PhD defence: Ditlev Otto Juel Reventlow (hybrid)

Ditlev Otto Juel Reventlow defends his thesis

Transitioning to near-natural forest management – effects on stand structure and wood production

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Senior researcher Thomas Nord-Larsen, IGN

Assessment Committee:
Professor Hubert Hasenauer, University of Natural Resources and Life Sciences, Vienna, Austria
Professor Urban Nilsson, Swedish University of Agricultural Sciences, Sweden
Professor Henrik Meilby (chair), IFRO

The transitioning towards near-natural forestry demands that more knowledge is obtained on these complex forest management systems. This PhD thesis explored selected themes within this general topic. Focus was on the conversion of uniform conifer plantations into more near-natural stands, as well as how to manage such near-natural stands of beech.
Article 1: We investigated how the inmixing of oak into Scots pine plantations affected productivity and stand structure. The results showed that such inmixing both enhanced structural heterogeneity as well as productivity relatively to monospecific stands of oak and Scots pine. Results were due to the better light use efficiency in the mixed stand.
Article 2: We scrutinized how the shelterwood system can be used to convert instable Norway spruce plantations to beech, Douglas fir and silver fir on sandy sites exposed to late frost and high browsing pressure. The results revealed very species specific patterns. While silver fir were completely annihilated in case of shelter removal, Douglas fir and beech tolerated this and these species also had a more steep positive growth response to increasing light from decreasing shelter density. Results were due to species shade-tolerance as well as the influence of late frost and browsing.
Article 3: The third article assessed the long term consequences of different conversion methods (a rather passive approach, heavy shelterwood thinning and gap cutting). The results showed that especially gap scenarios had a potential for creating stands of high structural heterogeneity within a relative short time frame and such scenarios also had a high economic yield, especially when combined with a high degree of target diameter harvesting.
Article 4: We investigated the effect of different pre-commercial thinning in young dense natural regenerations of beech. The results showed that no pre-commercial thinning resulted in an acceptable development of beech crop trees – although early thinning could results in a, modest, increase in diameter increment without decreasing stem quality. We also show that stand edge effects are less important for stem quality than would be expected, at least as long as the stand is sufficiently dense.

A digital version of the PhD thesis can be obtained from the PhD secretary Anne Marie Faldt