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Changes from pasture to a native tree plantation affect soil organic matter in a tropical soil, Panamá

Moore, Tim R., Abraham, Muriel, Kalácska, Margaret, Murphy, Meaghan T., Potvin, Catherine
Plant and soil 2018 v.425 no.1-2 pp. 133-143
C3 plants, biomass, ecosystems, forests, organic carbon, pastures, plantations, soil analysis, soil organic matter, stable isotopes, trees, tropical soils
BACKGROUND AND AIMS: We examined changes in soil organic matter arising from conversion of a 45-year old pasture to a 10 yr. old native tree plantation in Panamá, to evaluate the effect of monoculture and mixtures. METHODS: We intensively sampled the soil 0–10 cm depth in the pasture in 2001 and in 22 plantation plots in 2011, ranging from 5 monocultures to 3- and 6-species treatments; samples were also taken from an undisturbed forest site. Soil analyses included organic carbon (SOC) and δ¹³C. RESULTS: Conversion of the pasture to tree plantation resulted in an overall loss of SOC of 0.6 kg m⁻² (18%) in the top 10 cm, but neither tree species nor diversity had a significant effect. End-member δ¹³C values suggested that the contribution of C₃ plants to SOC was increased from 26% in the pasture to 55% after 10 years of plantation and SOC turnover times were calculated to be 21–36 yr. CONCLUSIONS: The magnitude of the loss in soil SOC is smaller than the increases in tree biomass (~3 kg C m⁻²) and litter (~0.3 kg C m⁻²) in the plantation, but still a significant part of the ecosystem C balance.