What are the advantages and disadvantages of the “selection forest” management system?

Selection forest is a traditional forest management technique that requires little or no management operations, and the major operation is thinning, which helps to sustain the management and productivity of the forests. However, an alternative management system known as selection forest has received comparatively less recognition over the past centuries but has been successfully practiced in the Wolfach forest district of the Black Forest in Germany. This position paper explores the benefits and drawbacks of implementing and practicing this selection forest management system.

The forest management system, known as selection silviculture or cutting, is commonly referred to as the Plenterwald system in Germany. This irregular or uneven-sized forest comprises groupings of trees of all sizes growing in different age classes within a short distance. Interestingly, silver fir, spruce, and sometimes beech and Douglas fir are the primary tree species in selection forest stands. The distinctive characteristic of selection forests is the scarcity of large and medium-sized trees but the abundance of small, young trees. Hence, most selection forests can be found at high elevations in the mountainous zone of approximately 800m above sea level with high 1100–1500 mm average annual precipitation and low average temperatures (7–7.5 °C). Therefore, it is crucial to emphasize certain prerequisite criteria that distinguish selection forests from even-aged and uneven-aged forests. A key prerequisite for the selection of forest management systems is the presence of trees at various developmental stages that are close to each other.

Additionally, a significant criterion is that most trees within the forest exhibit noticeable growth patterns, characterized by slower growth during the initial stages and accelerated growth once they are freed from surrounding vegetation through pruning and thinning operations. Therefore, another management option is periodically harvesting large trees every 5-8 years to support their ongoing growth and development. Selection forests offer numerous benefits. The primary advantage is the continuous production of high-quality timber, which enables regular harvesting every 5 to 8 years in an area spanning 2–3 hectares. This allows for extracting 7-8 trees annually from selection forests, which contain a substantial volume of valuable wood products in high demand per cubic meter per hectare.

Furthermore, harvesting every half a decade provides a steady income to forest owners and makes work available for forest workers. In addition to its economic benefits, the selected forest provides a notable environmental advantage by effectively preventing soil erosion. This is achieved through the presence of diverse tree species in close proximity, which enrich and preserve the soil, resulting in increased soil nutrients and stability. Also, the forest's protective capabilities extend to controlling surface runoff through crown length, varied tree regeneration, and the presence of dead wood and litter.

The selection of a forest management system can also contribute to carbon sequestration, as the forest retains a greater amount of biomass and sequesters more carbon over time. This can help mitigate climate change impacts and contribute to global efforts to reduce greenhouse gas emissions.

Furthermore, selection forests maintain a consistent appearance throughout the year, regardless of the season. Ecologically, selection forests exhibit uniform productivity across different areas and always maintain forest cover, thereby minimizing disturbances in the nutrient cycle. In a nutshell, the practice of selection forest management systems promotes the genuine sustainability of forest ecosystems.

In addition to the advantages of this system, it is essential to consider its specific limitations. One challenge is that converting an even-aged forest system to a selection forest takes a long time to develop to a rotation age of at least 60 years. Another disadvantage is that only shade-tolerant species, such as silver fir, spruce, and beech, survive the early developmental stages in the selected forest environment. Hence, forest owners and workers must ensure continuous management every five years to carry out pruning activities to ensure the survival of young trees, maintain the quality of mature trees, and harvest mature trees permanently to preserve the structure and productivity of the forests.

The most significant drawbacks are the management operations and harvesting costs. This system has high management costs that require qualified foresters, and the high cost of cutting trees depends on the use of experienced chainsaw operators (paying €40 per hour). Therefore, harvesting must be done correctly to remove dead wood and low-quality timber to prevent further harm to regenerating trees and other resource materials.

Additionally, forest disturbances, such as bark beetle attacks, intensive browsing by roe deer, wind throws, and heavy snow, also alter the distribution and structure of the forest during the transitional phases. This hinders the development of forest ecosystems and sometimes results in the death of individual tree species. Since ancient times, the restricted availability of suitable land for the growth of selective forests has posed a significant obstacle. Therefore, the development of trees in selection forests depends solely on a particular topography characterized by stable fertile soils, sufficient moisture content, and shallow depths or gentle steep terrains.

To conclude, the selection of forests serves as a notable illustration of irregular or uneven-sized forest management. However, it is important to note that this system cannot be universally applied because of its drawbacks and the need to satisfy specific requirements. Furthermore, selective cutting has only been implemented on a limited scale, accounting for 1% in Germany and 8–10% in the Black Forest district, with a larger percentage found in Wolfach. Most importantly, forest owners and workers should carefully consider these prerequisite criteria when deciding whether to adopt a selection forest management system and assess whether it is appropriate for their management aims and objectives.