Variation of above-ground tree biomass and soil carbon stocks across neotropical forest types

Neotropical forests encompass a diverse array of forest types, each with distinct structures and species compositions shaped by varying soil and climate conditions. Despite their global importance in carbon (C) cycling, their diversity is underrepresented in Earth system models due to our limited understanding of the abiotic and biotic factors influencing above-ground carbon (AGC) and soil organic carbon (SOC) stocks. We conducted a forest inventory across five neotropical forest types—cloud forest (CF), transition forest (TF), riparian forest (RF), pine-oak forest (POF), and tropical dry forest (TDF)—in Nicaragua's Miraflor-Moropotente Protected Landscape (MMPL) to explore these relationships. Across 40 plots, we identified 4,495 trees belonging to 239 species and 62 families, with Fabaceae being the most species-rich. RF exhibited the highest alpha diversity, followed by CF, TF, and TDF, while POF had the lowest. C stocks varied significantly among forest types, averaging 147.8 ​Mg ​C·ha⁻¹ for AGC and 46.3 ​Mg ​C·ha⁻¹ for SOC. RF and CF stored the most AGC, while TF had the highest SOC. AGC correlated strongly with basal area, species richness, and climatic factors such as precipitation and temperature, while SOC was primarily influenced by soil chemical properties (e.g., total nitrogen, pH) and precipitation. Notably, no significant relationship was found between SOC and AGC. Our C mapping estimated ~3,700 ​Gg of C in the MMPL, with TDF covering the largest area and contributing most to AGC. However, RF and CF, despite occupying smaller areas, harbored the highest species richness and disproportionately contributed to AGC. These findings highlight the need to treat the different neotropical forest types as distinct ecosystems and prioritize the conservation and expansion of endangered cloud and RF across the Neotropics.