Temporal changes of iron, manganese, zinc, copper and boron in a Southeastern Piedmont soil ecosystem

摘要

A long-term study on the biogeochemistry of trace elements was conducted in the acidic and old soils in the southern Piedmont loblolly pine forest of the USA. The long-term soil data indicate that forest growth affected three contrasting patterns among the five trace elements under study: 1) HCl- and AAO- extractable soil extractable B and Mn appear to be depleted in amounts that are comparable to removals due to accretion in tree biomass and in the O horizon. 2) Zn removals were 10-fold greater than soil depletions as indexed by either HCl or AAO, indicating significant resupply from other sources: dissolution of minerals, deep root uptake and re- circulation from soil layers >60 cm in depth, or atmospheric deposition. 3) Soil extractable Cu and Fe significantly increased in the surface 60 cm of soil between 1962 and 1997, although substantial amounts of Fe and Cu were accumulated in tree biomass and in the O horizon. Hypothetically, substantial amounts of Fe are translocated upward from surficial layers of mineral soil. AAO-Fe, which indexes short-range order Fe oxides in soil, has increased greatly, presumably at the expense of the much larger pool of more crystalline Fe.