Hydrological dynamics, wetland morphology and vegetation structure determine riparian arthropod communities in constructed wetlands

The data consists of data collected by 41 constructed wetlands in southern Sweden, where water level measurements were conducted between April 2020 and February 2023, and where vegetation height, grazing animal presence/absence, and flooded grassland area was measured in 2020. The data also includes collected abundances of riparian arthropods that were captured using SLAM (Sea Land and Air Malaise) trapping, pitfall trapping and vacuum sampling at three times during the spring and summer of 2020; late May, late June to early July and late August to early September. The arthropods were identified to genus level for spiders, beetles, predatory diptera and tipulidomorphs, whereas the remaining taxa were identified to family level. 

Methods
Arthropod collections

During three periods of spring and summer of 2020 (late May, late June to early July and late August to early September, we collected riparian arthropods by the wetland using three capturing techniques. SLAM (Sea Land and Air Malaise) traps were placed <2m from the water edge during three nights at all collection periods whereas triplicate 70mm diameter pitfall traps were used during May collections, along a 10m gradient parallel to the wetland shoreline within 5m of the SLAM trap. Both SLAM and pitfall traps contained soapy water as the killing agent. Vacuum sampling was performed in late June to early July and late August to early September using a converted Stihl™ BG85 Leaf blower in triplicate along a 10m gradient parallel to the wetland shoreline delineated with a 45cm diameter hoop, where samples were manually collected using a pooter, after evacuating the contents into a collection container. All arthropod samples were stored in 70% ethanol and were later identified to orders, with selected taxa being identified to lower taxonomic levels. For analysis, we focused on taxa that were sufficiently abundant by including taxa with >100 total individuals and being present in >70% of the sites.

Hydrological measurements

To calculate hydrology dynamics in the constructed wetlands, we deployed a pressure sensor transducer (ETM DeltaBlue with barometric pressure sensor) at the deepest point of each wetland that measured the differential pressure between the water and air to measure the water depth at a 60-minute interval between April 2020 and February 2023. The measurements were wirelessly transmitted to a server from which daily mean water levels were calculated. These were later converted to meters above sea level, calibrated to July 2020 measurements, and combined with 1m2 digital elevation models (DEMs, downloaded from SLU geodataportalen-Lantmäteriet on 2023-02-28) of each wetland (QGIS, ver. 3.26.3). By combining water levels and DEM pixel values we calculated wetland flood zone areas around the entire wetland, inundation frequency in a 10m radius around the SLAM  trap. We also calculated the maximum number of days the water level was above half way between the average water level and the SLAM trap and the maximum number of days the water level was below the lower 5%-percentile as maximum high- and low-water table duration. 

Vegetation height and grazing management

When performing vacuum collections of arthropods during August 2020, we also measured the maximum vegetation height at each collection point from which we calculated the average maximum vegetation height, and grazing management was determined by presence or absence of grazing livestock around each wetland.