How biotic, abiotic, and functional variables drive belowground soil carbon stocks along stress gradient in the Sundarbans Mangrove Forest?. (1st July 2023)

• Record Type: Journal Article
• Authors: Ahmed, Shamim; Sarker, Swapan Kumar; Kamruzzaman, Md; Ema, Juthika Afneen; Saagulo Naabeh, Clement Sullibie; Cudjoe, Eric; Chowdhury, Faqrul Islam; Pretzsch, Hans
• Is Part Of: Journal of environmental management. Volume 337(2023)
• Publication Date: 2023-07-01
• Subjects: Canopy packing -- Forest growth -- Forest structure -- Nutrients -- Root carbon -- Salinity gradients -- Soil organic carbon; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2023.117772
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Mangrove forests, some of the most carbon-dense ecosystems on Earth, play an important role in climate change mitigation through storing carbon in the soil. However, increasing anthropogenic pressures and sea level rise are likely to alter mangrove forest structure and functions, including the major source of carbon in mangrove ecosystems — below-ground soil carbon stocks (BSCS). Although estimating soil carbon stocks has been a popular practice in the mangroves, but poorly understood the (I) the linkage between BSCS and key ecosystem drivers (i.e., biotic, abiotic, and functional) and in (II) determining the pathways of how BSCS and multiple forest variables interact along stress gradients. This lack of understanding limits our ability to predict ecosystem carbon dynamics under future changes in climate. Here, we aimed to understand how abiotic factors (such as salinity, canopy gap fraction, nutrients, and soil pH), biotic factors (e.g., structural parameters, canopy packing, and leaf area index, LAI), and forest functional variables (e.g., growth and aboveground biomass stocks, AGB) affect BSCS (i.e., soil organic carbon, SOC, and root carbon, RC) using spatiotemporal data collected from the Sundarbans Mangrove Forest (SMF) in Bangladesh. We observed that BSCS decreased significantly with increasing salinity (e.g., from 70.6 Mg C ha −1 in the low-saline zone to 44.6 Mg C ha −1 in the high-saline zone). In contrast, the availability of several macronutrients (such as nitrogen, phosphorous, and potassium), LAI, species diversity, AGB, and growth showed a significant positive effect on SOC and RC. Stand properties, including tree height, basal area, density, canopy packing, and structural diversity, had a non-significant but positive impact on RC, while tree height and basal area significantly influenced SOC. Pathway analysis showed that salinity affects BSCS variability directly and indirectly by regulating stand structure and restricting nutrients and forest functions, although basal area, nutrients, and LAI directly enhance RC stocks. Our results indicate that an increase in nutrient content, canopy density, species diversity, and leaf area index can enhance BSCS, as they improve forest functions and contribute to a better understanding of the underlying mechanisms. Graphical abstract: Image 1 Highlights: Belowground carbon stocks (BSCs) have been revealed to be driven by biotic, abiotic, and functional variables. Increasing salinity, gap fraction, and high saline zones negatively affect BSCs. Nutrients, basal area, leaf area index, functional variables positively affect BSCs. Structural diversity and canopy packing may indirectly benefit BSCs.