Effect of snowmelt time on growth and reproduction of Pedicularis davidii var. pentodon in the eastern Tibetan Plateau

Abstract

The growth and reproduction of Pedicularis davidii Franch. var. pentodon Tsoong, a snowbank species in the eastern Tibetan Plateau, was studied along a snowmelt gradient of four segments. Soil water content in the snow-free period and amplitude of diurnal soil surface temperature in March to May were significantly different between the segments, whereas soil nutrients and pH showed no difference. The species did not occur at the early-melting segment. Stem height, leaf number per stem, leaf size and specific leaf area increased significantly along the remaining segments. Above-ground biomass and total biomass showed a similar trend, while below-ground biomass and the ratio of below- to above-ground biomass decreased along the gradient. Flower number, seeds per flower and 1000-seed weight increased in the lower and middle parts of an inflorescence, while they kept almost constant in upper part of an inflorescence along the gradient. As far as a whole inflorescence was concerned, these reproductive characteristics increased from early- to late-melting segments of the snowbank. Population density also increased along the snowmelt gradient. The distribution and growth pattern were mainly related to diurnal freeze–thaw cycles near the soil surface and soil water content.

Keywords:

• Pedicularis davidii Franch. var.
• pentodon Tsoong
• freeze–thaw cycle
• snowmelt gradient
• biomass allocation
• soil water content

Acknowledgments

This study was supported by the National Natural Science Foundation of China (Nos. 40971178, 30870396), the Knowledge Innovation Program of the Chinese Academy of Sciences (Nos. KZCX2-YW-418, KZCX2-XB2-02), the National Sci & Tech Supporting Program during the 11th Five-Year Plan Period of China (No. 2009BA184B02).