Fungal Perspective of Pine and Oak Colonization in Mediterranean Degraded Ecosystems

Metabolic niches in the rhizosphere microbiome: dependence on soil horizons, root traits and climate variables in forest ecosystems

Understanding belowground plant-microbial interactions is important for biodiversity maintenance, community assembly and ecosystem functioning of forest ecosystems. Consequently, a large number of studies were conducted on root and microbial interactions, especially in the context of precipitation and temperature gradients under global climate change scenarios. Forests ecosystems have high biodiversity of plants and associated microbes, and contribute to major primary productivity of terrestrial ecosystems. However, the impact of root metabolites/exudates and root traits on soil microbial functional groups along these climate gradients is poorly described in these forest ecosystems. The plant root system exhibits differentiated exudation profiles and considerable trait plasticity in terms of root morphological/phenotypic traits, which can cause shifts in microbial abundance and diversity. The root metabolites composed of primary and secondary metabolites and volatile organic compounds that have diverse roles in appealing to and preventing distinct microbial strains, thus benefit plant fitness and growth, and tolerance to abiotic stresses such as drought. Climatic factors significantly alter the quantity and quality of metabolites that forest trees secrete into the soil. Thus, the heterogeneities in the rhizosphere due to different climate drivers generate ecological niches for various microbial assemblages to foster beneficial rhizospheric interactions in the forest ecosystems. However, the root exudations and microbial diversity in forest trees vary across different soil layers due to alterations in root system architecture, soil moisture, temperature, and nutrient stoichiometry. Changes in root system architecture or traits, e.g. root tissue density (RTD), specific root length (SRL), and specific root area (SRA), impact the root exudation profile and amount released into the soil and thus influence the abundance and diversity of different functional guilds of microbes. Here, we review the current knowledge about root morphological and functional (root exudation) trait changes that affect microbial interactions along drought and temperature gradients. This review aims to clarify how forest trees adapt to challenging environments by leveraging their root traits to interact beneficially with microbes. Understanding these strategies is vital for comprehending plant adaptation under global climate change, with significant implications for future research in plant biodiversity conservation, particularly within forest ecosystems.

Into the void: ECM fungal communities involved in the succession from rockroses to oak stands

Oak forests accompanied by Cistus species are a common landscape in the Mediterranean basin. It is argued that Cistus dominated fields serve as recruitment areas for Quercus seedlings, as they help in the transmission of the fungal community through vegetative succession in these ecosystems. To test these assumptions, we analyzed the fungal community in terms of its richness and composition, taking into account the effects of host (Oaks vs. Cistus) and forest structure, mainly based on age. Edaphic variables related to the different structures were also analyzed to examine how they evolve through succession and relate to shifts in the fungal community. No differences in fungal richness were observed between old Cistus stands and younger Quercus, while a brief increase in ECM richness was observed. Community composition also showed a greater overlap between old Cistus and young Quercus stands. We suggest that the most important step in fungal transfer from one host to another is the shift from the oldest Cistus fields to the youngest Quercus stands, with the genera Amanita, Cortinarius, Lactarius, Inocybe, Russula, and Tomentella probably playing a major role. In summary, our work has also revealed the network of fungal community structure in the succession of Cistus to Oak stands, it would suggest that the fungi share niches and significantly enhance the ecological setting of the transition from Cistus to Oak stands.

Assessing the Importance of Native Mycorrhizal Fungi to Improve Tree Establishment after Wildfires

The Chilean matorral is a heavily threatened Mediterranean-type ecosystem due to human-related activities such as anthropogenic fires. Mycorrhizal fungi may be the key microorganisms to help plants cope with environmental stress and improve the restoration of degraded ecosystems. However, the application of mycorrhizal fungi in the restoration of the Chilean matorral is limited because of insufficient local information. Consequently, we assessed the effect of mycorrhizal inoculation on the survival and photosynthesis at set intervals for two years after a fire event in four native woody plant species, namely: Peumus boldus, Quillaja saponaria, Cryptocarya alba, and Kageneckia oblonga, all dominant species of the matorral. Additionally, we assessed the enzymatic activity of three enzymes and macronutrient in the soil in mycorrhizal and non-mycorrhizal plants. The results showed that mycorrhizal inoculation increased survival in all studied species after a fire and increased photosynthesis in all, but not in P. boldus. Additionally, the soil associated with mycorrhizal plants had higher enzymatic activity and macronutrient levels in all species except in Q. saponaria, in which there was no significant mycorrhization effect. The results suggest that mycorrhizal fungi could increase the fitness of plants used in restoration initiatives after severe disturbances such as fires and, consequently, should be considered for restoration programs of native species in threatened Mediterranean ecosystems.

Expansion of Naturally Regenerated Forest

Forests cover 31% of the global land area and are home to most of Earth’s terrestrial biodiversity [...]