Loss of old-growth, and the minimum need for strictly protected forests in Estonia

Abstract

estimation of the historical area of different age classes, critical threshold of its loss for specialist species, and the area; 5) defining gaps by comparing reserve need with current protected forest area; 6) analysis of the model sensitivity to errors in the esti mates of wildfire frequency. Management-incompatible forest (> 100 yr since the last stand-replacing disturbance) covered historically 32-42% of todays forest land. The theoretical minimum need for strictly protected forests was estimated at 8.5-11.3% of current forest land, one-fourth being the buffer amount. However, if current reserves retain their status, filling the gaps for underrepresented forest site types yields a total coverage of 10.4-13.2%. This difference is mostly due to the high present coverage within the current reserves of heath forests and oligotrophic paludifying forests (low silvicultural interest) and drained peatland forests (not a natural site type). The results were relatively insensitive to variation in the fire frequency data, and close to earlier estimates for Fennoscandia. We suggest that the estimated amount of reserve areas should be taken as approximate minimum targets in forest reserve development in Esto nia, even though future studies are likely to increase the accuracy and precision of the estimates.