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Although Northern red oak (Quercus rubra L.) is, in terms of surface area, the most important non-native deciduous tree species in Germany, only few studies were conducted on the genetic variation and origin of this introduced species, even at the European level. However, Northern red oak can, in groups or as single trees, contribute to a better stability and growth performance in mixed stands. The objective of this work is to give a review on existing studies that cover the origin and genetic variation of German resp. European red oak populations in comparison to populations from the natural range. It outlines relevant findings and provides a basis for future studies on this tree species. In the light of its economic relevance in North America, there are only few studies on the genetic variation of Q. rubra in its natural range. Until now, various studies had difficulties to identify particular postglacial migration routes due to the lack of geographic barriers and isolated glacial refugia. A possible consequence is the (in comparison to other oak species) lower genetic differentiation of northern red oak in its natural range which increases towards the north. In general, European red oak stands show sufficiently high genetic variation with at the same time only low genetic differentiation. Possible reasons may be, that multiple introductions and admixture of seeding material counteract genetic erosion in introduced populations. In one of the past studies, differences were found between historic German and historic French populations. It is suggested that differences in the import- and forest policies of the two countries may be the reason. The higher genetic variation in populations in the southwest of Germany indicates, that these stands may have been founded with material from the historic German populations (including populations in Alsace-Lorraine), while other German stands may have been founded with material of other sources. Until today, none of the reviewed studies was able to identify a particular region of origin of introduced red oak populations. However, all studies suggest, that introduced stands originate from the northern part of the natural distribution range. Furthermore, due to their sufficiently high genetic variation, the import of additional seeding material from the natural range is unnecessary in order to preserve the adaptive capacity of German red oak stands, at least under current climatic conditions. [ABSTRACT FROM AUTHOR]

For the main tree species (GÖTTLEIN et al., 2011) as well as for many less common tree species (GÖTTLEIN and ZEHLE, 2018) of Central Europe already nutritional threshold values have been derived on the basis of the extensive literature compilation of VAN DEN BURG (1985, 1990). The present publication provides such values also for the tree species Douglas fir, red oak and black locust, which were introduced in Central Europe in the 18th and 19th century. For these species nutritional threshold values for the range of normal nutrition could be calculated for all main nutrients as well as for the most important trace elements according to the method described by GÖTTLEIN et al. (2011). However, for red oak and black locust in most cases the data situation did not allow to calculate the threshold between latent and real deficit. To estimate the quality of the values given in tables 1 to 3 they were classified on the basis of their relative standard error. For Douglas fir, in the literature already several classification systems exist which, however, at least partly, were not developed independently of each other. Comparing the VAN DEN BURG-derived thresholds of the Tab. 1 with the median of all literature systems, with the exception of the lower limits of N and K, there is a very good consistency (Fig. 1). According to GÖTTLEIN (2016) from the thresholds of the range of normal nutrition a range of harmonious nutrient element ratios, as well as a narrower range of optimal ratios can be calculated. These values were also derived and are given in Tab. 4. [ABSTRACT FROM AUTHOR]

Urban foresters must be able to accurately assess costs associated with planting trees in the built environment, especially since resources to perform community forest management are limited. Red oak (Quercus rubra) and swamp white oak (Q. bicolor) (n = 48) that were produced using four different nursery production systems--balled and burlapped (BNB), bare root (BR), pot-in-pot container grown (PIP), and in-ground fabric (IGF)--were evaluated to determine costs of planting in the urban environment. Costs associated with digging holes, moving the trees to the holes, and planting the trees were combined to determine the mean cost per tree: BNB trees cost $11.01 to plant, on average, which was significantly greater than PIP ($6.52), IGF ($5.38), and B R ($ 4 .3 8 ) trees. Mean costs for BR trees were significantly lower than all other types of trees; IGF trees were less expensive to plant (by $1.14) than PIP trees, but this difference was not statistically significant (P = 0.058). Probabilities that cost per tree are less than specific values also are calculated. For example, the probabilities that IGF and BR can be planted for less than $8.00 per tree are 1.00. The probability that a PIP can be planted for less than $8.00 is 0.86, whereas the probability for a BNB tree is just 0.01. This study demonstrates th a t the cost of planting urban trees may be affected significantly in accordance with their respective nursery production method. [ABSTRACT FROM AUTHOR]