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Alpine ecosystems have a high ecological value, high biodiversity, and provide important ecosystem services. However, alpine communities are highly vulnerable to climate changes. Changes in biodiversity and its distribution will affect the goods and services that these ecosystems provide. Also, it can affect climate regulation by altering the exchanges of greenhouse gases (GHG) and the cycles of carbon (C) and nitrogen (N), in feedback processes. Due to their ecological importance and vulnerability, alpine meadows deserve special attention. In this regard, the main objective of the IBERALP project is the analysis of the interactions between components of biodiversity, mainly plant and soil microbial diversity, and their relationship with GHG fluxes; and how these interactions are affected by climate change. IBERALP is focused on the alpine communities of five Iberian mountain National Parks: Picos de Europa, Ordesa and Monte Perdido, Aigüestortes i Estany de Sant Maurici, Sierra Nevada, and Sierra de Guadarrama. In each National Park, we selected two different altitudes and two different alpine community types based on soil conditions (mesic and xeric). Here we study leaf physiological and fluorescence parameters assimilation, respiration, the quantum yield of photosystem II (PhiPSII), maximum quantum efficiency (Fv`/Fm`) and photochemical quenching (qP) in two representative plant species (a legume (Trifolium repens) and a grass (Nardus strita)) present in each National Park. In addition, we recorded altitude and humidity soil condition using a portable photosyntheic system (Li-cor 6800; Li-Cor Inc.) with an integrated fluorescence chamber head. Multiple factors affect the ability of plants to assimilate CO2 and photoprotect themselves from solar radiation excess, so there was no common pattern for all Parks. However, in general, plants at higher altitudes showed a greater photosynthetic and photoprotection capacity against high irradiances compare to those at lower altitudes. Similar behaviour was found in mesic versus xeric communities. Exceptions were found, such as, for example, in Picos de Europa National Park, where the intense fog and grazing (with continuous contribution of N to the soil) modified these patterns of photosynthesis and photoprotection. This work was supported by the OAPN through the project PN2021-2820s (IBERALP).

For the last decade there has been a continuous increase in atmospheric methane. Methane (CH4) is the second most important greenhouse gas (after carbon dioxide, CO2). However, despite the recent international effort to quantify global CH4 fluxes, such information is still limited, with a significant source of uncertainty (from 51% to 82%) mainly attributed to emissions from wetlands and other inland waters. On the other hand, some research in arid ecosystems (drylands) has shown that they play an important role in the CH4 cycle as CH4 sinks. These uncertainties in quantifying potential methane sinks highlight the need to increase our understanding of this effect of dryland ecosystems.In this study we have quantified the capacity of two Mediterranean ecosystems as methane sinks. A lowland site located at 200 m.a.s.l and 6 km from the coast, in Cabo de Gata Natural Park (Almería, Spain; N36°56′26.0″, W2°01′58.8). This lowland is dominated by Stipa tenacissima at 60 % cover. And a subalpine site located at 1,600 m.a.s.l. and 25 km from the coast, in Sierra de Gádor (Almería; 36º55′41.7″N; 2º45′ 1.7″W). This site is a shrubland plateau derived from an open forest and its climate is Mediterranean with hot summers. Both study sites are included in the international network FLUXNET (https://fluxnet.org/about/).For this purpose, two techniques have been used, the Eddy covariance technique to measure CH4 fluxes at the ecosystem scale and a standardized camera system composed by an infrared gas analyser (LI-7810, Li-Cor, Lincoln, NE, USA) connected to a Smart Chamber (8200-01S, Li-Cor, Lincoln, NE, USA), to measure soil CH4 fluxes in intensive campaigns. The Eddy covariance technique was applied for several weeks during the dry season, while the camera system was used to measure fluxes during the rainy season and in the middle of the growing season. Thanks to this study we will be able to establish an approximate range of CH4 assimilation by these ecosystems, comparing this value with those obtained in other studies; additionally, we will analyse the effect of the different soil conditions (humidity, temperature, porosity, texture...) on CH4 fluxes in these "drylands".This work was supported by the projects P20_00016 (BAGAMET) and LifeWatch-2019-10-UGR-01, co-funded by the MICINN through the FEDER funds.

Olive grove management entails environmental and socio-economic repercussions for the Mediterranean region. Maintaining bare soil in alleys is the most common management in this crop, but its implications for soil respiration (Rsoil) are not well understood. Although previous studies have quantified Rsoil at specific moments, soil respiration has not yet been continuously measured in olive groves. In this study a complete year of Rsoil measurements was taken in an irrigated olive grove in southeast of Spain. To avoid spontaneous weed growth a glyphosate-based herbicide was periodically applied. Six automated soil CO2 efflux chambers with additional sensors of soil temperature (T) and soil water content (SWC) were controled by a multichamber monitoring system (Li-8100A, Li-cor). With the aim of know the spatial variability in Rsoil and facilitate scaling up to estimate ecosystem soil respiration, 3 chambers were installed under the olive tree canopy and 3 chambers in the alleys.Preliminary results show that Rsoil increased in the warmer months and decreased in the colder months as expected. Also, daily Rsoil values under the trees are normally several times higher than in the alleys but this ratio changed with the seasons. In warm months, daily Rsoil under the tree was 2-3 times higher than daily Rsoil in the alley, while in cold months (like January) it was 6 times higher. In the alleys, diurnal variability was detected in Rsoil except in winter. While Rsoil under the trees was practically constant throughout the day during the year except in summer when there appears to be a relationship with the decrease in the flux of photosynthates in environments with high VPD. In spring Rsoil-alleys was double at midday versus night-time. Additionally, a positive and a negative relationship was established with temperature and SWC respectively. On the other hand, we found no clear relationship for Rsoil under the tree with respect to T or SWC. These preliminary results suggest a considerable Rsoil component of total ecosystem respiration influenced by the tree which does not depend on changes in T and SWC and that should be included in the partition models.

To study the effects of warming and declining species richness on the carbon balance of grassland communities, model ecosystems containing one, three or nine species were exposed to ambient and elevated (ambient +3°C) air temperature. In this paper, we analyze measured ecosystem CO2 fluxes to test whether ecosystem photosynthesis and respiration had acclimated to warming after 28 months of continuous heating, and whether the degree of acclimation depended on species richness. In order to test whether acclimation occurred, short term temperature response curves were established for all communities in both treatments. At similar temperatures, lower flux rates in the heated communities as compared to the unheated communities would indicate thermal acclimation. Because plant cover was significantly higher in the heated treatment, we normalized the data for plant cover. Subsequently, down-regulation of both photosynthesis and respiration was observed. Although CO2 fluxes were larger in communities with higher species richness, species richness did not affect the degree of acclimation to warming. These results imply that models need to take thermal acclimation into account to simulate photosynthesis and respiration in a warmer world., This research was funded by the Fund for Scientific Research – Flanders (Belgium) as project “effects of biodiversity loss and climate warming on carbon sequestration mechanisms in terrestrial ecosystems”, contract #G.0434.03N. H. J. De Boeck holds a grant from the Institute for the Promotion of Innovation by science and Technology in Flanders. P. Serrano-Ortiz benefits from a pre-doctoral grant from the Junta de Andalucía.