Лесопригодность экотопов Волго-Ахтубинской поймы для культур сосны

Abstract

In the south of European Russia, the largest sand massifs are found in the zone of dry steppes and semi-deserts. Effective utilization of such lands requires creation of protective forest planting of drought-resistant coniferous species like Scots pine and Crimean pine. The productivity and longevity of such stands vary widely over the territory and depends on the presence of additional to atmospheric precipitation water supply and the root layer mineral supply. In this regard, sand massifs of steppificated river valleys composed of multiphase or single-phase polymineral rocks are of particular interest for afforestation. One of the most important objects of afforestation is the Northern (within the Volgograd region) highest and most drained part of the Volga-Akhtuba floodplain. Volga River damming by the Volga Hydroelectric Station (Volga GES) led to a restructuring of surface and ground water regimes, formation of new conditions of water and mineral nutrition and changes in other important factors of forest ecosystems in the area. The research aims at developing a classification of the Volga-Akhtuba floodplain ecotopes by water-mineral nutrition conditions, cultivation, expected productivity and longevity of pine plantings. We studied relationships of growth parameters of Pinus silvestris L. stands with soil-ground and hydrological conditions in different ecotopes of the large hilly and transitional floodplains after the Volga River damming by the Volga GES. Dynamics patterns of this relationship were revealed. It was found that in the northern part of the Volga-Akhtuba valley (approximately up to the Kapustin Yar – Kamenny Yar line) with increasing stratification, heavier granulometric composition of the root layer to sandy loam layer, lowering the surface level at a small distance from the drainage channel moisture supply and growth of Scots pine plantations improve, forest suitability of ecotopes increases. There is a risk of early decay and death of high-density pine forests in periods of low water and dry years on soils underlain by thick loams. Three groups of ecotope forest suitability were identified according to these indicators, as well as the conditions for the creation of forest plantations, productivity and longevity of plantings. The least favorable ecotopes are in the highlands of the hilly and transitional floodplains with minor soils of different composition on single-phase open-textured sands with deep (more than 4–5 m) groundwater table during low-water season. The most favorable are welldrained areas of the transitional floodplain with light soils on thick stratified predominantly sandy loam sediments, as well as on sands with close to the surface groundwater occurrence. Average ecotopes in terms of conditions are poorly drained areas of the transitional floodplain with minor sandy loam and loamy soils on deep loams.