The methods for analysing chemical, physical, microbiological and zoological soil properties are summarised in Table 2. At each permanent plot,
a soil profile is dug and analysed according to Hoffmann (1991). Soil types are characterised following the standardised methods (AG Boden 1994, AG Stadtboden 1997). Microbiological parameters are analysed in mixed soil samples.
Vegetation is sampled in 10×10 m2 plots. Each has four subplots of 1×1 m2. Cover of plant species is estimated in absolute percentages. In the subplots, individuals of all plant species are counted. Special funnel traps were designed for capturing the diaspore rain (Fig. 1). They are emptied every two weeks. The diaspore bank of the top soil layer is sampled at depths of 0-2, 2-5 and 5-10 cm using a metal cylinder (500 cm3). Half of the material is studied using the “seed washing by sieve” method, the other half using the “seed emergence” method according to Fischer (1987). For the latter, diaspores are sown on a sterilised soil matrix and observed for a four-week period.
Fig. 1. Construction of the diaspore trap (after Haeupler et al. 2003)
On each permanent plot, the locations of all trees are established to create structure maps of the stand (Leder and Leonhardt 2003). Additionally, the height of the trees, their diameter at breast height (dbh) and their social positions are recorded, using the classification method of Kraft (1884). This classification describes the rank of a tree in comparison to its neighbours by recording the form of its crown. The classes are: (1) superior, (2) dominant, (3) co-dominant, (4) intermediate, and (5) overtopped. For the demographic analysis, saplings with a height of more than 1 m are considered.
By digging up the roots, information about mycorrhiza and root growth is obtained. The analysis will be completed by documenting historical development, and by analysing annual rings and aerial photographs.
The permanent plots are sampled for wild bees, sphecids, hoverflies (syrphids), ants and ground beetles. These groups are chosen because of their suitability as bio-indicators. The ecological requirements of the groups are well known, their lifestyles are adapted to all studied succes – sional stages, with differing habitat requirements within each group. They can be assigned to different trophic levels and use more than one habitat type or habitat structure during their life cycle.
In this paper, only ground beetles and ants are considered. For sampling ground beetles, pitfall traps are used (6 traps per plot; standing time 3×3 weeks per year). In addition, some beetles are caught manually at random. Ant nests are mapped in two 50 m2 partial areas per sample plot. The ant studies are completed by manual catches within the total sample plot, in pitfall traps used for ground-beetle mapping, using litter-layer sieving in woodland plots, net catches within higher vegetation and manual catches at random. Due to annual fluctuations in populations, samplings of two consecutive years are evaluated as one investigation unit with a regular repeti-
tion every five years. The initial recording was carried out in 2000/2001. An additional investigation was carried out in 2003.