Monitoring grassland’s arthropods in a in situ climate change experimentation (Terceira, Azores, Portugal)

Study Extent

he study was conducted in three intensive pastures on the island of Terceira (Azores). On each field, 20 plots (1x1m) were set up in an area of 100m2 where cattle were not allowed. Among those 20 plots, 10 were randomly chosen to be delimited by an OTC’s (in order to simulate an increase of +1.2ºC average), while the other 10 were considered as control plots (Picture 1). OTC’s were built including a 1m2 plot and a margin of 25cm all around. The aim of this margin was to allow the same setting up of the pitfall as in the control plots (e.g. 1 pitfall trap at each corner); it also let free space for scientists to enter inside the OTC’s without stepping the plot. Temperature and relative humidity were recorded through data loggers in control plots and inside OTC’s

Sampling

The focus of the study were the arthropods associated to pasture for foraging production. Because OTC’s represent a physical barrier for flying insects, our focus was made on crawling arthropods. OTC’s were lift up about 5cm above the ground and allow any arthropod dislocations around the experimental area. Pitfall trap were then used for the sampling. Grasses inside each plot were seasonally and manually harvested to evaluate the biomass. Therefore, pitfall traps were set up and collected before harvesting grasses. Pitfall traps consisted in a 330 ml plastic cups, about 12 cm deep and 8 cm of diameter at the top (Picture 2). Traps were filled with ethylene glycol. We used car’s cooling liquid at 20% ethylene glycol at which we added few drops of soap to break the water tension. Specimen collected were then store into ethanol (96%). For each season (Winter and Summer), four pitfall traps were set up on each corner of each plot resulting in 4 traps per plot (Picture 3). All traps were set up for 14 days apart during the summer in the field B where the traps were set up for 13 days

Quality Control

After collection, specimens were store into alcohol (96%) before sorting. Specimens, adults and juveniles, were identified in a laboratory by trained parataxonomist (Sophie Wallon) and organized following a system of morphospecies. Final identification was done by Paulo A.V. Borges.

Method steps

1. Specimens were identified based on the Azorean arthropods collection “Dalberto Teixeira Pombo Insect Collection (DTP), University of Azores” created and maintain by Paulo A.V. Borges. A new collection reference was created, in the frame of the project PASTURCLIM, referencing each species occurring on the present dataset. If the specimen observed was not corresponding to any specimen already recorded in the Azorean arthropods collection or if identification was not possible, then the specimen was attributed to a new morphospecies number (identificationRemarks in Occurrence table)

The following classes and orders of arthropods are covered: Arachnida: Araneae, Opiliones, Pseudoscorpiones; Chilopoda: Lithobiomorpha, Scutigeromorpha; Diplopoda: Julida, Polydesmida; and Insecta: Coleoptera, Dermaptera, Hemiptera, Hymenoptera, Neuroptera, Orthoptera, Psocodea

1. Arthropoda
   common name: Arthropods rank: class

The study was conduct on the Archipelago of the Azores (North Atlantic), on Terceira island (38.712925, -27.234912) which is the third largest island of the archipelago with 400.2 km2 and a maximum altitude above sea level of 1021 m.