Photosynthesis Traits of Pioneer Broadleaves Species from Tailing Dumps in Călimani Mountains (Eastern Carpathians)

The reforestation and stable ecological restoration of tailings dumps resulting from surface mining activities in the Călimani Mountains represent an ongoing environmental challenge. To assess the suitability of different tree species for restoration efforts, photosynthetic traits were monitored in four broadleaf pioneer species—green alder (Alnus alnobetula (Ehrh.) K. Koch), aspen (Populus tremula L.), silver birch (Betula pendula Roth.), and goat willow (Salix caprea L.)—that naturally colonized the tailings dumps. Green alder and birch had the highest photosynthetic rate, followed by aspen and goat willow. Water use efficiency parameters (WUE and iWUE) were the highest for green alder and the lowest for birch, with intermediary values for aspen and goat willow. Green alder also exhibited the highest carboxylation efficiency, followed by birch. During the growing season, net assimilation and carboxylation efficiency exhibited a maximum in late July and a minimum in late June. The key limitation parameters of the photosynthetic process derived from the FvCB model (Vcmax and Jmax) were the highest for green alder and exhibited a maximum in late July, regardless of the species. Based on photosynthetic traits, the green alder—a woody N2-fixing shrub—is the most well-adapted and photosynthetically efficient species that naturally colonized the tailings dumps in the Călimani Mountains.

Ecophysiological Variability of Alnus viridis (Chaix) DC. Green Alder Leaves in the Bieszczady Mountains (Poland)

Alnus viridis (Chaix) DC., green alder, is a fast-growing shrub that grows expansively in the European mountainside. In Poland, A. viridis naturally occurs only in the Bieszczady Mountains (south-eastern part of the country), above the upper forest border. In this study, we assessed the potential of green alder to expand in post-farming areas in the Bieszczady Mountains. We investigated the effects of topographical, climatic, and edaphic characteristics of four various study sites on the physiological and morphological properties of A. viridis leaves in order to answer the question whether the growth of plants in lower positions improves their physiological condition to such an extent that it increases the species invasiveness. This is the first comprehensive ecophysiological study of this species to be carried out in this part of Europe. The photochemical efficiency of PSII, the chlorophyll content, and leaf 13C and 15N discrimination were analyzed. On the basis of leaf radiation reflection, coefficients such as reflectance indices of anthocyanins, carotenoids, flavonoids (ARI2, CRI1, FRI), photochemical index of reflection (PRI), and the water band index (WBI) were calculated. We observed favorable physiological effects in A. viridis plants growing in locations below the upper forest border compared to plants growing in higher locations. As a result, A. viridis may become an invasive species and disturb the phytocoenotic balance of plant communities of the altitudinal zones in the Polish Western Carpathians.

Diversity and Pathogenicity of Phytophthora Species Associated with Declining Alder Trees in Italy and Description of Phytophthora alpina sp. nov

Extensive decline and mortality events of alder trees have recently been observed in several riparian ecosystems in Italy. Since there is little information about the aetiology of this disease and given the high ecological relevance of riparian ecosystems, an in-depth study was conducted in three sites spanning from the Mediterranean to Alpine regions. From spring 2019 to spring 2020, 261 samples of bleeding cankers, rhizosphere soil and leaves used as baits along waterways were collected and used for Phytophthora isolation. Based on morphology, colony appearance and DNA sequence data, 10 species belonging to 6 clades were identified. These included P. plurivora (84 isolates), P. pseudocryptogea (50), P. hydropathica (18), P. gonapodyides (14), P. bilorbang (13), P. pseudosyringae (12), P. lacustris (11), P. acerina (7), P. cactorum (1) and one isolate of the hybrid Phytophthora ×serendipita. In addition, two new Phytophthora species, one of which is described here as Phytophthora alpina sp. nov., were isolated. The pathogenicity of P. alpina and other species obtained from samples collected in the green alder stand was assessed on 3-year-old seedlings. All species proved to be pathogenic on green alder causing symptoms congruent with field observations. Results obtained have allowed us to expand knowledge about alder decline aetiology. The diversity of pathogenicity of Phytophthora species associated with symptomatic alder trees suggested that no single agent is responsible for the disease, but that it is the result of multiple infections of different Phytophthora species, variable in assemblages among sites.

Grossflächige Klassifikation von Gebüschwald mit Fernerkundungsdaten

Large-scale classification of shrub forest with remote sensing data Information on shrub forest distribution and development is important for a range of forestry- and ecologically-related questions, but current and area-wide datasets have been characterized by limited availability. In this study, the mapping of shrub forests dominated by green alder, mountain pine and hazel for the canton of Grison was investigated, based on available nationwide remote sensing data. Satellite data from Sentinel-1 and Sentinel-2, as well as a vegetation height and an elevation model were used. Training areas provided by the canton and supplemented by aerial imagery interpretation were used for a supervised classification with Random Forest, a decision tree-based machine learning algorithm. Independent validation of the results was carried out with data from the National Forest Inventory (NFI). Green alder and mountain pine forests were classified with high accuracy of 92.1% respectively 86.7%, whereas for hazel shrub forests, the internal model accuracy was only 66.7%. The resulting area expansion of the shrub forest was comparable with findings based on the NFI. A direct comparison with the NFI aerial imagery interpretation points revealed major discrepancies. The main reason for this is the different degree of spatial detail. However, NFI areas with a high percentage of shrubs were reliably classified as shrub forest. The method presented here underscores the potential of remote sensing data available throughout Switzerland for an essentially objective, costefficient and large-scale mapping of shrub forests with an accuracy applicable in practice.

Green alder effects on the forest soils in higher elevations

Presented study documents the effects of green alder (Alnus alnobetula [Ehrh.] C. Koch) on the uppermost forest soil layers in mountain areas, respectively in the top part of the Orlické hory Mts. Three variants effect to the forest soil have been studied: pure groups of green alder, pure groups of Norway spruce and Norway spruce stand under-planted by green alder. The effect of alder stands litter influenced some basic soil characteristics: the surface humus accumulation (low), the bases content and base saturation (decreased). The green alder increased the acidification trends in the forest soils of the humus forms on the studied locality and intensified the mineralization and nutrient losses from the soil profile.