Agriculture, Ecosystems and Environment 363 (2024) 108874 Available online 12 January 2024 0167-8809/© 2023 Elsevier B.V. All rights reserved. Latitudinal responses of wetland soil nitrogen pools to plant invasion and subsequent aquaculture reclamation along the southeastern coast of China Lishan Tan a, b , Ping Yang a, b, c, d, * , Xiao Lin b, d , Yongxin Lin a, b , Linhai Zhang b, c, d , Chuan Tong b, c, d , Yan Hong b , Derrick Y.F. Lai e, ** , Kam W. Tang f, ** a Fujian Provincial Key Laboratory for Subtropical Resources and Environment, Fujian Normal University, Fuzhou 350117, PR China b School of Geographical Sciences, Fujian Normal University, Fuzhou, 350007, PR China c Key Laboratory of Humid Subtropical Eco-geographical Process of Ministry of Education, Fujian Normal University, Fuzhou 350007, PR China d Wetland Ecosystem Research Station of Minjiang Estuary, National Forestry and Grassland Administration, Fuzhou 350215, PR China e Department of Geography and Resource Management, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR China f Department of Biosciences, Swansea University, Swansea SA2 8PP, UK A R T I C L E INFO Keywords: Soil organic nitrogen (SON) Soil inorganic nitrogen (SIN) Exotic invasive plants Aquaculture reclamation ABSTRACT The impact of invasive species and land use change on soil nitrogen pools in coastal wetlands has been reported at local scale, but uncertainty persists for regional pattern due to geographical variability and limited feld data. This study measured the top soil (upper 20 cm) organic nitrogen (SON), inorganic nitrogen (SIN) and total ni- trogen (STN) concentrations and stocks across 21 coastal wetland sites in China (20 ◦ 42′ N-31 ◦ 51′ N) that had undergone the same sequence of transformation from mudfats (MFs) to invasive Spartina alternifora marshes (SAs) then to earthen aquaculture ponds (APs). Results showed that the conversion of MF to SA signifcantly increased SON and SIN concentrations and stocks by 37.7–86.1%, but subsequent conversion to APs signifcantly decreased them by 13.5–34.6%. SON/SIN ratio decreased upon invasion by S. alternifora and it had a negative effect on STN accumulation, whereas conversion of SAs to APs showed the opposite trends. The change rates of SON, SIN and STN stocks showed clear decreasing trends with increasing latitude in the MF-to-SA conversion scenario, refecting the strong infuence of environmental temperatures, but weaker or insignifcant trends were observed in the SA-to-AP conversion scenario, likely because of mitigating anthropogenic activities in aqua- culture ponds. Our fndings can be used to inform strategies to control invasive species and reduce the green- house gas nitrous oxide (N 2 O) emissions, and support global N model for climate change in response to habitat modifcations in coastal wetlands. 1. Introduction Coastal wetlands consist of mudfats, salt marshes, mangroves or seagrass beds (Duarte et al., 2013; Mcleod et al., 2011), and they are important carbon and nitrogen pools (Reddy and DeLaune, 2008; Xu et al., 2020) thanks to their high primary productivity, high sediment accretion rate, and low decomposition rate (Mcleod et al., 2011; Neu- bauer and Megonigal, 2021; Xu et al., 2020). Land-use change and exotic species invasion have impacted coastal wetlands world-wide (Murray et al., 2019; Tan et al., 2022; Wang et al., 2023a). During the past century, over 21% natural coastal wetlands have been lost or degraded globally as a result of land use change to support population growth and economic development (Davidson and Finlyson, 2018; Han et al., 2014; Fluet-Chouinard et al., 2023). Alteration of plant community through invasion or de-vegetation would change the primary production and the rate of organic deposition into the soil (Ge et al., 2015; Wang et al., 2023b), while corresponding changes to the soil microbial community would affect organic remineralization rate (Bahram et al., 2022; Yang et al., 2022a, 2023). Land conversion to aquaculture ponds also changes soil particle size and creates a continuously water-logged environment, and the aquaculture operation itself may introduce additional distur- bances to soil chemistry, e.g. by adding fertilizer and organic wastes (Kauffman et al., 2018; Yang et al., 2021). Many coastal areas in China have undergone a sequence of habitat * Corresponding author at: Fujian Provincial Key Laboratory for Subtropical Resources and Environment, Fujian Normal University, Fuzhou 350117, PR China. ** Corresponding authors. E-mail addresses: yangping528@sina.cn (P. Yang), dyfai@cuhk.edu.hk (D.Y.F. Lai), k.w.tang@swansea.ac.uk (K.W. Tang). Contents lists available at ScienceDirect Agriculture, Ecosystems and Environment journal homepage: www.elsevier.com/locate/agee https://doi.org/10.1016/j.agee.2023.108874 Received 16 October 2023; Received in revised form 5 December 2023; Accepted 22 December 2023