Consequences of non-intervention management for the development of subalpine spruce forests in Bulgaria

Abstract

Subalpine spruce forests are among the best preserved woodland ecosystems in Bulgaria with respect to their structure, functions, and biodiversity. Considerable territories of these forests were declared as protected areas at the beginning of the twentieth century, which allowed them to develop predominantly naturally. Nowadays, climate changes and the consequent increasing number of disturbances in the spruce forests across Europe raises the question to what extent the non-intervention regime of protected forests is compatible with the concepts of sustainable management and the protection functions of these forests. To answer this question we studied the natural development of three subalpine spruce forests in the nature reserves Parangalitsa (1933) in the Rila Mountains, Bistrishko branishte (1934) in Vitosha Mountain, and Beglika (1960) in the Rhodopes Mountains. We created GIS databases for these reserves and used them to analyze satellite and field data. We found that small- and large-scale disturbances such as windthrows, bark beetle outbreaks, and fires are part of the natural dynamics of subalpine spruce forests. Their resilience to disturbances is mainly dependent on the availability of structural elements that are often missing in managed forests, such as heterogeneous forest structures and spatial patterns, as well as specific regeneration substrates such as deadwood or windthrow mounds. Thus, we recommend that the sustainable management of subalpine spruce forests should be focused on preserving and, where needed, restoring the structural elements that are characteristic for the natural spruce forests.