This collection contains oven-dried terrestrial litterfall samples (NEON sample class: ltr_chemistrySubsampling_in.archiveSampleID). Litterfall is defined as shed leaves and needles, reproductive parts (i.e. flowers, fruits, cones, seeds, etc.), and fine woody debris with butt-end diameter < 2 cm. Up to two trap-pairs (ground + elevated) are deployed per plot in forested ecosystems. Elevated litter traps are designed to be large enough that the average size of abundant foliage and fine woody debris elements are easily intercepted by the trap. Ground traps are intended to intercept particularly large foliage elements that will not fit in elevated traps (e.g. palm fronds), and fine woody debris pieces that are too long to be sampled in elevated traps including small diameter branches. Both elevated and ground traps are established in Tower Plots. The timing and frequency of sampling for elevated traps depends on the dominate vegetation type at the site. Ground traps are sampled once annually at Tower Plots (± 2 weeks); archived samples correspond to sampling events associated with chemical analyses (once every five years). The sampling interval of elevated litter traps is variable by dominant overstory vegetation. Deciduous forests are sampled once in the spring then multiple times during fall senescence; evergreen and coniferous forests are sampled year round. Traps are consistent with those used by the Smithsonian Center for Tropical Forest Science (CTFS). Mass data for each collection event are measured separately for functional groups: Leaves, Needles, Twigs/branches, Woody material, Seeds, Flowers and other non-woody reproductive structures, Other, and Mixed (unsorted). Once every five years, elevated litter trap sampes from a single collection are analyzed for total C, N, stable isotopes of C and N, and lignin. Chemistry samples for leaves and needles are pooled at the plot level, where there are two traps per plot. Other functional group samples are pooled at the site level. Subsamples for archive are oven-dried at 65 degrees Celsius for at least 48 hours then ground in a Wiley mill to 20 mesh size (sieve opening size = 0.0331 in) then transferred to a 20 mL HDPE scintillation vial. Archived samples are stored at room temperature. See related links below for protocols and NEON related data products.