Vol 10, No 3 (2019)

Acer negundo L., the invasive tree species of North American origin, is naturalizing in the floodplain forests of Orenburg oblast. Now A. negundo has created an extensive secondary range on the territory of Orenburg oblast and occupies an area of more than 20 000 ha. On the right and left sides of the Tok River in Krasnogvardeysky and Grachevsky districts in the northwest of Orenburg oblast, four test areas of 20 × 2000 m were laid, and inside each test area, 40 sample plots of 20 × 50 m were laid. Nine tree species were considered; the data of records were recalculated per 1 ha. In tree communities of the floodplain of the River Tok, an absolute dominance of A. negundo, which in abundance exceeded all other floodplain tree species (281.13 and 383.25 specimens/ha), was noted. The share of invasive species in the floodplain forests of this area on average was 66.39%. The performed calculation of natural renewal of woody vegetation showed the considerable superiority of undergrowth of A. negundo (130 833.50 and 178 831.50 specimens/ha). Naturalization of A. negundo in floodplains of Orenburg oblast influenced negatively the height, development, and renewal of local forest-forming species, leading to irreversible consequences of degeneration of the floodplain forests.

A field study of common ragweed (Ambrosia artemisiifolia L.) in European Russia provided information on the occurrence and abundance of the species and enabled a prediction of the possible boundaries of species naturalization. As a result, the understanding of the ecological limits of common ragweed distribution related to the limiting environmental factors was refined. Insufficient heat supply during the seed ripening period is the factor that determines the expansion of the species to the north in European Russia. The moisture deficit factor determines the eastern and southeastern boundaries of species expansion. Ecological maps based on MODIS data from the Terra satellite were used in the ecological analysis of geographical distribution of the common ragweed. As a result, the map of the distribution potential of the common ragweed in European Russia was refined and the possibility of species naturalization in the area was plotted on the map.

Cardamine occulta Hornem. (Brassicaceae), an East Asian weedy bittercress, have introduced globally in recent years. First record of this neophyte species in European Russia was made in 2003. According to current data C. occulta was found in nine regions: Leningrad Oblast, Moscow Oblast, Saratov Oblast, Vologda Oblast, Yaroslavl Oblast, the Republic of Karelia, the Udmurt Republic, the city of Moscow and the city of Saint Petersburg. All known populations of C. occulta occupied predominantly man-made habitats. Currently, the species is considered to be a casual or naturalized alien plant. Uncontrollable transfer of the weed along with ornamental plants might lead to its successful spread across the European Russia. Distribution history of the species, as well as a potential for further spread in European Russia are briefly discussed. The main diagnostic morphological features are presented in comparison with those for allied C. hirsuta L. and C. flexuosa With.

The emerald ash borer is a serious pest of ash (Fraxinus spp.) in North America and European Russia. It was introduced to those territories from East Asia in the 1990s. Currently the pest has spread in 12 regions of European Russia. The northwestern border of its range is in the city of Tver. This poses a potential threat to ash trees of St. Petersburg and Western Europe. In 2016 and 2018, green ash trees were surveyed in the summer in several districts of Tver. There are only local foci of the emerald ash borer in the city; mass drying of ash trees is not observed. A species that accompanies the emerald ash borer (the jewel ash beetle Agrilus convexicollis) and a pest parasitoid (Spathius polonicus) were found. Both species are recorded for Tver region for the first time. In addition, parasitoid Coeloides sp. was found inside the bark beetle galleries.

In 2018, a new species, Heracleum ponticum (Lipsky) Schischk., was identified in the Priozersky district of Leningrad oblast. The H. ponticum plant does not contain photodynamically active furocumarins, but interspecific hybrids of this species with the H. sosnowskyi Manden. plant may contain some substances in their juice that are dangerous to human skin. The approximate growing area of H. ponticum is almost 0.7 ha.

The hydrobiological studies carried out in 2017 and 2018 yielded new information on the distribution of the alien species Kellicottia bostoniensis (Rousselet, 1908), discovered in five different-type rivers. This species was found in these rivers for the first time. In the Gnilichka, Vyunitsa, Chernaya, and Kerzhenets rivers and also in the Cheboksary Reservoir, the rotifer was reregistered. The lower reach of the Vetluga River is at the same time the easternmost and northernmost location where this species was found in Nizhny Novgorod oblast. The paper analyzes the findings of K. bostoniensis in the floodplain lakes of the Kerzhenets River, which are new habitats of this species in Nizhny Novgorod oblast. It has been found that rotifers are common in water bodies with various depths and different morphometric and physicochemical parameters. For the first time K. bostoniensis is registered in the water bodies of European part of Russia with a water color index of more than 1000 degrees (Lake Novaya Staritsa—1245.0 deg), as well as in the waters with a low content of dissolved oxygen (0.2 mg/L—Lake Novaya Staritsa).