A.M.Obukhov Institute of Atmospheric Physics
Russian Academy of Sciences

Project dates        2002-2005

Summary

The Project was implemented during 2002-2005 in cooperation with the Chair of Geobotany, M.V. Lomonosov Moscow State University, and western colleagues. 'Early successional changes in forest ecosystems after a gap-forming disturbance' have been described as successive dynamics of species which dominate in the lower forest layers inside the gap, i.e., the perennial grass or/and shrub ones. The 'floristic relay' of these species depends drastically on the forest type and the kind and strength of the disturbance. In clear-cut areas of spruce forest (e.g., in the Bavarian Forest National Park, Germany, or the Central Forest Reserve, Russia) the first colonizers are red raspberry (Rubus idaeus) supplanted usually by small-reed of Calamagrostis spp, an 'ideal weed' which is even able to block the tree regeneration in an open gap; in windthrow areas of beech or spruce forest in Swiss Alps, the Rubus spp. colonize quickly all the patches of disturbed soil cover, then compete for light with survived undergrowth of tree spp. like Betula pendula or Fagus sylvatica. To understand the mechanisms underlying the interrelated dynamics of the first colonizers, we analysed in the field, laboratories and computer rooms the population structures in terms of the chronological age (in years) and ontogenetic stages (along the scales developed formerly in the Russian geobotanic school) of individual plants. Several sample plots were carefully selected to represent certain stages of successional dynamics in three case studies of the Project, and the experiments were laid down where each individual plant, either survived one or appeared anew, has been marked and monitored (once a year, in August) during the three-year Project period. Certain parts of plants were dug out to provide for reliable age determination in the laboratory, and the population age-stage structures were established from the corresponding data-bases of observations. The life cycle graphs (LCGs) have thereafter been constructed as directed graphs of annual aging and ontogenetic transitions over a grid of (a moderate number of) feasible age-stage states. It has been found that plants respond to the changing environment with changes in their ontogenetic pathways, and the LCGs enable monitoring those changes from the year-to-year observation data. The LCGs serve also as the conceptual bases for mathematical modelling of the double-structured population dynamics. A new family of matrix models for the double-structured populations has been developed: the class of traditional Lefkovitch projection matrices for stage-structured populations has been expanded (to Logofet-type nonnegative matrices), the inherent mathematics has been investigated, and the appropriate calibration procedures have been proposed and applied for the particular case studies. When calibrated vs. the data, the projection matrices have produced an estimate of the maximal population growth rate 1 (the dominant eigenvalue), the population structure that guarantees the fastest growth (the corresponding dominant column-eigenvector), and the vector (the corresponding dominant row-eigenvector) of age-stage-specific reproductive values, i.e., the relative contributions by the age-stage groups into the transient dynamics when the initial population structure is different from that of the fastest growth. These model findings have given quantitative certainty to theoretical views on the population dynamics of colonizing spp., while the (linear) matrix models have been found adequate to the phase of extensive population growth. However, after 5-10 years of the extensive growth, the first colonizer undergoes competitor pressures or/and density self-regulation. To illustrate the course of after-disturbance succession in the model terms, we have modified the matrix models for double-structured, single-species population dynamics of Rubus idaeus and Calamagrostis villosa into the non-linear models which incorporate the density-dependent effects responsible for various outcomes of the interrelated dynamics (i.e., competitive coexistence, suppression, or exclusion) at different phases of the succession after clear cutting of spruce forest. A similar approach can be recommended to model the outcome of succession under various scenarios of forest management, which involve the gap-forming disturbances.

Publications

Logofet D.O., Ulanova N.G., Klochkova I.N., Demidova A.N.
Structure and dynamics of a clonal plant population: Classical model results in a non-classic formulation.   Ecological Modelling, 2006, v.196, p. 95-106

Novoselova, E.A., Ulanova N.G., Fischer A.
The population structure of Rubus idaeus in beech-spruce forests clearcuts in the Bavarian Forest National Park (Germany). Topical Problems of Ecology and Conservancy. 2004, vol., 5-6, p.15-17. (in Russian).

Ulanova N.G., Klochkova I.N., Wohlgemuth Th., Logofet D.O., Nobis M.
An approach to combine dynamics of age and life stage in clonal raspberry (Rubus idaeus L.) after disturbance. Folia Geobotanica. 2007.

Ulanova, N.G., Zhukovskaya, O.V., Kuksina, N.V., Demidova, A.N.
Structure and dynamics of silver birch (Betula pendula Roth.) in Calamagrostis epigeios communities on spruce clear-cuts in Kostroma region. Bull. Moscow Society of Naturalists, Biol. Section. 2005, v. 110, 5, p. 27-35.

Zhukovskaya O.V., Ulanova N.G.
Influence of brushing frequency on birch population structure after felling. Ecoscience. 2006, v.13, 2, pp. 219-225.

Project participants

Laboratory of Mathematical Ecology (IAP RAS):

Dept. of Geobotany, Biological Faculty, Lomonosov Moscow State University

Section of Geobotany, Dept. of Ecology, Center of Life and Food Science, TU Munchen, Freising, Germany

WSL, Swiss Federal Institute for Forest, Snow and Landscape Research