What is the potential for replacing monocultures with mixed-species stands to enhance ecosystem services in boreal forests in Fennoscandia?

We tested whether the pairing of selected isolates could be used to increase the efficiency of a decay fungus Chondrostereum purpureum (Pers. Ex Fr.) Pouzar to control hardwood sprouting in Finland. We paired C. purpureum strains efficient in sprout control or highly active in laccase production, and tested the efficacy of their progeny in spout control experiments. This procedure resulted in a strain with an efficacy superior to that of the parental strains. The mortality of birch (Betula pendula Roth. and B. pubescens Ehrh.) 1 cm in stump diameter was 78%, 56% and 9% for the best progeny, the best parental strain and the control, respectively. Mortality was only slightly higher for B. pendula than for B. pubescens but no significant differences were found between the number or maximum height of stump sprouts. Our results showed that cross breeding of this decay fungus is a good alternative in attempts to produce efficient biocontrol agents against hardwood sprouting.

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Breeding Increases the Efficacy of Chondrostereum purpureum in the Sprout Control of Birch

Early management of the regenerated seedlings shapes the future stand properties. To address these issues, pre-commercial thinning (PCT) and control treatments were applied to planted Norway spruce (Picea abies L. Karst) and naturally regenerated birch (Betula pendula Roth., Betula pubescens Ehrh.) stands in forest experiments in southern Sweden (lat. 56–57 N) containing 1.1–5.5 m tall saplings. The treatments were retention of 1000 or 2000 stems ha−1 of Norway spruce, with no birch or birch at 1000 stems ha−1. Treatments were replicated with and without annual removal of birch sprouts from stumps. The periodic annual increment (PAI) over five years was calculated for total stand volume and individual trees. The mean PAI of dominant trees was significantly higher both following all PCT treatments than controls, and following low rather than high-density PCT. Birch retention did not affect growth of the dominant trees but PAI was lower in plots with uncontrolled sprouting. The PAI of birch was significantl...

Pre-commercial thinning, birch admixture and sprout management in planted Norway spruce stands in South Sweden

In the establishment phase, several management alternatives could be applied that affect the species composition of the future stand. In this study, tree seedling data from experiments with planted Norway spruce (Picea abies L. Karst) and naturally regenerated species, mainly Silver birch (Betula pendula Roth), were used for six simulated pre-commercial thinning (PCT) scenarios. The scenarios included both monocultures and mixed stand alternatives with various initial spacing of the planted Norway spruce (0, 1600 or 2800 seedlings) and selection of main stems based on relative heights. Further stand development and individual tree growth were simulated until final harvest. Potentially, based on findings of the seedling measurements, the stands could be mixed with five to six species, but the browsing pressure from ungulates reduced this possibility since the height growth for all species except Norway spruce was highly affected by browsing. The simulated mixtures had a small variation between the PCT scenarios for the maximum mean annual increment (about 10 %). Although the growth was similar for Norway spruce, the proportion of birch in the final stands differed from 3 to 21 % between treatments and none of the high-density planting treatments generated a mixed Norway spruce–birch forest at the time of final felling.

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Scenario analysis of planting density and pre-commercial thinning: will the mixed forest have a chance?

\n We evaluated the impacts of juvenile stand management on wood production based on a nationwide scenario analysis. Measured plot-level information of the Finnish 11th National Forest Inventory (NFI) from juvenile stands formed the initial data for the analysis. To represent a total of 2.5 million hectares of productive forest land available for wood production, 6900 sample plots were selected. We predicted the development of the sample-plot stands for the next 100 years using the Motti stand simulator. We examined the impacts of juvenile stand management, including early cleaning and precommercial thinning, with three scenarios of different intensities of early-stage management (intensive, no management and business-as-usual). The results showed the benefits of juvenile stand management: earlier harvesting revenues, larger total removals, more valuable wood in the removals, and additional benefits that are associated with the first commercial thinning (i.e. no need for clearing before thinning, a larger stem size of removed trees). The main downside of juvenile stand management was the cost of the early cleaning and precommercial thinning. According to the results, a €560 million increase in costs would result in a €1700 million increase in stumpage earnings in Finnish forests during the next 100-year period. The 34 million m3 increase in the sawlog yield together with 28 million m3 decrease in the pulpwood yield also demonstrated the nationwide potential for increasing valuable sawlog production by intensive management of juvenile stands.

Benefits of juvenile stand management in Finland—impacts on wood production based on scenario analysis

Young Norway spruce stands (Picea abies [L.] Karst) are typically cleaned of non-crop species on one or several occasions during young stand stage. In order to objectively evaluate the perceived benefits of early cleaning (EC), we studied the effects of EC on three study sites 2–2.5 years after receiving the treatment. Experiments were established as a randomised complete block design with a total of 40 blocks. Although height growth and mortality were not significantly affected, we found that EC substantially reduced canopy competition and, consequently, the mean diameter of released spruce grew 21–32% faster depending on the site. Furthermore, non-crop trees that were cleared during EC had fewer sprouts in two of the three sites and the sprouts were substantially smaller than the corresponding non-crop trees on control in all sites. EC can reduce the cost of pre-commercial thinning because EC reduced the estimated time needed for subsequent management by 18–49%. Thus, EC offers forest owners and manager...

Karri Uotila

Papers

Effects of early cleaning on young Picea abies stands