Biogeochemistry of the Western Gulf Coastal Plain as Impacted by Forest Management
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Plantation forestry is central to supplying the global demand for forest products and sustainable production will rely on information regarding the effects of disturbance on soil biogeochemistry. The extent of ecosystem disturbance will dictate the degree to which biogeochemical processes are perturbed. To date little is known about the impact of forest harvest activities on biogeochemical cycling in the western Gulf Coastal Plain, therefore the purpose of this study was to elucidate the impact of three harvest methods (bole only, whole tree, whole tree+forest floor removal) in factorial combination with three soil compaction intensities (none, intermediate, severe) 15-years following treatment and in an archived soil time-series in a Pinus taeda L. forest. I evaluated soil microbial biomass (SMB), and soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) storage, and stable isotopes ^(15)N and ^(13)C. I used chloroform fumigation extraction, dry combustion, and lithium metaborate fusion to quantify SMB, SOC and TN, and TP, respectively, and isotope ratio mass spectrometry to analyze 15N and 13C. Soil microbial biomass, TN, and TP decreased significantly in the order: bole only > whole tree > whole tree+forest floor removal; although not significant SOC followed the same pattern. Soil TN, litter and root N were generally ^(15)N enriched under the whole tree+forest floor removal treatment. Compared to control plots, harvest initially resulted in lower TN and SOC that was enriched in ^(15)N and ^(13)C, however, both C and N have been accumulating since 5-years post-treatment and have become increasingly less enriched isotopically. No evidence of a compaction or a harvest by compaction interaction effect was found on the measured variables. Although both C and N are accumulating, there were losses initially following harvest as evidenced by isotopic enrichment. Forest harvest practices that minimize removal of above-ground biomass will likely favor soil N and P retention and maintenance of the SMB pool. Since both N and P limit productivity in the sandy soils of this region, and because SMB plays a key role in nutrient cycling, harvest practices that favor nutrient retention and SMB will ensure the productivity of future rotations.
Foote, Julie (2014). Biogeochemistry of the Western Gulf Coastal Plain as Impacted by Forest Management. Doctoral dissertation, Texas A & M University. Available electronically from