TY - JOUR

T1 - Conversion of coastal marshes to croplands decreases organic carbon but increases inorganic carbon in saline soils

AU - Zhu, Yuanshan

AU - Wang, Yidong

AU - Guo, Changcheng

AU - Xue, Dongmei

AU - Li, Jun

AU - Chen, Qing

AU - Song, Zhaoliang

AU - Lou, Yilai

AU - Kuzyakov, Yakov

AU - Wang, Zhong-Liang

AU - Jones, Davey L.

N1 - National Natural Science Foundation of China. Grant Numbers: 31300381, 31570523, 41930862 Central Public‐interest Scientific Institution Basal Research Fund. Grant Number: BSRF201715

PY - 2020/5/30

Y1 - 2020/5/30

N2 - Over the past century, conversion to agriculture has greatly reduced the global extent of coastal wetlands leading to degradation and loss of these ecosystems. However, it remains unclear how this land conversion affects the confluent soil organic and inorganic carbon (SOC and SIC) storage as well as their localizations in soil matrix. Here, we investigated these issues using wet sieving at two coastal saline–alkali sites in northern China. Conversion of marshes to cropland (>60 years) decreased the portion of large macroaggregates (>2 mm) and correspondingly increased the portion of microaggregates (0.053–0.25 mm) at both sites. Land conversion decreased SOC contents by 31–67% in all fractions (>2, 0.25–2, 0.053–0.25, and <0.053 mm) in the topsoil (0–15 cm) and subsoil (15–30 cm). In contrast, irrigation‐ and NH4HCO3 fertilization‐derived carbonates increased SIC storages in almost all fractions due to the saline–alkali soil conditions, especially for the subsoil. This increases in SIC almost offset and compensate for the SOC losses at both sites. Consequently, the irrigation‐ and NH4HCO3‐induced SIC accumulation should be included in the full C balance of saline–alkali soils. It should be noted, however, that the progressive loss of SOC due to cultivation will lead to soil degradation in fertility and ecological function, thereby hampering long‐term sustainability of coastal ecosystems. Therefore, the compensation of SIC for the loss of SOC is not sustainable in the longer term.

AB - Over the past century, conversion to agriculture has greatly reduced the global extent of coastal wetlands leading to degradation and loss of these ecosystems. However, it remains unclear how this land conversion affects the confluent soil organic and inorganic carbon (SOC and SIC) storage as well as their localizations in soil matrix. Here, we investigated these issues using wet sieving at two coastal saline–alkali sites in northern China. Conversion of marshes to cropland (>60 years) decreased the portion of large macroaggregates (>2 mm) and correspondingly increased the portion of microaggregates (0.053–0.25 mm) at both sites. Land conversion decreased SOC contents by 31–67% in all fractions (>2, 0.25–2, 0.053–0.25, and <0.053 mm) in the topsoil (0–15 cm) and subsoil (15–30 cm). In contrast, irrigation‐ and NH4HCO3 fertilization‐derived carbonates increased SIC storages in almost all fractions due to the saline–alkali soil conditions, especially for the subsoil. This increases in SIC almost offset and compensate for the SOC losses at both sites. Consequently, the irrigation‐ and NH4HCO3‐induced SIC accumulation should be included in the full C balance of saline–alkali soils. It should be noted, however, that the progressive loss of SOC due to cultivation will lead to soil degradation in fertility and ecological function, thereby hampering long‐term sustainability of coastal ecosystems. Therefore, the compensation of SIC for the loss of SOC is not sustainable in the longer term.

KW - coastal wetland

KW - soil aggregation

KW - soil inorganic carbon

KW - soil organic matter

KW - wetland degradation

U2 - 10.1002/ldr.3538

DO - 10.1002/ldr.3538

M3 - Article

VL - 31

SP - 1099

EP - 1109

JO - Land Degradation and Development

JF - Land Degradation and Development

SN - 1085-3278

IS - 9

ER -