Tropical Rainforest Restoration Plantations Are Slow to Restore the Soil Biological and Organic Carbon Characteristics of Old Growth Rainforest

• Published in: Microbial ecology 2020-02, Vol.79 (2), p.432-442
• Main Authors: Bonner, Mark T. L., Allen, Diane E., Brackin, Richard, Smith, Tim E., Lewis, Tom, Shoo, Luke P., Schmidt, Susanne
• Format: Article
• Language: English
• Subjects: Bacteria; Biodiversity; Biomedical and Life Sciences; Carbon; Carbon cycle; Communities; Ecology; Environmental restoration; Forest Science; Forests; Geoecology/Natural Processes; Gram-negative bacteria; Land use; Life Sciences; Markvetenskap; Microbial activity; Microbial Ecology; Microbiology; Microorganisms; Nature Conservation; Old growth; Organic carbon; Organic soils; Pasture; Plantations; Rainforests; Reforestation; Restoration; Skogsvetenskap; Soil; SOIL MICROBIOLOGY; Soil microorganisms; Soil Science; Soils; Statistical analysis; Tropical climate; Water Quality/Water Pollution
• ISSN: 0095-3628; 1432-184X; 1432-184X
• DOI: 10.1007/s00248-019-01414-7

Widespread and continuing losses of tropical old-growth forests imperil global biodiversity and alter global carbon (C) cycling. Soil organic carbon (SOC) typically declines with land use change from old-growth forest, but the underlying mechanisms are poorly understood. Ecological restoration plantations offer an established means of restoring aboveground biomass, structure and diversity of forests, but their capacity to recover the soil microbial community and SOC is unknown due to limited empirical data and consensus on the mechanisms of SOC formation. Here, we examine soil microbial community response and SOC in tropical rainforest restoration plantings, comparing them with the original old-growth forest and the previous land use (pasture). Two decades postreforestation, we found a statistically significant but small increase in SOC in the fast-turnover particulate C fraction. Although the δ¹³C signature of the more stable humic organic C (HOC) fraction indicated a significant compositional turnover in reforested soils, from C₄ pasture-derived C to C₃ forest-derived C, this did not translate to HOC gains compared with the pasture baseline. Matched old-growth rainforest soils had significantly higher concentrations of HOC than pasture and reforested soils, and soil microbial enzyme efficiency and the ratio of gram-positive to gram-negative bacteria followed the same pattern. Restoration plantings had unique soil microbial composition and function, distinct from baseline pasture but not converging on target old growth rainforest within the examined timeframe. Our results suggest that tropical reforestation efforts could benefit from management interventions beyond re-establishing tree cover to realize the ambition of early recovery of soil microbial communities and stable SOC. beyond re-establishing tree cover to realize the ambition of early recovery of soil microbial communities and stable SOC.