Abstract
Global warming has shifted climate zones poleward or upward. However, understanding
the responses and mechanism of microbial community structure and functions relevant
to natural climate zone succession is challenged by the high complexity of microbial
communities. Here, we examined soil microbial community in three broadleaved forests
located in the Wulu Mountain (WLM, temperate climate), Funiu Mountain (FNM, at the
border of temperate and subtropical climate zones), or Shennongjia Mountain (SNJ,
subtropical climate). Although plant species richness decreased with latitudes, the
microbial taxonomic a-diversity increased with latitudes, concomitant with increases
in soil total and available nitrogen and phosphorus contents. Phylogenetic NRI (Net
Relatedness Index) values increased from 0.718 in temperate zone (WLM) to 1.042
in subtropical zone (SNJ), showing a shift from over dispersion to clustering likely
caused by environmental filtering such as low pH and nutrients. Similarly, taxonomybased
association networks of subtropical forest samples were larger and tighter,
suggesting clustering. In contrast, functional a-diversity was similar among three forests,
but functional gene networks of the FNM forest significantly (P < 0.050) differed
from the others. A significant correlation (R D 0.616, P < 0.001) between taxonomic
and functional b-diversity was observed only in the FNM forest, suggesting low
functional redundancy at the border of climate zones. Using a strategy of space-fortime
substitution, we predict that poleward climate range shift will lead to decreased
microbial taxonomic a-diversities in broadleaved forest.
