Carbon allocation between storage and growth plays a significant role in determining how plants respond to changes in external environment. During photosynthesis, carbon dioxide is absorbed from the air and converted into non-structural carbohydrates (NSCs, including soluble sugars and starch), which can be used both as energy carriers and as building blocks for anabolic processes (i.e., growth, storage and reproduction). NSC therefore serves as the primary currency for carbon allocation when exposed to cold climates.

In order to reveal the NSC pattern and the sugar:starch ratio in response to elevation, the Forest Ecology Group of Wuhan Botanical Garden conducted a meta-analysis of NSC and sugar: starch ratio along 90 elevational gradients worldwide based on assembled 67 studies.

Results show that total NSC of aboveground organs including leaf, branch and stem increases significantly with elevation. Trees grown within warmer mountain ranges, which possess a greater respiratory metabolic rate, tend to store larger amounts of NSC in leaf in response to increasing elevation compared to tree located in colder mountain ranges. With tree species type considered as a moderator, the increase of NSC in leaves and stems only appears in treeline tree species, but not in non-treeline tree species. Despite considerable variation in NSC of different organs among regions, the sugar: starch ratio in mountain trees does not vary with elevation.

The study reveals a relatively stable sugar-starch partitioning pattern in mountain trees across the world, predominately modulates the balance of carbon assimilates between supply and demand. The findings are of great implication for understanding how trees respond to climate change in terms of carbon ecophysiology.

The results of this research have been published in Environmental and Experimental Botany entitled “Global patterns of mobile carbon partitioning in mountain trees in response to elevation”. This work was supported by the National Natural Science Foundation of China. (Version of Record 4 February 2023)

Results of the meta-analysis of log-response ratios (lnRR) for NSC concentrations (including soluble sugars, starch and total NSC) as well as sugar:starch ratio (Image by ZHOU Quan)