The influence of stand structure in submontane acidophilous oak forests on the presence of the wild service tree and sword-leaved helleborine

The objective of this work was to evaluate the occurrence of two strictly protected vascular plant species in managed stands of submontane acidophilous oak forests (Luzulo luzuloidis - Quercetum petraeae Hilitzer 1932 association) in the Sudeten foothills (Lower Silesia, Poland). During the study, the most important stand parameters influencing the occurrence of the wild service tree (Sorbus torminalis (L.) Crantz) and the orchid sword-leaved helleborine Cephalanthera longifolia (L.) Fritsch) were ascertained. The stands ranged from 50 to 130 years of age and were dominated by sessile oak (Quercus petraea (Matt.) Liebl.), which comprised 5-100% of trees. Both of the protected plant species were observed in 10% of the examined plots with the most favorable type of forest stand for sword-leaved helleborine as well as the wild service tree being clearly dominated by sessile oak (portion of oak above 80%). The analysis showed that the wild service tree was found in pure oak stands, whereas sword-leaved helleborine was also recorded in mixed stands aged 50-80 years. The increased frequency of sword-leaved helleborine was associated with a higher portion of oak in the tree layer. The results suggest that the modern silviculture practices, ‘close-to-nature’ silviculture, transform pure oak forest into mixed forest and allow for natural expansion of hornbeam (Carpinus betulus L.) as well as beech (Fagus sylvatica L.), which can induce the gradual disappearance of the orchid and the wild service tree in submontane acidophilous oak forests. Restoring semi-natural pure oak stands should play a significant role in supporting both protected species in submontane acidophilous oak forests of the Sudeten Region.

Arum-type of arbuscular mycorrhizae, dark septate endophytes and Olpidium spp. in fine roots of container-grown seedlings of Sorbus torminalis (Rosaceae)

The aim of this study was to determine the mycorrhizal status of nursery seedlings of the wild service tree (<em>Sorbus torminalis</em>), which belongs to the Rosaceae family. Its mycorrhizal associations are still fragmentarily known, and data from the few existing studies indicate that it forms ectomycorrhizal symbiosis (ECM). We analyzed the degree of mycorrhizal colonization of thirty 2-year-old container-grown <em>S. torminalis</em> nursery seedlings, which belonged to three single-tree progenies. The roots were dominated by arbuscular mycorrhizae (AM), with the morphology of the <em>Arum</em>-type containing arbuscules, vesicles and hyphae; however, no ECM structures were found. The degree of root colonization of the analyzed seedlings by AM fungi was 83.6% and did not differ significantly between the three single-tree progenies. In addition to AM, structures of dark septate endophytes (0.7%) and sporangia of <em>Olpidium</em> spp. (1.1%) were found in wild service tree roots. In agreement with previous studies, we confirmed arbuscular mycorrhizae for <em>S. torminalis</em>. Moreover, this is the first report that roots of this <em>Sorbus</em> species show the <em>Arum</em>-type morphology of AM and are associated with <em>Olpidium</em> species.

Growth-climate relationships at yew and wild service trees on the eastern edge of their range in Europe

<p><em>Aim of study</em>: The aim of the study was the construction of regional chronologies for South-Western Poland for yew (<em>Taxus baccata</em> L.) and wild service tree (<em>Sorbus torminalis</em> L.), two of the rarest native tree species on the edge of their range in Europe. The relationships growth-climate and incremental dynamics at both these species were investigated as well.</p><p><em>Area of study:</em> The eastern borders of the ranges of yew and wild service trees run across Poland. The majority of the yew occurrence sites are situated in South Poland, within the area of uplands and mountains, whereas the wild service tree grows in the western part of the country. The study plots (5 for yew trees, 4 for wild service trees) were located in nature reserves in SW Poland.</p><p><em>Material and Methods</em>: The research materials were cores from 200 trees (115 yew trees and 85 wild service trees). The annual growth widths were measured, then, local chronologies were constructed using classic methods of dating. Regional chronologies were based on yew trees with the Student’test t &gt; 6.0, and wild service trees with t &gt; 5.9. The chronologies were subjected to the indexation and used for dendroclimatological analyses: pointer years, correlation and response function.</p><p><em>Main results</em>: The yew chronology, spanning 219 years (1790-2008), was established on the basis of 51 samples, the average width of annual growths amounted to 0.61 mm. The wild service tree chronology, representing the period 1841-2013 (173 years), was produced from 37 samples, the average width of annual growth amounted to 0.60 mm (from 0.27 up to 0.58 mm). Dendroclimatological analyses of the yew indicated thermal conditions of the winter months and beginning of spring (straight correlations) as the predominating factor affecting the annual growth widths. Summer drought was an additional factor limiting growth. For the wild service trees cool and humid summer months in the growing season favour the formation of wide growths.</p><p><em>Research highlights</em>: On account of strong dispersion and limited small populations of these two tree species, there are few dendrochronological studies available. Therefore, every piece of information on the ecology of the yew and wild service tree allows us to broaden our knowledge of these rare species enriching the biodiversity of the native tree flora.</p><p><strong>Keywords:</strong> tree-ring width; <em>Taxus baccata</em> L.; <em>Sorbus torminalis</em> L.; dendroclimatology; Poland.</p>