Boreal peat properties link to plant functional traits of ecosystem engineers

Abstract

Plant species shape soil properties such as nutrient availability and carbon storage through functional traits. Understanding the role of plant functional traits, and the relationship between aboveground and belowground systems are especially important in boreal peatlands, which are important carbon sinks. Sphagnum as a key peat-forming bryophyte has long been considered an ecosystem engineer, whereas the engineering role of graminoids, also dominant in peatlands, has not traditionally been considered. We quantified vegetation community composition, plant functional traits, and peat properties in two peatland sites differing in dominant vegetation (Sphagnum mosses and Carex sedges), and link plant traits with peat properties using ordination. We show that plant traits significantly explain many peat properties, including organochemicals that are indicators of decomposition dynamics. Specifically, Carex-dominated sites had larger amount of ‘decomposition products’ while a larger proportion of ‘undecomposed materials’ was observed in Sphagnum-dominated sites. Feedbacks in plant-soil systems are increasingly being recognised as drivers of ecosystem processes. In both peatland types, plant traits of the key ecosystem engineer drove properties of the belowground peat environment. Peat organochemical constituents between Sphagnum-dominated and Carex-dominated sites reveal differences in ecosystem function, and thus the conducive potential for carbon storage.