PS 40-92 - Linking hyperspectral imagery with foliar and soil nutrients to assess landscape-scale nutrient dynamics

Abstract: Nutrient availability and cycling plays a significant role in maintaining biodiversity and ecosystem functions. With rising levels of human disturbances and shifting climates, there is a need to understand what governs nutrient cycle dynamics through space and time. Carbon and nitrogen biogeochemistry is controlled by complex feedbacks between abiotic factors (soil properties, climate, topography) and biotic components (plant and microbial communities). In order to understand nutrient dynamics across complex landscapes, we must couple modeling and analysis with on-the-ground data collection to understand the effects of plant species identity and environmental factors simultaneously. We quantified ground observations of nutrient concentrations in tree canopies, inputs via leaf litter, and nutrient availability in soils with remotely sensed hyperspectral data across different soil types and plant species to investigate these drivers, both at the local- and landscape-level.

We conducted our research at the Sedgwick Reserve in Santa Barbara County, CA utilizing two California native oak species, the winter deciduous blue oak (Quercus douglasii) and the evergreen coast live oak (Quercus agrifolia). We investigated inter- and intraspecific differences in leaf canopy nutrient concentrations, leaf litterfall contributions, and the resulting effects to nutrient availability and cycling (total carbon and nitrogen, inorganic nitrogen concentrations, and net nitrogen mineralization) across different soil types and topographies. We then utilized hyperspectral imagery taken during the NASA Surface Biology and Geology High Frequency Time Series (SHIFT) Campaign to determine if any remotely-sensed metrics could be predictive of belowground nutrient availability. We detected differences between leaf nutrient concentrations between the evergreen and deciduous species driven by leaf carbon to nitrogen ratios as well as leaf litter biomass, with varying resulting impacts to soil nutrient availability across soil types.