The dynamics of peat accumulation on bogs: mass balance of hummocks and hollows and its variation throughout a millennium

This study concerns the mass balance in hummocks and hollows on three ombrotrophic boreonemoral bogs in both a short (ca 10 yr) and long (1000 yr) time scale. Nitrogen, ¹⁴C. and ^?210Pb are used to establish detailed time scales and to estimate productivity and decay losses in tour different microtopographical units: hummocks with either Sphagnum or lichens and hollows with either Sphagnum lawns or bare hollows. The accumulation of N and ²¹⁰Pb was greater in hummocks than in hollows. The litter input was higher in Sphagnum hummocks (170-210 g m^?2yr^?1) than in lawns (110-145 g m ^?2- yr^?1) while its decay rate (0.011 -0.014 yr^?1) did not differ. The arotelm was deeper in Sphagnum hummocks than in lawns but because of less compaction in lawns, neither residence time (80 100 yr) nor decay losses (70-75%) differed. Productivity in lichen hummocks and bare hollows was insignificant and the mass balance negative. It is concluded that the higher productivity in Sphugnum hummocks maintains the microtopography on the mire surface. The mass balance in hummocks will determine not only the development in hollows but also the rise of the ground water mound, and the height increment of a bog. The addition of mass to the catotelm has generally been less in hollows than in hummocks. Since 800 BP the overall input to the catotelm has decreased from about 150 to < 50 g m ^?2 yr^?1 due to longer residence time increasing losses through decay in the acrotelm from < 20% to 70% and is the result of either climatic changes or autogenic processes in the bog ecosystem. Before recent centuries the whole bog surface must have been covered with Sphagnum mosses, forming an overall input of litter as large as in the recent Sphagnum hummocks and lawns. Due to the present lesser cover of peat forming mosses (20-50% of the surface), the recent overall input of peat-forming litter is only 50-65 g m^?2 yr^?1. The bogs no longer act as sinks for carbon since the input of carbon only just covers the losses as CH₄ and CO₂.     

Ecological Succession of a Relict Central European Peat Bog and Variability of Its Insect Biodiversity

The isolated habitat of the ervené Blato bog (South Bohemia, Czech Republic) and its relict insect fauna have been the subject of long-term monitoring. The species composition and abundance of Lepidoptera (light traps) and Coleoptera (pitfall traps) were monitored for 4 years (1994–1997) simultaneously on two sites – in the edaphic climax pine forest and in wetland successional habitats. The method of statistical evaluation by RDA and CCA ordination, representing the habitat preference of species of Coleoptera (Carabidae only) and Lepidoptera (all nocturnal phototactic taxa) between the edaphic climax forest and succession stages, was used. All categories of the peatland taxa (tyrphobiontic, tyrphophilous and tyrphoneutral species) were analysed. Ten highly stenotopic tyrphobiontic species and 23 tyrphophilous species of Lepidoptera (out of 487) were most characteristic of the bog habitat. Only two tyrphophilous carabid species (out of 20) were characteristic of the bog. The most important relict species (tyrphobionts) of Lepidoptera are most diverse and abundant within the successional habitats and in the open wet forest. The relict fauna of the closed climax pine forest is much less diverse and composed mostly of abundant tyrphophilous and tyrphoneutral forest species. Preservation or restoration of sufficiently constant hydrological conditions, which prevents formation of the closed forest, is the basic management for habitat conservation of all relict tyrphobiontic species of the ervené Blato bog and similar peat land habitat islands. The peat bog is a unified complex system of specific diverse and relict taxa. The most specific taxa are tyrphobiontic Lepidoptera, but a number of other vulnerable tyrphophilous and tyrphoneutral insects are associated with the peat bog as well.     

Spatial distribution of insect indicator taxa as a basis for peat bog conservation planning

Peat bogs are highly endangered ecosystems worldwide. In the Western Balkans, they represent fragmented habitat patches, where insect diversity and implications for the habitat loss are poorly known. Carabid beetles and ants, widely used environmental indicators, were sampled by pitfall trapping in the largest and oldest Croatian peat bog and at its edges. We found that tyrphobiontic—bog specialist—species were absent in both taxonomic groups, which is likely due to biogeographical limitation for dispersal of these species into this region. With this study, tyrphophilous—typical of bogs—species have been recognised as environmental indicators in the Western Balkans peat bogs. Assemblages of both taxa were strongly affected by specific conditions in the peat bog – high soil moisture and Sphagnum moss dominance, showing that edges are more favourable habitats for both taxa. Overall, carabid beetle activity density was significantly higher at the edge than at the peat bog, while species richness increased for both taxa at the edge, but not significantly. Spatial distribution of tyrphophilous species differed between studied taxa, with ants being more abundant in the peat bog, and carabid beetles at the edge. Additionally, some stenotopic and globally endangered species preferred edges. Occurrence of tyrphophilous and globally endangered species highlights the great conservation value of peat bog habitats in the Western Balkans. However, successional changes in vegetation are changing hydrological conditions of the peat bog. Here we suggest active conservation measures to preserve these unique soil invertebrate zoocoenoses.     

On the significance of structural vegetation elements for caterpillar thermoregulation in two peat bog butterflies: Boloria eunomia and B. aquilonaris

Purpose

Temperature profoundly impacts on distribution and habitat-use of organisms. The development of ectothermous caterpillars does not depend on host plant quality only, but also on the availability of suitable thermal conditions. Selection for thermally favorable microclimates (i.e. behavioral thermoregulation) is a primary mechanism of temperature control, and caterpillars can be either (or alternately) temperature conformers (i.e. passively adopting ambient temperature conditions) or thermoregulators (i.e. able to some extent to elevate or decrease their body temperature relative to ambient temperature). Here, we addressed the functional significance of different structural vegetation elements for the behavioral thermoregulation by caterpillars of two butterfly species.

Results

Weather conditions influenced the caterpillar detection probability within host plant patches, indicating that caterpillars can hide and use suitable microclimates provided by vegetation structures to cope with weather variations. This is why we (1) evaluated the heterogeneity in temperature conditions provided by these structures, (2) quantified the influence of ambient temperature and light intensity on caterpillar body temperature, and (3) tested how position on structure, substrate color and exposition influenced caterpillar body temperature. As expected, vegetation structures provided heterogeneous temperature and sun exposition conditions, while caterpillar body temperature was dependent on ambient temperature and light intensity. But body temperature was additionally influenced by the position on vegetation structures, substrate color and exposition.

Conclusions

These results suggest that there is no unique and fixed structure in the vegetation subsuming the best thermal conditions for caterpillars. We argue that a better understanding of the thermal properties of vegetation structures is essential for correctly understanding caterpillar habitat-use and the behavioral mechanisms driving their body thermoregulation. Conceptually this means that thermal conditions should be included in the definition of a species' functional habitat. Practically this may influence the choice of appropriate habitat management for species of conservation concern.     

A biotrophic fungal infection of the great burnet Sanguisorba officinalis indirectly affects caterpillar performance of the endangered scarce large blue butterfly Phengaris teleius

Interactions between ecological communities of herbivores and microbes are commonly mediated by a shared plant. A tripartite interaction between a pathogenic fungus-host plant-herbivorous insect is an example of such mutual influences. In such a system a fungal pathogen commonly has a negative influence on the morphology and biochemistry of the host plant, with consequences for insect herbivore performance. Here we studied whether the biotrophic fbngus Podosphaera ferruginea, attacking the great burnet Sanguisorba officinalis, affects caterpillar performance of the endangered scarce large blue butterfly Phengaris teleius. Our results showed that the pathogenic ftmgus affected the number and size of inflorescences produced by food-plants and, more importantly, had in direct, plant-mediated effects on the abun dance, body mass and immune response of caterpillars. Specifically, we found the relationship between caterpillar abundance and variability in inflorescence size on a plant to be positive among healthy food-plants, and negative among infected food-plants. Caterpillars that fed on healthy food-plants were smaller than those that fed on infected food-plants in one studied season, while there was no such difference in the other season. We observed the relationship between caterpillar immune response and the proportion of infected great burnets within a habitat patch to be positive when caterpillars fed on healthy food-plants, and negative when caterpillars fed on infected food-plants. Our results suggest that this biotrophic fungal infection of the great burnet may impose a significant indirect influence on P. teleius caterpillar performance with potential consequences for the population dynamics and structure of this endangered butterfly.     

Early succession of butterfly and plant communities on set-aside fields

 Hypotheses on secondary succession of butterfly and plant communities were tested using naturally developed 1- to 4-year-old set-aside fields (n = 16), sown fields (n = 8) and old meadows (n = 4) in 1992 in South Germany. Pioneer successional fields (1st and 2nd year of succession, dominated by annuals) and early successional fields (3rd and 4th year of succession where perennials, especially grasses became dominant) had fewer plant species than mid-successional fields (old meadows). In contrast to established hypotheses, mean number of plant species decreased from 1- to 4-year-old set-aside fields. Species richness of butterfly communities did not change during the first four years of succession, but species composition changed greatly. Pioneer successional fields were characterized by (1) specialized butterflies depending on annual pioneer foodplants (e.g. Issoria lathonia), and (2) species preferring the pioneer successions despite their host plants being more abundant on early and mid-successional fields (e.g. Papilio machaon). The variability in butterfly species richness was best explained by flower abundance which was closely correlated with plant species richness. Species whose abundance was correlated with habitat connectivity were significantly smaller than species which correlated with flower abundance. Numbers of caterpillar species were correlated with numbers of adult butterfly species. Life-history features of butterflies changed significantly from pioneer to early and mid-successional fields. We found decreasing body size and migrational ability, decreasing numbers of species hibernating as imago, decreasing numbers of generations and increasing larval stage duration with age of succession, but, contrary to expectation, host plant specialization, numbers of egg-cluster laying species and egg diameter did not change with successional age. Received 18 September 1995 / Accepted: 17 July 1996     

Spatial patterns of host exploitation in a larval parasitoid of the predatory dusky large blue Maculinea nausithous

The foraging behaviour of the parasitoid wasp Neotypus melanocephalus and factors affecting parasitism at the population level were studied. This specialised parasitoid attacks caterpillars of the butterfly Maculinea nausithous, which sequentially feed on the plant Sanguisorba officinalis and specific red Myrmica ants. Among M. nausithous populations, there is considerable variation in caterpillar densities. At low M. nausithous densities, foraging might be time consuming for N. melanocephalus. High host densities may not always be advantageous to foraging parasitoids due to the caterpillars’ frequent overexploitation of ant resources and subsequent density-dependent mortality. In order to disperse progeny, we hypothesised that N. melanocephalus should search in a non-random way at the level of the micro-habitat, i.e., single flower heads of S. officinalis. Our analysis of 32 natural populations in the Upper Rhine valley in Germany did not show a density-dependent relationship between M. nausithous caterpillars and parasitism. Furthermore, habitat parameters like patch size and density of the host's food plant did not affect the parasitism rate. Foraging N. melanocephalus females preferred to search on large flower heads. They probed host-occupied flower heads only, visiting non-host-exploited flower heads only briefly. Time spent on a flower head was independent of the number of caterpillars per flower head. This study indicates that N. melanocephalus increases its foraging efficiency by preferring large flower heads that were previously shown to contain more host caterpillars than small flower heads. Furthermore, oviposition increases the likelihood of continuing to search on a flower head, which is an adaptive strategy for parasitoids foraging for aggregated hosts. However, many host-occupied flower heads were not probed by N. melanocephalus. We discuss the possibility that temporal host refuges of M. nausithous caterpillars might contribute to heterogeneity of parasitism, and why spreading offspring might constitute a suitable strategy for a parasitoid of an ant-parasitic butterfly.     

A climatic threshold triggers the die‐off of peat mosses during an extreme heat wave

Heat waves, which are projected to be more frequent and intense in a warmer climate, could become a serious threat to plants that rely on water surplus availability, such as bryophytes. Here, I take the advantage of the European summer 2003 climate anomaly to assess the impact of an extreme heat wave on peat mosses of the genus Sphagnum, a group of bryophytes forming the bulk of living and dead biomass in peatlands. With this aim, 20 selected bogs in the Italian Alps were checked for Sphagnum survival in the years following the heat wave. Over the study area, the period May–September 2003 was characterized by higher mean monthly air temperature (13.5 °C) and lower mean monthly precipitation (87 mm) compared with normal climatic conditions (11.5 °C and 117 mm, respectively) so that the heat wave coincided with a drought spell. As a consequence of the unusual water stress, I documented an increased mortality of peat mosses forming high hummocks. In particular, at habitat scale, the distribution of desiccated peat mosses was restricted to the hummock face receiving the greatest amount of solar irradiation. However, at regional scale, the present study identified a climatic threshold, simply defined by the ratio of precipitation to temperature (P : T), which triggered an irreversible desiccation of peat mosses when mean monthly P : T dropped below 6.5 (mm : °C) during May–September 2003. The absence of any sign of recovery after 4 years since the drought must be seen as a harbinger of the deleterious effects of extreme heat waves on organisms not adapted to cope with abrupt climate anomaly.     

Persistent versus transient tree encroachment of temperate peat bogs: effects of climate warming and drought events

Peatlands store approximately 30% of global soil carbon, most in moss‐dominated bogs. Future climatic changes, such as changes in precipitation patterns and warming, are expected to affect peat bog vegetation composition and thereby its long‐term carbon sequestration capacity. Theoretical work suggests that an episode of rapid environmental change is more likely to trigger transitions to alternative ecosystem states than a gradual, but equally large, change in conditions. We used a dynamic vegetation model to explore the impacts of drought events and increased temperature on vegetation composition of temperate peat bogs. We analyzed the consequences of six patterns of summer drought events combined with five temperature scenarios to test whether an open peat bog dominated by moss (Sphagnum) could shift to a tree‐dominated state. Unexpectedly, neither a gradual decrease in the amount of summer precipitation nor the occurrence of a number of extremely dry summers in a row could shift the moss‐dominated peat bog permanently into a tree‐dominated peat bog. The increase in tree biomass during drought events was unable to trigger positive feedbacks that keep the ecosystem in a tree‐dominated state after a return to previous ‘normal’ rainfall conditions. In contrast, temperature increases from 1 °C onward already shifted peat bogs into tree‐dominated ecosystems. In our simulations, drought events facilitated tree establishment, but temperature determined how much tree biomass could develop. Our results suggest that under current climatic conditions, peat bog vegetation is rather resilient to drought events, but very sensitive to temperature increases, indicating that future warming is likely to trigger persistent vegetation shifts.     

Desiccation tolerance of Sphagnum revisited: a puzzle resolved

As ecosystem engineers, Sphagnum mosses control their surroundings through water retention, acidification and peat accumulation. Because water retention avoids desiccation, sphagna are generally intolerant to drought; however, the literature on Sphagnum desiccation tolerance (DT) provides puzzling results, indicating the inducible nature of their DT. To test this, various Sphagnum species and other mesic bryophytes were hardened to drought by (i) slow drying; (ii) ABA application and (iii) chilling or frost. DT tolerance was assessed as recovery of chlorophyll fluorescence parameters after severe desiccation. We monitored the seasonal course of DT in bog bryophytes. Under laboratory conditions, following initial de‐hardening, untreated Sphagnum shoots lacked DT; however, DT was induced by all hardening treatments except chilling, notably by slow drying, and in Sphagnum species of the section Cuspidata. In the field, sphagna in hollows and lawns developed DT several times during the growing season, responding to reduced precipitation and a lowered water table. Hummock and aquatic species developed DT only in late autumn, probably as a response to frost. Sphagnum protonemata failed to develop DT; hence, desiccation may limit Sphagnum establishment in drier habitats with suitable substrate chemistry. Desiccation avoiders among sphagna form compact hummocks or live submerged; thus, they do not develop DT in the field, lacking the initial desiccation experience, which is frequent in hollow and lawn habitats. We confirmed the morpho‐physiological trade‐off: in contrast to typical hollow sphagna, hummock species invest more resources in water retention (desiccation avoidance), while they have a lower ability to develop physiological DT.     

Metapopulation viability analysis of the bog fritillary butterfly using RAMAS/GIS

Many species living in man-shaped landscapes are restricted to small natural habitat patches and form metapopulations; predicting their future is a central issue in applied ecology. We examined the viability of the bog fritillary butterfly Proclossiana eunomia Esper, a specialist glacial relict species, in a highly fragmented landscape (<1% of suitable habitat in 10 km²), by way of population viability analysis. We used comprehensive data from a long-term study in which a patchy population was monitored during ten consecutive years to parameterise a spatially structured metapopulation model using commercially available platform RAMAS/GIS 3.0. Population growth rate was density-dependent and modulated by various climatic variables acting on different developmental stages of the butterfly. Density dependence was probably related to larval parasitism by a specific parasitoid. Population size was negatively affected by an increase in the mean temperature. Dispersal was modelled as the observed proportion of movements between patches, taking into account the probability of emigration out of a given patch. Our model provided results close to the picture of the system drawn from the field data and was considered as useful in making predictions about the metapopulation. Demographic parameters proved to have a far higher impact on metapopulation persistence than dispersal or correlation of local dynamics. Scenarios simulating both global warming and management of habitat patches by rustic herbivore grazing indicated a decrease in the viability of the metapopulation. Our results prompted the regional nature conservation agency to modify the planned management regime. We urge conservation biologists to use structured population models including local population dynamics for viability analysis targeted to such threatened metapopulations in highly fragmented landscapes.     

Fine‐scale five‐year vegetation change in boreal bog vegetation

Abstract. Within an ombrogenous part of N. Kisselbergmosen, Rødenes, SE Norway, fine‐scale changes in species abundance, successional trends relative to the main gradients (as represented by DCA axes), and co‐ordinated change within pairs of the bottom layer species are studied. Data sets were sampled twice with a five‐year interval, and included species abundance and cover of mud bottom, naked peat and litter in 436 sample plots (16 cm× 16 cm), and species abundance in 6976 subplots (4 cm× 4 cm). Depth from the surface of subplots to the water table was estimated in 1991. Most summers and growing seasons were somewhat drier than normal in the 5‐yr period. The area covered by mud‐bottom, naked peat and litter increased significantly, as did the frequencies of the dwarf shrubs Calluna vulgaris and Andromeda polifolia in hummocks and upper lawn. Sample plots were significantly displaced downward the peat productivity gradient (DCA 2), reflecting the reduced cover of many bottom layer species, including all Sphagnum spp. Significant coordinated changes in cover of bottom layer species are described. The changes observed in hummocks support the existence of a local regeneration cycle, as suggested by other researchers. Some of the vegetation changes seem parallel to those reported from areas with a higher nitrogen deposition, but it is not likely that nitrogen deposition alone is the major cause of the observed changes. Between‐year variation in population size and climatic fluctuations may as well explain the observed changes.     

Field Simulation of Global Change: Transplanting Northern Bog Mesocosms Southward

A large proportion of northern peatlands consists of Sphagnum-dominated ombrotrophic bogs. In these bogs, peat mosses (Sphagnum) and vascular plants occur in an apparent stable equilibrium, thereby sustaining the carbon sink function of the bog ecosystem. How global warming and increased nitrogen (N) deposition will affect the species composition in bog vegetation is still unclear. We performed a transplantation experiment in which mesocosms with intact vegetation were transplanted southward from north Sweden to north-east Germany along a transect of four bog sites, in which both temperature and N deposition increased. In addition, we monitored undisturbed vegetation in control plots at the four sites of the latitudinal gradient. Four growing seasons after transplantation, ericaceous dwarf shrubs had become much more abundant when transplanted to the warmest site which also had highest N deposition. As a result ericoid aboveground biomass in the transplanted mesocosms increased most at the southernmost site, this site also had highest ericoid biomass in the undisturbed vegetation. The two dominant Sphagnum species showed opposing responses when transplanted southward; Sphagnum balticum height increment decreased, whereas S. fuscum height increment increased when transplanted southward. Sphagnum production did not differ significantly among the transplanted mesocosms, but was lowest in the southernmost control plots. The dwarf shrub expansion and increased N concentrations in plant tissues we observed, point in the direction of a positive feedback toward vascular plant-dominance suppressing peat-forming Sphagnum in the long term. However, our data also indicate that precipitation and phosphorus availability influence the competitive balance between Sphagnum, dwarf shrubs and graminoids.     

Species numbers,area, and habitat diversity on the habitat-islands of Mizorogaike pond,Japan

Species-area relationships of flowering plants were analyzed on the habitat-islands (hummocks on a floating bog) of Mizorogaike Pond, Japan. Three habitat units (Sphagnum cuspidatum unit,Sphagnum palustre unit, and fallen leaves unit) in which habitat conditions were homogeneous and a group of habitat-specific species occurred were recognized on the hummocks. Six hummock types were determined according to various combinations of the three habitat units. The most fundamental species-area relationships in which size itself affects the number of species were shown by hummocks with only one habitat unit. The species-area relationships for hummocks with two or three habitat units included the effects of habitat diversity in addition to size. The speciesarea curve for all hummocks was an average of these relationships. It is concluded that area in species-area relationships affects species numbers in two ways: number of habitat units and size of each habitat unit.     

Restoration of Sphagnum and restiad peatlands in Australia and New Zealand reveals similar approaches

Peatlands in Australia and New Zealand are composed mainly of Restionaceous and Cyperaceous peats, although Sphagnum peat is common in wetter climates (Mean Annual Precipitation > 1,000 mm) and at higher altitudes (>1,000 m). Experimental trials in two contrasting peatland types—fire‐damaged Sphagnum peatlands in the Australian Alps and cutover restiad bogs in lowland New Zealand—revealed similar approaches to peatland restoration. Hydrological restoration and rehydration of drying peats involved blocking drainage ditches to raise water tables or, additionally in burnt Sphagnum peatlands, peat‐trenching, and the use of sterilized straw bales to form semipermanent “dam walls” and barriers to spread and slow surface water movement. Recovery to the predisturbance vegetation community was most successful once protective microclimates had been established, either artificially or naturally. Specifically, horizontally laid shadecloth resulted in Sphagnum cristatum regeneration rates and biomass production 3–4 times that of unshaded vegetation (Australia), and early successional nurse shrubs facilitated establishment of Sporadanthus ferrugineus (New Zealand) within 2–3 years. On severely burnt or cutover sites, a patch dynamic approach using transplants of Sphagnum or creation of restiad peat “islands” markedly improved vegetation recovery. In New Zealand, this approach has been scaled up to whole mine‐site restoration, in which the newly vegetated islands provide habitat and seed sources for plants and invertebrates to spread onto surrounding areas. Although a vegetation cover can be established relatively rapidly in both peatland types, restoration of invertebrate communities, ecosystem processes, and peat hydrological function and accumulation may take many decades.     

Natural peat bog remnants promote distinct spider assemblages and habitat specific traits

Peat bogs are very sensitive and highly endangered ecosystems. They were once typical landscape elements in northern Germany, but today only a few remnants exist. On-going habitat degradation has alarming adverse effects on biodiversity, and, from a conservation viewpoint, it is imperative to evaluate the current ecological quality of the remaining peat bog remnants to assess the intensity of degradation and to suggest reasonable management strategies. In 2007, spiders were sampled in 23 study sites representing typical peat bog habitat types in the northern parts of Westphalia (NW Germany). In all, 214 species from 18,413 adult individuals have been collected. Multivariate analyses showed that different peat bog successional stages harbour distinct spider assemblages with succession being the main driver for species separation. Pardosa sphagnicola, Pirata piscatorius and P. uliginosus can be considered as flagship species for near-natural or natural peat bogs. Trait analyses showed that habitat specialisation for high moisture is negatively affected by succession. Peat bogs are now only small remnants, but, nevertheless, they have a high conservation value as they still harbour a distinct species assemblage and specialised species.     

An evaluation of the use of translocated blanket bog vegetation for heathland restoration

Abstract. The decision was taken by an opencast coal mining company to translocate on-site blanket bog vegetation, on completion of mining, at a site in Co. Durham, UK, both to preserve it and to use it to enhance recolonization. The vegetation of the treatments was monitored for seven years after site completion and this paper reports on the progress of the translocated material and its effect on recolonization. Translocation of large turves of blanket bog into carefully prepared receptor cells preserved most of the vegetation intact, but resulted in severe decline in the frequency of Sphagnum, while the design of the receptor site as strips of translocated vegetation enclosing strips of spread, stored peat accelerated recolonization of the intervening bare peat by Calluna vulgaris, but not of other target species. This attempt to translocate blanket bog vegetation and at the same time use it to accelerate recolonization was only partly successful. It was concluded that the ecological requirements of species known to be significant for ecosystem function, such as Sphagnum, must be fulfilled if translocation of blanket bog is to be attempted in future.     

POLLEN SUCCESSION,ABSOLUTE POLLEN FREQUENCY,AND RECURRENCE SURFACES IN CENTRAL JAPAN

A generalized pollen diagram, associated with three simplified pollen diagrams from Tsubogakure (1,500 m), Nakatashiro (1,400 m) and Yashima-ga-hara (1,650 m) bogs in central Japan, represents five pollen zones for the last 12,000 years, i.e., L (before 10,500 B.P., pine-boreal); R I (10,500–9,500 B.P., boreal-oak); R II (9,500–4,500 B.P., temperate); R IIIa (4,500–1,500 B.P., temperate-boreal); and R IIIb (after 1,500 B.P., pino-nonarboreal). Absolute pollen frequency is high in well-humified peat, in gyttja (deposited immediately below the first peat formation), and in peat in the part of the R IIIa cooling stage, and it is low in less-humified peat, since the former sediments have slow and the latter rapid rates of accumulation, respectively. Changes of plant communities should affect the absolute pollen frequency, but changes of sedimentation rates are more critical. After a re-examination of Nakatashiro bog, it is hardly possible to recognize a recurrence surface in the European sense, nor can the accumulation of thin tephra on the bog surface be responsible for a temporary halt in peat growth. Nakatashiro bog (like Tsubogakure bog) is a low-moor bog, and true recurrence surfaces would not be expected in it. In a raised Yashima-ga-hara bog, however, there are seven recurrence surfaces without a volcanic ash band; the well-humified horizons correspond to low values of Sphagnum spores and Cyperaceae pollen, and the less-humified horizons to high values of Sphagnum spores and Cyperaceae pollen. Peaks of these species in the upper core correspond to those Cryptomeria pollen, an indicator of the high precipitation (generally >1,800 mm/yr). Regularly interrelated fluctuations among these species, absolute pollen frequency, and peat horizons suggest that the precipitation was low in well-humified peat and was high in less-humified peat.