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The Hubbard Brook Ecosystem Study: Biogeochemistry of Lead in the Northern Hardwood Forest
Author(s) -
Smith William H.,
Siccama Thomas G.
Publication year - 1981
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1981.00472425001000030015x
Subject(s) - forest floor , environmental science , biogeochemistry , experimental forest , clearcutting , biogeochemical cycle , biota , forest ecology , subalpine forest , watershed , ecosystem , biomass (ecology) , hydrology (agriculture) , ecology , geology , biology , geotechnical engineering , machine learning , computer science
The average annual Pb input to the northern hardwood forest at the Hubbard Brook Experimental Forest in central New Hampshire was 266 g ha −1 year −1 based on 4 years of records. Lead output via streamwater and eroded particulate matter was 5.0 and 1.1 g ha −1 year −1 , respectively. Lead concentration in precipitation averaged 22 µ g liter −1 and showed a significant decline over the 4 sample years (1975–1978). Lead input to the ecosystem via meteorological vectors is accumulated in the forest floor. Total current Pb content of the forest floor was 8.6 kg ha −1 and showed no significant differences along the elevation gradient of the watershed (400–800 m). Lead concentration in the forest floor was maximum on the ridge due to a minimum forest floor mass relative to the rest of the watershed. Within the forest floor, maximum Pb concentration is in the fermented (F) layer. Total Pb content of the forest biomass (stems ≥ 10 cm dbh) was 1,248 g ha −1 . Lead concentration in the biota was in the following order: lichens (213 µ g g −1 ) > mosses (190 µ g g −1 ) > tree twigs (26 µ g g −1 ) > roots (20 µ g g −1 ) > bark (19 µ g g −1 ) > leaves (7 µ g g −1 ) = bracket fungi (7 µ g g −1 ) > wood (0.7 µ g g −1 ). Disturbance of the forest ecosystem through harvest cutting, other than through increased runoff, increased erosion, and transport of particulate matter, does not alter the biogeochemistry of Pb and does not result in increased mobility and export of Pb due to gross or subtle alterations of the behavior of Pb in the ecosystem.