H. Vasander | University of Helsinki (original) (raw)
Papers by H. Vasander
ABSTRACT After a peatland has been harvested, the remaining bare surfaces are often difficult to ... more ABSTRACT After a peatland has been harvested, the remaining bare surfaces are often difficult to restore to a functional peat accumulating system. Recolonisation by typical bog vegetation is a first step in this process, but is often problematic due to the changed physico-chemical, hydrological and ecological properties of the remaining peat. Within RECIPE, a European Union Framework 5 initiative, we have aimed to identify those combinations of site physico-chemical conditions, vegetation composition and below-ground microbiological characteristics that are beneficial to the long-term regeneration of cut-over peatland biodiversity and restoration of the carbon sink function. The first experimental phase of this project entailed a baseline study of cut-over peatlands at various stages in the regeneration process in five European countries. We present here the relationships of various soil processes with these regeneration stages and discuss these data in the context of both current management practices and future options for peatland management, taking into account feasibility and overall socio-economic effects.
Ecology, 2008
Present tropical peat deposits are the outcome of net carbon removal from the atmosphere and form... more Present tropical peat deposits are the outcome of net carbon removal from the atmosphere and form one of the largest terrestrial organic carbon stores on the Earth. Reclamation of pristine tropical peatland areas in Southeast Asia increased strikingly during the last half of the 20th century. Drainage due to land-use change is one of the main driving factors accelerating carbon loss from the ecosystem. Dams were built in drainage-affected peatland area canals in Central Kalimantan, Indonesia, in order to evaluate major patterns in gaseous carbon dioxide and methane fluxes and in peat hydrology immediately before and after hydrologic restoration. The sites included peat swamp forest and deforested burned area, both affected by drainage for nearly 10 years. Higher annual minimum soil water table levels prevailed on both sites after restoration; the deforested site water table level prevailed considerably longer near the peat surface, and the forest water table level remained for a longer period in the topmost 30 cm peat profile after restoration. Forest soil gas fluxes were clearly higher in comparison to the deforested area. Cumulative forest floor CO2 emissions (7305-7444 g x m(-2) x yr(-1); 166.0-169.2 mol CO2 x m(-2) x yr(-1)) and the deforested site CO2 emissions (2781-2608 g x m(-2) x yr(-1); 63.2-59.3 mol CO2 x m(-2) x yr(-1)) did not markedly reflect the notably differing hydrological conditions the year before and after restoration. The forest floor was a weak CH4 sink (-0.208 to -0.368 g x m(-2) x yr(-1); -13.0 to -22.9 mmol CH4 x m(-2) x yr(-1)) and the deforested site a comparable CH4 source (0.197-0.275 g x m(-2) x yr(-1); 12.3-17.1 mmol CH4 x m(-2) x yr(-1)) in the study period. In general, higher soil water table levels had a relatively small effect on the annual CH4 emission budgets. In the two site types the gas flux response into hydrological conditions in degraded tropical peat can be attributed to differing CO2 and CH4 dynamics, peat physical characteristics, and vegetation.
Wetlands Ecology and Management, 2016
Tropical peat carbon compound composition (CCC) is a highly understudied subject. Advanced unders... more Tropical peat carbon compound composition (CCC) is a highly understudied subject. Advanced understanding of peat CCC and carbon dynamics in differing conditions is desperately needed due to large-scale utilization of these peatlands. We studied the CCC—i.e. the hemicellulosic carbohydrate and uronic acid composition and concentrations of extractives, cellulose, acid-soluble lignin and acid-insoluble lignin—in association with peat profile depth and physical structure of peat, under representative, common land uses. Samples were gathered from an undrained forest and three sites altered 20–30 years prior to the study, which in aggregate form a continuum of increasing land-use intensity (drainage-affected forest; drained and deforested degraded open site; drained and deforested site under cultivation) in Central Kalimantan, Indonesia. Peat samples were taken from depths between 10 and 115 cm that covered mostly oxic, frequently waterlogged and permanently waterlogged, anoxic conditions. Our results demonstrated greater modification of peat properties when both vegetation and hydrological conditions were altered. The differences between sites were mainly present in the topmost peat and decreased with depth. Peat located at the surface contained more labile compounds (hemicelluloses, extractives, uronic acids, cellulose) on forest sites than at the most intensively altered open sites, where peat was enriched with recalcitrant acid insoluble lignin. The effect of drainage was evident in the drained forest site, where at the approximate median water table depth peat more closely resembled open sites in terms of the peat properties. The increased recalcitrance of peat in reclaimed areas has been a result of enhanced decomposition, reduced litter input rates and, at open sites also by repeated fires.
Memoranda - Societatis pro Fauna et Flora Fennica
Archiv für Protistenkunde, 1992
The distribution of 38 testacean species (Protozoa: Rhizopoda) and a rotifer, Habrotrocha angusti... more The distribution of 38 testacean species (Protozoa: Rhizopoda) and a rotifer, Habrotrocha angusticollis (Rotifera: Bdelloidea) were analyzed by range and weighted average ordination techniques of seven chemical and four physical variables from 90 microsites in virgin mires in southern Finland. Both living and dead individuals were counted and the absolute numbers of individuals per unit area were determined. The absolute numbers varied from 13 to 2300 individuals/cm3. All species or species groups but one, Lesquereusia spiralis, a species of nutrient-rich fen microsites, were found to occur in ombrotrophic sites. Only three species (Arc ella discoides, Bullinu/a indica, and Heleopera syfvatica) were not found in eutrophic sites, whereas the remaining taxa were widely distributed across the ecological gradient from ombrotrophic to eutrophic microsites. Three species, Amphitrema wrightianum, Arcella discoides, and Hya/osphenia e/egans were found to be in very low numbers in Sphagnum. All other testacean species were found to be well represented in both Sphagnum and Bryales mosses.
ABSTRACT Since the last deglaciation, 300-500 Pg carbon have accumulated in northern peatlands (3... more ABSTRACT Since the last deglaciation, 300-500 Pg carbon have accumulated in northern peatlands (346 mill. ha). While sequestering carbon dioxide (CO2), these peatlands release considerable amounts of methane (CH4) to the atmosphere. The greenhouse-gas balance of peatlands may change in the future if summers become warmer and drier, as has been predicted for high latitudes. Subsequent emissions of CH4 would decrease, whereas emissions of CO2 and nitrous oxide (N2O) would increase. Water-level drawdown has been predicted to enhance the greenhouse impact from northern peatlands. The components of carbon cycling were measured both in undrained and drained peatlands of different trophic levels. The results were drawn together into a single radiative forcing factor, to assess the combined atmospheric effects of water-level drawdown. We present a hypothesis, based on the measured changes in carbon stores in soil and tree stand, and fluxes of CO2 CH4 and N2O after water-level drawdown caused by drainage for forestry. The hypothesis suggests that possible drying arising from climate change would, in fact, decrease the impact of northern peatlands on the total radiative forcing for about one hundred years by c. 0.1 W m-2. This is caused by the decrease in CH4 emissions, fairly small changes in the peat carbon storage, and increase in the tree-stand biomass storage.
ABSTRACT After a peatland has been harvested, the remaining bare surfaces are often difficult to ... more ABSTRACT After a peatland has been harvested, the remaining bare surfaces are often difficult to restore to a functional peat accumulating system. Recolonisation by typical bog vegetation is a first step in this process, but is often problematic due to the changed physico-chemical, hydrological and ecological properties of the remaining peat. Within RECIPE, a European Union Framework 5 initiative, we have aimed to identify those combinations of site physico-chemical conditions, vegetation composition and below-ground microbiological characteristics that are beneficial to the long-term regeneration of cut-over peatland biodiversity and restoration of the carbon sink function. The first experimental phase of this project entailed a baseline study of cut-over peatlands at various stages in the regeneration process in five European countries. We present here the relationships of various soil processes with these regeneration stages and discuss these data in the context of both current management practices and future options for peatland management, taking into account feasibility and overall socio-economic effects.
Ecology, 2008
Present tropical peat deposits are the outcome of net carbon removal from the atmosphere and form... more Present tropical peat deposits are the outcome of net carbon removal from the atmosphere and form one of the largest terrestrial organic carbon stores on the Earth. Reclamation of pristine tropical peatland areas in Southeast Asia increased strikingly during the last half of the 20th century. Drainage due to land-use change is one of the main driving factors accelerating carbon loss from the ecosystem. Dams were built in drainage-affected peatland area canals in Central Kalimantan, Indonesia, in order to evaluate major patterns in gaseous carbon dioxide and methane fluxes and in peat hydrology immediately before and after hydrologic restoration. The sites included peat swamp forest and deforested burned area, both affected by drainage for nearly 10 years. Higher annual minimum soil water table levels prevailed on both sites after restoration; the deforested site water table level prevailed considerably longer near the peat surface, and the forest water table level remained for a longer period in the topmost 30 cm peat profile after restoration. Forest soil gas fluxes were clearly higher in comparison to the deforested area. Cumulative forest floor CO2 emissions (7305-7444 g x m(-2) x yr(-1); 166.0-169.2 mol CO2 x m(-2) x yr(-1)) and the deforested site CO2 emissions (2781-2608 g x m(-2) x yr(-1); 63.2-59.3 mol CO2 x m(-2) x yr(-1)) did not markedly reflect the notably differing hydrological conditions the year before and after restoration. The forest floor was a weak CH4 sink (-0.208 to -0.368 g x m(-2) x yr(-1); -13.0 to -22.9 mmol CH4 x m(-2) x yr(-1)) and the deforested site a comparable CH4 source (0.197-0.275 g x m(-2) x yr(-1); 12.3-17.1 mmol CH4 x m(-2) x yr(-1)) in the study period. In general, higher soil water table levels had a relatively small effect on the annual CH4 emission budgets. In the two site types the gas flux response into hydrological conditions in degraded tropical peat can be attributed to differing CO2 and CH4 dynamics, peat physical characteristics, and vegetation.
Wetlands Ecology and Management, 2016
Tropical peat carbon compound composition (CCC) is a highly understudied subject. Advanced unders... more Tropical peat carbon compound composition (CCC) is a highly understudied subject. Advanced understanding of peat CCC and carbon dynamics in differing conditions is desperately needed due to large-scale utilization of these peatlands. We studied the CCC—i.e. the hemicellulosic carbohydrate and uronic acid composition and concentrations of extractives, cellulose, acid-soluble lignin and acid-insoluble lignin—in association with peat profile depth and physical structure of peat, under representative, common land uses. Samples were gathered from an undrained forest and three sites altered 20–30 years prior to the study, which in aggregate form a continuum of increasing land-use intensity (drainage-affected forest; drained and deforested degraded open site; drained and deforested site under cultivation) in Central Kalimantan, Indonesia. Peat samples were taken from depths between 10 and 115 cm that covered mostly oxic, frequently waterlogged and permanently waterlogged, anoxic conditions. Our results demonstrated greater modification of peat properties when both vegetation and hydrological conditions were altered. The differences between sites were mainly present in the topmost peat and decreased with depth. Peat located at the surface contained more labile compounds (hemicelluloses, extractives, uronic acids, cellulose) on forest sites than at the most intensively altered open sites, where peat was enriched with recalcitrant acid insoluble lignin. The effect of drainage was evident in the drained forest site, where at the approximate median water table depth peat more closely resembled open sites in terms of the peat properties. The increased recalcitrance of peat in reclaimed areas has been a result of enhanced decomposition, reduced litter input rates and, at open sites also by repeated fires.
Memoranda - Societatis pro Fauna et Flora Fennica
Archiv für Protistenkunde, 1992
The distribution of 38 testacean species (Protozoa: Rhizopoda) and a rotifer, Habrotrocha angusti... more The distribution of 38 testacean species (Protozoa: Rhizopoda) and a rotifer, Habrotrocha angusticollis (Rotifera: Bdelloidea) were analyzed by range and weighted average ordination techniques of seven chemical and four physical variables from 90 microsites in virgin mires in southern Finland. Both living and dead individuals were counted and the absolute numbers of individuals per unit area were determined. The absolute numbers varied from 13 to 2300 individuals/cm3. All species or species groups but one, Lesquereusia spiralis, a species of nutrient-rich fen microsites, were found to occur in ombrotrophic sites. Only three species (Arc ella discoides, Bullinu/a indica, and Heleopera syfvatica) were not found in eutrophic sites, whereas the remaining taxa were widely distributed across the ecological gradient from ombrotrophic to eutrophic microsites. Three species, Amphitrema wrightianum, Arcella discoides, and Hya/osphenia e/egans were found to be in very low numbers in Sphagnum. All other testacean species were found to be well represented in both Sphagnum and Bryales mosses.
ABSTRACT Since the last deglaciation, 300-500 Pg carbon have accumulated in northern peatlands (3... more ABSTRACT Since the last deglaciation, 300-500 Pg carbon have accumulated in northern peatlands (346 mill. ha). While sequestering carbon dioxide (CO2), these peatlands release considerable amounts of methane (CH4) to the atmosphere. The greenhouse-gas balance of peatlands may change in the future if summers become warmer and drier, as has been predicted for high latitudes. Subsequent emissions of CH4 would decrease, whereas emissions of CO2 and nitrous oxide (N2O) would increase. Water-level drawdown has been predicted to enhance the greenhouse impact from northern peatlands. The components of carbon cycling were measured both in undrained and drained peatlands of different trophic levels. The results were drawn together into a single radiative forcing factor, to assess the combined atmospheric effects of water-level drawdown. We present a hypothesis, based on the measured changes in carbon stores in soil and tree stand, and fluxes of CO2 CH4 and N2O after water-level drawdown caused by drainage for forestry. The hypothesis suggests that possible drying arising from climate change would, in fact, decrease the impact of northern peatlands on the total radiative forcing for about one hundred years by c. 0.1 W m-2. This is caused by the decrease in CH4 emissions, fairly small changes in the peat carbon storage, and increase in the tree-stand biomass storage.