RELEASE-2022

For sites with predominantly forest/shrubland cover, spatial collection methods differed during early operations (2016‐2018) compared to 2019 and onward. The earlier method involved sampling the top three dominant species present in each of 14 pre‐assigned plots, 4 Tower and 10 Distributed. However, with input from the community, the design shifted away from plots and towards a site‐based approach focused on sampling the full spectrum of canopy biodiversity present at the site. Many of the individuals sampled are monitored in the Vegetation Structure (VST) protocol, and all are georeferenced, either using stem offsets (prior to 2020 as well as smaller individuals) or polygon shapefiles of sampled crowns mapped on top of recent AOP spectrometer data while in the field (2020 and onward for larger individuals). For grassland sites, the design has remained consistent. Foliage is sampled from 20 plots; all aboveground material in one or two (depending on plot size), randomly selected 0.1 X 2 m clip strips is harvested and homogenized, yielding 20-24 samples per bout. Traits are measured on species mixtures that represent community composition of the clip strip. In sites with both woody and herbaceous cover, a combination of the two sampling approaches is employed. Foliar sampling occurs once every five years per site during the period of historic peak greenness. Whenever possible, sampling also occurs within two weeks of the AOP overflight and aopCollectDate for each sample is included in the data. Chlorophyll subsamples are immediately frozen after collection, and additional processing of samples, including scans for leaf mass per area and initiation of sample drying for leaf water content and chemical analyses, occurs within 1-5 days of collection. During the same year that foliar traits are measured, other biogeochemical pools and fluxes are as well (e.g., soil chemistry, DP1.10086.001; litter chemistry, DP1.10033.001; root biomass and chemistry, DP1.10067.001) with coincident data at a subset of plots.