Birch Woodland Research Articles

Natural colonization as a means to upscale restoration of subarctic woodlands in Iceland

The global climate and biodiversity crisis has led to extensive restoration initiatives, calling for cost‐effective strategies harnessing the potential of natural processes. Natural colonization of target species is a key process in the scaling up of woodland restoration, and effective planning and implementation of restoration strategies requires a mechanistic understanding of colonization processes. In this study, we investigated patterns and processes of natural colonization of mountain birch (Betula pubescens ssp. tortuosa), the only native woodland‐forming tree species in Iceland, into adjacent treeless lands under diverse conditions, and its implications for low‐intensity restoration strategies. Accordingly, we assessed spatial patterns of seedling densities on transects extending from 10 birch woodlands in Iceland and analyzed the impact of local environments on colonization dynamics. Seedling densities generally decreased rapidly with distance from the seed source to around 40 m. In many study areas, however, birch seedlings were registered at high enough densities to potentially form woodlands, up to 140 m from a standing seed source. We identified a range of biotic and abiotic determinants of colonization, with the largest number affecting the early‐establishment phase of birch colonization, including safe site availability, wind speed and dominant direction, and grazing. Our results demonstrate a good potential for natural colonization as a restoration strategy for birch woodlands in subarctic environments, and they can furthermore be used to identify areas where birch colonization is likely to occur naturally and determine appropriate interventions that can facilitate birch colonization in areas where it is less likely.

Dynamics of vegetation of Central Yamal in the holocene

The paper presents new paleobotanical data in combination with the results of radiocarbon dating obtained from organomineral deposits of the northern shore of Lake. Pechevalavato (70°13’22.3” N, 71°50’57.6” E) in the Seyakha river basin and characterizing the dynamics of vegetation in the northern part of Central Yamal in the Holocene. It has been established that in the Early Holocene (10.2–8.7 thousand years ago) in Yamal, tree-shaped birch (Betula sect. Betula) grew no less than 400 km north of the modern northern limit of distribution of Betula pubescens ssp. tortuosa. Favorable conditions for the existence of birch woodlands at this time were due to the higher temperature of the growing season, exceeding by approximately 3–4 °C the modern parameters of the warmest month of the summer season. At the end of the Early Holocene (after 8.5 thousand cal BP), forest vegetation began to degrade, and open landscapes with diverse plant communities of the subarctic tundra and single trees in the river valley spread. About 6.5 thousand cal BP the northern subarctic tundra began to form the zonal appearance of the study area in climatic conditions close to modern ones.

Estimation of ammonia deposition to forest ecosystems in Scotland and Sri Lanka using wind-controlled NH3 enhancement experiments

Ammonia (NH3) pollution has emerged as a major cause of concern as atmospheric concentrations continue to increase globally. Environmentally damaging NH3 levels are expected to severely affect sensitive and economically important organisms, but evidence is lacking in many parts of the world. We describe the design and operation of a wind-controlled NH3 enhancement system to assess effects on forests in two contrasting climates. We established structurally identical NH3 enhancement systems in a temperate birch woodland in the UK and a tropical sub-montane forest in central Sri Lanka, both simulating real-world NH3 pollution conditions. Vertical and horizontal NH3 concentrations were monitored at two different time scales to understand NH3 transport within the forest canopies. We applied a bi-directional resistance model with four canopy layers to calculate net deposition fluxes. At both sites, NH3 concentrations and deposition were found to decrease exponentially with distance away from the source, consistent with expectations. Conversely, we found differences in vertical mixing of NH3 between the two experiments, with more vertically uniform NH3 concentrations in the dense and multi-layered sub-montane forest canopy in Sri Lanka. Monthly NH3 concentrations downwind of the source ranged from 3 to 29 μg m−3 at the UK site and 2–47 μg m−3 at the Sri Lankan site, compared with background values of 0.63 and 0.35 μg m−3, respectively. The total calculated NH3 dry deposition flux to all the canopy layers along the NH3 transects ranged from 12 to 162 kg N ha−1 yr−1 in the UK and 16–426 kg N ha−1 yr−1 in Sri Lanka, representative of conditions in the vicinity of a range of common NH3 sources. This multi-layer model is applicable for identifying the fate of NH3 in forest ecosystems where the gas enters the canopy laterally through the trunk space and exposes the understorey to high NH3 levels. In both study sites, we found that cuticular deposition was the dominant flux in the vegetation layers, with a smaller contribution from stomatal uptake. The new facilities are now allowing the first ever field comparison of NH3 impacts on forest ecosystems, with special focus on lichen bio-indicators, which will provide vital evidence to inform NH3 critical levels and associated nitrogen policy development in South Asia.

Palaeoecological reconstruction of the Late Glacial and Early Holocene based on pollen data from lake Novozhilovo (Perm region, Russia)

This paper provides the first paleolimnological studies performed in the upper Kama basin (Perm region). These yielded a detailed pollen record characterizing the changes in the natural conditions of the transition from the periglacial environment of the Late Glacial period to the interglacial conditions of the Holocene between 14.15 and 10.0 cal ka BP. It was found that open birch woodland with larch existed in the Allerød period (14.15–12.7 сal ka BP) and was replaced by larch forest-steppe during the Younger Dryas (12.7–11.5 cal ka BP). The spread of spruce began in the early Holocene between 11.5 and 10.7 cal ka BP, whereas open larch and spruce woodlands became dominant between 10.7 and 10.0 cal ka BP. Quantitative palaeoclimatic reconstruction reveals that the average temperature of the warmest month (July) and the annual precipitation were considerably lower than modern values. The average July temperature increased from 10 to 16ºС between 14.15 and 12.7 cal ka BP. Then, small fluctuations within 1ºС occurred between 12.7 and 10.0 cal ka BP. The average annual precipitation was 200-300 mm below modern values between 14.15 and 10.7 cal ka BP and reached them only after 10.7 cal ka BP.

Putting down roots: Afforestation and bank cohesion of Icelandic Rivers

AbstractRiparian vegetation is widely recognized as a critical component of functioning fluvial systems. Human pressures on woody vegetation including riparian areas have had lasting effects, especially at high latitude. In Iceland, prior to human settlement, native downy birch woodlands covered approximately 15%–40% of the land area compared to 1%–2% today. Afforestation efforts include planting seedlings, protecting native forest remnants, and acquiring land areas as national forests. The planted and protected nature of vegetation along rivers within forests provides a unique opportunity to evaluate the various taxa within riparian zones and the channel stabilizing characteristics of the vegetation used in afforestation. We investigated bank properties, sediment textures, and root characteristics within riparian zones along four rivers in forests in Iceland. Bank sediment textures are dominantly sandy loam overlying coarser textures. Undercut banks are common because of erosion of the less cohesive subsurface layer. Quantitative root data indicate that the woody taxa have greater root densities, rooting depths, and more complex root structures than forbs or graminoids. The native downy birch has the highest root densities, with <1 mm roots most abundant. Modeling of added bank cohesion indicates that willow provides up to six times and birch up to four times more added cohesion to the coarse sediment textures comprising stream banks compared to no vegetation. We conclude that planting and protecting the native birch and willow helps to reduce bank erosion, especially where long‐term grazing exclusion can be maintained.

Multimillennial fire history of northern Finland along a latitude/elevation gradient

In boreal environments, wildfires are expected to decrease in frequency and/or size with latitude/elevation, mainly in response to climate, as well as fuel availability and type. Furthermore, fire frequency and biomass burned are supposed to have been higher during warm and dry periods of the Holocene (last ∼ 11,000 years). We tested these assumptions in northern Finland by using charcoal analysis to reconstruct Holocene regional fire regimes from eight lake sediment sequences sampled within four different environments in terms of elevation, latitude and vegetation type: (1) low latitude/mid elevation coniferous forests (Pinus sylvestris and Picea abies); (2) mid latitude/low elevation pine forests (Pinus sylvestris); (3) mid-high latitude/elevation transitional mixed forests (Pinus sylvestris and Betula pubescens subsp. tortuosa); and (4) high latitude/elevation birch woodlands (Betula pubescens subsp. tortuosa). As expected, fire frequency decreased with increasing latitude/elevation. Contrary to expectations, fire frequency was not significantly higher in the warm and dry mid-Holocene than in the cool and wet late Holocene, except in transitional mixed forests. Biomass burned was higher in the mid- than in the late Holocene, but only in pine and pine-spruce forests. The opposite was observed in transitional mixed forests and birch woodlands, suggesting that factors other than climate controlled fire regimes in these environments. While climate warming will likely result in more biomass burned in low latitude/elevation coniferous forests, other disturbances (such as insect outbreaks) might play a more important role in high latitude/elevation birch-pine forests and birch woodlands.

Long-term vegetation history of a relict birch forest (Betula pubescens subsp. celtiberica (Rothm. & Vasc.) Rivas Mart.) in the Toledo Mountains (central Iberia). Conservation implications

Understanding ecosystem resilience requires long data series provided by palaeoecological studies, the best tool for reconstructing vegetation dynamics. Here, we analyzed a continuous and well-dated record of pollen, non-pollen palynomorphs, macrocharcoal remains, loss-on-ignition and magnetic susceptibility from one of the most singular peatlands in the Toledo Mountains (central Spain), in order to delineate the anthropogenic and/or climate impact on the peatland and the ecosystem’s response. La Ventilla mire is an isolated site of birch woodland dominated by Betula pubescens subsp. celtiberica (Rothm. & Vasc.) Rivas Mart. This mire, acting as a refugium for this species, is located in Cabañeros National Park and is recognized as ‘Special Area of Conservation’ according to Habitats Directive of the Natura 2000 network. We describe major patterns and trends in the development of this palaeorefugium since the mid-Holocene (∼6145 cal BP) and provide historical context for some natural and/or human-induced dynamics. Around 1500 cal BP, the lotic depositional environment with slow moving backwaters developed into a minerotrophic mire. Until the Middle Ages, macroclimate and autogenic succession appear to have been the main drivers of both local and regional development of vegetation. Between 1500 and 500 cal BP, an abrupt decline in birch cover started, coincident with the Visigothic period. The pronounced peaks in the coprophilous fungi record ca. 1000 and 150 cal BP reflect extensive pastoral activities in the area. This study shows how palaeoecological knowledge helps to explain present patterns in the composition of a valuable protected site, which may be used in prioritizing conservation.

Microscopical palynology: Birch woodland expansion and species hybridisation coincide with periods of climate warming during the Holocene epoch in Iceland.

Introgressive hybridisation between arctic dwarf birch (Betula nana) and European downy birch (B.pubescens) is relatively common in natural woodlands in Iceland. As dwarf birch is a diploid species and downy tree birch a tetraploid species, their hybrids are triploid. In the introgression process, triploid hybrids, which are partially fertile, can backcross with the parental species, producing progenies comprising introgressed diploid, triploid and tetraploid plants. Triploid plants produce both normal triporate pollen (with three pores) and abnormal, aborted pollen, due to dysfunctional meiosis. The type of pollen abnormality that can be detected and quantified is non-triporate pollen (with four or more pores in the pollen wall). We therefore used the presence of non-triporate pollen as a marker to trace birch hybridisation in the past. In the current study we examined fossil pollen in samples from Holocene sediments from three locations: Grímsnes (SW), Eyjafjördur (N) and Thistilsfjördur (NE Iceland). All three peat monoliths had the starting age of 10.3cal. ka BP. Ages were calibrated based on known tephra layers and by radiocarbon dating. The size of Betula pollen grains was measured, and the species proportions calculated from size. Non-triporate grains were detected in samples from all three locations and throughout the Holocene, but with different frequencies. The peaks of intense hybridisation followed birch woodland expansion in two major periods of the Holocene, both coinciding with a warming of climate. The first period occurred in the Early Holocene, around 9.5-7cal. ka BP, when the climate warmed rapidly after deglaciation. The second period occurred around 5-3.5cal. ka BP, well within the mid-Holocene Northern Hemisphere warming. A new wave of birch hybridisation appears to have started in the last few decades as the climate has warmed. Birch woodlands are likely to become more widespread. Introgressed shrub birch is likely to be more competitive over dwarf birch.

Phytocenotic conditions and structure of the local population for Betula humilis Schrank near Zhornyska village (Ukrainian Roztochchia)

hytocoenotic conditions and structure of the local population for Betula humilis in the north-eastern environs of the village Zhornyska, Yavoriv district, Lviv region, on the territory of the Roztochchia International Biosphere Reserve have been studied. Four coenopopulations (CP) of the species are confined to secondary plant communities of sicaciogenic and pyrogenic successions with different sod levels of the peat soil, as well as missing or unequally expressed tree layer. The least transformed communities with the dominance of B. humilis (40-80% p.c.) in the shrub layer and no stands in terms of floristic composition and spatial structure correspond to the derived mesohygrophytic and hygromesophytic variants of the association Betuletum humilis Steffen 1931. The most transformed areas with sparse tree layer are represented by pioneer forest communities - birch woodlands. Seventy-five species of higher plants (seventy vascular plants and five bryophytes) were found in the floristic composition of phytocenoses. The minimal participation of helophytes and the presence of invasive species indicate a high level of mesophytization and synanthropization of modern phytocenoses. Within the locality B. humilis forms different in area and density of formation shoots (turions) of the colony-curtain mainly from semi-autonomous subpartial bushes 0.3-2.2 m tall. The largest curtains (up to 300 m2) with a high density of living formation shoots (up to 293 pcs/m2) are confined to open well-lit areas. The age of old skeletal axis, not exceeding 9 years was determined and the annual growth of shoots has been calculated. The parameters of seed productivity (SP) of the local population of B. humilis vary within: potential SP - 89.48–109.24 seed germs, actual SP - 80.84–100.4 seeds. The coefficient of seed productivity is quite high (86.69-92.16%) for all coenopopulations. Based on the results of research and analysis of the literature the life form of B. humilis, which belongs to vegetatively mobile hypogeogenic-geoxyl deciduous shrubs that form colonies or clones of (semi) autonomous (sub) partial (daughter) shrubs and are characterized by monopodial-sympodial shoots growth has been clarified. The big life cycle of the species characteristic of shrubs consists of development cycles for systems shoots formation (main skeletal axes), which are successively replaced, and lasts for decades. The development cycle of the system formation shoot covers the periods of intensive growth (appearance of formation shoot from an additional or dormant bud in the first year), relative stabilization of growth processes with the formation of first and higher-order branching shoots (from second to tenth years) and ageing and death of shoots (after about ten years of age).

The content of nutrients, lignin and cellulose in plants and lichens in the forest-tundra ecotone of the Khibiny mountain massif

The results of studies of the chemical composition of plants and lichens in the altitude gradient on the slope of Yumechorr of the Khibiny mountain massif (Murmansk region) are presented. The species specificity of the accumulation of macro- and microelements by the assimilating organs of plants and lichens in the in the main altitude zones is shown. The leaves of Betula pubescens and Vaccinium myrtillus are the most rich of elements of mineral nutrition. Lichens are characterized by a low content of N, Ca, K, P, Mg, S, as well as Zn and Mn and high - Fe, Cu, Ni. In spruce and pine needles, similar patterns of the distribution of elements by age classes were revealed. Changes in the content of nitrogen, mineral elements, secondary metabolites in the altitude gradient in the assimilating organs of plants and lichens, during the transition from the forest belt to the mountain forest, have been established. It has been established that with increasing growth height, the N content increases in Pinus sylvestris needles, in the leaves of Arctostaphyllos uva-ursi, in the leaves of the current year Empetrum hermaphroditum. Plants growing in the mountain tundra and forest tundra are characterized by a high content of K. The Zn content also increases with increasing absolute height in the conifers/leaves of P. sylvestris, B. pubescens, V. uliginosum. During the transition from the forest belt to the mountain tundra, the content of Ca and Mg decreases in plant leaves. In the leaves of E. hermaphroditum, minimal concentrations of Mn were also detected in the mountain tundra. The content of lignin and cellulose in the leaves of shrubs, with the exception of V. myrtillus, in the belt of coniferous forests is lower than in the belt of birch forests and tundra. The content of lignin in the leaves of B. nana and B. pubescens increases, and cellulose practically does not change with an increase in absolute height in the Khibiny Mountains. Accumulation of lignin is observed in needles of P.sylvestris in the belt of birch woodlands.

Conservation genetics of montane willow populations in Scotland—limited natural recovery despite long-distance gene flow and high genetic diversity

Plant species around the world are negatively affected by habitat fragmentation and climate change. Montane willow populations in the UK have declined primarily due to grazing, as well as climate change and muirburn in certain areas. Only small, isolated populations remain, scattered across steep ledges where shrubs escape most grazing animals. We explored the genetic effects of habitat fragmentation on gene flow and genetic diversity in the largest remaining patches in the UK, which lie in Scotland, for two now restricted and rare montane willow species—Salix myrsinites and Salix lapponum. Using ten microsatellite loci and an almost complete genetic inventory in the central Cairngorms area (S. myrsinites n = 186, S. lapponum n = 91) we showed that genetic diversity (heterozygosity and allelic richness) is relatively high in both species, particularly high for the decaploid S. myrsinites, and clonal reproduction low. Historic gene flow between populations could be demonstrated. Significant inbreeding was detected in both species and observed seed set and numbers of juveniles in the field are low, possibly indicating signs of inbreeding depression. Both species have extremely low numbers of individuals at each site, with many being smaller than ten, and in some cases combined with skewed sex-ratios (mainly female biased). This will likely cause more severe reproductive failures in the next generations unless population numbers are increased. Reinforcing populations of both species under low grazing pressure with new, unrelated individuals, as well as creating new stepping-stone populations will be necessary to help the recovery of these species. Results from this study will inform restoration work in Scotland aiming to create continuous woodland habitats from pinewoods at lower altitudes through to higher altitude downy birch woodlands merging with montane willows.

Lateglacial and Early Holocene palaeoenvironmental change and human activity at Killerby Quarry, North Yorkshire, UK

ABSTRACTThe hunter‐gatherers that entered the British peninsula after ice‐retreat were exploiting a dynamic, rapidly changing environment. Records of vegetation change and human occupation during the Lateglacial to Early Holocene in northern Britain are more commonly found at upland and cave sites. However, recent research highlights many areas of the Swale–Ure Washlands that preserve extensive environmental sequences in low‐lying ice‐wastage basins, channels and depressions. The Lateglacial–Early Holocene environment of Killerby Quarry, North Yorkshire, is investigated here using a multi‐proxy approach of sedimentary ancient DNA (sedaDNA), pollen, sedimentological (geochemistry and portable optically stimulated luminescence), and rare and well‐preserved archaeology (Lavvu structures and lithics). Results show that the wetland basins and kettleholes were small lakes or ponds in the Lateglacial surrounded by sedge‐fen and birch woodland. A gradual (centennial scale) succession to reed‐swamp and then marsh is seen by the Early Holocene. This environment formed the resource‐scape for hunter‐gatherer transitory settlement in both the Lateglacial (Late Upper Palaeolithic) and Holocene (Early Mesolithic), attracted by the rich communities of pond‐related flora and fauna as well as easy strategic landscape access by way of the River Swale, an arterial route through the landscape connecting the North Sea Basin with the Pennine uplands via the palaeolakes around Killerby.

The influence of vegetation cover on the grain-size distributions and thicknesses of two Icelandic tephra layers

Grain-size distributions and thicknesses of tephra layers are used to reconstruct characteristics, dynamics, and hazards of explosive volcanic eruptions, but the extent to which the preservation of tephra is influenced by depositional environments is unclear. This paper analyses grain-size distributions and thicknesses of tephra layers produced by the Eyjafjallajökull (2010) and Grímsvötn (2011) eruptions. We collected 110 tephra samples and layer thickness measurements from 86 sites at two locations in southern Iceland. Areas of different vegetation cover have varying capacities to affect rates of tephra erosion, retain fallout, or capture remobilised tephra. The Grímsvötn tephra was somewhat coarser-grained and thicker in areas of birch woodland than in adjacent moss heath, but no comparable differences in the Eyjafjallajökull tephra were observed. The spatial variability (over tens of metres) of median particle-size and layer thickness is low, providing confidence that relatively few samples and measurements may be required to capture fallout characteristics.

Insect herbivory increases from forest to alpine tundra in Arctic mountains.

Current theory holds that the intensity of biotic interactions decreases with increases in latitude and elevation; however, empirical data demonstrate great variation in the direction, strength, and shape of elevational changes in herbivory. The latitudinal position of mountains may be one important source of this variation, but the acute shortage of data from polar mountains hampers exploration of latitude effects on elevational changes in herbivory. Here, we reduce this knowledge gap by exploring six elevation gradients located in three Arctic mountain ranges to test the prediction that a decrease in herbivory occurs with increasing elevation from forest to alpine tundra. Across the 10 most abundant evergreen and deciduous woody plant species, relative losses of foliage to insect herbivores were 2.2‐fold greater at the highest elevations (alpine tundra) than in mid‐elevation birch woodlands or low‐elevation coniferous forests. Plant quality for herbivores (quantified by specific leaf area) significantly decreased with elevation across all studied species, indicating that bottom‐up factors were unlikely to shape the observed pattern in herbivory. An experiment with open‐top chambers established at different elevations showed that even a slight increase in ambient temperature enhances herbivory in Arctic mountains. Therefore, we suggest that the discovered increase in herbivory with elevation is explained by higher temperatures at the soil surface in open habitats above the tree line compared with forests at lower elevations. This explanation is supported by the significant difference in elevational changes in herbivory between low and tall plants: herbivory on low shrubs increased fourfold from forest to alpine sites, while herbivory on trees and tall shrubs did not change with elevation. We suggest that an increase in herbivory with an increase in elevation is typical for high‐latitude mountains, where inverse temperature gradients, especially at the soil surface, are common. Verification of this hypothesis requires further studies of elevational patterns in herbivory at high latitudes.

Tree line shifts, changing vegetation assemblages and permafrost dynamics on Galdhøpiggen (Jotunheimen, Norway) over the past ~4400 years

An environmental reconstruction based on palynological evidence preserved in peat was carried out to examine late-Holocene alpine tree line dynamics in the context of past climatic changes on Galdhøpiggen (Jotunheimen, southern Norway). We analysed a peat core taken from a mire at the present-day tree line (1000 m a.s.l.), c. 450 m downslope from the lower limit of sporadic permafrost. We adopted a combination of commonly used indicators of species’ local presence to reconstruct past vegetation assemblages, such as the relative pollen abundance (%), pollen accumulation rate (PAR), and presence of indicator species. Additionally, fossil pollen from the peat sequence was compared to modern pollen from a surface moss polster to establish a modern analogue. The results were compared with studies covering the late-Holocene climatic changes in the area. The reconstruction demonstrates that a pine-dominated woodland reached above the present-day tree line at c. 4300 cal. yr BP, suggesting a warmer climate suitable for Scots pine ( Pinus sylvestris) growth at this altitude. Scots pine retreated to lower altitudes between c. 3400 and 1700 cal. yr BP, accompanied by the descent of the low-alpine shrub-dominated belt, in response to cooling climatic conditions. The colder period covered c. 1700–170 cal. yr BP, and an open downy birch ( Betula pubescens) woodland became widespread at 1000 m a.s.l., whilst pine remained sparse at this altitude. From c. 170 cal. yr BP onwards, warming allowed pine to re-establish its local presence alongside downy birch at 1000 m a.s.l.

Resources of birch trees and their productivity for honey collection in conditions of the Leningrad region

The Leningrad Oblast has a rich food base for bees on forest land. Still, currently, there is no regulatory basis for assessing the honey resources of birch forest land at the regional level. Therefore, forest areas with woody, shrubby or herbaceous plants as part of the woody, shrubby or herbaceous layer are used as a forage base for bees. The birch forests of the Leningrad region are the second largest in terms of the area covered. The research aims to carry out an inventory of honey resources and determine honey productivity for the primary honey plants under the birch canopy and forest edges. We used a proven survey methodology for counting plants of the understorey at the experimental sites. The study presented 71 species from 31 families of melliferous plants of blueberry, wormwood and herb-meadow birch forests. Significant melliferous plants under the birch canopy are Aegopodium podagraria L. (herb-twine and sagebrush birch, 57 kilograms/hectare); Vaccinium myrtillus L. (birch bilberry and acidic birch, 27 kilograms/hectare); Veronica chamaedrys L. (acidic birch, 24 kilograms/hectare). Rubus idaeus L. (107 kg/ha) has maximum honey production in the forest margins. The honey yield of Frangula Alnus Mill. and Chamaenerion angustifolium (L.) Scop is 50-60 kg/ha; the honey yield of Trifolium medium L. is 32 kg/ha. The evaluation of the birch woodlands showed that the studied components of the forest phytocenosis are characterized by a significant number of honey-bearing plant species that have a wide range of honey productivity.

Long‐term exclosure of sheep‐grazing from an ancient wood: Vegetation change after a sixty‐year experiment

AbstractQuestion: An ancient woodland site with a long history of coppicing and heavy grazing was protected from domesticated stock in 1955. Results of a vegetation‐monitoring experiment were subsequently published in 1983. This study followed up the original research to investigate whether observed trends were as predicted. These included a shift in tree species composition in favour of shade‐tolerant species, beech (Fagus sylvatica) and rowan (Sorbus aucuparia), at the expense of light‐demanding birch (Betula spp.) and oak (Quercus petraea agg.), and progress towards a typical woodland ground flora.Location: Peak District National Park, United Kingdom.Methods: The mixed oak–birch woodland was re‐surveyed in 2011. Two enclosures (1955 and 1980s) and an unenclosed control area were investigated. Overstorey structure and composition was assessed by measuring canopy openness and the girths of all trees and saplings. Herb layer species composition was also recorded in 28 vegetation plots.Results: We demonstrated a progressive decline in the number of mature oaks and birch in the old enclosure although they still regenerated successfully. Only a few individuals of beech and rowan appeared. Herb layer species composition differed between the subareas but since the 1980s, the temporal change in the old enclosure was negligible. The new enclosure followed a similar pattern in both canopy and herb layer as observed in the early years in the old enclosure. However, the control subarea had no regeneration of woody species and limited ground flora.Conclusions: After nearly 60 years, the replacement of light‐demanding dominants by shade‐tolerant trees was still limited, probably by low pH and stable light conditions. The findings are pertinent to the impacts of large herbivore grazing (domestic stock or wild) on woodland dynamics.

Biogeochemical and photobiological responses of subarctic lakes to UV radiation

Solar ultraviolet radiation (UV) induces photodegradation of optically and functionally important organic compounds in lakes and may negatively impact aquatic biota. We disentangled UV impacts on dissolved organic matter (DOM) transformation, and algal and zoobenthic micro-organisms in two shallow subarctic lakes in NW Finnish Lapland; in a high-UV + low-DOM (tundra, Iso-Jehkas) and a low-UV + high-DOM (mountain birch woodland, Mukkavaara) system. In addition to site and seasonal comparisons, in situ experiments with three treatments (DARK, photosynthetically active radiation [PAR], UV + PAR) were set up floating on the lakes for four weeks during midsummer. Lake water and experimental lake water were analyzed for basic limnology, optical properties (dissolved organic carbon [DOC], specific UV absorbance [SUVA], colored DOM [CDOM], and DOM compounds) as well as for photosynthetic and photoprotective pigments in algae and microzoobenthos. DOC concentrations remained largely unchanged after the exposure period in seasonal and experimental samples in both lakes yet the biochemical composition of the carbon pools was distinctly altered. CDOM and SUVA decreased seasonally and under UV exposure in the experiments, and terrestrial DOM compounds decreased in the experiments, suggesting UV induced photodegradation of large molecular size DOM of terrestrial origin. Higher seasonal and experimental (UV + PAR vs. PAR) proportional CDOM degradation occurred in Iso-Jehkas (32%, 29%) than in Mukkavaara (19%, 9%). Accordingly, the high-UV + low-DOM lake was more sensitive to photodegradation despite originally low CDOM relative to the low-UV + high-DOM system where DOM biodegradation likely prevailed. Experimental results showed elevated algal carotenoid/chlorophyll ratios and microzoobenthic melanin under UV exposure indicating photoinhibition and photoprotective pigmentation. UV has a significant impact on aquatic food webs of subarctic lakes altering the biogeochemical composition of organic matter and organisms through mechanisms of photodegradation, photoinhibition and photoprotection.

Late Glacial-early holocene vegetation and environmental changes in the western Iberian Central System inferred from a key site: The Navamuño record, Béjar range (Spain)

A new record from a long sediment core (S3) in Navamuño (1505 m asl, western Iberian Central System) provides the reconstruction of the vegetation history and environmental changes in the region between 15.6 and 10.6 ka cal BP, namely during the Late Glacial and the early Holocene, using a multiproxy analysis (pollen-based vegetation and climate reconstruction, sedimentary macrocharcoals, loss-on-ignition, magnetic susceptibility and X-ray fluorescence (XRF) measurements). The results are then compared with other sequences from the Iberian Central System and the whole Iberian Peninsula in order to better understand the past dynamics of the main forest constituents. The pollen record shows a shift from open pine forests ∼15.6–14.7 ka cal BP (Oldest Dryas) to mixed open pine-birch woodlands ∼14.7–14.0 ka cal BP (Bølling). Woodlands were succeeded by a steppe-like landscape until ∼13.4 ka cal BP (Older Dryas), which was replaced again by high-mountain pine forests and riparian woodlands ∼13.4–12.6 ka cal BP (Allerød). A great development of cold steppe grasslands linked to the decline of birch woodlands is documented ∼12.6–11.7 ka cal BP (Younger Dryas). The early Holocene (11.7–10.6 ka cal BP) was characterized by a progressive reforestation of the study area by pine and birch forests in the highlands and oak woods in the lowlands. Temperate tree taxa (Carpinus betulus, Castanea sativa, Corylus avellana, Fraxinus, Juglans, Tilia, and Ulmus) were also common but likely at lower elevations. Pollen of Fagus sylvatica was already recorded during the Late Glacial and the early Holocene. The marked increasing local fire activity during the warmer and wetter Allerød oscillation could be related to a rise in tree cover, supporting the climatically driven character of these fires. Nevertheless, the strong increase in fire activity during the Younger Dryas would probably be related to growing tree and shrub mortality, as well as to the wet/dry biphasic structure of this stadial. The standard “Modern Analogue Technique” has been also applied to the Navamuño sequence to provide quantitative climate estimations for the Late Glacial and the early Holocene periods. This record is one of the few continental archives that show the climatic trend between the Late Glacial and the early Holocene in central Iberia, agreeing with many other regional records from the Western Mediterranean.

Соотношение природных и антропогенных факторов в развитии ландшафтов бассейна реки Раздольная, Приморье

Landscapes’ development in the Razdolnaya River Basin in the Starorechensky hillfort vicinity was reconstructed. Fragmentary data for the middle Holocene phase (~5.9 cal. ka) were obtained, in detail the reconstruction was carried out for the last 2.5 cal. ka. The development of landscapes took place in contrasting climatic conditions, moisture changed the most strongly. Five stages of the valley development under different humidity were reconstructed. The sections include buried soil formed in the droughty period in the second half of the late Holocene. At this time, steppe sagebrush, mixed herbs grasslands and birch woodlands were widespread. Climate in the late 7th-10th centuries gradually became warmer and more humid. Decrease of the temperature, with high humidity in the Little Ice Age with a constant renewal of the substrate on the floodplain during floods, led to an increase in areas occupied by Betula ovalifolia communities. The role of Pinus densiflora and birches increased in the mountain forests. Correlation of paleogeographic events with regional data is carried out. The role of the anthropogenic factor in the development of landscapes during the settlement of the valley by the Bohai agriculturalists, the first settlers of the 19th-beginning of 20th centuries and the development of modern agro-complexes was analyzed.