Analyzing relationships among water uptake patterns, rootlet biomass distribution and soil water content profile in a subalpine shrubland using water isotopes

Stable isotopic characteristics of plant water represent an integrated response of root systems to water sources with different isotopic signatures. Analysis of these signatures can help to identify many ecological processes involved in the uptake, transport and utilization of different water sources. In August 2003, we collected soil water samples throughout the soil profile from a subalpine shrub ecosystem in Wolong Nature Reserve, West China, along with stem water samples from the two dominant shrub species, Quercus aquifolioides and Salix luctuosa. Stable isotope contents of the different water samples were determined in conjunction with rootlet biomass distribution of each species and soil water content throughout the soil profile. Results indicated that these subalpine non-phreatophytic shrubs utilized soil water primarily from the top 30 cm of the soil profile. Water uptake patterns were significantly positively correlated with rootlet biomass distribution as well as the soil water content profile. Hence, the two shrubs could play an important role in keeping rainwater from entering river channels quickly, thereby reducing risk of flooding.

► Stem water of Q. aquifolioides and S. luctuosa came directly from the soil profile, with 75.4% and 73.1% of stem water originating from the top 30 cm of the soil profile in August 2003.
► Water uptake patterns of the two subalpine shrub species matched rootlet biomass distributions or soil water contents throughout the soil profile, but only that of S. luctuosa was consistent with both rootlet biomass distribution and soil water content throughout the soil profile.
► Alpine shrub communities could play an important role in keeping rainwater from entering river channels quickly, thereby reducing risk of flooding.