Browsing by Subject "mineral soil"

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  • Kramarenko, Dmitri (Helsingfors universitet, 2012)
    In the carbon cycle carbon is sequestrated from the atmosphere through photosynthesis in vegetation, returned into soils as litter and released into atmosphere in decomposition as carbon dioxide. In the boreal zone a large proportion of the organic carbon is bound into soil. The aim of this study was to find out how the amount of soil organic carbon (SOC) has changed in Finnish forests in last 20 years by comparing results of empirical measurements from two projects (1986-1995 and 2006). The purpose of the study was also to analyze how well the field measurements of SOC collected in two consecutive periods of time are suitable for characterization of changes in the SOC stock. The effect of soil structure, vegetation type and climatic factors on possible SOC changes were also studied. The average size of SOC stock (organic layer + mineral layer 0-40cm) in Finnish forests is 5.65 kg C m-2. About one third of SOC is in the organic layer (2.10 kg C m-2) and the rest of it is in the mineral soil (3.56 kg C m-2 ). Higher amount of SOC stock in the organic layer has been determined on plots with thicker organic layer, poor drainage and the presence of peat mosses. Higher amount of SOC in the mineral layer has been measured on plots which have a more southerly location, lower stoniness and high proportion of fine textures. Coefficients of determination in General Linear Models were between 23-61%. The average annual change of SOC (organic layer + mineral layer 0-40 cm) is +33.9 g C m-2a-1. Change in the organic layer has been +11.4 g C m-2a-1 and in the mineral soil +22.5 g C m-2a-1. The accumulation of organic carbon into the organic layer is positively correlated with the thickness of the organic layer, the southern location, pine dominance in tree layer and the age of the trees, while in the mineral soil higher carbon accumulation occurs in less stony soils and in more southern locations. Coefficients of determination in General Linear Models describing the change in SOC were low, between 11-14%. The largest positive or negative changes in SOC are in plots where the depth of the organic layer measured in two successive measurements was very different. Also, the differences in the measurements of SOC were large if the plots were drained, divided to two different sections or plots were excessively moist. Climate change and higher temperature will probably affect soil carbon sequestration positively, forecasted by using the results of the south-north gradient in which more carbon was accumulated into the soils of southern Finland. Soil monitoring research should be developed by using precise sampling methods and establishing permanent instructions for field work in order to avoid additional sources of error and to minimize variation.
  • Harju, A. Vilhelmiina; Narhi, Ilkka; Mattsson, Marja; Kerminen, Kaisa; Kontro, Merja H. (2021)
    Views on the entry of organic pollutants into the organic matter (OM) decaying process are divergent, and in part poorly understood. To clarify these interactions, pesticide dissipation was monitored in organic and mineral soils not adapted to contaminants for 241 days; in groundwater sediment slurries adapted to pesticides for 399 days; and in their sterilized counterparts with and without peat (5%) or compost-peat-sand (CPS, 15%) mixture addition. The results showed that simazine, atrazine and terbuthylazine (not sediment slurries) were chemically dissipated in the organic soil, and peat or CPS-amended soils and sediment slurries, but not in the mineral soil or sediment slurries. Hexazinone was chemically dissipated best in the peat amended mineral soil and sediment slurries. In contrast, dichlobenil chemically dissipated in the mineral soil and sediment slurries. The dissipation product 2,6-dichlorobenzamide (BAM) concentrations were lowest in the mineral soil, while dissipation was generally poor regardless of plant-derived OM, only algal agar enhanced its chemical dissipation. Based on sterilized counterparts, only terbutryn appeared to be microbially degraded in the organic soil, i.e., chemical dissipation of pesticides would appear to be utmost important, and could be the first response in the natural cleansing capacity of the environment, during which microbial degradation evolves. Consistent with compound-specific dissipation in the mineral or organic environments, long-term concentrations of pentachloroaniline and hexachlorobenzene were lowest in the mineral-rich soils, while concentrations of dichlorodiphenyltrichloroethane (DTT) and metabolites were lowest in the organic soils of old market gardens. OM amendments changed pesticide dissipation in the mineral soil towards that observed in the organic soil; that is OM accelerated, slowed down or stopped dissipation.
  • Niemi, Suvi (Helsingfors universitet, 2012)
    Root and butt rot is the most harmful fungal disease affecting Norway spruce in southern Finland. In approximately 90 % of cases the causal agent is Heterobasidion parviporum. Root and butt rot infections have not been reported in Finnish peatlands. However, the increase in logging operations in peatlands means there is a risk that the fungus will eventually spread to these areas. The aim of this study was to find out the impact of growing site on the resistance of Norway spruce to Heterobasidion parviporum infections. This was investigated by artificially inoculating H. parviporum to spruce trees in pristine mire, drained peatland and mineral soil and comparing the defence reactions. Additionally, the effect of genotype on resistance was studied by comparing the responses of spruce clones representing different geographic origins. The roots and stems of the trees to be sampled were wounded and inoculated with wood dowels pre-colonised by H. parviporum hyphae. The resulting necrosis around the point of inoculation was observed. It was presumed that increased length of necrosis indicates high susceptibility of the tree to the disease. The relationship between growth rate and host resistance was also studied. The results indicated that growing site does not have a statistically significant effect on host resistance. The average length of necrosis around the point of inoculation was 35 mm in pristine mire, 37 mm in drained peatland and 40 mm in mineral soil. It was observed that growth rate does not affect resistance, but that the genotype of the tree does have an effect. The most resistant spruce clone was the one with Russian origin. The results suggest that the spruce stands in peatlands are not more resistant to root and butt rot infections than those in mineral soil. These findings should be taken into consideration when logging peatland forests.