Remotely sensed crown nutrient concentrations modulate forest reproduction across the contiguous United States

Global forests are increasingly lost to climate change, disturbance, and
human management. Evaluating forests' capacities to regenerate and
colonize new habitats has to start with the seed production of individual
trees and how it depends on nutrient access. Studies on the linkage
between reproduction and foliar nutrients are limited to a few locations
and few species, due to the large investment needed for field measurements
on both variables. We synthesized tree fecundity estimates from the
Masting Inference and Forecasting (MASTIF) network with crown nutrient
concentrations from hyperspectral remote sensing at the National
Ecological Observatory Network (NEON) across the United States. We
evaluated the relationships between seed production and foliar nutrients
for 56,544 tree-years from 26 species at individual and community scales.
We found a prevalent association between high foliar phosphorous (P)
concentration and low individual seed production (ISP) at the continental
scale. With-species coefficients to nitrogen (N), potassium (K), calcium
(Ca), and magnesium (Mg) are related to species differences in nutrient
demand, with distinct biogeographic patterns. Community seed production
(CSP) decreased four orders of magnitude from the lowest to the highest
foliar P. This first study on hyperspectral imagery indicates promise for
future monitoring of reproductive potential. The fact that both ISP and
CSP decline at high foliar P levels has immediate applications in
improving forest demographic and regeneration models by providing more
realistic nutrient effects at multiple scales.