Search results for "Humus"
showing 10 items of 117 documents
Activity and role of the enchytraeid worm Cognettia sphagnetorum (Vejd.) (Oligochaeta: Enchytraeidae) in organic and mineral forest soil
2003
Summary Site preparation following clear felling of coniferous forest creates a mosaic of different kinds of habitats for soil decomposers, ranging from bare mineral soil to thick layers of organic soil and felling residues. To study whether the impact of enchytraeids on nutrient mineralisation processes is different in residues, organic layer, and mineral soil, a microcosm experiment was conducted in the laboratory. Microcosms contained mineral soil (sand) alone or with soil organic layer (humus and F-layer materials) and spruce needles, either separately or together. Enchytraeids (Cognettia sphagnetorum) were introduced to the half of the microcosms. Numbers of enchytraeids, their gut con…
Biodegradation of microplastic in freshwaters : a long‐lasting process affected by the lake microbiome
2022
Plastics have been produced for over a century, but definitive evidence of complete plastic biodegradation in different habitats, particularly freshwater ecosystems, is still missing. Using 13C-labeled polyethylene microplastics (PE-MP) and stable isotope analysis of produced gas and microbial membrane lipids, we determined the biodegradation rate and fate of carbon in PE-MP in different freshwater types. The biodegradation rate in the humic-lake waters was much higher (0.45±0.21% per year) than in the clear-lake waters (0.07±0.06% per year) or the artificial freshwater medium (0.02±0.02% per year). Complete biodegradation of PE-MP was calculated to last 100-200 years in humic-lake waters, …
Influence of littoral periphyton on whole-lake metabolism relates to littoral vegetation in humic lakes
2017
The role of littoral habitats in lake metabolism has been underrated, especially in humic lakes, based on an assumption of low benthic primary production (PP) due to low light penetration into water. This assumption has been challenged by recent recognition of littoral epiphyton dominance of whole-lake PP in a small highly humic lake and of epiphyton as an important basal food source for humic lake biota. However, as these studies have mostly concerned single lakes, there is a need to test their wider generality. We studied the whole-lake PP and community respiration (CR) in eight small humic lakes in southern Finland during July 2015 using 14C incorporation to measure pelagic PP and the ch…
Humus forms, carbon stock and properties of soil organic matter in forests formed on dry mineral soils in Latvia
2020
Over the last decades, more attention has been paid to carbon accumulation in soil, more recently, to soil humus forms, as they indicate environmental conditions and state of soil organic matter. There is insufficient information on the impact of soil and forest type on the chemical properties of soil, soil organic matter and humus form. Knowledge about the chemical properties of humus is crucial for modelling C and N accumulation and storage in forest soils. On this account, the aim of this study was to characterize soil humus forms, humus chemical properties and C stock and to determine the spatial distribution correlations between soil humus forms in forests formed on dry mineral soils. …
Complex-forming properties of peat humic acids from a raised bog profiles
2013
Abstract Humic substances (HS) belong to the most powerful complex-forming agents, significantly affecting major and trace element speciation in natural environment. Several authors have focused on humic–metal interactions, using differing methods and comparing humic substances on different sources. However, the intrinsic differences among the HS of different origin and the impact of humification degree on the complex formation between humic substances and metals have not received the necessary attention until now. The aim of this study is to determine the Cu(II) complexing capacity and stability constants of Cu(II) complexes of humic acids (HA) isolated from two well-characterized raised b…
Littoral energy pathways in highly humic boreal lakes
2017
Littoral zones in lakes are among the most productive habitats in the world, but have been seriously understudied, as most limnological studies have concerned only pelagic habitats. The likely importance of littoral zones in clear lakes is widely acknowledged, but in contrast their role in dystrophic humic lakes has generally been assumed to be minor. In this thesis, littoral importance in whole-lake metabolism was studied in small and highly humic lakes in Southern Finland, where Lake Mekkojärvi was the principal study lake. Primary production (PP) measurements revealed that littoral periphyton, growing on surrounding aquatic vegetation, can dominate the whole-lake PP, and the highly autot…
Bacterial-mediated terrestrial carbon in the foodweb of humic lakes
2007
Sami Taipale tarkasteli tutkimuksessaan metaanin merkitystä humusjärvien ravintoketjussa. Suurin osa Suomen järvistä lukeutuu humusjärviin, jotka ovat väriltään ruskehtavia. Koska metaani on 21 kertaa tehokkaampi kasvihuonekaasu kuin hiilidioksidi, on sen kohtalolla järvissä sekä järvien ravintoketjussa suuri merkitys ilmastonmuutoksen kannalta. - Metaania hapettavilla bakteereilla on merkittävä rooli humusjärvien ravintoketjussa, mutta myös globaalisti, sillä ne estävät suurelta osin voimakkaan kasvihuonekaasun, metaanin, pääsyn ilmakehään. Metaania hapettavien bakteerien merkitys korostunee tulevaisuudessa ilmaston lämmetessä, Taipale täsmentää. Uudet tutkimusmenetelmät, kuten vakaiden is…