**7. Microtopographic series**

208 Ecosystems Biodiversity

The field and bottom cover types can be broadly related to the moisture and water table gradient. Dwarf shrubs, Lichen-dwarf shrubs, and Lichen types are well developed on hummock and mound levels of the microtopographic gradient. Graminoid and/or herb, and Graminoid-dwarf shrub are common types of lawns in fens or bogs. Low sedges are in the carpet phases of fens and bogs. Sphagnum occurs widely across the whole wetland gradient, except for frequently flooded sites and strongly shaded sites (trees, dense shrubs). Reeds and tall sedges/graminoids are on shores and frequently flooded locations, often with higher pH and base-richness. Often there is a Sphagnum bottom layer beneath the

There are also general relationships of these Field and bottom cover types with the pH-baserichness gradient. Dwarf shrub and dwarf shrub-lichen tend to have quite low pH-base status and are in bogs or in the bog phase of mixed mires. The sequence tall graminoids, graminoids, and low sedges tend to follow a gradient of high to low pH-base levels. *Sphagnum*-rich sites have a range of species that differentiate both on a moisture-water table gradient and a pHbase richness gradient from rich to poor fen and into ombrogenous bog. Tall reeds and emergents, floating plants, and submerged plants are in water at edges of rivers and lakes, and

To explore relationships of the field and ground layer vegetation with hydrotopographic types we reduced the data set to the six most common Field and bottom types, and the eight

Fewer occurrences than expected

Graminoid/Dwarf shrub, and

shrub, and Sphagnum mosses.

Graminoid/Dwarf shrub, Dwarf

Graminoid/Dwarf shrub, and

Table 5. The relations between the Hydrological mire type and associated Field/bottom

and Sphagnum mosses.

and Sphagnum mosses.

Sphagnum mosses.

Higher occurrences than expected of Field/bottom

Low sedges and Sphagnum

Graminoid/herb, Tall and

Graminoid/dwarf shrub and

Low sedges and Sphagnum

Graminoid/Dwarf shrub and

Dwarf shrub and Sphagnum

Graminoid/Dwarf shrub and

Graminoid/Dwarf shrub, and

layer

mosses.

Low sedges.

Low sedges.

Dwarf shrub.

Dwarf shrub.

Tall sedges.

Graminoid/herb,

mosses.

mosses.

vary from circumneutral to weakly acid and moderate to low base levels.

**6.1 Relationships of Field and bottom cover to Hydrotopographic types** 

of Field/bottom layer

Graminoid/herb,

Dwarf shrub.

and Tall sedges.

**Limnogenous fen** Graminoid/Dwarf shrub, Dwarf

**Sloping fen** Graminoid/herb, Dwarf shrubs

**String flark fen** Graminoid mixtures with Herb

**Flat or weakly raised bog** Graminoid/herb, Tall sedges,

**Mosaic mixed mire** Graminoid/herb, Tall sedges,

**Non-mire wetland** Dwarf shrub, Low sedges and

layers in the dataset, from analyses with Chi-square test.

**String mixed mire** Graminoid/herb,

shrub.

Tall sedges.

dwarf shrub, graminoid, and low sedge types.

Hydrotopographic wetland type

**Flat fen (all types of field/bottom occur)** 

The definition of these types was based upon the microtopographic series - hummock, lawn, carpet, mud-bottom, pool series – introduced by Sjörs (1948) and now used internationally (e.g., Rydin and Jeglum 2006). Seven elements are recognized in the NILS system: Dwarf shrub dominated hummock, lawn, carpet, mud-bottom, flark pool, bog pool, and marsh. (Marsh as described in Rydin and Jeglum, 2006, is very similar to Sumpkarr as described in Allard, 2005). In conducting the photo interpretation, these types together should add up to 100% cover. In the data explored here hummock or lawn were the most common types, and often together totalled 100%. There was a strong inverse correlation between the values for these two types, with a Pearson r value of -0.635, P-Value < 0.0001.

The area data for Microtopographic series in the polygons are given in Table 6, showing that the most common elements are, in decreasing order: Lawn, Hummock, Carpet, and Mudbottom. Flark pool, Bog pool, and Marsh were very infrequent.


\*Small raised mounds usually built-up by Sphagnum and characterized by dwarf shrubs.

Table 6. Estimates of total areas of mires of seven Microtopographic elements, and proportions of the total mire area studied, with standard errors (in parentheses).

Main Ecosystem Characteristics and Distribution of Wetlands

in Boreal and Alpine Landscapes in Northern Sweden Under Climate Change 211

**Flark pools, bog pools**: These are water-covered, and appear very dark to black. They have elongated, crescentic or more or less rounded shapes. Flark pools are the elongated pools in minerogenous fens with unidirectional flow, whereas bog pools are either crescentic or rounded shapes in ombrogenous bogs (Rydin Pers. Comm.). Even though flark pools and bog pools are supposed to be in fens and bogs respectively, sometimes it is difficult to determine positively whether the type in which the pool occurs is a bog or a fen. Hence,

Only one Field/bottom type was assigned to each polygon, whereas the Microtopographic series had a range of seven classes which were given percentages if present in a polygon. Therefore the detail of sampling is greater for the Microtopographic elements. The accuracy of the estimates of covers for different elements should be explored further by conducting assessments of well-mapped wetland polygons, and comparing several photo interpreters. Such exercises are conducted for the staff of NILS as thematic blocks, and are extremely valuable for training and to develop more reliable estimates. This is particularly important because the Microtopographic elements are key attributes in documenting effects of climate change and anthropogenic influences. In addition, it would be of value to define an additional element, i.e., hummock with trees (treed hummock) to allow for documentation of tree

Fig. 6. A portion of a NILS square (yellow lines left and top) in the mid-south of the study area rich in String flark fens. Yellow lines encircle the mapped polygons. The diameter of the circle with the cross hair (centre left) is 20 m. Inside the flark pools can be only water, or water plus mud-bottoms, or only mud-bottoms; therefore flark pools and mud-bottoms could be combined in assessing climate change. In the upper left are some areas in which the unpatterned sedge fens are either very light or medium grey-pink; combinations of lawns

and carpets could be more reliable indicators of climate change.

there may be misidentifications of flark pools (and other fen pools) and bog pools.

We performed a chi-square between Microtopographic series and Hydrotopographic wetland types to determine relationships between the two classifications. Those comparisons of observed and expected with enough values showed some interesting relationships. In Flat or weakly raised bog, Strongly influenced bog, and String mixed mire, hummocks were more abundant than lawns, probably because of more of the raised bog phase in these types. Carpets were more frequent than the mud-bottoms in all the Hydrotopographic types. Flark pools were distributed unevenly, and observed counts were lower than expected in Flat fen, Sloping fen, and Flat or weakly raised bog, but higher than expected in String flark fen and String mixed mire. Clearly the sample method was able to pick up the flark element. Pools were more common than expected in Flat fen whereas Marsh was less common than expected in Flat fen. However, Marsh was more common in Limnogenous fen, just as one would expect along lake and stream margins.

Because it is deemed so important for interpreting climate change to be able to accurately determine the proportions of each Microtopographic element, we give detailed descriptions of the elements which follow and augment the descriptions of Rydin & Jeglum (2006):

**Hummocks** - Hillocks or small mounds with rounded, convex form, usually formed of hummock *Sphagnum* species (e.g. *S. fuscum, S. capillifolium*) rising to ca. 30-60 cm above adjacent hollows. Water tables range from 20-50 cm below the tops of the hummock. Sphagnum may be the main cover viewed from above, without any overtopping vegetation. However, usually the Sphagnum is covered with dwarf shrubs (e.g., *Calluna vulgaris, Ledum palustre, Vaccinium uliginosum*), and sometimes may be partially covered by patches of lichen (e.g., *Cladonia* spp.). With climate warming and lowering of water tables dwarf shrubs and lichens will probably increase, as will sapling and tree cover, on the hummock phase. Hummocks can occur as the dominant microtopographic element in raised bogs, with smaller amounts of hollow types (Rydin & Jeglum, 2006), or they may form raised linear strings or miniature bog islands surrounded by lawns and other wetter elements in patterned bogs, net bogs, and mixed mires.

**Lawns** - Level surfaces covered with fairly dense cover of graminoids (tall sedges, grasses, e.g., *C. lasiocarpa, C. rostrata, Eriophorum vaginatum* ). Most of the time lawns surfaces are 5-20 cm above the water table, but during spring melt and heavy rains water can be at or slightly above the surface. Because of the strong rooting systems of the graminoids, lawns are so firm that footprints rapidly disappear. The moss cover beneath the graminoids is continuous, and lawns seem to have the greatest bryophyte diversity.

**Carpets** - Level surfaces with moderate to sparse cover of low sedges (e.g., *Carex livida, Rhynchospora alba, Scirpus cespitosus)* and Sphagnum and/or brown mosses in the bottom layer*.* Most of the time lawns surfaces are from 5 cm below to 5 cm above water table, but during spring melt and heavy rains water can be more than 5 cm above the surface. The lack of strong graminoid rooting systems makes carpets so soft that a footprint remains visible for a long time.

**Mud-bottoms** – Mud-bottoms are often inundated by water and then are dark to black and hard to separate from the adjacent flark pools or bog ponds. However, in summer drought, mud-bottoms may be exposed bare peat, and may have thin covering of algae, or a gelatinous layer of decomposing peat and microorganisms, or a layer of dark green to black liverwort (e.g., *Cladopodiella fluitans*) with some scattered horizontal shoots of mosses.

We performed a chi-square between Microtopographic series and Hydrotopographic wetland types to determine relationships between the two classifications. Those comparisons of observed and expected with enough values showed some interesting relationships. In Flat or weakly raised bog, Strongly influenced bog, and String mixed mire, hummocks were more abundant than lawns, probably because of more of the raised bog phase in these types. Carpets were more frequent than the mud-bottoms in all the Hydrotopographic types. Flark pools were distributed unevenly, and observed counts were lower than expected in Flat fen, Sloping fen, and Flat or weakly raised bog, but higher than expected in String flark fen and String mixed mire. Clearly the sample method was able to pick up the flark element. Pools were more common than expected in Flat fen whereas Marsh was less common than expected in Flat fen. However, Marsh was more common in

Because it is deemed so important for interpreting climate change to be able to accurately determine the proportions of each Microtopographic element, we give detailed descriptions of the elements which follow and augment the descriptions of Rydin & Jeglum (2006): **Hummocks** - Hillocks or small mounds with rounded, convex form, usually formed of hummock *Sphagnum* species (e.g. *S. fuscum, S. capillifolium*) rising to ca. 30-60 cm above adjacent hollows. Water tables range from 20-50 cm below the tops of the hummock. Sphagnum may be the main cover viewed from above, without any overtopping vegetation. However, usually the Sphagnum is covered with dwarf shrubs (e.g., *Calluna vulgaris, Ledum palustre, Vaccinium uliginosum*), and sometimes may be partially covered by patches of lichen (e.g., *Cladonia* spp.). With climate warming and lowering of water tables dwarf shrubs and lichens will probably increase, as will sapling and tree cover, on the hummock phase. Hummocks can occur as the dominant microtopographic element in raised bogs, with smaller amounts of hollow types (Rydin & Jeglum, 2006), or they may form raised linear strings or miniature bog islands surrounded by lawns and other wetter elements in

**Lawns** - Level surfaces covered with fairly dense cover of graminoids (tall sedges, grasses, e.g., *C. lasiocarpa, C. rostrata, Eriophorum vaginatum* ). Most of the time lawns surfaces are 5-20 cm above the water table, but during spring melt and heavy rains water can be at or slightly above the surface. Because of the strong rooting systems of the graminoids, lawns are so firm that footprints rapidly disappear. The moss cover beneath the graminoids is

**Carpets** - Level surfaces with moderate to sparse cover of low sedges (e.g., *Carex livida, Rhynchospora alba, Scirpus cespitosus)* and Sphagnum and/or brown mosses in the bottom layer*.* Most of the time lawns surfaces are from 5 cm below to 5 cm above water table, but during spring melt and heavy rains water can be more than 5 cm above the surface. The lack of strong graminoid rooting systems makes carpets so soft that a footprint remains visible

**Mud-bottoms** – Mud-bottoms are often inundated by water and then are dark to black and hard to separate from the adjacent flark pools or bog ponds. However, in summer drought, mud-bottoms may be exposed bare peat, and may have thin covering of algae, or a gelatinous layer of decomposing peat and microorganisms, or a layer of dark green to black liverwort (e.g., *Cladopodiella fluitans*) with some scattered horizontal shoots of

continuous, and lawns seem to have the greatest bryophyte diversity.

Limnogenous fen, just as one would expect along lake and stream margins.

patterned bogs, net bogs, and mixed mires.

for a long time.

mosses.

**Flark pools, bog pools**: These are water-covered, and appear very dark to black. They have elongated, crescentic or more or less rounded shapes. Flark pools are the elongated pools in minerogenous fens with unidirectional flow, whereas bog pools are either crescentic or rounded shapes in ombrogenous bogs (Rydin Pers. Comm.). Even though flark pools and bog pools are supposed to be in fens and bogs respectively, sometimes it is difficult to determine positively whether the type in which the pool occurs is a bog or a fen. Hence, there may be misidentifications of flark pools (and other fen pools) and bog pools.

Only one Field/bottom type was assigned to each polygon, whereas the Microtopographic series had a range of seven classes which were given percentages if present in a polygon. Therefore the detail of sampling is greater for the Microtopographic elements. The accuracy of the estimates of covers for different elements should be explored further by conducting assessments of well-mapped wetland polygons, and comparing several photo interpreters. Such exercises are conducted for the staff of NILS as thematic blocks, and are extremely valuable for training and to develop more reliable estimates. This is particularly important because the Microtopographic elements are key attributes in documenting effects of climate change and anthropogenic influences. In addition, it would be of value to define an additional element, i.e., hummock with trees (treed hummock) to allow for documentation of tree

Fig. 6. A portion of a NILS square (yellow lines left and top) in the mid-south of the study area rich in String flark fens. Yellow lines encircle the mapped polygons. The diameter of the circle with the cross hair (centre left) is 20 m. Inside the flark pools can be only water, or water plus mud-bottoms, or only mud-bottoms; therefore flark pools and mud-bottoms could be combined in assessing climate change. In the upper left are some areas in which the unpatterned sedge fens are either very light or medium grey-pink; combinations of lawns and carpets could be more reliable indicators of climate change.

Main Ecosystem Characteristics and Distribution of Wetlands

Canada, to extend over 100 m from a peripheral ditch.

species such as *S. magellanicum*.

minerogenous waters.

in Boreal and Alpine Landscapes in Northern Sweden Under Climate Change 213

4. **Changes in proportions of Microtopographic elements**: Most of these changes will be owing to the changes in Sphagnum dominance just mentioned. With higher temperatures, increasing evapotranspiration, and lowered water tables, bogs will change in the direction of more hummock and treed hummock vegetation elements. Hummocks with dwarf shrubs will invade into the lawns. Soft carpets may become drier and develop towards lawns, while mud-bottoms may develop towards soft carpets. The area of open water flarks and pools may decrease. The Hydrotopographic types that are transitional between bog and fen such as Flat or weakly raised bog and Weakly raised bog or fen-northern, may develop toward more hummock-preferring Sphagnum and develop a more ombrogenous bog ecosystem, owing to less influence of

5. **Changes owing to drainage:** Drainage effects can be used to predict what will happen with climate warming and drying. Many of the same changes listed under Items 2-4 may occur by lowering water tables. This has and still is occurring extensively owing to forest drainage in Sweden, Finland, and the Russian Federation. Drainage of Flanders Moss in Scotland has shown conversion of most of its previous lawn vegetation to hummock vegetation, and only a little of the carpet and pool vegetation is left in small pockets (Pers. Obs.). Hebda *et al.* (2000) estimated the zone of influence of water table lowering in Burns Bog, a bog on the Fraser River Delta in southern British Columbia,

6. **Expansion of the density and cover of trees into peatlands.** Such expansions are often owing to lowered water tables, best illustrated by the expansion of trees in drained peatlands (e.g., see Fig. 1). Several studies have documented advances of trees and shrubs from the margins into the centres of peatlands (e.g., Hebda et al., 2000; Linderholm and Leine, 2004), and the dying of Sphagnum at the margins by lowered water levels and being covered by forest litter. The NILS monitoring in 5-year intervals

7. **Changes of vegetation and invasive species.** Striking examples are the invasion by bamboo, *Sasa* sp., into drained mires in Japan (Iqbal et al., 2005); and Reed Canary Grass (*Phalaris arundinacea*) into bog owing to marginal flooding by mineral-rich waters (Burns Bog, British Columbia, Canada, Pers. Obs.). With drying of peatland margins in Burns Bog, British Columbia, drier upland forest trees such as *Betula* spp and *Tsuga heterophylla*, shrubs such as *Gaultheria shallon* and *Rubus* spp., other upland herbs, and dry mosses (e.g., feathermosses) have invaded and laid down a forest humus, and this

is ideally suited to recording changes in canopy cover of trees and saplings.

process is progressing toward the centre of the peatland (Hebda et al., 2000). 8. **Decreases in peat depth at the margins of the peatlands, and decreases of total area of peatlands:** This will happen owing to temperature increase and drying, collapse of the peat matrix owing to water loss out of the matrix, and oxidation and decomposition. In the first decade after forest drainage, subsidence of peat may be in the order of 15 to 40 cm (Päivänen & Paavilainen, 1996). National Forest Inventories in Finland over many decades (Keltikangas et al., 1986) suggest that significant areas of shallow-peated sites

have converted to non-peatland with less than 30 cm depth of peat.

They predict that in northern Sweden, hollow species such as *S. balticum* will lose competitive strength relative to hummock species such as *S. fuscum* and southern

encroachment onto peatlands (e.g., Fig. 1). We also suggest that it may be useful in future analyses to combine i) lawn and carpet, and ii) mud-bottom with flark pools (e.g., Fig. 6). These elements individually have low accuracy of estimation, but by combining these pairs we may achieve more accurate and reliable estimations of cover changes.
