Responses of alpine shrubs to simulated environmental change during three years in the mid-latitude mountain, northern Japan

Effects of artificial warming on phenology, individual leaf traits, vegetative growth, and reproduction of five alpine species (two deciduous and three evergreen shrubs) were investigated during three years in the mid-latitude alpine, northern Japan. Eleven open-top chambers (OTCs) were set up on a fellfield (1680 m a. s. l.) in the Taisetsu Mountains by which air temperature at plant height was increased by ca 2°C. Vaccinium uliginosum (deciduous shrub) showed earlier leaf emergence in every season and earlier flowering only in the first season in the OTCs. By contrast, acceleration of leaf emergence in the OTCs was not clear for other species, i.e. Arctous alpinus (deciduous shrub). Ledum palustre. V. vitis-idaea , and Empetrum nigrum (evergreen shrub). Both deciduous species showed longer leaf life-span in the OTCs every season. All evergreen species had higher leaf survival rates in the OTCs. indicating extension of leaf life-span. Leaf nitrogen concentration and leaf mass per unit leaf area (mg cm ⁻²) generally tended to decrease in the OTCs. Relationships between the individual leaf traits and cumulative air temperature during the leaf developing period were not clear. Total leaf production during the three seasons increased in the OTCs in A. alpinus. L. palustre. V. vitis-idaea , and E. nigrum. All evergreen shrubs showed larger shoot growth in the OTCs but both deciduous shrubs did not show significant changes. In contrast to the vegetative growth, deciduous shrubs produced more flowers in the OTCs. Fruit production was not influenced by the OTCs for all species. The extension of photosynthetic period in the OTCs may contribute to the larger vegetative growth or flower production.     

苔藓植物对环境变化的响应及适应性研究进展

苔藓植物由于其结构相对简单,对环境变化的反应较为敏感,是一类良好的生物指示植物.本文综述了水分、光照、温度等方面的环境因子变化对苔藓植物的影响以及苔藓植物对环境污染的响应及适应的最近研究进展,以期促进国内深入开展苔藓植物对环境污染和全球变化的响应、适应及其生态指示作用等研究.     

苔藓植物对环境变化的影响及适应性研究进展

苔藓植物由于其结构相对简单,对环境变化的反应较为敏感,是一类良好的生物指示植物,本文综述了水分、光照、温度等方面的环境因子变化对苔藓植物的影响以及苔藓植物对环境污染的响应及适应的最近研究进展,以期促进国内深入开展苔藓植物对环境污染和全球变化的响应、适应及其生态指示作用等研究。     

Preferences of dead wood inhabiting bryophytes for decay stage,log size and habitat types in Hungarian beech forests

Abstract

This study describes the quantitative preferences of epixylic bryophytes for decay stages, log size and habitat type. The two habitats investigated were zonal (situated on plateaux without extreme microclimatic conditions) and ravine-like near-natural beech stands. Preferences of 30 bryophyte species are described using logistic regression modelling. The species pool differed between habitat types. In the ravine-like forests more species are found. Regionally rare epixylic species (mainly liverworts) were limited to these forests. The species richness of individual logs was also higher in the ravine-like than in the zonal forests and the proportion of logs of all sizes colonized by bryophytes was higher in the former. The species were classified into four categories on the basis of their preference for decay stages: strict epixylics, indifferent species, preferential epixylics and epiphytes. The epixylics and preferential epixylics prefer advanced decay stages while the latter extend further into earlier decay stages than strict epixylics. Common epixylic species have a wider tolerance to decay stage than rare ones. Probabilities of species occurrence increase with log size, more strongly in zonal stands than in ravines. A simple successional scheme for bryophyte succession on dead wood is proposed on the basis of the observed species responses.     

Response of bryophytes to exposure and water availability on some European travertines

Abstract

Seventeen travertine-bryophyte taxa were recorded in 212 quadrats from 17 sites, and the cover of the eight commonest species was analysed in terms of aspect, slope, exposure and water relations. Only Aneura pinguis was significantly affected by aspect, while Eucladium verticillatum and Hymenostylium recurvirostrum preferred steep slopes. The last two species, with Didymodon tophaceus, were also found to prefer sheltered sites, while Bryum pseudotriquetrum, Palustriella commutata var. commutata and Pellia endiviifolia were more common in exposed situations. Didymodon tophaceus, Hymenostylium recurvirostrum and Aneura pinguis were mostly confined to seepages and were kept moist by capillarity, while Palustriella commutata var. falcata and Pellia endiviifolia withstood high flows. Cratoneuron filicinum, Palustriella commutata var. commutata and Pellia endiviifolia had wide ecological amplitudes and were among the most frequently recorded species.     

A contribution to the knowledge of epiphyllous bryophytes of Bioko Island (Equatorial Guinea), including additional remarks on non-epiphyllous species

Abstract

A collection of epiphyllous bryophytes from Bioko Island was investigated. It contained 57 epiphyllous bryophytes, comprising 55 hepatics and two mosses. Three taxa, Cololejeunea eustacei Pócs, Colura calderae Pócs and Lejeunea halei Robinson subsp. africana Pócs, are new to science. Cololejeunea papilliloba Steph. is new to Africa, five species of hepatics are new to West Africa, and an additional 31 species of hepatics are newly reported from Bioko Island. The second part of the paper deals with records of non-epiphyllous collections. Fourteen species are reported for the first time for Bioko Island. Actinodontium dusenii Broth. is made a synonym of Actinodontium streptopogoneum Broth. The following new combination is proposed: Wijkia rigidicaule (Müll.Hal. ex Broth.) Frank Müll., comb. nov. (Basionym: Acanthocladium rigidicaule Müll.Hal. ex Broth.).     

秦岭北麓油松径向生长对气候变化的响应

以秦岭北麓南五台油松为样本,建立油松树轮宽度标准化年表(STD),研究油松径向生长与气候因子之间的相关性。结果表明: 秦岭北麓油松径向生长与前一年9月及当年5月水分因子呈显著正相关,与前一年11月温度因子呈显著正相关,与前一年10月、当年5月温度因子呈显著负相关。油松径向生长对不同气候因子响应均存在明显的滞后效应。油松径向生长与PDSI干旱指数具有较好的相关性,特别是与前一年9—12月、当年5月PDSI呈显著正相关。回归模型能较好地模拟树轮宽度指数与PDSI之间的关系,油松极宽窄轮的形成主要是干旱作用的结果。综合各种气候指标,PDSI能更好地反映研究区油松径向生长的特征。     

Testing reliability of short-term responses to predict longer-term responses of bryophytes and lichens to environmental change

Environmental changes are predicted to have severe and rapid impacts on polar and alpine regions. At high latitudes/altitudes, cryptogams such as bryophytes and lichens are of great importance in terms of biomass, carbon/nutrient cycling, cover and ecosystem functioning. This seven-year factorial experiment examined the effects of fertilizing and experimental warming on bryophyte and lichen abundance in an alpine meadow and a heath community in subarctic Sweden. The aim was to determine whether short-term responses (five years) are good predictors of longer-term responses (seven years). Fertilizing and warming had significant negative effects on total and relative abundance of bryophytes and lichens, with the largest and most rapid decline caused by fertilizing and combined fertilizing and warming. Bryophytes decreased most in the alpine meadow community, which was bryophyte-dominated, and lichens decreased most in the heath community, which was lichen-dominated. This was surprising, as the most diverse group in each community was expected to be most resistant to perturbation. Warming alone had a delayed negative impact. Of the 16 species included in statistical analyses, seven were significantly negatively affected. Overall, the impacts of simulated warming on bryophytes and lichens as a whole and on individual species differed in time and magnitude between treatments and plant communities (meadow and heath). This will likely cause changes in the dominance structures over time. These results underscore the importance of longer-term studies to improve the quality of data used in climate change models, as models based on short-term data are poor predictors of long-term responses of bryophytes and lichens.     

Responses of the clonal sedge, Carex bigelowii, to two seasons of simulated climate change

The effect of enhanced temperature was studied in open-top chambers on the arctic clonal sedge Carex bigelowii Torr. ex Schwein. at Latnjajaure Field Station, Swedish Lapland for two growing seasons. The flowering phenology of C. bigelowii accelerated during the first field season that the open-top chambers were erected. After the second season of perturbation the sexual reproductive investment was higher in the open-top chambers than in the controls and flowering phenology was still accelerated. Leaf phenology and the growth of vegetative tillers followed the same pattern in the open-top chambers as in the controls, but the leaves were longer in the open-top chambers from the end of June until the end of August. The results suggest that relatively late flowering clonal graminoids may be favoured by warmer climate, at least in the short term.     

Effects of simulated long-term climatic change on the bryophytes of a limestone grassland community

The bryophyte vegetation of upland limestone grassland at Buxton in the southern Pennine Hills (UK) was studied following seven years' continuous simulated climate change treatments. The experimental design involved two temperature regimes (ambient, winter warming by 3°C) in factorial combination with three moisture regimes (normal, summer drought, supplemented summer rainfall) and with five replicate blocks. Percentage cover of the bryophytes was estimated visually using 15 randomly positioned quadrats (30 cm × 30 cm) within each of the 30 3 m × 3 m plots. Significant treatment effects were found but these were relatively modest. Total bryophyte cover and cover of Calliergonella cuspidata and Rhytidiadelphus squarrosus responded negatively to drought, whereas Fissidens dubius increased in the droughted plots. Campyliadelphus chrysophyllus increased with winter warming, while R. squarrosus, Lophocolea bidentata and species richness all decreased. The effects on the total bryophyte flora were further studied by canonical correspondence analysis, which yielded a first axis reflecting the combined effects of the moisture and temperature treatments. However, this analysis and a detrended correspondence analysis of the plot data also revealed that natural factors were more important causes of variation in the grassland community than the simulated climate treatments. It was concluded that dewfall may be an important source of moisture for grassland bryophytes and that this factor may have reduced the impact of the moisture treatments. The absence of some thermophilous species such as Homalothecium lutescens in the plots initially may also have reduced their scope for major vegetational change.     

Seasonal phosphatase activities of mosses from Upper Teesdale,northern England

Abstract

Changes in tissue nutrient concentrations and surface phosphatase activities of eight moss species were measured over one year in terrestrial and semi-aquatic environments on Widdybank Fell, Upper Teesdale National Nature Reserve, northern England. Rates of phosphatase activity in apical regions of moss shoots differed markedly between species, but were generally greatest in the winter and least in the summer in most species. Mean values for phosphomonoesterase activity (µmol para-nitrophenol g^-1 d.wt h^-1) ranged from 18.2 for Polytrichum commune to 85.8 for Palustriella commutata var. falcata. Mean phosphodiesterase activity ranged from 3.1 for Polytrichum commune to 86.2 for Hylocomium splendens. In contrast, tissue nitrogen and phosphorus concentrations remained relatively constant throughout the year. Phosphatase activities were negatively correlated with tissue phosphorus concentration for several species, although few relationships were detected between ambient nutrient concentrations and phosphatase activity, tissue nitrogen, or tissue phosphorus concentration. These results demonstrate that phosphatase activities can provide a sensitive indicator of nutrient stress in terrestrial and semi-aquatic mosses, notably in the ectohydric Hylocomium splendens. However, further studies at sites with a wide range of nutrient levels are required to determine whether the technique can be used to indicate ambient nutrient status.     

Effect of simulated environmental change on alpine soil arthropods

The effects of environmental change on soil animal communities are poorly known. Norwegian mountains are subject to both atmospheric nitrogen deposition and increased temperature. In a nutrient poor alpine Dryas heath in south Norway, soil arthropods were studied after 4 years of simulated environmental change by warming and/or nutrient addition. Warming alone only affected three low‐density Collembola species, while nutrient addition, with or without warming, greatly changed the dominance hierarchy of the microarthropod community. Certain Collembola species with a short (1 year) life cycle and predatory Gamasina mites increased markedly in density. These groups may have been favored by increased litter production, as plant biomass and litter producing graminoids and forbs increased significantly in plots with nutrient addition and nutrient addition combined with warming. Microarthropods with a longer life cycle, such as Oribatida and certain Collembola, were generally unaffected by nutrient addition and probably need more time to respond. The number of Oribatida taxa was, however, reduced in plots with nutrient addition, both with and without warming. A ground‐living species of Coccoidea (Homoptera) declined in plots with nutrient addition and warming compared with only warming, probably due to reduced cover of its host plant Dryas. The density of Diptera larvae (Sciaridae and Chironomidae) was unaffected by the treatments. Our results show that increased nutrient availability in nutrient poor alpine soils may have large but different effects on different taxa of soil animals. Species with short life cycles reacted first. Nutrient addition and nutrient addition combined with warming resulted in several effects below ground on microarthropods as previously shown above ground on plants: Increased biomass, high dominance of a few rapid‐growing species, contrasting responses of closely related species, and a reduction in species numbers. These short‐term responses may have profound long‐term effects in this alpine ecosystem.     

Short-term effects of simulated environmental change on phenology, leaf traits, and shoot growth of alpine plants on a temperate mountain, northern Japan

In order to assess the responses of circumpolar and semicircumpolar plants growing around their southern distribution margins to artificial warming, we set up 11 open-top chambers (OTCs) on a fell-field (1680 m a.s.l.) in the Taisetsu Mountains, northern Japan. The OTCs increased mean air temperature by 1.3°C through the growing season (June–September) and extended the length of the growing season. We examined phenology and leaf traits of plants in the OTCs and control plots during the first season under artificial warming treatment using two deciduous and three evergreen species. Ledum palustre (evergreen shrub), Vaccinium uliginosum , and Arctous alpinus (deciduous shrubs) showed earlier leaf emergence and/or flowering in the OTCs. Deciduous shrubs had longer individual leaf longevity and an extended foliage period in the OTCs than in the control plots. There were no significant differences in specific leaf area and leaf size for many species between the OTCs and the control plots. Vaccinium vitis-idaea (evergreen shrub), L. palustre, A. alpinus , and Empetrum nigrum (evergreen shrub) had lower leaf nitrogen concentration in the OTCs than in the control plots, whereas it was higher in V. uliginosum . Only E. nigrum showed larger annual shoot growth in the OTCs. No clear differences in response to the warming effect were detected between evergreen and deciduous species in the first season. Circumpolar plants growing in temperate alpine regions may be more affected by season length rather than temperature itself.     

树干/枝呼吸作用对环境变化的响应

树干/枝呼吸是调控森林碳平衡的关键生理过程之一,其对环境变化的响应在很大程度上决定了森林生产力及其固碳增汇能力.本文主要综述了近10年来林木树干/枝呼吸对大气CO2浓度升高、温度升高、干旱胁迫和人为管理的响应及其生理生态学调控机制,结果表明:大气CO2浓度升高和升温一般促进树干/枝的呼吸,其表观温度敏感性(Q10值)受树种、测定方法、温度范围、季节、林龄和径阶的影响,但变幅小于根系呼吸Q10值的变幅;干旱胁迫时,树干/枝呼吸速率减缓,随后进行浇水则会引发树干/枝呼吸的剧增,其生理学机制仍不清楚;不同的管理措施(如火烧、施肥、灌溉、修枝、环割等)对树干/枝呼吸的影响不尽相同.综述以往研究,提出今后值得深入探讨的4个方向:(1)明确树干/枝呼吸释放CO2的来源和去向以及建立相应的测定标准;(2)了解树干/枝呼吸对环境变化响应的生物学机制;(3)探讨树干/枝呼吸对环境变化的适应性;(4)树干液流、同位素示踪和CO2微电极技术的综合应用.     

Responses of riparian trees and shrubs to flow regulation along a boreal stream in northern Sweden

1. Flow dynamics is a major determinant of riparian plant communities. Therefore, flow regulation may heavily affect riparian ecosystems. Despite the large number of dams worldwide, little specific information is available on the longitudinal impacts of dams on vegetation, for example how far downstream and at what degree of regulation a dam on a river can influence riparian woodlands. 2. We quantified the long‐term responses of riparian trees and shrubs to flow regulation by identifying their lateral distribution and habitat conditions along a boreal river in northern Sweden that has been regulated by a single dam since 1948. The regulation has reduced annual flow fluctuations, this effect being largest at the dam, downstream from which it progressively decreases following the entrance of free‐flowing tributaries. 3. We related changes in the distribution patterns, composition, abundance and richness of tree and shrub species to the degree of regulation along the river downstream from the dam. Regulation has triggered establishment of trees and shrubs closer to the channel, making it possible to measure ecological impacts of flow regulation as differences in vegetation attributes relative to the positions of tree and shrub communities established before and after regulation. 4. Trees and shrubs had migrated towards the mid‐channel along the entire study reach, but the changes were largest immediately downstream of the dam. Shrubs were most impacted by flow regulation in terms of lateral movement, but the effect on trees extended furthest downstream. 5. The species composition of trees progressively returned to its pre‐regulation state with distance downstream, but entrance of free‐flowing tributaries and variation in channel morphology and substratum caused local deviations. Species richness after regulation increased for trees but decreased for shrubs. The changes in species composition and richness of trees and shrubs showed no clear downstream patterns, suggesting that other factors than the degree of regulation were more important in governing life form.     

苔藓植物对全球变化的响应及其生物指示意义

苔藓植物由于其结构相对简单,对大气成分浓度和全球气候等各方面的环境变化非常敏感,因此苔藓植物可以作为全球变化、环境污染、养分状况、森林整体性有生态系统健康等方面的生物指示材料,国内应深入开展苔藓植物对全球变化的响应与适应及其生物指示作用等研究。     

Sensitivity and response of northern hemisphere altitudinal and polar treelines to environmental change at landscape and local scales

The sensitivity and response of northern hemisphere altitudinal and polar treelines to environmental change are increasingly discussed in terms of climate change, often forgetting that climate is only one aspect of environmental variation. As treeline heterogeneity increases from global to regional and smaller scales, assessment of treeline sensitivity at the landscape and local scales requires a more complex approach than at the global scale. The time scale (short‐, medium‐, long‐term) also plays an important role when considering treeline sensitivity. The sensitivity of the treeline to a changing environment varies among different types of treeline. Treelines controlled mainly by orographic influences are not very susceptible to the effects of warming climates. Greatest sensitivity can be expected in anthropogenic treelines after the cessation of human activity. However, tree invasion into former forested areas above the anthropogenic forest limit is controlled by site conditions, and in particular, by microclimates and soils. Apart from changes in tree physiognomy, the spontaneous advance of young growth of forest‐forming tree species into present treeless areas within the treeline ecotone and beyond the tree limit is considered to be the best indicator of treeline sensitivity to environmental change. The sensitivity of climatic treelines to climate warming varies both in the local and regional topographical conditions. Furthermore, treeline history and its after‐effects also play an important role. The sensitivity of treelines to changes in given factors (e.g. winter snow pack, soil moisture, temperature, evaporation, etc.) may vary among areas with differing climatic characteristics. In general, forest will not advance in a closed front but will follow sites that became more favourable to tree establishment under the changed climatic conditions.