Data from: Functional correlations between specific leaf area and specific root length along a regional environmental gradient in Inner Mongolia grasslands

Among above- and belowground traits, specific leaf area (SLA, cm2 g−1) and
specific root length (SRL, m g−1) are the two key traits reflecting
species resource acquisition strategies. However, patterns of variation in
SLA and SRL have rarely been examined simultaneously across evolutionary
history and environmental gradients, and the SLA-SRL relationship is still
controversial on several grounds. We examined the inter- and intraspecific
variations in SLA and SRL of different root branching orders and the
SLA-SRL relationship across 55 species and 21 plant communities of four
vegetation types along a 2,000-km transect in the Inner Mongolia
grassland. With increasing root branching order, the interspecific
variation in SRL increased but the intraspecific variation in SRL
decreased considerably, and the form of SLA-SRL relationship shifted from
positive to negative. This indicates that acquisition of soil resources
(e.g. water and nutrients) is a fundamental strategy for plant investment
to root length. When inter- and intraspecific variations in SLA and SRLs
were partitioned into alpha (within-community) and beta (among-community)
components, the alpha component exhibited substantially greater inter- and
intraspecific variations than the beta component. Across the transect, the
evolutionarily late diverged species in phylogenetic tree evolved toward
low SLA and SRL-1 (SRL for first-order roots) and tended to distribute in
resource-poor conditions along the environmental gradient. The early
diverged species, in contrast, had high SLA and SRL-1 and mostly
distributed in resource-rich conditions. Our findings suggest that
patterns of inter- and intraspecific variations in SLA and SRL of
different root branching orders and the form of SLA-SRL relationship could
be well explained by within- and among-community filtering processes and
species divergence time. Coordination and trade-offs between leaves and
roots do not mutually exclude but operate simultaneously at different
scales and among different root branching orders in arid and semiarid
grasslands.