An analysis of forest ecosystem structural variation in Scots pine dominated stands: A methodolocical consideration based on the Estonian Network of Forest Research Plots

Background/Question/Methods

Changes in regional or global biological diversity or spatial distribution reflect the reactions of organisms in these ecological systems to modified environment conditions. Changes in the behavior of any single species, taxon or geographic region have a number of possible explanations including not only climate change but also globally extensive human-induced land use changes. Different management intensities and patterns are intermixing with disturbances. Disturbances operate at multiple spatial scales and often disturbances at different scales interact, producing multi-scale habitat diversity, from microhabitats to landscape. In the past, when methods for growth and yield prediction of a given tree species were used, it was assumed that tree growth besides other factors (stand density, age of the stand and management regime, genetics of the trees, etc.) is largely predefined by site productivity. Currently, three different methodologies are used in forest ecosystem dynamics monitoring: long-term permanent sample plots, eddy covariance flux measurements and dendrochronology. In modelling long-term forest dynamics based on long-term research plots, it is possible to detect the changes or irregularities in development. Still, in most cases these historical time series lack information about known disturbance events and more importantly, about the exact agents causing these events.

Results/Conclusions

In the current study we focus on analysing a forest ecosystem in basic structurally similar functional units comprising trees, ground vegetation and soil. For the study of these three structural units, the combined monitoring of single tree growth variables, the detiled inventory of ground vegetation and mechanical and chemical description of soil has been started in the Estonian Network of Forest Research Plots (ENFRP) in Estonia. In this study the records of 130 Scots pine dominated plots on Vaccinum sites have been analysed. The stand variables include measures of potential tree growth, tree height and height/diameter relationship derived from the single tree inventory data. A ground vegetation inventory was based on 400 “point” descriptions on each plot. Soil organic matter, pH and elemental composition were characterized on each plot. We present the theoretical framework for analyzing forest ecosystem functional units in the context of natural and anthropogenic disturbances. We distinguish the range of variation within the site type following the known history of these particular forest stands. The aim of the study is to develop the methodological basis to asses how previous disturbance and stand development affect current forest composition and structure, using tree and stand inventory data.