Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. plant functional traits plant phenology 1406-65-1 Chlorophyll N762921K75 NEON Nitrogen Soil biotic controls climate change functional diversity functional traits gas exchange intra‐site variability land surface phenology leaf hyperspectral reflectance maximum carboxylation capacity multitrait covariance optimality strategy partial least-squares regression (PLSR) photoperiod plant functional types productivity satellite remote sensing solar radiation species diversity spring phenology