I and many other older scientists goofed in the past when we cut grass leaves from stems and put them in litterbags on sediment surfaces in order to follow their decay. We should have done our homework: it has been known for a long time that most grasses do not have abscission layers at the bases of their leaves, so their leaves do not fall away via abscission after senescence. This image shows the typical structure of grass leaves -- they have two parts, the blade and the sheath. The connection between blade and sheath is the ligule. The sheath is wrapped tightly around the true stem. The ligule provides a strong mechanical bond between the blade and sheath, so when the leaf dies, the blade stays attached, and begins decay in the attached position. In order to study natural decomposition of grass shoots, one must leave the shoot parts in place. Tags (e.g., electrical cable ties) can be used to mark individual leaf blades or shoots to establish starting points for decay of senescent blades. Or if blades are too delicate or small for tagging, one could put a numbered tag at the base of the shoot, and take a digital photo of the shoot to provide a starting-point identifier for individual senescent blades. Cutting blades and putting them in upright litterbags comes closer to the natural situation than putting the bags on the sediment surface, but it may also cause a substantial deviation from the natural situation. This is due (among other factors such as unnatural clumping of blades) to the breaking of aerenchymal- channel contact to the parent shoot. Aerenchymal (gas-passageway) channels may enable exchange of CO₂ and O₂ (and other items?) between the living plant and decay fungi in the attached-decaying blades. (Maybe this potential mutualism is one reason for the evolution of retention of dead blades by the plant?) See Newell, 1996, Established and potential impacts of eukaryotic mycelial decomposers in marine/terrestrial ecotones, J Exp Mar Biol Ecol 200:187-206; Newell & Porter, 2000, Microbial secondary production from saltmarsh-grass shoots, and its known and potential fates, pp. 159-185 in Weinstein & Kreeger, Concepts and Controversies in Tidal Marsh Ecology, Kluwer.