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Decade-Scale Influences of Organic Matter Removal on Forest Soil Biogeochemistry and Microbial Ecology
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One of the main goals of applied forest ecology is to utilize silvicultural practices that generate economic output from forest products while simultaneously maintaining the long-term sustainability of forest stand properties such as wildlife habitat, the ability to sequester carbon, soil nutrient stocks, and soil microbial community structure and function. To this regard, there are some forest management methods (such as clear-cutting, short rotations, whole-tree harvesting, and litter removal) that utilize intensive biomass removal techniques to increase economic output. These intensive methods could jeopardize the long-term sustainability of the forest ecosystem through the degradation and destabilization of soil biotic and abiotic properties. Because of this, the purpose of this study was to analyze specific soil biogeochemical and microbiological properties of Pinus taeda L. (loblolly pine) stands that were subjected to different harvest methods 18 years ago. Soil properties of intensively harvested stands (whole-tree harvest + forest floor removal) were compared to those of stands subjected to a less intensive method (bole-only harvest), and to unharvested control stands (tree age: 60-80 years old). Results indicate that increasing organic matter removal intensity can lead to reduced tree size and reduced soil organic carbon and soil total nitrogen; furthermore, soils from whole-tree harvest + forest floor removal plots were less enriched in δ13C and more enriched in δ15N suggesting that increasing forest harvest intensity decreases long-term carbon mineralization and decomposition potential as well as increases N-losses through volatilization and leaching. Increasing organic matter removal intensity also reduced microbial biomass carbon and microbial biomass nitrogen, NH4+, and NO2- + NO3- pools, increased the concentration of Mehlich-III extractable P, and altered the abundance of archaeal and bacterial amoA. Furthermore, intensive forest harvest led to decade-scale alterations in ammonia-oxidizer, fungal, and bacterial and community structure as well as functional fungal and bacterial groups relative to unharvested stands. These results imply that more intensive harvest methods not only lead to reduced tree size, but also create decade-long alterations in physical, chemical, and biological properties in surface and subsurface soils, which could be inherited by future rotations.
Mushinski, Ryan Michael (2017). Decade-Scale Influences of Organic Matter Removal on Forest Soil Biogeochemistry and Microbial Ecology. Doctoral dissertation, Texas A & M University. Available electronically from