Impact of mountain pine beetle on the net ecosystem production of lodgepole pine stands in British Columbia

• Published in: Agricultural and forest meteorology 2010-02, Vol.150 (2), p.254-264
• Main Authors: Brown, M., Black, T.A., Nesic, Z., Foord, V.N., Spittlehouse, D.L., Fredeen, A.L., Grant, N.J., Burton, P.J., Trofymow, J.A.
• Format: Article
• Language: English
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agronomy. Soil science and plant productions; Animal and plant ecology; Animal, plant and microbial ecology; Beetles; Biological and medical sciences; Canopies; carbon sequestration; Dendroctonus ponderosae; Disturbance; Eddy covariance; eddy covariance method; forest canopy; forest pests; forest stands; forest trees; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; growing season; Harvesting; insect pests; mortality; Mountain pine beetle; Mountains; Net ecosystem production; overstory; Photosynthesis; Phytopathology. Animal pests. Plant and forest protection; Pine; Pinus contorta; Pinus contorta var. latifolia; primary productivity; Protozoa. Invertebrates; Respiration; Seasons; stand structure; Stands; Supports; Synecology; temperate forests; Trees; understory; vegetation
• ISSN: 0168-1923; 1873-2240
• DOI: 10.1016/j.agrformet.2009.11.008

British Columbia (BC), Canada is experiencing a severe mountain pine beetle (MPB) ( Dendroctonus ponderosae) epidemic extending over an area of 135,000 km 2. The widespread mortality of lodgepole pine ( Pinus contorta var. latifolia) caused by the beetle has significant implications for BC's timber supply and Canada's carbon (C) budget. This study used the eddy-covariance technique to examine how the beetle is impacting the net ecosystem production (NEP) of two attacked lodgepole pine-dominated stands in the central interior of BC. MPB-06 is an 83-year-old stand that was first attacked in 2006. At the start of 2007 roughly 60% of the canopy had been attacked and by October 2008 only 21% of the trees remained healthy. MPB-03, a 110-year-old stand, had >95% pine canopy mortality as a result of a 2003 beetle attack, and also differed from MPB-06 in that it had a more developed secondary structure (consisting of tree seedlings and saplings and sub-canopy and canopy trees) that survived the beetle attack. Eddy-covariance measurements were also conducted in two stands near MPB-06 harvested in 2005 and 1997 (CC-05 and CC-97) for approximately three-week periods each during the 2007 growing season. MPB-06 had an annual NEP of −82 and −33 g C m −2, while MPB-03 had an NEP of −56 and 4 g C m −2 in 2007 and 2008, respectively. In the 2007 and 2008 growing seasons (May–September), MPB-06 was a sink of 12 and 52 g C m −2, while MPB-03 was a sink of 17 and 68 g C m −2, respectively. The productivity at MPB-06 resulted from an increase in photosynthesis by the remaining healthy trees and understory vegetation, while at MPB-03 the secondary structure and understory vegetation showed a strong capacity to sequester C due to an opening up of the stand as a result of canopy mortality. Average daily values of NEP during the measurement periods at CC-97 and CC-05 were −0.37 and −0.87 g C m −2, respectively, showing that even 10 years following harvesting, these stands are likely to remain growing season C sources. That MPB-06 and MPB-03 were growing season C sinks suggests that deferring the harvest of stands with significant levels of secondary structure could prevent MPB-attacked forested areas from becoming C sources over extended periods.