Print PageLeaves of Rhamnus cathartica (European buckthorn) rapidly decompose and, as a result, buckthorn-invaded areas typically have sparse litter layers. The cause of such rapid litter decomposition is unclear but is thought to be the result of microbial metabolic processes. Because fungi are one of the primary decomposers of leaf litter in forest habitats, such shifts in metabolic processes are likely to be reflected in the composition of leaf litter fungal communities. For this study, we examined the metabolic activity and fungal species richness of leaf litter associated with R. cathartica and Quercus alba (white oak) in an oak woodland restoration chronosequence. Standardized litterbags of R. cathartica and Q. alba leaves were placed in three locations: un-restored and dominated by R. cathartica, newly restored (< 1 year), or mature restoration (6-14 years). Soil samples were measured for plant-available nitrate, ammonium, and phosphate levels. Leaf litter was collected 3 and 5 weeks after placement and subjected to analyses for enzymes associated with the decomposition of cellulose and lignin. Fungal species richness was examined using the following protocols: environmental DNA extraction from leaf litter, PCR with fungal specific primers, cloning of PCR products, and RFLP analyses to identify unique fungal Operational Taxonomic Units (OTU’s).
Results/Conclusions
Restoration status influenced the levels of plant-available nitrate, ammonium, and phosphate. Most notably, levels of nitrate and ammonium were highest in newly restored sites, and phosphorus in the mature restored site. In addition, fungal metabolic activity differed among sites. R. cathartica leaf litter levels of acid phosphatase (P mineralization), and cellobiohydrolase and β-N-acetyl-glucosaminidase (cellulose degradation) were significantly lower in the un-restored site. In contrast, there was no significant difference in litter phenol oxidase activity (lignin degradation) among sites. To date, analyses of fungal species richness by RFLP analyses have identified approximately 33 OTU’s associated with R. cathartica leaf litter. Sequencing of these fungal OTU’s will be done for further taxonomic identification. In addition, these techniques will be applied to Q. alba samples for comparison with R. cathartica fungal communities. Our results to date suggest that rapid turnover of R. cathartica leaf litter was associated with both changes in soil nutrient levels and increased decomposition of leaf cellulose. We expect that such differences will be reflected in fungal community composition.
