Surface fluctuation in three virgin pine mires in eastern Finland.

A review is made of earlier work and theories on a formation of string mires, together with a report on detailed investigations carried out over seven years on a small string (aapa) mire in eastern Finland, to determine the applicability of earlier hypotheses on the explanation of string and pool patterning. Attention is paid to the topography of the surface and bottom of the mire and to the peat and pollen stratigraphy. Results are presented of year‐round temperature measurements and long sequences of snow and frost depth readings from both pools and strings. Snow depth is shown to be a decisive factor in ground frost formation. The strings are shown by a series of repeated Geodimeter measurements to move partly upslope, partly downslope and partly in a sideways direction. The maximum cumulative movement recorded was about 1 m in seven years. Some of the pools remained unfrozen even in midwinter because of groundwater flow. Uneven retention and discharge of the surface water causes the strings to be in a labile state and promotes their movement. The initial formation of the string and pool topography is dated to 2,000–3,000 radiocarbon years B.P. and attributed to a rise in the groundwater table due to climatic change. The resulting fluviodynamics of the mire surface led to the accumulation of loose material into ramparts at the spring flood season and led in time to differential peat formation conditions, progressive peat accumulation on the strings, and regressive peat degradation in the pools. Thus the strings became higher and the pools deeper. The authors believe the importance of frost action, ice expansion and solifluction on the development of string and pool patterns is frequently overestimated.

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“…In addition, any increase in the volume of water present will raise the surface of the mire while any decrease will lower it (cf. Kurimo 1983).…”

Section: Discussionmentioning

confidence: 99%

“…The fluctuations in the groundwater table, on the other hand, cause much greater rises and falls in the mire surface (cf. Kurimo 1983).…”

Section: Discussionmentioning

confidence: 99%

Formation of a string and pool topography as expressed by morphology, stratigraphy and current processes on a mire in Kuusamo, Finland

Seppälä

Koutaniemi

1985

Boreas

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“…The outset of the measuring period happened to be clearly moister than the end of the period in all the plots: the difference gives rough information about the height of the habitat surface in moist and dry conditions, although detailed, continuous measurements of the height fluctuations of the habitat surface (cf. Kurimo 1983) have not been conducted. The annual growth of Sphagnum, which in part contributes to the height of the surface in Sphagnum-dominated sites, was not specifically measured either.…”

Section: Determination Of Water Levelmentioning

confidence: 99%

Community and species responses to water level fluctuations with reference to soil layers in different habitats of mid-boreal mire complexes

2007

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The present paper discusses water level fluctuations in different parts of boreal mire complexes (eleven localities), mainly aapa mire complexes, on the basis of measurements performed by means of shallow observation wells and a few deeper observation tubes (piezometers) in the coastal half of the southern aapa mire zone in Finland. The sites represented intact vegetation from 12 different habitat types (communities), which were divided a priori into habitats with a stable surface moisture status (stable habitats) and into habitats with an unstable surface moisture status (unstable habitats). In stable habitats water level fluctuations took place according to the acrotelm-catotelm model, but the unstable habitats clearly deviated from the general pattern: water level fluctuations in them were not at all concentrated to the surficial, porous peat layer. Direct gradient analysis was used for arranging the communities along the water level fluctuation gradient. Variability of the water table, using 80% amplitude of water table residence, was used for the arrangement. The gradient was split into three groups: (1) habitats with a slightly fluctuating water table, (2) habitats with a considerably fluctuating water table and (3) habitats with an extremely fluctuating water table. The last group nearly corresponded to aro wetlands, and represented a very special habitat type. Indirect gradient analysis (NMDS ordination) also revealed the water level fluctuation gradient along with the gradient of traditional water level categories. According to the results of direct and indirect gradient analysis, the water level fluctuation seems to be an independent and important vegetation gradient. In peatlands, it occurs alongside with the traditional gradient of water level categories reflecting the mean water table. The responses of species to the range of water level fluctuations seem to reflect their tolerance to disturbances and evidently to seasonal drought. Most Sphagnum species are absent or in poor condition in habitats with extremely fluctuating water table. Vascular plant species that experienced most extreme water level fluctuations (Carex nigra, Juncus filiformis) have earlier been regarded as disturbance indicators. In addition, the difference between the piezometric water level and simultaneously measured water table depth reached the highest values within the habitats of those species (i.e., within Polytrichum commune aro wetlands) showing the downward direction of water movement in sandy mineral soil.

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“…In peatlands, the rise and fall of the surface, sometimes described as 'bog-breathing' (Kulczynski, 1949;Baden and Eggelsmann, 1964;Mustonon and Suena, 1971;Hutchinson, 1980;Kurimo, 1983;Almendinger et al, 1986;Price, 2003;Price and Schlotzhauer, 2003) is one of the key self-regulating feedback mechanisms providing resilience and maintaining function during periods of hydrological stress (Money and Wheeler, 1999;Waddington et al, 2015). This 'surface motion', which is a poro-elastic mechanical response to ecohydrological processes, results from the collapse and expansion of large pores in response to changes in the mass of water stored and associated stresses within the peat (Price, 2003).…”

Section: Introductionmentioning

confidence: 99%

Identification of typical eco-hydrological behaviours using InSAR allows landscape-scale mapping of peatland condition

Bradley¹,

Andersen

Marshall

et al. 2021

Preprint

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Abstract. Better tools for rapid and reliable assessment of global peatland extent and condition are urgently needed to support action to prevent their further decline. Peatland surface motion is a response to changes in the water and gas content of a peat body regulated by the ecology and hydrology of a peatland system. Surface motion is therefore a sensitive measure of ecohydrological condition but has traditionally been impossible to measure at the landscape scale. Here we examine the potential of surface motion metrics derived from InSAR satellite radar to map peatland condition in a blanket bog landscape. We show that the timing of maximum seasonal swelling of the peat is characterized by a bimodal distribution. The first maximum is typical of steeper topographic gradients, peatland margins, degraded peatland and more often associated with ‘shrub’-dominated vegetation communities. The second maximum is typically associated with low topographic gradients often featuring pool systems, and Sphagnum dominated vegetation communities. Specific conditions associated with ‘Sphagnum’ and ‘shrub’ communities are also determined by the amplitude of swelling and average multiannual motion. Peatland restoration currently follows a re-wetting strategy, however our approach highlights that landscape setting appears to determine the optimal endpoint for restoration. Aligning expectation for restoration outcomes with landscape setting might optimise peatland stability and carbon storage. Importantly, deployment of this approach, based on surface motion dynamics, could support peatland mapping and management on a global scale.

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Surface fluctuation in three virgin pine mires in eastern Finland.

Cited by 5 publications

References 0 publications

Formation of a string and pool topography as expressed by morphology, stratigraphy and current processes on a mire in Kuusamo, Finland

Formation of a string and pool topography as expressed by morphology, stratigraphy and current processes on a mire in Kuusamo, Finland

Community and species responses to water level fluctuations with reference to soil layers in different habitats of mid-boreal mire complexes

Identification of typical eco-hydrological behaviours using InSAR allows landscape-scale mapping of peatland condition

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