Abstract
We studied bark thickness in the mixed-conifer forest type throughout California. Sampling included eight conifer species and covered latitude and elevation gradients. The thickness of tree bark at 1.37 m correlated with diameter at breast height (DBH) and varied among species. Trees exhibiting more rapid growth had slightly thinner bark for a given DBH. Variability in bark thickness obscured differences between sample locations. Model predictions for 50 cm DBH trees of each species indicated that bark thickness was ranked Calocedrus decurrens > Pinus jeffreyi > Pinus lambertiana > Abies concolor > Pseudotsuga menziesii > Abies magnifica > Pinus monticola > Pinus contorta. We failed to find reasonable agreement between our bark thickness data and existing bark thickness regressions used in models predicting fire-induced mortality in the mixed-conifer forest type in California. The fire effects software systems generally underpredicted bark thickness for most species, which could lead to an overprediction in fire-caused tree mortality in California. A model for conifers in Oregon predicted that bark was 49% thinner in Abies concolor and 37% thicker in Pseudotsuga menziesii than our samples from across California, suggesting that more data are needed to validate and refine bark thickness equations within existing fire effects models.
Highlights
There is interest in predicting fire-caused tree mortality in places where prescribed fire or wildfires are common [1,2,3,4]
There are many factors that can influence the formation of bark and little information exists comparing this trait across geographic gradients [22, 23]
Sample trees covered a broad range of tree sizes, crown ratio, and growth (Supplementary File, Table S1, in Supplementary Material available online at http://dx.doi.org/10.1155/ 2016/1864039)
Summary
There is interest in predicting fire-caused tree mortality in places where prescribed fire or wildfires are common [1,2,3,4]. Tree bark plays a critical role in reducing mortality from fire. Bark protects living cambial tissues from external biotic and abiotic forces [14,15,16,17]. Different tree species exhibit distinct strategies in growth and the development of defense features with some allocating proportionally more resources to bark development than others [18,19,20,21]. There are many factors that can influence the formation of bark and little information exists comparing this trait across geographic gradients [22, 23]. The properties and function of bark are a result of complex evolutionary strategies by these organisms to perform more efficiently and competitively within their native ranges [21, 22]
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