Leguminous Inga trees are thought to enhance soil carbon (C) accumulation following reforestation, through mostly unknown mechanisms. This study amplified soil DNA using the ITS1F and ITS4 primers for PCR and Illumina MiSeq methods to identify fungal taxa, and traditional C analysis methods to evaluate how planted 4-, 8-, and 11-year-old Inga punctata trees affected soil fungal community compositions and C utilization patterns compared to old-growth I. punctata trees and an adjacent unplanted pasture within the same reforestation zone in Monteverde, Costa Rica. Along the tree age gradient, the planted I. punctata trees enhanced the tree soil C capture capacity, as indicated by increased levels of soil biomass C, Respiration, and efficiency of organic C use (with lower qCO₂ values), and development of increasingly more abundant, stable, and successionally developed fungal communities, including those associated with the decomposition of complex organic C compounds. The level and strength of differences coincided with differences in the time of separation between the pasture and tree age or between the different tree ages. Fungal taxa were also identified as potential indicators of the early and late stages of soil recovery. Thus, planting I. punctata should be part of future reforestation strategies used in this region of the Monteverde Cloud Forest in Costa Rica.

Leguminous Inga trees are thought to enhance soil carbon (C) accumulation following reforestation through mostly unknown mechanisms. This study amplified soil DNA using the ITS1F and ITS4 primers for PCR and Illumina MiSeq methods to identify fungal taxa, and traditional C analysis methods to evaluate how planted 4, 8, 11-year-old, Inga punctata trees affected soil fungal community compositions and C utilization patterns compared to old growth I. punctata trees and adjacent unplanted pasture within the same reforestation zone in Monteverde, Costa Rica. Along the tree age gradient the planted I. punctata trees enhanced the tree soil C-capture capacity as indicated by increased levels of soil Biomass-C, Respiration, and efficiency of organic C use (as lower qCO2 values), and development of increasingly more abundant, stable and successionally developed fungal communities, including those associated with decomposition of complex organic C compounds. The level and strength of differences coincided with differences in time of separation between the pasture and tree age or between the different tree ages. Fungal taxa were also identified as potential indicators of early and late stages of soil recovery. Thus, planting I. punctata should be part of future reforestation strategies used in this region of Costa Rica.

Seedlings of the ecologically important and “critically endangered” tree, Ocotea monteverdensisis, are experiencing high mortality in the cloud forests of Monteverde, Costa Rica at the onset of the wet season, yet no previous work has been conducted to determine the disease etiology. Here, healthy and diseased Plant Root and adjacent Bulk soils were analyzed for total organic carbon and nitrogen (N), respiration, nitrate, and ammonium, and DNA sequence-based bacterial and fungal community composition. All N metric levels were greater in Diseased vs. Healthy Plant Root soils, which could enhance pathogen growth and pathogenic mechanisms. Greater DNA percentages from several potential pathogens were found in Diseased vs. Healthy Plant Root soils, suggesting a root pathogen etiology. The DNA percentage of the fungus Mycosphaerella was present at greater levels in the Diseased Plant Root soils than other potential pathogens (about 11.7% vs. < 3.2%). Mycosphaerella causes similar diseases in other plants, including coffee, often after onset of the wet season. Similarly, the O. monteverdensis disease occurs in seedlings planted within or near former coffee plantations often at wet season onset. Although fungal pure culture isolation and transmission studies are needed, this is the first evidence of a potential etiologic agent of this disease.