Assessing the Forest Management Impact on Forest Carbon Dynamics in Romanian Forests

Abstract

Forests play a crucial role in the EU's strategy for decarbonisation and in achieving neutrality targets, primarily through their capacity for carbon sequestration (carbon stock change) and storage (carbon stock) in above-ground biomass, dead organic matter, and soil organic matter. Alongside reforestation, sustainable forest management practices can further enhance the role of forests in decarbonisation. Our focus is on the Argeș-Vedea basin in Romania, a region stretching from the Carpathian Mountains to the Danube River. We analyse systematic sample plots across an area covering 300,000 hectares of forest. We studied the relationship between stand attributes (basal area, diameter at breast height, age, species) and carbon stock changes in various carbon pools, evaluated also under different forest management practices context. Correlation analysis reveals a negative correlation between basal area and carbon stock changes in living trees and litter, which suggests that an increased basal area leads to reduced carbon stock changes (r = -0.15). Older stands tend to have lower net living tree carbon changes due to reduced growth and increased disturbance. Similarly, we found that soil carbon stock generally increases with the age of stands and decreases following disturbance, such as the harvesting of older stands (i.e., on average, by 10%). The effects of various forest management practices (no intervention, clear-cuts, shelterwood, thinning, and stands affected by natural disturbance) on different carbon pools are distinct. While all interventions generally decrease carbon stock in above-ground biomass, thinning operations result in a minor increase, especially in the lower-density stands, but still five times less than non-intervention stands (+13 tC/ha) with a decrease in deadwood carbon, indicating the role of selective removal in forest health maintenance. In contrast, in no intervention management increases living tree carbon, underscoring the benefits of natural forest dynamics. Stands in the initial development stage exhibit the highest carbon sequestration capacity (+11 tC/ha), while stands in the understory initialization stage show a decrease in tree biomass (-11 tC/ha) due to the harvesting operations. Natural disturbances significantly impact the deadwood pool, tripling the carbon stock change compared to shelterwood-managed stands. Stands, where thinning is performed, are the only ones showing decreased deadwood carbon stock change. Similarly, the litter pool decreases in stands undergoing thinning and clear-cutting. Regarding the regeneration pool, stands affected by clear-cuts and natural disturbance (in a five-year period) showed the highest decrease in carbon stock change (-0.03 tC/ha). This research reveals key insights into the variations in carbon stock caused by different management practices and the age progression of forest stands. This information is crucial for accurately modelling the carbon dynamics within forest ecosystems.