Soil organic carbon dynamics in dry tropics: impact of tree plantations on restoration of urban degraded lands

Abstract

Restoring urban degraded abandoned land (UDL) is a major global environmental concern. The plantation of different trees on UDL has been advocated as sustainable and efficient restoration strategy, however, their impact on carbon dynamics across the soil profile in dry tropics is least studied. The present study was designed to investigate the soil organic carbon (SOC) dynamics in terms of major labile carbon fractions (LCFs) and stable carbon fractions (SCFs) as well as soil carbon indices, i.e., carbon pool management index (CPMI) in response to three economically important tree plantations, viz., Terminalia arjuna (TAP), Eucalyptus citriodora (ECP), and Tectona grandis (TGP) and agroecosystem (AG) grown on urban degraded abandoned grassland (DG) across the soil profile in dry tropics. In upper soil depth (0–30 cm) across all the land use types (LUT), the SOC content and LCFs, viz., permanganate oxidizable carbon (POX-C), water-extractable organic carbon (WEOC) and microbial biomass carbon (MBC), as well as the SCFs, i.e. humic acid (HA) and fulvic acid (FA), were highest in TAP, followed in decreasing order by ECP, TGP, and DG and lowest in AG. In the middle (30–60 cm) and lower depths (60–90 cm), SOC and SCFs showed a similar pattern to that of upper depth. However, MBC and WEOC were higher in TGP than in ECP. SOC content and all carbon fractions decreased with soil depth. LCFs were found to be more sensitive to LUT, while the SCFs to soil depth. Soil carbon indices followed a similar trend to that of SOC content across the LUTs and soil depths. LUT had a greater influence on soil carbon indices than soil depths. Higher CPMI in tree plantations especially TAP, indicated the restoration potential of trees and lower CPMI in AG suggested a stage of degradation. TAP may be recommended for inclusion in the long-term sustainable restoration strategies of DG. © The Author(s) under exclusive licence to Society for Environmental Sustainability 2025.