Long-term record of defoliation intensity in monitoring plots of pine woodland by the pine processionary moth (Thaumetopoea pityocampa)

Study Extent

Data recording began in 1998 for a short number of trees in Sierra Nevada, then in 2015 the number of plots was increased and kept until present. The plots were selected in all types of pine woodlands in the southeast of the Iberian Peninsula. A 500 m long itinerary is established on each plot. Each plot is geolocated with the coordinates and altitude of the midpoint of the itinerary, unless the itinerary is curved, in which case the approximate midpoint of the sampling area is indicated. Twelve trees per plot were individually labelled and georeferenced. In mixed stands, the species of labelled pines is the dominant one. When a tree dies, it is replaced by a close neighbour of similar size and shape. From 1998 till 2014, a set of 80 Pinus sylvestris were monitored for Pine Processionary Moth defoliation in an area of Sierra Nevada. From 2015, 27 pine woodlands were selected along the Granada province, including those labelled in 1998. Later, 11 additional plots were selected in 2019.

Sampling

Pines were visited every winter, and percentage of defoliation, estimated by eye from two perpendicular sides, was recorded. From 2014, also number of Pine Processionary Moth winter tents was recorded. Data were registered at the end of the period of caterpillar activity, February-April depending on the plot altitude and winter climatic conditions. The height of the pines was estimated by eye in 1998, when initially labelled. After that, in 2021 all trees were revisited, georeferenced, its height measured by a clinometre, DBH measured with a measuring tape, and some additional data on the shape of the canopy were also recorded.

Quality Control

1. The observer periodically trains its skills in defoliation estimations, whenever possible some helpers take part during data recording, to test the skill capacity of the observer. 2. Records are stored in an Excel datasheet which is daily updated during the censusing period. 3. Once per year, data are updated to the main database. 4. Storage: data is stored in Linaria (https://linaria.obsnev.es/), the institutional data repository of the Sierra Nevada Global-Change Observatory. Linaria is a normalised database focused on ecology and biodiversity related-data and it is developed in a PostgreSQL/PostGIS relational database management system (RDBMS). 5. Taxonomic validation: scientific names were reviewed by experts and were checked with the GBIF backbone taxonomy using the species matching tool (https://www.gbif.org/tools/species-lookup). 6. Standardisation: the standardisation to Darwin Core was done according to the practices recommended by the TDWG guidelines (https://dwc.tdwg.org/terms/).

Method steps

1. 1. Field sampling (see Sampling Description section). 2. Data is stored in Linaria (https://linaria.obsnev.es/), the institutional data repository of the Sierra Nevada Global-Change Observatory. 3. The dataset was standardised to the Darwin Core structure as occurrence data. It contains, specifically: 4,851 occurrences, and 35,474 records of associated measurements of 9 variables: “Percentage of defoliation caused by pine processionary moth”, "Number of pine processionary moth nests for that winter", "Height of the pine tree", "Diametre at breast height", "Tree top diametre", "Tree top shape", "Height of the unbranched part of the trunk of the tree measured from the ground to the first branches", "Number of neighbouring trees within a radius of 5 metres", "Year of the death of the tree". The Darwin Core elements included in the Occurrence Core are: occurrenceID, eventID, catalogNumber, collectionCode, datasetName, institutionCode, ownerInstitutionCode, modified, language, license, eventDate, year, basisOfRecord, recordedBy, recordedByID, individualCount, scientificName, taxonRank, kingdom, phylum, class, order, family, genus, specificEpithet, scientificNameAuthorship, continent, country, countryCode, locality, minimumElevationInMeters, maximumElevationInMeters, samplingProtocol, decimalLatitude, decimalLongitude, geodeticDatum, coordinateUncertaintyInMeters, habitat. For the Measurement or Fact Extension file, the Darwin Core elements included are: measurementID, occurrenceID, measurementType, measurementValue, measurementUnit, measurementMethod, measurementdetermineddate. 4. The resulting dataset was published through the Integrated Publishing Toolkit of the Spanish node of the Global Biodiversity Information Facility (GBIF) (http://ipt.gbif.es).

The dataset is centred on population size and defoliation intensity by the pine processionary moth (Thaumetopoea pityocampa, Notodontidae, Lepidoptera). Sampling units are individually labelled pines, belonging to seven different tree species: Pinus pinea, Pinus halepensis, Pinus pinaster, Pinus nigra, Pinus sylvestris, Pinus uncinata and Pinus canariensis.

1. Pinaceae
   rank: family

All the plots are located in the southeast of the Iberian Peninsula, mostly in the Granada province. There are some preselected plots in the province of Almería, but most of them have no data recorded so far. The plots were chosen trying to cover as much as possible the diversity of pine woodlands in which the pine processionary moth is present. The altitudinal range covers from sea level to 2500 m altitude, from coastal areas to high mountains and inland depressions, and pine forests can be natural, spontaneous regeneration, or the result of plantations.