Altitudinal zonation of human-disturbed vegetation on Mt. Tianmu,eastern China

Much of the primary vegetation at low altitudes has been greatly altered or destroyed by a long history of human activities. This is particularly true in eastern China, where low-altitude areas are now dominated by secondary forests or plantations. Altitudinal vegetation zonation of this region is often based on these secondary forests, resulting in seral vegetation with an obscure zonal sequence. Here, we deduced the potential climax vegetation according to the regeneration patterns of the dominant species of the secondary forests at low altitudes (below 1,000 m a.s.l.) on Mt. Tianmu (1,506 m a.s.l., 30°18′30″–30°21′37″N, 119°24′11″–119°27′11″E). Based on the potential climax vegetation combined with the floristic composition and community structure, three vegetation zones were identified, viz: (1) evergreen broad-leaved forest zone (400–950 m a.s.l.); (2) evergreen and deciduous broad-leaved mixed forest zone (950–1,100 m a.s.l.); (3) deciduous broad-leaved forest zone (1,100–1,506 m a.s.l.). The altitudinal vegetation zones identified in this study correspond with the thermal conditions on Mt. Tianmu. The distribution of vegetation on Mt. Tianmu was limited by lower temperatures in winter, and the altitudinal thermal vegetation zones on this mountain were more similar to the thermal vegetation of Japan than to that of China. The vertical distributions and roles of conifers were different between the eastern and the western regions along 30°N latitude in humid East Asia. Cryptomeria fortunei formed the emergent layer, towering above the broad-leaved canopy at middle altitudes as C. japonica on Yakushima, but disappeared at high altitudes with hydrothermal limitation on Mt. Tianmu.     

Morphological variations of the Solidago virgaurea L. complex along an elevational gradient on Mt Norikura,central Japan

Morphological variations in vegetative and reproductive organs in the Solidago virgaurea complex were examined for eight elevations between 1600 and 2400 m a.s.l. in Japan. The rosette diameter and stem height were lower at higher elevations. The stem diameter at any stem height was greater at higher elevations, suggesting that the S. virgaurea complex increases mechanical stiffness against strong wind at high elevations. The number of flower heads at any stem height was less at high elevations (2000–2400 m a.s.l.) than at low elevations (1600–1900 m a.s.l.). Leaf nitrogen concentration did not change along the elevational gradient. Leaf mass per area (LMA) tended to decrease with increasing elevation, except for 2400 m a.s.l. The decrease of LMA would contribute to maintaining a positive carbon balance at high elevations. The number of involucral rays of flower heads was mostly four at low elevations (1600–1900 m a.s.l.) and three at high elevations (2000–2400 m a.s.l.). The number of involucral scales and diameter of flower heads were greater at high elevations (2000–2400 m a.s.l.) than at low elevations (1600–1900 m a.s.l.). Therefore, the S . virgaurea complex is suggested to adapt to high elevations that have cool temperature, a short growing season and strong wind conditions by changing its vegetative and reproductive traits.     

Similarities between predator mite populations (Acari: Gamasina) from natural forests in the Bucegi Massif,Romania

Ecological research of gamasid mites was carried out in three natural forest ecosystems with Picea abies (1350 m a.s.l.), Abies alba (950–1000 m a.s.l.) and Fagus sylvatica (1200 m a.s.l.) situated in the Bucegi Massif, Southern Carpathians, Romania during 2001–2003. In the studied forest ecosystems, the taxonomic structure of gamasids was represented by 11 families (Epicriidae, Parasitidae, Veigaiidae, Ameroseiidae, Aceosejidae, Rhodacaridae, Macrochelidae, Pachylaelapidae, Laelapidae, Eviphididae and Zerconidae), with 39 genera and 97 species. The maximum number of species was recorded in the ecosystem with Abies alba (80), followed by the ecosystem with Fagus sylvatica (73), while the minimum in the ecosystem with Picea abies (68). 2,016 samples, 97 species with 23,441 individuals were analysed. In order to show similarities between predator mite populations from these areas, the vegetation and some abiotic parameters of the soil (temperature, humidity, pH) were analysed and described. Similarities between gamasid mite populations from the investigated ecosystems were analysed using the Jaccard index (q). The highest similarity index (q = 0.706) was recorded between gamasids identified in Picea abies and Abies alba forests, at soil level, in comparison with those from Abies alba and Fagus sylvatica forests (q = 0.656). Based on the similarity index, it is discussed that the gamasid population structure was influenced by the type of soil, the specific composition of the herbaceous, shrub and tree layers, the microclimatic factors, all characteristic for each studied ecosystem.     

Early Pleistocene vegetation change in upland south‐eastern Australia

Aim This study aims to improve our understanding of the late Cenozoic history of Australian rain forest and sclerophyll biomes by presenting a detailed pollen record demonstrating the floristic composition and orbital‐scale patterns of change in forest communities of upland south‐eastern Australia, during the Early Pleistocene. The record is examined in order to shed light on the nature of the transition from rain forest‐dominated ‘Tertiary’ Australian vegetation to open‐canopied ‘Quaternary’ vegetation. Location Stony Creek Basin (144.13° E, 37.35° S, 550 m a.s.l), a small, infilled palaeolake in the western uplands of Victoria, Australia. Methods A c. 40‐m‐long sediment core was recovered from the infilled palaeolake. Palynology was used to produce a record of changing vegetation through time. Multivariate analyses provided a basis for interpreting the composition of rain forest and sclerophyll forest communities and for identifying changes in these communities over successive insolation cycles. Results Early Pleistocene upland south‐eastern Australian vegetation was characterized by orbital‐scale, cyclic alternation between rain forest and sclerophyll forests. Individual intervals of forest development underwent patterns of sequential taxon expansion that recurred in successive vegetation cycles. Diverse rain forests included a number of angiosperm and gymnosperm taxa now extinct regionally to globally. Sclerophyll forests were also diverse, and occurred under warm and wet climate conditions. Main conclusions The Stony Creek Basin record demonstrates that as recently as c. 1.5 Ma diverse rain forests persisted in southern Australia beyond the modern continental range of rain forest. The importance of conifers in these rain forests emphasizes that they have no modern Australian analogue. Alternation in dominance between these forests and diverse, sclerophyllous open canopied forests was apparently driven by changes in seasonality, and may have been promoted by fire.     

Avian Density and Nest Survival on the San Pedro River: Importance of Vegetation Type and Hydrologic Regime

Abstract: Lowland riparian vegetation in the southwestern United States is critically important for maintaining a high richness and density of breeding birds. Further investigation is needed within riparian corridors, however, to evaluate the relative importance of vegetation type and hydrologic regime for avian density and nest survival as targets for regional conservation or restoration efforts. We estimated the densities of 40 bird species and for species grouped on the basis of nest height and dependence on surface water in gallery cottonwood–willow (Populus spp.–Salix spp.) forests, saltcedar (Tamarix spp.) shrub lands, and terrace vegetation types along a gradient in the hydrologic regime of the San Pedro River, Arizona, USA. We also assessed nest survival for shrub-nesting insectivores and herbivores. Canopy-nesting birds as a group and 14 individual bird species reached their greatest densities in cottonwood forests regardless of the hydrologic regime. Water-dependent birds as a group reached their highest density in both intermittent- and perennial-flow cottonwood stands, but certain species occurred almost exclusively in perennial-flow sites. Two shrub-nesting species and the brown-headed cowbird (Molothrus ater) were most abundant in saltcedar shrub lands, and the brown-headed cowbird was most abundant in saltcedar stands with intermittent flows. Mesquite (Prosopis spp.) and big sacaton (Sporobolus wrightii) grassland each maintained the highest densities of certain species within ≥1 hydrologic regime. Shrub-nesting insectivores had the greatest nest survival in cottonwood, including Arizona Bell's vireo (Vireo bellii arizonae), and also had lower proportions of nests parasitized and preyed upon, although 95% confidence intervals among vegetation types overlapped. Nest survival for both shrub-nesting insectivores and herbivores was lowest in intermittent-flow saltcedar, although, again, confidence intervals overlapped. Nest survival was lower in parasitized than nonparasitized nests in mesquite and across vegetation types for Arizona Bell's vireo and in cottonwood for Abert's towhee (Pipilo aberti). Riparian management that maintains heterogeneous riparian vegetation types, including floodplain vegetation comprising cottonwood–willow gallery riparian forests with some stretches of perennial flow, are important for maintaining the high diversity and abundance of breeding birds on the San Pedro River and probably across the region. Cottonwood stands also appear to maintain highest nest survival for some shrub-nesting birds.     

Tree population dynamics,stand structure and species composition in the montane virgin forest of Vallibäcken,northern Sweden

The population dynamics of Betula pubescens and Picea abies in a boreal forest near Kvikkjokk, northern Sweden, are governed by a process of storm gap regeneration similar to the gap regeneration described for boreo-nemoral forests. Cumulative age distribution curves, interpreted as static survivorship curves, lead to a simple theory of differential survival based on properties of the species, i.e. shade tolerance and relative growth rate. The theory is sustained by diameter and height distributions and by the spatial distributions of logs and of trees in different life-phases. Species of the field and ground layers respond differentially to gap formation and the ensuing successional stages. Browsing by moose (Alces alces) may prevent tree species, mainly Sorbus aucuparia, Betula pubescens and Pinus sylvestris, from developing into a tree layer. The regeneration ability for tree species growing in a stand at 460 m a.s.l. is limited compared with the regeneration at 330 m a.s.l., and typical storm gap formation involving more than one tree seems to occur rarely if at all, while overthrown trees with exposed rootplates are uncommon. Spruce at 460 m a.s.l. shows also a lower growth rate and a lower height/diameter ratio compared to the lower situated stands.     

Sensitivity of Siberian larch forests to climate change

The Northern Hemisphere's boreal forests, particularly the Siberian boreal forest, may have a strong effect on Earth's climate through changes in dominant vegetation and associated regional surface albedo. We show that warmer climate will likely convert Siberia's deciduous larch (Larix spp.) to evergreen conifer forests, and thus decrease regional surface albedo. The dynamic vegetation model, FAREAST, simulates Russian boreal forest composition and was used to explore the feedback between climate change and forest composition at continental, regional, and local scales. FAREAST was used to simulate the impact of changes in temperature and precipitation on total and genus‐level biomass at sites across Siberia and the Russian Far East (RFE), and for six high‐ and low‐diversity regions. Model runs with and without European Larch (Larix decidua) included in the available species pool were compared to assess the potential for this species, which is adapted to warmer climate conditions, to mitigate the effects of climate change, especially the shift to evergreen dominance. At the continental scale, when temperature is increased, larch‐dominated sites become vulnerable to early replacement by evergreen conifers. At the regional and local scales, the diverse Amur region of the RFE does not show a strong response to climate change, but the low‐diversity regions in central and southern Siberia have an abrupt vegetation shift from larch‐dominated forest to evergreen‐conifer forest in response to increased temperatures. The introduction of L. decidua prevents the collapse of larch in these low‐diversity areas and thus mitigates the response to warming. Using contemporary MODIS albedo measurements, we determined that a conversion from larch to evergreen stands in low‐diversity regions of southern Siberia would generate a local positive radiative forcing of 5.1±2.6 W m^?2. This radiative heating would reinforce the warming projected to occur in the area under climate change.     

Ground vegetation in the Mongolian taiga forest‐steppe ecotone does not offer evidence for the human origin of grasslands

Question: Is the vegetation of meadow and mountain steppes distinct from the ground vegetation of light taiga forests in the transitional zone between these biomes? Location: Western Khentey Mountains, northern Mongolia. Methods: Vegetation was recorded from 100‐m² plots from all dominant types of light taiga forest and dry grassland. Distinctness of ground vegetation was studied with Detrended Correspondence Analysis (DCA). Results: Ground vegetation in the light taiga was significantly different from the herbal vegetation of meadow and mountain steppes. Clear separation was only absent for the Car ex amgunensis meadow steppes that occur in a narrow strip along the forest edge and are partly shaded by trees. Forest and steppe communities followed a moisture gradient according to the DCA ordination with light taiga forests at the moistest sites and steppe communities at the driest sites. Ulmus pumila open woodlands diverged from this pattern, because of their close spatial and phytosociological relationship to mountain steppes. Conclusions: The present results do not support the assumption that grasslands in Mongolia's transitional zone between forest and steppe would generally resemble the ground vegetation of light taiga forests. This contradicts a published hypothesis stating that the vegetation of meadow and mountain steppes would not clearly differ from ground vegetation of light taiga forests in the forest‐steppe transitional zone of Mongolia.     

Palynological investigations on vegetation and climate change in the Late Quaternary of Lake Rukche area,Gorkha Himal,Central Nepal

Palynological data and pedological investigations including stable isotopes and lignin biomarkers (Glaser et al. in press) from a 4 m core of Lake Rukche (3500 m a.s.l.) enhance our palaeoecological knowledge of the time since the LGM in the Gorkha Himal, Central Nepal. Even before 15000 B.P. forest types became established which prove the existence in Central Nepal of a temperate-humid climate with a considerable amount of winter and spring precipitation from westerly disturbances. Lignin input and pollen data point to a patchy vegetation cover around Lake Rukche with meadow-steppes dominated by Poaceae. Around 15000 B.P. Quercus and Pinus roxburghii dominated the lower altitudes while the vegetation around Lake Rukche was more steppe-like (Chenopodiaceae, Artemisia). Subsequently the climate became warmer and drier as winter and spring precipitation decreased while summer rain remained low. Later on more resource-demanding forests became established under improved temperature and precipitation conditions (Engelhardia). Around Lake Rukche coniferous forests (Abies, Picea) occurred beside meadow-steppes. The transition from the Pleistocene to the Holocene is not recorded. In the Holocene alpine Kobresia-meadows stabilised the soil surface causing sand accumulation to end. During the mid-Holocene (7800–2750 B.P.) humid oak forests with demanding elements (Ilex, Coriaria, Myrsine and Engelhardia) dominated the vegetation cover. A charcoal layer and a marked emergence of fire-induced communities with Pinus roxburghii, Poaceae, Ericaceae and Pteridium are proofs of a first strong anthropogenic change in vegetation which coincided with the climatic deterioration at the onset of the Subatlantic. Since 900 B.P. grazing pressure and the frequency of fires increased, resulting in a replacement of Betula utilis-forests by meadows and woods of Juniperus and Rhododendron. While previous anthropogenic influence increased the biodiversity by promoting replacement communities, recent developments have led to a decrease in biodiversity through loss of natural vegetation communities.     

Variation in net primary productivity and biomass of forests in the high mountains of Central Himalaya

Abstract. This study describes the biomass and net primary productivity of the forests of Central Himalaya occurring in areas where vegetation ranges from close-canopy broad-leaved forest to stunted open-canopy timberline vegetation. The forests studied were Acer cappadocicum forest at 2750 m, Betula utilis forest at 3150 m, and Rhododendron campanulatum forest at 3300 m altitude in Central Himalaya. With the rise in altitude the forest biomass decreased from 308.3 ton/ha in Acer forest to 40.5 ton/ha in Rhododendron forest. The decrease in net primary productivity was less steep, from 19.6 ton/ha/yr in Acer forest to 10.0 ton/ha/yr in Rhododendron forest. The production efficiency of leaves (net production per unit leaf weight) in these forests is higher than in low altitude broad-leaved forests of Central Himalaya, i.e. from 2.89 in Acer forest to 3.41 g net production/g leaf biomass/yr, against 0.81-1.55 at lower altitudes.     

Montane Andean rain forests are a global diversity hotspot of geometrid moths

Aim Andean forests are known to be a major diversity hotspot for vascular plants and vertebrates, but virtually nothing is known about the diversity of arthropods. We examined whether montane rain forests in southern Ecuador are also a diversity hotspot for arthropods, and chose geometrid moths as a model group. Location The study area in southern Ecuador (Province Zamora‐Chinchipe, 79° W, 04° S) covers c. 40 km², with 39 collecting sites within an elevational range of 1040–2677 m a.s.l. Thirty‐five of the sites were situated in an area c. 2.5 km². Additional qualitative sampling was carried out in the same area and up to an elevation of 3100 m. Methods Nocturnal moths were collected quantitatively and qualitatively using portable light towers consisting of two 15 W fluorescent tubes, and diurnal moths were collected qualitatively using an insect net. Insects were sampled in six fieldwork periods in the years 1999–2003. As diversity measures, Fisher's alpha of the log‐series distribution as well as eight estimators of total species richness were applied. Results A total of 1266 species were recorded, 63% of which were identified to named species, whereas the remainder are likely to include many undescribed species. Quantitative samples at light towers collected 35,238 specimens representing 1223 species. The extrapolated species number for these data is 1420 (incidence coverage estimator). Twenty‐one additional nocturnal species and 22 exclusively diurnal species were sampled qualitatively at elevations between 1040 and 3100 m. The pooled value of Fisher's alpha for all quantitative samples is 246 ± 3. Main conclusions The diversity of Geometridae documented here is much higher than anywhere else in the world, even without the inclusion of additional species from adjacent lowland rain forests. The number of recorded species in this small area corresponds to more than 6% of the known world fauna of geometrid moths. Our study emphasizes the importance of protecting the remaining montane Andean rain forests. For setting priorities in conservation, more studies on insect diversity are urgently required in other regions of the Andes, since montane forests are being destroyed at an alarming rate.     

Characteristics of the Psidium cattleianum invasion of secondary rainforests

Strawberry guava (Psidium cattleianum) is a shade‐tolerant shrub or small tree invader in tropical and subtropical regions and is considered among the world's top 100 worst invasive species. Studies from affected regions report deleterious effects of strawberry guava invasion on native vegetation. Here we examine the life history demographics and environmental determinants of strawberry guava invasions to inform effective weed management in affected rainforest regions. We surveyed the vegetation of 8 mature rainforest and 33 successional sites at various stages of regeneration in the Australian Wet Tropics and found that strawberry guava invasion was largely restricted to successional forests. Strawberry guava exhibited high stem and seedling densities, represented approximately 8% of all individual stems recorded and 20% of all seedlings recorded. The species also had the highest basal area among all the non‐native woody species measured. We compared environmental and community level effects between strawberry guava‐invaded and non‐invaded sites, and modelled how the species basal area and recruitment patterns respond to these effects. Invaded sites differed from non‐invaded sites in several environmental features such as aspect, distance from intact forest blocks, as well as supported higher grass and herb stem densities. Our analysis showed that invasion is currently ongoing in secondary forests, and also that strawberry guava is able to establish and persist under closed canopies. If left unchecked, strawberry guava invasion will have deleterious consequences for native regenerating forest in the Australian Wet Tropics.     

The subalpine vegetation of Mt. Vysokaya, central Sikhote-Alin

The subalpine vegetation structure of Mt. Vysokaya, the Central Sikhote-Alin, is described. This vegetation consists mainly of subalpine spruce-fir forest, a complex of subalpine meadows, shrubs, groves of Betula lanata (B. ermanii s.l.), krummholz of Pinus pumila and alpine tundras. Significant disturbances in the vegetation structure were noted, especially in the forest-tundra ecotone accompanying a sharp reduction of the belts of Betula lanata and Pinus pumila. The altitudinal level of the upper timberline reaches 1600 m a.s.l. which is 250 m less than the expected altitude calculated by Kira's warmth index. An undergrowth of scattered trees of Picea and Betula are growing up to the mountain top. Based on these data and a review of the literature, we concluded that a catastrophic lowering of the timberline and devastation of the subalpine vegetation belt occurred several centuries ago, probably as result of fires.     

Fisionomía y sociología de los bosques de Nothofagus dombeyi en la región de Nahuel Huapi

Summary In the mountains around Lake Nahuel Huapi three belts of vegetation can be observed: the evergreen forests of Nothofagus dombeyi between surface level of the lake (ca. 770 m a.s.l.) and 1100–1200 m; the deciduous forests of Nothofagus pumilio; and the Andean-antarctic meadows and other communities above the timberline (±1600 m).A physiognomical study of the evergreen beech forests shows three main types of structure, one of which coincides with a quite different floristical composition.Detailed phytosociological work following the method of Braun-Blanquet is proving the floristical relationship between the deciduous forests of Nothofagus pumilio or N. antarctica and the main part of the evergreen patagonical forests of Nothofagus dombeyi, especially when austrocedrus chilensis is present. Besides other units, there has therefore been established a new alliance, Austrocedro-Nothofagion, belonging to the Nothofagetalia pumilionis-dombeyi as an order of the Nothofagetea pumilionis-antarcticae Oberd. 1960.Only a few stands in the extreme West of Argentine territory present the characteristics of the Nothofago-Winterion Oberd., which is an alliance of the Wintero-Nothofagetea Oberd., and corresponds to the forêt valdivienne of phytogeographical literature.Comment has been made on the theoretical bases of systematics, considering that in certain cases the forest communities studied demonstrate what some ecologists think to be a continuum of vegetation.     

Using Soil 13C to Detect the Historic Presence of Schizachyrium scoparium (Little Bluestem) Grasslands on Martha's Vineyard

Abstract We used differences in soil carbon δ¹³C values between forested sites and grasslands dominated by the C₄ grass Schizachyrium scoparium (little bluestem) to detect the presence of former grasslands in the historical landscape of the coastal sand plain of Martha's Vineyard, Massachusetts, U.S.A. Soil δ¹³C was measured at (1) sites with long‐term forest or grassland vegetation and (2) sites with known histories where forest vegetation invaded grassland and where forest converted to grassland. The δ¹³C of soil under long‐term grassland was –24.1‰ at 0 to 2 cm depth and –23.4‰ at 2 to 10 cm and was enriched by 3.4‰ and 2.8‰ compared with soil under long‐term forest. In forests that invaded grasslands dominated by S. scoparium, soil δ¹³C decreased as C derived from trees replaced C from S. scoparium. This decline occurred faster in surface soils and in the light soil organic matter fraction than in the mineral soil. In forests that converted to grasslands, soil δ¹³C increased and the rate of increase was similar in surface and mineral soil and in the different soil organic matter fractions. Rates of change indicated that soil δ¹³C could be used to detect changes in vegetation involving the presence or absence of S. scoparium during the last 150 years. Application of this model to a potential grassland restoration site on Martha's Vineyard where the landscape history was not known indicated that the site was previously unoccupied by S. scoparium during this time. The δ¹³C of surface mineral soil can be useful for detecting the presence of historic S. scoparium grasslands but only in the period well after European settlement of these coastal sand plain landscapes.     

Large‐scale fungal diversity assessment in the Andean Yungas forests reveals strong community turnover among forest types along an altitudinal gradient

The Yungas, a system of tropical and subtropical montane forests on the eastern slopes of the Andes, are extremely diverse and severely threatened by anthropogenic pressure and climate change. Previous mycological works focused on macrofungi (e.g. agarics, polypores) and mycorrhizae in Alnus acuminata forests, while fungal diversity in other parts of the Yungas has remained mostly unexplored. We carried out Ion Torrent sequencing of ITS2 rDNA from soil samples taken at 24 sites along the entire latitudinal extent of the Yungas in Argentina. The sampled sites represent the three altitudinal forest types: the piedmont (400–700 m a.s.l.), montane (700–1500 m a.s.l.) and montane cloud (1500–3000 m a.s.l.) forests. The deep sequence data presented here (i.e. 4 108 126 quality‐filtered sequences) indicate that fungal community composition correlates most strongly with elevation, with many fungi showing preference for a certain altitudinal forest type. For example, ectomycorrhizal and root endophytic fungi were most diverse in the montane cloud forests, particularly at sites dominated by Alnus acuminata, while the diversity values of various saprobic groups were highest at lower elevations. Despite the strong altitudinal community turnover, fungal diversity was comparable across the different zonal forest types. Besides elevation, soil pH, N, P, and organic matter contents correlated with fungal community structure as well, although most of these variables were co‐correlated with elevation. Our data provide an unprecedented insight into the high diversity and spatial distribution of fungi in the Yungas forests.     

Nitrogen limitation and microbial diversity at the treeline

Tree growth limitation at treeline has mainly been studied in terms of carbon limitation while effects and mechanisms of potential nitrogen (N) limitation are barely known, especially in the southern hemisphere. We investigated how soil abiotic properties and microbial community structure and composition change from lower to upper sites within three vegetation belts (Nothofagus betuloides and N. pumilio forests, and alpine vegetation) across an elevation gradient (from 0 to 650 m a.s.l.) in Cordillera Darwin, southern Patagonia. Increasing elevation was associated with a decrease in soil N‐NH₄⁺ availability within the N. pumilio and the alpine vegetation belt. Within the alpine vegetation belt, a concurrent increase in the soil C:N ratio was associated with a shift from bacterial‐dominated in lower alpine sites to fungal‐dominated microbial communities in upper alpine sites. Lower forested belts (N. betuloides, N. pumilio) exhibited more complex patterns both in terms of soil properties and microbial communities. Overall, our results concur with recent findings from high‐latitude and altitude ecosystems showing decreased nutrient availability with elevation, leading to fungal‐dominated microbial communities. We suggest that growth limitation at treeline may result, in addition to proximal climatic parameters, from a competition between trees and soil microbial communities for limited soil inorganic N. At higher elevation, soil microbial communities could have comparably greater capacities to uptake soil N than trees, and the shift towards a fungal‐dominated community would favour N immobilization over N mineralization. Though evidences of altered nutrient dynamics in tree and alpine plant tissue with increasing altitude remain needed, we contend that the measured residual low amount of inorganic N available for trees in the soil could participate to the establishment limitation. Finally, our results suggest that responses of soil microbial communities to elevation could be influenced by functional properties of forest communities for instance through variations in litter quality.     

A model‐data comparison of Holocene timberline changes in the Swiss Alps reveals past and future drivers of mountain forest dynamics

Mountain vegetation is strongly affected by temperature and is expected to shift upwards with climate change. Dynamic vegetation models are often used to assess the impact of climate on vegetation and model output can be compared with paleobotanical data as a reality check. Recent paleoecological studies have revealed regional variation in the upward shift of timberlines in the Northern and Central European Alps in response to rapid warming at the Younger Dryas/Preboreal transition ca. 11 700 years ago, probably caused by a climatic gradient across the Alps. This contrasts with previous studies that successfully simulated the early Holocene afforestation in the (warmer) Central Alps with a chironomid‐inferred temperature reconstruction from the (colder) Northern Alps. We use LandClim , a dynamic landscape vegetation model to simulate mountain forests under different temperature, soil and precipitation scenarios around Iffigsee (2065 m a.s.l.) a lake in the Northwestern Swiss Alps, and compare the model output with the paleobotanical records. The model clearly overestimates the upward shift of timberline in a climate scenario that applies chironomid‐inferred July‐temperature anomalies to all months. However, forest establishment at 9800 cal. BP at Iffigsee is successfully simulated with lower moisture availability and monthly temperatures corrected for stronger seasonality during the early Holocene. The model‐data comparison reveals a contraction in the realized niche of Abies alba due to the prominent role of anthropogenic disturbance after ca. 5000 cal. BP, which has important implications for species distribution models (SDMs) that rely on equilibrium with climate and niche stability. Under future climate projections, LandClim indicates a rapid upward shift of mountain vegetation belts by ca. 500 m and treeline positions of ca. 2500 m a.s.l. by the end of this century. Resulting biodiversity losses in the alpine vegetation belt might be mitigated with low‐impact pastoralism to preserve species‐rich alpine meadows.     

The influence of former land-use on vegetation and biodiversity in the boreo-nemoral zone of Sweden

Pollen analyses were carried out at two sites with contrasting land-use histories (in-field and out-land) within a single estate. The aim was to distinguish the relative importance of natural processes and cultural influence on the development of vegetation and biodiversity. The estate lies in the boreo-nemoral zone of southern Sweden, and attention is focused on the distribution of coniferous and deciduous trees. The in-fields. which lie close to the estate buildings, are currently dominated by deciduous trees, and have a documented history as fields and hay meadows. The more distant out-lands were primarily used as grazing land in the past, and support coniferous forest at present. The study covers the last 4000 yr, 2000–1000 BC: the out-lands site supported natural, dense forests consisting of Quercus, Betula, Tilia, Alnus and Corylus. 1000 BC–AD 1100: several events are best interpreted as an increased cultural activity in the area. Agriculture was based on animal husbandry and the recorded cereals probably originate from a kind of shifting cultivation. AD 1000–1800: agriculture intensified on the in-fields with cereal cultivation of increased importance, while the out-fields were used for slash-and-burn agriculture and forest grazing. The forests became more open in structure but the composition remained unchanged. An increase in Colluna was a possible consequence of over-exploitation, AD 1800 onwards: the out-field deciduous forests were rapidly replaced by Picea-Pinus coniferous forests during the l800's. The in-fields retained deciduous forest with a continuity of Quercus and other species. There is a close, positive relationship between floristic diversity and cultural influence during the last 4000 yr. A comparison is made with a similar investigation on another estate in the region, revealing small differences between the estates, but striking similarities in the effects of land-use types on the development of vegetation. The significance of former in-fields for nature conservation is discussed, particularly as a potential source for increasing the deciduous component in commercial forestry practice.