Raimo Sutinen

Soil-Driven Timberline of Spruce (Picea abies) in Tanaelv Belt–Lapland Granulite Transition, Finland

Abstract Climate-driven northern limits of cold-hardy conifers, Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.), reach latitude 70°N in Fennoscandia. Spruce timberline is located at significantly lower latitudes than pine timberline, but factors contributing to this exceptional pattern have remained obscure. We assessed soil-water and soil-nutrient regimes across the spruce timberline in Finnish Lapland through the use of terrestrial electromagnetic (EM) measurements. These included soil dielectric permittivity (ϵ), which is positively correlated to soil-water content (θv); gamma radiation (γ), which is negatively correlated to soil-water content (θv); and electrical conductivity (σa), which is a measure of solute content of a soil. The soil EM data were acquired at 15 sites carrying mature (older than 150 yr) stands dominated by either spruce or pine; the sites fall along a 50-km-long transect that crosses the spruce timberline. The correlation and artificial neural network (ANN) analyses revealed that the soil-moisture and solute content were significantly higher in glacial tills of Norway spruce stands compared to those of stands formed by Scots pine. The stands dominated by spruce were associated with mesic-wet and nutrient-rich tills derived from mafic amphibole and hornblende gneisses of the Tanaelv Belt. Dry and nutrient-poor till derived from felsic garnet gneisses of the Lapland Granulite appeared to constitute an edaphic dispersal barrier for Norway spruce.

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.

LiDAR DEM detection and classification of postglacial faults and seismically-induced landforms in Finland: a paleoseismic database

Abstract During the last decades, postglacial faults (PGFs) have been found in northern Fennoscandia, the first fault scarps being discovered in western Finnish Lapland in the 1960s. With LiDAR-based digital elevation models (DEMs), a new and accurate remote sensing mapping methodology has been acquired. It allows the relatively rapid and low-cost detection and mapping of late- or PGFs and, for instance, mapping of landslides from areas where they have not previously been recognized. We describe the approach of the Geological Survey of Finland to the systematic search for (screening) and mapping of PGFs, paleolandslides, and other morphological features of Quaternary deposits related to post- and late-glacial seismic activity in Finland. The observations have been collected and classified into a file geodatabase with ArcGis (© ESRI) using a procedure that includes several steps. We also provide examples from western and northern Finland of how sites of late- and postglacial fault scarps and landslides have been detected and described from LiDAR DEM data.

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.

Central boreal mire plant communities along soil nutrient potential and water content gradients

Peatlands have traditionally been exploited in forestry and agriculture over the boreal region, yet they also provide substantial source of fuel production. The large-scale exploitation of peatlands has raised a concern about the diversity of mire plant communities. We studied composition of mire plant communities along soil nutrient potential and water content gradients, to recognize the areas with the high plant diversity. Soil electrical conductivity (ECb) was measured to characterise soil nutrient regimes and soil dielectric permittivity (DP) the soil (volumetric) water regimes. A total of 115 mire sites were studied in the central boreal region of south-western Finnish Lapland. We found that Ward’s hierarchical cluster analysis produced eight stable ECb and DP clusters with discrete vegetation compositions. On the basis of a locally weighted regression analysis (Loess), Carex dioica L., Comarum palustre L., Equisetum fluviatile L., Menyanthes trifoliata L., and Scorpidium scorpioides (Hedw.) Limpr. were found as indicator species for nutrient-rich regimes as designated by high soil ECb. The soil ECb is a diagnostic measure of plant diversity as ECb > 7 mSm−1 resulted in a considerable increase in species richness. Our classification method, based on electrical measurements, provides a simple way to classify mires and focus detailed research to areas with potentially high conservation value.

Large contribution of boreal upland forest soils to a catchment‐scale CH4 balance in a wet year

Upland forest soils affect the atmospheric methane (CH4) balance, not only through the soil sink but also due to episodic high emissions in wet conditions. We measured methane fluxes and found that during a wet fall the forest soil turned from a CH4 sink into a large source for several months, while the CH4 emissions from a nearby wetland did not increase. When upscaled to the whole catchment area the contribution of forests amounted to 60% of the annual CH4 emission from the wetlands, while in a normal year the forest soil consumes 10% of the wetland emission. The period of high upland soil emission was also captured by the nearby atmospheric concentration measurement station. Since the land cover within the catchment is representative of larger regions, our findings imply that upland forests in the boreal zone constitute an important part in the global CH4 cycle not previously accounted for.

Inter- and intra-seasonal effects of temperature variation on radial growth of alpine treeline Norway spruce

A widely accepted standpoint contends that plant growth near the cold edge of the species range, such as treelines, does not depend on the annual temperature seasonality (i.e. difference between maximum and minimum temperature values) but rather on the warmth of summer season. In contrast to this expectation, we show that the growth of treeline Norway spruce (Picea abies) is well explained by temperature seasonality as a single climatic determinant. To do so, the tree-ring data of spruce trees growing on alpine treeline in Lapland was compared with long climate records. Biennial time-series of temperature seasonality capture both the decadal and abrupt growth fluctuations with a correlation coefficient of r = 0.601. We also show that the archetypal association between summer temperature and treeline tree growth may in fact be by far a more complex relationship than previously thought. Spruce growth appears responsive to late- June (r = 0.494) and mid-July (r = 0.310) temperatures but unresponsive to temperatures during the early July, that is, during the grand period of the tracheid formation. Climatic warming may enhance the treeline spruce growth unless the warming is concentrated on unresponsive interval in the midst of the growing season. Water relations did not play significant role as agents of P. abies growth.

Arctic Soil Hydraulic Conductivity and Soil Type Recognition Based on Aerial Gamma-Ray Spectroscopy and Topographical Data

A central characteristic of soil in the arctic is its load bearing capacity since that property influences forest harvester mobility, flooding dynamics and infrastructure potential. The hydraulic conductivity has the greatest dynamical influence to bearing capacity and hence is essential to measure or estimate. In addition, the arctic soil type information is needed in many cases, e.g. in roads and railways building planning. In this paper we propose a method for hydraulic conductivity estimation via linear regression on aerial gamma-ray spectroscopy and publicly available topographical data with derived elevation based features. The same data is also utilized for the arctic soil type recognition, both logistics regression and nearest neighbor classification results are reported. The classification results for logistic regression resulted in 44.5% prediction performance and 50.5% for 8-nearest neighbor classifier respectively. Linear regression results for estimating the hydraulic conductivity of the soil resulted in C-index value of 0.63. The hydraulic conductivity and soil type estimation results are promising and the proposed topographic elevation features are apparently new for remote sensing community and should also have a wider general interest.

Predicting Water Permeability of the Soil Based on Open Data

Water permeability is a key concept when estimating load bearing capacity, mobility and infrastructure potential of a terrain. Northern sub-arctic areas have rather similar dominant soil types and thus prediction methods successful at Northern Finland may generalize to other arctic areas. In this paper we have predicted water permeability using publicly available natural resource data with regression analysis. The data categories used for regression were: airborne electro-magnetic and radiation, topographic height, national forest inventory data, and peat bog thickness. Various additional features were derived from original data to enable better predictions. The regression performances indicate that the prediction capability exists up to 120 meters from the closest direct measurement points. The results were measured using leave-one-out cross-validation with a dead zone between the training and testing data sets.

Dating of paleolandslides in western Finnish Lapland: Dating of paleolandslides in western Finnish Lapland

The dating of landslide-buried organic materials potentially indicates non-stationary seismicity in northern Finland attributable to the release of lithospheric stresses during and after retreat of the Scandinavian Ice Sheet. The landslide age data reveals three episodes of increased slope instability and formation of landslides, from 9000 to 11 000 cal BP, from 5000 to 6000 cal BP, and from 1000 to 3000 cal BP. While a seismogenic origin cannot be unequivocally established, we interpret that at least the early Holocene episode reflects increased seismic activity in northern Finland in association with late-glacial and postglacial faulting. The foci of slope instabilities changes through time, implying that different segments of the postglacial fault systems were active at different times during the Holocene. We also show that the correlation of landslide ages with the surface roughness and backwall slope is complicated. The morphology of landslide scarps is significantly affected by thickness of glacial sediments, liquefaction during landslide formation, and accumulation of peat upon landslide scars and deposits, and thus, the time-dependent erosional smoothing of the surfaces should be considered as descriptive and non-qualitative. Copyright