Soil carbon may be maintained under grazing in a St Lawrence Estuary tidal marsh

Abstract

SUMMARYProduction of belowground organic matter is critical to sustainability of salt marshes. It plays a role in vertical soil accretion, a process essential for salt marshes to maintain their relative elevation and persist as sea levels rise. This paper examines belowground production and soil carbon of a high-latitude saltmarsh in the St Lawrence Estuary (Québec, Canada), which had been subjected to six years of sheep grazing. In the seventh year, without sheep, organic matter production in grazed and ungrazed sections was assessed by examining harvests of plant litter, end-of-season standing crop, and the roots and rhizomes present in in-growth cores. Excepting salinity, porewater chemistry varied little. The grazed marsh had higher soil carbon density and belowground production, yet lower aboveground biomass. Grazing reduces plant litter and increases solar exposure, soil temperature (at this latitude, soil remained frozen until April) and evapotranspiration, thus raising soil salinity and nitrogen demand, the latter a driver of root production. Grazing may not be detrimental to soil carbon storage. Permitting certain types of grazing on restored salt marshes previously drained for agriculture would provide economic incentive to restore tidal flooding, because the natural carbon sink provided in the recovered marsh would make these lands eligible for carbon payments.

Interactions between ecosystem properties and land use clarify spatial strategies to optimize trade-offs between agriculture and species conservation

“…SOC should increase with nutrient availability and ANPP (Bateman et al 2013;Conti & Díaz 2013;Doblas Miranda et al 2013). Increasing biomass removal should decrease ANPP (Lienin & Kleyer 2012), but may increase or conserve SOC due to compensatory growth of roots and rhizomes (Yu & Chmura 2009;Piñeiro et al 2010;Paula & Pausas 2011). Conversely, we expect a reduction in SOC where land-use intensification is accompanied by high levels of fertilization (Van Wesemael et al 2010).…”

Comparison of Three Methods for the Quantification of Sediment Organic Carbon in Salt Marshes of the Rubicon Estuary, Tasmania, Australia

“…Applying the quadratic equation of Craft et al (1991) to LOI results using exposure times and temperatures outside of those specified by Craft et al (1991), has been tested previously (Connor et al, 2001;Chmura et al, 2003;Yu & Chmura, 2010). The equation has allowed re-evaluation of previous studies reporting organic matter values, by allowing organic carbon percentages to be determined without further sample analysis (Chmura et al, 2003).…”

“…A common method used to quantify carbon stores in sediment is a conversion variable, used to convert organic matter content data into organic carbon values (Allen, Grimshaw, Parkinson & Quarmby, 1974;Craft et al, 1991;Chmura et al, 2003;Pribyl, 2010;Yu & Chmura, 2010;Drexler, 2011). The Loss on Ignition (LOI) method is a simple and relatively inexpensive method used to estimate organic matter, though the temperature and length of time for best estimation of organic matter loss varies (Mook & Hoskin, 1982;Pribyl, 2010).…”

Bottom‐up and top‐down human impacts interact to affect a protected coastal Chilean marsh

“…In the United States and Canada, free‐ranging feral horses and lamb not only directly decrease salt marsh primary production, but also indirectly affect intertidal and subtidal animal communities (Furbish and Albano , Levin et al. , Yu and Chmura ). There are also reports of livestock grazing impacts on Chinese salt marshes (Zhao et al.…”