<p>Forest ecosystems are a significant component of the global carbon (C) cycle. Afforestation is considered a cost-effective and ecologically viable means to sequester atmospheric carbon. However, afforestation requires intensive management practices, including thinning, to maintain and enhance the carbon sequestration capability of the forest. This study examines thinning effects on forest carbon dynamics using eddy covariance (EC) methods. In January 2012, a 74-year-old white pine (<em>Pinus strobus</em>) plantation located in southern Ontario was selectively thinned. Approximately 30% of trees, equating to 2308 m<sup>3</sup> of wood (sawlogs and pulpwood), were removed to improve light, water and nutrient availability for remaining trees. Fluxes of energy, water, carbon dioxide (CO<sub>2</sub>) as well as meteorological variables were measured throughout the year following thinning and compared to data from the previous 9 years to evaluate effects of thinning on forest carbon dynamics. Mean annual net ecosystem productivity (NEP), gross ecosystem productivity (GEP) and ecosystem respiration (RE) from the 9 years prior to thinning were 290, 1413 and 1118g C m<sup>-2</sup><strong>,</strong> respectively. Post-thinning NEP, GEP and RE were 154, 1509 and 1350 g C m<strong><sup>-</sup></strong><sup>2</sup><strong> </strong>year<sup>-1</sup>, respectively. Post-thinning NEP was significantly less than pre-thinning at the annual time scale due to higher RE, however post-thinning fluxes were still within the range of interannual variability. At this site, approximately 20% of interannual variability in NEP, GEP and RE was explained by environmental conditions. Effects of extreme weather events, particularly heat and drought stress, were demonstrated to negatively impact NEP. Biotic responses to environmental drivers explained the remaining 80% of interannual variability in fluxes. Thinning did not significantly impact these responses. Further, results suggest that thinning may improve tolerance to drought stress by improving water availability for remaining trees. Therefore, thinning has the potential to effectively reduce resource competition and stimulate growth and carbon sequestration in temperate coniferous forests.</p> / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/13732 |
| Date | 04 1900 |
| Creators | Trant, Janelle S. |
| Contributors | Arain, M. Altaf, Geography and Geology |
| Source Sets | McMaster University |
| Detected Language | English |
| Type | thesis |
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