Vladimir Shanin

Tree species composition affects productivity and carbon dynamics of different site types in boreal forests

The objective was to analyse how differences in the initial proportions of tree species and site fertility affect carbon sequestration in living biomass and soil. We used the individual-based simulation model EFIMOD, which is able to simulate spatially explicit competition between trees for light and nutrients. Simulations were carried out for three site types with distinct initial stocks of soil nutrients. For each site, the 100-years undisturbed dynamics of monocultures and mixtures of three tree species (Betula pendula Roth, Pinus sylvestris L. and Picea abies (L.) H. Karst.) was predicted. Changes in the proportions of competing tree species were dependent on the fertility of the site: on poor sites, pine was the most competent species, while on rich sites, spruce increased its proportion during stand succession. Net primary production (NPP) and soil respiration were the highest in stands of two coniferous species and in stands with a high initial proportion of pine. Mixed stands were more productive than monocultures; the highest overyielding was observed with mixtures of two coniferous species. Simulated NPP and carbon stocks in all pools increased from poor to rich sites. The highest carbon stocks in standing biomass were observed for mixtures of conifer species and three-species mixtures; the greatest accumulation of forest floor occurred in stands with high proportions of pine.

Global Climate Change and Carbon Balance in Forest Ecosystems of Boreal Zones: Simulation Modeling as a Forecast Tool

The individual-based system of models EFIMOD simulating carbon and nitrogen flows in forest ecosystems has been used for forecasting the response of forest ecosystems to various forest management regimes with climate change. As input data the forest inventory data for the Manturovskii forestry of the Kostroma region were used. It has been shown that increase of mid-annual temperatures and precipitation influence the redistribution of carbon and nitrogen supply in organic form: supply increase of these elements in phytomass simultaneously with depletion of them in soil occurred. The most carbon and nitrogen accumulation in forest ecosystems occurs in the scenario without felling. In addition, in this scenario only the ecosystems of the modeling territory function as a carbon sink; in the other two scenarios (with selective and clear cutting) they function as a source of carbon. Climate changes greatly influence the decomposition rate of organic matter in soil, which leads to increased emission of carbon dioxide. The second consequence of the increase in the destruction rate is nitrogen increase in the soil in a form available for plants that entails productivity increase of stands.

New procedure for the simulation of belowground competition can improve the performance of forest simulation models

The major part of existing models of belowground competition in mixed forest stands is limited in explaining the spatial distribution of roots as a response to competitive pressure from neighbours and heterogeneity of soil properties. We are presenting a new spatially explicit and multi-layered discrete model of belowground competition, RootInt (ROOTs INTake). It describes spatial distribution of belowground biomass and allows simulation of competition between trees for soil nutrients. The tree-specific area of root zone is calculated on the basis of stem diameter, with site-specific modifiers to account for the effect of soil fertility and moisture. The shape of root zone is dependent on the amount of available nitrogen in the current cell, distance between this cell and the stem base, and the mass of roots of other plants. RootInt was incorporated into ecosystem model EFIMOD to refine the existing description of belowground competition in forest stands with multiple cohorts and tree species. The results of simulation showed that bringing more complexity into structure of stand (including initial spatial locations of trees, species composition and age structure, vertical structure of canopy) resulted in higher spatial variation in competition intensity, as well as in higher rates of resource uptake. This indicates that stands with complex canopy structure had high plasticity in their root systems and were adapted to intensive competition for soil resources.

Spatial distribution features of the root biomass of some tree species (Picea abies, Pinus sylvestris, Betula sp.)

The effect of intra- and interspecific competition on the spatial distribution of the biomass and mortmass of woody plant roots in mixed tree stands has been studied. It has been found that the mass of roots in the samples from tree pairs of different species is higher than in the samples from monospecific pairs. Species-specific differences in the vertical distribution of roots and the effect of intra- and interspecific competition on the spatial structure of biomass have been shown. It has been noted that the proportion of dead roots increases almost linearly with depth.

Evidence of Plant Biodiversity Changes as a Result of Nitrogen Deposition in Permanent Pine Forest Plots in Central Russia

Abstract: This study examines the influence of the increased atmospheric nitrogen (N) deposition observed in central Russia between 1960 and 2010 (with a peak in 1990) on biodiversity and the availability of N in soil in pine forests. Shifts in N availability in soils of 3 pine plots were analyzed using presence/absence chronosequence records of the dynamics of ground vegetation plants and a set of specialist plant species with a narrow range of tolerance as bioindicators of soil richness. We assumed that changes in plant communities might be caused by increased atmospheric N input. To examine this assumption, (i) the species composition of forest ground vegetation was analyzed using the Ellenberg N scale and the Tsyganov N scale, which was developed for forest vegetation in European Russia, and (ii) the dynamics of the main N pools were examined using simulation models of forest growth and elements cycling in the forest—soil system. Our results confirm that changes in the ground vegetation communities experiencing eutrophication occurred in all plots. The number of indicators of N-rich conditions for these plots reached a maximum in 1990, the year N deposition reached its maximum in this area. The decline in the number of oligotrophic species indicated that N-poor soils decreased over the monitoring period. Model simulations showed an increase in labile N compounds in the soil and in the total N pool in forest ecosystems. Our results demonstrate an acceleration of natural succession due to atmospheric nitrogen deposition in this region.

Modeling the Dynamics of Natural Forest Ecosystems in the Northeast of European Russia under Climate Change and Forest Fires

Abstract: The individual-based EFIMOD simulation model was used for regional-scale assessments of the dynamics of basic characteristics of the carbon and nitrogen balance in the forest ecosystems of north central Russia. Two forest strict nature reserves were chosen as case studies. Data from the National Forest Inventory were used for model initialization. Initial soil data were taken from a soil survey database containing data on soil organic matter and nitrogen content in the organic layer and mineral soil for different forest types and regions of European Russia. Standard meteorological data were used as climatic inputs. Two simulation scenarios (without disturbances and with forest fires) were coupled with 2 climatic ones (actual climate and the scenario of climate change). The main sources of uncertainty were analyzed and the model parameters were evaluated. A Monte Carlo procedure was applied for evaluation of the robustness of coefficients. Simulation results showed that the greatest carbon accumulation occurred in the scenario without disturbances. Fires resulted in significant losses in soil organic matter and tree biomass through direct and indirect carbon dioxide emissions. Simulated climate change led to an increased decomposition rate of soil organic matter and a related increase in the productivity of vegetation; however, for this region, the carbon balance was positive. This was primarily because young and middle-aged stands are prevalent in the region modeled. A full analysis would require analytical data on the possible dynamics of mature and over-mature forests in the same scenarios of climate change and forest fires.

Model Predictions of Effects of Different Climate Change Scenarios on Species Diversity with or without Management Intervention, Repeated Thinning, for a Site in Central European Russia

The EFIMOD-ROMUL soil-vegetation dynamic model of carbon and nitrogen cycles in forest ecosystems and a static ground vegetation model BioCalc were used for simulating the dynamics of forest ecosystem parameters and prognosis of plant species biodiversity under two management and two climate change scenarios. A large forested area occupying approximately 1,800 km2 on the Central Russian Plain (in Kostroma administrative region) was taken as a case study. Natural forest development (forest reservation) and clear cutting regime were taken as the management scenarios. The most dramatic climate change based on HadCM3 model and A1Fi emission scenario and ‘stationary climate’ were taken as the climatic scenarios. The simulation results showed that clear cutting impacts on forest biodiversity are very strong in the study area and climate warming has minimal effect on biodiversity under the clear cutting regime but climate changes lead to a slight decrease in species diversity under the forest natural development.

20 - DLES: A Component-Based Framework for Ecological Modeling

Abstract Discrete Lattice Ecosystem Simulator (DLES) is a component-based framework which facilitates integration of stand-alone models with spatial interactions, and comparison between models. DLES allows coupling of models of different spatial and temporal resolution. The main features of our approach are (1) the system of models isn’t a “monolithic program” (single executable file), but a number of stand-alone modules that can be easily added to, and removed from, the system; (2) modules exchange data with each other via a shared area of memory controlled by a special system unit; and (3) a module can be either a submodel or another data provider (file, database, etc.).

Pattern of Biomass Partitioning into Fractions of Boreal Trees

Ratios between above- and underground phytomass of tree organs were studied for different forest types. The partitioning of phytomass into tree fractions was described using rank distributions characterizing the relationships between the resource volume available for each tree organ and the ranks of biomass fractions. Species-specific parameters of biomass partitioning into tree organs were calculated, and the dependences of these parameters on the forest type and tree size were revealed. Independent verification of the biomass distribution model was performed.

THE EFFECT OF ABOVEGROUND COMPETITION ON SPATIAL STRUCTURE AND CROWN SHAPE OF THE DOMINATING CANOPY SPECIES OF FOREST STANDS OF EUROPEAN RUSSIA

Background. The most of ecosystem models do not take into account the asymmetry of crowns resulted from the competition between trees. Thus, the objective of the current study is to estimate quantitatively the effect of competition on shape and size of tree crowns. Materials and methods. The study was carried out in mixed and pure spruce, pine and birch stands in the Moscow and Novgorod regions. Mapping of trees was carried out on 14 sample plots of 25×25 m in size. Stem diameter, crown length and crown spread in four cardinal directions were measured for each tree. The relationship between crown size and tree stem size was analysed, as well as spatial distribution of stem bases and centroids of crown projections. Results. We found that crown size and shape is strongly dependent on tree species, its location in stand, and stand density. Pioneer tree species are characterized by relatively narrower crowns with high relative crown base height while the late-successional tree species have relatively wider crowns. The asymmetry of crown projection was shown to be strongly influenced by a tree neighbourhood. We also found that centroids of crown projections are distributed in space more regularly than stem bases. Conclusions. The species-specific features in crown development were shown. The analysis of results confirmed the previously described mechanism of adaptation to competition from neighbouring trees through asymmetric crown expansion in different directions. The relationships derived can be used for development of improved algorithm of simulation of aboveground competition. New procedure will allow us account the influence of a tree neighbourhood on the size and shape of its crown.