Articles containing the keyword 'mixed stand'

Shifting cultivation, practiced earlier in Finland, was beneficial for grey alder (Alnus incana (L.) Moench). It can produce seeds early and the early growth of the seedlings is fast. Areas where shifting cultivation was intensive, the areas next to the fields were pure alder stands, next circle was Betula sp. dominated, beyond that could be found Scots pine (Pinus sylvestris L.), and finally Norway spruce (Picea abies (L.) H. Karst.). When shifting cultivation ended, Norway spruce became more common. Many young mixed stands had Norway spruce undergrowth and alder overgrowth. The aim of the study was to find out how the stands develop to spruce dominated stands, and how they should be managed.

The density of spruce undergrowth affects the further development of both spruce and alder. The number of alder stems decreases the faster the denser the spruce undergrowth is. Alder overgrowth slow down the early diameter and height growth of spruce compared to pure stands. Also the diameter and height growth of alder remains smaller in mixed stands. The basal area of spruce develops slowly in the beginning, increases significantly by the age of 30, and surpasses the growth of pure spruce stands in Oxalis-Myrtillus site type. Thus, Norway spruce do not suffer from growing in the undergrowth. In the first years, fast growing alder seedlings limits growth of ground vegetation and protects spruce seedlings from frost.  Later thinning or removal of alder benefits spruce growth. The density of spruce undergrowth decides how much alder can be leaved in the stand. If the spruce undergrowth is thin, more alder can be left in the stand.

The PDF includes a summary in German.

• Kalela, E-mail: ek@mm.unknown

About 40% forest in Finland are mixed stands that have birch (Betula pubescens and B. verrucosa) as one of the species. The aim of this research was to study the structure of root system of birch and compare it to the other main tree species in Finland.

The root systems were dug out and measured in 28 sample plots in Southern and Central Finland, representing different forest site types. Birch roots correspond 30‒100% of the volume of the stem, the largest root systems being in the sandy soils or peatlands. Also the longest lateral roots can be found at these sites. The size variation of root system of birch is larger than in Scots pine (Pinus sylvestris L.), and the vertical root system is in general smaller in birch. Birch seems to be better than pine able to adapt its root system to the existing conditions. The smallest root systems were found in the good forest site types, but the roots grow in the good sites denser than in the poor sites. The lateral roots of the main tree species in Finland, birch, Scots pine and Norway spruce (Picea abies (L.) H. Karst.) grow in different depths, which decreases the competition between the species. This finding gives support to cultivation of mixed stands.

The PDF includes a summary in English.

• Laitakari, E-mail: el@mm.unknown

Mixed forests are known for their ability to provide a wide range of ecosystem services. Such forests have higher biodiversity compared to monocultures, are resilient against disturbances and may mitigate the effects of climate change. Despite well-known benefits, there is still little information on how these forests should be established and managed. The aim of this study was to describe the early growth dynamics of current boreal young mixed stands of planted Norway spruces (Picea abies (L.) Karst.) and naturally regenerated birches (Betula spp.). We collected data from 9  stands planted for spruce 8–14 years ago in Southern and Central Finland. Stem analysis was conducted to 144 spruces and to 144 birches to determine previous growth. We modelled the height and diameter development of individual trees in relation to tree age at stump height using non-linear mixed Chapman-Richards model. There were no significant differences between spruce and seed-origin birch in diameter growth at stump height, but the initial height increments of natural birches were larger than those of planted spruces. However, planted spruces were able to keep up with the height development of birches, if spruces received a head start over naturally regenerated seed-origin birch for two growing seasons. Thus, naturally regenerated birch admixture can be utilized to establish single-storied spruce-birch mixtures, and the admixture should be retained during the early cleaning of planted spruce stands.

• Männistö, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, FI-00790 Helsinki, Finland https://orcid.org/0009-0009-0213-1972 E-mail: lauri.mannisto@luke.fi
• Miina, Natural Resources Institute Finland (Luke), Natural resources, Yliopistokatu 6 B, FI-80100 Joensuu, Finland https://orcid.org/0000-0002-8639-4383 E-mail: jari.miina@luke.fi
• Huuskonen, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, FI-00790 Helsinki, Finland https://orcid.org/0000-0001-8630-3982 E-mail: saija.huuskonen@luke.fi

Uneven-aged forests set certain challenges for cut-to-length harvesting work. It is a challenge to cost-effectively remove larger trees while leaving a healthy understory for regrowth. The study’s aim was to evaluate productivity and costs of harvesting two-storied Silver birch (Betula pendula Roth) and Norway spruce (Picea abies (L.) H. Karst.) stands by creating time consumption models for cutting, and using existing models for forwarding. Damage to the remaining understory spruce was also examined. Four different harvesting methods were used: 1) all dominant birches were cut; 2) half of them thinned and understory was preserved; compared to 3) normal thinning of birch stand without understory; and 4) clear cutting of two-storied stand. Results showed the time needed for birch cutting was 26–30% lower when the understory was not preserved. Pulpwood harvesting of small sized spruces that prevent birch cutting was expensive, especially because of forwarding of small amounts with low timber density on the strip roads. Generally, when taking the cutting and forwarding into account, the unit cost at clear cuttings was lowest, due to lesser limitations on work. It was noted that with increasing removal from 100 to 300 m³ ha^–1, the relative share of initial undamaged spruces after the harvest decreased from 65 to 50% when the aim was to preserve them.  During summertime harvesting, the amount of stem damage was bigger than during winter. In conclusion, two-storied stands are possible to transit to spruce stands by accepting some losses in harvesting productivity and damages on remaining trees.

• Niemistö, Natural Resources Institute Finland (Luke), Natural resources, Kampusranta 9 C, FI-60320 Seinäjoki, Finland https://orcid.org/0000-0002-9152-2108 E-mail: ext.pentti.niemisto@luke.fi
• Korpunen, Norsk institutt for bioøkonomi (NIBIO), Division of Forest and Forest Resources, Department of Forest operations and digitalization, Divisjon for skog og utmark, Avdeling for Driftsteknikk og digitalisering, Høgskoleveien 8, 1433 Ås, Norway https://orcid.org/0000-0001-9749-5684 E-mail: heikki.korpunen@nibio.no
• Nuutinen, Natural Resources Institute Finland (Luke), Production systems, Yliopistokatu 6 B, FI-80100 Joensuu, Finland https://orcid.org/0000-0003-3360-4444 E-mail: yrjo.nuutinen@luke.fi