Long-term Doñana monitoring by the Unique Scientific and Technical Infrastructure of Doñana Biological Reserve (ICTS-RBD) (ref.: 202030E286)

Ricardo Díaz-Delgado, Mizar Torrijo-Salesa, Luis Alfonso Ramírez González, Antonio Alcaide, David Antonio Paz Sánchez, David Aragonés, Diego López, Olga Ceballos, Isidro Román Maudo, Alejandria Rojas, Juan Tenorio, Katrin Schmidt, Jose Ruíz-Martín, Javier Bustamante, Rocío Marquez-Ferrando

Doñana LTSER (Long-Term Socio-Ecological Research) Platform. Doñana Protected Area. Doñana National Park. Doñana Biological Reserve (RBD).

The Doñana Long-Term Monitoring Programme has been carried out by ICTS-RBD (Unique Scientific and Technical Infrastructure of Doñana Biological Reserve) since 2004. Certain monitoring and survey activities have already started in the 1980s, focusing on birds and endangered species, such as the Iberian Lynx or the Imperial Eagle. The integrated programme started in 2003, when it was extended and funded to monitor biodiversity and ecological processes targeting species, habitats and populations, as well as ecosystem structure, function and services. Long-term data systematically collected provide a baseline for decision-making and the assessment of management actions in order to minimise the impact of global change and local drivers. Results and reports are annually published and provided to the Protected Area Managers and Practitioners and to the regional authorities through the CSIC open access repository.

National Parks Autonomous Agency (OAPN) between 2002–2007; Singular Scientific and Technical Infrastructures from the Spanish Science and Innovation Ministry (ICTS-MICINN); Ministry of Agriculture, Livestock, Fisheries and Sustainable Development from the Regional Government of Andalusia (CAGPDES-JA) since 2007; and Doñana Biological Station from the Spanish National Research Council (EBD-CSIC) provide in-kind and direct funding to maintain the programme. Finally, the project has also benefitted from the eLTER Plus INFRAIA Research Project (Horizon 2020 EU Programme, Agreement No. 871128), the eLTER H2020 INFRAIA project (Horizon 2020 EU Programme, Agreement No. 654359) and the SUMHAL Research Project funded by FEDER actions [SUMHAL, LIFEWATCH-2019-09-CSIC-13, POPE 2014-2020] from the Ministerio de Ciencia, Innovación y Universidades.

The study area is located inside Doñana Protected Area in southwest Spain, where permanent plots are spread across Doñana Biological Reserve (60 km²). The climate is Mediterranean sub-humid with Atlantic coast influence, resulting in wet mild winters and dry warm summers. The rainy season occurs between October and April, with a peak in December–January (average rainfall is about 550 mm). Doñana's four main ecosystems are monitored, including: temporary marshes, active sand dunes, Mediterranean shrublands and woodlands and Doñana's shoreline of 30 km length. Under the vegetation topic, shrubland plant communities are monitored in 21 permanent plots sampled once per year during the peak flowering season, between March and May.

The long-term monitoring of Doñana shrublands started in 2008 by setting 21 permanent plots across the Doñana Biological Reserve. Each plot is sampled during one sampling campaign per year along the flowering season (between March and May). A total of 21 permanent square plots (15 m x 15 m) were located according to stratified random sampling (Fig. 1). Stratification was based on the three main types of shrub communities found on the stabilised sand dunes according to water table depth in summer: xerophytic white shrub > 4 m; transitions shrub > 1 m and < 4 m; hygrophytic dark shrub < 1 m. Woody plant cover is measured using the line intercept method across three transects per plot of 15 m length, orientated from west to east and located at fixed points of 2.5, 7.5 and 12.5 metres on both sides of the plot. Using the line-intercept method, the contacts of each plant individual are recorded in a band strip of 50 cm along the measuring tape (Cummings and Smith 2000), together with the plant species, the class age, either adult (size class > 25 cm) or seedling (size class < 25 cm), the canopy status as a living or dead specimen and the average canopy height per transect, visually estimated (Fig. 2). According to the plant structure of the monitored woody plant communites, only one vertical stratum, the dominant and taller, is measured so that plants or seedlings in the understorey are disregarded, being those very infrequent. The method enables the calculation of the percentage cover for each species across every transect and for the whole plot (as the summatory of the three transects), including total data per species on class age and percentage of dry and green canopies, additionally to the percentage cover of bare soil, plant species density, species richness and plant species diversity. The maximum sampling time per plot was 75 minutes, being 40 minutes the average time, including stakes search and plot deployment. This permanent sampling is used as ground-truthing for further landscape monitoring using different remote sensing data sources (satellite, airborne and unmanned Aerial vehicle (UAV)), enabling the validation of shrubland mapping at larger scales (Jiménez and Díaz-Delgado 2015, Jiménez and Díaz-Delgado 2017). The yearly collected data on species occurrence and abundance in the monitored plots are used to train classifiers and produce maps of spatial distribution of main shrubland species in the Doñana Biological Reserve.

Figure 1.  

Geographic location of the 21 permanent plots (with their identification codes) monitored and available in the dataset. All plots are located inside the Doñana Biological Reserve, RBD (red polygon). Doñana protected area is located in the south-western part of the Iberian Peninsula.

Figure 2.  

Graphical scheme of the sampling procedure. a) Zenithal view of one monitoring plot with the different woody plant canopies and transects located inside the plot; b) zoom in the red square in figure a) showing the interceptions of every canopy with the measurement tape and the strip band considered for interceptions; c) field data collection with a digital device; d) resulting table of the example in b).

Taxonomic identification is assessed by different observers at the time in the field, using flowers and fruits to complement the correct identification. Plots are located with permanent stakes and coordinates collected with a D-GPS (ca. < 1 m horizontal accuracy). Although more than 10 observers have participated in the sampling, 80% of the sampling was led by the same observer. Data were digitally collected using mobile devices by means of a specifically designed Cybertracker sequence. This procedure guides the observer through a sequence of screens in a step-by-step way, some of them mandatory to prevent the loss of data. A map and a list of the plots, as well as a plant species list and observer names, are also available in the sequence for the observer. Unidentified plants in the field were later taxonomically identified. Contiguous individuals from the same species were recorded separately to improve plant density calculations. Data were transferred to a central Cybertracker database used for basic quality assessment, where the most frequent error (95%) corresponds to wrong tape measurements, which were corrected according to the previous record. Interannual plot percentage cover comparisons were also used to assess consistency in plant species occurrences and relative abundance, although the plant cover dynamics of these plant communities are highly variable.

Along each plot, there are three different transects of 15 metres, on which a measuring tape is extended. The three transects were distributed at fixed distances from the western side of the plot, the first one being 2.5 metres from the NE corner, the second one is 7.5 metres and the last one is 12.5 metres (Fig. 2). All the individuals intercepted by measuring tape were identified and the tape distance of the initial and final contact points was recorded in order to calculate the total cover in the transect per species. Ancillary data on age class (adult or seedling: plant height under 25 cm) and canopy status (green or dry), which means the vitality of a living or dead specimen, was also recorded for each individual. The average plant height was recorded for every transect. The percentage green and dead cover of each species was calculated per transect by adding up the measured interceptions per canopy as shown in Fig. 2d and finally provided in percentage of the total measured distance for all the three transects (45 m). Data were collected in the field using a CyberTracker-programmed sequence and downloaded as Excel or CSV-files.

The 21 shrubland permanent plots included in this long-term monitoring were set across the Doñana Biological Reserve (RBD) (red line in Fig. 1). These plots are included in the Doñana LTSER Platform, which contains the Doñana Protected Area.

36.983 and 37.031 Latitude; -6.548 and -6.463 Longitude.

For the whole monitoring period, technicians have identified 34 different species, eight generic identifications (i.e. genus) and a few individuals remain indeterminate. Taxa included three classes, 11 orders and 16 different families of terrestrial plants (Table 1). The most abundant families are Cistaceae, Lamiaceae, Fabaceae and Ericaceae, making up 93% of the total percentage cover (including all years and transects) (Table 1).

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