Mineral dust as a driver of carbon accumulation in northern latitudes

Abstract

Peatlands in northern latitudes sequester one third of the world’s soil organic carbon. Mineral dusts can affect the primary productivity of terrestrial systems through nutrient transport but this process has not yet been documented in these peat-rich regions. Here we analysed organic and inorganic fractions of an 8900-year-old sequence from Store Mosse (the “Great Bog”) in southern Sweden. Between 5420 and 4550 cal yr BP, we observe a seven-fold increase in net peat-accumulation rates corresponding to a maximum carbon-burial rate of 150 g C m−2 yr−1 – more than six times the global average. This high peat accumulation event occurs in parallel with a distinct change in the character of the dust deposited on the bog, which moves from being dominated by clay minerals to less weathered, phosphate and feldspar minerals. We hypothesize that this shift boosted nutrient input to the bog and stimulated ecosystem productivity. This study shows that diffuse sources and dust dynamics in northern temperate latitudes, often overlooked by the dust community in favour of arid and semi-arid regions, can be important drivers of peatland carbon accumulation and by extension, global climate, warranting further consideration in predictions of future climate variability.

Phosphorus supply affects long-term carbon accumulation in mid-latitude ombrotrophic peatlands

“…Large databases of peat C and N profiles have been compiled, which link accumulation rates to climate drivers and floral stratigraphy 1,[13][14][15] , but phosphorus measurements are restricted to a handful of individual case studies [16][17][18][19] . These present evidence that occasional, localised injections of P-enriched dust 20 or tephra 19,21 triggered short-lived spikes in C accumulation. The extent to which spatially variable P supply controlled the long-term functioning of mid-latitude ombrotrophic peatlands has not yet been explored.…”

“…Nevertheless, we are aware of no independent estimates of regional atmospheric P emission and deposition through the Holocene and Brahney et al 48 model pre-industrial global atmospheric P transfers using fluxes directly proportional to 20 th -century values. The spatial pattern presented in Figure 5 represents a different biogeochemical response to that of large, abrupt injections of nutrients, such as local dust input 20 or tephra 19,21 . These events stimulate rapid carbon accumulation as ecosystem productivity ramps up but fertilisation effects are fairly short-lived (a few centuries).…”

“…These events stimulate rapid carbon accumulation as ecosystem productivity ramps up but fertilisation effects are fairly short-lived (a few centuries). Indeed long-term P accumulation rates are low in bogs in southern Sweden (Figures 3, 5) despite receiving episodic pulses of nutrient-enriched dust sourced locally during the mid-Holocene 20 .…”

Procedure for Organic Matter Removal from Peat Samples for XRD Mineral Analysis

“…This is achieved by comparing XRD data of samples with different levels of pre-treatment: no pre-treatment; thermal combustion at 300, 350, 400, 450, 500 and 550°C; and wetchemical oxidation using either H 2 O 2 or Na 2 S 2 O 8 . We used peat samples from a stratigraphic sequence from Store Mosse (SM) and a composite sample from Dumme Mosse (DM), two ombrotrophic bogs located in southern Sweden which are detailed elsewhere (Bindler 2003;Kylander et al 2013Kylander et al , 2016Kylander et al , 2018. To verify the effects of the different pre-treatments, known clay mineral standards were added to bulk samples prior to the different pre-treatments.…”

A regime shift from erosion to carbon accumulation in a temperate northern peatland

“…As we note above, mining activity in the region around the field site coincided with revegetation and peat accumulation, and an increase in Fe and K concentrations in the peat. Mining dust can increase the base mineral input and nutrient supply to peatlands (Gałka, Szal, Broder, Loisel, & Knorr, 2019; Ireland, Clifford, & Booth, 2014), and there is evidence of high C accumulation rates related to dust supply (Kylander et al., 2018). On bare, eroding peat surfaces, input of mineral‐rich dust can promote the growth of minerotrophic wetland plant species (e.g.…”