Modeling foliage density and leaf mass area dynamics in Intermountain Western USA conifers

Abstract

Leaf mass area (LMA) is a dominant trait quantifying tradeoffs between structure and physiology. LMA variations are driven by a combination of leaf density and morphology. LMA is widely used in ecosystem process models and in fire research to model live fuel moisture content (LFMC), a dominate predictor of wildland fire behavior. Despite its importance, LMA is often assumed as invariant both seasonally and between species. Here, we measured density, LMA, and foliar chemistry across 10 Intermountain USA conifer species and used these data to develop mechanistic models of foliar density and LMA. We first modeled density as the combination of three components: neutral detergent fiber (structural carbohydrates), non-structural carbohydrates, and crude fat. These foliar density estimates were then combined with all-sided surface-areato- volume ratio (SAV) to predict LMA. These models adequately predicted interspecies foliar density and LMA across all 10 conifer species (𝑅 = 0.77 and 𝑅 = 0.81, respectively) and intraspecies variations for intensively sampled Douglas fir (𝑅 = 0.75 and 𝑅 = 0.77, respectively). Predicted density and LMA were applied to a mechanistic model to predict LFMC. Predicted LFMC were strongly correlated with measured LFMC across conifers (𝑅 = 0.82 and 𝑅 = 0.73, respectively) and for Douglas fir (𝑅 = 0.77 and 𝑅 = 0.69, respectively). This framework can improve seasonal LMA representation in ecosystem process models, advance our understanding of live vegetation-driven wildland fire behavior and can help explain the leaf trade-offs that regulate terrestrial productivity and global carbon and water cycles.

Citation

Keefer, Ella M.; Jolly, W. Matt; Conrad, Elliott T.; Brown, Tegan P.; Hillman, Samuel C. 2026. Modeling foliage density and leaf mass area dynamics in Intermountain Western USA conifers. Ecological Modelling. 521: 111732.