Seasonality and Activity of Arbuscular Mycorrhizal Fungi in the Rhizosphere of Endemic Tree Species

This study analyzed arbuscular mycorrhizal fungi (AMF) activity and soil chemical properties in Aspidosperma pyrifolium, Bauhinia ungulata, Caesalpinia pyramidalis, and Caesalpinia ferrea. AMF spores, root colonization, total glomalin-related soil protein (T-GRSP), easily extracted GRSP (EE-GRSP), and soil chemical properties were measured four times (July 2019, 2020 and December 2019, 2020). Significant differences were observed in AMF spores, root colonization, T-GRSP, and EE-GRSP among the plant species and across seasons. For soil chemical properties, we observed differences among plant species. During the dry season, B. ungulata and C. pyramidalis had the highest AMF spores and root colonization (57.3 ± 0.27 spores 50 g soil⁻¹ and 48.8 ± 1.05, respectively), whereas during the rainy season, C. pyramidalis and C. ferrea showed the highest AMF spores and root colonization (36.6 ± 0.13 spores 50 g soil⁻¹ and 62.2 ± 1.17, respectively). A. pyrifolium showed the highest T-GRSP in both seasons. On the basis of the soil chemical properties, we found that (i) A. pyrifolium, B. ungulata, and C. ferrea showed the highest soil organic carbon (1.32 ± 0.03 g kg⁻¹), phosphorus (7.01 ± 0.26 mg kg⁻¹), and soil pH (5.85 ± 0.23) and (ii) C. pyramidalis showed the highest Ca²⁺, Mg²⁺, Na⁺, H⁺ + Al³⁺, K⁺, and soil total nitrogen (1.36 ± 0.04, 0.73 ± 0.01, 3.72 ± 0.85, 4.56 ± 0.12 cmol_c kg⁻¹, 15.43 ± 1.53 mg kg⁻¹, and 0.16 ± 0.01 g kg⁻¹, respectively). Our results highlight the advantage of AMF spores as perennating structures over other AM fungal propagules in seasonal vegetation like Caatinga.