Soil nutrients in islets under nutrient treatment in a mangrove forest subject to ecohydrological restoration in Tampamachoco, Veracruz, Mexico (2021).

Data were collected to investigate how nutrient addition influences the relative growth, folivory and leaf nutrients content of black mangrove (Avicennia germinans) seedlings in a mangrove area subject to ecological restoration. To address this objective, nitrogen (N) and phosphorus (P) fertilization experiments were carried out in newly formed soils created through artificial terrain elevation in degraded areas targeted for mangrove recovery. Soil relative level modification involved creating circular elevated areas with a relative height of 30 cm and a diameter of 5 m. These structures, designed to mitigate soil collapse and promote propagule anchorage, having a similar soil elevation compared to a conserved reference mangrove sites, formed distinct 'islets' within the dead mangrove zone. A total of 30 islets were randomly selected, and in 10 of these, one of three possible fertilization treatments was applied. The fertilization treatments were: N as granular urea (NH4, 46 - 0 - 0), P as triple superphosphate (P2O5, 0 - 46 -0), and a control (no fertilizer). We applied nitrogen (N) or phosphorus (P) fertilizer in two doses of 75 g in February and May 2021, respectively. We sampled soil cores two months after the second dose of fertilizer was applied (July 2021) to determine the total nitrogen (N) and phosphorus (P) content. Soil cores were sampled in the fertilizer application area using a 50 cm long and 1.9 cm diameter corer. The core was separated into 10 cm depth intervals (0 - 10, 10 -20, and 20 - 30 cm) and stored in a plastic bag for later analysis. Soil samples were dried at room temperature in the laboratory and then finely ground