Canadian Forest Service Publications

The origin of soil organic matter controls its composition and bioreactivity across a mesic boreal forest latitudinal gradient. Kohl, L., Philben, M., Edwards, K., Podrebarac, F. A., Warren, J., & Ziegler, S. E. (2018). Global change biology, 24(2), e458-e473.

Year: 2018

Issued by: Atlantic Forestry Centre

Catalog ID: 40429

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1111/gcb.13887

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Warmer climates have been associated with reduced bioreactivity of soil organic matter (SOM) typically attributed to increased diagenesis; the combined biological and physiochemical transformation of SOM. In addition, cross-site studies have indicated that ecosystem regime shifts, associated with long-term climate warming, can affect SOM properties through changes in vegetation and plant litter production thereby altering the composition of soil inputs. The relative importance of these two controls, diagenesis and inputs, on SOM properties as ecosystems experience climate warming, however, remains poorly understood. To address this issue we characterized the elemental, chemical (nuclear magnetic resonance spectroscopy and total hydrolysable amino acids analysis), and isotopic composition of plant litter and SOM across a well-constrained mesic boreal forest latitudinal transect in Atlantic Canada. Results across forest sites within each of three climate regions indicated that (1) climate history and diagenesis affect distinct parameters of SOM chemistry, (2) increases in SOM bioreactivity with latitude were associated with elevated proportions of carbohydrates relative to plant waxes and lignin, and (3) despite the common forest type across regions, differences in SOM chemistry by climate region were associated with chemically distinct litter inputs and not different degrees of diagenesis. The observed climate effects on vascular plant litter chemistry, however, explained only part of the regional differences in SOM chemistry, most notably the higher protein content of SOM from warmer regions. Greater proportions of lignin and aliphatic compounds and smaller proportions of carbohydrates in warmer sites' soils were explained by the higher proportion of vascular plant relative to moss litter in the warmer relative to cooler forests. These results indicate that climate change induced decreases in the proportion of moss inputs not only impacts SOM chemistry but also increases the resistance of SOM to decomposition, thus significantly altering SOM cycling in these boreal forest soils.

Plain Language Summary

Warmer climates have been associated with reduced reactivity of soil organic matter (SOM). In addition, studies have shown that ecosystem changes associated with long-term climate warming affect SOM properties due to changes in the composition of soil inputs. The importance of these factors acting on SOM properties as ecosystems experience climate-warming remains poorly understood. To explore the issue, we examined plant litter and SOM across a boreal forest in Atlantic Canada. The results of the study indicate that climate change induced decreases in moss inputs impact SOM make-up, and increase the resistance of SOM to soil break-down. These effects significantly alter SOM cycling in boreal forest soils.