Temperature and precipitation significantly influence the interactions between arbuscular mycorrhizal fungi and diazotrophs in karst ecosystems

Abstract

Arbuscular mycorrhizal fungi (AMF) and diazotrophs have the potential for nutrient transfer and biological nitrogen fixation in ecosystems, respectively. However, their response to vegetation restoration remains unclear, especially under varying temperature and precipitation levels in karst ecosystems. This study aimed to understand the effects of three climatic levels within four natural and managed vegetation restoration types on the diversity and community composition of AMF and diazotrophs. The interactive effects of temperature, precipitation, and vegetation types affected AMF diversity, while diazotroph diversity was not affected. Under conditions of natural vegetation restoration, there was an increase in AMF diversity in response to increasing temperature and precipitation. AMF richness was higher in shrubland and mature forest than in cropland when temperatures were over 20 ℃ and precipitation was high. Thus, in terms of diversity, AMF were more responsive to changes in climatic conditions and vegetation recovery than diazotrophs. Both AMF and diazotroph community compositions were affected by temperature and vegetation type. The relative abundances of AMF groups (e.g., Gigaspora, Glomus, and Septoglomus) and diazotroph taxa (e.g., Frankia) increased at temperatures above 18 ℃. The relative abundances of the AMF genus Glomus and the diazotroph genus Bradyrhizobium in shrubland and mature forest were higher than those in cropland, while abundances of the AMF genus Septoglomus and diazotroph genus Anabaena increased in cropland. Network complexity increased with increasing temperature and precipitation between AMF and diazotroph taxa. Glomus and Bradyrhizobium showed the most links with other groups, confirming that the dominant genera perform well in the co-occurrence network. These results suggested high hydrothermal regions resist rapid nutrient decomposition by strengthening the interactions between AMF and diazotrophs, especially between the abundant groups Glomus and Bradyrhizobium. Management to increase AMF and diazotroph abundance during vegetation recovery in high climate level may stimulate nutrient absorption and transport.