Abstract

Department of Plant and Environmental Sciences, UMB.

Contradictory results are reported on the best time to transplant trees from nurseries to urban areas and few studies are performed with Nordic tree species. Soil temperature fluctuates considerable during a growing season and the influence of soil temperature after transplanting is not well known.

The aim of this thesis was to study the effect of temperature, season, and phenology on transplant ability of some frequently planted street trees in the Nordic countries. Three different study methods were applied.

Method 1: Shoot and stem growth and leaf area was measured on five species: Acer platanoides L., Aesculus hippocastanum L., Prunus avium L., Sorbus aucuparia L. and Tilia x europaea L. ‘Pallida’ three years subsequent to transplanting in spring and autumn (both early and late in each season). Severe and moderate root pruning were performed in the transplanting process. Trees with larger root balls performed slightly better than trees with smaller root balls. Early autumn appeared least favorable for all the species, except S. aucuparia. Early spring transplanting was found favorable for A. platanoides and P. avium, but unfavorable for S. aucuparia. Shoot growth in all species, except S. aucuparia, was reduced by 38 to 86 % of control trees and leaf surface area by 13 to 61 % in the first season after transplanting. In A. platanoides and A. hippocastanum shoot growth was further reduced in the second season (71 and 81 % respectively). Shoot growth averaged the growth of non-transplanted controls the third season after transplanting in all species except for A. hippocastanum.

Method 2: Top and root growth related to soil temperature were measured in a rhizotron, consisting of twelve root study boxes. Betula pendula Roth. trees were transplanted early and late spring from the field into the rhizotron. Root extension rates in the middle of the growing season varied from 4 to 11 mm/day and correlated with soil temperature. Mean maximum length of new roots was 89 cm. This study revealed that first season growth in B. pendula trees transplanted late spring, with fully developed leaves, was not reduced compared to trees transplanted earlier in the spring (at bud break).

Method 3: The influence of root-zone temperature was tested on two ecotypes (northern: Rognan and southern: Stange) Betula pendula seedlings. Special equipment was developed for studies of plants in nutrient solution. Four stable root-zone temperatures (2, 6, 12, and 17 ºC) were applied to seedlings growing in a natural light phytotron and controlled environment chambers. Growth increased with temperature from 2 to 17 °C for seedlings adapted to growth in nutrient solution. The onset of growth was prevented at 2 and 6 °C both in ecodormant roots of cold stored plants and actively growing roots transplanted from solid root medium to hydroponic conditions. Bud break did not seem to be influenced by root temperatures. Samples of leaves and roots were analyzed for starch and soluble carbohydrates after eight weeks growth at 2 and 17 °C. The results show that production of photosynthetic products, respiration and incorporation of carbohydrates in cell structures were higher at 17 °C than 2 °C.

No transplanting time can be recommended on a general basis from these experiments. Results indicate that the cold soil temperature normally found in early spring and late autumn may restrict the growth of ecodormant roots or transplanted roots. However, transplanting field-grown trees in late autumn (mean soil temperature 6.6 °C) or early spring (mean soil temperature 3.6 °C) in the present study was not necessarily negative. Warmer soil temperatures promote growth and it appears that transplanting in late spring, after the first leaves are fully developed (mean soil temperature 10 °C), may be recommended for Betula pendula, and perhaps other deciduous trees if sufficient water is provided. Some authors consider early autumn transplanting (in full leaf) favorable for some species. This appeared to be the least favorable time in the present study (mean soil temperature 15 °C). However, a number of leaves wilted shortly after transplanting, and this most likely influenced the results in a negative way.


Key words: Acer platanoides, Aesculus hippocastanum, Betula pendula, carbohydrates, controlled environment, hydroponic, Prunus avium, rhizotron, root-zone temperature, soil temperature, Sorbus aucuparia, Tilia x europaea ‘Pallida’.




Oppdatert: 30.11.06
Utskriftsvennlig versjon : Arkiv : Tips en venn