Carbon storage traits of conifers across a leaf life-span gradient of six months to 16 years

Recent studies have revealed that contrasting characteristics among conifers and larches---such as relative growth rate and nutrient use efficiency---may not be as reflective of functional differences as earlier hypothesized. As functional traits are examined at the tree instead of leaf level, it appears that larches are not as physiologically different from conifers as their deciduous leaf habit may suggest. This indicates that tree-level advantages of being evergreen, such as demand-driven carbon storage, are achieved via deciduousness in larch. Previous studies have looked for contrasting characteristics in conifer and larch or examined traits across a leaf life-span gradient of conifers. A unique aspect of this study is the inclusion of larch in addition to a wide range of leaf life spans in conifers (up to 20 years). Similar to a common garden, all trees in this study were taken from a cultivated environment (University of Wyoming Laramie campus) so that the effects of natural habitat variation and harsh environmental conditions such as drought and winter damage are significantly reduced.;Results indicate that trait variation among species with leaf life spans ranging from 3 to 16 years is less variable than expected in natural populations. Therefore the campus trees can be used as a baseline for determining plasticity of traits such as wood density, specific leaf area, total non-structural carbohydrates, and conducting area. Larch stands out from all conifers but leaf life span does not explain the variability in traits among the six species of conifers as predicted. First of all, we conclude that plasticity plays an important role in the expression of coniferous tree characteristics. Artificially favorable environments reduce the expression of trait extremes known to contribute to increased survival rates in natural, harsh conditions. Secondly, this study is the first to suggest a negative non-linear relationship between carbon storage and wood density for roots and branches and the positive one for stems, which is partly explained by conducting area via the model. Both of these major results support the notion that while observing traits in isolation may yield intuitive results, studying how two or more traits interact in different environments is crucial for teasing out potential mechanisms that determine morphological and physiological characteristics. Increasing LLS can be thought of as reflecting a nutrient or water availability gradient, suggesting the importance of interspecific studies of conifers across altitudes and intraspecific studies within an altitude to address carbon storage and growth questions.