Another explanation may be that old forests with low amounts of dead wood are more frequently harvested than old forests with high amounts of dead wood. This may be due to differences in forest owner behavior with some small, private forest owners harvesting at a lower rate (e.g. through longer rotation periods), which could lead to accumulation of selleck kinase inhibitor dead wood. Deeper analyses

are needed to reveal if such a mechanism is likely. Overall, there seems to be a large potential for maintaining higher dead wood levels from the harvested forests. Low levels of dead wood in the northernmost region N Norrland are difficult to explain. Forests > 100 years old held the highest volumes of dead wood indicating that there is a potential for retaining dead trees in young forests after felling. A possible explanation that Selleckchem Doxorubicin cannot be resolved in this study is that forest-owner behavior may differ between regions.

If forest owners in N Norrland are more likely to retain dead wood in retention zones and patches, this would affect the present results. Also, at least to some extent, it could also indicate that fallen trees are extracted as firewood for local use to a larger extent than in other regions. Each region shows a similar pattern with the highest amounts of dead wood in the oldest forest age classes and the lowest amounts in intermediate age classes (21–60 years). A large part of the intermediate age classes were clearcut at a time before retention actions became common practice, and have not produced any considerable amounts of dead wood since then. According acetylcholine to retention recommendations, retention should be practiced at all logging operations, i.e. also at thinnings. The low amounts in intermediate age classes may indicate that

retention at thinning operations is slow to develop. About twice as high deadwood amounts occurred in the age class 0–10 years compared to the age class 11–20 years, in 2007. This indicates that the increase in dead wood has been much higher during the last 10-year period than during the preceding 10-year period. To some extent, decomposition of dead trees such as birches might have occurred 11–20 years after harvest. Deeper analysis of dead wood development before 1997 is not possible though, since such complete dead-wood data are only available from after 1994. The number of living trees in forests 0–10 years old was in 2007 roughly at the same level as in 1955 (excluding the commonly used seed tree P.sylvestris), after a substantial decrease during the 1970s and 1980s. The high levels about 50 years ago were most likely due to a larger use of Norway spruce as a seed tree, more restricted harvest of deciduous trees, and that small, crooked and damaged trees were left at site. The restoration during the last two decades is without doubt due to the retention practice.