Abstract
Arbuscular mycorrhizal fungi (AMF) are determinant for the performance of plant communities and for the functionality of terrestrial ecosystems. In natural ecosystems, grazing can have a major impact on mycorrhizal fungi and consequently on plant growth. The objective of this study was to evaluate the statements referred above in Mediterranean arid areas in Tunisia. Root samples and rhizosphere soils of five dominant herbaceous plants were studied at six distinct arid sites differing on soil proprieties and grazing intensity. At each site, chemical and dynamic properties of the soil were characterized as well as the AMF colonization intensity and the soil functionality. Results showed that the mycorrhizal frequency and intensity and spore density, varied between plants in the same site and, for each plant, between sites and evidenced a positive effect of mycorrhized plants on soil microbial activity. Grazing and soil properties strongly affected AMF composition and the soil microbial and biochemical dynamics, which presented the lowest values at the sites with the highest grazing intensities. In conclusion, these results demonstrate that AMF improve soil biological properties, supporting the hypothesis that mycorrhiza and grazing compete for plant photosynthates, and highlight the importance of mycorrhizal symbiosis towards soil functionality under arid conditions.
Highlights
Arid and semi-arid regions of the world are considered as being vulnerable to climate change [1]
Several works emphasized the role of arbuscular mycorrhiza fungi (AMF) in sustaining plant cover in semi-arid and arid ecosystems [4,8,10] as is the case of the following Mediterranean conserved areas in Tunisia: Bou-Hedma National Park, Zarat protected area and Oued Dkouk Natural Reserve
AMF is of vital importance in the arid Tunisian ecosystem, where soils are generally poor in organic matter and nutrients
Summary
Arid and semi-arid regions of the world are considered as being vulnerable to climate change [1]. The arid and semi-arid regions of the world have been subjected to accelerated desertification due to increasing grazing intensity, decreased rainfall, higher temperatures and prolonged periods of drought [2,3]. Plants are well known for their symbioses with nitrogen fixing bacteria and arbuscular mycorrhiza fungi (AMF) These are just two examples of a vast range of symbiotic relationships that consist the plant microbiome and modulate plant phenotype and, plant fitness. In this context, the microbial community of the rhizosphere [5] is of great importance to plant performance, playing a crucial role in ecosystem functioning. Plants interact with guilds of these beneficial microorganisms living in their rhizosphere, promoting their growth and development [6]
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