Key message

A fixed sequence existed in the timing of critical stages between apical and radial growth. Radial growth was highly correlated with apical growth during the onset stage but not during the peak or cessation stages.

Abstract

The temporal relationships between the apical and radial growth of conifers may vary with species and site, and the varied responses of growth to climate change have rarely been revealed. We studied the temporal sequences and correlations between the apical and radial growth of Picea meyeri and the responses of the two growth types to the short-term climate of Luya Mountain, North-central China. The seasonal dynamics of aboveground growth at three sites were monitored, and the climate conditions of two growing seasons were contrasted. The results showed that (1) stem growth was initiated first, followed by needle and shoot growth; stem growth peaked and ceased last, followed by shoot growth and then needle growth, regardless of site or year. Stem growth was highly correlated with needle and shoot growth during the onset stage but not during the peak or cessation stages. (2) The three organs showed a similar earlier growth onset and peak in the warmer year (2017) than in the colder year (2016), although consistent earlier growth cessation was not observed, and growth increments were not significantly greater in the former than in the latter. Stem growth showed a longer duration, lower relative rate, and larger increment variability than shoot and needle growth, irrespective of site and year. These results suggested that (1) there was a consistent temporal sequence of the timing of critical growth periods between apical and radial growth (radial growth was not always linked to apical growth, at least during the peak and cessation growth periods) and (2) the three organs did not show consistent phenological responses to temperature during the growth cessation stage. Neither apical nor radial growth was enhanced by short-term warming; radial growth was probably more susceptible than apical growth to climate change.