Consistent Poplar Clone Ranking Based on Leaf Phenology and Temperature Along a Latitudinal and Climatic Gradient in Northern Europe

Abstract

In Northern Europe, poplars (Populus) can provide biomass for energy and material use, but most available clones were developed for lower latitudes and are unlikely to be well adapted to higher latitudes, even under warmer climates. We thus need to understand how clones respond to climatic conditions and photoperiod, and how these responses can be predicted. We answer these questions exploiting leaf phenological data of Populus clones, grown in six sites across the Baltic region, in Northern Europe, for 2 years with contrasting climatic conditions. Regarding the effects of climatic conditions and photoperiod, within each site, higher temperatures advanced the timing and enhanced the speed of spring and autumn phenology, but reduced the effective growing season length. Across sites, latitude affected the timing of spring and autumn phenology, the speed of spring phenology, and the effective growing season length; clone affected only the timing of phenology. Regarding the predictability of clone response to growing conditions, the growing degree day (GDD) model could not predict spring phenology, because the growing degree day threshold for a specific phenological stage was not only clone-, but also latitude- and year-specific. Yet, this GDD threshold allowed a robust ranking of clones across sites and years, thus providing a tool to determine the relative differences across clones, independently of latitude and temperature. A similar, but not as strong, pattern was observed in the timing of spring and autumn phenological stages. Hence, while prediction of spring phenology remains elusive, the ranking of clones based on observations of their phenology in a single location can provide useful indications on the clones’ relative performance under different latitudes and climates.

European Carbon Uptake has Not Benefited From Vegetation Greening

“…On the seasonal time‐scale, European NEE from TRENDY in spring has a significant decreasing trend of 0.018 PgC yr −1 (Figure 2f), which may be related to the advance of the start of the growing season (Fu et al., 2014; Vico et al., 2021). This advanced spring phenology makes the trend of GPP (0.060 PgC yr −1 ) greater than that of TER (0.042 PgC yr −1 ), resulting in a net carbon increase.…”

Molecular Selection Tools in Adaptive Phenology of Populus trichocarpa Breeds for the Nordic-Baltic Region

“…Approximately 900 selected clones underwent testing for several years before planting 100 individuals in the long-term clone trial near Uppsala at 59°N. Since 2007, selected parts of this material have been tested in multiple locations in Sweden, Estonia, Latvia, Lithuania, and Poland [6,7,43,44]. Since 2013, 10 candidate clones for commercial deployment have been tested in pilot plantations.…”

Fertilization of poplar plantations with dried sludge : a demonstration trial in Hillebola - central Sweden

“…The poplar plantation is located in the coniferous-dominated landscape outside Hillebola, central Sweden (blocks 1 and 2 -60.351975 N, 17.690794 E; blocks 3 and 4 -60.349752 N, 17.667424 E). The area of set-aside arable land, approximately 25-30 hectares, was planted in 2016 with Populus trichocarpa clones adapted to northern European climate by breeding (Adler et al, 2023;Adler et al, 2021;Apuli et al, 2021;Karacic et al, 2021;Richards et al, 2020;Ronnberg-Wastljung et al, 2022;Vico et al, 2021). The parcel with blocks 1 and 2 was previously grown with food and fodder crops, while blocks 3 and 4 were established on grassland (Figure 2).…”