Development of height growth and frost hardiness for one-year-old Norway spruce seedlings in greenhouse conditions in response to elevated temperature and atmospheric CO₂ concentration

Abstract

The mean temperature during the potential growing season (April–September) may increase by 1 °C by 2030, and by 4 °C, or even more, by 2100, accompanied by an increase in atmospheric CO concentrations of 536–807 ppm, compared to the current climate of 1981–2010, in which atmospheric CO is at about 350 ppm. This may affect both the growth and frost hardiness of boreal trees. In this work, we studied the responses of height and autumn frost hardiness development in 22 half-sib genotypes of one-year-old Norway spruce ( (L.) Karst.) seedlings to elevated temperatures and atmospheric CO concentration under greenhouse conditions. The three climate treatments used were: T+1 °C above ambient and ambient CO; T+4 °C above ambient and ambient CO; and T+4 °C above ambient and elevated CO (700 ppm). The height growth rate and final height were both higher under T+4 °C compared to T+1 °C. Temperature increase also delayed the onset, and shortened the duration, of autumn frost hardiness development. Elevated CO did not affect the development of height or frost hardiness, when compared to the results without CO elevation under the same temperature treatment. Higher temperatures resulted in greater variation in height and frost hardiness development among genotypes. Three genotypes with different genetic backgrounds showed superior height growth, regardless of climate treatment; however, none showed a superior development of autumn frost hardiness. In future studies, clonal or full-sib genetic material should be used to study the details of autumn frost hardiness development among different genotypes.22Picea abies222222