Size-class structure of the forests of Finland during 1921–2013: a recovery from centuries of exploitation, guided by forest policies

Abstract

Frequency distributions of tree diameters are a powerful tool for analyzing changes of tree populations in large areas. We analyzed the densities and mean volume estimates of trees in different size classes for the Finnish forests over the time-span of the National Forest Inventories (1921-2013). The results display a general increase in trees in all size classes, species group and geographical area, mainly after the 1970s. The densities of medium-and large-sized conifers showed large increases in the southern boreal subzone, spruces even more than pines. Small-to medium-sized pines have increased in the middle and northern boreal subzones. The shifts in growing stock are related to changing land use, resulting from the development of the society. The low quantities of both growing stock and large trees during the 1920s reflect a poor initial state of forests. Several land use forms of the former agriculture-based society were detrimental to forests, including slash and burn agriculture, cattle grazing and tar production. The pressure from alternative land use forms was stronger in southern Finland, where the population density (people per km 2) is much higher. Between 1971 and 2013, the changes in size-class structure can be attributed mainly to intensified silviculture boosted by actions of the Finnish governments, including both legislation and financial support for management activities. Not only the development of growing stock has exceeded expectations, but the increase has also concentrated in the economically valuable trees in the large size classes.

Long-Term Nitrogen and Phosphorus Dynamics in Waters Discharging from Forestry-Drained and Undrained Boreal Peatlands

“…A few previous studies have indicated that the general increase in forest cover and biomass in northern latitudes during recent decades ("greening effect") may be one factor behind increasing organic carbon concentrations in forested streams (Finstad et al, 2016;Nieminen et al, 2021;Škerlep et al, 2019), but ours is the first study showing that the trends in nitrogen concentrations may also correlate positively with the increase in forest biomass. Tree stand volume and latitude are positively correlated; tree stands with higher volume are found in southern rather than northern locations in the Nordic region (Henttonen et al, 2020), thus complicating the interpretation of the results. That is, it is unclear whether the increasing trends are primarily related to tree physicochemical processes, such as evapotranspiration and root exudates, or site locationrelated factors, such as temperature.…”

Models for integrating and identifying the effect of senescence on individual tree survival probability for Norway spruce

“…Norway spruce larger than 50 cm are rarely found in boreal old-growth forests in the Nordic countries (Linder 1998;Siitonen et al 2000;Kuuluvainen et al 2002;Rouvinen and Kuuluvainen 2005). This study's dataset can therefore be regarded as covering the whole age and diameter range from young to oldgrowth stands (Henttonen et al 2020), but not necessarily as a representative sample, because the locations of the experiments and plots were subjectively selected. We found that tree survival did not differ between the used datasets (HARKAS, the Norwegian dataset, and old-growth stands).…”

Forest Area and Structural Variable Estimation in Boreal Forest Using Suomi NPP VIIRS Data and a Sample from VHR Imagery

“…The study area was divided into three south, middle, and north zones which roughly followed the hemi-boreal/south boreal, mid-boreal, and north boreal/forest tundra vegetation zones. Separate models were computed for these zones (Figure 1) [45,46].…”