The effect of climate change on treeline position at the latitudinal forest-tundra ecotone (FTE) is poorly understood. While the FTE is ~13000 km long, understanding relationships between climate and tree growth may depend on very fine scale processes, therefore appropriate tools are needed to appropriately characterize the leading (northernmost) edge of the FTE. We hypothesize that microstructural metrics obtainable from lidar remote sensing will relate to variation in the physical growth environment that governs seeding establishment. To test our hypothesis, we used terrestrial laser scanning (TLS) to collect highly spatially resolved 3-D structural information on spruce (Picea mariana, Picea gluaca) seedlings and their surrounding growth environment at the leading edge of a FTE in northern Alaska. From the 3-D TLS data, seedling coordinates were extracted along with randomly generated no-seedling coordinates for comparing locations of establishment against non-establishment. Ground roughness, canopy roughness, average aspect, wind shelter, and snow shelter were extracted from point clouds within a variable radius from seedling and no-seedling coordinates. Generalized linear models (GLM) were fit to determine if these environmental covariates were significantly associated with seedling establishment.
Results/Conclusions
Preliminary analyses at one of four sample plots suggested that there was not a statistically significant difference (p > 0.05) between seedling and no-seedling coordinates in terms of ground roughness, canopy roughness, and average aspect. However, preliminary evidence suggests that wind- and snow-shelter are important in seedling establishment. Future analyses will include all four plots, using additional structural metrics and optimized scale of structural parameters. These analyses will be useful for integrating microsite characteristics and seedling structural parameters with measures of tree stress, taken by in-situ fluorescence measurements. These analyses will also be performed for comparison with similar studies addressing the growth environment of mature tree stands at the FTE.