See more from this Session: General Forest, Range, & Wildland Soils: II
Tuesday, November 2, 2010
Long Beach Convention Center, Exhibit Hall BC, Lower Level
Soil acidification in forest ecosystems is of concern in the Athabasca oil sands region (AOSR), the largest area for open-pit oil sands mining in Alberta, Canada, due to acid emission and its subsequent deposition. This research was conducted to quantify H+ deposition in forest soils in AOSR and to determine sources of H+ deposition in different forest stands. We evaluated bulk precipitation, interception deposition (ID), canopy leaching (CL), and canopy uptake (CU) of H+ in throughfall in jack pine (Pinus banksiana) and trembling aspen (aspen, Populus tremuloides) stands in two watersheds (NE7 and SM8) in AOSR between 2006 and 2009. Bulk precipitation of H+ was 47.1 molc ha-1 yr-1 in NE7 and 117.2 molc ha-1 yr-1 in SM8. The major anion and cation of bulk deposition was SO42- and Ca2+, respectively. The pH of throughfall in jack pine stands was generally lower than that of bulk precipitation while the reverse was true in aspen stands. Greater H+ supply in jack pine than that in aspen stands was caused by the greater ID of SO42-, greater organic acid release, and less CU of H+ by jack pine canopy. The ID of H+ ranged from 127.8 to 148.2 molc ha-1 yr-1 in jack pine and from 61.3 to 135.7 molc ha-1 yr-1 in aspen in NE7 and from 158.3 to 176.9 molc ha-1 yr-1 in jack pine and from 41.1 to 134.2 molc ha-1 yr-1 in aspen in SM8. The CL of H+ by organic acids ranged from 127.1 to 128.7 molc ha-1 yr-1 in jack pine and from 0 to 6.0 molc ha-1 yr-1 in aspen. In conclusion, significant amounts of acid materials are being deposited in AOSR and canopy interception was a major process of atmospheric deposition. Jack pine stands may be exposed to a greater risk of soil acidification than aspen stands due to the greater acid deposition and organic acid production.