# Vegetation Productivity Losses Linked to Mediterranean Hot and Dry Events
###### Abstract  
Persistent hot and dry conditions play an important role in vegetation dynamics, being generally associated with reduced activity. In the Mediterranean region, ecosystems are adapted to such conditions. However, prolonged and intense heat and drought or the occurrence of compound hot and dry events may still have a negative impact on vegetation activity. This work aims to study how the productivity of Mediterranean vegetation is affected by hot and dry events, examining a set of severe episodes that occurred in three different regions ( Iberian Peninsula, Eastern Mediterranean and Western Europe) between 2001 and 2019. The analysis relies on remote sensing products, namely Gross Primary Production from MODIS to detect and monitor vegetative stress and LST from MODIS and SM from ESA CCI to evaluate the influence of temperature and soil water availability on stressed vegetation. Of all events, the 2005 episode in the Iberian Peninsula was the most significant, affecting large sectors of low tree cover areas and crops and leading to reductions of annual plant productivity in affected vegetation of ~47 TgC/year. The obtained results highlight the influence of land-atmosphere coupling on vegetation productivity and clarified the role of warm springs on vegetation activity and soil moisture that may amplify summer temperatures. The functional recovery of affected vegetation productivity after these episodes varied across events, ranging from months to years. This work highlights the influence of hot and dry events on vegetation productivity in the Mediterranean basin and the usefulness of remote-sensing products to assess the response of different land covers to such episodes. g 20  
From a hydrometeorological point of view, soil moisture and temperature anomalies control vegetation activity; directly through water limitation and indirectly by affecting the land-atmosphere coupling and atmospheric heating and drying, which further amplifies water stress conditions [19; 20; 21; 22; 23]. Previous studies, e.g., [23; 24; 25], pointed out how land-atmosphere feedbacks, with an emphasis on the soil moisture-evaportranspiration-temperature mechanism, play an important role in temperature extremes. The depletion of soil water content amplifies high temperatures due to the increase of sensible heat fluxes [26], which consequently leads to a reduction in the transpiration and photosynthetic activity of vegetation and thereby contributes to the enhance in warming due to the decrease of evaporative rates [27]. Soil moisture and temperature are expected to change under future climates [24] and strong temperature anomalies, in conjunction with the lack of precipitation during a long period, may induce high soil moisture deficits, consequently affecting vegetation activity [28]. Moreover, these events not only reduce the carbon take-up by plants but also highly increase the potential risk of large fires [29] or other disturbances [30]. The magnitude of a given hydrometeorological extreme event may not necessarily imply an extreme response from the ecosystem, as pointed out by [PERSON] et al. [31] and exemplified in other studies of the two major drought/heat events in Europe [6; 18; 20]. Vegetation response to a given extreme can also be lagged [32], which calls for an extended analysis of the spatio-temporal influence of extreme events on vegetation. Furthermore, land cover is thought to play an important role in buffering or amplifying the resulting impacts of extreme summer droughs [20; 33; 34]. This work aims to study how hot and dry events affect the European part of the Mediterranean's vegetation productivity by examining a set of severe episodes that occurred in three different regions (Iberian Peninsula, Eastern Mediterranean and Western Europe), between 2001 and 2019. Based on remote sensing data, we assess the persistence of vegetative stress conditions in order to quantify the changes in vegetation productivity and to identify the most affected land covers on each episode.