Catchments

JORG LOFFLER AND OLE ROßLER

University of Oldenburg, Institute of Biology and Environmental Sciences, PO Box 2503, D-26111 Oldenburg, Germany

13.1 INTRODUCTION

Coupled climatologic and hydrologic investigations of high mountain landscapes in Norway are a great challenge, especially where strong meteorological and topographical gradients dominate the boreal altitudinal zones. Human impacts during the past centuries have been important in these types of landscapes, especially involving logging, peat cutting, lichen harvesting for winter fodder and extensive pasturing in the upper birch forest and alpine belts. Besides traditional summer pasture in the mountainous areas, reindeer domestication, especially in northern Norway, has had a broad-scale influence on the mountain environment (Loffler 2000). Its fragility in relation to environmental change and increasing land-use pressure has forced a major focus on high mountains within the discussion of sustainable development (Messerli & Ives 1997). Management of the mountain watersheds has received highest priority with regard to global freshwater resources (Mountain Agenda 1998). Problems and perspectives of Norwegian mountains have been recognised (Bernes 1993, Kaltenborn 1999). Mountains as water towers are important within its highly developed water power industry.

The objectives of the research program reported here are to analyse high mountain ecosystem functioning within different spatial and temporal scales in order to understand the mechanisms that determine the limits of land use. Furthermore, these mechanisms are to be understood within the framework of future global warming. Process-oriented studies have been established to emphasise long-term measurements with the following aims.

- Quantification of vertical and micro-spatial energy and water fluxes

- Process-oriented mapping and spatial modelling

- Analysis of landscape ecological interactions as determined by climate and hydrology

- Synthesising landscape functioning principles that determine the ecology of the high mountain environment.

The most decisive factor in the high mountain landscapes of the Norwegian Scandes is its complex topography determining climatologic and hydrologic gradients, which in turn effect soil development, nutrient fluxes and plant distribution (Kohler et al. 1994). These gradients are complex, and their ecological impact on the high mountain environment is not yet fully understood (Korner 1999). Extensive data are available on high mountain ecology, especially on plant life

Climate and Hydrology in Mountain Areas. Edited by C. de Jong, D. Collins and R. Ranzi © 2005 John Wiley & Sons, Ltd and vegetation organisation, for over a century (Dahl 1998, Wielgolaski 1998, Moen 1999, Wielgolaski 2001). During the 1970s and 1980s, the Norwegian mountains were part of the International Biological Programme, focused on ecosystem functioning at different sites for a global comparative synthesis (Rosswall & Heal 1975, Wielgolaski 1975, Bliss etal. 1981). Local research on spatial dynamics and functioning of alpine ecosystems has been carried out by Mosimann (1985).

Hydrologic investigations with an ecological approach are rare in the Norwegian mountains. On the other hand, many hydro-geological surveys are provided by hydropower development in Norway (Faugli 1994a, 1994b, 1994c, Haland & Faugli 1994 among others). Although early studies dealt with the complexity of mountain environments in Norway (i.e. Dahl 1956), the present scientific challenge is to extend our knowledge on fine-scale temperature and snow cover differentiations as well as gradients between the oceanic and continental regions (Fsgri 1972).

In the Scandes, snow is a decisive factor affecting both hydrologic and ecological systems. Snow-ecosystem studies show that feedbacks between snow, vegetation and climate are complex and occur at multiple scales (Walker et al. 2001). Although the patterns of snow distribution change little from year to year, its amount varies significantly. The most important factor affecting snow accumulation is wind. Strong winds are usually recorded in winter, and this affects both snow depth and distribution as well as its protective role for plants. Snow blown off ridges and windward-exposed slopes accumulates in lee positions, depressions or narrow valleys, where it may last far into the summer. This uneven snow distribution is commonly known as the conservative distribution of snow (Gjffirevoll 1956). Moisture and stability of soils are affected by the distribution and thickness of the snow cover (Dahl 1956). Thus, the combined impact of topography, wind and snow cover has important effects on the high mountain vegetation.

This paper focuses on landscape ecological investigations, especially analyses of spatial and temporal snow dynamics, moisture, and temperature gradients in the central Norwegian high mountains. Interrelations between vegetation cover, periglacial patterns, soil types, humus forms, snow cover thickness, snow-melt and resulting water balance features as well as air, surface, and soil temperature regimes are analysed and mapped in detail (Loffler 1998). Primary results show that the local energy budget is the most important factor for physical, chemical and biotic processes (Loffler 1999, Loffler & Wundram 2001,2003).

13.2 APPROACH

The ''landscape ecological complex analysis'' (Mosimann 1984a, 1984b, 1985), which quantifies landscape processes at the micro scale, is used as a basis for this study. Approaches for ecosystem functioning in different landscapes have been the subject of much discussion (e.g. Leser 1986, Rempfler 1989, Potschin & Wagner 1996, Potschin 1996, 1998, Dobeli 2000).

On the basis of a landscape ecological approach, climatologic and hydrologic coupling is used to explain landscape functioning patterns with a high spatial and temporal resolution. Ecosystem dynamics are analysed over the lower and middle-alpine belts in the continental and oceanic central Norwegian high mountains by means of continuous time series of measurements. Figure 13.1 shows a process-correlation model after Mosimann (1997), integrating the concept of vertical landscape analysis within a seasonal perspective. Water and energy fluxes are regarded as primary interactive processes between different structural compartments of the Norwegian high mountain ecosystem. The most important processes determining input fluxes into the ecosystems are solar radiation and precipitation. The topography with its strong structural elements controls insolation. Resulting heat radiation controls air temperatures, heat flow controls surface and soil temperatures. In combination with wind speed and direction, the relief also controls snow accumulation during the autumn and winter. During spring snow melt, the water equivalent of the snow pack results in a certain amount of surface water. In combination with the infiltration capacity, it affects the entire soil water system, while snow cover isolates against temperatures extremes. Energy and water balance in turn are correlated with different factors of the vegetation, fauna, and soil compartments. The model integrates the cyclicity of seasonal dynamics within the ecosystems.

The process-oriented approach over different spatial scales follows current principles and paradigms in geography (e.g. Haase etal. 1991, Billwitz 1997, Leser 1997, Bastian & Schreiber 1999, Bastian & Steinhardt 2002). The econ concept is used as a basis for extrapolating local point measurements into ecotopes of structural quasi-heterogeneity (Loffler 2002b). In a second step, spatial processes are characterised and structural boundaries mapped in ecotope mosaics. Spatio-temporal characterisations enable a higher level of heterogeneity on the basis of ecochores (Loffler 2002c). Ultimately, the investigations should allow regionalisation of the high mountain landscapes of Norway.

Winter

SuW<-

^^^ Process controller | | Storage

Correlation variable Water flux Energy flux -► Correlation

Double Quantified parameter contour

HF HR

Air Humidity Ascendence Air temperature Evaporation Exposition Fauna Heat flow Heat radiation

Insolation

Air Humidity Ascendence Air temperature Evaporation Exposition Fauna Heat flow Heat radiation

Int In P

PE PR S

Insolation

Infiltration

Inclination

Precipitation

Pot. evaporation

Position in reliet

Soil

Snow cover

WD/WS

Autumn

Soil moisture Soil temperature Solar radiation Soil water

Surface temperature Surface water Vegetation Wind direction/speed

Figure 13.1 Research approach shown as a process-correlation model within a seasonal perspective (Loffler 2002a). The model integrates vertical fluxes of water and energy at a site and uses complex factor constellations determining their intensity and dynamics. Reproduced by permission of Dr Christof Ellger

(a) Econ concept (nano scale)

Precipitation Energy

Evaporation Air heat flow

Percolation Soil heat flow

Evaporation Air heat flow

Percolation Soil heat flow

Atmosphere Hydrosphere

Anthroposphere Zoosphere

Phytosphere

Lithosphere

Ground water formation

(b) Data extrapolation from the econ into the ecotope

Atmosphere Hydrosphere

Anthroposphere Zoosphere

Phytosphere

Pedosphere Geomorphosphere

(c) Ecotope concept (micro scale)

Lithosphere

Ground water formation

(d) Ecochore concept (meso scale)

Pedosphere Geomorphosphere

Temperate ecozone Boreal ecozone: Lowland ecoregions Continental mountain ecoregions Subcontinental mountain ecoregions Suboceanic mountain ecoregions Oceanic mountain ecoregions

Vertical processes within each econ ----►Lateral interactions

(e) Ecoregion concept (macro scale)

Temperate ecozone Boreal ecozone: Lowland ecoregions Continental mountain ecoregions Subcontinental mountain ecoregions Suboceanic mountain ecoregions Oceanic mountain ecoregions

Figure 13.2 shows the different spatial scales and concepts applied for this study. Vertical landscape structure is analysed with the nano-scale. Representative sites are established for field investigations on the basis of larger areas comprising of similar econs. Theoretical considerations concerning the econ concept have to be transposed from the vertical dimension into space. For this, the ecotope concept strictly combines landscape reality and derives its methodical advantages from the econ concept, from which vertical structures and processes are adopted. Larger landscape complexes are regarded as ecotope mosaics. This spatial arrangement of ecotopes is analysed as part of larger landscape units within heterogeneous landscape mosaics. On the meso-scale, landscape complexes are aggregated from a mosaic of ecotopes and result in a completely new emerging spatial unit as the ecochore. Ecotopes are delineated into sub-catchments that are analysed according to their chorological arrangement within a valley system. All those ecotope mosaics assembled within several catchments in turn follow the same landscape ecological functioning principle from the micro scale. Processes of larger extent are the object of investigation. Such processes that correspond between the single ecoregions find their origin within the ecochores, transposed through the spatial level of ecochore mosaics and resulting in characteristic attributes of each ecoregion. Figure 13.2 illustrates the different levels of emergence analyses from the catchment to the altitudinal level, and finally, to the oceanic-continental level of a mountain chain. Ecoregions within Scandinavia are demonstrated as a spatial mosaic of different climatic regions and with superimposed spatial processes. Those processes determine the spatial arrangement of the regions as well as the result of interactions between single regional units. Climatic control and hydrological dynamics within those regional ecosystems are apparent at this macro scale of analysis.

13.3 STUDY SITES

The mountain chain of the Norwegian Scandes has a clearly defined oceanic-continental gradient (Figure 13.3). The western mountain regions are influenced by strong oceanic conditions, and more continental climates are found 100 km to the east. In both regions, the alpine zone can be differentiated into a lower alpine belt, dominated by scrub and heather communities, a middle-alpine belt, dominated by grassy vegetation, and a high alpine belt with vegetation patches in a blocky environment (Dahl 1986). Although little is known about the differentiation of the high mountain climate in Norway, the arid and continental mountain region of Norway Vaga/Oppland (ca. 61° 53'N; 9°15'E) has an annual precipitation of about 300-400mm/a. The alpine environment begins at the tree-line at about 1000-1050m and ends at the highest peak, the Blaho at 1618 m a. s. l. The transition zone between the lower-alpine and the middle-alpine belts lies around 1350m a. s. l. The oceanic mountain region Stranda/More og Romsdal (62°03'N; 7° 15'E) is found in the inner fjords of western Norway and has humid conditions with annual sums of precipitation of about 1500-2000 mm/a. The alpine environment within this western investigation area reaches from the tree-line at about 840-80 m to the highest peak, the Dalsnibba with 1476 m a.s.l. Four representative mountain catchments are chosen for each altitudinal belt (Figure 13.4, Figure 13.5, Table 13.1).

13.4 METHODS

An extensive program of spatial analysis and process measurements was carried out for different landscape ecological parameters within a complex landscape ecological analysis following Mosimann (1984a, 1984b). The methodological concept for high mountain landscape ecological research in Norway was designed for different scales using a hierarchy of models (Figure 13.6).

Figure 13.2 Concept and definition of landscape units at different spatial scales (Loffler 2002a). Figures 13.2(a) modified after Fortescue 1980, (c) and (d) after Leser 1997. Def. ''econ'': ''... a concrete part of the landscape with vertical structure of landscape components. These components are determining characteristic processes between the compartment spheres of the landscape. Thus, an econ is a small delimitable area that has been chosen out of a larger landscape unit serving as a basis for the analysis of vertical landscape structure and functioning. Similar terms are: ''tessera'', ''ecotope holon'', ''landschaftsokologischer Standort'' ...'' (Loffler 2002b). Def. ''ecotope'': "... (gr. "topos": locality) a spatial manifestation of different econs of the same structure and functioning spatially connected with each other. Ecotopes represent the landscape sphere and its related systems of landscape complexes (ecosystems) within the topological dimension (spatial micro scale). They are characterised through concrete structural attributes and size mappable. Processes of vertical landscape functioning are analysed within an econ that is defined as the spatial representative of the ecotope ..." (Loffler 2002c). Further theoretical abstraction of chorological dimension (: gr. ''choros'': ''space'') dealing with heterogeneous landscape complexes leads to the aggregation of mosaics of ecotopes to such completely new spatial units that are analysed as ''ecochores''. Landscape complexes of higher geographical dimension are represented by the theoretical concept of ''ecoregions'' (Loffler 2002c). Reproduced by permission of Dr Christof Ellger

Figure 13.3 Location of the study sites and research design in central Norway (Loffler et al. 2001)
Figure 13.4 Photos of catchments in the lower- and middle-alpine belt of western and eastern Norway (photos from western Norway by R. Pape, from eastern Norway by J. Loffler)

Figure 13.5 Topography of study sites and catchments in the lower and middle-alpine belts (DEM and GIS routines by R. Pape and D. Wundram, field surveys also by O. RoBler and J. Naujok)

Vaga / Oppland, Eastern Norway

Figure 13.5 Topography of study sites and catchments in the lower and middle-alpine belts (DEM and GIS routines by R. Pape and D. Wundram, field surveys also by O. RoBler and J. Naujok)

Table 13.1 Table of the basin characteristics

Catchment 1

Catchment 2

Catchment 3

Catchment 4

Name of the basin/area

Vole

Salknappen

Blafjell

Dalsnibba

Mountain range

Scandes

Scandes

Scandes

Scandes

Elevation range of

1050-1100 m a.s.l

1400-1470 m a.s.l

850-900 m a.s.l

1350-1430 m a.s.l

individual sites

Latitude and longitude

UTM 6862900-507400

UTM 6863200-512400

UTM 6881350-408050

UTM 6880300-409700

Area in km2

0.03

0.038

0.02

0.068

Geology

Mainly phyllit

Mainly phyllit

Mainly gneiss

Mainly gneiss

% glacierized

0

0

0

0

Vegetation type

Lower alpine

Middle alpine

Lower alpine

Middle alpine

(dominant)

% forested

0

0

0

0

Source: Reproduced by permission of Dr Andreas Dittmann.

Source: Reproduced by permission of Dr Andreas Dittmann.

Simulation model X

Landscape ecological prognosis

Model calculation and validiation

Landscape ecological quantification/Balancing

Concept model

Complex site analysis Process mapping Process gradient analysis

Landscape ecological analysis

System model

Site structure analysis Structure complex mapping Structure mosaic mapping ra ol ol c e e œ a

\ Econ concept \ Ecotope concept \ Ecochore concept

Figure 13.6 Methodological concept of high mountain landscape ecological research on different scales using a hierarchy of models for abstraction (Loffler 2002a). Reproduced by permission of Dr Christof Ellger

Single methodological principles were combined within different geographical dimensions. Landscape structures were derived from the theoretical ecosystem model to determine landscape processes. Furthermore, process measurements formed the basis of quantitative models that were to be validated from secondary results. Finally, simulation of landscape ecological processes should allow forecasting future scenarios.

Each catchment was equipped with one ecological base station, several ecological major and minor stations as well as several water level stations. The spatial organisation of measurements and technical equipment strictly followed a spatio-temporal approach for each station (Figure 13.7). They were arranged with the highest possible spatial resolution, the most quantitative measurements, and most cost-effective instruments available. Seasonal ecosystem dynamics was measured throughout the entire year at hourly intervals from a network of permanent stations. Each ecological base station was installed in ridge position. Each four additional data logger stations were located in southern and northern mid slope position as well as in depressions. Data loggers were used to measure air [+200, +100, +15,

+5cm], surface [-1cm] and soil [-5, -15, -30cm] temperatures; precipitation, solar radiation and air humidity [+100cm]; soil moisture [-5, -15, -30cm]; as well as wind direction and wind speed [+200 cm]. Additionally, spatial variability of temperature, soil moisture and wind speed were investigated at various locations. Air temperatures [+200, +100, +15, +5 cm], surface and soil temperatures as well as soil moisture [-1, -5, -15 cm] were investigated using hand-held measurements at 36 sites in each catchment during typical climatic situations (high, low and transitional pressure situations, characteristic wind directions, etc.) over the unfrozen seasons between 1991 and 2003. Soil moisture was measured daily. At well-drained sites, free-draining near-surface percolation lysimeters were used for water and matter balancing. Poorly drained sites consisted of a network of water level stations quantifying the spatial dynamics of stagnation processes. During the winter season, snow accumulation was mapped and quantified by means of snow pack surveys as well as snow property measurements for snow water equivalent. Additionally, snow-melt dynamics was observed by means of colour tracers injected at certain sites and traced by means of

Ecological base station

O Ecological base station

Ecological base station

Evaporation Meter

^ Major ecological station

- Evaporation (15 cm)

' Water level station

- Air Pressure

- Global radiation (1 m)

- Precipitation (1 m,15 cm)

- Evaporation (15 cm)

Low alpine catchment Eastern Norway

Low alpine catchment Eastern Norway

40 m

Permanent vegetation plots

40 m

Permanent vegetation plots

O Minor ecological station

jf^y-r^v«

Figure 13.7 Spatial organization of measurements and use of technical equipment at different types of stations including sensor positions (Photos: R. Pape) (after: Loffler 2002a, Wundram 2003). Reproduced by permission of Dr Andreas Dittmann

Evaporation Meter snow profiles. Spatial data extrapolation was based on a digital elevation model derived from topographic surveys of approx. 1000 points for each catchment.

Spatio-temporal data were fed into a digital database and processed in a GIS. Spatial data layers such as mapped vegetation types, relief, snow cover, and so on, were used to define structural ecotope types. Functional attributes were extrapolated into the ecotope types and spatially correlated with structural information layers (Loffler & Wundram 2001, 2003). Statistically deduced ecological patterns were quantified and generalised for all catchments with respect to scale. Qualitative and quantitative interrelations between the ecosystem compartments were synthesised over high levels of complexity.

13.5 RESULTS OF CLIMATOLOGIC AND HYDROLOGIC COUPLING

13.5.1 Local climatologic and hydrologic dynamics

The meteorological oceanic-continental gradient is sketched by general data (Table 13.2). Annual mean temperatures in the low-alpine west are higher than those of the east, middle-alpine values being similar. Annual maxima are similar in western and eastern low-alpine belts, higher in the eastern middle-alpine belt. Annual minima are lowest in western and eastern low alpine, differences being larger in continental Norway. Summer and autumn minima are similar in the same belts of both regions; the latter slightly lower in eastern middle alpine. Spring maximums are much higher in both altitudinal belts of the west; spring minima are lower in the east, especially in the low-alpine belt. It is shown that temperature dynamics is not strictly explained by principle rules of regional meteorological changes.

Vertical water fluxes are illustrated by four examples from the lower and middle-alpine altitudinal belt in the western and eastern Norwegian high mountain region. Figure 13.8 shows the temporal dynamics of vertical water fluxes.

During the summer months, the eastern Norwegian mountains are characterised by relatively low precipitation. Despite ridge positions are generally the driest localities, a lack of soil moisture during the driest summer period was not measured. Influences of precipitation on soil moisture variability were quite low, since percolation processes were reduced except for intense rainfalls. Moreover, the coarse silty sand with a low field capacity showed volumetric moisture content of20 -30% throughout this dry season. Thus, in the lower alpine belt, upward movement of subsurface water under dense lichen cover even though was extremely retarded, while evaporation rates were high under dry and windy conditions. Evaporation rates were generally high, and sometimes higher than precipitation during rainfall events. Middle-alpine conditions are to be characterised by slightly higher precipitation, lower temperatures and sparse vegetation cover. This constellation led to a more pronounced soil moisture variability, but lower evaporation rates.

Soil moisture was not a limiting factor in the high mountain landscapes during dry summer conditions; for example, competition between plant species resulting in the ecological distribution of phytocoenoses is more dependent on oversupplies of water. Water fluxes on lower alpine ridges were reduced because of the homogenous surface conditions during warm and dry but short summer periods. A dense vegetation layer is important since it isolates high radiation inputs and soil heat fluxes. Summer soil temperatures generally decreased strongly away from the surface at all well-drained sites. Therefore, soil moisture content under vegetation cover was not reduced during dry periods.

Table 13.2 Temperature of western and eastern altitudinal belts (Loffler 2003). Data from western valley and low-alpine stations interpolated by adiabatic coefficient (0.6K/100m) for comparison of same altitude of eastern stations; calculated values used given in brackets. Air temperatures (AirT) from western and eastern valley stations (WestValley, EastValley) and from low and middle-alpine stations (WestLA, WestMA, EastLA, WestMA)

Table 13.2 Temperature of western and eastern altitudinal belts (Loffler 2003). Data from western valley and low-alpine stations interpolated by adiabatic coefficient (0.6K/100m) for comparison of same altitude of eastern stations; calculated values used given in brackets. Air temperatures (AirT) from western and eastern valley stations (WestValley, EastValley) and from low and middle-alpine stations (WestLA, WestMA, EastLA, WestMA)

WestValley

WestLA

WestMA

EastValley

EastLA

EastMA

AirT

AirT

AirT

AirT

AirT

AirT

Annual mean

(3.0) 6.8

(0.7) 1.9

-1.4

1.7

-1.2

-1.9

Annual max

(15.7) 19.5

(16.0) 17.2

12.9

18.2

16.7

15.5

Annual min

(-17.3) -13.5

(-24.6) -23.4

-22.9

-26.8

-29.2

-19.9

Spring max

(10.2) 14.0

(9.7) 10.9

8.5

10.8

7.6

4.9

Spring min

(-3.4) 0.4

(-3.6) -2.4

-9.7

-5.0

-11.1

-11.0

Summer min

(5.5)9.3

(2.4) 3.6

-0.1

4.7

2.3

0.1

Autumn min

(-6.5) -2.7

(-9.1) -7.9

-8.2

-6.9

-10.0

-11.6

Western mountain region

Middle alpine ridge

SG mm 1G mm

Low alpine ridge

1 Month

Soil moisture

Low alpine ridge u

Eastern mountain region

Middle alpine ridge

SG mm 1G mm

SG mm 1G mm

Middle alpine ridge

1 Month

Low alpine ridge

Low alpine ridge

SG mm 1G mm

Precipitation (P) Soil moisture --- Evaporation (E)

1 Month Percolation (Pe) 1 Month

Figure 13.8 Vertical water fluxes in ridge positions of the lower- and middle- alpine altitudinal belt in western and eastern Norway during one representative dry summer month; here: August 2001 (after: Loffler 2002a). Reproduced by permission of Dr Christof Ellger

1 Month

1 Month

Water balance on middle-alpine ridges was dominated by higher water inputs and reduced evaporation rates because of lower temperatures. Direct solar radiation did not intensify soil heat fluxes and soil moisture remained high, although soil evaporation was dominant in sparse and patchy vegetation. On the one hand, high evaporation rates were a result from high air temperatures, low relative humidity and strong wind speeds, a common phenomenon during high-pressure weather situations. On the other hand, high evaporation rates occurred during rainy periods as a result of dry air mass exchange in areas with local convective precipitation. This phenomenon was common in the lower altitude of the alpine belts. Cloud formation and increased precipitation mostly occurred at higher altitudes during such periods. Similar results have been found in high mountain ecosystems of the Alps (de Jong & Ergenzinger 2002).

The western mountain region has higher precipitation totals than those found in continental Norway, and thus the ecosystem dynamics is supposed to be much different (Moen 1999, Loffler 2003). Calling from the measurements lower- and middle-alpine ridge positions were characterised by high soil moisture throughout the driest summer periods. Compared with the eastern mountain ridges, soil moisture was roughly 10% higher in the lower alpine ridge and 20% higher in the middle-alpine ridge positions. Constant rainfall and short periods without precipitation caused highly saturated soils under otherwise unaltered conditions. Percolation was reduced to precipitation events, and since intense rainfall rarely occurred in oceanic summer conditions, percolation amounts were relatively low. High air humidity and cloud cover reduced evaporation substantially; especially under colder middle-alpine conditions. During warm and dry periods, evaporation in the lower alpine regions increased, but absolute rates were permanently lower than those found under continental conditions. The ridge positions are covered by dense lichen heath in the lower and middle-alpine belt, despite high soil moisture and high air humidity. Vegetation distribution in the western high mountains therefore cannot be explained by hydrologic patterns alone. Instead, snow cover conditions determine the spatial arrangement of plant associations. Lichen heath on alpine ridge positions thus corresponds with a thin snow cover during winter. The seasonal dynamics of characteristic air, surface and soil temperatures at different sites in the lower- and middle-alpine belt is very important for ecosystem functioning in the continental to oceanic mountain regions. General principles of vertical temperature dynamics during different seasons are characterised by snow cover influence during winter, exposure to solar radiation in summer and topography relative to soil water saturation during the year (Figure 13.9, Figure 13.10 and Figure 13.11).

Figure 13.9 Vertical temperature profiles at different sites in the lower alpine belt of the eastern Norwegian high mountains 1999. Data are based on long-term investigations with meteorological stations, temperature data loggers and additional manual measurements; curvatures of different profiles are schematic and based on generalisation interpolation in between sensor positions, respectively (Loffler 2002a). Reproduced by permission of Dr Christof Ellger

Continental Eastern Norway, Lower alpine belt

Ground level (cm)

Northern exposure,16° upper mid slope,windward Vaccinium myrtillus lichen heath, well drained soil

Ground level (cm)

Northern exposure,16° upper mid slope,windward Vaccinium myrtillus lichen heath, well drained soil

-300-200-100 00 10o 200 30o Temperature (C)

Ridge position Arctostaphylos uva-ursi lichen heath, well drained soil

Ground level (cm)

-30° -20°-10° 0° 10° 20° 30° Temperature (C)

Ridge position Arctostaphylos uva-ursi lichen heath, well drained soil

-30° -20°-10° 0° 10° 20° 30° Temperature (C)

Depression Sphagnum-Eriophorum mire, not drained

Ground level (cm)

Depression Sphagnum-Eriophorum mire, not drained

-300-200-100 0o 10o 200 30o Temperature (C)

Continental and oceanic lower alpine slopes

Continental and oceanic lower alpine slope sites showed gradual differences with regard to lee- and windward snow pack under similar winter temperature conditions. Average winter temperature profiles remained similar around 0°C. The snow cover isolates against frost and hindered deep soil freezing processes. Freeze-thaw action during spring was possible on northern and southern exposed slopes. Intense solar radiation heated up the ground surface to temperatures comparable to those of the summer but did not effect the deeper layers. On northern exposures, maximum summer air temperatures reached around 20°C under oceanic and 25°C under continental conditions. Therefore, soil temperatures during spring snow melt were identical for both aspects under both conditions. The minimum summer temperature profile showed an inversion. In

Figure 13.10 Vertical temperature profiles at different sites in the lower alpine belt of the western Norwegian high mountains. Data are based on long-term investigations with meteorological stations, temperature data loggers and additional manual measurements; curvatures of different profiles are schematic and based on generalisation interpolation in between sensor positions, respectively. Data for specific events are given as an example of the year 2001

Oceanic Western Norway, Lower alpine belt

Southern exposure, 25° upper mid slope, lee side Vaccinium myrtillus lichen heath, well drained soil

Ground level (cm)

-30o-20o-10o 0o 10o 20o 30oTemperature (C)

Ridge position Rhacomitriuml aguminosum-lichen heath, drained soil

Ground level (cm)

200 100 15

-30o-20o-10o 0o 10o 20o 30oTemperature (C)

Northern exposure,18" upper mid slope, windward Vaccinium myrtillus lichen heath, well drained soil

Ground level (cm)

200 100 15

-30o-20o-10o 0o 10o 20 o 30 o Temperature (C)

Depression Sphagnum-Eriophorum mire, not drained

Ground level (cm)

-30o-20o-10o 0o 10o 20o 30oTemperature (C)

contrast to the oceanic conditions, air temperatures near the ground dropped sharply below 0° C because of night frosts. During summers, the air near the ground, the surface, and the upper soil layers reached highest temperatures on south-facing slopes, but soil temperatures in deeper ground remained identical in both exposures. Highest temperatures were found on continental southerly exposed surfaces, with maximum values above 45°C, while the oceanic southerly slopes reached around 30°C.

Continental and oceanic lower alpine ridges and depressions

Temperature profiles along ridge positions differ from those of well-drained slope sites, even under extreme

Figure 13.11 Vertical temperature profiles at different sites in the middle-alpine belt of the eastern Norwegian high mountains. Data are based on long-term investigations with meteorological stations, temperature data loggers and additional manual measurements; curvatures of different profiles are schematic and based on generalisation interpolation in between sensor positions, respectively. Data for specific events are given as an example of the year 1999 (Loffler 2002a). Reproduced by permission of Dr Christof Ellger

Continental Eastern Norway, Middle alpine belt

Southern exposure,18° upper mid slope, lee side Carex bigelowii snow bed, well drained soil

Ground level (cm)

Southern exposure,18° upper mid slope, lee side Carex bigelowii snow bed, well drained soil

Northern exposure, 24° upper mid slope, windward Cassiope hypnoides snow bed, well drained

Ground level (cm)

200

.i'V'-,.

f

i T

■ i

1

Air

100 -

« 1 i

1

15

i

i

i

CO t

Snow

Ii

*

Vegetation

rn -1 -

i

z

Humus

-5 -15 "

: i

Soil

!

i*

-30

—i—■

■ _

«

[_i_

H-1—

-1-1-1

-300 -200-100 0o 10o 200 30o Temperature (C)

-300 -200-100 0o 10o 200 30o Temperature (C)

Ridge position Cetraria nivalis lichen heath, well drained soil

Ground level (cm)

CO t

Ridge position Cetraria nivalis lichen heath, well drained soil

200 300 Temperature (C)

200 300 Temperature (C)

Depression (anticlinal) Cetraria nivalis-Carex bigelowii lichen heath, poorly drained

Ground level (cm)

-30 -I-1-1 "? -I-1-1-30° -20° -10° 0° 10° 20° 30° Temperature (C)

Depression (anticlinal) Cetraria nivalis-Carex bigelowii lichen heath, poorly drained

-30 -I-1-1 "? -I-1-1-30° -20° -10° 0° 10° 20° 30° Temperature (C)

winter conditions. With deeper snow cover and higher soil moisture, oceanic ridge sites showed little variability of near-ground soil and air temperatures. While extreme annual amplitudes of more than 65 K were experienced under continental conditions, those at oceanic ridge sites reached only around 40 K. Depressions differ from all sites as they remained wet throughout the year and retained a thick snow cover. The examples chosen characterise wet mires with similar vegetation cover in the continental and oceanic mountains and approximately 2 m snow pack during winter. In addition, saturated Sphagnum moss and peat material also isolated against summer overheating, causing gentle soil temperature gradients. Air temperature profiles reflected summer warming effects away from the ground. Overlying air masses sheltered by the pronounced relief caused the stabilisation of warm air layers above cool and wet mire surfaces. Summer minima were lowest during high-pressure temperature inversions. While continental summer minima dropped dramatically below 0°C, oceanic depressions seldom reached the freezing point.

Continental middle-alpine slopes

Middle-alpine slopes were gradually differentiated according to snow melt. North- and south-facing slopes retained equal snow packs and had similar winter temperature profiles. South-facing upper mid-slopes melted out earlier and were thus exposed sooner to summer minimum temperatures while the north-facing slopes remained isolated during this period. Freeze-thaw action during spring occurred on north- and south-facing slopes but did not penetrate far into the ground. Intense solar radiation caused maximum air temperatures in southern as well as northern exposures but did not significantly affect surface and soil temperatures. The uppermost soil temperatures during summer periods remained below 18°C but dropped to 5°C at greater depths. Average summer temperatures are constant at around 5°C.

Continental middle-alpine ridges and depressions

Ridge positions were characterised by highest annual temperature amplitudes near the ground surface. Winter conditions were extreme but negative air temperature was limited near the ground to an average snow layer of 15-20 cm. Summer temperatures were equal to those of the mid-slopes. Depressions in the middle-alpine belt were covered by wet, poorly drained mineral soils. In anticlinal positions, grassy lichen-dominated vegetation types occur where the snow cover was thin during winter. The example had minimum winter temperatures that affected the deeper ground. The deeper mineral soil layer had its average water level at 20-cm depth and was characterised by maximum soil temperatures at 5°C. Summer minima were found in the depressions during temperature inversions, but cold air flows did not last throughout the night as relief gradients allowed air flow down to the lower alpine belt. Nocturnal minima occurred earlier than in the lower alpine depressions and did not show such extreme near-ground air temperatures fluctuations.

13.6 SPATIAL PATTERNS OF CLIMATOLOGIC AND HYDROLOGIC DYNAMICS

Important factors determining hydrologic regimes in different ecotopes include topography, aspect and the winter snow pack. Soil moisture conditions correspond with vegetation cover, humus and top soil layers. Two spatial data sets can be used to illustrate the seasonal dynamics within the water balance: snow cover and soil moisture.

Figure 13.12 gives an impression of snow cover conditions in continental eastern Norway. Lower- and-middle alpine conditions are demonstrated for two catchments. As precipitation increases with height and the snow pack is thicker during winter, it covers the entire catchment in the middle-alpine belt. Here, late snow cover was more persistent in early summer than in the lower alpine belt. The lower alpine catchment in turn was characterised by thick snow accumulations in depressions, but snow-free ridge positions throughout the winter. Lower alpine snow lasted longest in foot-slope positions, but melted out earlier than the middle-alpine snow beds. The snow-free period in summer was short: 13-15 weeks in the lower alpine belt and 11-12 weeks in the middle alpine belt, respectively. Figure 13.13 illustrates the spatio-temporal distribution of snow cover in a lower alpine catchment of the continental mountains. Because of prevailing wind from the north to northwest and high wind speeds during the winter season, the east-west-oriented catchments received lee-side snow accumulation on the southern exposed slopes, where the snow cover melted out in late June. North-facing slopes were characterised by windward snow packs that melted out about three weeks earlier than the latest snow cover in the lower alpine belt. Ridge positions remained more or less snow-free during winter, so that upper slope positions had little snow cover and early snow melt. Depending on surrounding topography, depressions either formed the deepest snow packs or were snow-free because of wind exposure.

Different structural compartments of ecosystems determine the water balance. Besides relief, the mineral fraction of the soil influences the type of water fluxes and soil moisture variability (Figure 13.14). Highly complex vegetation patterns result from the distribution of snow and liquid water. Interactions between landscape structures and hydrologic dynamics were analysed for the lower alpine catchment in the eastern mountain region. Figure 13.14 shows the spatial distribution of substrates. A large proportion of the total catchment area is covered by a dominant glacial till that is up to 100 cm in depth and consists of silty sand and a high coarse fraction. In contrast, ridge positions have a substrate formed by in situ weathering of the phyllitic bedrock and consisting of a coarse-rich sandy silt of up to 30 cm thickness. Locally, a few periglacial block fields occur. The depressions are covered by peat, with a maximum thickness of 160 cm.

Middle alpine catchment

Middle alpine catchment

Figure 13.12 Catchment areas of the lower- and middle-alpine belt and their seasonal dynamics of snow cover and vegetation phenology in continental eastern Norway (Photos by J. Loffler) (Loffler 2002a). Reproduced by permission of Dr Christof Ellger

The mineral substrates are permeable, but organic layers often tend to water logging.

Figure 13.15 shows a map of the distribution of vegetation types in the lower alpine catchment of continental Norway. Ridge positions are covered by lichen heaths. Three different types can be differentiated along a snow gradient of 0 and 30 cm thickness. Alectoria ochroleuca indicates extreme conditions without snow during winter. Cetraria nivalis requires only a thin snow cover of 5 -10 cm, while Cladina stellaris appears where snow extends from 10-30 cm. Those sites that have a thick snow pack that melts in early summer but provides sheltered against late frosts are characterised by shrubs like Betula nana, Vaccinium myrtillus, or Calluna vulgaris. Late snow beds with maximum depths of 400 cm in southern foot-slope locations are characterised by Nardus stricta, which can survive extreme conditions with a wet, warm and short growing season. Depressions show a mosaic of different mire vegetation types along a moisture gradient. Sphagnum - Carex types are found in the wet mires where surface water is to be found throughout the year, while Sphagnum - Eriophorum types with a water table about 0 to 5 cm below the surface. The Sphagnum - Rubus chamaemorus type is characterised by a water level varying between 0 and 15 cm below the surface. All in all, the very fine-scale spatial differentiation of vegetation is the result of a combination of topography, snow cover and ground-water level.

Figure 13.16 illustrates the spatio-temporal variability of soil moisture conditions, directly corresponding with processes such as frost penetration, snow cover and snow melt for the same region. The distribution of different soil moisture profiles showed fine-scale differentiation according to the complex topography. While ridges and convex slopes endured driest conditions throughout the

Wind directions Precipitation at Average wind speeds at different wind directions different wind directions

important are highest wind speeds during winter. Topographical conditions and snow cover were examined by levelling ~1000 during different seasons. Spatial data modelling was based on measurements as well as a digital elevation model and were extrapolated according to their dominant character for the period of 1991-2003. (Snow surveys and maps by D. Wundram and J. Loffler) (Loffler 2003). Reproduced by permission of Dr Andreas Dittmann important are highest wind speeds during winter. Topographical conditions and snow cover were examined by levelling ~1000 during different seasons. Spatial data modelling was based on measurements as well as a digital elevation model and were extrapolated according to their dominant character for the period of 1991-2003. (Snow surveys and maps by D. Wundram and J. Loffler) (Loffler 2003). Reproduced by permission of Dr Andreas Dittmann

In situ substrates

Periglacial substrates

Glacial substrates (till)

In situ substrates

Solid bedrock

Periglacial substrates

Skeleton dominance

Glacial substrates (till)

Skeleton dominance

Weathering layer

Fine material dominance

Fine material dominance

Organic substrates

Lakes and ponds

Figure 13.14 Spatial differentiation of types of ground substrate in the lower alpine catchment (Loffler 1998)

year, soil moisture was constantly high. The interactive hydrologie process was characteristic for the lower alpine belt. Concave profiles tended to be wet and functioned as temporary surface runoff and stagnating ecotopes. Wet conditions were dominant during and after snow melt. However, tracer experiments showed that most of the melt water ran directly downhill over frozen surface, and therefore passed through the entire mountain catchment as surface runoff before penetrating the ground. Thus, the snow pack did not supply a higher volume of water to the ecotopes. Late melting of frozen ground correlated with the availability of liquid water in the soils. This specific process constellation was typical for the water balance of the continental high mountain regions of central Norway. Erratic, high rainfall events characteristically resulted from convective precipitation patterns, but their effect lasted for only hours or days and did not explain permanently high water saturation in the depressions of the catchments.

13.6.1 Spatio-temporal landscape ecological synthesis

By synthesising the principles of landscape functioning according to ecosystem reactions, the results from quantifying procedures are used to explain ecosystem

Figure 13.15 (Plate 9) Spatial differentiation of vegetation types in the lower alpine catchment (Loffler 1998)

Lichens on exposed bedrock

Alectoria ochroleuca - Type Cetraria nivalis - Type Cladonia stellaris -Type

I Cladonia stellaris -I Betula nana -Type

Lichens on exposed bedrock

Lakes and ponds

Nardus stricta - Typ

Alectoria ochroleuca - Type Cetraria nivalis - Type Cladonia stellaris -Type

Betula nana - Type Salix glauca - Type

I Cladonia stellaris -I Betula nana -Type

Vaccinium myrtillus - Type Calluna vulgaris -Type

- Sphagnum spec. - Eriopho-__ rum angustifolium -Type

Sphagnum spec. - Rubus chamaemorus - Type interrelations. For this purpose, a hierarchy of a process-oriented characterisation of ecotopes is defined according to specific landscape functioning attributes. Daily and seasonal air, surface, and soil temperature variations are used to aggregate dynamics of different functional features for each type of structurally delimited ecotope. Differences along spatial and temporal temperature gradients are illustrated in two maps from small catchments in the lower and middle-alpine belt (Figure 13.17 and Figure 13.18). Within this frame, temperature data are classified into seven temperature intervals for spatial ecological interpretation. A legend for each ecotope describes temperature intervals and ecological significance for 13 different landscape ecological parameters. Moreover, temperature attributes show the duration of daily means, duration of frosts, the annual amplitude and the duration of daily maximum (Figure 13.19).

This scaling procedure can directly be adopted to the raw data set to produce the thermoisopleth diagrams.

Figure 13.16 Spatial dynamics of soil moisture (Loffler 2005). Maps are based on spatial surface water measurements by water level stations and soil moisture mapped from hand-held TDR-measurements during different seasons (at ~400 locations). Data are based on long-term field experiments and are generalised according to dominant characteristics for the region since 1991. The classification of soil moisture follows Loffler (1998). Short-term temporal changes in soil moisture conditions are examined by continuous TDR-logger measurements at single sites. Frozen soil conditions are not analysed during winter except on sites with TDR-loggers. The last measurement taken before the winter is representative until springtime. (Measurements modelling and maps by D. Wundram and J. Loffler). Reproduced by permission of Dr Andreas Dittmann

According to the analysis of dominant temperature attributes, the data were also classified for each temperature layer (Table 13.3).

Figure 13.17 and Figure 13.18 show resulting landscape ecological units of temperature dynamics for two examples from the lower- and middle-alpine belt. The primary attribute for the different ecotopes is their topographical position within the catchment. Therefore, a schematic profile along a characteristic relief gradient is illustrated by means of thermoisopleth triples. In conclusion, the figures describe spatio-temporal complexity of high mountain landscape functioning on the ecotope level. They show the pronounced daily air and surface temperature contrasts during the summer period in all ecotope types. Higher soil moisture content leads to less differentiation, while aspect is the most important factor during diurnal variations. High daily summer soil temperature variations are distinct on ridges and southerly exposed slopes but less marked in northern exposure and depressions. Annual variations of the spatial air temperature distribution depend on snow cover thickness and duration of snow cover. Ecotopes with thick snow cover differ from those without snow pack according to the duration of transitional seasons. Spring and autumn air temperature dynamics combined with frost activity and freeze-thaw-processes

j-j Temperature profiles of

Temperature profiles of | | depressions j-j Temperature profiles of

I I southern exposures northern exposures

142 EU-COOl 39

Ecotopes with j-j Temperature profiles of

northern exposures j-j Temperature profiles of

KEx-COOl 20

20 1153 0

122 Ex-COOl 2

Temperature profiles of | | depressions j-j Temperature profiles of

I I southern exposures

Ex-COOl-eu

142 EU-COOl 39

Ex-COOl-eu

Ridge

Upper slOpe

¿12 Mod-cool

49 0

20 m iQfa

^ew Mid stope^

9" MOd-COOl 10

129 Ex-COOl 39

1101Ex-COOl-mOd 4

107 32

Mod-cool

20 m

Linear depressiOn Plain depressiOn

1101Ex-COOl-mOd 4

Mod-cool

Figure 13.17 (Plate 10) Spatial differentiation of temperature dynamics in the lower alpine belt (Loffler & Wundram 2001). A schematic profile along a characteristic relief gradient is illustrated by thermoisopleth diagrams. Legend is given in Figure 13.19 and Table 13.3

Soil

Ex-cold

Per-cold Per-cold

Mod-cold

Mod-cold Mod-cold

Mod-cold

Ex-cold

0 0

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