科研之友
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摘要
Question Do the three chosen species (Caltha palustris, Veratrum nigrum and Stellera chamaejasme) in humid alpine meadows take up water from different depths? Do these species differ in their responsiveness to rainfall? Location Mt. Balang, China. Methods Rainwater, soil water and plant water were collected from three plots over a 15-day period during JuneJuly 2006, and water isotopes analysed. The linear mixed models procedure was used to compare dD and d 18O values across soil depths, while three-factor ANOVA was performed to compare dD and d 18O values among the three species. The contributions of different soil depths to plant water sources were analysed using MixSir. A classic two-endmember linear mixed model was used to calculate the proportion of rainwater in plant stem water. Results Soil water showed substantial temporal shifts in isotopic profile from day to day, as influenced by rainwater input. The three plant species, C. palustris (CP), V. nigrum (VN) and S. chamaejasme (SC), acquired water from different soil depths, with their reliance on deeper soil water increasing in the order of CP < VN < SC. Moreover, CP, VN and SC absorbed 69.18%, 35.50% and 13.46% of their stem water, respectively, from the 4 July rainwater, suggesting that their responsiveness to rain pulses significantly differed in the order of CP > VN > SC. Conclusions The isotopic profiles of soil water shifted dramatically in response to rainfall, suggesting rapid movement of soil water. There was separation of the plant water uptake depths among the three species, with SC depending less on surface soil and being associated with drier soil habitats compared with CP and VN. Moreover, CP absorbed rainwater before it percolated below the root zone, while VN and SC did not; the differential responsiveness to water pulses may be related to their different water requirements as a result of adaptation to different soil water conditions. Our study demonstrates inter-specific differentiation in plant water uptake in humid alpine meadows. Such information is important for species co-existence and plant community composition.
