Article Digital Mapping of Habitat for Plant Communities Based on Soil Functions: A Case Study in the Virgin Forest-Steppe of Russia Nikolai Lozbenev 1,* , Maria Smirnova 1,2 , Maxim Bocharnikov 2 and Daniil Kozlov 1 1 V.V. Dokuchaev Soil Science Institute, Pyzhyovskiy lane 7 building 2, Moscow 109017, Russia; [email protected] (M.S.); [email protected] (D.K.) 2 Lomonosov Moscow State University, Leninskiye Gory, 1, Moscow 119234, Russia; [email protected] * Correspondence: [email protected]; Tel.: +7-909-966-96-24 Received: 14 December 2018; Accepted: 6 March 2019; Published: 9 March 2019 Abstract: The spatial structure of the habitat for plant communities based on soil functions in virgin forest-steppe of the Central Russian Upland is the focus of this study. The objectives include the identification of the leading factors of soil function variety and to determine the spatial heterogeneity of the soil function. A detailed topographic survey was carried out on a key site (35 hectares), 157 soil, and 34 geobotanical descriptions were made. The main factor of soil and plant cover differentiation is the redistribution of soil moisture along the microrelief. Redistributed runoff value was modelled in SIMWE and used as a tool for spatial prediction of soils due to their role in a habitat for plant communities’ functional context. The main methods of the study are the multidimensional scaling and discriminant analysis. We model the composition of plant communities (accuracy is 95%) and Reference Soil Group (accuracy is 88%) due to different soil moisture conditions. There are two stable soil habitat types: mesophytic communities on the Phaeozems (with additional water runoff more than 80 mm) and xerophytic communities on Chernozems (additional runoff less than 55 mm). A transitional type corresponded to xero- mesophytic communities on the Phaeozems with 55–80 mm additional redistributed runoff value. With acceptable accuracy, the habitat for natural plant communities based on soil function model predicts the position of contrastingly different components of biota in relation to their soil moisture requirements within the virgin forest-steppe of the Central Russian Upland. Keywords: Chernozems; Phaeozems; Central Chernozem Reserve; predictive soil mapping 1. Introduction The most important ecological function of the soil as a component of the environment is to maintain the balance and sustainability of the biosphere under the anthropogenic impact and climate change [1–3]. The direct methods for soil ecological functions evaluation are limited, that is the main cause why researchers focus on indirect indicators of the soil systems functioning: the soil properties—i.e., the chemical composition of the different soil phases [4–7], soil structure [4,8,9], etc.—and the properties of environment connected to the soil by material—energy interactions. The latter include the species composition and productivity of plant communities [10–12] and in a broader sense, serve as the basis for landscape indication when mapping hard-to-observe properties of a landscape from lightly observed factors. The soil is the habitat for the plants—the environment of root nutrition and a seed pool. The study of the soil–vegetation interactions characterizes the features of the habitat for plant soil functions [2,13,14]. Soil structure (aggregate composition and pore space), chemical composition Soil Syst. 2019, 3, 19; doi:10.3390/soilsystems3010019 www.mdpi.com/journal/soilsystems Soil Syst. 2019, 3, 19 2 of 12 (including organic carbon and nutrients concentration), and moisture characteristics are the key properties for the plant’s growth [4,9–11,15–17]. The connection between soil properties and plant parametersSoil Syst. are2018, implemented 2, x FOR PEER REVIEW in the global and regional ecological scales [18–21]. 2 of 13 Our study site is located in the virgin forest-steppe of East European plain. The climatic conditions (including organic carbon and nutrients concentration), and moisture characteristics are the key of the forest-steppe with favorable water-air and thermal regime contribute to the formation of the properties for the plant’s growth [4,9–11,15–17]. The connection between soil properties and plant mostparameters fertile soils are among implemented all the naturalin the global land and areas regional [22]. However,ecological scales the diversity [18–21]. of edaphic conditions determinesOur the study wide site variation is located of soil in the moisture virgin andforest-steppe aeration regimesof East European and, as a plain. result, The variety climatic in plant speciesconditions composition. of the forest-steppe We suppose with that favorable the soil moisturewater-air isand the thermal leading regime factor contribute controlling to the species compositionformation in of the the virgin most forest-steppe,fertile soils among as it all has the been natural qualitatively land areas shown[22]. However, [23]. the diversity of Theedaphic aim conditions of our work determines was the the digital wide variation mapping of ofsoil the moisture habitat and for aeration natural regimes plant communities’and, as a soil function,result, variety soil moisturein plant species conditions composition. and related We suppose plant speciesthat the compositionsoil moisture is in the virgin leading forest-steppe factor landscapescontrolling of V.V. species Alekhin composition Central in Chernozem the virgin forest State-steppe, Reserve as it (Kursk has been region, qualitatively Russia). shown The [23]. objectives The aim of our work was the digital mapping of the habitat for natural plant communities’ soil were to: (1) quantitatively characterize the relationship of the water regime and soil properties, function, soil moisture conditions and related plant species composition in virgin forest-steppe the compositionlandscapes of of V.V. plant Alekhin species; Cent (2)ral define Chernozem the different State Reserve habitat (Kursk types; region, (3) create Russia). and The verify objectives the habitat for a plantwere to: communities (1) quantitatively map. characterize We characterized the relation theship soil of forming the water factors regime features and soil forproperties, each section the of the regularcomposition grid withof plant resolution species; (2) 2.5 define m. The the redistributed different habitat runoff types; value (3) create was modelledand verify inthe SIMWE habitat [24]. Multidimensionalfor a plant communities scaling and map. discriminant We characterized analysis the were soil forming used to factors determine features the for relationship each section between of surfacethe runoff, regular soil grid moisture with resolution regime, 2.5 and m. The plant redi speciesstributed composition. runoff value The was main modelled hypothesis in SIMWE of our[24]. work is thatMultidimensional the plant species scaling composition and discriminant is the result analysis of a complexwere used interaction to determine in the the relationship sequence: between soil forming factorsurface (topography)—soil runoff, soil moisture forming regime, process and plant (redistribution species composition. of surface The runoff)—soil main hypothesis properties of our work (water and airis that regime)—soil the plant species function—species composition is the composition result of a complex of vegetation. interaction in the sequence: soil forming factor (topography)—soil forming process (redistribution of surface runoff)—soil properties (water 2. Materialsand air regime)—soil and Methods function—species composition of vegetation. The2. Materials study was and completedMethods on the sub-horizontal part of the interfluve and gentle slope in the southwesternThe study part of was the completed Central Russian on the sub-horizontal upland of the pa Eastrt of European the interfluve Plain and to thegentle south slope of in the the Kursk city (Figuresouthwestern1) within part theof the Streletsky Central Ru steppessian upland cluster of of the the East V.V. European Alekhin Plain Central to the Chernozemsouth of the Kursk Reserve. ◦ The averagecity (Figure annual 1) within air temperature the Streletsky of steppe study clus areater isof 5.7the V.V.C, theAlekhin amount Central of precipitation Chernozem Reserve. is 590 mm. Soil-formingThe average parent annual materials air temperature are loess-like of study loams, area underlain is 5.7°C, the with amount 8 m byof chalkprecipitation deposits. is 590 mm. Soil-forming parent materials are loess-like loams, underlain with 8 m by chalk deposits. FigureFigure 1. Study 1. Study area area (a) ( areaa) area location location (blue (blue square) square) relativelyrelatively natural natural areas areas and and large large cities, cities, (b) typical (b) typical topographytopography of central of central Russian Russian upland upland and and Central Central ChernozemsChernozems State State Reserve, Reserve, red red square—key square—key plot plot (coordinates(coordinates of the of center—51.5727N,the center—51.5727N, 36.0926E)). 36.0926E)). Soil Syst. 2019, 3, 19 3 of 12 SoilKey Syst. plot 2018, area2, x FOR is PEER about REVIEW 35 ha. Its topography was studied in detail by GNSS surveys.3 of 13 Two Stonex S9III+ GNSS receiver were used. In fixed RTK regimes the positioning accuracy of horizontal coordinatesKey isplot 8 mm,area is vertical about 35 coordinates—15 ha. Its topography mm. was studied About in 10,000 detailof by points GNSS surveys. with accurately Two Stonex defined coordinatesS9III+ GNSS and height,receiver