting the sequestration of soil carbon (C) in agroecosystems. However, knowledge on how conservation tillage accumulates soil organic C (SOC), especially at the aggregate scale, remains limited. This study aimed to clarify the effects of conservation tillage on SOC accumulation by measuring hydrolytic and oxidative enzyme activities and C mineralization in aggregates and developing an extended scheme of C flows between aggregate fractions using the 13C natural abundance (δ13C) method. Topsoils (0-10 cm) were sampled from a 21-year tillage experiment located in the Loess Plateau of China. Compared with conventional (CT) and reduced tillage with straw removal (RT), no-till (NT) and subsoiling with straw mulching (SS) enhanced the proportions of macro-aggregates (> 0.25 mm) (by 12-26%) and SOC contents in bulk soils and all aggregate fractions (by 12-53%). In bulk soils and all aggregate fractions, SOC mineralization and the activities of hydrolases (ß-1,4-glucosidase, ß-acetylglucosaminidase, ß-xylosidase, and cellobiohydrolase) and oxidases (peroxidase and phenol oxidase) were 9-35% and 8-56% lower, respectively, under NT and SS than under CT and RT. Partial least squares path model revealed that reductions in the activities of hydrolases and oxidases and increases in macro-aggregation decreased SOC mineralization in bulk soils and macro-aggregates. Furthermore, Δ13C values (aggregate-associated δ13C - bulk-soil δ13C) increased with decreasing size of soil aggregates, suggesting that C is younger in larger aggregates than in smaller aggregates. The probability of C flows from large to small soil aggregates was lower under NT and SS than under CT and RT, indicating that young SOC with low rates of decomposition in macro-aggregates was better protected under NT and SS. Overall, NT and SS enhanced SOC accumulation in macro-aggregates by decreasing the activities of hydrolases and oxidases and C flows from macro- to micro-aggregates, which promoted C sequestration in soils. The present study provides improved insights into the mechanism and prediction of soil C accumulation under conservation tillage.
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Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Solo
/
Carbono
Tipo de estudo:
Prognostic_studies
País/Região como assunto:
Asia
Idioma:
En
Revista:
Sci Total Environ
Ano de publicação:
2023
Tipo de documento:
Article