Drained-forest Restoration Experiment (DREX)
DREX was established in 2013 in cooperation with the State Forest Management Service. It comprises a replicated BACI (before-after-control-impact) experimental design for assessing the impacts of ditch filling and thinning treatments on the habitat quality of drained forests, with 64 plots covering a total of ca. 3 km2. The focal species of DREX is Capercaillie (Tetrao urogallus), but the experiment is addressing a wide range of basic and applied research issues regarding drained forested wetlands. The scientific issues addressed in the project include: (i) the composition, key factors, and dynamics of the novel assemblages of drained forests; (ii) wet-forest restoration pathways and techniques, including a comparison of ecosystem- and species-based targets; (iii) multi-criteria restoration planning, including ecological, economic and social targets and co-effects, conflicts between targets, and information requirements. The pre-surveys last from April 2013–August 2014 and the experimental manipulations will be carried out in autumn-winter 2013/2014.
The originally mixotrophic mire sites are situated in two adjacent forest massives, which have been densely ditched (ditches 110–150 m apart) in the 1960s and 1980s, respectively. Before drainage, about half of the sites had been semi-open and their forest cover only developed post drainage. Currently, the sites thus represent different stand ages and levels of transformation into decayed-peatland type, with peat depths ranging from 0.2 to >1.5 m. Water-level measurements confirm that there is tight connection between peat depth and the water level. The plots are arranged as paired four-plot clusters where one cluster is subjected to ditch filling (bordered with red on the map) while the other serves as control. The four plots represent randomly assigned harvest treatments (shades of grey on the map): removal of undergrowth; patchy removal of 5–20% of trees together with the undergrowth; uniform thinning of up to 30% of trees together with the undergrowth; control. The cluster sizes range from 12 to 32 ha and there are four cluster-pairs in each forest massive.
- restoration of historical key factors vs. creating habitat stucture using novel disturbance: what, when, and where works best for the Capercaillie?
- the role of environmental filtering and dispersal limitation in the post-drainage development of plant, fungal and bird assemblages in forests;
- biodiversity value of drained peatland forests, and its assessment for landscape planning.
PhD projects involved
- Elin Soomets “Focal species in wetland management: comparing the restoration of naturalness and creation of novel habitats“
Publicity [in Estonian]
- Lõhmus, A., Kohv, M., Ligi, K., Ojaste, I., Saag, P., Saarma, U., Valdmann, H. 2014. Metsise elupaigakvaliteedi kompleksuuring. [Ettekanne RMK teaduskonverentsil, 14.02.2014.]
- Käärt, U. 2013. Kadumisohtu sattunud metsiste elupaigad lähevad uuenduskuurile. Eesti Päevaleht, 11.06.2013.
- Mets, R. 2013. Enim kaitstud linnu arvukus üha väheneb. Tartu Postimees, 30.11.2013.
DREX has been established in the frame of the project LLOOM13051 “Integrative study of habitat quality factors for the Capercaillie (Tetrao urogallus)” (2013–2015) funded by the State Forest Management Service, who will also carry out the habitat manipulations in the field.
Photo 1. A typical DREX site: mid-aged pine forest, 35 years post drainage. Photo: A. Lõhmus, 03.07.2013.
Photo 2. The hydrology in DREX will be restored by ditch filling. The expected immediate view will probably resemble this experimental site in Northern Latvia. Photo: A. Lõhmus, 30.04.2013.
Photo 3. Simple thinning may not be sufficient for restoring the Capercaillie habitat because dense undergrowth will develop in only few years on drained lands. Photo: A. Lõhmus, 19.05.2013.