Validation of transfer functions predicting Cd and Pb free metal ion activity in soil solution as a function of soil characteristics and reactive metal content.

According to recent insight, the toxicity of metals in soils is better related to the free metal ion (FMI) activity in the soil solution than to the total metal concentration in soil. However, the determination of FMI activities in soil solution is a difficult and time-consuming task. An alternative is to use empirical equations (so called transfer functions (TFs)) that relate FMI activity in solution to the reactive metal concentration in the solid phase and to soil properties (pH and organic matter content). Here we test the applicability of two sets of TF for Cd and Pb using independent data from a wide range of soil types and regions that are not represented in the datasets used to derive the TFs. From these soils, soil solution was extracted using four different methods. For all these extracts, FMI activities were calculated from total concentrations in solution using the speciation program WHAM VI. In some of the soils, Cd and Pb FMI activities were also measured using a Donnan membrane technique. Most of these FMI activities deviated from the TF predictions by less than one order of magnitude and were within the 95% confidence interval of the TFs, irrespective of the method used to extract soil solution. Predictability was higher for Pb than for Cd and differed also between the two TF sets

EDAPHOLOGY IN THE STRUCTURE OF SOIL SCIENCE AND ECOSYSTEM ECOLOGY

Edaphology (Edaphologia, from Greek εδάφοξ – soil for planting) is a science of soil as a habitat for living beings. On the contrary, pedopogy (Pedologia from Greek πεδον – leg as a thing for walking) is a science of soil properties and formation, namely genetic soil science. Soil science is a relatively young discipline studying the complex «bio-abiogenic» systems. Even the history of soil science is not simple, as the main term was duplicated: pedology and edaphology. Later, Edaphology was driven out from soil science into agricultural chemistry to solve edaphic problems for agricultural plants only. The genetic soil science had been mainly developing that time. However the edaphic problems remained and they were solved both within basic soil science and adjoined sciences. The edaphic component is clearly seen in ecological soil science (soil ecology) that appeared in the middle of the 20th century, but without a return to the initial terminology. In forest soil science, the concept of humus forms is directly related to edaphology because humus forms represent a classification of topsoil organic and organo-mineral horizons that determine the vegetation productivity and they are developed under the impact of the biological cycle in forest ecosystems. The European and North American soil-landscape classifications of forest sites also belong to edaphology. The plant ordination according to the scales of soil moisture and «richness» in ecological botany (geobotany) and lower layers of landscape classifications are of clearly edaphic origin as well. The restoration of the edaphic branch in soil science is necessary for addressing theoretical and especially practical problems in sustainable forest and environmental management under the rapidly changing environment and developing economy

Modelling the Rhizosphere Priming Effect in Combination with Soil FoodWebs to Quantify Interaction between Living Plant, Soil Biota and Soil Organic Matter

A model of rhizosphere priming effect under impact of root exudate input into rhizosphere soil was developed as an important process of the plant-soil interaction. The model was based on the concept of nitrogen (N) mining, compensating for the N scarcity in exudates for microbial growth by accelerating SOM mineralisation. In the model, N deficiency for microbial growth is covered (“mined”) by the increased SOM mineralisation depending on the C:N ratio of the soil and exudates. The new aspect in the model is a food web procedure, which calculates soil fauna feeding on microorganisms, the return of faunal by-products to SOM and mineral N production for root uptake. The model verification demonstrated similar magnitude of the priming effect in simulations as in the published experimental data. Model testing revealed high sensitivity of the simulation results to N content in exudates. Simulated CO2 emission from the priming can reach 10–40% of CO2 emission from the whole Ah horizon of boreal forest soil depending on root exudation rates. This modeling approach with including food web activity allows quantifying wider aspects of the priming effect functioning including ecologically important available N production

MODELING THE DYNAMICS OF FOREST ECOSYSTEMS TAKING INTO ACCOUNT THEIR STRUCTURAL HETEROGENEITY AT DIFFERENT FUNCTIONAL AND SPATIAL LEVELS

In many problems of modern forest ecology, it is necessary to analyze the conjugated dynamics of processes occurring at different spatio-temporal scales of the functioning of plant communities and soils resulted from their interaction under the influence of all edaphic and anthropogenic factors. Mathematical models can be an efficient tool for such analysis. The aim of this study is to present the implementation of a new system of models that makes it possible to reproduce in simulation experiments the spatial structure of forest phytocenoses formed by tree and grass-shrub layers, as well as associated heterogeneity of soil conditions and the diversity of ecological niches at different hierarchical levels. To determine the required level of detail of the spatial heterogeneity of forest biogeocenoses related to the processes of their multi-scale functioning, experimental studies were carried out on permanent sampling plots in the Prioksko-Terrasny State Natural Biosphere Reserve and in the “Kaluzhskie Zaseki” State Nature Reserve. The spatial structure of communities and related heterogeneity of ecological conditions were studied using traditional soil and geobotanical, as well as modern instrumental methods. The obtained data were used to construct the algorithms and to estimate the parameters of different blocks of the new system of models. The implementation of a spatially-explicit process-based system of models has shown its ability to reproduce the dynamics of forest ecosystems, taking into account the species composition and spatial structure of different layers of vegetation and the associated patchiness of soil conditions. Because of a wide range of interrelated ecosystem characteristics implemented in the system of models it is possible to simulate productivity, biological turnover of C and N, and the dynamics of forest ecosystems, taking into account their characteristic spatial structure at different scales. This makes it possible to improve the understanding of ecosystem processes and their contribution to maintaining the sustainable functioning of forests, which can be used for predictive assessments of the efficiency of forest management techniques and in solving other forestry and environmental problems