Twenty-year changes in biomass and nutrient distribution in forests of Walker Branch Watershed, Tennessee

Conference · Fri Jan 01 04:00:00 EST 1988

OSTI ID:7055323

Johnson, D W; Olson, R J; Mann, L K; Todd, D E

Changes in biomass and nutrient distribution in forests of Walker Branch Watershed from 1967 to 1987 are reviewed. There have been major changes in species composition in certain forest types: yellow-poplar (Liriodendron tulipifera) has largely been replaced by shortleaf pine (Pinus echinata) in what was formerly the pine forest type, and chestnut oak (Quercus prinus) appears to be replacing hickory in the oak-hickory forest type. In both cases, insect attacks (bark beetles and borers) precipitated the changes by inducing heavy mortality in native pines and hickory species in the 1970s. Subsoil (Bt horizon) exchangeable Ca/sup 2 +/ and Mg/sup 2 +/ have decreased markedly over a period of only 11 years in certain poor, upper-slope stands with oak and oak-hickory vegetation. From nutrient flux and mass balance analyses, we conclude that the Ca/sup 2 +/ changes can be attributed primarily to the sequestering of calcium in biomass. The situation with respect to Mg/sup 2 +/ is less clear; leaching was low relative to uptake in the one plot where Mg/sup 2 +/ decreases were statistically significant (95% level, t-test), yet it was clearly the dominant mechanism of Mg/sup 2 +/ export in all other plots where less significant (85% level, t-test) decreases were noted. It is noteworthy that leaching is dominated by SO/sub 4//sup 2/minus//, implying that acid deposition may be a major cause of the subsoil exchangeable Mg/sup 2 +/ decreases in some cases. 31 refs., 11 figs., 3 tabs.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 7055323
• Report Number(s): CONF-8807107-2; ON: DE88016804
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
140504* -- Solar Energy Conversion-- Biomass Production & Conversion-- (-1989)
ALKALINE EARTH METALS
ANIMALS
ARTHROPODS
BIOMASS
CONIFERS
DISSOLUTION
DISTRIBUTION
ECOLOGICAL SUCCESSION
ELEMENTS
ENERGY SOURCES
EVALUATION
GROWTH
INSECTS
INVERTEBRATES
LEACHING
MAGNESIUM
MASS BALANCE
METALS
MINERAL CYCLING
MODIFICATIONS
MONITORING
NATIONAL ORGANIZATIONS
NUTRIENTS
OAK RIDGE RESERVATION
OAKS
OXYGEN COMPOUNDS
PINES
PLANT GROWTH
PLANTS
POPLARS
RENEWABLE ENERGY SOURCES
SEPARATION PROCESSES
SOILS
SPATIAL DISTRIBUTION
SULFATES
SULFUR COMPOUNDS
TREES
US DOE
US ERDA
US ORGANIZATIONS