Seasonal fluctuations of the rusty carbon sink in thawing permafrost peatlands

In permafrost peatlands, up to 20% of total organic carbon (OC) is bound to reactive iron (Fe) minerals in the active layer overlying intact permafrost, potentially protecting OC from microbial degradation and transformation into greenhouse gases (GHG) such as CO2 and CH4. During the summer, shifts in runoff and soil moisture influence redox conditions and therefore the balance of Fe oxidation and reduction. Whether this “rusty carbon sink” is stable or continuously dissolved by Fe(III) reduction and reformed by Fe(II) oxidation during redox shifts remains unknown. We exposed ferrihydrite (FH)-coated sand in the active layer along a permafrost thaw gradient in Stordalen mire (Abisko, Sweden) over the summer (June to September) to capture changes in redox conditions and quantify formation and dissolution of reactive Fe(III) (oxyhydr)oxides and associated OC. We found that Fe(III) minerals formed under the constantly oxic conditions in palsa soils overlying intact permafrost over the full summer season. In contrast, in fully-thawed fen areas, conditions were continuously anoxic and by late summer 50.4% of the original Fe(III) (oxyhydr)oxides were lost via dissolution while 44.7% and 4.9% of the Fe remained as Fe(III) and Fe(II) on the sand, respectively. Periodic redox shifts (from 0 mV to +300 mV) were observed over the summer season in the partially-thawed bog due to changes in active layer depth, runoff and soil moisture. This resulted in dissolution and loss of 47.5% of initial Fe(III) (oxyhydr)oxides and release of associated OC in early summer when conditions are wetter and more reduced, and new formation of Fe(III) minerals (34.7% gain in comparison to initial Fe) in the late summer under more dry and oxic conditions which again sequestered Fe-bound organic carbon. Our data suggests that the so-called rusty carbon sink is seasonally dynamic in partially-thawed permafrost peatlands, thus likely either promoting or suppressing carbon mineralization and leading to seasonal changes in GHG emissions.

Sivas- Koyulhisar Orman (Fagus Orientalis Lipsky.) Toprakları ile Tarım Topraklarının Karbon Mineralizasyonu Yönünden Karşılaştırılması

In this study, the dynamism of forest areas was tried to be determined by determining the ecological differences between the areas where Fagus orientalis Lipsky. (Eastern beech, Fagaceae), a very important species for forestry in Turkey, and the soils of agricultural fields. lime %, total salt %, pH, texture, field capacity %, C%, N%, C/N ratios, 30-day carbon mineralization of the lands of Eastern beech forests and agricultural fields, which are naturally formed in Sivas province Koyulhisar district, under controlled conditions (28°C, 80 humidity %) was determined by the respiration method, and two areas in two different ecosystems were compared. When the carbon mineralizations of eastern beech soils were examined seasonally, it was determined as 19.54>18.23>17.87>17.18 mg C(CO2)/100g DS/30 day in spring>autumn>summer>winter seasons, while it was determined as 14.46>13.87>13.68>13.65 mg C(CO2)/100g DS/30 day in autumn>summer>spring>winter seasons in agricultural soils, respectively. Significant relationships were found between the C%, N%, 30-day carbon mineralization cumulative values and % carbon mineralization rates between both areas.

Determination of the Effects of Copper (Cu) and Lead (Pb) Heavy Metals on Soil Carbon and Nitrogen Mineralization

Heavy metal (HM) pollution has become one of the most important environmental problems of the present day, as a result of the developing industrial activities. Accordingly, it is important to understand microorganism activities in soil ecosystems that have been exposed to HMs for a long time. The aim of this study was to show the potential effects of ores on soil carbon and nitrogen mineralizations which were taken from copper (Cu) and lead (Pb) mines in Balıkesir-Balya and Kastamonu-Küre districts in Turkey. The carbon (C) and nitrogen (N) mineralizations were determined by using the CO2 respiration method (30 days) and the Parnas Wagner method (42 days) under the controlled laboratory conditions (28 °C, 80% of field capacity), respectively. It was observed that carbon mineralization decreased depending on the dose increase. 250 mg kg-1 treatment with Pb was lower than the control and there was a significant difference between them (P < 0.001). In terms of nitrogen mineralization rate (%), there was no significant difference among all treatments. According to the results, Pb affected microorganisms more negatively; however, the presence of Cu slightly decreased its negative effect. It is possible to conclude that carbon mineralization can be indicator for HM pollution in the soil. However, nitrogen mineralization was not a determining factor at HM pollution in this study.