Charred plant fragment–aluminium complexes in buried humic horizons of a cumulative volcanic soil profile: Formation, accumulation and potential role

Abstract

The objective of the present study was to investigate the formation, accumulation and potential role of charred plant fragment (CPF)-aluminium (Al) complexes in several buried A (Ab) horizons of a cumulative volcanic soil profile, focusing on CPFs, active Al components and soil age. Nineteen soil samples were collected from four buried humic horizons (2A-5A, from 7.3 cal ka BP to AD 1471), and their CPF-carbon (C), soil organic C (SOC), acid oxalate-extractable Al (Al ox ), pyrophosphate-extractable Al (Al py , Al-humus complexes) and short-range ordered Al minerals (Al ox À Al py ) were quantified. The proportion of CPF-C content (up to 15.8 g kg À1 ) to SOC content (up to 117 g kg À1 ) ranged from 2.3% to 15.1% (8.4% on average). The contents of active Al components (6.71-77.1 g kg À1