Plant community responses to experimental warming across the tundra biome

Recent observations of changes in some tundra ecosystems appear to be responses to a warming climate. Several experimental studies have shown that tundra plants and ecosystems can respond strongly to environmental change, including warming; however, most studies were limited to a single location and were of short duration and based on a variety of experimental designs. In addition, comparisons among studies are difficult because a variety of techniques have been used to achieve experimental warming and different measurements have been used to assess responses. We used metaanalysis on plant community measurements from standardized warming experiments at 11 locations across the tundra biome involved in the International Tundra Experiment. The passive warming treatment increased plant-level air temperature by 1-3 degrees C, which is in the range of predicted and observed warming for tundra regions. Responses were rapid and detected in whole plant communities after only two growing seasons. Overall, warming increased height and cover of deciduous shrubs and graminoids, decreased cover of mosses and lichens, and decreased species diversity and evenness. These results predict that warming will cause a decline in biodiversity across a wide variety of tundra, at least in the short term. They also provide rigorous experimental evidence that recently observed increases in shrub cover in many tundra regions are in response to climate warming. These changes have important implications for processes and interactions within tundra ecosystems and between tundra and the atmosphere.

Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time

Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation - and associated ecosystem consequences - have the potential to be much greater than we have observed to date.

BioTIME: A database of biodiversity time series for the Anthropocene

MOTIVATION

The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene.

MAIN TYPES OF VARIABLES INCLUDED

The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record.

SPATIAL LOCATION AND GRAIN

BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km2 (158 cm2) to 100 km2 (1,000,000,000,000 cm2).

TIME PERIOD AND GRAIN

BioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year.

MAJOR TAXA AND LEVEL OF MEASUREMENT

BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates.

SOFTWARE FORMAT

.csv and .SQL.

Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes

Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide. Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.

Pan European Phenological database (PEP725): a single point of access for European data

The Pan European Phenology (PEP) project is a European infrastructure to promote and facilitate phenological research, education, and environmental monitoring. The main objective is to maintain and develop a Pan European Phenological database (PEP725) with an open, unrestricted data access for science and education. PEP725 is the successor of the database developed through the COST action 725 "Establishing a European phenological data platform for climatological applications" working as a single access point for European-wide plant phenological data. So far, 32 European meteorological services and project partners from across Europe have joined and supplied data collected by volunteers from 1868 to the present for the PEP725 database. Most of the partners actively provide data on a regular basis. The database presently holds almost 12 million records, about 46 growing stages and 265 plant species (including cultivars), and can be accessed via http://www.pep725.eu/ . Users of the PEP725 database have studied a diversity of topics ranging from climate change impact, plant physiological question, phenological modeling, and remote sensing of vegetation to ecosystem productivity.

Event-related potentials in newborns with and without familial risk for dyslexia: principal component analysis reveals differences between the groups

Differences revealed by factor scores extracted by principal component analysis (PCA) from event-related potential (ERP) data of newborns with and without familial risk for dyslexia were examined and compared to results obtained by using original averaged ERPs. ERPs to consonant-vowel syllables (synthetic /ba/, /da/, /ga/; and natural /paa/, /taa/, /kaa/) were recorded from 26 at-risk and 23 control 1-7 day-old infants. The stimuli were presented equiprobably and with interstimulus intervals varying at random from 3,910 to 7,285 ms. Statistically significant between-group differences were found to be relatively similar irrespective of the methods of analysis (original ERPs vs. factor scores from PCA). Responses to /ga/ differed from those to /ba/ and /da/ between the groups in the right hemisphere at the latencies of 50-170 ms (Factor 4) and 540-630 ms (Factor 3). The groups differed also in their responses to /da/ in the posterior electrode sites at 740-940 ms (Factor 2). There were no group differences in the natural stimulus set. These results demonstrate that brain activation differences may be implicated in risk for dyslexia immediately after birth. The results also show that the PCA-ANOVA procedure is an effective way of identifying the group-related variance in the ERP-data when the component structure, such as those of infants, is not well-known in advance.

Speech perception and brain laterality: the effect of ear advantage on auditory event-related potentials

Dichotic listening has been used for assessing asymmetries in processing auditory stimuli. It is known that there is better recognition of dichotic stimuli in the right ear with verbal stimuli (right ear advantage, REA) by the majority of the subjects. We were interested in the psychophysiological correlates of ear advantage as it is manifested in event-related potentials (ERP). We compared ERPs to monaural and dichotic syllables in stable REA and LEA subjects. The most consistent finding was that REA subjects show larger positive ERP deflections over the left hemisphere (maximal at T5) and LEA subjects over the right hemisphere (maximal at T6) both at the latency range of 320-340 msec. Thus, brain event-related potentials support the contention that the REA and LEA reflect differential activation of the left and right hemispheres, respectively.

Effects of reproduction and artificial herbivory on vegetative growth and resource levels in deciduous and evergreen dwarf shrubs

Effects of reproduction (production of flowers and berries) and artificial herbivory of different phenological stages on deciduous bilberry (Vaccinium myrtillus L.) and evergreen lingonberry (Vaccinium vitis-idaea L.) were investigated to determine differences in allocation patterns and recovery ability between these species. Vegetative growth and concentration of sugars, starch, and nitrogen were measured in ramets at the end of the growing season. Statistical comparisons were made between the treatments and damage times, but not between the species, as these were manipulated at different sites within the same forest. Reproduction reduced the vegetative growth significantly in lingonberry, whereas the fertile bilberry ramets grew even more than the sterile ones. The bilberry produced new shoots as a response to simulated herbivory, which significantly decreased carbohydrate levels in tissues. The evergreen lingonberry produced less shoots, and carbohydrate levels increased significantly. Nitrogen concentration either remained unchanged or increased in both species. For both species, time of damage affected the carbon and nitrogen levels as well as the ability to regrow. The species have developed different strategies to overcome the costs of sexual reproduction and herbivory damage, apparently as a result of the different resource allocation patterns and different architectural constraints for shoot development. The evergreen lingonberry grows slowly and conserves resources, whereas the deciduous bilberry allocates resources to increase the photosynthesizing biomass, which increases the potential of future survival, growth, and reproduction. Key words: carbohydrate, clipping, deblossoming, defoliation, nitrogen, Vaccinium.

Differences in recovery between a deciduous and an evergreen ericaceous clonal dwarf shrub after simulated aboveground herbivory and belowground damage

Insect and microtine rodent herbivory (defoliation and branch clipping, respectively) were simulated in stands of the deciduous Vaccinium myrtillus L. and evergreen V. vitis-idaea L. Rhizome connections around the treated plots were either left intact or severed. Recovery in the plots was monitored for two growth seasons, from 1991 to 1992. It was hypothesized that the evergreen V. vitis-idaea would suffer more from the simulated herbivory treatment than V. myrtillus, but that severing the rhizome connections would decrease recovery of both species, because clonal integration is disrupted and wounding may have a harmful influence on growth. After two growth seasons, recovery was complete from simulated herbivory in V. myrtillus, whereas the new dry biomass was reduced slightly (22 – 37%) or significantly (49%) compared with that of the control in V. vitis-idaea. Rhizome severing reduced the growth of the branches and ramets and the aboveground dry biomass by 34% compared with that of the unsevered control in V. myrtillus. In the evergreen V. vitis-idaea, severing slightly reduced growth, the effect being significant only in the clipped treatment. The results suggest that the deciduous V. myrtillus recovers more rapidly from simulated herbivory than the evergreen V. vitis-idaea. Rhizome severing is more detrimental to the growth of V. myrtillus, but less detrimental to recovery from simulated herbivory. Sexual reproduction decreases more in V. vitis-idaea than in V. myrtillus after damage. Key words: compensation, growth form, herbivory, rhizome severing, Vaccinium

Impacts of drainage, restoration and warming on boreal wetland greenhouse gas fluxes

Northern wetlands with organic soil i.e., mires are significant carbon storages. This key ecosystem service may be threatened by anthropogenic activities and climate change, yet we still lack a consensus on how these major changes affects their carbon sink capacities. We studied how forestry drainage and restoration combined with experimental warming, impacts greenhouse gas fluxes of wetlands with peat. We measured CO₂ and CH₄ during two and N₂O fluxes during one growing season using the chamber method. Gas fluxes were primarily controlled by water table, leaf area and temperature. Land use had a clear impact of on CO₂ exchange. Forestry drainage increased respiration rates and decreased field layer net ecosystem CO₂ uptake (NEE) and leaf area index (LAI), while at restoration sites the flux rates and LAI had recovered to the level of undrained sites. CH₄ emissions were exceptionally low at all sites during our study years due to natural drought, but still somewhat lower at drained compared to undrained sites. Moderate warming triggered an increase in LAI across all land use types. This was accompanied by an increase in cumulative seasonal NEE. Restoration appeared to be an effective tool to return the ecosystem functions of these wetlands as we found no differences in LAI or any gas flux components (PMAX, Reco, NEE, CH₄ or N₂O) between restored and undrained sites. We did not find any signs that moderate warming would compromise the return of the ecosystem functions related to C sequestration.

Aboveground growth habits of two Vaccinium species in relation to habitat

Ramet morphology in the deciduous Vaccinium myrtillus L. and the evergreen Vaccinium vitis-idaea L. was compared between the forest and open, clear-felled habitats. Growth habits were measured in terms of branching, shoot mass, bud type, branching angle, and vertical elevation of ramets. New ramets of both species were produced from buds on the below-ground stem. Branching occurred from buds on 1-year-old shoots in young ramets. Aging and flowering induced rejuvenation, i.e., production of new shoots from buds on older shoot generations within the ramets. Sympodial V. myrtillus ramets were more branched than the predominantly monopodial V. vitis-idaea ramets. In ramets of both species, vegetative shoots grew primarily from distal buds in the forest, whereas a greater number of lower buds were activated in the ramets in the open habitat. Vaccinium myrtillus ramets grew more horizontally and had wider branching angles to increase the intercepted radiation in the forest, whereas compact, vertically growing ramets prevailed in the open habitat, where light was not limited. No difference in branch orientation was observed between habitats in V. vitis-idaea. Production of flowers was greater in the open habitat than in the forest in both species. The observed differences in growth habits between forest and open habitat were assumed to indicate high morphological plasticity in both species, allowing the plants to respond rapidly to changed environmental conditions. Key words: architecture, branching, growth habit, shrub, Vaccinium.

Repeated assessment of the Tower of Hanoi test: reliability and age effects

The purpose of this research was to analyze the effects of repeating an executive function test. Three versions of the Tower of Hanoi (TOH) test were repeated three times each, with test-retest intervals of 2 months. Two groups of children participated in the research (7.7 and 11.6 years, n = 22 and n = 28). Repeating the assessment improved the performance and decreased the total performance time in both of the groups. The older participants improved their performance faster than the younger ones. The reliability of all the scores, besides the error scores, seemed to be satisfactory after the first few assessments. The stability of the scores was maintained through all the assessments. The planning time did not explain the variations of the achieved score. The reasons for the initially low reliabilities are discussed, and modifications for the test administration and scoring are suggested.

Tourism, biodiversity and protected areas--Review from northern Fennoscandia

Tourist numbers in northern Fennoscandia outweigh those in other northern boreal - arctic regions, which creates a specific need to evaluate the impacts of tourism. This review 1) identifies patterns and trends in the vegetation and wildlife of northern Fennoscandian terrestrial ecosystems as a consequence of tourism and recreation, 2) discusses the implications of findings in terms of the intensity, area and magnitude of impacts, changing climate and management needs under increasing tourist pressure, and 3) identifies research gaps. The reviewed studies show negative environmental and biodiversity impacts that are most pronounced near tourist resorts. The most sensitive plants, birds and mammals decline or disappear from the disturbed sites, and the species composition shifts from 'wild' species to cultural and human associated species. There is little research on the spread of alien species, but the few examples show that alien species can be promoted by tourism activities. Impacts of the use of motorized vehicles have not been widely studied either, despite the extensive track network which can cause disturbance to wildlife. The integrated impacts of tourism and climate change on the vegetation and wildlife was not addressed directly in any of the reviewed studies. In addition, little research has been done on carrying out restoration at tourist areas. Scientific research on these topics is needed to prevent, minimize or restore the most negative ecological impacts of tourism and recreation.

Vegetation shift from deciduous to evergreen dwarf shrubs in response to selective herbivory offsets carbon losses: evidence from 19 years of warming and simulated herbivory in the subarctic tundra

Selective herbivory of palatable plant species provides a competitive advantage for unpalatable plant species, which often have slow growth rates and produce slowly decomposable litter. We hypothesized that through a shift in the vegetation community from palatable, deciduous dwarf shrubs to unpalatable, evergreen dwarf shrubs, selective herbivory may counteract the increased shrub abundance that is otherwise found in tundra ecosystems, in turn interacting with the responses of ecosystem carbon (C) stocks and CO2 balance to climatic warming. We tested this hypothesis in a 19-year field experiment with factorial treatments of warming and simulated herbivory on the dominant deciduous dwarf shrub Vaccinium myrtillus. Warming was associated with a significantly increased vegetation abundance, with the strongest effect on deciduous dwarf shrubs, resulting in greater rates of both gross ecosystem production (GEP) and ecosystem respiration (ER) as well as increased C stocks. Simulated herbivory increased the abundance of evergreen dwarf shrubs, most importantly Empetrum nigrum ssp. hermaphroditum, which led to a recent shift in the dominant vegetation from deciduous to evergreen dwarf shrubs. Simulated herbivory caused no effect on GEP and ER or the total ecosystem C stocks, indicating that the vegetation shift counteracted the herbivore-induced C loss from the system. A larger proportion of the total ecosystem C stock was found aboveground, rather than belowground, in plots treated with simulated herbivory. We conclude that by providing a competitive advantage to unpalatable plant species with slow growth rates and long life spans, selective herbivory may promote aboveground C stocks in a warming tundra ecosystem and, through this mechanism, counteract C losses that result from plant biomass consumption.

Trends in phenology of Betula pubescens across the boreal zone in Finland

Timing of plant phenophases is a useful biological indicator which shows how nature responds to the variation in climate. Thus, long phenological observation series help to estimate the impact of changing climate on forest plants. We investigated whether phenological patterns of downy birch Betula pubescens respond to warming climate and whether the intensity of the responses varies among phytogeographical zones. We studied data collected by the Finnish National Phenological Network from 30 observation sites across Finland during 1997-2006. The advancement in the timing of the earliest phenophase, bud burst, ranged from 0.7 days/year in southern boreal zone to 1.4 days/year in middle and northern boreal zones. Timing of bud burst was most clearly dependent on mean May temperatures. The intensity of the response to temperature increased from south to north. The advancement of bud burst resulted into a significant lengthening of the growth period by 1.2-1.6 days per year in northern and middle boreal zones, respectively, whereas the lengthening was not significant in the southern boreal zone. No trend was observed in the timing of autumn phenophases.

Vegetation structure and photosynthesis respond rapidly to restoration in young coastal fens

Young coastal fens are rare ecosystems in the first stages of peatland succession. Their drainage compromises their successional development toward future carbon (C) reservoirs. We present the first study on the success of hydrological restoration of young fens. We carried out vegetation surveys at six young fens that represent undrained, drained, and restored management categories in the Finnish land uplift coast before and after restoration. We measured plant level carbon dioxide (CO2) assimilation and chlorophyll fluorescence (Fv/Fm) from 17 most common plant species present at the sites. Within 5 years of restoration, the vegetation composition of restored sites had started to move toward the undrained baseline. The cover of sedges increased the most in response to restoration, while the cover of deciduous shrubs decreased the most. The rapid response indicates high resilience and low resistance of young fen ecosystems toward changes in hydrology. Forbs had higher photosynthetic and respiration rates than sedges, deciduous shrubs, and grasses, whereas rates were lowest for evergreen shrubs and mosses. The impact of management category on CO2 assimilation was an indirect consequence that occurred through changes in plant species composition: Increase in sedge cover following restoration also increased the potential photosynthetic capacity of the ecosystem. Synthesis and applications. Restoration of forestry drained young fens is a promising method for safeguarding them and bringing back their function as C reservoirs. However, their low resistance to water table draw down introduces a risk that regeneration may be partially hindered by the heavy drainage in the surrounding landscape. Therefore, restoration success is best safeguarded by managing the whole catchments instead of carrying out small-scale projects.

Urban forest soils harbour distinct and more diverse communities of bacteria and fungi compared to less disturbed forest soils

Anthropogenic changes to land use drive concomitant changes in biodiversity, including that of the soil microbiota. However, it is not clear how increasing intensity of human disturbance is reflected in the soil microbial communities. To address this issue, we used amplicon sequencing to quantify the microbiota (bacteria and fungi) in the soil of forests (n = 312) experiencing four different land uses, national parks (set aside for nature conservation), managed (for forestry purposes), suburban (on the border of an urban area) and urban (fully within a town or city), which broadly represent a gradient of anthropogenic disturbance. Alpha diversity of bacteria and fungi increased with increasing levels of anthropogenic disturbance, and was thus highest in urban forest soils and lowest in the national parks. The forest soil microbial communities were structured according to the level of anthropogenic disturbance, with a clear urban signature evident in both bacteria and fungi. Despite notable differences in community composition, there was little change in the predicted functional traits of urban bacteria. By contrast, urban soils exhibited a marked loss of ectomycorrhizal fungi. Soil pH was positively correlated with the level of disturbance, and thus was the strongest predictor of variation in alpha and beta diversity of forest soil communities, indicating a role of soil alkalinity in structuring urban soil microbial communities. Hence, our study shows how the properties of urban forest soils promote an increase in microbial diversity and a change in forest soil microbiota composition.

The associations of indoor environment and psychosocial factors on the subjective evaluation of Indoor Air Quality among lower secondary school students: a multilevel analysis

Subjective evaluation of Indoor Air Quality (subjective IAQ) reflects both building-related and psychosocial factors, but their associations have rarely been studied other than on the individual level in occupational settings and their interactions have not been assessed. Therefore, we studied whether schools' observed indoor air problems and psychosocial factors are associated with subjective IAQ and their potential interactions. The analysis was performed with a nationwide sample (N = 195 schools/26946 students) using multilevel modeling. Two datasets were merged: (i) survey data from students, including information on schools' psychosocial environment and subjective IAQ, and (ii) data from school principals, including information on observed indoor air problems. On the student level, school-related stress, poor teacher-student relationship, and whether the student did not easily receive help from school personnel, were significantly associated with poor subjective IAQ. On the school level, observed indoor air problem (standardized β = -0.43) and poor teacher-student relationship (standardized β = -0.22) were significant predictors of poor subjective IAQ. In addition, school-related stress was associated with poor subjective IAQ, but only in schools without observed indoor air problem (standardized β = -0.44).