Direct and indirect effects of global change on mycorrhizal associations of savanna plant communities

Abstract

Mycorrhizal fungi are key components of whole‐plant adaptive strategies to cope with different abiotic and biotic constraints. Although they are particularly sensitive to different global change drivers, there are still many gaps on the mechanisms underpinning shifts in mycorrhizal associations under different climatic and management scenarios. We carried out a field manipulative experiment of rainfall exclusion and increased temperature aimed to evaluate the impact of forecasted warming and drying on mycorrhizal associations of savanna plant communities subjected to different grazing history. Additionally, we compiled detailed information on the abiotic and biotic environment with the final aim of disentangling the direct and indirect effects of climate change on this widespread mycorrhizal symbiosis. Our results suggest that climate change could induce relevant changes in mycorrhizal associations, primarily promoted by warming, which decreased the abundance of mycorrhizae but induced higher activity of nutrient exchange between the host–plant and the mycosymbiont. Temperature did not only affect this symbiosis in a direct way, but also exerted relevant indirect effects via changes in soil functioning and other root‐colonizing microorganisms such as dark septate endophytes. Grazing history influenced the allocation of fungal structures inside the host‐root, but its effect differed as a function of the climatic treatment. Results from this study suggest that mycorrhizal fungi might become less prevalent in plant communities inhabiting savanna ecosystems under future scenarios of increasing aridity. In agreement with this finding, higher temperatures also promoted the predominance of plants with root traits that favour efficient resource acquisition by themselves without the help of a mycorrhizal partner. Our results provide new insights into the interactive effects of the two main threats facing Mediterranean savanna ecosystems, as well as potentially useful information to be applied in ecologically‐based management strategies aimed at attenuating the potential impact of global change on mycorrhizal fungi.

Effects of Climate Change on Soil Organic Matter C and H Isotope Composition in a Mediterranean Savannah (Dehesa): An Assessment Using Py-CSIA

“…Four permanent plots of 4 × 6 m were installed in each habitat type and fenced to exclude livestock access. In each habitat, four climate scenarios (treatments) were simulated: (1) control (C), without any manipulation; (2) warming (W), using methacrylate open top hexagonal chambers (0.65 m 2 ) to force an increase of 2–3 °C according to climate forecasting models (SRES A-2 model by the IPCC, 2022); (3) drought (D), using rainfall-exclusion shelters with six “V”-shaped methacrylate chanaletts (0.14 m wide; 20° inclination) intercepting 30% of the precipitation based on the same IPCC scenario; (4) a combined warming and drought (W+D) scenario, to assess the impact of both climatic stressors. , …”

Impact of climate change on pasture quality in Mediterranean dehesas subjected to different grazing histories

“…Their pH is acid, varying between 6.2 and 6.4 and its texture is loamy-sandy. For this study, three neighboring dehesas with similar characteristics in terms of vegetation, tree density, slope, orientation, and soil texture and depth were selected (more details in Pérez-Ramos et al 2021). Specifically, the distance across sites was 4.3 km.…”

“…Plant acclimation to drought is complex and depends on different factors, such as the species characteristics or the duration of water restriction (Farooq et al 2009). Drought alters plant associations with soil microorganisms, which are essential for nutrient uptake strategies (Pérez-Ramos et al 2021;Schimel et al 2007). Under moderate water stress, plant maturation can be delayed, thus nutrient values of pasture remain higher for a longer period (Coblentz et al 2000).…”

Importance of Dark Septate Endophytes in Agriculture in the Face of Climate Change

“…The detrimental effects of climate change have caused long and severe periods of drought [1] in which extensive farming in the Mediterranean region has become almost impossible, and, in the case of intensive farming, the water availability has been severely reduced. The interactions between microorganisms and plants have also been affected by droughts and soil warming, causing a decrease in the symbiotic relationships between both in various ecosystems [2,3]. The endophytic relationships of fungi with plants are being widely studied to elucidate their interactions with the hosts, the type of relationship they establish, and the potential effects of such interactions.…”