PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros 2315

demography, and paleoenviromment on the colorado plateau. Methodologies commonly used to pretreat samples American Antiguity 50, 537–554. are described, in addition to the paleoecological indi- Douglass, A. E. (1935). Dating Pueblo Bonito and other ruins in cator value of a wide selection of botanical/zoologi- the southwest. National Geographic Society Contributed Technical Papers, Pueblo Bonito Series No. 1. Washington. cal macrofossils. Applications of mire and peat Douglass, A. E. (1941). Crossdating in dendrochronology. Journal macrofossil analyses in Holocene environmental of Forestry 39(10), 825–831. reconstructions are reviewed briefly. These include Fritts, H. C. (1976). Tree-Rings and Climate. Academic Press, paleoclimate reconstructions, peatland carbon accu- London. mulation rate studies, and the nature of successional Fritts, H. C. (1991). Reconstructing Large-Scale Climatic Patterns from Tree-Ring Data. University of Arizona Press, Tucson. processes in peatlands. Haury, E. W. (1935). Tree-rings–the archaeologist’s time piece. American Antiquity 1, 98–108. Nash, S. E. (1998). Time for collaboration: A.E. Douglass, archael- Introduction ogists, and the development of tree-ring dating in the American Southwest. Journal of the Southwest 40, 261–305. The potential scope of ‘mire and peat macrofossils’ is Nash, S. E. (1999). Time, Trees, and Prehistory: Tree-Ring Dating enormous given both the substantial range of plant and the Development of North American Archaeology. macrofossils preserved in peat sequences and the University of Utah Press, Salt Lake City. ca. 400 million hectare global extent of peat deposits Parks, J. A., and Dean, J. S. (1990). Tree-ring dating of Balcony House: a chronological architectural, and social interpretation. (Barber and Charman, 2003). Peat is defined as accu- In Balcony House: A History of a cliff Dwelling, Mesa Verde mulated sediment which contains at least 30% dry National Park, Colorado (K. Fiero, Ed.), pp. 91–104. Mesa Verde mass of dead organic material, and mires as peat- Museum Association, Mesa Verde National Park, Colorado. lands where peat is currently being formed. We there- Salzer, M. W. (2000). Dendroclimatology of the San Francisco fore restrict our attention in this chapter to Holocene Peaks Region of Northern Arizona. PhD Dissertation, Geosciences Department, University of Arizona, Tucson. northwest European raised peat bog (ombrotrophic) Stokes, M. A., and Smiley, T. L. (1968). An Introduction to Tree- and fen (minerotrophic peatland) deposits (see Ring Dating. University of Chicago Press, Chicago. Wheeler and Proctor, 2000, for a detailed review of Stuiver, M. (1978). Radiocarbon timescale tested against magnetic peatland terminology), where we have our greatest and other dating methods. Nature 273, 271–274. expertise and experience. In this chapter we discuss Towner, R. H. (1997). The Dendrochronology of the Navajo Pueblitos of Dine´tah. PhD Dissertation, Department of how mire and peat macrofossil analyses have been Anthropology, University of Arizona, Tucson. University used to investigate Quaternary environmental Microfilms, Ann Arbor. change, and the methodologies used to prepare and Towner, R. H. (2003). Defending the Dine´tah. University of Utah analyze the samples. A review of the paleoecological Press, Salt Lake City. indicator value and identification notes of a represen- Towner, R. H., and Dean, J. S. (1992). LA 2298: The oldest Pueblito revisited. Kiva 59, 315–331. tative selection of mire and peat plant macrofossils Van West, C. R. (1994). Modeling prehistoric agricultural produc- forms a major part of this chapter. We include a tivity in southwestern Colorado: A GIS approach. Reports of series of photographic figures as an aid to macrofossil Investigations No. 67. Department of Anthropology. Pullman: identifications. It is certainly not a comprehensive Washington State University. selection, but serves to extend and complement the Webb, G. S. (1983). Tree-rings and Telescopes: The Scientific Career of A.E. Douglass. University of Arizona Press, Tucson. identification keys and photographs/illustrations cur- Windies, T. C., and Ford, D. (1996). The Chaco Wood Project: the rently available. The figures will not only be of value chronometric reappraisal of puoblo Bonito. American to paleoecological analyses of mire and peat macro- Antiquity 61(2), 295–310. fossils in northwest Europe. Some of the species we describe here have also been recovered from peat- lands in southern Que´bec, Canada (Pellerin and Lavoie, 2003); the Western Great Lakes Region, Mire and Peat Macros USA (Booth et al., 2004); Tierra del Fuego, D Mauquoy, University of Aberdeen, Aberdeen, UK Argentina (Mauquoy et al., 2004a); and the East- B Van Geel, Universiteit van Amsterdam, Amsterdam, European Russian Arctic (Va¨liranta et al., 2003). The Netherlands

ª 2007 Elsevier B.V. All rights reserved. Applications Environmental change reconstructions based on mire A range of mire and peat macrofossils which can be and peat macrofossils analyses are limited, in that full found in northwest European peat bog (ombro- plant assemblages cannot be reconstructed and trophic) and fen (minerotrophic peatland) deposits directly compared with detailed neophytosociologi- are illustrated in an extensive series of figures. cal studies. This problem occurs due to the selective 2316 PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros nature of vegetation decomposition in peatlands, pinpoint the best samples possible (above-ground since even decay resistant Sphagnum mosses have macrofossils, preferably free of fungal contamina- different decomposition rates (Johnson and tion) for 14C-dating peat sequences in order to create Damman, 1991). Due to the potential for differential accurate and precise chronologies (Mauquoy et al., preservation and representation of the bog vegeta- 2004b). tion, successional and/or paleoclimate reconstruc- tions produced from subfossil assemblages need to be interpreted cautiously. Furthermore it is not Methods always possible to identify Sphagnum spp. to the lowest taxonomic level, particularly where their Analyses of plant macrofossils in peat deposits stem leaves are absent. Cyperaceous (sedge and requires samples of ca. 5 cm3, and these can be recov- allies) remains are also difficult to identify consis- ered using a 7 or 9 cm diameter ‘Russian’ pattern tently, since in many instances seeds and diagnostic corer, a Wardenaar peat sampler (to a maximum epidermal tissues are simply not present. depth of 1 m), or where peat sections are exposed, Subfossil plant macrofossils preserved in peat sam- 50 (100) 15 10 cm metal boxes can be used. ples have been used to reconstruct Holocene raised Analyses of the field stratigraphy of the peat bog peat bog vegetation succession at microform scales (Barber et al., 1998) is highly desirable prior to tak- (analyses of a single borehole to reconstruct vegeta- ing the master core that will be subjected to detailed tion changes in hummock/hollow microform com- paleoecological analyses. This can be undertaken plexes see van Geel, 1978; van der Molen, 1988; using a 5 cm diameter ‘Russian’ pattern corer (either McMullen et al., 2004) and mesoform scales (trans- 50 or 100 cm length). When sampling a ‘living’ peat ects of boreholes analyzed across single raised peat bog, care should be taken to avoid compression of bogs see Svensson, 1988; Barber et al., 1998; Hughes the surface layers of the peat deposits. Before sub- et al., 2000). The aim of much of this research on sampling, 5 mm of peat from the core should be ombrotrophic (rain-fed) peat bog stratigraphy has trimmed to avoid contamination and only clean been paleoclimate reconstructions, since changes in instruments used to avoid the introduction of ‘mod- bog surface wetness recorded by plant macrofossils ern’ carbon and/or contamination with older or are highly likely to represent changes in precipitation younger macro/microfossils. and temperature (Barber and Charman, 2003; Barber Plant macrofossil samples should be gently boiled et al., 2004). The macrofossil data produced from with 5% KOH (deflocculation to dissolve humic and this research is equally valuable in peatland carbon fulvic acids) and disaggregated. When sieving (on a accumulation rate studies (Oldfield et al., 1997) and 125 or 150 mm sieve) the plant remains must be kept the identification of successional processes in peat- just under the water surface (to avoid too much lands, for example the nature and timing of the fen– damage of delicate subfossils, for example, bog transition (Hughes and Barber, 2004). Applied Sphagnum stems with their stem leaves still paleoecological research using plant macrofossil data attached). Stem leaves can be very important for has provided long-term baseline data for the origin Sphagnum identification, because they can help con- and nature of vegetation changes, which can be used siderably in identification to species level. to guide conservation management in environmen- Macrofossils retained on the sieve are then trans- tally sensitive areas (Chambers et al., 1999). The ferred to a petridish and only enough distilled water nature and timing of recent human disturbance to should be added to float the remains, which are ombrotrophic bogs, for example burning and drai- scanned using a low power (10–50) stereozoom nage, has also been assessed (Pellerin and Lavoie, microscope. Moss leaves, cyperaceous epidermal tis- 2003). Dating peat samples using 14C accelerator sues, and small seeds (Juncus spp.) need to be mass spectrometry has now become the standard mounted onto temporary slides and examined at method, and it offers the possibility of dating high magnifications (100–400). above-ground parts of identified plants, for example, Reference collections are essential in aiding and Sphagnum leaves or fruits of Rhynchospora alba. confirming the identification of mire and peat macro- This is highly advantageous, since cyperaceous roots fossils. Above-ground (leaves, stems, flowers, fruits, and the stem bases and attached lower parts of and seeds) and below-ground (rhizomes and roots) Eriophorum vaginatum leaves can be avoided. parts of peatland plants can be collected during field- These have been shown to be younger (because of work or from a herbarium. The best reference collec- downward growth) than bryophyte fragments in the tion, however, is one derived from fossil remains same 14C-dated stratigraphic levels (Kilian et al., (Grosse-Brauckmann, 1986), where the identifica- 2000). Plant macrofossil expertise can be used to tions have been confirmed by an experienced analyst. PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros 2317

A range of techniques are available to present the hummock and lawn microforms (Lindholm and data. The simplest technique is to use ordinal values, Vasander, 1981). It can extend into wet hollow for example, 1 ¼ rare, 2 ¼ occasional, 3 ¼ frequent, microforms, but does not occur in the wettest loca- 4 ¼ common, and 5 ¼ abundant (Barber, 1981). tions (Jacquemart, 1998). Alternatives to this are to make quantitative esti- mates using volume percentages (see the quadrat Vaccinium oxycoccus (Oxycoccus palustris) and leaf count macrofossil analysis technique widely Growth of Vaccinium oxycoccus (Fig. 2E–G) is opti- adopted by Barber and Charman, 2003) or absolute mal where average groundwater levels are 25–30 cm numbers, calculated as either concentrations (number below the root–stem junction (Gronskis and of objects per unit volume, Janssens, 1983; Booth Snickovskis, 1989). It occurs predominantly in et al., 2004) or influx (based on age–depth models). moist hollow microforms on raised peat bogs All three techniques can be combined to present dif- (Lindholm and Vasander, 1981). ferent macrofossil components from a single peat sequence, for example, mosses, dwarf shrubs, and Drosera cyperaceous roots can be expressed as percentages; bark, wood, and bud scales as ordinal values; and Drosera spp. (Fig. 2I and J) are insectivorous, short- seeds as absolute numbers (Va¨liranta et al., 2003). lived herbaceous perennials of open, oligotrophic bogs. The seeds of Drosera rotundifolia and Drosera anglica are similar but strongly differ in Macrofossil Indicator Value and morphology from Drosera intermedia seeds. Descriptions of Northwest European Mire and Peat Macrofossils Eriophorum vaginatum Calluna vulgaris Eriophorum vaginatum (Fig. 2K–M) can grow over a large range of moisture conditions, and forms a Hammond et al. (1990) investigated the position of dominant component of peat communities that Calluna vulgaris (Fig. 1A–F) in relation to local experience surface water levels in the spring and raised peat bog water tables, and found that it subsequent reduced water levels in the summer occurred under minimum and maximum water (Wein, 1973). Drought conditions are not unduly table depths of 10 cm and 52 cm, respectively, with harmful, as the species can survive due to its deep- 90% of occurrences at 30 cm water table depth. It is rooting habit, since the rhizomes may extend to restricted to drier microforms, because the roots and 60 cm below the surface (Gore and Urquhart, their endomycorrhizas need an aerated layer about 1966). Eriophorum vaginatum is capable of invading 10–20 cm deep (Lindholm and Markkula, 1984). pools, and paleoecological evidence supporting this Erica tetralix observation, has been presented by Barber (1981). Hammond et al. (1990) most frequently encountered Erica tetralix (Fig. 1G–K) can withstand some water- this species in peat with a water table at 24 cm depth, logging under experimental conditions (Bannister, although it had a range spanning 0–28 cm, which 1964). Hammond et al.(1990)investigated the posi- demonstrates its wide tolerance to water table tion of Erica tetralix in relation to local raised peat depth. Økland (1989, 1990) also concluded that it bog water tables and found that it occurred under was ‘ubiquitous and omnipresent’, although it was minimum and maximum water table depths of 5– less common in carpets and low lawn microforms. 52 cm below the surface, with 90% of its occurrences recorded at sites with a 35 cm water table. Eriophorum angustifolium

Empetrum nigrum Godwin and Conway (1939) describe Eriophorum angustifolium (Fig. 3A and B) as a species which Empetrum nigrum (Fig. 1L–O) is intolerant of pro- characteristically colonizes drying pools. In a similar longed waterlogging and is restricted to well-drained manner to Eriophorum vaginatum, the well-pro- hummock microforms on raised peat bogs (Bell and tected stem apex of Eriophorum angustifolium offers Tallis, 1973) and can occur abundantly in mire mar- it a degree of fire resistance (Phillips, 1954). Boatman gins (Økland, 1990). and Tomlinson (1977) and Rodwell (1991) con- firmed its position at the edges of pools (where it Andromeda polifolia can dominate), in permanent shallow pools, and in The highest shoot frequencies of Andromeda polifo- dried-up hollow bottoms, as it can tolerate a range of lia (Fig. 2A–D) occur in raised peat bog low moisture conditions. Van der Molen (1988) noted its 2318 PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros

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Figure 1 (A)–(F) Calluna vulgaris: (A) remains in situ; (B) stem with flower; (C) leaf epidermis; (D) twig without leaves; (E) stem; (F) seed. (G)–(K Erica tetralix: (G) stems and leaves in situ; (H) leaf; (I) leaf epidermis; (J) and (K): seed. (L)–(O) Empetrum nigrum: (L) and (M) leaves; (N) leaf epidermis; (O) seed. PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros 2319

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Figure 2 (A)–(D) Andromeda polifolia: (A) leaves and twig; (B) remains in situ; (C) leaf epidermis; (D) seed. (E)–(G) Vaccinium oxycoccus: (E) stems with leaves; (F) remains in situ; (G) leaf epidermis. (H) Ericales, rootlets. (I) Drosera intermedia, seed; (J) Drosera rotundifolia or D. anglica, seed. (K)–(M) Eriophorum vaginatum: (K) stem and leaf remains; (L) part of stem with some in situ spindles and separate spindles; (M) epidermis. 2320 PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros

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Figure 3 (A) Eriophorum angustifolium, lower parts of stems; (B) Eriophorum spp., seeds. (C)–(F) Rhynchospora alba: (C) leaf; (D) detail of leaf with sheath; (E) leaf epidermis; (F) seeds; (G) Carex rostrata, perigynium and achenes. (H)–(J) Carex cf. limosa: (H) rhizome fragment; (I) and (J) root. (K) Carex sp., root. (L)–(N) Scirpus cespitosus: (L) remains in situ; (M) leaf; (N) leaf epidermis. (O) Cladium mariscus, stem base. (P) Typha sp., seed. PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros 2321 occurrence in hollow microforms, with a mean minerotrophic peatland microforms has also been height above the water table of 8–10 cm. confirmed by Økland (1990) using ordination tech- niques. Casparie (1972) also mentions its presence Rhynchospora alba can indicate slight minerotrophy in subfossil peat Rhynchospora alba (Fig. 3C–F) is a good indicator of samples. Thick layers of Scheuchzeria palustris ‘pre- high-mire water tables as it occurs in low lawns and cursor peat’ can precede the deposition of later at pool margins (Godwin and Conway, 1939). Its Sphagnum-rich levels in peat bog deposits. mean height above the water table appears to be 12–14 cm (van der Molen, 1988). Hammond et al. Menyanthes trifoliata (1990) and Økland (1990) report slightly lower Menyanthes trifoliata (Fig. 4G–I) is an aquatic per- values of 8 cm and 5–7 cm respectively to the water ennial herb that occurs in a range of aquatic meso- table, with the range extending from 0 to 10 cm. trophic/eutrophic/oligotrophic peatland communites, Rodwell (1991) describes the position of where water levels are at or above the ground surface Rhynchospora alba as being confined between low (Hewett, 1964; Godwin, 1975). lawns and the shallower water around pool margins, from where it may, sometimes, extend across smaller mire pools. Potentilla palustris Potentilla palustris (Fig. 4J) grows in fens, wet mea- Carex spp. (Carex rostrata and Carex limosa) dows, and lake margins. These Cyperaceae (Fig. 3G–K) occur in mesotrophic and poor fens, although Carex limosa can also be Myrica gale found in ombrotrophic bog pool communities. Carex spp. macrofossils have been used to identify Myrica gale (Fig. 4K) is a deciduous shrub that the fen/bog transition in UK peatlands (Hughes and chiefly grows on both acidic fens and bogs (marginal Barber, 2004). slopes of raised bogs) over a pH range of 3.8–6.1 (Skene et al., 2000). Scirpus cespitosus (Trichophorum cespitosum) Juncus Scirpus cespitosus (Fig. 3L–N) is typically found on Various Juncus spp. (Fig. 4L–N) occur in wet mea- drier areas of raised and blanket peat bogs (Rodwell dows, along shores and in gradient and pioneer situa- et al., 1991). On the better drained Rand (sloping tions. The plants produce enormous amounts of margins) of raised peat bogs it is frequently recorded seeds. Ko¨ rber-Grohne (1964) made a useful illu- (Godwin, 1975). strated key for Juncus seeds in northwest-European deposits. Cladium mariscus

Cladium mariscus (Fig. 3O) grows in calcium rich Molinia caerulea and nutrient poor, shallow water bodies, for example in fens and swamps. Macrofossils of this sedge have Molinia caerulea (Fig. 5A and B) is a perennial grass been recorded with Phragmites australis to indicate a that has a bimodal pH distribution (pH < 4andpH reedswamp phase (Hughes and Barber, 2003). > 7, Grime et al., 1988) and can grow in both bog or fen sites where total waterlogging is absent (Godwin, Typha angustifolia and Typha latifolia 1975). It is most abundant in sites where there is ground-water movement, good soil aeration during Typha spp. (Fig. 3P) produce enormous quantities of the growing season, and an enriched nutrient supply. wind-dispersed seeds and the presence of low num- It is tolerant of burning (Taylor et al., 2001). bers of seeds does not necessarily indicate its local presence. In combination with the pollen record its local presence in terrestrialization phases becomes Phragmites australis clear (rooting in nutrient-rich substrates). Phragmites australis (Fig. 5C–F) grows in fens, shal- low lakes, salt marshes, and flushed areas of bog Scheuchzeria palustris edges, in low-lying areas intermittently or perma- Scheuchzeria palustris (Fig. 4A–F) grows in perma- nently flooded with shallow or still water (pH range nent standing water or in places where local water for well-grown stands of 5.5–7.5, but can occur tables are high (Moore, 1955; Tallis and Birks, where pH is as low as 3.6, Haslam, 1972). The 1965). Its occurrence in very wet and slightly roots can extend to 100 cm in depth. 2322 PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros

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Figure 4 (A)–(F) Scheuchzeria palustris: (A) rhizomes and leaf remains; (B) rhizome epidermis; (C) leaf epidermis with stoma; (D) and (E) hydathode; (F) seeds. (G)–(I) Menyanthes trifoliata: (G) epidermis; (H) remains in situ; (I) seed. (J) Potentilla palustris, seed. (K) Myrica gale, leaf. (L) Juncus effusus-type, seed; (M) and (N) Juncus articulatus-type, seed. PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros 2323

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Figure 5 (A) and (B) Molinia caerulea: (A) thickened lower stem bases; (B) epidermis. (C)–(F) Phragmites australis: (C) rhizomes; (D) and (E) rhizome epidermis; (F) leaf epidermis with stoma. (G) and (H) Alnus spp.: (G) seeds; (H) remains of female catkin. (I)–(N) Betula spp.: (I) seed; (J) B. nana, female catkin scale; (K) tree birch, female catkin scale; (L) detail of leaf; (M) Betula nana, leaf; (N) Betula sp., periderm. (O) and (P) Populus tremula: (O) catkin bracts; (P) bud scale. 2324 PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros

Tree macrofossils – Alnus glutinosa, Betula zip-connections between the cells. Dark parts with spp., Pinus sylvestris, Populus tremula lighter spots in the epidermis are a characteristic Alnus, Betula, and Pine (Fig. 5G–N; Fig. 6A–D) grow feature. The outer cell layer of the roots show long and short cells, with simple cell structure (no zip- in ‘bog woodland’, and base-rich mires (‘fen carr’). connections). Buds, bud scales, catkin scales, fruits, leaf fragments, and needles of these trees have been recorded in peat Thelypteris palustris profiles (Hannon et al., 2000; Hughes and Barber, 2004), particularly in deposits spanning the fen/bog Thelypteris palustris (Fig. 7G–K) can be an important transition (Hughes et al., 2000). Remains of Populus peat former in Holocene deposits formed under tremula (Fig. 5O and P) often occur in early eutrophic conditions. Often leaf fragments, curved Holocene deposits, for example, in small depressions, ends of leaf axes, roots, and tracheids are preserved indicating stands of Populus on drier soils (van Geel (Grosse-Brauckmann, 1972a). Fern sporangia are et al., 1981). common in Thelypteris peat.

Potamogeton Characeae Seeds of Potamogeton can be identified with the Oospores of Characeae (Fig. 7L) are often numerous study by Aalto (1970), but also leaf remains with in lake deposits, especially when these deposits were their characteristic venation (parallel, with connec- formed in pioneer conditions (inputs of minerogenic tions (Fig. 6E and F)) can be common in lake depos- material). A key for central European charophyte its. oospores and a discussion of their ecology is available (Haas, 1994). Ceratophyllum Gloeotrichia Ceratophyllum spp. (Fig. 6G–I) are underwater root- less perennial plants which occur in nutrient rich Globular colonies consisting of hyaline sheaths of water. Pollen of Ceratophyllum does not preserve, Gloeotrichia-type (Fig. 7M and N) regularly occur in and seeds are quite rare. However, the characteristic shallow freshwater deposits (van Geel et. al., 1989; leaf spines are common in pollen slides and leaf frag- 1994; 1996). Increases of Cyanobacteria can indicate ments with insitu leaf spines can be found in macro- eutrophication (increased phosphorus loading which fossil samples of lake deposits. may cause nitrogen-limited growth conditions). In such conditions Cyanobacteria capable of nitrogen Nymphaeacea fixation can thrive. Gloeotrichia-type was also observed in nutrient-poor pioneer conditions at the Asterosclereids and the suberized basal cells of start of the Late-Glacial period (van Geel et al., 1989). Nymphaeaceae mucilaginous hairs (Fig. 6J–N) are frequently found in pollen slides from lake and pool Sphagnum austinii (Sphagnum imbricatum deposits and indicate their local presence (Pals et al., spp. austinii) 1980). This Sphagnum spp. (Fig. 8A and B) is particularly Trapa natans striking since its hyaline cells possess numerous trans- verse lamellae, which appear to be comb-like (Smith, Water chestnut (Trapa natans)(Fig. 7A) is an annual 2004). The ecology of modern examples of this spe- aquatic plant that grows at a depth of 1–2 m in lakes cies indicates that it is a bryophyte capable of grow- and former river channels with a muddy bottom and ing under relatively xeric conditions. Like other fairly warm water. The fruit has a very hard, rough members of section Sphagnum, it has both inrolled shell with four sharp spines (Fig. 7A shows a spine). cucullate (hooded at the apex) leaves, and grows in a Fossil fruits have been identified by Korhola and compact form with a very close and imbricate Tikkanen (1997), most abundantly in shallow, arrangement of the branch leaves. This serves to eutrophic water, prior to final infilling of lake basins reduce the surface area for evaporation (Flatberg, (Schofield and Bunting, 2005). 1986). Green (1968) experimentally demonstrated its ability to retain water, while Flatberg (1986) con- Equisetum firmed its presence in (high) hummocks. Detailed The above-ground remains of Equisetum fluviatile paleoecological macrofossil analysis undertaken by (Fig. 7B–F) in peat deposits are black, while rhizomes van der Molen and Hoekstra (1988) highlight the and roots are dark-brown. Rhizome epidermis cells ability of this bryophyte to grow under dry mire sur- are long and show a very regular pattern with face conditions in the past. PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros 2325

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Figure 6 (A)–(D) Pinus sylvestris: (A) needles; (B) needle epidermis with stomata; (C) periderm; (D) mycorrhizal roots. (E) and (F) Potamogeton, leaf fragment. (G)–(I) Ceratophyllum: (G) leaf with spines in situ; (H) spine; (I) seed. (J)–(N) Nymphaeaceae: (J) leaf epidermis; (K) leaf fragment with trichosclereids; (L) trichosclereid; (M) Nymphaea, seed; (N) Nymphaea, seed epidermis. 2326 PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros

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Figure 7 (A) Trapa natans, barbed appendage of seed. (B)–(F) Equisetum fluviatile: (B) rhizome epidermis; (C) leaf; (D) and (E) stem diaphragm; (F) root. (G)–(K) Thelypteris palustris: (G) leaf fragment; (H) young fossilized stems with folded leaves; (I) fern sporangium (Thelypteris-type); (J) tracheids; (K) root. (L) Characeae, oospore. (M) and (N) Gloeotrichia-type, colony. (O) Sphagnum peat. PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros 2327

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Figure 8 (A) and (B) Sphagnum austinii (S. imbricatum spp. austinii): (A) leaf; (B) transverse lamellae in hyaline cells. (C)–(F) Sphagnum magellanicum: (C) leaf; (D), (E), and (F) high, middle, and low focus. (G) and (H) Sphagnum papillosum: (H) papillae on cell walls. (I)–(K) Sphagnum palustre: (I) leaf; (J) and (K) dorsal high and low focus. (L)– (N) Sphagnum sect. Cuspidata: (L) leaf, (M) and (N) ventral high and low focus. (O)–(Q) Sphagnum cf. tenellum: (O) leaf; (P) and (Q) ventral high and low focus. (R)–(T): Sphagnum sect. Acutifolia: (R) leaf; (S) and (T) dorsal high and low focus. 2328 PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros

Sphagnum imbricatum spp. austinii does, however, Sphagnum palustre have morphologically distinct ecads or ecophenes, The branch leaves of Sphagnum palustre (Fig. 8I–K) which allow it to grow in both hummocks and are ovate or broadly ovate and the apex has a hood- (low) lawns. The lawn ecad has a lax growth form, shaped tip. The photosynthetic cells are variable in which has been experimentally induced by Green shape and can be either triangular and fully exposed (1968). The ability of Sphagnum imbricatum to on the ventral surface; barrel-shaped and broadly grow under wetter mire surface conditions has been exposed ventrally; or lens-shaped with negligible ven- demonstrated in the fossil record by Casparie (1972), tral exposure (Smith, 2004). This species can be van Geel (1978), and Barber (1981). The disappear- found in mesotrophic marshes, stream sides, and in ance of Sphagnum imbricatum from the stratigraphy wet woodlands. Macrofossils of Sphagnum palustre of British and Irish peatlands has been noted by many in poor fen peat deposits have been identified by paleoecologists (see the review in Mauquoy and Hughes et al. (2000). Barber, 1999). The reasons for the disappearance of Sphagnum imbricatum in northwest European peat deposits are still not clear. It may result from a pos- Sphagnum section Cuspidata sible combination of climatic changes and eutrophi- Species within section Cuspidata (Fig. 8L–N) can be cation (deposition of nutrients bound to soil dust identified by their ovate-to-lanceolate shape, narrow following human disturbance). hyaline cells, and their triangular-to-trapezoidal- shaped photosynthetic cells broadly exposed on the Sphagnum magellanicum dorsal surface. The leaves of Sphagnum cuspidatum Subfossil leaves of Sphagnum magellanicum (Fig. 8 are particularly distinctive, as they may extend to C–F) are readily recognized by their photosynthetic 3.5 mm in length. Section Cuspidata leaves are pre- cells, which are oval and largely enclosed by hyaline dominantly found in pool and low lawn ecotopes, cells (Smith, 2004). Andrus et al. (1983) recorded and are therefore a good indicator of raised mire Sphagnum magellanicum in lawns and low hum- water levels. mocks (25.8 9.5 cm above the spring water table). Hammond (1990) found that 90% of the Sphagnum section Acutifolia occurrences of Sphagnum magellanicum occurred at Leaves from Sphagnum section Acutifolia (Fig. 8R– Ø a water table depth of 24 cm. kland (1990), how- T; Fig. 9A–D) are readily recognized by their ovate- ever, suggests it has a broad habitat niche. The spe- to-narrow ovate branch leaves (Smith, 2004), which cies became dominant in many raised bogs during the are small in Sphagnum fuscum (1.1–1.3 mm in last millennium. length) and Sphagnum capillifolium (0.8–1.4 mm) and rather bigger in Sphagnum subnitens (1.2– Sphagnum papillosum 2.7 mm) and Sphagnum molle (1.4–2.3 mm). All of The internal commissural walls of Sphagnum papil- the species within the section possess triangular losum.(Fig. 8G and H) are rough, since they possess photosynthetic cells broadly exposed on the ventral projecting papillae (Smith, 2004). This distinctive surface and possess similarly sized dorsal pores (up to feature of the hyaline cells makes identification of 30 mm). The overlapping size ranges of the branch Sphagnum papillosum straightforward. Boatman leaves, makes positive identification to species level (1983) found it predominantly in low lawns and difficult (unless stem leaves are present, as these are pools in the Silver Flowe complex of bogs in south- very valuable in aiding identification, see Johansson, west Scotland. Its 10–12 cm mean height above the 1995). water table also suggests an optimal low lawn posi- The difficulty of consistently and accurately iden- tion (Janssens, 1992; van der Molen et al., 1994). tifying leaves to species level also poses problems in Conversely, Hammond et al. (1990) found that determining the degree of mire surface wetness. This 90% of the occurrences of the species were at rela- is not such a problem for both Sphagnum fuscum and tively high positions on lawns (23 cm), just below the Sphagnum capillifolium var. rubellum leaves, since optimum value for Sphagnum magellanicum (24 cm). they occupy hummocks; Andrus et al. (1983) found Økland (1990) made similar findings since it was the two species growing at mean heights of recorded largely in lawn microforms, and only rarely 30.9 10.6 cm and 24.8 9.4 cm above the spring in hummocks as single shoots. This species appears to water table, respectively. Rydin and McDonald have a wide ecotope breadth, like Sphagnum magel- (1985) similarly found the two species at respective lanicum, although its optimum position would heights of 35 cm and 25 cm above the water table, appear to be centered on low lawn positions. while Janssens (1992) derived an optimum height of PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros 2329

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Figure 9 (A)–(D) Sphagnum fuscum (recent): (A) and (B) leaf and stem leaf; (C) and (D) ventral high and low focus. (E) and (F) Sphagnum sect. Subsecunda. (G) and (H) Sphagnum spp., sporangium and operculum. (I) and (J) Aulacomnium palustre, leaf and detail of leaf. (K)–(O) Polytrichum juniperinum/alpestre-type: (K) Polytrichum in situ; (L) leaf; (M) leaf tip; (N) leaf base; (O) detail of leaf base. 2330 PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros

27.5 cm above the mean water table for Sphagnum mesotrophic phase in the local peatland succession fuscum. (Va¨liranta et al., 2003). Sphagnum molle and Sphagnum subnitens are, however, lawn species (Smith, 2004), which reduces Calliergon giganteum the accuracy of any paleoecological reconstruction Calliergon giganteum (Fig. 10G and H) is a moss that made using branch leaves identified to Sphagnum primarily occurs in rich fens. Subfossil leaves of section Acutifolia alone. Calliergon giganteum were identified by van Geel et al. (1986) and used to indicate stagnant, eutrophic, Sphagnum section Subsecunda and base-rich aquatic environments in an Eemian Branch leaves in Sphagnum section Subsecunda lake deposit. (Fig. 9E and F) are typically 0.7–2.5 mm long and Drepanocladus spp. (Fig. 10I and J) 0.4–1.5 mm wide. Numerous small dorsal/ventral pores are present along the commissures (the junction Drepanocladus aduncus is an aquatic moss which between the hyaline and the green cells), with up to occurs in moderate-rich fens, small lakes, ponds, or 40 and 20 per cell, respectively. Species in this section streams. Drepanocladus fluitans is found in pools in can be found in depressions (often submerged), in blanket bogs, sometimes with Sphagnum cuspida- base-rich flushes, fens, woods, and moors. tum. Watson (1968) describes it as a species that can tolerate both aquatic and terrestrial habitats, Aulacomnium palustre since it is found in both deep pools and sites which are only periodically wet. Dickson (1973), however, The leaf cells of Aulacomnium palustre (Fig. 9I and J) places Drepanocladus fluitans as a species primarily have rounded lumens. This moss grows at relatively found in base-poor pools. Ohlson and Malmer high positions above the water table, for example (1990) corroborate this, as they recorded Andrus et al. (1983) recorded it at positions 30.0– Dreplanocladus fluitans with Rhynchospora alba 31.4 cm above the spring water table, in small growing in mud-bottom communities. patches on hummock sides. Økland (1990) similarly confirms the presence of this species within upper Fungi hummocks and, additionally, as ‘single shoots’ Fungal fruit bodies (ca. 125–500 mm in diameter) are among Sphagnum species. Nicholson and Gignac regularly recorded in raised bog macrofossil samples (1995) found it growing at a greater range of heights (van Geel, 1978). The dark-brown fruit bodies are above the water table (10–40 cm). often still filled with ascospores. Meliola ellisii (Fig. 11B) is an obligate parasite on Calluna vulgaris. Polytrichum commune and Polytrichum juniperinum/alpestre-type The currently unidentified Type 18 (Fig. 11A) occurs on roots of Eriophorum vaginatum. Mycelium with Polytrichum commune (Fig. 10A–C) grows under a chlamydospores of Glomus cf. fasciculatum wide range of acidic habitats, including heaths, (Fig. 11C) can be common in various types of (non- woods, wet moorlands, bogs, lake margins, pools, oligotrophic) peat deposits. It grows as a vesicular- and stream sides in damp-to-wet microhabitats. It is arbuscular endomycorrhizal fungus on a variety of commonly associated with a range of Sphagnum host plants. In lake sediments the presence of Glomus spp., especially Sphagnum palustre and Sphagnum indicates soil erosion in the catchment of the lake recurvum. Polytrichum juniperinum (Fig. 9K–O) (Anderson et al., 1984). grows on well-drained acidic soils on heaths and moors (Smith, 2004; Dickson, 1973). Polytrichum Freshwater sponges alpestre similarly displays a preference for drier Spicules and gemmules of freshwater sponges (Fig. 11E microforms and has been interpreted as a hum- and F) are of regular occurrence in macrofossil sam- mock-level moss (Hughes et al., 2000), since it ples; especially in shallow water deposits at transitions forms dense tussocks on ombrotrophic bogs from open water in the first stage of terrestrialization (Dickson, 1973). (Harrison, 1988; van Geel et al., 1989). Paludella squarrosa Chironomidae and Trichoptera Paludella squarrosa (Fig. 10D–F) is a moss that The chitinous larval remains of chironomids (Fig. 11G occurs in fens and subfossil leaves identified in a and H) are very useful in paleoenvironmental studies peat profile collected from the east-European of lake sediments (Walker, 2001). For the use of caddis Russian Arctic have been used to show a wet and fly larvas remains we refer to Elias (2001). PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros 2331

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Figure 10 (A)–(C) Polytrichum commune: (A) leaf; (B) detail of leaf with lamellae; (C) leaf base. (D)–(F) Paludella squarrosa; (G) and (H) Calliergon giganteum; (I) and (J) Drepanocladus cf. aduncus. 2332 PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros

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Figure 11 (A) Fungal fruit body (Type 18; not identified) in roots of cf. Eriophorum vaginatum. (B) Meliola ellisii, fruit body with ascospores. (C) Glomus, mycelium with chlamydospores. (D) mycorrhiza tissue (Cenococcum geophilum?) on root tips (not preserved). (E) and (F) Freshwater sponge, gemmule. (G) Chironomid, larval head capsule. (H) Trichoptera, membrane of pupal case. (I) Acari, Oribatida. (J) Piscicola geometra, cocoon. (K)–(M) Bryozoa statoblasts: (K) Plumatella-type; (L) Lophopus crystallinus; (M) Cristatella mucedo. (N) Foraminifera. (O) Ostracod. (P) Callidina angusticollis, lorica. (Q) Diaptomus castor, egg sac. (R) Bithynia, operculum. PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros 2333

Acari (oribatid mites) Conclusions The majority of oribatid mites (Fig. 11I) have a scler- High-quality macrofossil datasets from peat depos- otinized, chitin-rich cuticle. They are soil dwellers, its can be used to reconstruct the former degree of common in peat deposits, but normally no records mire surface wetness, successional processes of are made and for identifications specialist literature the local peat-forming vegetation, trophic/pH and the help of an acarologist is essential (Schelvis status, and assess the effect of human disturbance and van Geel, 1989). For an overview of the potential (e.g., burning, drainage, and rapid forest use of mites in paleoecology see Solhøy (2001). expansion)(Pellerin and Lavoie, 2003). A thorough knowledge of the present-day ecology of the plants Piscicola geometra growing in bogs and fens is essential in order to make accurate paleoenvironmental reconstructions, Piscicola geometra (Fig. 11J) is an external parasite and provides the basis for evaluating the subfossil of freshwater fish. They lay their eggs in cocoons on presence of these plants (the individualistic the pond bottom, plants, stones, etc. Cocoons can be approach, Birks and Birks, 2003). We have, there- common in lake deposits (Pals et al., 1980). fore, compiled and reviewed a selection of literature on the actuo- and paleoecology of peat-forming Bryozoa plants to guide the interpretation of subfossil peat Bryozoa (Fig. 11K–M) are small, sessile, colonial, sequences. Identifications of mire and peat macro- filter-feeding animals. There are more than 65 fresh- fossils can often be made to species level, and is the water species worldwide. Bryozoa of the class key advantage of the technique compared to pollen Phylactolaemata produce asexual buds called stato- analysis, since grains and spores are usually only blasts. These consist of two chitinous valves with identifiable to family or genus level and may come regenerative cells within, and function as reproduc- from a variety of habitats outside the peat-forming tive, survival, and dispersal agents. Statoblasts can be wetland. Our illustrations of a range of mire and identified and provide information on past aquatic peat macrofossils may help to identify remains of environments (Francis, 2001). peat-forming plants, but we stress that type mate- rial (preferably fossil) is the best way to confirm Foraminiferae correct identifications.

In peat deposits and lake sediments, the presence of See also: Plant Macrofossil Introduction. Plant linings of foraminiferae (Fig. 11N) indicate tempor- Macrofossil Methods and Studies: Peatland Records of ary inundation with salt or brackish water. Holocene Climate change; Validation of Pollen Studies. Pollen Methods and Studies: Reconstructing Past Ostracods Biodiversity Development. Ostracods (Fig. 11O) are bivalved aquatic crusta- ceans with shells, common in nonmarine waters with neutral-to-alkaline pH. Ostracods are sensitive References to a range of ecological factors (Holmes, 2001). Aalto, M. (1970). Potamogetonaceae fruits. 1. Recent and subfossil endocarps of Fennoscandian species. Acta Botanica Fennica 88, Callidina angusticollis 1–55. Aerts, R., Walle´n, B., and Malmer, N. (1992). Growth limiting The loricas of Callidina angusticollis (Fig. 11P) are of nutrients in Sphagnum dominated bogs subject to low and high regular occurrence in Holocene raised bog deposits, atmospheric nitrogen supply. Journal of Ecology 80, 131–140. but to date no specific ecological information can be Anderberg, A. L. (1994). Atlas of seeds and small fruits of derived from the occurrence of this representative of Northwest European plant species with morphological descrip- tions. Part 4 Resedaceae-Umbelliferae. Swedish Museum of the Rotifera (van Geel, 1978). Natural History, Stockholm. Risbergs Tryckeri, Uddevalla. Anderson, R. S., Homola, R. L., Davis, R. B., and Jacobson, G. L. Diaptomus cf. castor (1984). Fossil remains of the mycorrhizal fungal Glomus fasci- culatum complex in postglacial lake sediments from Maine. According to Bennike (1998) the egg sacs of Canadian Journal of Botany 62, 2325–2328. Diaptomus cf. castor (Fig. 11Q) might indicate low Andrus, R. E., Wagner, D. J., and Titus, J. E. (1983). Vertical arctic or subarctic climates, but that idea must be zonation of Sphagnum mosses along hummock-hollow gradi- ents. Canadian Journal of Botany 61, 3128–3139. incorrect, as van Dam et al. (1988) recorded them Barber, K. E. (1981). Peat stratigraphy and climatic change: a from late Holocene moorland pool deposits in The palaeoecological test of the theory of cyclic peat bog regenera- Netherlands. tion. Balkema, Rotterdam. 2334 PLANT MACROFOSSIL METHODS AND STUDIES/Mire and Peat Macros

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