Impact of climate change on alpine vegetation of mountain summits in Norway

Climate change is affecting the composition and functioning of ecosystems across the globe. Mountain ecosystems are particularly sensitive to climate warming since their biota is generally limited by low temperatures. Cryptogams such as lichens and bryophytes are important for the biodiversity and functioning of these ecosystems, but have not often been incorporated in vegetation resurvey studies. Hence, we lack a good understanding of how vascular plants, lichens and bryophytes respond interactively to climate warming in alpine communities. Here we quantified long-term changes in species richness, cover, composition and thermophilization (i.e. the increasing dominance of warm-adapted species) of vascular plants, lichens and bryophytes on four summits at Dovrefjell, Norway. These summits are situated along an elevational gradient from the low alpine to high alpine zone and were surveyed for all species in 2001, 2008 and 2015. During the 15-year period, a decline in lichen richness and increase in bryophyte richness was detected, whereas no change in vascular plant richness was found. Dwarf-shrub abundance progressively increased at the expense of lichens, and thermophilization was most pronounced for vascular plants, but occurred only on the lowest summits and northern aspects. Lichens showed less thermophilization and, for the bryophytes, no significant thermophilization was found. Although recent climate change may have primarily caused the observed changes in vegetation, combined effects with non-climatic factors (e.g. grazing and trampling) are likely important as well. At a larger scale, alpine vegetation shifts could have a profound impact on biosphere functioning with feedbacks to the global climate.     

Effects of climate change,coal mining and grazing on vegetation dynamics in the mountain permafrost regions

The ecological environment in alpine regions is fragile and sensitive to land-use and land-cover (LULC) change and climate warming. However, there are limited studies on the response of LULC and vegetation activity to climate change and human interference in mountainous permafrost regions. Based on in-situ meteorological and multi-source remote sensing data, we performed time trend and partial correlation analyses to investigate the spatial and temporal variation of LULC, landscape pattern, and vegetation growth under the impact of climate change and human activities in the source region of the Datong River from 2000 to 2019. Our results showed that the alpine desert area decreased significantly at a rate of −13.1 km² yr⁻¹ (p < 0.05), while the alpine meadow area increased at a rate of 8.3 km² yr⁻¹ (p < 0.1). Mining and road areas showed a significant increasing trend at a rate of 3.2 km² yr⁻¹ and 1.2 km² yr⁻¹, respectively. The increasing alpine meadow and mining areas were mainly derived from alpine deserts and alpine wetlands, respectively. The number of alpine wetland patches increased significantly along with a significant decrease in the landscape shape index of the rivers. Vegetation growth, as indicated by the enhanced vegetation index (EVI) was positively correlated with temperature but negatively correlated with precipitation and solar radiation in 59.6%, 52.3%, and 56.5% of the vegetated areas, respectively (p < 0.05). Temperature was the dominant climate factor controlling vegetation dynamics, and the recent warming hiatus resulted in a significant increase in EVI for alpine deserts, but no significant changes in EVI for alpine wetlands and alpine meadows. Increasing risk of negative impacts from human activities, including mineral exploration and grazing, on vegetation distribution and growth was observed. This study provides clear evidence of the upward invasion of alpine meadows into alpine desert areas under warm and humid climatic conditions. As climate warming intensifies, alpine meadow expansion may be impeded by extreme precipitation and permafrost thawing.     

Littoral benthic macroinvertebrates of alpine lakes (Tatra Mts) along an altitudinal gradient: a basis for climate change assessment

Littoral benthic macroinvertebrates were studied in three alpine lakes in the High Tatra Mountains (Slovakia) located at different elevations: 2157, 1940 (alpine zone) and 1725 m (sub-alpine zone). The study sites were selected in order to obtain a gradient in thermal regimes and particular organic matter (POM). Differences in the faunal composition of lakes were tested for the ability of these differences to indicate climatic changes, and species/taxa were identified that could be used for the purposes of monitoring and climate change assessment. Macroinvertebrates were sampled quantitatively during the ice-free seasons of 2000 and 2001, and lake surface water temperature (LSWT) and POM were measured. LSWT and POM were negatively correlated with elevation, whereas ice cover was positively correlated with elevation. A total of 60 oligostenothermic macroinvertebrate species/taxa were collected belonging to ten higher taxonomic groups. Statistical analysis showed trends in several biotic metrics with altitude. More specifically, there was a clear increase in the number of species/taxa, genera, and higher taxonomic groups, as well as an increase in the Shannon–Wiener diversity with decreasing altitude. On the contrary, evenness and density of benthic macroinvertebrates did not show any clear relationship with altitude. Gatherers of detrital particles dominated the assemblages’ trophic structures, but no distinct changes in the proportion of functional feeding groups along the altitudinal gradient were found. While the non-insect fauna of the lakes was rather uniform across the elevational gradient, the insect fauna composition was highly correlated with altitude, as confirmed by Detrended Correspondence Analysis. Aquatic insects, in particular chironomids and caddisflies, can therefore be used as good indicators of temperature changes. Our results suggest that under warmer conditions, non-insect benthic macroinvertebrates will remain more or less stable, while aquatic insects will undergo an increase in the number of thermophilic species typical for lower altitudes. These colonizers will increase the diversity of alpine lakes, while the extinction of cold stenothermal species will lead to impoverishment of the native fauna. An indirect impact on benthic macroinvertebrates through changes in food sources is likely, and changes in trophic structure of the littoral assemblages can be expected.     

Plant species composition shifts in the Tatra Mts as a response to environmental change: a resurvey study after 90 years

Mountain vegetation is often considered highly sensitive to climate and land-use changes due to steep environmental gradients determining local plant species composition. In this study we present plant species compositional shifts in the Tatra Mts over the past 90 years and discuss the potential drivers of the changes observed. Using historical vegetation studies of the region from 1927, we resurveyed 76 vegetation plots, recording the vascular flora of each plot using the same methodology as in the original survey. We used an indirect method to quantify plant species compositional shifts and to indicate which environmental gradients could be responsible for these shifts: by calculating shifts in estimated species optima as reflected in shifts in the ecological indicator values of co-occurring species. To find shifts in species composition, focusing on each vegetation type separately, we used ordination (DCA). The species optimum changed significantly for at least one of the tested environmental gradients for 26 of the 95 plant species tested; most of these species changed in terms of the moisture indicator value. We found that the strongest shifts in species composition were in mylonite grassland, snowbed and hygrophilous tall herb communities. Changes in precipitation and increase in temperature were found to most likely drive compositional shifts in vegetation resurveyed. It is likely that the combined effect of climate change and cessation of sheep grazing has driven a species composition shift in granite grasslands communities.     

Increasing species richness on mountain summits: Upward migration due to anthropogenic climate change or re‐colonisation?

Abstract. Over the last 20 years, several studies comparing recent survey data with historical data from the early 20th century documented an increase in species numbers on high mountain summits of the European Alps. This increase has more or less explicitly been attributed to an upward migration of plant species due to anthropogenic climate warming. However, a reconsideration of the historical and recent data has revealed that more than 90% of the recent species occurrences on mountain summits concern species that were already present at the same or even at higher altitudes within the study region at the time of the historical surveys. This finding suggests that suitable habitats already occurred on these summits under the mesoclimatic conditions prevailing at the beginning of the 20th century and that these habitats were, at least in part, occupied by these plant species. Consequently, the observed increase in species number during the last century does not require the additional temperature increase due to anthropogenic climate change. We therefore consider the phenomenon of increasing species number on high mountain summits to be primarily the result of a natural dispersal process that was triggered by the temperature increase at the end of the Little Ice Age and that is still in progress mostly due to the dispersal limitation of the species involved. Since both the natural dispersal process and a potential upward migration due to anthropogenic climate warming would take place at the same time, we suggest seeding and transplanting experiments in order to assess their respective roles in the increase in species number on mountain summits.     

Consequences of abandonment for a regional fen flora and mechanisms of successional change

Abstract. Until the 1960s, species-rich vegetation on minero-trophic peaty soüs (fen sites) were characteristic of the alluvial plains in Schleswig-Holstein (Northwest Germany). Today, many of these habitats undergo successional changes due to abandonment. Vegetation development after abandonment can be characterized as a sequence of different successional stages and described in terms of a successional model. Successional stage I includes grazed, mown and recently abandoned sites without dominants. Stages II and III are characterized by the dominance of highly competitive herbaceous species whüe stage IV consists of woody vegetation. Ca. 3000 phytosociological relevés were assigned to the respective successional stages. Mean cover values were calculated for 250 species of the regional fen flora and assigned to successional categories according to their changes in cover in the successional series. According to our results 141 species decrease during succession, while 100 species were restricted to early successional stages and 85 species increased. Abandonment of all fen sites in Schleswig-Holstein will probably lead to the regional loss of 23 species of the fen flora. To identify mechanisms underlying successional change, the successional categories were correlated with life history traits and ecological requirements of the species. Results indicate that both light competition and limitation of sexual reproduction of small-seeded species might play a major role in the decrease and extinction of species during succession. Finally, conservation strategies for endangered species in a cultural landscape are discussed.     

Caddisfly assemblages of high mountain streams (The High Tatra Mts, Slovakia) influenced by a major windstorm event

Hydrobiological research of high mountain streams in the High Tatras was carried out in 2009–2010. We evaluated the influence of windstorm on caddisfly assemblages. To assess the influence of windstorm we focused on river morphology using the RHS method and evaluation of TAM, TOM and BOM (CPOM, FPOM, UFPOM) amount in seven streams. Site 1 was a control and the other six were disturbed by the windstorm in different ways. The most remarkable differences compared to the control site was in feeding structure at sites most affected by erosion. In these streams there was a noticeable dominance of predators from the family Rhyacophilidae (mainly Rhyacophila tristis; sites 3, 4, 5, 6) and a remarkable decrease of passive filter feeders (site 4, 5). Using Spearman coefficient we confirmed a positive correlation between the proportion of predators and amount of TAM caused by erosion of steep deforested slopes of windstorm affected sites. In contrast, we did not observe such an increase in the proportion of predators at site 7, which was affected by both windstorm and subsequently by fire. This might be explained by the shallow vee valley with no observed erosion, where this site is situated. We also found a negative correlation between predators and evenness, indicating unstable community structure clearing succesion in the streams disturbed by erosion, and a negative correlation between passive filter feeders and UFPOM. We found out that overhanging tree boughs and LWD had an influence on species composition. RHS was a useful tool in characterising the influence of hydromorphology on caddisfly assemblages.     

未来气候变化对山地生物气候类型分布的影响--以四川省为例

使用生物气候分类法评估气候变化下生态系统变化的区域,对于气候变化下生态系统的保护有着重要的意义。但是现有的研究由于分析尺度较大,难以反映气候变化对于山地生态系统的影响。选取四川省为研究区,使用区域气候模型(Reg CM4.0)对未来气候变化进行预估,在此基础上按照柯本生物气候分类法划分原则,分别对当前1981—2010,未来2011—2040,2031—2060以及2070—2099时段四川省柯本气候类型进行识别并分析各类型的转变。结果表明(1)当前四川省分布的柯本气候类型共包括3个主要类型,分别为暖温带气候带(C),冷温带气候带(D),极地气候带(E),其面积分别占四川省总面积的54%,22%和24%。(2)在未来各时段内,四川省柯本气候类型总体分布格局并无明显变化。但是未来气候变化程度足以使得部分区域内的生物气候类型发生转变,其中最大的转变发生于E类型向D类型的转变。相比当前时段,到2070—2099时段C类型和D类型增加面积占当前分布面积的13%和20%,E类型减少面积占当前分布面积的48%。对比不同时段的转变速率,近期的气候变化对于生物气候类型的影响要大于远期的气候变化。(3)由于受气候变化的影响,各柯本气候类型分布的平均海拔均向高海拔区域上移,C类,D类和E类型分布平均海拔的上移速率分别为2.9,3.4 m/a和1.8 m/a。此外,经统计生物气候类型发生变化区域的海拔主要为3800—4500 m。     

Dispersal and climate change: a case study of the Arctic tern Sterna paradisaea

Dispersal is an important evolutionary process that can affect admixture of populations and cause rapid responses to changing climatic conditions due to gene flow from populations at different altitudes or latitudes already experiencing these conditions. We investigated long-term patterns of natal and breeding dispersal in a coastal seabird, the Arctic tern Sterna paradisaea , that experiences specific climatic conditions in the northern temperate and Arctic climate zones during breeding and different climatic conditions in the Antarctic during winter. Long natal and breeding dispersal distances were costly as shown by their effects on delayed breeding. Dispersal distances varied significantly among years, with natal dispersal showing a strong temporal increase during the last 70 years. Annual differences in dispersal distance could be accounted for by climate conditions in the breeding grounds and the winter quarters. Natal dispersal was related to climate conditions in both the year of hatching and the year of breeding, whereas breeding dispersal was only related to climate conditions in the second year of the dispersal event. Only the north Atlantic oscillation (NAO) index for winter showed a consistent temporal trend, suggesting that the temporal trend in natal dispersal distance must be caused by changes in the NAO (or associated phenomena). These findings indicate that dispersal can change rapidly in response to changing climate conditions.     

Effects of the progressive abandonment of grazing on dung beetle biodiversity: body size matters

Dung beetles are an ecologically important group of insect species inhabiting semi-natural grasslands in Europe. Despite their ecological importance, several dung beetle species are currently facing local threats mainly stemming from changes in land use practices, including the abandonment of pasturelands. The aim of this study was to analyze the impact of the progressive abandonment of grazing lands on dung beetle alpha diversity, abundance, biomass and body size classes. Areas representing a range of trophic resource availability were compared: (i) abandoned, (ii) low and (iii) moderate grazing intensity. A total of 136,884 specimens belonging to 56 species (3 Geotrupinae; 16 Scarabaeinae; 37 Aphodiinae) of dung beetle were collected. Pastureland abandonment was shown to lead to a decrease in alpha diversity and biomass density, a reduction of 22 and 78% respectively in abandoned areas. From a biomass standpoint, the effects of pastureland abandonment varied according to the body size classes of the dung beetles, with larger species proving more susceptible to local extinction. Such body-size dependent variations led us to propose the use of both biomass and abundance data in making assessments since they are differentially sensitive to trophic resource availability. Hence, from a conservationist standpoint, the obtained results suggest that traditional pastureland management with low-moderate grazing intensity should be maintained.     

Parapatric species and the implications for climate change studies: a case study on hares in Europe

Parapatry is a biogeographical term used to refer to organisms whose ranges do not overlap, but are immediately adjacent to each other; they only co‐occur – if at all – in a narrow contact zone. Often there are no environmental barriers in the contact zones, hence competitive interaction is usually advocated as the factor that modulates species distribution ranges. Even though the effects of climate change on species distribution have been widely studied, few studies have explored these effects on the biogeographical relationships between closely related, parapatric, species. We modelled environmental favourability for three parapatric hare species in Europe – Lepus granatensis, L. europaeus and L. timidus – using ecogeographical variables and projected the models into the future according to the IPCC A2 emissions scenario. Favourabilities for present and future scenarios were combined using fuzzy logic with the following aims: (i) to determine the biogeographical relationships between hare species in parapatry, that is L. granatensis/L. europaeus and L. europaeus/L. timidus and (ii) to assess the effects of climate change on each species as well as on their interspecific interactions. In their contact area L. granatensis achieved higher favourability values than L. europaeus, suggesting that if both species have a similar population status, the former species may have some advantages over the latter if competitive relationships are established. Climate change had the most striking effect on the distribution of L. timidus, especially when interspecific interactions with L. europaeus were taken into account, which may compromise the co‐existence of L. timidus. The results of this study are relevant not only for understanding the distribution patterns of the hares studied and the effects of climate change on these patterns, but also for improving the general application of species distribution models to the prediction of the effects of climate change on biodiversity.     

Effects on heather of heavy grazing by mountain hares

Continual heavy grazing of small patches of heather by mountain hares produces conspicuous, short, lawn-like bushes. Their probable development is described. The shoots of such heather bushes maintained a juvenile appearance, contained more nitrogen and phosphorus than the surrounding heather and, to judge from their chemical composition, were more digestible. The generalization that tree and shrub twigs of juvenile growth form are more unpalatable to hares than twigs of mature growth form did not apply in this case.     

The effects of climate change on species composition,succession and phenology: a case study

Climate change and its role in altering biological interactions and the likelihood of invasion by introduced species in marine systems have received increased attention in recent years. It is difficult to forecast how climate change will influence community function or the probability of invasion as it alters multiple marine environmental parameters including rising water temperature, lower salinity and pH. In the present study, we correlate changes in environmental parameters to shifts in species composition in a subtidal community in Newcastle, NH through comparison of two, 3‐year periods separated by 23 years (1979–1981 and 2003–2005). We observed concurrent shifts in climate related factors and in groups of organisms that dominate the marine community when comparing 1979–1981 to 2003–2005. The 1979–1981 community was dominated by perennial species (mussels and barnacles). In contrast, the 2003–2005 community was dominated by annual native and invasive tunicates (sea‐squirts). We also observed a shift in the environmental factors that characterized both communities. Dissolved inorganic nitrogen and phosphate characterized the 1979–1981 community while sea surface temperature, pH, and chlorophyll a characterized the 2003–2005 community. Elongated warmer water temperatures, through the fall and early winter months of the 2000s, extended the growing season of native organisms and facilitated local dominance of invasive species. Additionally, beta‐diversity was greater between 2003–2005 than 1979–1981 and driven by larger numbers of annual species whose life‐history characteristics (e.g., timing and magnitude of recruitment, growth and mortality) are driven by environmental parameters, particularly temperature.     

气候和放牧对锡林郭勒地区植被覆盖变化的影响

基于锡林郭勒盟15个气象站点1981-2007年的逐月气温、降水量数据及各旗县的牲畜头数,在ArcGIS软件的支持下,分析气候干燥度和牲畜密度的空间分布,结合1981-2007年的逐旬归一化植被指数(NDVI)数据,对研究区植被覆盖变化的驱动因素进行分析.结果表明:研究期间,锡林郭勒盟气候干燥度与植被覆盖状况之间存在良好的线性回归关系;NDVI与牲畜密度之间存在良好的二项式回归关系,随着NDVI值的升高,牲畜密度先增加后降低;植被覆盖状况与干燥度和牲畜密度呈复线性相关关系,其中,NDVI与干燥度呈正相关,与牲畜密度呈负相关,且干燥度对NDVI的影响远大于牲畜密度对NDVI的影响.     

基于结构方程模型的高寒生态脆弱区农户的气候变化感知研究——以甘南高原为例

农户对气候变化的感知是其适应行动选择的基础,弄清楚影响农户气候变化感知的关键因素,辨明农户气候变化感知的形成机制,对制定有效的适应策略至关重要。以甘南高原为研究区,基于539份入户调查数据,构建了路径模型,分析了影响农牧户气候变化感知的关键因素及其作用路径,结果发现:(1)客观适应能力对农牧户的气候变化风险感知及适应感知有显著的正向影响;(2)气候变化信息对农牧户的气候变化风险感知及适应感知有显著的正向影响,它还通过客观适应能力间接影响农牧户的气候变化感知;(3)社会话语信任度对农牧户的气候变化风险感知及适应感知有显著的正向影响,适应激励对农牧户的气候变化适应感知有显著的正向影响,但对风险感知产生显著的负向影响,同时,社会话语信任度及适应激励均通过气候变化信息及客观适应能力而间接影响农牧户的气候变化感知。最后,基于影响甘南高原农牧户气候变化感知的关键因素,提出了提高农牧户的气候变化认知水平及气候变化适应行为有效性的对策建议。     

Indexing variability: A case study with climate change impacts on ecosystems

We developed a methodology to index statistical changes in the variance of ecological measures over time. While ecological indicators are used to assess ecosystem health, vulnerability, risk and damage to ecosystems, their primary focus has been on changes to the mean of the ecological state or process. Little work has been done on incorporating variability into ecological indices. The methodology developed here is based on the Modified Levene's test of variance and a moving block where an initial time period (block) of ecosystem behavior is compared to the moving block. This allows for the detection of not only shifts in variance but also the magnitude of the shift on a continuous basis. Our results compared well with the benchmarked results from the Centered Cumulative Sum of Squares Algorithm (CUSUM) for detection of variance changes in fixed time series. The output from this methodology is a continuous stream of parameters (significant variance shift, magnitude of the shift, and the direction of the variance shift) suitable for indexing variance or integrating into an index measuring ecosystem change. Results suggest that the block interval widths should be at least 50 and that a smoothing factor of five be used to avoid false positives. We used modeled vegetation carbon output to analyze the utility of the methodology, illustrating that different model assumptions and CO₂ regimes affect the variability of the ecological response. The degree of risk resource managers may want to explore can be altered by choices in the block length, the length of the string used to smooth variance shifts, the assumption that the initial period has constant variance and the alpha levels used to determine statistical significance.     

Effects of temperature and elevation on habitat use by a rare mountain butterfly: implications for species responses to climate change

Abstract 1. The present study used the mountain specialist butterfly Parnassius apollo as a model system to investigate how climate change may alter habitat requirements for species at their warm range margins. 2. Larval habitat use was recorded in six P. apollo populations over a 700 m elevation gradient in the Sierra de Guadarrama (central Spain). Larvae used four potential host species (Sedum spp.) growing in open areas amongst shrubs. 3. Parnassius apollo host‐plant and habitat use changed as elevation increased: the primary host shifted from Sedum amplexicaule to Sedum brevifolium, and larvae selected more open microhabitats (increased bare ground and dead vegetation, reduced vegetation height and shrub cover), suggesting that hotter microhabitats are used in cooler environments. 4. Larval microhabitat selection was significantly related to ambient temperature. At temperatures lower than 27 °C, larvae occupied open microhabitats that were warmer than ambient temperature, versus more shaded microhabitats that were cooler than ambient conditions when temperature was higher than 27 °C. 5. Elevational changes in phenology influenced the temperatures experienced by larvae, and could affect local host‐plant favourability. 6. Habitat heterogeneity appears to play an important role in P. apollo larval thermoregulation, and may become increasingly important in buffering populations of this and other insect species against climatic variation.     

Effects of grazing on above-ground biomass on a mountain snowbed, NW Finland

The density-dependent effect of induced plant resistance on herbivore populations depends on the relationship between the amount of herbivore damage and the level of induced resistance produced by the plant. This relationship should influence the interaction of induced resistance and herbivore population dynamics, and if the relationship varies among plant genotypes, it could be subject to natural selection by herbivores. In this study the relationship between percent leaf area damaged and level of induced resistance was characterized for four genotypes of soybeans grown in a greenhouse. Damage ranging from 8 to 92% of leaf area was imposed using Mexican bean beetle larvae, and induced resistance was measured by bioassay using Mexican bean beetle adults. The level of induced resistance was significantly affected by the amount of damage, and the level of induced resistance varied significantly among the four genotypes. There was also a marginally significant interaction of damage and plant genotype, suggesting that the form of density dependence varies among these four genotypes of soybeans. These results suggest that these genotypes of plants might affect herbivore populations differently. If this variation is heritable, the form of density-dependent effects of induced resistance has the potential to evolve in this system.     

Effects of differential grazing on decomposition rate and nitrogen availability in a productive mountain grassland

Background and aims

Grazing may influence nutrient cycling in several ways. In productive mountain grasslands of central Argentina cattle grazing maintain a mosaic of different vegetation patches: lawns, grazed intensively and dominated by high quality palatable plants, and open and closed tussock grasslands dominated by less palatable species. We investigated if differences in the resources deposited on soil (litter and faeces) were associated with litter decomposition rates and soil nitrogen (N) availability across these vegetation patches.

Methods

We compared the three vegetation patches in terms of litter and faeces quality and decomposability, annual litterfall and faeces deposition rate. We determined decomposition rates of litter and faces in situ and decomposability of the same substrates in a common garden using “litter bags”. We determined soil N availability (with resin bags) in the vegetation patches. Also, we performed a common plant substrates decomposition experiment to assess the effect of soil environment on decomposition process. This technique provides important insights about the soil environmental controls of decomposition (i.e. the sum of soil physicochemical and biological properties, and microclimate), excluding the substrate quality.

Results

The litter quality and faeces deposition rate were higher in grazing lawns, but the total amounts of carbon (C) and nitrogen (N) deposited on soil were higher in tussock grasslands, due to higher litterfall in these patches. The in situ decomposition rates of litter and faeces, and of the two common plant substrates were not clearly related to either grazing pressure, litterfall or litter quality (C, N, P, lignin, cellulose or hemicellulose content). In situ litter decomposition rate and soil ammonium availability were correlated with the decomposition rates of both common plant substrates. This may suggest that difference in local soil environment among patch types is a stronger driver of decomposition rate than quality or quantity of the resource that enter the soil.

Conclusions

Our results show that, although high grazing pressure improves litter quality and increases faeces input, the reduction in biomass caused by herbivores greatly reduces C and N input for the litter decomposition pathway. We did not find an accelerated decomposition rate in grazing lawns as proposed by general models. Our results point to soil environment as a potential important control that could mask the effect of litter quality on field decomposition rates at local scale.     

Lags in the response of mountain plant communities to climate change

Rapid climatic changes and increasing human influence at high elevations around the world will have profound impacts on mountain biodiversity. However, forecasts from statistical models (e.g. species distribution models) rarely consider that plant community changes could substantially lag behind climatic changes, hindering our ability to make temporally realistic projections for the coming century. Indeed, the magnitudes of lags, and the relative importance of the different factors giving rise to them, remain poorly understood. We review evidence for three types of lag: “dispersal lags” affecting plant species’ spread along elevational gradients, “establishment lags” following their arrival in recipient communities, and “extinction lags” of resident species. Variation in lags is explained by variation among species in physiological and demographic responses, by effects of altered biotic interactions, and by aspects of the physical environment. Of these, altered biotic interactions could contribute substantially to establishment and extinction lags, yet impacts of biotic interactions on range dynamics are poorly understood. We develop a mechanistic community model to illustrate how species turnover in future communities might lag behind simple expectations based on species’ range shifts with unlimited dispersal. The model shows a combined contribution of altered biotic interactions and dispersal lags to plant community turnover along an elevational gradient following climate warming. Our review and simulation support the view that accounting for disequilibrium range dynamics will be essential for realistic forecasts of patterns of biodiversity under climate change, with implications for the conservation of mountain species and the ecosystem functions they provide.