A DNA metasystematic approach to forest restoration in the Northern Zone of Costa Rica
Tropical secondary forest developments have exhibited multiple successional trajectories resulting in different outcomes of forest restoration. However, the mechanisms involved in this are still not well known, particularly so for the soil bacterial and fungal communities that develop under these altered land-use conditions. Soil bacteria and fungi are recognized as important components of soil ecosystems, often driving changes and patterns in global biogeochemical cycling, yet there is still much to be explored of these soil biotic communities in tropical secondary forests. As such, the role various soil abiotic properties that may drive soil bacterial and fungal community composition across landscapes and across local-scales, warrants investigation. This thesis addresses some of the mechanisms of how and which soil abiotic factors may have a strong role in determining the soil bacterial and fungal community composition across secondary forest succession in the Maquenque National Wildlife Refuge (MNWR) of Costa Rica. In chapter one, I show that the differences in land-use and differences in soil nutrient factors has mostly affected the soil microbial community composition. Moreover, I show that the soil microbial biomass C and soil fungal community composition were driven by soil NO3-. This chapter highlights the role that soil inorganic N may be playing for secondary forest regeneration. In chapter two, I demonstrate that two target tree species studied (Pentaclethra macroloba and Dipteryx panamensis) had unique soil-microbiomes and certain soil abiotic properties. This chapter also shows the soil microbial biomass C, and the soil microbial community composition were driven by soil NH4+. The third chapter shows that as the P. macroloba tree grows and develops, its soil microbiome will also change, within a primary forest and within a 23-year-old secondary forest. This chapter also demonstrates that the soil bacterial microbiomes of P. macroloba trees can become similar even in when developed in contrasting past land-use histories, yet, it may take more time for the soil fungal community composition to become more similar under these conditions. Collectively, this dissertation research deepens our mechanistic understanding of some of the unexplained stochasticity across secondary succession in the Maquenque National Wildlife Refuge of Costa Rica.