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EN
Climate-growth relationships in Quercus robur chronologies for vessel lumen area (VLA) from two oak stands (QURO-1 and QURO-2) showed a consistent temperature signal: VLA is highly correlated with mean April temperature and the temperature at the end of the previous growing season. QURO-1 showed significant negative correlations with winter sums of precipitation. Selected climate variables were used as predictors of VLA in a comparison of various linear and nonlinear machine learning methods: Artificial Neural Networks (ANN), Multiple Linear Regression (MLR), Model Trees (MT), Bagging of Model Trees (BMT) and Random Forests of Regression Trees (RF). ANN outperformed all the other regression algorithms at both sites. Good performance also characterised RF and BMT, while MLR, and especially MT, displayed weaker performance. Based on our results, advanced machine learning algorithms should be seriously considered in future climate reconstructions.
PL
Celem pracy było określenie wpływu siedliska leśnego na zróżnicowanie jakościowe substancji humusowych w poziomach próchnic nadkładowych gleb leśnych tworzących się w pobliżu starodrzewu Quercus robur (200 – 600 lat). Analizowane gleby były zlokalizowane na terenie obszaru chronionego krajobrazu – w Borach Niemodlińskich i Lasach Stobrawsko-Turawskich. Badane gleby reprezentowały 15 profili zaliczanych do bielic, gleb brunatnych właściwych i kwaśnych. Specyfika i troficzność siedliska leśnego wpłynęły na ukształtowanie właściwości fizykochemicznych i chemicznych analizowanych gleb leśnych, co wyrażało się przede wszystkim w ich kwaśnym odczynie, zróżnicowanym zasoleniu jak i właściwościach optycznych substancji humusowych. Jednocześnie stwierdzono ilościowe zróżnicowanie materii organicznej w analizowanych poziomach gleb wyrażone wartością współczynnika zmienności (V) równą 61%. Uzyskane wyniki analiz chemicznych i wartości indeksów A2/4, A2/6, A4/6, ΔlogK oraz współczynników korelacji wskazują, iż w badanych glebach procesy transformacji materii organicznej prowadzą do wytworzenia substancji humusowych o niskim stopniu humifikacji i ilościowym zróżnicowaniu w profilach. Zmienność analizowanych właściwości charakteryzujących jakość substancji humusowych wskazuje, iż transformacja materii organicznej poziomów ektohumusowych zależy w dużym stopniu od jakości siedliska, w tym od rodzaju dopływającej materii organicznej.
EN
The aim of this work was to determine the diversity of qualitative humic substances in the ectohumus horizon of the forest soil profiles. The analyzed soils were located in protected landscape areas and nature parks – Bory Niemodlińskie and Lasy Stobrawsko-Turawskie, and occurred under the tree stands of trees which were 200 – 600 years old – Quercus robur. The analyzed soils represent 15 soil profiles belonging to Podzols, Cambisols and Dystric Cambisols. Properties of forest habitat specificity influenced the physicochemical and chemical properties of the analyzed soils. We observed particularly strong expressions of acidity, pH and salinity, and a diversity of chemical and optical properties of humic substances. The content of organic matter in the analyzed soil horizons showed considerable variation, as indicated by a coefficient of variation (V) equal to 61%. The composition of humic substances of forest litter is characterized by a gradual change of functional groups that usually consists in the decrease of carbohydrates, the relative increase of carboxyl and alkyl carbon, and decay of lignin. In the investigated soils, we observed that the transformation processes of organic matter led to humic substances which were predominantly humus with a lower level of humification, as evidenced by the indexes: A2/4, A2/6, A4/6, ΔlogK. Therefore, variation of the observed properties of humic substances indicates a different direction in the transformation process of organic matter. Such a transformation depends very much on the habitat and nature of supplied organic matter.
EN
Hybridisation and introgression are expected to be common in plant populations composed of various species of the same genera. These processes, however, frequently have one direction or are asymmetric, when one of hybridising species is a donor and other recipient of pollen. The asymmetric hybridisation may be also an important manner of migration by pollen. According to the theory of asymmetric hybridisation in mixed oak populations of European white oaks (Quercus robur and Q. petraea) the number of hybrid saplings should be higher under a canopy of Q. robur than under Q. petraea trees. The aim of this study was to determine, which of the two species in the mixed populations has a greater degree of success in regeneration and colonization, measured by the proportion and density of saplings and young individuals higher than 0.3 m. The taxonomic composition of saplings under the crown ranges of trees was analyzed on the basis of morphological characters of leaves in two distantly located mixed oak stands in Poland, in Jamy and Legnica Forests, where young generation to about 17-18 years old was observed under canopy of 125-140 years old mother trees. The first population is located about 100 km of Q. petraea geographic range and covers area of 6 km, the second about 500 km of Q. petraea range and covers more than 10 hectares. The density of 60 and 134 adult trees per hectare, were found in analysed populations, respectively. A significantly higher proportions of Q. petraea than Q. robur saplings were found in both compared stands. A hybrid saplings proportion were higher than hybrid adult trees. The hybrid saplings were observed more frequently under canopy of Q. robur only in the stand closer to the range of Q. petrea. Gene flow from Q. petraea to Q. robur by cross-pollination was found to be likely. The number of hybrid saplings found under crown projections of Q. petraea trees in both populations suggested also reverse gene flow, at least in the stand located close to the north-eastern limit of the Q. petraea range. A higher regeneration success of Q. petraea was observed in both stands suggesting expansion of this species.
EN
The occurrence of Osmoderma eremita (Scopoli, 1763), an endangered species restricted to hollow trees, was studied in a network or rural avenues in northern Poland. We detected1002 trees with hollows suitable for hermit beetle development (25% of all trees). Among them, 114 (11%) were occupied by O. eremita. The distribution of O. eremita was not random with respect to tree species identity. Tilia cordata and Alnus glutinosa were preferred while Acer platanoides andCarpinus betulus were avoided. The beetle preferred trees about 450 cm in circumference at 1.3 m height with a tendency towards lower occupancies of the biggest trees having circumferences above 500 m. O. eremita did not show any significant preferences accroding to hollow entrance area, exposition and road surface type. Contrary to common belief O. eremita did not prefer oaks. Our result show that preservation schemes and choices of prime areas for conservation for heremit beetles have to included stands of trees other than oak.
EN
Litter production is essential for transfer of energy and nutrients from plant to soil. This paper aims to relate the phenology of litter-fall by common oak (Quercus robur L.) to specific climatic factors. Over three years, two natural stands of Quercus robur (Cerceda with latitude 43 degrees 11'N and longitude 8 degrees 28'W and Lourizan with latitude 42 degrees 25'N and longitude 8 degrees 40'W) near to fifty years old and located in Galicia, Northwest of Spain, were thoroughly studied in the period 1992-1994. The litter was collected in five litter traps (0.5 m wide, 20 cm high) located within a plot of 100 m2. Annual litterfall values were similar in both stands, being approximately between 6 and 11 Tm [dot] ha^-1 (dry weight); the southern stand showed a higher interannual variability. The leaf fraction accounted for the highest percentage of total litter production. Usually it represents more than 70% of annual production, but it has been exceeded by fruits production in the corresponding season (spring in the north and summer in the south). The climatic parameters that had the greatest influence on litter production were total precipitation and absolute maximum temperature with a correlation always higher than 65%. It allows to link litter production with climate parameters with an adjusted correlation coefficient around 70 %, even more in the south plot (Lourizan). With an easy ANOVA analysis it is possible to distinguish the season with greater litter production; it is the autumn in all cases except fruits production as was said above.
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