Leaf mass and leaf area of seedlings under nutrient treatment in a mangrove forest subject to restoration in Veracruz, Mexico (2021)

Data were collected to investigate how nutrient addition influences the relative growth 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. At the end of the experiment, we harvested the seedlings of 6 islets per treatment. Leaves were digitized by taking photos of 15 mature leaves (fully expanded) selected randomly for each seedling. The images were taken at a height of 30 cm above the surface, with a ruler placed next to the samples for scale reference. The area of each leaf was measured by digitizing the leaves with ImageJ version 2 software. Leaf material was weighed on a digital balance.