A metanalysis exploring the carbon- and the growth- limitation hypotheses for treeline formation in deciduous species

Using a meta-analysis of studies published between 1994 and 2023, we compared NSC, starch, and soluble sugars between treeline and below-treeline elevations and examined how responses varied among organs, plant functional types, and growing-season periods.

Overall, carbohydrate concentrations did not differ consistently between elevations, indicating no general support for either hypothesis. However, organ-specific patterns revealed that roots and stems tended to accumulate NSC and soluble sugars at treeline, consistent with growth limitation, whereas twigs showed reduced NSC during mid-season, consistent with carbon limitation. These results suggest that carbon limitation and growth limitation may operate simultaneously in deciduous treeline species, depending on organ and seasonal context.</p>