HAWTHORN (CRATAEGUS L.) TAXA AND THEIR HYBRIDS IN NORTH-WESTERN ROMANIA: A RECOMMENDATION FOR NATIONAL IDENTIFICATION KEYS BASED ON MORPHOMETRIC ANALYSES

Crataegus species are common and widespread shrubs or small trees across Europe, and are of considerable ecological and agricultural importance. However, controversy still surrounds the taxonomy and ecology of this genus, mainly due to frequent hybridization between sympatric species and introgression of genes. Considering the poor representation of Crataegus-related research in the Romanian botanical literature, we investigated the occurrence and morphology of native Crataegus species and their putative hybrids in north-western Romania. We collected herbarium specimens from three regions (Zărandului Mountains, Transylvanian Plain, Călata region), from a variety of habitats, including forests, grasslands and forest-grassland ecotones. Morphometric measurements were taken on a total of 34 fruit-, leaf- and stipule characters on generative shoots. We used PCA and Random Forest analysis to select for the ‘best’ characters differentiating between species and hybrids. We identified ten different Crataegus taxa, including species, subspecies, varieties and their hybrid nothotaxa: Crataegus monogyna (mainly in grasslands), C. rhipidophylla var. rhipidophylla, C. rhipidophylla var. lindmannii and C. laevigata subsp. laevigata, C. laevigata subsp. palmstruchii (mainly in forests), C. × kyrtostyla nothovar. domicensis, C. × media, C. × macrocarpa nothovar. macrocarpa and C. × macrocarpa nothovar. hadensis (mainly in forest openings and near forest edges). The most common taxa identified was C. × kyrtostyla nothovar. kyrtostyla (common in grasslands, rarer in forests). The best differentiating characters between species and hybrids were number of styles, fruit length, number of teeth on stipules, position of sepals on mature fruits, number of serrations on basal leaf lobe, ratio between serrate part of lower leaf lobe and the entire part, depth of basal sinus, and ratio between sepal length and width. Based on the results of the morphometric analysis and literature review, we constructed national identification keys of all Crataegus taxa identified in this study and other confirmed taxa present in Romania. Additionally, we have illustrated the most common six identified taxa (including hybrids).

Fragmentation dynamics in an Abies religiosa forest of central Mexico

Fir (Abies Mill.) forests of Mexico are relicts of the boreal forests that advanced southwards during glaciation periods. Mexico is a center of diversification of the Abies genus, as there are eight species in its territory, six of which are endemic. The forests of Abies religiosa (Kunth) Schltdl. & Cham. near Mexico City are subject to a process of deterioration. We analyzed the fragmentation dynamics of the A. religiosa forest in the northern region of the Sierra Nevada, Mexico. Land cover change detection was done by means of high-resolution images acquired by the SPOT satellite in 2005, 2010, 2015, and 2018. Habitat fragmentation was observed, with a decrease in the size of dense Abies masses. The area covered by Abies decreased by 22.9%. The area occupied by forest openings increased 3% from 2005 to 2010 and then decreased by 1.8% and 1.6% in the following periods. The land patch type Other Forest Cover increased in both frequency and size, with the area increasing by 23.3%, which warns of a change process towards this patch type. The formation of increasingly smaller and isolated remnants of A. religiosa forest in the Sierra Nevada can lead to the loss of this vegetation relict and its replacement by other types of cover in the short term.

Latitudinal variability of the radiation microclimate in artificial forest gaps in Poland – the modelling perspective

The aim of the study was to characterize latitudinal changes in the radiative microclimate of small forest openings (artificial gaps) under Polish conditions. The global, direct and diffuse radiation on the forest floor in gaps was modelled using the Solar Radiation tool in ArcGiS 10.2 Esri. The gaps were modelled as holes of elliptical shape (60 m × 40 m diameters) in flat terrain and with a depth of 20 to 30 meters to mimic the height of a surrounding tree stand. The range of global radiation diversity on an open and flat surface predicted by our model was comparable with findings of empirical studies. Theoretically, the investigated gaps in the northern-most part of Poland receive only 82% of global solar radiation, 74% direct and 90% of diffuse radiation compared to gaps in the most southern part of the country. The comparison with empirical data indicates that local values of the transmittance parameter of the atmosphere may have a large influence on the actual values of solar radiation and may partially mask the latitudinal impact. Nevertheless, the model constitutes a valuable tool for characterising solar radiation diversity in a gap and supports silvicultural decision-making.

Grouseberry (Vaccinium scoparium Leiberg ex Coville) fruit production in forest openings in Banff National Park, Alberta

Grouseberry (Vaccinium scoparium Leiberg ex Coville) is an abundant dwarf shrub in the understory of many areas of subalpine forest in Banff National Park and has the potential to produce fruit important for wildlife. However, the suppression and prevention of wildfires, which began in the early 1900s in the park, have reduced fire-dependent shrubland and open forest and increased the extent of closed, mature forest. Because canopy closure is typically associated with decreased fruit production by understory shrubs, the decline in fire disturbance may be reducing Grouseberry fruit production. To quantify this effect, we measured Grouseberry fruit production under various forest canopies at 10 sites in Banff during 2004–2012. We measured site openness by modeling photosynthetically active direct solar radiation (dPAR) adjusted for overshadowing by topography and coniferous foliage. We found a positive relation between Grouseberry fruit production and dPAR in 2006 and 2010–2012, but not in 2008 or 2009, the 2 years of lowest fruit production; data were lacking for 2004, 2005, and 2007. We also recorded high Grouseberry fruit densities beginning 5 years after fire removed the forest canopy in four prescribed burns conducted during 2001: fruit production was 3.3 to more than 20 times that in adjacent mature forests in 5 of the 6 years analyzed. This study shows the potential ecological benefits of both prescribed burns and wildfire in upper subalpine forests where Grouseberry is widespread, but fruit production is low under the forest canopy.

The Biology of Canadian Weeds. 146. Rhododendron groenlandicum (Oeder) Kron and Judd

Hébert, F. and Thiffault, N. 2011. The Biology of Canadian Weeds. 146. Rhododendron groenlandicum (Oeder) Kron and Judd. Can. J. Plant Sci. 91: 725–738. Rhododendron groenlandicum (Oeder) Kron and Judd, bog Labrador tea, is an evergreen shrub from the Ericacae family native to North America. Bog Labrador tea is associated with the later stages of forest successions in black spruce forest stands of the boreal ecosystems with cool climates, but responds aggressively to forest openings where it is already present. In general, bog Labrador tea is associated with nutrient-poor, acidic soils, with drainage ranging from moist to wet. Layering is the main regeneration strategy of the species; evidence suggests that this could be especially true following disturbances that open the forest canopy. Sexual reproduction maintains viability in undisturbed communities through wind or water dispersal. Rhododendron groenlandicum acclimates more rapidly relative to black spruce after perturbations through a higher rate of resource utilization when resources are available. The species is a highly competitive shrub for soil nutrients; it competes with regenerating conifers for soil nitrogen and phosphorus. It can also assimilate organic nitrogen from the soil through its mycorhizae. These characteristics may lead to the formation of ericaceous heaths that can stay unforested indefinitely. However, this species can be eradicated by herbicides (glyphosate) and heavy site scarification can limit its propagation.