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

1-The Sierra Nevada Global-Change Observatory (https://obsnev.es/) is an ambitious project promoted by the Department of Sustainability, Environment and Blue Economy of the Regional Government of Andalusia with the scientific coordination of the University of Granada, in order to monitor the effects of global change in the Sierra Nevada protected area. For this purpose, the Sierra Nevada Global-Change Observatory has developed a monitoring programme and an information system for appropriate data management. 2-Smart EcoMountains (University of Granada-Sierra Nevada, Spain) is the Thematic Center on Mountain Ecosystems of the European Research Infrastructure LifeWatch-ERIC (https://smartecomountains.lifewatch.eu/). The main objective of the project is the long-term evaluation of mountain ecosystems' functions and services in the context of global change, using remote sensing, computing and new information and communication technologies advanced tools. The Smart EcoMountains project pursues three main objectives: 1) generate information on biodiversity, ecosystem services and global change in mountain ecosystems; 2) develop new technological tools and services that facilitate the exchange, localisation, access and analysis of data by scientists, in order to improve our knowledge of mountain ecosystems and the main global change processes affecting them; 3) develop tools to inform society about the most important global change processes affecting mountain biodiversity and ecosystem services, and support environmental managers and policymakers in science-based decision making. 3- Survival of an ectothermal organism requires that development and reproduction be synchronized with the appropriate periods of the annual cycle, and those inadequate with the phases of inactivity, but the sum of the times required for all phases of the life cycle cannot exceed one year in univoltine species. The problem we are going to unravel in this project is to understand if variation in the phenological strategy of the pine processionary moth (Thaumetopoea pityocampa) along an altitudinal gradient responds to an optimization of the pupation length, dragging as a consequence the rest of the cycle, or if on the contrary, it aims to diversify the possibility of avoiding predators and parasites, tracking a less optimal but broader period and playing with the climatic variety between years. Answering this question implies to understand what factors regulate the pupation length of the processionary and how non-climatic selective pressures (mainly predators and parasitoids) vary in each environment of the gradient. The study consists of three blocks: an observational one, designed to collect basic information about the species along the gradient; an experimental one, aimed at unravel what abiotic and, above all, biotic factors influence the phenology of the phase of the life cycle most difficult to observe, which is the pupa stage; and one of simulation, in which we will test our ability to predict the life cycle of the processionary, based on the observational and experimental data collected, through an ABM (Agent-Based Model). Although this project is primarily of basic research, its results will be important for the conservation and management of biodiversity in forest ecosystems. 4- The pine processionary moth (Thaumetopoea pityocampa, PPM) is a known defoliator alternating in its population dynamics periods at very low densities with periods of overpopulation, causing strong defoliation in the pine forests where it lives. The causes of this population dynamics have been attributed to abiotic (climate), biotic (predation, quantity and quality of food) factors, or both, with generally inconclusive results. The hypothesis that this project intends to explore is that PPM outbreaks are triggered by different causes in different places: although they share a development habitat (homogeneous pine forests) and a precondition in the biological features of the PPM (high reproductive investment, gregariousness), outbreaks start in "window of opportunity" in which group size and larval survival give each other positive feedback. To do this, we will take advantage of the different conditions that the PPM experiences along the altitude gradient of Sierra Nevada, in which previous data suggest that the "windows of opportunity" depend on climatic factors in the upper part of the gradient and biotic factors in the lower one. The study comprises of four blocks. First, we will use the Andalusian Government's database of PPM monitoring (1993-2019) to compare the characteristics of plots with highly contrasted PPM incidence histories. Second, we will quantify the predation rates in the successive life phases of the PPM by different types of predators (egg parasitoids, pupal parasitoids, birds and bats) in several plots that intensively monitored from 2015, distributed along the altitude gradient of the Sierra Nevada. Third, we will analyze, by means of experimental manipulations of the density of egg batch, the effect that the aggregation of egg batches has on the oviposition behavior of the moths, the predation rate and, later, the larval survival. Fourth, we will modify the bird density in a pine forest plot by placing nesting boxes, in order to determine if they are really able to control the PPM population. Although this project is eminently basic research, the results obtained will have significance for the conservation and management of biodiversity in forest ecosystems.

This work was conducted under the agreement “Convenio de colaboración entre la Consejería de Sostenibilidad, Medio Ambiente y Economía Azul de la Junta de Andalucía y la Universidad de Granada para el desarrollo de actividades vinculadas al Observatorio de Cambio Global de Sierra Nevada, en el marco de la Red de Observatorios de Cambio Global de Andalucía” and the project Smart EcoMountains “Thematic Center on Mountain Ecosystem & Remote sensing, Deep learning-AI e-Services University of Granada-Sierra Nevada” (LIFEWATCH-2019-10-UGR-4), which has been co-funded by the Ministry of Science and Innovation through the FEDER funds from the Spanish Pluriregional Operational Program 2014-2020 (POPE), LifeWatch-ERIC action line. The project has also been co-financed by the Provincial Council of Granada".