Temperate forest development during secondary succession: effects of soil,dominant species and management

With the increase in abandoned agricultural lands in Western Europe, knowledge on the successional pathways of newly developing forests becomes urgent. We evaluated the effect of time, soil type and dominant species type (shade tolerant or intolerant) on the development during succession of three stand attributes: above-ground biomass, stand height (HT) and stem density (SD). Additionally, we compared above-ground biomass (AGB) in natural and planted forests, using ten chronosequences (8 from the literature and 2 from this study). Both AGB and HT increased over time, whereas SD decreased. HT, SD and AGB differed among species types. For example, birch had greater HT than alder, willow and ash at a similar age and had higher SD than pine and oak at a similar age. However, birch showed lower AGB than pine. HT and AGB differed among soil types. They were higher in rich soil than in poor soils. Comparative analysis between chronosequences showed an effect of the regeneration method (natural regeneration vs plantation) on above-ground biomass. Planted sites had higher AGB than natural regeneration. Time, soil type, species and regeneration method influenced the mechanism of stand responses during secondary succession. These characteristics could be used to clarify the heterogeneity and potential productivity of such spontaneously growing temperate forest ecosystems.     

The influences of forest stand management on biotic and abiotic risks of damage

? This article synthesizes and reviews the available information on the effects of forestry practices on the occurrence of biotic and abiotic hazards, as well as on stand susceptibility to these damaging agents, concentrating on mammal herbivores, pest insects, pathogenic fungi, wind and fire.

? The management operations examined are site selection, site preparation, stand composition, regeneration method, cleaning and weed control, thinning and pruning, and harvesting. For each of these operations we have examined how they influence the occurrence of biotic and abiotic damaging agents, the susceptibility of European forests, and describe the ecological processes that may explain these influences.

? Overall, we find that the silvicultural operations that have the largest influence on both biotic and abiotic risks to European forest stands are closely related to species composition and the structure of the overstorey. Four main processes that drive the causal relationships between stand management and susceptibility have been identified: effect on local microclimate, provision of fuel and resources to biotic and abiotic hazards, enhancement of biological control by natural enemies and changes in individual tree physiology and development.

? The review demonstrates an opportunity to develop silvicultural methods that achieve forest management objectives at the same time as minimising biotic and abiotic risks.

     

Future harvesting pressure on European forests

We provide quantitative insight in the spatial distribution of the future supply of wood as a raw material from European forests (27 countries) until 2060. This supply is tested for two scenarios: ‘projection of historical management’ and ‘new management trends’ and compared against a benchmark scenario. The new management trends scenario incorporates influences of issues as nature-oriented management, carbon credits and increased demand for bio-energy. The results of these projections provide insight in the state of the European forests and indicate that under the ‘new management trends’ supply can still increase to 729 million m³ by 2060 in Europe, whereby almost throughout Europe we allow harvest to be higher than increment for some time. Without linking countries dynamically through international trade, we identify regions where harvesting pressure is highest. Under the new management trends scenario, the harvested volume is reduced with 82 million m³/year (compared to ‘projection of historical management’) because of stricter management constraints. However, the management regimes as parameterised here allow harvesting pressure to remain highest in Central Europe and some Scandinavian countries, notably Finland and Norway.

Development of forest carbon stock and wood production in the Czech Republic until 2060

? This study describes the scenarios of likely development of carbon pools in managed forest ecosystems of the Czech Republic. The analysis was based on a matrix scenario model (EFISCEN), adopting a novel parameterization based on forest stand site types and forest typology. The model was constrained by practical management rules as prescribed by the Czech Forestry Act and used to assess production potential for the next five decades under three management and three climate scenarios. The analysis provided data on carbon pool development, including both tree biomass and soil compartments.

? For the tested scenarios of sustainable forest management (wood removals not exceeding increment) the model indicated a slight increase of soil carbon pool. For the possibly largest removals (maximum sustainable felling scenario), soil carbon stabilized within two or three decades reaching a mean value of about 8.1 kg/m² for. At the same time, the mean carbon stock held in biomass reached about 10.2 kg/m² including belowground parts. No decline of soil carbon was observed for any of the tested scenarios.

? We conclude that it is reasonable to assume that soil carbon is not a source of carbon under the current management constraints as implemented in the Czech forestry practice.