Abstract
The conversion of natural grassland to semi-natural or artificial ecosystems is a large-scale land-use change (LUC) commonly occurring to saline–alkaline land. Conversion of natural to artificial ecosystems, with addition of anthropogenic nitrogen (N) fertilizer, influences N availability in the soil that may result in higher N2O emission along with depletion of 15N, while converting from natural to semi-natural the influence may be small. So, this study assesses the impact of LUC on N2O emission and 15N in N2O emitted from naturally occurring saline–alkaline soil when changing from natural grassland (Phragmites australis) to semi-natural [Tamarix chinensis (Tamarix)] and to cropland (Gossypium spp.). The grassland and Tamarix ecosystems were not subject to any management practice, while the cropland received fertilizer and irrigation. Overall, median N2O flux was significantly different among the ecosystems with the highest from the cropland (25.3 N2O-N µg m−2 h−1), intermediate (8.2 N2O-N µg m−2 h−1) from the Tamarix and the lowest (4.0 N2O-N µg m−2 h−1) from the grassland ecosystem. The 15N isotopic signatures in N2O emitted from the soil were also significantly affected by the LUC with more depleted from cropland (− 25.3 ‰) and less depleted from grassland (− 0.18 ‰). Our results suggested that the conversion of native saline–alkaline grassland with low N to Tamarix or cropland is likely to result in increased soil N2O emission and also contributes significantly to the depletion of the 15N in atmospheric N2O, and the contribution of anthropogenic N addition was found more significant than any other processes.
Highlights
The conversion of natural grassland to semi-natural or artificial ecosystems is a large-scale landuse change (LUC) commonly occurring to saline–alkaline land
Our results indicate that the conversion of natural ecosystems to cropland with the addition of anthropogenic N would greatly contribute to the depletion of the 15N in atmospheric N2O by emitting more depleted 15N in N2O along with higher N2O emission rate, which was according to our hypothesis
Our study showed that LUC from native grassland to Tamarix chinensis (Tamarix) and cropland on saline–alkaline soil significantly influence soil temperature, soil moisture and N H4 and N O3 contents
Summary
The conversion of natural grassland to semi-natural or artificial ecosystems is a large-scale landuse change (LUC) commonly occurring to saline–alkaline land. Our results suggested that the conversion of native saline–alkaline grassland with low N to Tamarix or cropland is likely to result in increased soil N2O emission and contributes significantly to the depletion of the 15N in atmospheric N2O, and the contribution of anthropogenic N addition was found more significant than any other processes. N loss from alkaline soil may be high in total, but if much of the N is lost in the form of N H3 there may be less N H4 available for nitrification and subsequent denitrification This evidence suggests that in naturally occurring saline–alkaline soil, the influence of both salinity and alkalinity may significantly affect the N 2O formation processes. Differences in the capacity to reduce N2O to N2 between various ecosystems may influence the 15N in emitted N2O
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.
