Alnus Forest Research Articles

Dry matter dynamics and carbon flux along riverine forests of Gori valley, Western Himalaya

IntroductionRiverine forests in the Himalaya represent a biodiverse, dynamic, and complex ecosystem that offers numerous ecosystem services to local and downstream communities and also contributes to the regional carbon cycle. However, these forests have not been assessed for their contribution to dry matter dynamics and carbon flux. We studied these parameters along three classes of riverine forests in eastern Uttarakhand, dominated by Macaranga, Alnus, and Quercus-Machilus forest.MethodsUsing volume equations, we assessed tree biomass, carbon storage, and sequestration in the study area.ResultsThe total standing tree biomass in Macaranga, Alnus, and Quercus-Machilus forest ranged from 256.6 to 558.1 Mg ha−1, 460.7 to 485.8 Mg ha−1, and 508.6 to 692.1 Mg ha−1, respectively. A total of 77.6–79.6% of vegetation biomass was stored in the aboveground biomass and 20.4–22.4% in belowground plant parts across the riverine forests. The carbon stock in Macaranga forest ranged from 115.5 to 251.1 Mg ha−1, in Alnus forest from 207.3 to 218.6 Mg ha−1, and in Quercus-Machilus forest from 228.9 to 311.4 Mg ha−1. The mean annual litterfall was accounted maximum for Quercus-Machilus forest (5.94 ± 0.54 Mg ha−1 yr.−1), followed by Alnus (5.57 ± 0.31 Mg ha−1 yr.−1) and Macaranga forest (4.67 ± 0.39 Mg ha−1 yr.−1). The highest value of litterfall was recorded during summer (3.40 ± 0.01 Mg ha−1 yr.−1) and the lowest in winter (0.74 ± 0.01 Mg ha−1 yr.−1). The mean value of net primary productivity and carbon sequestration was estimated to be highest in Quercus-Machilus forest (15.8 ± 0.9 Mg ha−1 yr.−1 and 7.1 ± 0.9 Mg C ha−1 yr.−1, respectively) and lowest in Alnus forest (13.9 ± 0.3 Mg ha−1 yr.−1 and 6.1 ± 0.3 Mg C ha−1 yr.−1, respectively).DiscussionThe results highlight that riverine forests play a critical role in providing a large sink for atmospheric CO2. To improve sustainable ecosystem services and climate change mitigation, riverine forests must be effectively managed and conserved in the region.

Alnus forests of the Abkhazia

The features of the distribution, formation and the cenotic dynamics of forests of Alnus barbata C.A. Mey are described; environmental functions and the role of Alnus forests in the composition of the forest cover of the region are highlighted; bioecological and forestry features are highlighted; it is indicated that Alnus barbata is an economically valuable woody species; its useful qualities for practical purposes are emphasized; the ways to increase the productivity of Alnus forests using foresting, forest melioration and forest cultural sampling, as well as measures of using valuable fast-growing, resistant to the waterlogged conditions of growing area, local and foreign woody breeds ( Cupressus lusitanica , Metasequoia glyptostroboides , Taxodium distichum , Liquidambar styraciflua, Liriodendron tulipifera, Platanus x acerifolia, Eucalyptus viminalis ).

Airborne and belowground phytotoxicity of invasive Ageratina adenophora on native species in Nepal

Volatile compounds from leaf litter of invasive alien Ageratina adenophora are known to inhibit growth of native species in sub-tropical Asia, but there is not much evidence if the litter affects tree species. In particular, the relative importance of airborne inhibition versus belowground effect of invaded soil on tree species is rarely explored. We used A. adenophora uninvaded and invaded soils to follow germination and seedling growth of a native Nepalese tree Schima wallichii (DC.) Korth. in the presence and absence of leaf litter of A. adenophora. We also compared diversity of native species in the uninvaded and invaded sites in Nepal. We found that A. adenophora invasion is associated with lower native species richness and correlated with lower tree canopy cover. Invaded soil and the proximity of A. adenophora leaf litter decreased seed germination rate of S. wallichii. Both invaded soil and leaf litter of the weed inhibited S. wallichii shoot and root biomass accumulation independently of each other. As far as we know, this is the first study to report these two effects simultaneously. In conclusion, belowground effects of A. adenophora invaded soil and airborne effects of leaf litter have a potential to inhibit native tree regeneration in Nepalese Schima–Alnus forests. Maintaining high canopy cover and removing litter of the weed should be tested to control its invasion.

Comparative study of macrofungi in different patches of Boshan Community Forest in Kathmandu, Central Nepal

Macrofungi are considered as a group of high-value forest resources worldwide. In this paper, we report species richness and composition of macrofungi in three different forest patches (Schima-Castanopsis, Pinus and Alnus forest) of mid-hill, central Nepal, which were managed under Boshan Community Forest. A Systematic random sampling was applied where 20 rectangular plots of size 10 m x 10 m were laid at 1500 m to 1600 m elevation in each forest type. Species richness and composition of macrofungi were accessed in each forest type. Schima-Castanopsis forest was the richest in terms of macrofungal diversity (70 species), followed by Alnus forest (64) and Pinus forest (56). Polyporaceae was the largest family, followed by Amanitaceae. Agaricales (Rusulla and Amanita) were dominant in Schima-wallichi and Alnus forests, whereas Boletales were dominant in Pine forest. Macrofungal species richness increased with increasing canopy, soil moisture and soil pH. The species richness, however, had weak relationships with litter cover and disturbance. Based on the present study it can be concluded that the study area is rich in macrofungal diversity. Moist soil followed by litter and decaying wood assist the higher diversity of macrofungi. Species diversity is higher in moist and dense canopy forests (like, Schima-Castanopsis and alder) than in open and dry pine forest. Soil moisture, soil pH and tree canopy cover are the most important variables affecting macrofungal diversity. Botanica Orientalis – Journal of Plant Science (2017) 11: 43–48

Postglacial fire history and interactions with vegetation and climate in southwestern Yunnan Province of China

Abstract. A high-resolution, continuous 18.5 kyr (1 kyr = 1000 cal yr BP) macroscopic charcoal record from Qinghai Lake in southwestern Yunnan Province, China, reveals postglacial fire frequency and variability history. The results show that three periods with high-frequency and high-severity fires occurred during the periods 18.5–15.0, 13.0–11.5, and 4.3–0.8 ka, respectively. This record was compared with major pollen taxa and pollen diversity indices from the same core, and tentatively related to the regional climate proxy records with the aim to separate climate- from human-induced fire activity, and discuss vegetation–fire–climate interactions. The results suggest that fire was mainly controlled by climate before 4.3 ka and by the combined actions of climate and humans after 4.3 ka. Before 4.3 ka, high fire activity corresponded to cold and dry climatic conditions, while warm and humid climatic conditions brought infrequent and weak fires. Fire was an important disturbance factor and played an important role in forest dynamics around the study area. Vegetation responses to fire after 4.3 ka are not consistent with those before 4.3 ka, suggesting that human influence on vegetation and fire regimes may have become more prevalent after 4.3 ka. The comparisons between fire activity and vegetation reveal that evergreen oaks are flammable plants and fire-tolerant taxa. Alnus is a fire-adapted taxon and a nonflammable plant, but density of Alnus forest is a key factor to decide its fire resistance. The forests dominated by Lithocarpus/Castanopsis and/or tropical trees and shrubs are not easy to ignite, but Lithocarpus/Castanopsis and tropical trees and shrubs are fire-sensitive taxa. Fire appears to be unfavourable to plant diversity in the study area.

Changing environments and Human settlement during Mid-Holocene in Rio de Moinhos Beach (Esposende, Northern Portugal)

This work results from a combination of sedimentological, palaeocological and archaeological data, made available due to special meteo-marine conditions that removed sand from the beach of Rio de Moinhos, exhuming older sedimentary deposits and bringing into evidence a huge amount of archaeological remains – Prehistoric and Roman (the latter not considered here).
 In this paper the relationship between the palaeoenvironments and the contemporary human evidence is analysed. The time interval considered in this study goes from 5590±80 yr BP (4614-4319 cal BC 2) to 3550±30 yr BP (2007-1772 cal BC 2) and encompasses a succession of environments comprising an Alnus forest, a wetland, a brackish lagoon and a fresh water lake, showing a progressively finer and more organic sequence, and higher infilling rates. Initially, in the wetland phase, there are no certain traces of human activity in the pollen content, but from around 4860±30 yr BP (3703-3539 cal BC 2) cereal cultivation and agriculture are detected. Later on indications of grazing also appear.
 However, human presence is well documented by a lithic assemblage dated from the interval between 5590±80 y BP (4614-4319 cal BC 2) and 4680±30 yr BP (3622-3370 cal BC 2). Another lithic industry predates 5590±80 yr BP, being therefore prior to the Alnus forest. Apparently, it documents the earliest evidence of human presence at the site.

Phylogenetic Relationships among Species of Phellinus sensu stricto, Cause of White Trunk Rot of Hardwoods, from Northern North America

Species in Phellinus s.s. are some of the most important wood-decaying fungal pathogens in northern temperate forests, yet data on species incidence in North America remains limited. Therefore, phylogenetic analyses were performed using four loci (ITS, nLSU, tef1 and rpb2) with isolates representing 13 species. Results of phylogenetic analyses using maximum likelihood and Bayesian inference revealed that eight species of Phellinus s.s. occur in North America, and include: P. alni, P. arctostaphyli, P. betulinus, P. lundellii, P. nigricans, P. tremulae and two undescribed species, P. NA1 and P. NA2. Meanwhile, P. tuberculosus, P. igniarius s.s., P. populicola, P. laevigatus s.s. and P. orienticus were not detected and appear restricted to Europe and/or Asia. The tef1 dataset outperformed all other loci used and was able to discriminate among all 13 of the currently known Phellinus s.s. species with significant statistical support. The internal transcribed spacer (ITS) region performed well but a high level of intraspecific variation could lead to inflated taxa recognition. Phellinus alni exhibited the broadest host range, as demonstrated previously, and appears to be the most common species in northern hardwood (Acer-Betula-Fagus), northern floodplain (Fraxinus-Populus-Ulmus) and coastal alder (Alnus) forests of North America.

Testing the link between community structure and function for ectomycorrhizal fungi involved in a global tripartite symbiosis

Alnus trees associate with ectomycorrhizal (ECM) fungi and nitrogen-fixing Frankia bacteria and, although their ECM fungal communities are uncommonly host specific and species poor, it is unclear whether the functioning of Alnus ECM fungal symbionts differs from that of other ECM hosts. We used exoenzyme root tip assays and molecular identification to test whether ECM fungi on Alnus rubra differed in their ability to access organic phosphorus (P) and nitrogen (N) when compared with ECM fungi on the non-Frankia host Pseudotsuga menziesii. At the community level, potential acid phosphatase (AP) activity of ECM fungal root tips from A.rubra was significantly higher than that from P.menziesii, whereas potential leucine aminopeptidase (LA) activity was significantly lower for A.rubra root tips at one of the two sites. At the individual species level, there was no clear relationship between ECM fungal relative root tip abundance and relative AP or LA enzyme activities on either host. Our results are consistent with the hypothesis that ECM fungal communities associated with Alnus trees have enhanced organic P acquisition abilities relative to non-Frankia ECM hosts. This shift, in combination with the chemical conditions present in Alnus forest soils, may drive the atypical structure of Alnus ECM fungal communities.

Reconstructing late Holocene vegetation and fire histories in monsoonal region of southeastern China

Eastern subtropical China is a key region for understanding the variability of the East Asian Summer Monsoon (EASM). Multidisciplinary studies in southeastern China have shown that the summer monsoon intensity declined in the mid-late Holocene. We present a high-resolution pollen record of the last 4000calyr BP in Jinggang Mts of Jiangxi Province, southeastern China. The identified pollen taxa from the core can be statistically divided into three groups corresponding to evergreen, deciduous and wetland communities. The transitions between evergreen and deciduous-coniferous pollen associations is likely caused by temperature fluctuations, indicating that climate was relatively cool at 3800–3200calyr BP and 2200–1300calyr BP and warmer at 3200–2800calyr BP and 1300–800calyr BP. The vegetation study suggests that an Alnus-dominant association represents a secondary forest that usually takes place and expand after repeated forest fires. The charcoal concentration from the core depicts at least six major forest fire events since 4000calyr BP, most of which were followed by the development of an Alnus forest community. This result suggests that the EASM weakened toward the late Holocene and that its related decrease in moisture led to large forest wildfires. Furthermore, the rapid formation of a swamp and the subsequent development of the Alnus wetland community at ~550calyr BP suggest a gradual drying up of the lake, which was likely related to “the Little Ice Age”. As a result of a substantial burning related to an intensification of the human cultivation practices, Alnus reached its highest values in the last 200years along with abundant wetland herbs, pioneer ferns (mainly Dicranopteris) and high charcoal concentrations. The present evidence of several sharp floristic and climate changes coincides with either the collapse or the beginning of some Chinese dynasties, which will need further research on the relationship between natural and human cultural changes.

Vegetation responses to interglacial warming in the Arctic: examples from Lake El'gygytgyn, Far East Russian Arctic

Abstract. Preliminary analyses of Lake El'gygytgyn sediment indicate a wide range of ecosystem responses to warmer than present climates. While palynological work describing all interglacial vegetation is ongoing, sufficient data exist to compare recent warm events (the postglacial thermal maximum, PGTM, and marine isotope stage, MIS5) with "super" interglaciations (MIS11, MIS31). Palynological assemblages associated with these climatic optima suggest two types of vegetation responses: one dominated by deciduous taxa (PGTM, MIS5) and the second by evergreen conifers (MIS11, MIS31). MIS11 forests show a similarity to modern Picea–Larix–Betula–Alnus forests of Siberia. While dark coniferous forest also characterizes MIS31, the pollen taxa show an affinity to the boreal forest of the lower Amur valley (southern Russian Far East). Despite vegetation differences during these thermal maxima, all glacial–interglacial transitions are alike, being dominated by deciduous woody taxa. Initially Betula shrub tundra established and was replaced by tundra with tree-sized shrubs (PGTM), Betula woodland (MIS5), or Betula–Larix (MIS11, MIS31) forest. The consistent occurrence of deciduous forest and/or high shrub tundra before the incidence of maximum warmth underscores the importance of this biome for modeling efforts. The El'gygytgyn data also suggest a possible elimination or massive reduction of Arctic plant communities under extreme warm-earth scenarios.

Symbiotic Frankia bacteria in Alnus forests in Mexico and the United States of America: is geographic location a good predictor of assemblage structure?

While the biogeography of Alnus species is well characterized, that of their microbial symbionts remains less well understood. Little is known, for example, about how the genotypic richness of Alnus-associated Frankia bacteria varies at the continental scale, and the richness of Alnus-associated Frankia at tropical latitudes has yet to be explored. In this study, we conducted sequence-based analyses of the nifH gene comparing Frankia found in root nodules of two Alnus species in central Mexico with those associated with two Alnus species in the northwestern United States of America (USA). Similar to Frankia assemblages in northwestern USA and other geographic locations, genotypic richness within the Mexican samples was low, with five genotypes total using a ≥97% nifH sequence similarity cutoff. The vast majority of Mexican sequences belonged to genotypes also very common in northwestern USA Alnus forests, although two novel Mexican genotypes were identified. Phylogenetic analyses confirmed that all of the genotypes present in Mexico belong to larger clades of Alnus-associated Frankia. Genotype- and distance-based community analyses indicated that neither geographic location nor the phylogenetic relationships among hosts are strong predictors of Frankia assemblage structure. Our results suggest that factors other than classic biogeography are more influential in determining the continental-scale distribution and diversity of Alnus-associated Frankia.

Ectomycorrhizal fungi in Mexican Alnus forests support the host co-migration hypothesis and continental-scale patterns in phylogeography

To examine the geographic patterns in Alnus-associated ectomycorrhizal (ECM) fungal assemblages and determine how they may relate to host plant biogeography, we studied ECM assemblages associated with two Alnus species (Alnus acuminata and Alnus jorullensis) in montane Mexico and compared them with Alnus-associated ECM assemblages located elsewhere in the Americas. ECM root samples were collected from four sites in Mexico (two per host species), identified with ITS and LSU rRNA gene sequences, and assessed using both taxon- (richness, diversity, evenness indices) and sequence divergence-based (UniFrac clustering and significance) analyses. Only 23 ECM taxa were encountered. Clavulina, an ECM lineage never before reported with Alnus, contained the dominant taxon overall. ECM assemblage structure varied between hosts, but UniFrac significance tests indicated that both associated with similar ECM lineage diversity. There was a strikingly high sequence similarity among a diverse array of the ECM taxa in Mexico and those in Alnus forests in Argentina, the United States, and Europe. The Mexican and United States assemblages had greater overlap than those present in Argentina, supporting the host-ECM fungi co-migration hypothesis from a common north temperate origin. Our results indicate that Alnus-associated ECM assemblages have clear patterns in richness and composition across a wide range of geographic locations. Additional data from boreal western North America as well as the eastern United States and Canada will be particularly informative in further understanding the co-biogeographic patterns of Alnus and ECM fungi in the Americas.

Invasion of Norway spruce (Picea abies) and the rise of the boreal ecosystem in Fennoscandia

Summary 1. Norway spruce ( Picea abies ), one of the dominant tree species in Eurasia, has spread slowly westward in northern Europe, invading eastern Finland about 6500 calibrated years ago (cal. years BP), eastern central Sweden about 2700 cal. years BP and southern Norway about 1000 cal. years BP. Its spread is the most recent and best constrained invasion of a main tree species in northern Europe and allows an assessment of colonization patterns and associated competitive replacement processes. 2. We analysed five selected high-resolution pollen accumulation rate (PAR) -records along a 700-km long transect in the direction of P. abies invasion from eastern Finland to central Sweden across the present P. abies - and Pinus sylvestris- dominated southern boreal zone. 3. Our results show that the P. abies population increased in size from the time of the initial expansion to levels comparable with the modern in 100‐550 years. At each site P. abies invaded a dense, intact Pinus ‐ Betula ‐ Alnus forest, mixed with temperate deciduous taxa, particularly Tilia cordata and Corylus avellana . The resident mixed forest provided no or weak resistance to the colonization of P. abies , and the variable population growth rate was therefore not caused by compositional differences in the resident forest but by other, possibly local edaphic factors. 4. Of the taxa that formed the resident forest, T . cordata responded most strongly to the invasion of P. abies . This suggests that the mid-Holocene T. cordata population decline was not directly climateinduced but resulted from competitive replacement due to overlapping ecological niches with P. abies , a stronger competitor. 5. Synthesis . The rise to dominance of P. abies was caused not only by its rapid population growth but by associated competitive suppression of other taxa, leading to a major ecosystem change from a mixed conifer-deciduous forest to the modern P. abies - and P. sylvestris -dominated boreal conifer forest in central Fennoscandia. This competitive suppression by P. abies is still reflected in the scattered occurrence and generally weak performance of T. cordata in the boreal zone of Europe and may influence its distribution and abundance patterns under predicted future climate scenarios.

A palynological study of environmental changes and their implication for prehistoric settlement in the Ilan Plain, northeastern Taiwan

Pollen records from two sediment cores taken from Ilan Plain, northeastern Taiwan provide new insights into the environmental and cultural history of the last 4200 years. The record indicates a relatively warm climate at around 4200 cal b.p. The environmental conditions would have been suitable for people whose settlements and activities were mainly in the littoral zone during this period. However, at ca. 3800 cal b.p., elements tolerant of brackish water dominated the vegetation, indicating that the environment was influenced by marine incursion. The remarkable increase in wetland flora suggests the presence of widespread marshlands thereafter. It is quite conceivable that settlement movement from the fluvial plain to hills between 3800 and 2400 cal b.p. can be correlated with the environmental changes in lowlands. A conspicuous gap in the archaeological sequence between 2400 and 1300 cal b.p. corresponds chronologically with a period of heavy rainfall or frequent typhoons as indicated by the aggradational episode in the Lanyang drainage basin as well as the flourishing of Alnus forests. The persistence of frequent landslides and climate deterioration would have had a dramatic impact on ancient humans and led to abandonment of the settlements. By 1300 cal b.p. a lowland flora is widespread indicating a shift from a marsh to a terrestrial environment in response to a well-developed fluvial plain. Decrease of landslides and the amelioration in climate could have advantages to human activities again. However, both the pollen and archaeological records indicate that intensive colonisation had a profound effect upon the vegetation within the Ilan region about 400 years ago.

Putting the stewardship concept into practice: Commercial moss harvest in Northwestern Oregon, USA

Increased demand for non-timber forest products has spurred increased regulation of these resources as well as recognition of the need to include harvesters in monitoring efforts. The moss harvest monitoring program on the Siuslaw National Forest in the Pacific Northwest included a pilot stewardship program involving two 5-year leases of 890 ha parcels of mixed conifer- Alnus forest to a local commercial moss harvester under the condition that the harvester adhere to specific harvest guidelines and provide data on how much moss was removed. Across both lease areas, nearly 66,000 kg of tree-moss was harvested over a 48-month period, mostly during the dry summer season. The program provided for direct harvester participation, made the product available on a year-round basis, and improved patrol of illegal harvest in the lease area. In addition, three experiments were conducted to contrast moss abundance, species richness, and species composition using four levels of harvest intensity (Control in which harvest was prohibited, Low Intensity harvest approximating current standards and guidelines = ca. 34 kg/ha, High Intensity harvest approximating unregulated harvest levels = ca. 112 kg/ha, and “No Rules” harvest with no restrictions of any kind). Subsampling data indicated that cover on vine maple shrubs immediately following harvest was reduced by 5% and 16–20% for Low Intensity and High Intensity harvest treatments, respectively. These treatment differences remained for two years in riparian areas but were non-significant after one year in upland mixed forest. Species richness did not vary among harvest intensities and impacts to species composition, which were generally restricted to stems actually harvested, dissipated after one or two years. Because impacts restricted to harvested stems averaged out at the plot-level, plot-level surveys were less sensitive to harvest impacts than host-level subsampling. Due to the slow rate of recovery of this resource, future Stewardship Areas for moss harvest may be impractical, but this approach may be a viable option for non-timber forest products with shorter rotations.

Birth, life and death of the Pannonian Lake

The Miocene-Pliocene Pannonian Lake formed in an extensional basin system behind the compressional arc of the Carpathians. Its size and depth were comparable to those of the Caspian Sea. Subsidence began in Middle Miocene times, forming deep, pelagic basins, separated by reef-bearing ridges. Clastic influx filled the marginal basins during Middle Miocene time. Prograding deltas dissected the lake and completed the infilling of the basin system by the end of the Pliocene. Basin plain, prodelta, delta front, delta plain, beach, fluviatile, and marsh environments can be recognized. Terminal Miocene uplift of the Carpathians isolated the Pannonian region from the rest of Paratethys. The subsequent decrease of salinity resulted in the evolution of an endemic, freshwater mollusc fauna. Rich nutrient influx from rivers supported high organic productivity (dinoflagellates, diatoms, nannoplankton, foraminifers, ostracods, etc.), yielding organic-rich sediments. Preservation of organic matter was helped by a stratified water column and oxygen deficient bottom conditions. Deep burial, continuing subsidence, and high geothermal flux due to an extremely thin crust, led to the formation of commercially exploitable oil and gas accumulations. Shallow lacustrine zones of basin margins provided suitable environments for a rich Congeria-Melanopsis mollusc fauna. Wave action on beaches produced commercially exploitable pure quartz sand deposits. Taxodium and Alnus forests flourished around the lake producing enormous lignite deposits. Besides a rich land snail and mammal fauna, prehominids lived in the forests. There was a warm, temperate climate, with probably frostfree winters. Basaltic volcanoes overlooked the landscape, and maars hosted minor lakes with rich algal flora forming oil shale. The catchment area included most of the Carpathians and parts of the Apls and Dinarides. The positive water balance resulted in a supposed overflow in the southern margin, supplying exotic fauna to the South Carpathian and Dacian basins of the Eastern Paratethys. The Pannonian Lake was completely filled by the end of Pliocene. Recent lakes in the Carpathian Basin are not descendants of it.

開析谷の遺跡とそれをとりまく古環境復元 関東平野中央部の川口市赤山陣屋跡遺跡における完新世の古環境

Paleoenvironmental reconstruction of the Holocene since 8, 000 years ago, based on detailed archaeological excavation and geological and paleobotanical studies, including fossil pollen assemblage, plant macrofossil assemblage, and fossil wood assemblage, has been performed on the sediments in the dissected valley at the Akayama Site (35°50′55″N, 139°45′10″E), about 15km north of Tokyo, in the southeastern part of the Ohmiya Upland, central Kanto Plain. From the results, 5 epoch-making events (E-1 to E-5) and 6 paleoenvironmental stages (I to VI, divided based on their events) were identified. An event is characterized by an erosion and a subsequent drastic change of the sedimentary environment in the valley.Both Stage I(ca 8, 000-6, 500y.B.P.) and Stage II (ca 6, 500-5, 300y.B.P.), corresponding to the Earliest and Early Jomon Ages in archaeology, are characterized by a landslide or collapse of the precipice along the marginal upland ridge, and the reclamation by them or their secondary sediments in a valley under a marine or brackish environment. The sea reached a level 3m above its present level in late Stage I. During both stages, a warm-temperate deciduous broad-leaved forest composed of mainly Quercus subgen. Lepidobalanus stood on the upland to scarp, and Polygonum thunbergii, Chrisoplenium, and Carex communities covered the ridge at the edge of the water, in the valley.Stage III(ca 5, 300-4, 000y.B.P.) corresponds to the Middle Jomon Age, and is distinguished by a standing of Alnus japonica forest in the valley and an invasion of Aphananthe and Celtis in the upland to scarp forest. The deposition of clayey soil containing many Castanea-Castanoposis and Mallotus plant fossils is evidence of the destruction of the forest and the cultivation or semicultivation of Castanea on the scarp to upland.Stage IV (ca 4, 000-2, 200y.B.P.) corresponding to the Late and Later Jomon Ages is defined as an invasion of Fraxinus mandshurica, Aesculus turbinata and Acer to the Alnus forest in the valley, and the beginning of a wide expansion of Cryptomeria, Chamaecyparis group and Quercus subgen. Cyclobalanopsis on the upland. These facts testify to a cooler and wetter climate than that in previous stages. During this stage, part of the bottom forest was destroyed by man, and then manufacturing of Aesculus products was begun.Stage V (ca 2, 200-500y.B.P.) and Stage VI (since 500y.B.P.), later than the Yayoi Age in terms of archaeology, were characterized by a strong impact of man on vegetation and by a swampy valley bottom in which Cyperaceae and Gramineae communities stand. Almost all of the scarp and bottom forests have disappeared mainly as a result of human activities.

A LATE MEDIEVAL CLEARING AT THE EDGE OF THE DINKEL VALLEY (EASTERN NETHERLANDS)

SUMMARY A late medieval clearing of Alnus forest at the edge of the Dinkel valley and at the foot of the Ootmarsum hill (Twente, Eastern Netherlands) is revealed from pollen analysis of peat developed near a source of a vanished brooklet. The clearing later developed from a wet sedge-meadow to a pasture. Details on the medieval forest history are also discussed.