Divergent response of shrub growth to climate warming along a latitude gradient

Understanding the response of shrub growth to climate changes is crucial to accurately predict the dynamic changes of the boreal forest ecosystem. A shrub-ring network base on 12 sites was established to explore the response of Pinus pumila growth to climate change along a latitudinal gradient from 44.10° to 52.58° N in northeastern China. The results showed significant differences in the growth trend of P. pumila at different latitudes in recent decades. Shrub growth was faster from 1950 to 1980 in the south and central. From 1981 to 2014, P. pumila growth increased in the north while slowed in the south and the central regions. The temperature of the previous winter and current spring were the main limiting factors for the growth of P. pumila in the north and south. In the central and southern, shrub growth was negatively correlated with precipitation in the previous and current summer. With the increase of latitude, summer temperature inhibits P. pumila growth, while summer precipitation positively impacts from 1981 to 2014. At the individual level, it can be better verified that the growth of P. pumila is promoted by both water and temperature. The prediction of the model shows that the radial growth trend of the northern shrub is decreasing under warming. Unexpectedly, P. pumila growth in the south will benefit from warming under the RCP4.5, RCP6.0, and RCP8.5 scenarios. Therefore, shrubs might not expand northward in the future under the background of climate warming.