Forest-to-Cropland Conversion Reshapes Microbial Hierarchical Interactions and Degrades Ecosystem Multifunctionality at a National Scale

Conversion from natural lands to cropland, primarily
driven by
agricultural expansion, could significantly alter soil microbiome
worldwide; however, influences of forest-to-cropland conversion on
microbial hierarchical interactions and ecosystem multifunctionality
have not been fully understood. Here, we examined the effects of forest-to-cropland
conversion on intratrophic and cross-trophic microbial interactions
and soil ecosystem multifunctionality and further disclosed their
underlying drivers at a national scale, using Illumina sequencing
combined with high-throughput quantitative PCR techniques. The forest-to-cropland
conversion significantly changed the structure of soil microbiome
(including prokaryotic, fungal, and protistan communities) while it
did not affect its alpha diversity. Both intrakingdom and interkingdom
microbial networks revealed that the intratrophic and cross-trophic
microbial interaction patterns generally tended to be more modular
to resist environmental disturbance introduced from forest-to-cropland
conversion, but this was insufficient for the cross-trophic interactions
to maintain stability; hence, the protistan predation behaviors were
still disturbed under such conversion. Moreover, key soil microbial
clusters were declined during the forest-to-cropland conversion mainly
because of the increased soil total phosphorus level, and this drove
a great degradation of the ecosystem multifunctionality (by 207%)
in cropland soils. Overall, these findings comprehensively implied
the negative effects of forest-to-cropland conversion on the agroecosystem,
from microbial hierarchical interactions to ecosystem multifunctionality.