Long-term dynamics of stand structure and regeneration in high-stocked selection fir-beech forest stand: Croatian Dinarides case study

Abstract

In recent decades, changes in stand structure in Central European fir-beech forests, such as accumulation of large-diameter firs, fir dieback, and poor regeneration, have been well documented. Besides environmental factors, light harvesting was suggested as one of the main drivers of the negative structural dynamics of these forests in Croatia. This study applied the MOSES 3.0 stand simulator on permanent sample plot data to reconstruct stand development over the past 20 years and simulate long-term projections of selection stand structure and regeneration with respect to theoretical values, using three management regimes differing by the applied harvesting intensity (traditionally applied, theoretical intensity, and no management). Sample plot data from three sets of detailed measurements (1992, 2002, and 2012) were used for validation of the simulator, and eleven 10-year cycles of management were then simulated under the above management scenarios. Results showed a positive influence of harvest intensity on stand regeneration and the achievement of a targeted selection structure in the long term. Two management scenarios predicted a decrease in stand volume (34% and 40%, respectively), an increase in the initial percentage (28%) of beech and maple (58% and 75%, respectively), and the achievement of optimal stand regeneration of 11-13 recruited trees per hectare annually (60% firs). No management scenario could achieve old-growth structure (accumulation of standing stock, large trees, and deadwood). The theoretical intensity scenario was evaluated as the better approach to be applied in this type of forest stands in Croatia.

The Influence of Increased Salvage Felling on Forwarding Distance and the Removal—A Case Study from Croatia

“…A large amount of tree dieback brings unfavourable effects of low felling densities and planning of time-space distribution of felling areas. Future management and development of oak forests due to oak dieback and decreasing stand structure quality and their spatial heterogeneity depend on actual age-class structure, intensity and spatial-temporal dynamics of forest regeneration [14]. The most probable reasons for such a large share of salvage felled timber are: (1) unfavourable climatic conditions (dry summers) where climate change affects forest ecosystems and timber production [17], (2) falling groundwater levels due to the construction of Sava-Odra canal where river regulation disrupts flood patterns of lowland forests [27] and increases stress to ecosystems [28], (3) low removal values in past MP's, and (4) non-execution of the prescribed regular fellings due to their replacement with salvage fellings.…”

“…The analysis of the structure of felled timber volume will be classified depending on its origin i.e., type of felling into (1) the main felling which consists of: (1.1) shelterwood system regeneration, (1.2) salvage felling, (1.3) clearcut (due to the land conversion), and (2) the intermediate felling which consists of: (2.1) thinning, (2.2) intermediate salvage felling. Such felling classification is usual in Croatian forestry and is prescribed by management plans for both state or private even-aged forests [13,14].…”