Phosphorus Speciation in Long-Term Drained and Rewetted Peatlands of Northern Germany

Abstract

Previous studies, conducted at the inception of rewetting degraded peatlands, reported that rewetting increased phosphorus (P) mobilization but long-term effects of rewetting on the soil P status are unknown. The objectives of this study were to (i) characterize P in the surface and subsurface horizons of long-term drained and rewetted percolation mires, forest, and coastal peatlands and (ii) examine the influence of drainage and rewetting on P speciation and distributions using wet-chemical and advanced spectroscopic analyses. The total P was significantly (p < 0.05) different at the surface horizons. The total concentration of P ranged from 1022 to 2320 mg kg−1 in the surface horizons and decreased by a factor of two to five to the deepest horizons. Results of the chemical, solution 31P nuclear magnetic resonance (NMR), and P K-edge X-ray absorption near-edge structure (XANES) indicated that the major proportions of total P were organic P (Po). In the same peatland types, the relative proportions of Po and stable P fractions were lower in the drained than in the rewetted peatland. The results indicate that long-term rewetting not only locks P in organic matter but also transforms labile P to stable P fractions at the surface horizons of the different peatland types.Soil Syst. 2020, 4, 11 2 of 20 dynamic and may be taken up by microbes and plants, lost by leaching and drainage, and form secondary P minerals [8,9]. Thus, a complete account of P species is required to predict the P mobilization or stabilization potential in long-term drained and rewetted peatland types [10,11].Phosphorus transformations can vary according to management practices, peatland types, topographic positions, historic, and current land use types [12]. For instance, when a peat soil predominated by redox-sensitive elements is rewetted, P mobilization and release of soluble P species can occur by the reductive dissolution of binding partners of phosphate, especially pedogenic Fe-(oxy)hydroxides [6,13,14]. However, there is no information on the influence of long-term drainage and rewetting of percolation mires, forest, and coastal peatlands.Traditional wet chemical and advanced spectroscopic analytical techniques such as sequential P fractionation, solution 31 P nuclear magnetic resonance (NMR), and X-ray absorption near edge structure (XANES) spectroscopy have been used successfully to investigate P species in mineral soils and other environmental samples [15]. However, none of these analytical techniques can decipher P species independently because of the complex chemical and biochemical processes of P such as dissolution-precipitation, sorption-desorption, mineralization-immobilization, and oxidation-reduction [16]. Thus, the combined use of wet chemical and spectroscopic analytical techniques could provide detailed information on the impacts of management practices on various P species distributions and transformations.About 30,000 ha of degraded peatlands have been rewetted in Mecklenburg-West Pomerania, northern German since the mid-1...

Transformation of phosphorus forms and its regulation on phosphorus availability across differently degraded marsh soils

“…The most remarkable changes in P forms due to marsh degradation was an increase in organic P concentration and proportion, and organic P became the predominant P form in surface soils in Zoige, which is consistent with the results of the Min River Estuary, China (Zhang et al, 2015). However, some studies have revealed that the concentration and proportion of organic P in wetland soils decreased because cultivation and drainage stimulated the transformation from organic P to inorganic P and increased organic P loss (Negassa et al, 2020;Schlichting et al, 2002;Wang et al, 2006). Negassa et al (2020) demonstrated that the proportion of organic P was higher in long-term rewetted peatlands than in drained peatlands.…”

“…The forms of P in soils generally exhibit evident variations owing to the differences and changes in the pedogenic environments of wetlands, such as parent material, hydrothermal, and vegetation conditions (Cheesman et al, 2010(Cheesman et al, , 2012Cui et al, 2019b;Negassa et al, 2020;Qu et al, 2021;Wang et al, 2016a). Presently, climate change, rodent harm, and human disturbances such as drainage, overgrazing, and aquaculture have led to the degradation of more than half of wetlands worldwide to some degree (Huisman et al, 2017;Nguyen et al, 2016;Ren et al, 2019;Zuquette et al, 2020), which has completely altered the conditions of hydrology, salinity, vegetation, and soil characteristics in some wetland ecosystems (Cheng et al, 2020;Li et al, 2022;Zeng et al, 2021;Zhao et al, 2017a).…”

“…This has further affected soil P accumulation and its forms via P transformation processes such as sorption/desorption, precipitation/dissolution, immobilisation/mineralisation, and weathering (Augusto et al, 2017;Barrow, 2015;Khosa et al, 2021;Qu et al, 2021;Smith et al, 2021). For example, cultivation and drainage stimulated the transformation of organic P to inorganic P and decreased organic P in freshwater wetlands of the Sanjiang Plain region, China (Wang et al, 2006), and in peatland wetlands of Mecklenburg-West Pomerania and Saxony-Anhalt, Germany (Negassa et al, 2020;Schlichting et al, 2002), resulting in reduced P accumulation. Grazing increased soil P accumulation in wetlands within the dairy pasture of the Okeechobee Basin wetlands in the United States (Dunne et al, 2011).…”

Phosphorus Behaviour and Its Basic Indices under Organic Matter Transformation in Variable Moisture Conditions: A Case Study of Fen Organic Soils in the Odra River Valley, Poland

“…Although peat formation is a slow process, rewetting a degraded area may be the most appropriate way to reduce CO2 (and other greenhouse gases) emissions from peat oxidation [87]. Rewetting can enable drained peatlands to become peat-forming ecosystems and turn them again into sinks for soil carbon and nutrients (including P, which-in the course of long-term rewetting-is not only locked in organic matter but also transformed from labile P to stable P fractions at the surface horizons of the different peatland types) [88,89]. The goal of peatland rewetting is to achieve a persistent and stable saturation of the peat body with water by raising the water table to the peat surface and reducing the water level fluctuations [90].…”

Understanding the Ecology of Restored Fen Peatlands for Protection and Sustainable Use

“…Potential long-term influences of rewetting on phosphorus species were analyzed by Negassa et al [5] using traditional chemical and advanced spectroscopic methods. This indicated that rewetting could result in larger proportions of organic phosphorus and stable phosphorus fractions in the surface horizons of rewetted fens, compared to their degraded counterparts.…”