Browsing by Subject "N-FERTILIZATION"

Sort by: Order: Results:

Now showing items 1-2 of 2
  • Li, Junyu; Wu, Guoxi; Guo, Qingxue; Korpelainen, Helena; Li, Chunyang (2018)
    There are significant differences in the morphological and physiological responses of larch species with contrasting growth rates under fertilization. However, little is known about species-specific differences in responses to nutrient imbalance caused by fertilization. Therefore, in this study, the effects of nitrogen (N) and phosphorus (P) fertilization on the morphological, physiological and chloroplast ultrastructural traits of two contrasting larch species, fast-growing Larix kaempferi and slowly-growing L. olgensis, grown in larch plantation soil, were investigated during two growth seasons. It was shown that N and combined N and P (NP) fertilization increased plant photosynthesis, foliar N contents, chlorophyll contents, and dry mass accumulation and partitioning in aboveground organs in both larch species. Although P fertilization enhanced P accumulation, its presence reduced the N content in soluble proteins in the foliage of both larch species. Yet, P fertilization exhibited some differences in the two species: P fertilization increased photosynthesis, chlorophyll content and biomass accumulation of L. olgensis, while it decreased these parameters dramatically in L. kaempfert P fertilization increased foliar N content in L. olgensis, while it reduced it in L. kaempferi. P fertilized L. kaempferi had more damaged chloroplast ultrastructure than L. olgensis. In addition, L. kaempferi exhibited lower acid phosphatase activities, and higher photosynthesis and biomass accumulation than L. olgensis, except under P fertilization. L. kaempferi allocated more biomass into needles, except under P fertilization, while L. olgensis allocated more into stems under fertilization. In conclusion, it was shown that nutrient imbalance caused by P fertilization has greater negative effects on a fast-growing species than on a slowly-growing one, and the negative effects are related to differences in acclimation strategies, N partitioning to photosynthetic components, and P transportation and metabolism in the foliage.
  • Guo, Qingxue; Wu, Xiaoyi; Korpelainen, Helena; Li, Chunyang (2020)
    Plant-plant competition is a dynamic and complicated process that is strongly influenced by abiotic conditions. Drought is a critical threat to forests, particularly to young plantation forests. Temporal changes in competition combined with the effects of drought may dramatically influence the physiological traits of plants. Cunninghamia lanceolata plants exposed to intra-specific competition and no-competition conditions were investigated under two soil water levels (well-watered and drought). Changes in plant-plant competition relationships and nitrogen uptake rates were measured at different harvest times. The effects of drought and plant competition on physiological traits, for example, leaf nitrogen allocation, δ13C, and levels of abscisic acid (ABA), indole acetic acid (IAA) and jasmonic acid (JA), were also explored. Our results indicated that C. lanceolata shifted from intense neighbor competition to facilitation under well-watered conditions, whereas under drought neighbor competition became much stronger at the second harvest compared to the first harvest. Strong competition significantly decreased N uptake under drought. Leaf NH4+, NO3- and N allocation to water-soluble proteins increased under drought at the first harvest, but significantly declined under prolonged drought. Leaf, stem and root starch concentrations were enhanced by drought. However, during prolonged drought, the root starch concentrations, leaf δ13C, leaf ABA and starch content of C. lanceolata were much lower under strong neighbor competition than in no-competition conditions, which demonstrated that the combined effects of drought and strong competition were more harmful to plant growth and survival compared to single effects. Our study demonstrated that drought combined with competition strongly affected the N uptake, N allocation and physiological traits of plants. Intense competition imposed by neighbors is a great threat to the growth and survival of young C. lanceolata plantations under prolonged drought.