Print PageThe chemical and physical characteristics of plant litter have been shown to control ecosystem processes in many environments. The litter quality of a plant community’s most dominant member will impact biogeochemical cycling to a greater degree than the rest of the community due to its likely higher proportion of organic matter inputs, with the most extreme case being a monoculture. This is obviously important to the consequence of wetland invasion due to the usual pattern of one invasive species becoming dominant over all other species, though litter diversity could have strong effects at the beginning of an invasion. Also, a less studied aspect of decomposition is the potential litter x soil origin interaction that could be of importance when one species displaces others. We performed two laboratory incubations using litter collected from monocultures of Phalaris arundinacea, Phragmites australis, Typha x glauca and Carex lacustris (native representative). The first incubation was a factorial experiment with litter crossed by soil origin (soil collected under species monoculture) to determine species-specific litter effects on C and N cycling and possible litter x soil interaction. The second incubation manipulated litter diversity of the four species to better understand diversity effects on decomposition.
Results/Conclusions
Results from the first incubation show a significant interaction between litter type and soil origin, with the highest C mineralization rates occurring when P. australis litter was incubated in P. australis conditioned soil, and the lowest mineralization rates occurring in P. australis conditioned soil with no litter addition. Net N mineralization rates were the highest in the no litter addition controls, with P. australis litter addition being the greatest among the litter addition treatments. Evidence of N immobilization by the microbial community was seen in the P. arundinacea, T. x glauca and C. lacustris addition treatments due to the low quality of the litter inputs. The second incubation showed that litter diversity did not increase decomposition rates as predicted. While the additive effects of the single litter additions determined some of the results of the litter diversity treatments, others were idiosyncratic and not predictable from single litter additions. These results suggest that while species-specific litter quality can have a major role in decomposition, soil conditioning by the dominant plant species can also influence biogeochemical cycling. Though there wasn’t a clear trend for increasing litter diversity impacts on decomposition, there was evidence for more context-specific effects of litter diversity.
