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Typha latifolia paludiculture effectively improves water quality and reduces greenhouse gas emissions in rewetted peatlands

Vroom, Renske J.E., Xie, Fuju, Geurts, Jeroen J.M., Chojnowska, Aleksandra, Smolders, Alfons J.P., Lamers, Leon P.M., Fritz, Christian
Ecological engineering 2018 v.124 pp. 88-98
Azolla filiculoides, Typha latifolia, ammonium nitrate, belowground biomass, biomass production, carbon, carbon sequestration, crops, ecosystem services, flooded conditions, greenhouse gas emissions, greenhouse gases, land use, methane, methane production, nitrogen, nitrous oxide, nutrient uptake, peat, peat soils, peatlands, phosphorus, pollution load, potassium nitrate, surface water, uncertainty, urea, water quality
Paludiculture, the cultivation of crops on wet or rewetted agricultural peatlands, sustainably integrates productive land use with the provision of multiple ecosystem services. Paludiculture crops thrive under waterlogged conditions that stimulate nitrogen (N) and phosphorus (P) removal from soil and water and convert serious drainage-induced carbon (C) losses to C sequestration. Nutrient uptake by paludicrops can prevent mobilisation after rewetting and provide opportunities for purification of nutrient-rich water. Uncertainty remains, however, if and to what extent N loading and a subsequent increase in biomass productivity affect nutrient cycling as well as emissions of the potent greenhouse gases methane (CH4) and nitrous oxide (N2O). In this study, we use mesocosms with rewetted peat to investigate the effect of different N sources in surface water on biomass production of Typha latifolia, a typical paludiculture crop, and the emissions of CH4 and N2O. Organic (Azolla filiculoides; urea) or mineral (KNO3; NH4NO3) N was supplied either a single time (steady state) or repeatedly (pulse) to simulate a total surface water load of 150 kg N ha−1. We found that N stimulated aboveground and belowground biomass production and nutrient uptake by T. latifolia. These effects were absent in Azolla treatments. Whereas after two months CH4 emissions arose to substantial amounts (>10 mg CH4 m−2 day−1) in unvegetated mesocosms loaded with organic N, they remained very low (<1 mg CH4 m−2 day−1) in vegetated mesocosms, despite the labile C pool in the extensive belowground biomass and organic N loading. Overall, N2O emissions were close to zero and were only detected episodically after NO3− loading, irrespective of plant presence. Our findings support that T. latifolia as a paludicrop effectively removes various forms of N and P when harvested, and strongly mitigates CH4 emission after the rewetting of agricultural peat soils compared to unvegetated conditions.