European Journal of Forest Research最新文献

Prolonged periods without precipitation in spring prevent timely and rapid germination of pioneer tree seeds and could lead to an accelerated loss of germination capacity (reduced lifespan). To get knowledge about the shortening of seed lifespan and, thus, the shortening of natural regeneration windows under climate change, an experiment was conducted. Seeds of Alnus glutinosa, Betula pendula, Populus tremula, Salix caprea, Larix decidua, Pinus sylvestris, and Picea abies were exposed to temperatures of 15 °C, 25 °C (past or present climate), and 40 °C (future climate) with low or high humidity for a period of 3 months. Regardless of air humidity, the initial germination percentage of Alnus glutinosa, Betula pendula, Larix decidua, and Pinus sylvestris seeds decreased only slightly by 5–15% over the 91-day period when stored at 15 °C and 25 °C. For Populus tremula and Salix caprea, time windows of maximum 14–49 days and 42–91 days were identified, respectively.

However, as climate change progresses with rising temperatures and increasing absolute air humidity values, the window of opportunity for successful germination will shorten for all studied tree species. In the moist air humidity variant of 40 °C, the germination percentage dropped to 0% after 42 days for Alnus glutinosa, Betula pendula, and Larix decidua. The natural regeneration window will be reduced by half from more than three months to about three weeks under climate change. The lifespan of Populus tremula and Salix caprea seeds will be shortened to 1 week. For Picea abies, the time window will shorten to a maximum of 28 days.

Mitigating future forest risks, safeguarding timber revenues and improving biodiversity are key considerations for current boreal forest management. Alternatives to rotation forestry likely have an important role, but how they will perform under a changing climate remains unclear. We used a boreal forest growth simulator to explore how variations on traditional clear-cutting, in rotation length, thinning intensity, and increasing number of remaining trees after final harvest (green tree retention), and on extent of continuous cover forestry will affect stand-level probability of wind damage, timber production, deadwood volume, and habitats for forest species. We used business-as-usual rotation forestry as a baseline and compared alternative management adaptations under the reference and two climate change scenarios. Climate change increased overall timber production and had lower impacts on biodiversity compared to management adaptations. Shortening the rotation length reduced the probability of wind damage compared to business-as-usual, but also decreased both deadwood volume and suitable habitats for our focal species. Continuous cover forestry, and management with refraining from thinnings, and extension of rotation length represent complementary approaches benefiting biodiversity, with respective effects of improving timber revenues, reducing wind damage risk, and benefiting old-growth forest structures. However, extensive application of rotation length shortening to mitigate wind damage risk may be detrimental for forest biodiversity. To safeguard forest biodiversity over the landscape, shortening of the rotation length could be complemented with widespread application of regimes promoting old-growth forest structures.

Efficient forest operations are essential for forest enterprises, who provide wood and numerous ecosystem services for the society. Important factors influencing the efficiency of forest operations, and thus the harvesting costs, are the level of mechanization, the harvesting method applied, the forest road network, and the training of the labourers. The cost of labour, i.e. salaries, is another important driver of harvesting costs. However, its effect on and relative importance for overall harvesting costs is poorly described in the scientific literature. Thus, this study aims to analyse the influence of labour costs in more detail, especially on the country-wide wood harvesting potentials. In addition, we aimed to cross-compare the effect of labour costs with the effect of switching to a more efficient harvesting method. For this purpose, we calculated timber harvesting costs with varying salaries for all sample plots of the Swiss National Forest Inventory (NFI) for both, the currently applied harvesting method recorded in the NFI, and the potential best suitable harvesting method. A 1% change in labour costs affects harvesting costs by 0.33–0.77%, depending on the harvesting method applied. The influence is larger for systems that involve a large share of motor-manual work and for cable-based methods. Changing labour costs by ± 30% affects the number of plots for which timber harvesting is economically feasible, by 5 to 15 percent points. The effect of switching from the current to the best suitable harvesting method is comparable to that of reducing labour costs by 15–30%. These results indicate that the efficiency of wood harvesting can be increased with further mechanization and does not require cutting salaries of forestry personnel. In that, our results may inform forestry planning and policy making at regional to national level.

Deadwood is known to be an irreplaceable substrate for various groups of organisms but its importance for vascular plants is still unclear. To examine which deadwood characteristics promote its colonization by vascular plants and whether species can prefer this substrate to mineral soil (or vice versa), we used regression modeling and ordination methods to analyze an extensive data set of vegetation records from more than 1800 pieces of lying deadwood and 200 control plots on soil. Data were collected in four old-growth forest sites ranging from lowland alluvial to mountain spruce forests. Colonization of deadwood of all decay classes, including freshly fallen logs, was frequent at all study sites. The density of colonizers differed between deadwood species, increased with deadwood decomposition stage and was higher when deadwood was exposed to light. On average, about 40% of observed species showed a preference for either deadwood or soil substrate with preference for soil usually being more common. Species that preferred deadwood to soil were typically early successional species, while those with preference for soil were often hygrophytes or typical understorey species. Most species responded consistently to substrate across multiple sites. With its unique microsite conditions and specific composition of plant colonizers, we highlight the importance of deadwood for herb layer species composition. Deadwood retention should be encouraged not only in protected but also in commercial forests.

Pre-commercial thinning (PCT) is a common silvicultural practice for directing the development of the young stand in Nordic and Baltic countries. However, its impact on the stands carbon (C) cycling is still poorly studied. We carried out a comprehensive case study for estimating net ecosystem production (NEP) in unthinned control plot and in moderately and heavily thinned plots (2,500 and 1,500 trees ha⁻¹ remaining, respectively), in the next growing season after PCT in young Betula pendula stands on mineral soil (Site 1) and Betula pubescens stands on drained organic soil (Site 2). Thus, the study demonstrates post-thinning changes in C cycling in stands of two species of the same genus. The control plots of both sites served as C sinks: NEP 1.5 and 3.6 t C ha⁻¹ yr⁻¹ in Site 1 and Site 2, respectively. However, the thinned plots acted as C sinks on Site 1 (1.8 t C ha⁻¹ yr⁻¹) and as C sources on Site 2 (−1.4 and −3.1 t C ha⁻¹ yr⁻¹ in heavily and moderately thinned plot, respectively). The declined net primary production of trees after PCT was compensated for by the production of herbaceous vegetation and stump sprouts. Soil heterotrophic respiration (Rh) was the largest flux in the C budget of both sites and all treatments. Despite the increasing trend of Rh with increasing thinning intensity on Site 2, no statistically significant difference in the annual Rh flux occurred between the treatments in either site.