Abstract
Understanding carbon allocation in plants is essential for explaining their growth strategies during environmental adaptation. However, the role of mobile carbon in plant growth and its response to habitat conditions is still disputed. In degraded meadow (alpine sandy grassland) and non-degraded meadow (typical alpine meadow and swamp meadow) on the Qinghai–Tibetan Plateau, we measured the monthly averages of above-ground biomass (AGB) and below-ground biomass (BGB) of the investigated species in each meadow and the average concentration of non-structural carbohydrates (NSCs), an indicator of carbon storage. Below-ground organs had higher concentrations and showed more seasonal variation in NSCs than above-ground organs. BGB had a positive correlation with below-ground NSCs levels. However, AGB had no clear relationship with above-ground NSCs levels. Plants in sandy grasslands had higher total NSC, soluble sugars, fructose, and sucrose concentrations and lower starch concentrations in below-ground organs than plants in alpine or swamp meadows. Overall, NSCs storage, particularly soluble sugars, is a major process underlying the pattern of below-ground growth, but not above-ground growth, in the meadow ecosystem of the Qinghai–Tibetan Plateau, and degraded meadow strengthens this process. These results suggest that the extent of carbon storage in non-photosynthetic organs of alpine herbs impacts their growth and habitat adaptation.
Highlights
To test the above assumption, we examined the relationship between nonstructural carbohydrates (NSCs) concentration and biomass and evaluated the role of carbon storage in impacting above- and below-ground growth and its response to the three meadows
Sandy grassland had the highest above-ground biomass (AGB) and below-ground biomass (BGB) in all meadows from June to September; biomass accumulation increased in degraded grassland
A significant interaction between season and organ was found for total NSC (p < 0.05) but not for other NSCs components (p > 0.05) (Table 4). These results indicate that the change in total NSC storage primarily relies on the levels of soluble sugar and starch, which change in response to variation in the meadow type and season, respectively
Summary
Plants with limited exposure to light have a higher proportion of aboveground biomass to optimize growth and survival [2], whereas they have larger belowground root systems for better access to soil water/nutrition under conditions of reduced nutrient and/or water supply [3,5]. These observed ecological strategies are well explained by the functional equilibrium hypothesis, which emphasizes that plant strategies are optimized for resource capture when resources are limited [6]. There is a lack of knowledge on how biomass allocation is regulated to cope with habitat changes
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