Dominant Factors of the Nature Regulating CO2 Release from Boreal Forest Land

Temperature is often considered as a primary factor for microbial decomposition of soil organic carbon. Boreal forests are the large terrestrial carbon pool: if carbon stored in this region is transferred to the atmosphere as CO2 by a warming-induced acceleration of its decomposition, there will be positive feedback to global warming. It is reported that real issue regarding the release of carbon from soils to the atmosphere is how natural factors interact to influence decomposition of soil organic matter, so we observed mass losses (indicating decomposition rates) from litter and litterfall in a Northern Fennoscandia forest over 3 years under natural conditions. Our field survey has demonstrated that mass losses from most kinds of sample had moderate correlation with the temperature. Of the various samples, the canopy-gap litter alone had a greater rate (~70%) of mass loss. It is at least necessary to make a clear distinction of monitoring sites (under the canopy and in the canopy gap) when discussing the effect of climate on soil CO2 release from high-latitude forests. Though temperature, soil moisture and soil properties are prioritized in the issue of soil CO2 release, our results suggest that the fungi/bacteria rate and the wind-related mix/fragmentation are also important factors to be considered;however, this speculation is just tentative, and more detail research is called for.

The seasonal dynamics of geochemical characteristics of sediments in the impact zone of the fish farm(Lake Ladoga,Russia)

This study focuses on the analysis of seasonal dynamics of physicochemical parameters(pH and Eh)and organic matter content in the sediments accumulated within the impact zone of the cage trout farm(Lake Ladoga,Russia).The Ladoga is the largest lake in Europe and there are more than 20 fish farms located in the northern part of the waterbody.The geochemical research is necessary for predicting the negative impact of the polluted sediments on both the cage fish and the aquatic ecosystem.The sampling was conducted during various seasons of the year(February,June,August,October)which were characterized by the different fish feeding regimes.The sediment cores were collected at 7 points,including the cage and reference sites(150 m and 600 m far from the farm).The results showed that the accumulation of organic material released from the studied fish farms was local and the wastes did not enter the sediments at the control sites.Furthermore,the accumulated organic layer can be compacted and partially mineralized during winter period.Nevertheless,strongly reducing conditions in sediments occur due to the accumulation of organic material and low rate of water exchange within the studied bay.Therefore,there is a potential risk of formation of toxic gases and release of accumulated nutrients and metals from sediments to water.It can have a negative impact on benthic and nekton organisms,in particular cage fish.