Dynamics of dissolved carbon and nitrogen in decomposing boreal mor and peat as affected by enchytraeid worms

Abstract

Export of dissolved organic carbon and nitrogen (DOC and DON) from terrestrial ecosystems to watercourses has increased in the boreal zone. However, the effects of decomposing material and soil food webs on the release rate and quality of DOC and DON are poorly known. The objective of this study was to quantify the release of carbon (C) and nitrogen (N) from mor and peat, which are the most common organic soil types in the boreal zone. The impact of soil fauna on the release processes was also estimated. Decomposition products were divided into intermediate products (DOC and DON) and mineralised end products, i.e. carbon dioxide (CO2-C) and ammonium (NH4 + -N). The release of C and N into the soil solution, extractable pools, and CO2-C efflux were measured. DOC and DON were further divided into high molecular weight (HMW) and low molecular weight (LMW) fractions.Carbon release was slightly different in each soil type. In absolute terms, the peat released less C and in relative terms more DOC than mor. Enchytraeids worms (Cognettia sphagnetorum) affected the quantity and composition of the decomposition products by enhancing mineralisation and the release of HMW-DOC.In the slightly decomposed peat, the net release of N occurred in the form of DON, whereas the other soil types mainly released NH4 + -N. The slightly decomposed peats are typically located close to water bodies, in the topmost soil layer, where the water discharge is the highest. Therefore, the slightly decomposed peats might have an important role in controlling the quality and quantity of N export.The results were used to further develop the decomposition model ROMUL to account for DOC and DON processes and the division between intermediate and end products. The parameterisation and structure of the model was analysed by means of the GLUE (Generalised Likelihood Uncertainty Estimation) method, and several simultaneously measured variables, which is novel in this research field.

Temperature sensitivity patterns of carbon and nitrogen processes in decomposition of boreal organic soils – Quantification in different compounds and molecule sizes based on a multifactorial experiment

“…Temperature sensitivity patterns were evaluated for each soil type and soil faunal treatment. This study continues the works presented by Laurén et al [27] and Lappalainen et al [5,28], who demonstrated the role of soil fauna and soil type on different C and N release rates but did not study the effect of abiotic factors, such as temperature and moisture on C and N release.…”

“…The studies by Conant et al [45] and Hamdi et al [46] suggest that C release rate at the beginning of incubation is highest but stabilizes after the labile C has been consumed (approximately after 50 days). Our previous experiments [5,27,28] with the same soil types show that the compound storage in the repeated measurements change linearly between 50 to 180 days of incubation. Linearity allowed us to use a single value, the rate of storage change (γ), as a response variable in the further analyses, thus facilitating a balanced comparison of different treatments and compounds.…”

“…In boreal soils, enchytraeid worms such as Cognettia sphagnetorum are functionally the most important faunal group [22,23,24,25]. Enchytraeid worms can double the CO 2 and DOC release from temperate peat soil [26] and significantly enhance N, CO 2 , and DOC release from boreal organic soils [5,27,28]. The temperature sensitivity of worm activity is largely unknown; however, it is likely that the function of soil fauna responds to temperature change and is therefore indirectly linked with GHG balance.…”

Improving Nitrogen Availability on a Tropical Peat Soil Cultivated with Ananas comosus L. Merr. Using Pineapple Residue Ash

“…The high soil water enabled rapid transport of water and mobilization of nutrients. Retention of ammonium and nitrate following fertilization might have been influenced by organic nitrogen mineralization and nitrification driven by many microorganism pathways that occur mainly at the upper part of (Jauhiainen et al 2012a;Lappalainen et al 2013;Martínez et al 2018). The control treatments (T5 and T6) did not improve ammonium and nitrate ion retention throughout the pineapple growth period because soil acidity restricts nitrification and mineralization of organic nitrogen to ammonium ions.…”

“…Because ammonium ions are attracted to negatively charged soil colloids of peat soils, they do not leach rapidly like potassium. However, ammoniums are relatively unstable in drained peat soils because they are rapidly converted to nitrate (Lappalainen et al 2013).…”