This thesis reports a series of experiments investigating some aspects of seasonal C and nutrient cycling and microbial community responses in an alpine heathland under three environmental pressures: N deposition represented by N additions at four levels (0, 10, 20, 50 kg N ha^-1 yr^-1), climate change simulated by open top chambers (OTCs) and accidental burning (one low intensity fire event that occurred in autumn 1999). The Culardoch experimental site was used, which is located on an alpine heathland in the Eastern Cairngorms mountains, Scotland. The responses studied were related to litter decomposition dynamics, soil processes and the soil microbial community. Mass loss and nutrient status during decomposition of litter from the plots (“native”) and collected outside the plots (“standard”) were studied. Litter decomposition was not affected significantly by the treatments. Despite the decrease in initial C:N ratio by N additions, this treatment affected only phosphomonoesterase activity and a trend for increasing glucosidase and xylosidase activity with increasing N additions was seen. OTC impacts were limited to effects on P cycling in “native” decomposing litter in the later stages of decomposition and more P was accumulated in litter from the plots with the OTCs. Burning affected N cycling in “native” decomposing litter (more N was accumulated in litter incubated in the burnt plots) and mass loss, C, N and P content in “standard” litter. Increased cellulolytic activity was observed in litter from the burnt plots. Those changes were attributed to shifts in the bacterial and fungal communities due to burning and warming treatments, while N additions had only a minor effect on microbial community structure. Decomposition phase had the greatest effect on microbial community structure suggesting that a succession of communities occurred during decomposition. One of the most important findings was the lack of interactive effects among the three main treatments, indicating that they act independently on particular components of the ecosystem.

Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on Apr. 21, 2009). Includes bibliographical references.