Investigating whether light intensity can modify decomposition rates in peatlands through control of the ‘enzymic latch’

Abstract Root exudates released by vascular plants contain significant amounts of photosynthetically-derived low molecular weight carbon compounds and gases, such as oxygen. These compounds are reported to have a priming effect on the activity of soil microbes which, in turn, release extracellular soil enzymes. Rates of root exudation are known to correlate positively with photosynthesis rates. As such, we hypothesized that phenol oxidase activity in the rhizosphere of peatland plants could be manipulated by varying the intensity of light to which above ground biomass is exposed, in line with recent solar radiation management proposals of geoengineers. Since phenol oxidase plays a pivotal role in regulating biodegradation in peat soils, through a mechanism widely known as the ‘enzymic latch’, this approach was thought to have potential as an ecoengineering strategy designed to enhance carbon sequestration in these environments. Our experiment however, found little relationship between phenol oxidase activity and light intensity level for any of the plants analysed, although significant differences in enzyme activity were observed between plant species. It is argued therefore, that encouraging the growth of particular plant species may be more effective at enhancing carbon sequestration in peatlands than manipulating ambient light levels.