Browsing by Subject "paleohydrologia"

A significant amount of carbon has been stored in the northern peatlands during the Holocene. These peatlands are an important part of global carbon cycle by sequestering and releasing carbon dioxide (CO2) and methane (CH4) into the atmosphere. The development of high-latitude peatlands begun at the beginning of the Holocene, about 11,700 years ago after the retreat of the continental ice. To some extend, the carbon accumulation rate history has followed Holocene climate phases. Due to the high primary production during the warm periods, their carbon sequestration has been high and lower during the colder periods as primary production decreased. Perhaps the most important factor determining peatland carbon dynamics moisture conditions, i.e. water table depth. The climate is predicted to warm much faster in the north than elsewhere, making the northern peatlands particularly vulnerable to the effects of climate change. In the future, climate change is expected to change the humidity and temperature conditions, which likely affecting the carbon dynamics of the peatlands. However, the ultimate effects are not yet fully known. This thesis studies changes in the hydrological conditions of the subarctic Lompolojänkkä peatland in Finnish Lapland over the past 900 years. Based on a testate amoeba analysis of two peat profiles, a quantitative water table depth reconstruction was created using a transfer function based on the surface samples reference data. The supporting plant macrofossil data was available supplemented by chronology based on radiocarbon and lead dating. The results show that the hydrology of Lompolojänkkä has adapted changes in climate conditions over the past 900 years and the data show that the surface of the peatland is now drying. The observed current trend towards drier conditions is in line with previous observations from northern peatlands. Changes in the Lompolojänkkä's plant community indicate extensive peatland lateral growth as well as a small-scale development resembling fen-bog-transition. In contrast to prevailing understanding, changes in the testate amoeba community followed changes in the plant community. This may be due to relative change in water level whereas a result of warming the plant growth accelerated and peat accumulation increased, which resulted in deepening of water table depth. The number of testate amoebae in different peat layers gives the slightly conflicting indications of the development of the carbon sequestration capacity of the peatland over the time studied, and there are some uncertainties associated to applicability of such data. However, the observed vegetation shift suggests future increase in carbon sequestration potential in Lompolojänkkä.