Analyzing vegetation cover-induced organic matter mineralization dynamics in sandy soils from tropical dry coastal ecosystems

To gain knowledge about carbon and nitrogen mineralization potentials and their interaction with sandy soil environment in tropical dry coastal ecosystems, we carried out a short-term laboratory incubation experiment. For this, soil surface (0-10 cm) samples were collected from tropical semi-deciduous forest (TSdF), secondary forest (SecF), coastal dune scrub_crest (DS_C), and coastal dune scrub_slack (DS_S). Soil samples were incubated at 25 degrees C with constant soil moisture (at field capacity) for 97 days, and over this time 10 and 11 sampling occasions were analyzed to determine carbon (CO2-C) and nitrogen (NH4+, NO3-) dynamics, respectively. We used a simple exponential model to estimate soil carbon and nitrogen mineralization pools. On average, soil organic carbon mineralization rates ranged between 0.017 and 0.053 mg CO2-C g(-1) soil d(-1) and varied in the following order: DS_S > SecF > TSdF > DS_C. Average net mineralization rates (mg N kg(-1) soil d(-1)) ranged between 16.9 and 18.8 and varied in the following order: SecF > DS_S > TSdF, whereas in DS_C it was -0.44, indicating N immobilization. Co and No represented, on average, 1.08% and 5% of soil organic carbon and total organic nitrogen, respectively. On average, mineralization constants (k) for Co and No were 0.29 d(-1) and 0.23 d(-1), respectively, showing that SOM is easily mineralized. The proportion of NO3-/N-m was very high in SecF (89%) and TSdF (75%), while DS_C showed nitrate immobilization. The increase in NO3-/N-m ratio in SecF could be associated with legume species that have established in the nature restoration (SecF) on ex-grassland. Across all study sites, linear regression analyses suggested that soil physical and chemical properties may regulate SOM mineralization (p < 0.05).