Date of Award

12-2011

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Plant, Soil, and Environmental Sciences

Advisor

Ivan J. Fernandez

Second Committee Member

Tsutomu Ohno

Third Committee Member

Kevin Simon

Abstract

Three soil drainage classes and two forest types were used to evaluate the influences on soil organic carbon (SOC) pools. The soil drainage classes were moderately well drained (MWD), somewhat poorly drained (SWPD) and poorly drained (PD) and the forest types were coniferous (CF) and broadleaved deciduous (BLD). The research was centered at Bear Brook Watershed in Maine (BBWM), a long term ecological research site in eastern Maine, USA. Within each soil drainage class, 6 quantitative soil pedons were excavated, 3 in CF and 3 in BLD forests, and soils were sampled from the forest floor (O horizon) and several depth increments (0-5 cm, 5-25 cm, 25-50 cm, 50-C, C). The MWD soils had significantly higher C concentrations (%C) through the majority of the soil compared to SWPD and PD soils. For forest type comparisons within each soil drainage class, CF forests had a significantly higher C content in the O horizon, mineral soil and whole soil (O Horizon + mineral soil) compared to BLD in MWD soils, but CF C content were only numerically greater than BLD forests in SWPD and PD soils. The relative proportion of C fractions among soil drainage classes and forest types was similar, with the largest fractions for all soil drainage classes and forest types found in the stable fraction, with lesser amounts in the passive fraction. The active fraction was « 1% of the total C fraction pool. There were significant differences in %C among soil drainage classes but not forest type, and trends for C fractions relating to C content followed similar trends for C content data within soil drainage classes between CF and BLD forests. Soil respiration (Rs) data indicated significantly greater seasonal means for SWPD and PD soils compared to MWD soils. The SWPD and PD soil Rs monthly means were significantly greater for the months of July, August and September. Strong correlations were observed between soil temperature and air temperature with Rs, but not with gravimetric soil. Future SOC research should focus on understanding spatial and temporal differences in landscapes that can have high variability over short distances. Integration of understanding SOC dynamics in this context should include focusing on understanding patters of soil drainage, forest types and land use history, reliable estimates of coarse fragments, and understanding variations in types of wetland soils.

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