Marja Kolström

The influence of climate change on the productivity of Scots pine, Norway spruce, Pendula birch and Pubescent birch in southern and northern Finland

Abstract Model computations for Finland showed that the rising temperature associated with climatic change could increase the yield of Scots pine ( Pinus sylvestris ), Pendula birch ( Betula pendula ) and Pubescent birch ( Betula pubescent ). The yield of these species increased more in northern (66°N) than in southern Finland (62°N), the former site representing southern boreal the latter northern boreal conditions. The productivity of Norway spruce ( Picea abies ) decreased in southern Finland, but increased substantially in northern Finland. The temperature rise associated with climatic change could increase the productivity of the forest ecosystems in northern Finland close to that currently prevailing in southern Finland.

Computations on Frost Damage to Scots Pine Under Climatic Warming in Boreal Conditions

To investigate the risk of frost damage to Scots pine (Pinus sylvestris L.) in northern regions under climatic warming, a submodel for such damage to trees was included in a forest ecosystem model of the gap type. An annual growth multiplier describing the effects of frost was calculated with the help of simulated daily frost hardiness and daily minimum temperature. The annual growth multiplier was used in the main ecosystem model when simulating the development of a tree stand using a time step of one year. Simulations of the growth and development of Scots pine stands in southern Finland (61{degrees} N) under an elevating temperature indicated that climatic warming could increase the risk of frost damage due to premature onset of growth during warm spells in the late winter and early spring. Risk of frost damage implies uncertainty in yield expectations from boreal forest ecosystems in the event of climatic warming. 38 refs., 9 figs., 4 tabs.

Computations on the yield of timber by Scots pine when subjected to varying levels of thinning under a changing climate in southern Finland

Abstract Model computations showed that climatic change in terms of rising temperature could increase the yield of Scots pine ( Pinus sylvestris ) stands in southern Finland (61° N) with a consequent need to shorten the rotation and revise the timing of commercial thinnings to take place earlier than under the current temperature conditions. Hence, under a rising temperature, the total timber yield could increase compared with that under the current temperature condition if the length of rotation is kept the same. The largest increase was obtained when several thinnings at low thinning levels were applied under a slowly rising temperature.

Saproxylic beetles on aspen in commercial forests: a simulation approach to species richness

Abstract European aspen is important in boreal forests because of its rich fauna and flora. In Finnish commercial forests, however, aspen stems—especially large ones—are rare. Alternatives to aspen in managed forests were studied with a decision-support system where biodiversity was assessed according to the number of beetle species. The results showed that large aspen stems maintain the richness of beetle species in a forest. Such stems appear in commercial forests if green-retention trees remain after regeneration cutting.

Modelling the long-term dynamics of populations and communities of trees in boreal forests based on competition for light and nitrogen

Abstract This paper describes an individual-based and spatially explicit model for computing the long-term succession of a population or community of trees and the turnover of carbon and nitrogen in a forested ecosystem. In the model ecosystem trees are located within a simulated plot in a grid of cells that are sufficiently small to contain not more than one tree. Each tree consists of five mass compartments (stem, branches, leaves/needles, coarse roots and fine roots) and has its own area, varying in time, for the acquisition of nitrogen. Each tree competes with its nearest neighbours for light and nitrogen; i.e. growth depends on the limitations on light or nitrogen. The calculation of biomass production is based on the potential biomass increment, obtained by means of an integrating parameter for tree net primary production (NPP) in the form of the maximum possible biological productivity of the leaves/needles. Growth under the limited light and soil nitrogen are calculated, and the smaller of the two is used as the realised growth. The total growth of each tree is allocated to different mass compartments using species-specific proportions related to the age of the tree. The litter cohorts are assumed to decompose to form a pool of soil organic matter (SOM) in a manner that is dependent on climatic conditions and the quality of the litter. The simulated plot has an explicit nitrogen–carbon balance based on the turnover of these in the ecosystem linked to the dynamics of organic matter in the soil. The model, which allows standard forest inventory data to be used as input, has been constructed using an object-oriented approach. Comparison of the output of the model with growth and yield tables shows that the current model provides quite similar time courses for the main tree parameters (height, diameter, basal area, etc.) in the case of Scots pine ( Pinus sylvestris ), Norway spruce ( Picea abies ) and birch ( Betula pendula ) throughout Finland (60–70°N).

Weather based moisture content modelling of harvesting residues in the stand

Harvesting residues collected from the final cuttings of boreal forests are an important source of solid biofuel for energy production in Finland and Sweden. In the Finnish supply chain, the measurement of residues is performed by scales integrated in forwarders. The mass of residues is converted to volume by conversion factors. In this study, weather based models for defining the moisture content of residues were developed and validated. Models were also compared with the currently used fixed tables of conversion factors. The change of the moisture content of residues is complex, and an exact estimation was challenging. However, the model predicting moisture change for three hour periods was found to be the most accurate. The main improvement compared to fixed tables was the lack of a systematic error. It can be assumed that weather based models will give more reliable estimates for the moisture in varying climate conditions and the further development of models should be focused on obtaining more appropriate data from varying drying conditions in different geographical and microclimatological locations.