Spatio-temporal patterns of fine root distribution in four xerophytic
species shifted by soil rock fragment contents
Abstract
Temporal and spatial distribution of fine root influences the potential
for resource acquisition in soil profiles, which defines how plants
interact with local soil environments; however, a deep understanding of
how vertical fine root distribution and their temporal dynamics varies
with soil structural variations is lacking. We subjected four xerophytic
species native to an arid valley of China, Artemisia vestita, Bauhinia
brachycarpa, Sophora davidii, and Cotinus szechuanensis, to increasing
rock fragment content (RFC) treatments (0%, 25%, 50%, and 75%, v
v-1) in an arid environment and measured fine root vertical profiles
over four years of growth. Fine root depth and biomass of woody species
increased with increasing RFC, but the extent of increase declined with
plant age. Increasing RFC also increased the degree of interannual
decreases in fine-root diameter. The limited supplies of soil resources
in coarse soils explained the increases in rooting depth and variations
in the pattern of fine root profiles across RFC. Fine root depth and
biomass of the subshrub species (A. vestita) in soil profiles decreased
with the increase in RFC and plant age, showing an opposite pattern from
the other three woody species. Within species, the annual increase in
fine root biomass varied with RFC, which led to large interannual
differences in the patterns of fine root profiles. Capacity of younger
or subshrub plants to cope with soil environmental changes were greater
than the older or shrub plants. These results provide insights into the
limitations of soil resources in dry and rocky environments, and have
management implications for degraded agroforest ecosystem.