The drawdown of the water level has been hypothesized to change peatlands from carbon sinks to C sources to the atmosphere as a result of increased oxidation of organic matter. We measured the change ...in peat thickness (subsidence of peat surface) ca. 60 years after drainage in 273 peatland sites (875 points) representing three nutrient levels of pine fens and five macroclimatic regions from southern to northern Finland, and we calculated the changes in peat C densities and peat C stores using direct measurements and estimates drawn from regression models for C density derived in this study. On average, the peat surface had subsided ca. 22 +/- 17 cm (mean +/- SD), the C density had increased by 26 +/- 15 kg.m-3, and the C stores had increased by 5.9 +/- 14.4 kg.m-2 after drainage. Therefore. the hypothesis that drainage of peatland always makes them sources of C to the atmosphere is incorrect. We concluded that the post-drainage subsidence of peat surface was mainly caused by changes in the physical structure of peat after the removal of water while the oxidation of peat was of less importance. The changes in C density and C stores seemed to be dependent on the input of new C into the system through net primary production, especially through the fine roots of trees. Our results suggest that tree stand development plays an important role in the post-drainage C balance of peat soils.
The purpose of this paper is to introduce the gas exchange measurement and flux calculation methods commonly used in the projects of the programme "Greenhouse gas emissions from the use of peat and ...peatlands in Finland". The methods include measurements of instantaneous fluxes of CO2, CH4 and N2O made at the ecosystem–atmosphere boundary using closed chamber, and whole ecosystem fluxes of the gases using micrometeorological EC tower extending above the canopy, and the integration of seasonal and annual fluxes. In addition, tools developed for gap filling of missing weather records, and generating complete weather patterns for the key environmental controls of the gas fluxes are introduced. Derivation of emission factors from the collected gas fluxes, capable of reproducing the dynamic, climate dependent nature is outlined.
We built an automatic chamber system to measure greenhouse gas (GHG) exchange in forested peatland ecosystems. We aimed to build a system robust enough which would work throughout the year and could ...measure through a changing snowpack in addition to producing annual GHG fluxes by integrating the measurements without the need of using models. The system worked rather well throughout the year, but it was not service free. Gap filling of data was still necessary. We observed problems in carbon dioxide (CO2) respiration flux estimation during calm summer nights, when a CO2 concentration gradient from soil/moss system to atmosphere builds up. Chambers greatly overestimated the night-time respiration. This was due to the disturbance caused by the chamber to the soil-moss CO2 gradient and consequent initial pulse of CO2 to the chamber headspace. We tested different flux calculation and measurement methods to solve this problem. The estimated flux was strongly dependent on (1) the starting point of the fit after closing the chamber, (2) the length of the fit, (3) the type of the fit (linear and polynomial), (4) the speed of the fan mixing the air inside the chamber, and (5) atmospheric turbulence (friction velocity, u*). The best fitting method (the most robust, least random variation) for respiration measurements on our sites was linear fitting with the period of 120–240 s after chamber closure. Furthermore, the fan should be adjusted to spin at minimum speed to avoid the pulse-effect, but it should be kept on to ensure mixing. If night-time problems cannot be solved, emissions can be estimated using daytime data from opaque chambers.
We built an automatic chamber system to measure greenhouse gas (GHG) exchange in forested peatland ecosystems. We aimed to build a system robust enough which would work throughout the year and could ...measure through a changing snowpack in addition to producing annual GHG fluxes by integrating the measurements without the need of using models. The system worked rather well throughout the year, but it was not service free. Gap filling of data was still necessary. We observed problems in carbon dioxide (CO.sub.2) respiration flux estimation during calm summer nights, when a CO.sub.2 concentration gradient from soil/moss system to atmosphere builds up. Chambers greatly overestimated the night-time respiration. This was due to the disturbance caused by the chamber to the soil-moss CO.sub.2 gradient and consequent initial pulse of CO.sub.2 to the chamber headspace. We tested different flux calculation and measurement methods to solve this problem. The estimated flux was strongly dependent on (1) the starting point of the fit after closing the chamber, (2) the length of the fit, (3) the type of the fit (linear and polynomial), (4) the speed of the fan mixing the air inside the chamber, and (5) atmospheric turbulence (friction velocity, u*). The best fitting method (the most robust, least random variation) for respiration measurements on our sites was linear fitting with the period of 120-240 s after chamber closure. Furthermore, the fan should be adjusted to spin at minimum speed to avoid the pulse-effect, but it should be kept on to ensure mixing. If night-time problems cannot be solved, emissions can be estimated using daytime data from opaque chambers.
We built an automatic chamber system to measure greenhouse gas (GHG) exchange in forested peatland ecosystems. We aimed to build a system robust enough which would work throughout the year and could ...measure through a changing snowpack in addition to producing annual GHG fluxes by integrating the measurements without the need of using models. The system worked rather well throughout the year, but it was not service free. Gap filling of data was still necessary. We observed problems in carbon dioxide (CO sub(2)) respiration flux estimation during calm summer nights, when a CO sub(2) concentration gradient from soil/moss system to atmosphere builds up. Chambers greatly overestimated the night-time respiration. This was due to the disturbance caused by the chamber to the soil-moss CO sub(2) gradient and consequent initial pulse of CO sub(2) to the chamber headspace. We tested different flux calculation and measurement methods to solve this problem. The estimated flux was strongly dependent on (1) the starting point of the fit after closing the chamber, (2) the length of the fit, (3) the type of the fit (linear and polynomial), (4) the speed of the fan mixing the air inside the chamber, and (5) atmospheric turbulence (friction velocity, u*). The best fitting method (the most robust, least random variation) for respiration measurements on our sites was linear fitting with the period of 120-240 s after chamber closure. Furthermore, the fan should be adjusted to spin at minimum speed to avoid the pulse-effect, but it should be kept on to ensure mixing. If night-time problems cannot be solved, emissions can be estimated using daytime data from opaque chambers.
Heterotrophic soil respiration (CO2 efflux from the decomposition of peat and root litter) in three forestry-drained peatlands with different site types and with a large climatic gradient from the ...hemi-boreal (central Estonia) to south (southern Finland) and north boreal (northern Finland) conditions was studied. Instantaneous fluxes varied between 0 and 1.3 g CO2-C m–2 h–1, and annual fluxes between 248 and 515 g CO2-C m–2 a–1. Variation in the annual fluxes among site types was studied only in the south-boreal site where we found a clear increase from nutrient-poor to nutrient-rich site types. More than half of the within-site variation was temporal and explained by soil surface (–5 cm) temperature (T5). The response of soil respiration to T5 varied between the sites; the most northerly site had the highest response to T5 and the most southerly the lowest. This trend further resulted in increased annual fluxes towards north. This unexpected result is hypothesised to be related to differences in site factors like substrate quality, nutrient status and hydrology but also to temperature acclimation, i.e., adaptation of decomposer populations to different climates.
The purpose of this study was to determine changes in nasal respiratory pattern with growth and development, particularly to determine the age where upper airway growth ceases. The results on 361 ...healthy subjects, aged 7 to 24 years, based on aerodynamic measurements during rest breathing, showed clear differences between inspiratory and expiratory phases. Nasal airflow rate and cross‐sectional area increased and oral‐nasal pressure and nasal resistance decreased with age up to the age of 16, levelling by the age of 20 years. The body size and gender had effect only on nasal airflow rate. This study suggests that the measurements of the nasal respiratory pattern, determining impaired nasal airway, should be done during inspiration and using age‐related assesment from a healthy population until the age of 16 years. From then on, guidelines for adults are applicable.
Methane (CH4) fluxes from drainage ditches and adjoining strips between the ditches were measured in fall 1995 at a drained mire in Finland. The fluxes were measured at different mire sites using ...static chambers (diffusion and plant-mediated transport) and inverted funnels (ebullition). The emissions (chamber measurements) of CH4 from drainage ditch bottoms, ditch sides, and strips between ditches ranged from 0 to 595 mg.m-2.d-1, from 0 to 78 mg m-2 d-1, and from -3 to 33 mg.m-2 d-1, respectively. The ebullition of CH4 from ditches was rather small, ranging from 3 to 37 mg CH4 m-2.d-1, which was less than 10% of the CH4 flux measured by the chambers. As the proportion of ditches of the total peatland area is rather small, the inclusion of methane fluxes from ditches would not considerably change the previous estimates of the effect of drainage on the greenhouse gas balance of Finnish peatlands.
Mitochondrial mutations have previously been reported anecdotally in families with maternally inherited, nonsyndromic hearing impairment. To ascertain the contribution of mitochondrial mutations to ...postlingual but early-onset, nonsyndromic hearing impairment, we screened patients collected from within two different populations (southern Italy and UK) for previously reported mtDNA mutations associated with hearing disorders. Primer extension (SNP analysis) was used to screen for specific mutations, revealing cases of heteroplasmy and its extent. The most frequently implicated tRNA genes, Leu(UUR) and Ser(UCN), were also sequenced in all Italian patients. All tRNA genes were sequenced in those UK patients showing the clearest likelihood of maternal inheritance. Causative mtDNA mutations were found in approximately 5% of patients in both populations, representing almost 10% of cases that were clearly familial. Age of onset, where known, was generally before adulthood, and hearing loss was typically progressive. Haplogroup analysis revealed a possible excess of haplogroup cluster HV in the patients, compared with population controls, but of borderline statistical significance. In contrast, we did not find any of the previously reported mtDNA mutations, nor a significant deviation from haplogroup cluster frequencies typical of the control population, in patients with late adult-onset hearing loss (age-related hearing impairment) from the UK or Finland.
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