Marja-Liisa Sutinen

Mechanisms of Frost Survival and Freeze-Damage in Nature

Conifers experience a variety of frost scenarios and associated injuries in their natural range. For example, injury from spring frost is a frequent occurrence throughout the northern range of conifers — injuries are also caused by night frosts during the active growth period, when the tissues are sensitive to even slight freezing temperatures. However, night frosts during early autumn can also cause injuries if the weather conditions have not been favorable to cold acclimation. Although cold acclimated conifers from northern regions can usually tolerate severe freezing temperatures, winter desiccation and decreased cold hardiness due to unseasonable warm spells can cause injuries to conifer tissues during mid-winter and early spring. Thus, there are occasions when even the hardiest conifer species in the northern boreal forests experience injury of some sort.

Effects of emissions from copper‐nickel smelters on the frost hardiness of Finns sylvestris needles in the subarctic region

It has been proposed that freezing injuries play an important role in the forest decline phenomenon. In this study, the effect of emissions from the copper-nickel smelters in Monchegorsk and Nikel-Zapolyarnyi in the Kola Peninsula, south-west Russia, on seasonal changes in the frost hardiness of Pinus sylvestris L. needles were studied. The frost hardiness of current-year needles during autumn, winter, spring and early summer in 1991-1993 was estimated by the electrolyte leakage method and by visual estimation of the proportion of damaged needles at nine sites in Finnish Lapland, at five sites in the vicinity of Monchegorsk and at two sites in Norway, in the vicinity of Nikel. The foliar S, Cu, and Ni concentrations also analysed. There were no significant differences at any time of the year between the frost hardiness of pine needles at the sites in Norway and Finnish Lapland. However, in the winter, the degree of visual damage at -45 °C, the temperature close to the lowest recorded temperature in this area, was slightly higher at the sites near to Nikel than at the sites in Finnish Lapland. In the Kola Peninsula the frost hardiness was consistently lower at the sites located 10 km to the south and 36 km to the south-west of Monchegorsk than at the other sites (48-110 km to the south-west). The differences were greatest in early June, 1991, when frost hardiness was -2 °C and -8°C at the sites closest to Monchegorsk. At the same time, the frost hardiness at the other sites was e.-20 °C. There were slight differences between years, but the trends were the same. A clearly increasing gradient in the S, Cu and Ni concentrations was observed on moving towards the emission point source at Monchegorsk. Highly elevated concentrations were found within 40 km of the smelter. The results suggest that air pollutants from the copper-nickel smelter have predisposed the pines to freezing injuries, rhus contributing to forest decline in the Kola Peninsula.

Cold Hardiness of Scots Pine ( Pinus sylvestris L.)

The natural range of Scots pine (Pinus sylvestris L.) is the widest among the pine species (Mirov 1967). It is found at latitudes from 70°N in northern Scandinavia to about 40°N in the south, in Turkey and Spain, and at longitudes from 10°W in the west, with a small population in Scotland (6°W) to 150°E in the east in Russia (Figure 1). At the eastern end of its range the northern distribution limit shifts south, reaching about 65°N at the Ural mountains. Scots pine typically grows at low altitudes, even close to sea level in western Europe, but the altitude of the growing site increases in more southerly locations. In north-eastern Europe and on the west-Siberian Lowlands the northern limit occasionally follows the southern limit of the permafrost zone (Sokolov et al. 1977). At the southern limit of its distribution in the Caucasus mountains in Turkey Scots pine grows at elevations above 800 m, even as high as 2500 m (Rubner 1960; Sarvas 1964; Boratynski 1991).

Significance of snowpack for root-zone water and temperature cycles in subarctic Lapland.

Abstract Snowmelt timing is a critical factor for tree growth in high latitudes, but threshold conditions with respect to soil moisture availability and soil temperature for the root-zone processes are not well known. We monitored snowpack thickness, air and soil temperature, and water content in the soil, sapwood, and roots of downy birch (Betula pubescens Roth.) in Finnish Lapland through 1999–2003. An extreme cold event in January 1999 (TAIR  =  −49°C) resulted in soil freezing (at 10-cm depth) down to T10  =  −26°C at a snow-free site, but beneath the 50-cm-thick snowpack the soil temperature was T10  =  −0.5°C. Snowmelt water was able to infiltrate partially frozen soil sequences, such that an increase in water content of the soil and birch roots occurred two to six weeks before soil temperatures rose notably above 0°C. The soil T10 reached +0°C a week after the disappearance of snow. The increase in water content of birch trunks was coincidental with the air temperature rises notably above 0°C. The systematic interseasonal pattern of water content in the birch root-trunk system, i.e. high peaks in late winter–early spring and fall, suggests sap flow in downy birch.

Physiological changes in Pinus sylvestris needles during early spring under sub-arctic conditions.

Abstract Physiological condition of yellow and visually green Scots pine (Pinus sylvestris L.) needles was followed in the Finnish sub-arctic during May and June 1996. The five greenest and five yellowest saplings were chosen for needle sampling at weekly intervals. The chlorophyll fluorescence, chlorophyll and water content, fine structure of the mesophyll cells and frost hardiness were determined at weekly intervals. Intracellular, extracellular and cell-membrane resistance were estimated by impedance spectroscopy and the distribution of free and bound water were determined by magnetic resonance imaging for needle samples collected on June 11, 1996. The chlorophyll a and b contents, the ratio between the maximum variable fluorescence and the maximal fluorescence yield (Fv/Fm) and the thickness of the grana stacks were higher in the green than yellow needles during the first three samplings in May. The yellow needles maintained a higher level of freezing-stress resistance compared to the green needles. The recovery of green color was accompanied by an increase in the chlorophyll a and b content, Fv/Fm and the thickening of the grana stacks. The water content was slightly higher in the green than yellow needles in June. The water content still decreased even though the chlorophyll content of yellow needles began to increase and approached that of the green needles. Based on the magnetic resonance imaging, the water was distributed differently and in a more mobile form in the yellow than in the green needles. The extracellular resistance and the cell-membrane resistance were lower in yellow than green needles indicating impaired ability of yellow needles to maintain a high intracellular ion concentration. The results show that the yellow color of needles is an indication of a deeper state of photo-inhibition and slower deacclimation and is not directly related to the desiccation stress.

Geological controls on conifer distributions and their implications for forest management in Finnish Lapland

Abstract Soil water and nutrient regimes of naturally established old-growth conifer stands and those of intensively managed Norway spruce [Picea abies (L.) Karst.] sites were assessed over a range of lithological provinces in Finnish Lapland. Soil dielectric permittivity (ϵ), as a measure of soil water content (θ v) and soil electrical conductivity (σ a), as a measure of soil solute content, were species specific, such that high soil θ v>0.27 cm3cm−3 (ϵ>15) constitutes an edaphic constraint for Scots pine (Pinus sylvestris L.) and low soil solute content (σ a<0.5 mS m−1) is constraining for Norway spruce. The spatial pattern of the soil θ v was temporally stabile, such that intraseasonal and interseasonal soil θ v was significantly higher in silty tills of spruce stands compared to sandy tills of pine stands. Scots pine was the only conifer on tills derived from felsic rocks of Hetta granite (HG) and Lapland granulite (LG). Norway spruce dominated on tills derived from the mafic rocks of Lapland greenstone belt (LGB), but tills of LG and HG constitute a dispersal barrier for spruce. Mechanical site preparation (MSP) with ploughing (Marttiini) was not able to amend soil θ v to meet site requirements of Scots pine at former spruce sites. MSP resulted in significant reduction in soil nutrient content such that untreated control σ a>tilt/shoulder σ a>trench σ a. The results imply that MSP treatments through which cross-contour tracks are created pose a risk to the sustainability of soil quality in Lapland.

Nitrate reductase activity in some subarctic species and UV influence in the foliage of Betula pendula Roth. seedlings

Nitrate reductase (NR) activity was studied in the foliage of five subarctic species: mature trees of European white birch (Betula pubescens Erch. S.S.), Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L. Karst), Ericaceous shrub bilberry (Vaccinium myrtillus L.), naturally growing in a forest, and seed-grown silver birch (Betula pendula Roth.) seedlings in an ultraviolet (UV) exclusion field experiment at the Pallas-Ounastunturi National Park in Finnish Lapland (68 degrees N). Mean NR activity ranged from 0 in bilberry to 1477 (S.D. = 277.7) and 1910 (S.D. = 785.4) nmol g(-1) DW h(-1) in mature trees of European white birch and silver birch seedlings, respectively. Significant differences due to UV exclosure treatments were determined for the NR activity of silver birch seedlings (F = 3.62, P= 0.025*) after three growing seasons (191 days) of UV exclusion. The ambient and control silver birch seedlings had or tended to have higher NR activity than those grown under UV exclusion. No relationship was found between the foliage NR activity and total nitrogen content, which ranged from 0.61 to 1.35% per seedling. The present study suggests large differences in NR activity between the species and the induction of NR activity in silver birch seedlings due to ambient UV radiation.

The chemical response of reindeer summer pasture plants in a subarctic peatland to ultraviolet (UV) radiation

Reindeer management is an important livelihood in northern Fennoscandia. There are about 0.7 million reindeer in Finland, Sweden and Norway and approximately 300,000 calves are born every year. The survival of reindeer is highly dependent on renewable natural resources, or ecological preconditions provided by natural pastures (Helle et al. 1990; Reimers 1997; Kumpula et al. 1998). Summer pastures play a central role in the growth of reindeer. Reindeer calves are born in spring and their growth is most rapid during the first few months of life when they graze on summer pastures. Reindeer are mainly slaughtered during autumn. Most of the slaughtered animals are calves (>70 %), and the productivity of reindeer management and income of reindeer herders is highly dependent on the growth success of the calves during the summer. Body mass and fat stores that reindeer are able to accumulate on the summer pastures significantly affect the condition of reindeer and their survival over winter (Helle et al. 1987; Soppela 2000; Soppela and Nieminen 2002). The diet of reindeer is markedly different between summer and winter. During summer, reindeer feed on green vegetation such as grasses, sedges, shrubs, herbs, and leaves of deciduous trees (Warenberg et al. 1997). This diet has a high content of energy, protein, and minerals (Nieminen and Heiskari 1989; Staaland and Saebo 1993) and it enables rapid growth of reindeer and accumulation of muscle and fat. During autumn and early winter, reindeer gradually change to a diet consisting mainly of lichens and wintergreen parts of shrubs, sedges, and grasses (Warenberg et al. 1997). The main winter feeds in many areas are ground lichens (Cladina spp.; Kumpula 2001). Winter diet has a low content of nitrogen and minerals (Nieminen and Heiskari 1989; Staaland and Saebo 1993; Danell et al. 1994; Storeheier et al. 2002). Lichens

Seasonal changes in soil temperature and snow-cover under different simulated winter conditions: Comparison with frost hardiness of Scots pine (Pinus sylvestris) roots

Abstract Seasonal changes in soil temperature and in the frost hardiness of the roots of adult Scots pine (Pinus sylvestris L.) trees were studied between August 1992 and May 1993 in a pine forest growing on dry heathland soil. The study area is located in Finnish Lapland (67°N, 29°E). Air (2 m above ground) and soil (5 cm depth of mineral soil) temperatures were measured continuously every second hour. The frost hardiness of the roots in the soil (down to 10 cm) was measured by means of the electrolyte-leakage method. The air temperature remained consistently below 0°C after the first week of October. The coldest month was February with a daily average temperature of −10.3°C. Snow accumulation started in the first week of October and reached a depth of 129 cm in April. The temperature in the mineral soil varied between +15.4°C and 0.8°C. The frost-hardiness of the pine roots was at its lowest in September (−6°C), and at its highest in December (−21°C). Soil temperature and precipitation as snow in different winter conditions were simulated using the SOIL model. The simulations show that the insulating effect of the snow cover is crucial for the frost survival of Scots pine roots even during a moderate winter.

Challenges to Adaptation in Northernmost Europe as a Result of Global Climate Change

Global warming will continue, and the Arctic is expectedto warm at twice the global average rate (Intergovern-mental Panel on Climate Change 2007). The most pro-nounced changes will occur during winter with increasedprecipitation, more precipitation falling as rain, and ashorter snow period (Intergovernmental Panel on ClimateChange 2007; Roderfeld et al. 2008). These changes willhave far-reaching consequences for ecosystems and for thepeople dependent on their services and may serve as anindicator of environmental change and an ‘‘early warningsystem’’ for other parts of the world (Arctic Climate ImpactAssessment, Symon et al. 2005). We assessed the likelychanges in the provision of goods and services from naturaland seminatural ecosystems (i.e., excluding urban, indus-trial, and agricultural land) in the Barents region—thenorthern parts of Norway, Sweden, and Finland, andnorthwestern Russia—as a consequence of anticipatedclimate changes during the twenty-first century. Thisregion includes approximately six million people in an areathe size of France, Portugal, Spain, and Germany together,totaling 1.75 million km