Distinct taxonomic and phylogenetic patterns of plant communities on acid and limestone soils in subtropical and tropical China

Question: Understanding the mechanisms determining species composition is
one of the central goals in ecology. The limestone landscape of
southwestern China is one of the most widely-known landscapes developed on
carbonate bedrock in the world. We explored the following question: What
are the patterns of species composition and phylogenetic structures of the
communities developed on the acid and limestone soils? Location:
Southwestern China Methods: Using 536 plots on acid and limestone soils,
we identified distinct vegetation types on both soil types based on
hierarchical clustering and ordination. Variation partitioning partitioned
the effect of climate, geographic distance and soil on species
composition. Generalized linear models determined the effects of climate
and soil on phylogenetic diversities. Results: The typical vegetation on
acid soils is evergreen broad leaved forests indicated by Castanopsis
species, while typical vegetation on limestone soils is mixed evergreen
and deciduous forests indicated by a high proportion of deciduous trees
and calciphytes. Soil type was much more important in driving species
composition than climate and spatial distance. The standardized mean
pairwise phylogenetic distance (ses.MPD) and mean nearest taxon distance
(ses.MNTD) were significantly lower on limestone soils than on acid soils,
indicating a more clustered phylogenetic structure. The effect of soil on
ses.MPD was stronger than on ses.MNTD, and ses.MNTD increased with
increasing annual temperature and precipitation seasonality on acid soils
but decreased on limestone soils, suggesting that soil affected
phylogenetic structure at relatively deep branches, while climate combined
with soil mainly affects the relatively recent branches, as ses.MPD
measures phylogenetic structure at deep branches and ses.MNTD at shallow
branches. Conclusions: This study highlights the importance of soil in
shaping community structure at a regional scale, and it also reveals the
unique features of limestone vegetation and supports the validity of
limestone vegetation types in the Chinese vegetation classification
system.