Abstract
The impacts of coastal reclamation on carbon (C) and nitrogen (N) sinks of coastal wetlands remain unclearly understood. This study was conducted to investigate the alterations of soil organic C and N (SOC and SON) pools following conversion of Phragmites australis salt marsh into fishpond, wheat and rapeseed fields and town construction land through reclamation along Jiangsu coast in eastern China. Coastal reclamation significantly increased stocks of soil total, labile and recalcitrant organic C and N (SLOC, SLON, SROC, and SRON), and concentrations of water-soluble organic C (WSOC), microbial biomass C and N (SMBC and SMBN), cumulative CO2-C mineralization (MINC) following conversion of P. australis salt marsh into fishpond, wheat and rapeseed fields. However, coastal reclamation reduced SOC, SLOC, SROC, SRON, WSOC, SMBC, SMBN, and MINC following conversion of P. australis salt marsh into town construction land. Our results suggest that coastal reclamation affects C and N sinks of coastal wetlands by changing SOC and SON pools size, stability and dynamics changes following conversion of P. australis salt marsh into other land use types. This finding were primarily attributed to alterations in quantity and quality of exogenous materials returning the soil, and soil physiochemical properties as affected by coastal reclamation.
Highlights
Coastal reclamation has become a prevailing and rapid approach to alleviate the constraints of land resources and the increasing need for living space for human beings[1]
The fishpond had the highest soil organic C (SOC), soil organic nitrogen (SON), SROC, SLON, and SRON among land use types (Table 2; Fig. 2), which was mainly attributed to massive organism excrements and partial residual bodies in fishpond which were decomposed and further adsorbed into the sediment, and greatly promoted SOC, SON, SROC, SLON, and SRON accumulation in fishpond (Table 2; Fig. 2)[29,30]
High moisture in wetlands contributes to soil organic matter (SOM) sequestration owing to soil anaerobic environment which is propitious to SOM accumulation for long-term[31]
Summary
Coastal reclamation has become a prevailing and rapid approach to alleviate the constraints of land resources and the increasing need for living space for human beings[1]. A comprehensive understanding of the variations of SLOC (WSOC, MBC, MBN, and MINC), SLON, SROC, as well as SRON, and their driving mechanism following coastal reclamation have important implications for evaluating SOC and SON pools size, stability and dynamics changes in coastal wetlands. We hypothesize that coastal reclamation can alter SLOC, SLON, SROC, and SRON pools through changing soil physiochemical properties as well as exogenous materials entering the soil following conversion of coastal wetlands into aquaculture ponds, farmlands, and town construction lands. We examined concentrations and stocks of SOC, SON, SLOC, SROC, SLON, SRON, recalcitrant indices for C (RIC) and N (RIN), and the concentrations of WSOC, SMBC, SMBN, MINC, as well as soil physiochemical properties (i.e., soil moisture, bulk density, pH and salinity) in coastal reclaimed fishpond, wheat field, rapeseed field, and town construction lands in comparison to adjacent P. australis salt marsh. The objectives of this study were to: (1) evaluate whether the responses of SOC, SON, and various functional organic C and N pools to coastal reclamation would differ among different land use types; (2) which land use type had the greatest SOC and SON accumulation, and the most stable SOC and SON pools, respectively; and (3) identify which important factor could drive the changes in SOC and SON pools size, stability and dynamics following coastal reclamation
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