Aarhus University Seal / Aarhus Universitets segl

No. 73: Monitoring the vegetation recovery in Østerild Plantage 2015. Part 2

Wind, P. 2016. Monitoring the vegetation recovery in Østerild Plantage 2015. Part 2. Aarhus University, DCE – Danish Centre for Environment and Energy, 44 pp. Technical Report from DCE – Danish Centre for Environment and Energy No. 73 dce2.au.dk/pub/TR73.pdf

Summary

The overall objective of the monitoring program in Østerild is to document the succession of the vegetation cover as an outcome of the restoration project targeting open dune habitats following the clear-cutting of parts of the dune plantations at the National Test Centre facility. The first phase of the monitoring program, performed in July, 2011, included recording plant species composition and soil conditions prior to the clearing of the dune plantations (the baseline monitoring).

Sample areas and plots for the baseline monitoring were established in 2011 in a stratified random way in order to cover the variation in the development of the vegetation and the restoration measure that was described in the implementation plan. Stratification was applied according to the baseline condition (forest type), planned post-cutting treatments of litter layer, and the hydrology, the expected management regimes, the distance to appropriate seed sources, and the topography in the deforested area.

During the first 10 years following the clear-cutting, systematic monitoring of the vegetation cover to follow the succession towards open dune habitat types (post-construction monitoring) has been planned. The results of the monitoring program will, as far as possible, contribute to the recommendations for future restoration projects, which aim to convert plantations of especially conifer trees in dune areas into light open habitats that have previously prevailed in the areas.

In 2015, the third monitoring phase was initiated. The results of the third phase are presented in the report. The third phase was performed by re-monitoring the vegetation cover in the dune area formerly dominated by Pinus mugo. The 2011 monitoring methodology was repeated (Nygaard et al. 2011). The method is based on the variables in the Danish NOVANA program for terrestrial habitats (Fredshavn et al. 2015). The plant species composition and vegetation structure were recorded in a pin point frame (0.5 * 0.5 m2). Additional species were recorded in a documentation circle with a radius of 5 m for each of the twenty sample plots.

In the twenty sample plots monitored in 2015, 64 taxa of vascular plant species, bryophytes and lichens were recorded, ranging between twelve and 27 taxa in each plot. The most frequent species was Avenella flexuosa recorded in nineteen sample plots. Other abundant species were Carex arenaria, Dicranum scoparium, Empetrum nigrum, Hypnum jutlandicum and Pleurozium schreberi. Two species, Hypochaeris radicata andRumex acetosella, which each were recorded as additional species in one sample plot in 2011, were recorded in one and nine sample plots in 2013 and in fourteen and eleven sample plots in 2015, respectively. The rest of the 64 taxa were either recorded one, two, or three times in the pin point frames, or solely as additional species in the documentation circles.

The recorded species were also aggregated in nine different more or less systematic groups, where the number of species was compared between the three years. The species number has clearly improved in the group of broad-leaved herbal species, the grasses and the rushes and sedges. Thus, the vegetation cover has become more species rich due to the lighter conditions following the deforestation and, after an initial stage, has become denser, as the frequency of bare litter and naked sand recorded in the pin point frames between 2011 and 2015 has decreased.

The disturbance of the soil layer caused by cutting of the trees and removing the trunks and the stumps may lead to the release of nutrients that can favour problematic vascular plant species that prefer higher nutrient levels in the soil than originally present in the P. mugo plantation or to a flourishment of invasive species. In 2015, two problematic species, Epilobium angustifolium and Sencio sylvaticus, were recorded in the sample plots. As the two species were only recorded in a few, scattered populations they are not considered as a serious problem and will probably not become dominant in the long term.