Question: How do N fertilization and disturbance affect the understorey vegetation, microbial properties and soil nutrient concentration in boreal forests? Location: Kuusamo (66°22′N; 29°18′E) and Oulu (65°02′N; 25°47′E) in northern Finland. Methods: We conducted a fully factorial experiment with three factors: site (two levels), N fertilization (four levels) and disturbance (two levels). We measured treatment effects on understorey biomass, vegetation structure, and plant, soil and microbial N and C concentrations. Results: The understorey biomass was not affected by fertilization either in the control or in the disturbance treatment. Fertilization reduced the biomass of deciduous Vaccinium myrtillus. Disturbance had a negative effect on the biomass of V. myrtillus and evergreen Vaccinium vitis‐idaea and decreased the relative proportion of evergreen species. Fertilization and disturbance increased the biomass of grass Deschampsia flexuosa and the relative proportion of graminoids. The amount of NH4+ increased in soil after fertilization, and microbial C decreased after disturbance. Conclusions: Our results suggest that the growth of slow‐growing Vaccinium species and soil microbes in boreal forests are not limited by N availability. However, significant changes in the proportion of dwarf shrubs to graminoids and a decrease in the biomass of V. myrtillus demonstrate the susceptibility of understorey vegetation to N enrichment. N enrichment and disturbance seem to have similar effects on understorey vegetation. Consequently, increasing N does not affect the rate or the direction of recovery after disturbance. Moreover, our study demonstrates the importance of understorey vegetation as a C source for soil microbes in boreal forests.

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Effects of picking methods on the berry production of bilberry (Vaccinium myrtillus), lingonberry (V. vitis-idaea) and crowberry (Empetrum nigrum ssp. hermaphroditum) in Northern FinlandManninen O. H., Peltola R. (2013). Effects of picking methods on the berry production of bilberry (Vaccinium myrtillus), lingonberry (V. vitis-idaea) and crowberry (Empetrum nigrum ssp. hermaphroditum) in Northern Finland. Silva Fennica vol. 47 no. 3 article id 972. 12 p. Highlights• Berry production of bilberry, lingonberry and crowberry was studied after picking the berries by plastic hand rake, long-handed metal rake, and powerful picking by long-handed metal rake.• Berry production was not affected by the damage caused by any of the picking method.• Current commercial picking methods do not endanger the berry production of the berry species at least in short-term. AbstractThe effect of commercial wild berry picking on berry yields is under a strong public debate in Finland. Especially high concern has been arisen over damages caused by metal rakes used in commercial picking to subsequent berry production. We studied the berry production of bilberry (Vaccinium myrtillus L.), lingonberry (V. vitis-idaea L.) and crowberry (E. nigrum ssp. hermaphroditum (Hagerup) Böcher) after picking the berries by 1) plastic hand rake, 2) long-handed metal rake and 3) powerful picking by long-handed metal rake, in northern Finland during 2010-2012. In the powerful long-handed metal rake treatment the aboveground vegetation was raked twice to the moss layer after berry picking. Biomass, which was removed from the vegetation by rakes was collected and used as a measure of the damage. We assumed that picking by plastic hand rake would result in lowest, long-handed metal rake intermediate and powerful picking by longhanded metal rake highest biomass loss from vegetation. The amount of biomass loss should in turn be reversely reflected into berry production. However, only the powerful picking by longhanded metal rake removed higher amount of biomass than other picking methods in bilberry and lingonberry. In crowberry, the amount of biomass removed by rakes increased from treatment to treatment. Contrary to our assumption, berry production of bilberry, lingonberry and crowberry was not affected by the damage caused by any of the picking method. We conclude that long-handed metal rake used in commercial picking is comparable to hand rake in terms of berry production.

Questions: What are the effects of repeated disturbance and N‐fertilization on plant community structure in a mountain birch forest? What is the role of enhanced nutrient availability in recovery of understorey vegetation after repeated disturbance? How are responses of soil micro‐organisms to disturbance and N‐fertilization reflected in nutrient allocation patterns and recovery of understorey vegetation after disturbance? Location: Subarctic mountain birch forest, Finland. Methods: We conducted a fully factorial experiment with annual treatments of disturbance (two levels) and N‐fertilization (four levels) during 1998–2002. We monitored treatment effects on above‐ground plant biomass, plant community structure and plant and soil nutrient concentrations. Results: Both disturbance and N‐fertilization increased the relative biomass of graminoids. The increase of relative biomass of graminoids in the disturbance treatment was over twice that of the highest N‐fertilization level, and N‐fertilization further increased their relative biomass after disturbance. As repeated disturbance broke the dominance of evergreen dwarf shrubs, it resulted in a situation where deciduous species, graminoids and herbs dominated the plant community. Although relative biomass of deciduous dwarf shrubs declined with N‐fertilization, it did not cause a shift in plant community structure, as evergreen dwarf shrubs remained dominant. Both disturbance and N‐fertilization increased the N concentration in vascular plants, whereas microbial biomass N and C were not affected by the treatments. Concentrations of NH4+, dissolved organic N (DON) and dissolved organic C (DOC) increased in the soil after N‐fertilization, whereas concentrations of NH4+ and DON decreased after disturbance. Conclusions: Disturbances caused by e.g. humans or herbivores contribute more to changes in the understorey vegetation structure than increased levels of N in subarctic vegetation. Fertilization accelerated the recovery potential after repeated disturbance in graminoids. Microbial activities did not limit plant growth.