Analyzing age trends in short-lived alpine shrub species—detrending revisited

Annual growth rings of woody plants provide valuable insights into past growing conditions and climate–growth relationships. Constructing ring-width chronologies typically involves the application of detrending methods to separate age- or size- related growth trends from environmental signals. While such methods are well established for trees, their applicability to short-lived shrubs remains uncertain, and inappropriate detrending may also pose the risk of distorting the results. We investigated age-related growth trends in four alpine shrub species from contrasting biomes and evaluated how to minimize potential biases. Using a regional curve standardization approach, we developed a flexible framework for detecting and visualizing age and size trends, and tested several common detrending methods to assess their effects on ring-width chronologies and subsequent climate–growth analyses. Our findings show highly specific growth processes, with little evidence for a pronounced age trend in two species, a contrastingly pronounced trend in one species, and a highly non-linear trend in another. Common detrending methods led to varied results, in some cases altering climate–growth relationships, particularly for species without a clear age-dependent trend. We therefore propose classifying series based on the structure of the dataset and prior species-level information, identifying and thoroughly evaluating age-related growth trends before choosing a detrending method. Moreover, our results highlight the importance of testing multiple detrending methods rather than relying on a single, ‘one fits all’, standardized approach.