FraDiv Monitoring

The aim of the FraDiv^obs monitoring programme is to investigate the effects of ash dieback (ADB) disease on forest biocoenoses. At typical ash tree locations in Schleswig-Holstein (Northern Germany), we record the infestation situation of ash trees and relate the damage to the biodiversity of the stands. To this end, we have established a statewide monitoring programme in order to put the current extent of the ADB in relation to the respective environmental site conditions on a large scale. In addition, we can observe the effects of the ADB disease on the forest communities and the effects of associated forestry practice strategies over a larger period of time and document alterations of the ecosystem.

In spring 2019, we visited more than 400 potential sites throughout Schleswig-Holstein to assess their suitability for monitoring. The aim was to cover a representative selection of habitat types in which ash occurs and to integrate the landscape elements typical of Schleswig-Holstein (e.g. cliffs). In addition, forests with different forest utilisation intensities and known stands with occurrences of endangered or rare fungus species should be included in the data set. A great deal of information from the cooperation partners as well as from private individuals and public institutions was incorporated into this pre-selection.

In the next step, we selected 114 plots according to our criteria and set them up as permanent plots (hereinafter referred to as "plots"). The selected plots represent

• around 30 % each of the habitat types of alder-ash and alluvial forests (habitat types 91E0/91F0) and Asperulo-Fagetum beech forests rich in ash (habitat type 9130),
• around 20 % Sub-Atlantic and medio-European oak or oak-hornbeam forests of the Carpinion betuli forests (habitat type 9160) and Tilio-Acerion forests of slopes, screes and ravines (habitat type 9180).

Plots of 100 m² each were set up and permanently marked in each of the 114 forest stands by late summer 2020 in order to carry out a complete inventory:

• recording the composition of the moss, herb, shrub and tree layer (cover in per cent), structural factors, proportion of open soil, deadwood and stones
• mycological surveys by the FraDiv Myko team
• recording the damage to the existing adult ash trees on five individuals per plot: i) leaf loss (in %), ii) proportion of necrotic tissue at the base of the trunk, iii) presence of prolific epicormic shoots (yes/no), additional recording of secondary pathogens, so a categorisation into damage classes can be made according to the specifications of the Northwest German Forest Research Institute (NW-FVA; more on the inventory of damage can be found in the booklet "Kriterien zur Schadensbonitur” (Criteria for damage assessment, PDF in German only), which was developed as part of the FraxForFuture project in coordination with FraDiv)
• recording the damage to the young ash tree growth in the plot
• species detection and determination of the breast height diameter (BHD) of all tree individuals (BHD > 7cm) within the monitoring plot

Soil identification and soil sampling were carried out on all monitoring plots to characterise the soil chemical parameters. All monitoring plots were also equipped with data loggers for continuous measurement of soil moisture. At sites close to groundwater, the water level dynamics are also recorded with data loggers. By means of repeated light measurements on all plots, the direct influence of the ETS on the further canopy opening of old stands can also be recorded and the significance of the changed light conditions for the accompanying vegetation and forest regeneration and rejuvenation can be investigated.

A complete inventory of the floristic and mycological species of the ash-rich monitoring plots is now available. This data set represents the baseline situation for FraDiv. In the further course of the project, the development of the biocoenosis on these plots will continue to be observed to monitor success. By analysing this data, we want to help answer the following questions, among others

• Which factors determine the occurrence of rare and typical species of ash-rich forests (flora and fungi)?
• To what extent do abiotic and biotic factors (e.g. soil moisture, pH value, lime content, nutrient availability, tree species composition) influence the susceptibility of adult and young ash trees?
• What site and structural changes are associated with the various forestry measures in the course of the ADB disease and how do these affect biodiversity?

With repeated surveys of the herb layer and the occurring fungi in the further course of the project, we also want to record the extent to which the increasing loss of ash trees and the progressive thinning of the forest also affects the accompanying diversity of higher plants, fungi, mosses and lichens.

This project is funded by the Federal Agency for Nature Conservation with resources from the Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection.