Influence of ash-leaved maple (Acer negundo L.) on scots pine natural renewal in Barnaul ribbon pine forest

Abstract

The influence of ash-leaved maple (Acer negundo L.) on the natural regeneration of scots pine in the Barnaul ribbon forest in different types of forest growing conditions is considered. It was found that the ash-leaved maple forms a dense, closed undergrowth up to 10 m high in moist forest-growing conditions (A3), whereas in fresh forest-growing conditions (A2) it was noted only once. The closeness of the undergrowth of maple in the grass forest is 0,8…1,0 units, while the undergrowth with a predominance of local plant species (Siberian mountain ash, goat willow) in the grass forest has a closeness of no more than 0,5 units, in the fresh forest no higher than 0,2…0,4 units. The undergrowth of maple strongly obscures the components of the forest located under it: living ground cover and undergrowth. The shading of the living ground cover leads to its significant transformation, with a change in the floral composition and structure. Shading of the undergrowth leads to a complete absence of seedlings, self-seeding and the actual undergrowth of the common pine, interrupting the process of natural renewal. Using the obtained values of illumination under the canopy of the forest, it was found that in a grassy forest with a maple understory, the relative illumination is no more than 7,9 %, whereas in a grassy and fresh forest with an undergrowth of local species, 29,5…47,9 %. The density of pine undergrowth in a fresh forest with undergrowth of local species is 7,5…17,5 thousand units/ha, which is 3–7 times more than in a grass forest with undergrowth of local species. There is a close positive relationship between the relative illumination under the forest canopy and the density of undergrowth (r = 0,830). Ash-leaved maple acts as an aggressive undesirable breed, which limits the most important environmental factor — illumination, leading to the disappearance of pine undergrowth under the canopy of the forest.