Browsing by Subject "BETULA-PENDULA ROTH"

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  • Mikola, Juha; Koikkalainen, Katariina; Rasehorn, Mira; Silfver, Tarja; Paaso, Ulla; Rousi, Matti (2021)
    Fast-growing and slow-growing plant species are suggested to show integrated economics spectrums and the tradeoffs of fast growth are predicted to emerge as susceptibility to herbivory and resource competition. We tested if these predictions also hold for fast-growing and slow-growing genotypes within a silver birch, Betula pendula population. We exposed cloned saplings of 17 genotypes with slow, medium or fast height growth to reduced insect herbivory, using an insecticide, and to increasing resource competition, using naturally varying field plot grass cover. We measured shoot and root growth, ectomycorrhizal (EM) fungal production using ergosterol analysis and soil N transfer to leaves using N-15-labelled pulse of NH4+. We found that fast-growing genotypes grew on average 78% faster, produced 56% and 16% more leaf mass and ergosterol, and showed 78% higher leaf N uptake than slow-growing genotypes. The insecticide decreased leaf damage by 83% and increased shoot growth, leaf growth and leaf N uptake by 38%, 52% and 76%, without differences between the responses of fast-growing and slow-growing genotypes, whereas root mass decreased with increasing grass cover. Shoot and leaf growth of fast-growing genotypes decreased and EM fungal production of slow-growing genotypes increased with increasing grass cover. Our results suggest that fast growth is genotypically associated with higher allocation to EM fungi, better soil N capture and greater leaf production, and that the tradeoff of fast growth is sensitivity to competition, but not to insect herbivory. EM fungi may have a dual role: to support growth of fast-growing genotypes under low grass competition and to maintain growth of slow-growing genotypes under intensifying competition.
  • Possen, Boy J. H. M.; Rousi, M.; Keski-Saari, Sarita; Silfver, Tarja; Kontunen-Soppela, S.; Oksanen, Elina; Mikola, Juha (2021)
    Strong seasonality in the subarctic causes unfavorable conditions for plant growth driving strong latitudinal clines in growth onset and cessation related to temperature and photoperiodic cues. Results from controlled experiments indeed show such clines, but results from field experiments seem to indicate that such clines may depend on site characteristics, suggesting that environmental variation, other than temperature and photoperiod, is relevant under climate change. Here, we increase our understanding of the effects of climate change on survival, height growth, and the phenological cycle by investigating their inter- and intrapopulation variation using three common gardens and six silver birch (Betula pendula) populations (each represented by up to five cloned genotypes) spanning the Finnish subarctic. We found clinal south-north variation among populations in survival and growth and in spring and autumn phenology to be largely absent. Sapling survival decreased with a transfer of over five degrees of latitude southward, but growth and phenology showed little evidence for adaptation to the local climate. Instead, ample genetic variation and plastic responses were found for all traits studied. Higher soil N availability increased sapling survival and growth, and phenology seemed to be adapted to soil N and day length rather than to temperature. Our results suggest that the climatic conditions predicted for the end of this century may, at least for poor soils, reduce the survival of northern silver birch trees in their early growth. However, those saplings that survive seem to have sufficient phenotypic plasticity to acclimatize to the changing climate. Along with climate, soil fertility plays a significant role and clearly warrants inclusion in the future tests of the effects of climate warming on tree growth and survival.
  • Sutela, Suvi; Niemi, Karoliina; Edesi, Jaanika; Laakso, Tapio; Saranpää, Pekka; Vuosku, Jaana; Makela, Riina; Tiimonen, Heidi; Chiang, Vincent L.; Koskimäki, Janne; Suorsa, Marja; Julkunen-Tiitto, Riitta; Haggman, Hely (2009)