Beyond total carbon: conversion of amazon forest to pasture alters indicators of soil C cycling

It is well established that land use change (LUC) can impact soil organic carbon (SOC) in tropical regions, but the long-term effects of LUC on quality and C cycling remain unclear. Here, we evaluated how affects Amazon region using a 100-year observational chronosequence spanning primary forest-to-pasture conversion subsequent secondary forest succession. We found surprising increase topsoil SOC concentrations 60 years following conversion, despite major losses (> 85%) forest-derived within first 25 years. Shifts molecular composition SOC, identified with diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, occurred tandem significant decline permanganate-oxidizable (POXC) ?-glucosidase activity (per unit SOC), interpreted as deceleration after pasture grasses became dominant source inputs to soil. Secondary succession caused rapid reversal conditions observed under for not (DRIFT spectroscopy), reflecting long-lasting effect cycling. Our results show changes origin occur deforestation legacy some indicators (e.g. enzyme activity) others composition). This approach offers mechanistic understanding basin be used help explain conflicting reports impacts region.