Growth Of Birch Seedlings Research Articles

Effect of nitrogen deposition on growth of birch seedlings and ectomycorrhizal development with/without phosphorous treatments

Effect of nitrogen deposition on growth of birch seedlings and ectomycorrhizal development with/without phosphorous treatments

Varying impacts of cervid, hare and vole browsing on growth and survival of boreal tree seedlings

The negative impacts of mammalian herbivores on plants have been studied quite extensively, but typically with only a single herbivore species at a time. We conducted a novel comparison of the browsing effects of voles, hares and cervids upon the growth and survival of boreal tree seedlings. This was done by excluding varying assemblages of these key mammalian herbivores from silver birch, Scots pine and Norway spruce seedlings for 3 years. We hypothesised that the pooled impacts of the herbivores would be greater than that of any individual group, while the cervids would be the group with the strongest impact. Growth of birch seedlings advanced when cervids were excluded whereas growth of seedlings accessible to cervids was hindered. Survival of all seedlings was lowest when they were accessible to voles and voles plus hares, whereas cervids seemed not to influence seedling survival. Our results show that the impact of herbivores upon woody plants can be potent in the boreal forests, but the mechanism and strength of this link depends on the tree and herbivore species in question. Risk of abated stand regeneration appears highest for the deciduous birch, though there is need for seedling protection also in coniferous stands. The clear cervid-mediated growth limitation of birch also indicates potential for a trophic cascade effect by mammalian top predators, currently returning to boreal ecosystems.

Effects of light quality on growth and N accumulation in birch seedlings.

We studied the effects of light quality and nutrient supply on growth and nitrogen accumulation in silver birch (Betula pendula Roth) seedlings to test three hypotheses: (1) growth of birch seedlings is sensitive to changes in light quality; (2) the response of birch seedling growth to light quality depends on nutrient supply; and (3) assimilation and allocation of nitrogen by birch seedlings are affected by light quality. The two light regimes simulated the spectral quality of sunlight and shadelight, but did not differ in photosynthetic photon flux density, and the two nutrient supply regimes differed in the rate of supply, but not in the composition, of mineral nutrients. Accumulation and allocation of dry weight and nitrogen were strongly affected by nutrient supply regime, but light quality had little effect. During the first 15 days of the experiment, the largest effect of light quality was on height growth, which was greater in seedlings in simulated shadelight than in seedlings in simulated sunlight. Light quality had little effect on dry weight and nitrogen allocation to the stem during this period. However, at the end of the experiment (Day 29), there was an increase in N concentration per unit dry weight in leaves and stems of seedlings in the simulated shadelight plus high nutrient supply treatment.

The effect of Mn toxicity on growth of birch seedlings

The effect of Mn toxicity on growth of birch seedlings

Nutrition and growth of birch seedlings at varied relative phosphorus addition rates

Birch (Betula pendula Roth.) was investigated under steady state nutrition and growth at different relative addition rates of phosphorus (Rp). Phosphorus deficiency symptoms appeared on the leaves when the internal phosphorus concentration decreased, but disappeared again under steady state nutrition, independent of the stress level. The increased root/shoot ratio and the exploratory type of root systems developed during the adjustment stage remained under steady state conditions. At nonoptimum and close to optimum relative addition rates, independent of the rate, the phosphorus concentration of the culture solution did not exceed 2 μmol dm−3 and was generally < 1 μmol dm−3 immediately after phosphorus additions. The phosphorus concentration just before additions was generally < 0.5 μmol dm−3. The nutrition/growth relationships were similar to those for nitrogen, with relative growth rate (Rg) closely related to the Rp applied and with a strong linear relationship between internal phosphorus concentration and Rg. Regression was much steeper than that for nitrogen. The slope of the optimum nutrition was attained at a lower phosphorus weight proportion to nitrogen (8–10 P: 100 N) than previously estimated (= 13 P: 100 N), but a higher relative phosphorus requirement was observed under stress conditions. Birch seedlings had a strong tendency to consume phosphorus in excess of immediate requirements with a small effect on growth above optimum. This resulted in rapidly decreasing phosphorus productivity (Pp, growth rate per unit of phosphorus) with increasing internal phosphorus concentrations above optimum.

Effect of light quality, shading, and intermittent light on the growth of birch seedlings

Effect of light quality, shading, and intermittent light on the growth of birch seedlings