Typological structure and productivity of black poplar stands in different natural and climatic zones of the plain part of Ukraine

Abstract

Introduction

Over last decades, the climate change has caused changes in the habitats of plants. Between 2000 and 2010 in Ukraine, the area of poplar and aspen trees has been increased by 30 %. The area of black poplar (Populus nigra L.) stands is about 46 % of the total area of the poplar forests of in the plain part of Ukraine. Black poplar trees are of ecological and economic significance as they provide important ecosystem services including protection of soils, water bodies and agro-landscapes, phytoremediation of degraded land, rehabilitation of vulnerable ecosystems, desertification control, and reclaiming disturbed landscapes. They absorb carbon effectively and contribute to climate change adaptation and mitigation. Therefore, it is necessary to systematize data on the forest-typological structure, ecological range, condition and productivity of black poplars in various natural and climatic zones of Ukraine.

Materials and Methods

The growing stock volume and age structure of black poplar stands were analyzed in different typological growing conditions in Polissya, Forest-steppe, and Steppe using mathematical processing of the data from electronic subcompartment database of Production Association “Ukrderzhlisproekt” as of 01.01.2011. In total, we had analyzed over 4,500 subcompartments where black poplars are the main species in the canopy layer. The outlines of the black poplar location macro complex were applied to the Alekseev-Pogrebnyak edaphic grid in accordance with the distribution of the stand area at a certain edatope.

Results

As of 01.01.2011, the total area of forests in the plain part of Ukraine, where black poplar is the main species, amounted to 13.5 thousand hectares, including 50.4 % in the Steppe, 37.8 % in the Forest-Steppe, and 11.9 % in Polissya. Black poplar forests are representing in almost all ecological range. Most of them are concentrated in mesic (fresh) (35.1 %) and meso-hygric (moist) (52.7 %) hygrotopes (soil moisture) and oligomesotrophic (poor) (27.5 %) and mesotrophic (medium) (47.1 %) trophotopes (nutrient statuses). Macro complexes of habitats of black poplar were defined in different natural and climatic zones of the plain part of Ukraine and corresponding habitat figures were constructed. In optimal growth conditions (meso-hygric and hygric mesotrophic (C_3-4) and meso-hygric and hygric megatrophic (D_3-4)), 38.9 % of the total area of the black poplar stands is concentrated. Here black poplar forms the most productive tree stands.

A significant differentiation in the dynamics of areas and stocks of poplar stands has been found by age classes in different natural and climatic zones and typological range. Stands of VII and higher age classes were dominating. In Polissya, the actual maximum growing stock was recorded at the age of 45 in meso-hygric mesotrophic (C₃) (337 m³·ha^-1) and mesic mesotrophic (C₂) conditions (315 m³·ha^-1); in Forest-Steppe – in the Х–ХI age classes in meso-hygric megatrophic conditions (259 m³·ha^-1); in the Steppe – in the X–XIII age classes in meso-hygric megatrophic conditions (279 m³·ha^-1). The area is dominated by stands that growing by the third site class and below: 76.2 % in Polissya, 83.9 % in Forest-Steppe, 91.8 % in Southern Steppe and 95.6 % in Northern Steppe. In this regard, developing yield tables for black poplar stands aged over 40 is required.

Conclusions

The outlines of the macro complex of black poplar location had been forming around meso-hygric mesotrophic conditions (C₃). In the Forest-Steppe, the figure’s contours were propagated in the direction to the mesic oligomesotrophic and the meso-hygric mesotrophic conditions. In the Steppe, the macro complex of black poplar location is represented by the largest diversity of the typological spectrum. The widespread use of black poplar beyond the locus of the ecological habitat causes significant differentiation in growth and development, which negatively affects the productivity of forest stands and their functional capacity. The distribution in the age groups of the black poplar stands is unbalanced. The area of over-mature plantations was found to be excessive and the area of young poplar stands was small. In the Steppe, the black poplar is aging most intensely. In the meso-hygric hygrotopes, the best productivity was identified for the black poplar stands in the mesotrophic conditions, a little poorer – in the megatrophic conditions, and the worst – in the oligomesotrophic conditions.

12 Figs., 1 Table, 10 Refs.