Effect of different hydrological restoration measures in Aukstumala raised bog damaged by peat harvesting activities

Anthropogenic disturbance (drainage and peat harvesting works in adjacent area) accelerates water outflow from and mineralization of top peat layer in the raised bog of Aukstumala Telmological Reserve (Western Lithuania) thus inducing peatland degradation and promoting penetration of atypical plant species and woody vegetation. Possibilities of restoration of the most affected parts of the Aukstumala raised bog (contact zone of the bog and peat harvesting fields) were investigated. Specifically, we aimed to assess effectiveness of two different means of hydrological regime restoration installed in the contact zone: (i) bog isolation from peat harvesting fields (to prevent direct water runoff) using polyethylene membrane (PM measure, installed in November 2006) and "peat lock" system (PL measure: water runoff blocked by highly decomposed peat; installed in November 2010), and (ii) blocking of ditches of the old drainage system using peat dams (PD measure, installed in November 2012). The research was carried out by performing monthly (from April to October) water level measurements in a system of water level monitoring profiles installed in zones of impact of each measure and non-treated (control) areas. Moreover, dendrochronological analysis of pine growth was performed in PM-treated and control areas. Although in general positive effect of the applied treatments (raised water table, reduced amplitudes of seasonal water level fluctuation, reduced radial increment of pine trees, re-establishment of Sphagnum cover) could be observed, none of the three measures has fully restored hydrological regime to create favourable conditions for peat accumulation and thriving of typical raised bog communities. The results of the present study suggest that aiming to more efficiently regulate hydrological regime in drainage-affected parts of the Aukstumala raised bog, blocking or filling of the old drainage system should always be applied in combination with the installation of water insulation measures along the contact zone of the bog and peat harvesting fields. Longer observation time is needed to fully assess the effect of the installed restoration measures on hydrology and ecosystem functioning in the raised bog of Aukstumala Telmological Reserve