Browsing by large herbivores can have significant impacts on various ecosystems, and the industries associated with them. However, little is done to explain animal–plant interactions on the basis of browsing frequency. Our study indicates that assessment of summer browsing at the end of the growing season can give a clearer understanding of these interactions and therefore better guide management decisions. In order to quantify the impact of browsers on forest biomass production, a four year long browsing simulation experiment was performed by clipping fresh unripe shoot tops within a freshly clear felled aspen stand. Tree tops were clipped 1, 3-5 and 8 times per growing season with intervals of 2 – 8 weeks. A number of factors were measured; removed fresh apical biomass (A), which represented biomass consumed by animals, the green biomass remaining in autumn (B) and the sum of both A and B (A+B), which composes the total yield of green biomass after each growing season. The frequency of total apical removal during the vegetation period had a significant impact on all three indices. A significant negative relationship between A and B up to a level of fivefold clipping indicates that this is the threshold of compensatory growth, as all indices diminished at eightfold clipping. An 8-fold treating over the period of four years results in the development of grass cover instead of young small deciduous trees and shrubs. Comparison of our results with studies in nature allowed us to standardize the assessment of browsing intensity. Summer browsing intensity is the first index of plant response to browsing and gives an indication of deer fitness before winter. Any compensatory growth caused by deer swicthes to decompensatory growth, when browsing intensity exceeds 50%, whereby the biomass produced cannot effectively replace the biomass consumed.

Keywords: deer, deciduous woods, summer browsing, browsing simulation, apical removal.