Current issue: 54(2)
Under compilation: 54(3)
Habitat loss and degradation are the main threats to biodiversity worldwide. For example, nearly 80% of peatlands in southern Finland have been drained. There is thus a need to safeguard the remaining pristine mires and to restore degraded ones. Ants play a pivotal role in many ecosystems and like many keystone plant species, shape ecosystem conditions for other biota. The effects of mire restoration and subsequent vegetation succession on ants, however, are poorly understood. We inventoried tree stands, vegetation, water-table level, and ants (with pitfall traps) in nine mires in southern Finland to explore differences in habitats, vegetation and ant assemblages among pristine, drained (30–40 years ago) and recently restored (1–3 years ago) pine mires. We expected that restoring the water-table level by ditch filling and reconstructing sparse tree stands by cuttings will recover mire vegetation and ants. We found predictable responses in habitat structure, floristic composition and ant assemblage structure both to drainage and restoration. However, for mire-specialist ants the results were variable and longer-term monitoring is needed to confirm the success of restoration since these social insects establish perennial colonies with long colony cycles. We conclude that restoring the water-table level and tree stand structure seem to recover the characteristic vegetation and ant assemblages in the short term. This recovery was likely enhanced because drained mires still had both acrotelm and catotelm, and connectedness was still reasonable for mire organisms to recolonize the restored mires either from local refugia or from populations of nearby mires.
Altitude fluctuation of mire surface proportional to that of the groundwater table is presented for three virgin pine mires in Eastern Finland during the growing season 1982. The average amplitude of the surface fluctuation was found to be dependent on the period representing a certain type of weather, being limited to a certain maximum. The average amplitude of the surface fluctuation ranged from 18 to 45 mm; each of the mires followed a fluctuation scale of its own.
The daily fluctuation rates were low, generally 0.5–1 mm. No sudden fluctuation peaks occurred. Regularities in the surface fluctuation were caused by the duration of the period representing continuous sinking or rise of the groundwater table, and magnitude of it. The daily rate of the surface fluctuation related to that of the groundwater table was smaller in the beginning of such period than at the end of the same period. The one-directional rise or sinking of the altitude of the mire surface according to the groundwater table fluctuation is responsible for the autocorrelation of the long-term regression data.
The PDF includes a summary in Finnish.
Fertility of surface peat from sedge pine mires was studied by measuring several edaphic growth factors: bulk density, volume weight of organic matter, ash content, acidity, electric conductivity, effective cation exchange capacity, degree of base saturation, and total contents of N, P, K, Ca and Mg. The 168 temporal sample plots were situated on virgin sedge mires in different parts of Finland, and the 30 permanent sample plots on two uniform sedge mires.
The results showed that peat bulk density and volume weight of organic matter tend to increase with increasing site quality. Ash content increased gradually in the site series from small sedge mire to the herb-rich sedge mire. The relationship between the total content of macronutrients in peat and the site quality is clear. The importance of bulk density in evaluating the site quality is further emphasized when taking into account its significant correlation to contents of N and P. The soil variables follow the accepted quality gradient of the site series. Consequently, the plant sociologically based site classification seems to reflect satisfactorily the average soil properties. However, the within site variation was significant.