Crane fly diversity in Danish forest wetlands

Dataset description
The dataset contains field data on crane flies and environmental conditions collected in 2017 from four forest sites in eastern Denmark. Each site included paired managed and unmanaged stands, with sampling conducted across three habitat types: dry forest, wet forest patches, and drainage ditches. A total of 110 circular plots were established, where crane flies were sweep-netted twice during the summer and identified to species level.

For each plot, a range of explanatory variables were recorded, focusing on vegetation, soil, and forest structure. Ellenberg indicator values for light (Ellen_L), moisture (Ellen_F), soil pH (Ellen_R), and nitrogen (Ellen_N) were derived from plant composition in 5 m radius subplots. Additional variables include wetland size (ha), diameter of the largest tree in the plot (as a proxy for disturbance and continuity), and mean organic soil layer depth.

Key variables

• ID: Unique identifier for each plot.

• Site: Forest site name.

• Stand: Stand within site.

• Management: Managed or unmanaged forest.

• Treatment: Habitat type (dry forest, wet forest, drainage ditch).

• Stand_treat: Combined stand and treatment code.

• Ellen_L / Ellen_F / Ellen_R / Ellen_N: Ellenberg indicator values for light, moisture, pH, and nitrogen.

• Wetland_size: Area of wetland (ha).

• Large_tree_size: Diameter of largest tree in plot (cm).

• Organic_layer_avg: Average depth of organic soil horizon (cm).