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Nitrate reduction capacity is limited by belowground plant recovery in a 32‐year‐old created salt marsh
Author(s) -
Tatariw Corianne,
Mortazavi Behzad,
Ledford Taylor C.,
Starr Sommer F.,
Smyth Erin,
Griffin Wood Abigail,
Simpson Loraé T.,
Cherry Julia A.
Publication year - 2021
Publication title -
restoration ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.214
H-Index - 100
eISSN - 1526-100X
pISSN - 1061-2971
DOI - 10.1111/rec.13300
Subject(s) - salt marsh , denitrification , biogeochemical cycle , environmental science , ecosystem , biomass (ecology) , nitrate , organic matter , marsh , environmental chemistry , nutrient cycle , ecology , wetland , chemistry , nitrogen , biology , organic chemistry
Human activities have decreased global salt marsh surface area with a subsequent loss in the ecosystem functions they provide. The creation of marshes in terrestrial systems has been used to mitigate this loss in marsh cover. Although these constructed marshes may rapidly recover ecosystem structure, biogeochemical processes may be slow to recover. We compared denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates between a 32‐year‐old excavation‐created salt marsh (CON‐2) and a nearby natural reference salt marsh (NAT) to assess the recovery of ecosystem function. These process rates were measured at 5 cm increments to a depth of 25 cm to assess how plant rooting depth and organic matter accumulation impact N‐cycling. We found that, for both marshes, denitrification and DNRA declined with depth with the highest rates occurring in the top 10 cm. In both systems, N‐retention by DNRA accounted for upwards of 75% of nitrate reduction, but denitrification and DNRA rates were nearly 2× and 3× higher in NAT than CON‐2, respectively. Organic matter was 6× lower in CON‐2, likely due to limited plant belowground biomass production. However, there was no response to glucose additions, suggesting that the microbial functional community, not substrate limitation, limited nitrate reduction recovery. Response ratios showed that denitrification in CON‐2 recovered in surficial sediments where belowground biomass was highest, even though biomass recovery was minimal. This indicates that although recovery of ecosystem function was constrained, it occurred on a faster trajectory than that of ecosystem structure.