Shifting patterns in fine root distribution of four xerophytic species
across soil structural gradients and years of growth
Abstract
1. Fine root distribution influences the potential for resource
acquisition in soil profiles, which defines how plants interact with
local soil environments; however, a deep understanding of how fine root
vertical distribution varies with soil structural variations and across
plant ages is lacking. 2. 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. 3. 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 supply 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. 4. 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.