Adaptation of biomass allocation patterns of wild Fritillaria unibracteata to alpine environ-ment in the eastern Qinghai-Xizang Plateau

Abstract

Aims Under different selection stresses, alpine plants tend to adjust their biomass investments to different functions and/or organs, and this biomass allocation strategy presents different patterns during different life history stages of plants. Our objective is to address three hypotheses regarding Fritillaria unibracteata: 1) elevation gradients impact individual bulb biomass and individual total biomass; 2) biomass allocation adapts to the elevational change of environmental factors; and 3) biomass allocation at different life history stages show different patterns. Methods We collected wild F. unibracteata at different elevations in the alpine belt of Songpan County in the eastern Tibetan Plateau. The samples were cleaned and divided into different organs, the biomasses of which were then weighed after being dried in the oven. Important finding Elevation significantly affected individual bulb biomass (IBB) and individual total biomass (ITB), both of which decreased gradually with increased elevation. Elevation representing the heat factor was the pivotal factor limiting the growth of alpine plants such as F. unibracteata. For plants with different life history stages, their biomass allocation presented diverse patterns. First, the bulb biomass allocation (BBA) of 2-year-old F. unibracteata significantly decreased with increased elevation, but its leaf biomass allocation (LBA) increased. Second, both BBA and LBA of 3-and 4-year-old F. unibracteata were relatively stable at different elevations, but their stem biomass allocation (SBA) significantly decreased with increased elevation. In contrast, the sexual reproductive (flower) allocation (SRA) significantly increased with increased elevation. Third, at different life history stages, the root biomass allocation (RBA) of F. unibracteata was relatively stable at different elevations. Both RBA and SBA showed an increasing trend with the growth of plants, but BBA and LBA showed a decreasing trend.Three-year-old individuals normally had the maximum IBB.