A knowledge of the conditions that influence the activities of enzymes that mediate the key processes occurring within peat soils is a prerequisite for predicting potential ecosystem responses to climate change, human utilization and management policies.
In contrast to previous studies focussed on single biomes, the following study included three peatlands along a climatic gradient: Arctic (Svalbard, Norway), temperate (Wales, United Kingdom) and tropical (Andean mountains, Colombia). The study also encompasses a deliberately broad range of biotic and abiotic parameters, which were investigated along the peat profile.
Contrasting relationships were found between measured parameters across the three peatlands. Generally, the highest biogeochemical processing rates occurred in the superficial layer indicating it to be the most biologically active layer. However, in the deeper mineral layer of Svalbard, phenol oxidase activity was as high as in the superficial layer, with higher pH and nutrient concentrations. Also, nitrous oxide flux from the deeper layers did not
significantly differ from that of the upper layers, further highlighting the potential for the deeper layers of peats to be more active than is commonly assumed. The dominant controlling factor for phenol oxidase activity in Svalbard and Colombia was pH, while in Wales only hydrolases were positively correlated with pH. The response of hydrolase activities and gas fluxes to phenolics concentration also varied between the three regions, indicating that the three climatic peatlands differed in parent plant chemistry that controls
peat chemical composition across the latitudinal transect from the Arctic to the tropics.
A negative correlation was expected between enzyme activity and nutrient availability. However, contradictory results were found concerning this perspective, possibly because soil samples obtained from the three contrasting peatlands differed in nutrient concentrations, changing the dependency of in situ microbial communities on edaphic nutrients.
Significant differences in measured parameters were identified between different regions. Relatively high hydrolase activities were observed in Colombia, possibly due to the higher demand for nutrients and/or higher energy supply. Phenol oxidase was relatively higher in the Arctic, associated with significantly higher pH and concentrations of most inorganic nutrients. Conversely, the Welsh peatland exhibited the lowest phenol oxidase activity, consistent with lowest pH and consequently highest phenolics concentration. The higher
dissolved organic carbon (DOC) concentration towards the tropics can be attributed to the higher primary productivity towards the equator where there is a warmer climate and longer growing season. In addition, decreased DOC concentration has been linked to increased sea salt, which were high in Svalbard possibly due to the proximity of the sampling sites to the sea.
The effect of soil variables on community composition of micro-eukaryotes in peatlands along a climatic gradient is useful for predicting how peatland structure and function may respond to future climate change. In the present study, the diversity and relative abundance of micro-eukaryotes were determined. Also, attempts were made to relate micro-eukaryote
community composition to abiotic and metabolic variables. The general pattern of peat soil micro-eukaryote abundance was consistent with other studies of peatlands, where the supergroups Alveolata, Opisthokonta, Rhizaria and Stramenopiles were dominant.
Redundancy analysis revealed that the community composition of micro-eukaryotes differed significantly between the three regions in response to the selected variables; high pH, nutrients, organic matter content and oxygen concentration, and low temperature structured micro-eukaryotes community. The results showed that phagotrophs, phototrophs and mixotrophs dominated in the Arctic, while with increasing temperature and phenolics
concentration, community composition showed an increasing dominance of parasites in the temperate peatland. Micro-eukaryotic community in the tropical peatland was dominated by osmotrophs and distinguished by the high enzyme activities, decreased phenolics concentration, and with relatively high pH and DOC concentration.