Spatial Variability of Sediment Nutrient Storage Across Restored and Undisturbed Wetland Habitats

The sediments in wetlands are reservoirs of carbon, nitrogen, and phosphorus, although their concentrations vary significantly depending on the particular habitat, making it difficult to assess the success of a restoration project based on reference data from undisturbed wetlands. This paper investigates how the nutrient storage in wetland sediments varies depending on the particular habitat and how these differences are related to the data on nutrient storage in undisturbed wetlands. The concentration of total carbon, total nitrogen, and total phosphorus in surface sediments was calculated for each particular habitat separately within three sequential cell treatment wetlands, two restored floodplain wetlands and adjacent croplands, and was evaluated using a systematic literature review of twelve scientific articles published from 2014 until 2022. Carbon stocks ranged from 27.5 to 46.5 g kg⁻¹ and nitrogen from 2.60 to 3.90 g kg⁻¹, with the richest ecosystems storing up to 69 % and 50 % more carbon and nitrogen, respectively, than croplands. Phosphorus stocks had a different distribution, varying from 499 to 831 mg kg⁻¹, with the values being lower in three out of five studied wetlands, so that there was almost no correlation between phosphorus stocks and those of carbon and nitrogen (correlation coefficient between carbon and nitrogen r = 0.99; correlation coefficient between carbon and phosphorus r = 0.24). Literature review suggests that restored wetlands tend to be behind their natural analogues with regard to carbon and nitrogen for about one to two decades. Thus, monitoring programmes have to sample habitats separately and assess nutrient stocks independently.