Using light to predict fuels-reduction and group-selection effects on succession in Sierran mixed-conifer forest

Bigelow, S.W., North, M.P., & Salk, C.F. (2011). Using light to predict fuels-reduction and group-selection effects on succession in Sierran mixed-conifer forest. Canadian Journal of Forest Research 41 (10) 2051-2063. 10.1139/x11-120.

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Many semi-arid coniferous forests in western North America have reached historically unprecedented densities over the past 150 years and are dominated by shade-tolerant trees. Silvicultural treatments generally open the canopy but may not restore shade-intolerant species. We determined crossover-point irradiance (CPI) (light at which the height growth rank of pairs of species changes) for seedlings in Sierra Nevada mixed-conifer forest and used these to interpret light environments produced by fuels-reduction thinning and group selection with reserved large trees. Nine of 21 species pairs had well-defined CPIs. The CPI of the most common shade-tolerant and intolerant species (white fir (Abies concolor (Gordon & Glendl.) Lindl. ex Hildebr.) and ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & C. Lawson)) was 22.5 mol m^(-2) day^(-1) or 41% of full sun. Median understory irradiance increased from 9.2 mol m^(-2) day^(-1) (17% full sun) in pretreatment forest to 13 mol m^(-2 day^(-1) (24% full sun) in lightly and 15.5 mol m^(-2) day^(-1) (28% full sun) in moderately thinned stands and 37 mol m^(-2) day^(-1) (67% full sun) in group-selection openings. We estimate that 5%-20% of ground area in lightly to moderately thinned stands would have enough light to favor shade-intolerant over shade-tolerant growth compared with 89% of ground area in group-selection openings. The CPI provides a tool to assess regeneration implications of treatment modification such as increasing heterogeneity of thinning to enhance regeneration or reserving large trees in group-selection openings to maintain wildlife habitat.

Item Type: Article
Research Programs: Ecosystems Services and Management (ESM)
Bibliographic Reference: Canadian Journal of Forest Research; 41(10):2051-2063 (October 2011) (Published online 30 September 2011)
Depositing User: IIASA Import
Date Deposited: 15 Jan 2016 08:45
Last Modified: 27 Aug 2021 17:39

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