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Spatial mid-domain effect overrides climate, soil properties and microbes on a cosmopolitan non-native plant across elevation
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Introduction
Erigeron philadelphicus and Erigeron annuus are two ecologically destructive invasive plants from the Asteraceae family. Predicting the potential distribution pattern of two invasive alien Erigeron weeds can provide a scientific basis for prevent the further spread of these two weeds in China under climate change.
Methods
Based on historical occurrence datasets and environmental variables, we optimized a MaxEnt model to predict the potential suitable habitats of E. philadelphicus and E. annuus. We also analyzed the shifts of distribution centroids and patterns under climate change scenarios.
Results
The key variables that affect the potential geographical distribution of E. annuus and E. philadelphicus, respectively, are temperature seasonality and precipitation of the driest month. Moreover, topsoil sodicity and topsoil salinity also influence the distribution of E. philadelphicus. Under climate change, the overall suitable habitats for both invasive alien Erigeron weeds are expected to expand. The potential geographical distribution of E. annuus exhibited the highest expansion under the SSP245 climate scenario (medium forcing scenarios), whereas E. philadelphicus had the highest expansion under the SSP126 climate scenario (lower forcing scenarios) globally. The future centroid of E. annuus is projected to shift to higher latitudes specifically from Hubei to Hebei, whereas E. philadelphicus remains concentrated primarily in Hubei Province. The overlapping suitable areas of the two invasive alien Erigeron plants mainly occur in Jiangsu, Zhejiang, Fujian, Jiangxi, Hunan, Guizhou, and Chongqing, within China.
Discussion
Climate change will enable E. annuus to expand into northeastern region and invade Yunnan Province whereas E. philadelphicus was historically the only suitable species. E. annuus demonstrates a greater potential for invasion and expansion under climate change, as it exhibits higher environmental tolerance. The predictive results obtained in this study can serve as a valuable reference for early warning systems and management strategies aimed at controlling the spread of these two invasive plants.
Landslides cause significant disturbances to mountainous ecosystems and human activities. Due to climate change, the frequency of landslides as secondary disasters has notably increased compared to the past. Further exploration is needed to understand the effects of different restoration methods on post-landslide plant communities and soil properties over different periods of time. In this regard, we selected Lantian County in the northern foothills of the Qinling Mountains as our study area. We conducted surveys on artificially restored and naturally recovered plots at 1, 6, and 11 years after landslide events. Undamaged areas were chosen nearby as control plots. We identified vegetation types and species diversity after artificial and natural recovery and further analyzed the impact of different restoration strategies on vegetation patterns and soil properties. The research results indicate that, compared with natural recovery, artificial restoration can more quickly improve vegetation and soil. With the increasing time gradient, the average ground cover of the herbaceous layer in natural recovery decreased gradually from 47% at year one to 34% at year eleven. In contrast, in artificial restoration, the average ground cover of the herbaceous layer increased from 27% at year one to 44% at year eleven. For the shrub layer, in natural recovery, the average ground cover gradually increased to 39% over eleven years. While in artificial restoration, the average ground cover for the shrub layer gradually increased to 46% over the same period. In the artificial restoration plots, soil pH gradually increased (from 6.2 to 8.2), while TN content gradually decreased (from 1.7 g/kg to 0.9 g/kg). Similarly, TK content decreased (from 22.4 g/kg to 14.5 g/kg), and AP content showed a decreasing trend (from 20.7 mg/kg to 11.4 mg/kg). In the natural recovery plots, DNA content gradually increased (from 3.2 μg/g/d to 142.6 μg/g/d), and SC content gradually increased as well (from 2.4 mg/d/g to 23.1 mg/d/g). In contrast, on sites undergoing natural recovery, the short-term restoration rates of vegetation and soil are lower, but they show greater stability over a longer time. This study provides a new perspective on vegetation restoration strategies and is expected to offer insights for the optimization of post-landslide recovery in the future.
High-elevation ecosystems are among the few ecosystems worldwide that are not yet heavily invaded by non-native plants. This is expected to change as species expand their range limits upwards to fill their climatic niches and respond to ongoing anthropogenic disturbances. Yet, whether and how quickly these changes are happening has only been assessed in a few isolated cases. Starting in 2007, we conducted repeated surveys of non-native plant distributions along mountain roads in 11 regions from 5 continents. We show that over a 5- to 10-year period, the number of non-native species increased on average by approximately 16% per decade across regions. The direction and magnitude of upper range limit shifts depended on elevation across all regions. Supported by a null-model approach accounting for range changes expected by chance alone, we found greater than expected upward shifts at lower/mid elevations in at least seven regions. After accounting for elevation dependence, significant average upward shifts were detected in a further three regions (revealing evidence for upward shifts in 10 of 11 regions). Together, our results show that mountain environments are becoming increasingly exposed to biological invasions, emphasizing the need to monitor and prevent potential biosecurity issues emerging in high-elevation ecosystems. The authors resurveyed a previously sampled set of mountain transects on five continents, showing that the ranges of non-native plant species have shifted upslope in most locations in just 5–10 years.
Purpose
Understanding the root traits associated with plant invasions has become increasingly essential. This study examined the root characteristics associated with aboveground water use in invasive plants under variable water conditions with the aim of improving our understanding of invasive plant performance.
Methods
Root morphological and physiological traits, and water use parameters associated with water use efficiency were compared in five invasive and five congeneric or phylogenetically close native Compositae plants under well-watered and drought stress conditions.
Results
Under drought stress, the invasive plants, compared with the native plants, presented a more positive root and leaf water potential, longer fine roots (diameter ≤ 0.5 mm), higher specific root length, and lower water consumption. Moreover, invasive plants maintained a larger biomass, greater instantaneous water use efficiency and biomass water use efficiency than the native plants, although drought inhibited growth in both invasive and native plants. Regardless of the water conditions, invasive plants showed similar root hydraulic conductivity with native plants. Changes in water use efficiency in the invasive plants were mainly correlated with the fine root length (diameter ≤ 1 mm), specific root length, and root water potential; however, in native plants, only the fine root length (diameter ≤ 1 mm) showed a correlation, regardless of the water conditions.
Conclusion
Together, a more positive root water potential, and longer fine roots (diameter ≤ 1 mm) are associated with improvements in water use efficiency and drought tolerance in invasive plants, suggesting these physiological and morphological root traits form part of the plant growth strategy employed by successful invasive species.
The premise that the intensity of biotic interactions decreases with increasing latitudes and elevations is broadly accepted; however, whether these geographical patterns can be explained within a common theoretical framework remains unclear. Our goal was to identify the general pattern of elevational changes in trophic interactions and to explore the sources of variation among the outcomes of individual studies. Meta‐analysis of 226 effect sizes calculated from 134 publications demonstrated a significant but interaction‐specific decrease in the intensity of herbivory, carnivory and parasitism with increasing elevation. Nevertheless, this decrease was not significant at high latitudes and for interactions involving endothermic organisms, for herbivore outbreaks or for herbivores living within plant tissues. Herbivory similarly declined with increases in latitude and elevation, whereas carnivory showed a fivefold stronger decrease with elevation than with latitude and parasitism increased with latitude but decreased with elevation. Thus, although these gradients share a general pattern and several sources of variation in trophic interaction intensity, we discovered important dissimilarities, indicating that elevational and latitudinal changes in these interactions are partly driven by different factors. We conclude that the scope of the latitudinal biotic interaction hypothesis cannot be extended to incorporate elevational gradients.
Mountains are pivotal to maintaining habitat heterogeneity, global biodiversity, ecosystem functions and services to humans. They have provided classic model natural systems for plant and animal diversity gradient studies for over 250 years. In the recent decade, the exploration of microorganisms on mountainsides has also achieved substantial progress. Here, we review the literature on microbial diversity across taxonomic groups and ecosystem types on global mountains. Microbial community shows climatic zonation with orderly successions along elevational gradients, which are largely consistent with traditional climatic hypotheses. However, elevational patterns are complicated for species richness without general rules in terrestrial and aquatic environments and are driven mainly by deterministic processes caused by abiotic and biotic factors. We see a major shift from documenting patterns of biodiversity towards identifying the mechanisms that shape microbial biogeographical patterns and how these patterns vary under global change by the inclusion of novel ecological theories, frameworks and approaches. We thus propose key questions and cutting‐edge perspectives to advance future research in mountain microbial biogeography by focusing on biodiversity hypotheses, incorporating meta‐ecosystem framework and novel key drivers, adapting recently developed approaches in trait‐based ecology and manipulative field experiments, disentangling biodiversity–ecosystem functioning relationships and finally modelling and predicting their global change responses.
Recently, a new annotation tool "FungalTraits" was created based on the previous FUNGuild and Fun Fun databases, which has attracted high attention in the scientific community. These databases were widely used to gain more information from fungal sequencing datasets by assigning fungal functional traits. More than 1500 publications so far employed FUNGuild and the aim of this study is to compare this successful database with the recent FungalTraits database. Quality and quantity of the assignment by FUNGuild and FungalTraits to a fungal internal transcribed spacer (ITS)-based amplicon sequencing dataset on amplicon sequence variants (ASVs) were addressed. Sequencing dataset was derived from leaves and needles of 12 temperate broadleaved and coniferous tree species. We found that FungalTraits assigned more functional traits than FUNGuild, and especially the coverage of saprotrophs, plant pathogens, and endophytes was higher while lichenized fungi revealed similar findings. Moreover, ASVs derived from leaves and needles of each tree species were better assigned to all available fungal traits as well as to saprotrophs by FungalTraits compared to FUNGuild in particular for broadleaved tree species. Assigned ASV richness as well as fungal functional community composition was higher and more diverse after analyses with FungalTraits compared to FUNGuild. Moreover, datasets of both databases showed similar effect of environmental factors for saprotrophs but for endophytes, unidentical patterns of significant corresponding factors were obtained. As a conclusion, FungalTraits is superior to FUNGuild in assigning a higher quantity and quality of ASVs as well as a higher frequency of significant correlations with environmental factors.
The significant portion of global terrestrial biodiversity harboured in the mountains is under increasing threat from various anthropogenic impacts. Protecting fragile mountain ecosystems requires understanding how these human disturbances affect biodiversity. As roads and railways are extended further into mountain ecosystems, understanding the long‐term impacts of this infrastructure on community composition and diversity gains urgency.
We used railway corridors constructed across the mountainous landscapes of the Kashmir Himalaya from 1994 to 2013 to study the effects of anthropogenic disturbance on species distributions and community dynamics. In 2014 and 2017, we collected vegetation data along 31 T‐shaped transects laid perpendicular to the railway line, adopting the MIREN (Mountain Invasion Research Network) road survey methodology.
Plant communities shifted significantly from 2014 to 2017, potentially because of an ongoing species redistribution after railway construction, driven mainly by declines in both native and non‐native species richness, and an increasing abundance of a few non‐native species, especially in areas away from the railway track.
These patterns indicate an advancing succession, where initially—rare—pioneer species are replaced by increasingly dominant and often non‐native competitors, and potentially suggest a trend towards delayed local extinctions after the disturbance event. Native and non‐native species richness was negatively correlated with elevation, but that relationship diminished over time, with the abundance of non‐natives significantly increasing at higher elevations.
Synthesis and applications. Transport corridors seem to facilitate the spread of non‐native species to higher elevations, which has serious implications considering the warming mountain tops. Our results indicate that the plant communities next to railways do not reach equilibrium quickly after a disturbance. More than 10 years after railway establishment within Kashmir Himalaya, succession continued, and signs pointed towards a landscape increasingly dominated by non‐native species. Our study indicates that the single disturbance event associated with constructing railway in this Himalayan region had large and long‐lasting effects on plant communities at and around this transport corridor and suggests the need for a long‐term region‐wide coordinated monitoring and management program.
Detecting shifts in trait values among populations of an invasive plant is important for assessing invasion risks and predicting future spread. Although a growing number of studies suggest that the dispersal propensity of invasive plants increases during range expansion, there has been relatively little attention paid to dispersal patterns along elevational gradients. In this study, we tested the differentiation of dispersal-related traits in an invasive plant, Galinsoga quadriradiata, across populations at different elevations in the Qinling and Bashan Mountains in central China. Seed mass–area ratio (MAR), an important seed dispersal-related trait, of 45 populations from along an elevational gradient were measured, and genetic variation of 23 populations were quantified using inter-simple sequence repeat (ISSR) markers. Individuals from four populations were then planted in a greenhouse to compare their performance under shared conditions. Changing patterns of seed dispersal-related traits and populations genetic diversity along elevation were tested using linear regression. MAR of G. quadriradiata increased, while genetic diversity decreased with elevation in the field survey. In the greenhouse, populations of G. quadriradiata sourced from different elevations showed a difference response of MAR. These results suggest that although rapid evolution may contribute to the range expansion of G. quadriradiata in mountain ranges, dispersal-related traits will also likely be affected by phenotypic plasticity. This challenges the common argument that dispersal ability of invasive plants increases along dispersal routes. Furthermore, our results suggest that high-altitude populations would be more effective at seed dispersal once they continue to expand their range downslope on the other side. Our experiment provides novel evidence that the spread of these high-altitude populations may be more likely than previously theorized and that they should thus be cautiously monitored.
The mid-domain effect (MDE) explains altitudinal patterns of species diversity of mountainous plants at different elevations. However, its application is limited by the species life form and family flora in different layers of plant communities. To verify the MDE hypothesis at the plant community level, we chose a mountain with representative characteristics of the study area in the east of the Loess Plateau, China, such as obvious elevation (from 1324 to 2745 m) and latitude (from 36° 23′ to 39° 03′) gradients and considerable vegetation types (mainly coniferous and broad-leaved forests). We measured the life forms, families, and species diversity indices of tree, shrub, and herb communities along different elevations. We determined that the family numbers of the herb and shrub communities presented unimodal patterns across an altitudinal gradient, and the highest values occurred at intermediate elevations. The importance values of dominant families in the shrub and tree communities presented unimodal patterns, but the lowest values occurred at intermediate elevations. The species diversity indices of the herb, shrub, and tree communities conformed to unimodal change patterns following an altitudinal gradient, but the greatest diversity occurred at high, low, and intermediate elevations, respectively. At higher elevations, forbs and grasses grew well, whereas sedges grew well at lower elevations. Responses of different tree life forms to the altitudinal gradient were greater for evergreen coniferous tree species than for deciduous coniferous and deciduous broad-leaved tree species. We concluded that the MDE hypothesis of species diversity for mountainous plants is influenced greatly by the community life form and family at the plant community level in a temperate semi-arid region of the Loess Plateau, China. This conclusion tested and modified the MDE hypothesis and may be valuable for fueling prediction of biodiversity models and for the comparison with similar studies in arid and semi-arid mountainous regions.
Aim
Biological invasions threaten biodiversity globally. Large‐scale studies of non‐native plant species invasiveness typically focus on identifying ecological differences between naturalized and invasive species that account for their spread from sites of initial establishment (i.e., invasion success). However, invasive species differ widely in the magnitude of their impacts, suggesting the characteristics that favour invasion success might not necessarily predict the consequences of that invasion. Here we test whether those factors that increase the probability of plant species invasion also explain the severity of impacts.
Location
China.
Methods
We compiled a database of the invasiveness, biogeographic origins, life history traits, and introduction history for 538 non‐native plants in China and modelled differences in (a) naturalized and invasive species; (b) the spatial extent of invasion; and, (c) the severity of invasion impacts among successful invaders.
Results
Invasion success and the spatial extent of invasion shared similar influencing factors. However, these clearly differed from the predictors of severe invasion impacts. Unintentionally introduced non‐native plants with shorter life cycles and longer residence times were more likely to become invasive and to invade a larger area, while taller plants introduced from the Americas tended to have more severe impacts on the native ecosystems of China.
Main Conclusions
These results illustrate the different roles of introduction history, biogeographical origin and biological traits in determining the invasion success and spatial extent of invasion versus the severity of invasive species impacts. We suggest that factors associated with evolutionary adaptation and population expansion might determine invasion success and extent, while traits related to the relative competitive ability of invasive species determine the severity of impacts. Identifying specific characteristics of species that distinguish among successful invaders most likely to result in more severe impacts could help with planning more effective interventions.
Plant and animal community composition changes at higher elevations on mountains. Plant and animal species richness generally declines with elevation, but the shape of the relationship differs between taxa. There are several proposed mechanisms, including the productivity hypotheses; that declines in available plant biomass confers fewer resources to consumers, thus supporting fewer species. We investigated resource availability as we ascended three aspects of Helvellyn mountain, UK, measuring several plant nutritive metrics, plant species richness and biomass. We observed a linear decline in plant species richness as we ascended the mountain but there was a unimodal relationship between plant biomass and elevation. Generally , the highest biomass values at mid-elevations were associated with the lowest nutritive values, except mineral contents which declined with elevation. Intra-specific and inter-specific increases in nutritive values nearer the top and bottom of the mountain indicated that physiological, phenological and compositional mechanisms may have played a role. The shape of the relationship between resource availability and elevation was different depending on the metric. Many consumers actively select or avoid plants based on their nutritive values and the abundances of consumer taxa vary in their relationships with elevation. Consideration of multiple nutritive metrics and of the nutritional requirements of the consumer may provide a greater understanding of changes to plant and animal communities at higher elevations. We propose a novel hypothesis for explaining elevational diversity gradients, which warrants further study; the 'nutritional complexity hypothesis', where consumer species coexist due to greater variation in the nutritional chemistry of plants.
The success of invasive plant species can be evaluated using different dimensions, such as, range size, abundance and impact. These different dimensions do not always covary but are rarely separated, suggesting an urgency to disentangle the functional mechanisms behind them.
A dataset of leaf traits and four dimensions of invasion success (i.e. range size, local abundance, impact on native plant abundance and impact on native plant diversity) were compiled for 395 non‐native plant species in the US and Europe. Associations among dimensions of invasion success and between leaf traits and dimensions were analysed with general linear models (LMs) and supplemented by phylogenetic generalized least square (PGLS) models, which control for the phylogenetic relatedness across species.
The pair‐wise associations between most pairs of invasion dimensions were weak or neutral. The only exception was the association between impact on native plant abundance and impact on native plant diversity, which was strongly positive. Traits of species that have large range sizes were associated with a high metabolic rate; whereas, traits of species that were abundant or had a strong impact at the local scale were associated with low metabolic rate. In addition, traits of species with a large range size or having strong impacts on native plant abundance were associated with acquisitive strategies; whereas, traits of species with a high local abundance or strong impacts on native plant diversity were associated with conservative strategies.
Synthesis. Different dimensions of invasion success were associated with different functional traits. Invasion success at the regional scale was related to traits that promote rapid colonization; whereas, invasion success at the local scale was related to traits that are potentially less preferred by herbivores. Some locally successful invaders even possessed traits that facilitate a high stress tolerance and conservative strategy, which were similar to locally abundant native species. Therefore, an ambiguous definition of ‘invasion success’ in mechanism‐related studies may produce inconsistent or even controversial conclusions, highlighting the importance of separately studying different dimensions of invasion success.
The biogeographic origin of species may help to explain differences in average tree height and aboveground biomass (AGB) of tropical mountain forests. After the Andean uplift, small‐statured trees should have been among the initial colonizers of the highlands (new cold environment) from the lowland tropics, since these species are pre‐adapted to cold conditions with narrow vessels that are relatively resistant to freezing. If the descendants of these small‐statured clades continue to dominate tropical highland forests, there will be a high co‐occurrence of close relatives at high elevations. In other words, this scenario predicts a systematic decline in tree size, AGB, and phylogenetic diversity with elevation. In contrast, the colonization of Andean forests by some large‐statured clades that originated in temperate regions may modify this expectation and promote a mixing of tropical and temperate clades, thereby increasing the phylogenetic diversity in tropical highland forests. This latter scenario predicts an increase or no change of tree size, AGB, and phylogenetic diversity with elevation. We assessed how the historical immigration of large‐statured temperate‐affiliated tree lineages adapted to cold conditions may have influenced the composition and structure of Andean forests. Specifically, we used 92 0.25‐ha forest inventory plots distributed in the tropical Andes Mountains of Colombia to assess the relationship between the phylogenetic diversity and AGB along elevational gradients. We classified tree species as being either “tropical affiliated” or “temperate affiliated” and estimated their independent contribution to forest AGB. We used structural equation modeling to separate the direct and indirect effect of elevation on AGB. We found a hump‐shaped relationship of phylogenetic diversity, AGB, and tree size with elevation. The high phylogenetic diversity found between 1,800–2,200 m above sea level (asl) was due to the mixing of highland floras containing many temperate‐affiliated species, and lowland floras containing mostly tropical‐affiliated species. The high AGB in highland forests, which contrasted with the expected decline of AGB with elevation, was likely due to the significant contribution of temperate‐affiliated species. Our findings highlight the lasting importance of biogeographic history on the composition and structure of Andean mountain forests.
The mid-domain effect states that in a spatially bounded domain species richness tends to decrease from the center towards the boundary, thus producing a peak or plateau of species richness in the middle of the domain even in the absence of any environmental gradient. This effect has been frequently used to describe geographic richness gradients of trophically similar species, but how it scales across different trophic levels is poorly understood. Here, we study the role of geometric constraints for the formation of spatial gradients in trophically structured metacommunities. We model colonization–extinction dynamics of a simple food chain on a network of habitat patches embedded in a one- or two-dimensional domain. In a spatially homogeneous or well-mixed system, we find that the food chain length increases with the square root of the ratio of colonization and extinction rates. In a spatially bounded domain, we find that the patch occupancy decreases towards the edge of the domain for all species of the food web, but this spatial gradient varies with the trophic level. As a consequence, the average food chain length peaks in the center and declines towards the boundaries of the domain, thereby extending the notion of a mid-domain effect from species richness to food chain length. This trophic mid-domain effect already arises in a one-dimensional domain, but it is most pronounced at the headlands in a two-dimensional domain. As the mid-domain effect for food chain length is caused solely by spatial boundaries and requires no other environmental heterogeneity, it can be considered a null expectation for geographic patterns in spatially extended food webs.
Correlative species distribution modelling is a widely used method to predict potential species ranges but can suffer from limitations in integrating species’ fundamental niches. Therefore, they might underestimate suitable ranges, but including physiological information can improve accuracy of predictions and help identify mechanisms of e.g. range limitation. However, approaches using both, results from correlative as well as physiological investigations are rare, especially in research on seaweeds. Here, we provide results from both approaches to predict the suitable habitat range of Capreolia implexa (Rhodophyta) in its native range (Australia and New Zealand) and invaded range (Chile) under present and future climate scenarios (year 2100, rcp 2.6 and rcp 8.5). We used the Maxent modelling technique and physiological knowledge from a temperature tolerance experiment (2–20 °C) for thermal niche estimation. Results from both approaches suggest larger suitable habitat ranges under present day conditions for both regions than currently occupied. Abiotic range limitation in the native range led to underestimation of the suitable temperature range by Maxent (here lower temperature limit = 8.3 °C). Predictions based on the laboratory temperature tolerance experiment suggest additional suitable habitat in colder regions (here lower temperature limit = 6.6 ± 0.4 °C). Under future climate conditions, both native and invaded ranges should shift southward, which will lead to an overall loss of suitable habitat in the native range. Like that, rcp 8.5 conditions should reduce the native range to 50% of the present-day extent. We demonstrate the limitation of correlative SDM modelling for species that live on continental margins and that physiological experiments can help to identify species’ niches beyond correlative analyses, providing valuable information for range projections. Furthermore, we provide valuable insights relevant for both invasion management and conservation.
Graphic abstract
Mountains contribute disproportionately to the terrestrial biodiversity of Earth, especially in the tropics, where they host hotspots of extraordinary and puzzling richness. With about 25% of all land area, mountain regions are home to more than 85% of the world’s species of amphibians, birds, and mammals, many entirely restricted to mountains. Biodiversity varies markedly among these regions. Together with the extreme species richness of some tropical mountains, this variation has proven challenging to explain under traditional climatic hypotheses. However, the complex climatic characteristics of rugged mountain regions differ fundamentally from those of lowland regions, likely playing a key role in generating and maintaining diversity. With ongoing global changes in climate and land use, the role of mountains as refugia for biodiversity may well come under threat.
Phenology is a harbinger of climate change, with many species advancing flowering in response to rising temperatures. However, there is tremendous variation among species in phenological response to warming, and any phenological differences between native and non‐native species may influence invasion outcomes under global warming. We simulated global warming in the field and found that non‐native species flowered earlier and were more phenologically plastic to temperature than natives, which did not accelerate flowering in response to warming. Non‐native species' flowering also became more synchronous with other community members under warming. Earlier flowering was associated with greater geographic spread of non‐native species, implicating phenology as a potential trait associated with the successful establishment of non‐native species across large geographic regions. Such phenological differences in both timing and plasticity between native and non‐natives are hypothesised to promote invasion success and population persistence, potentially benefiting non‐native over native species under climate change.
Globally, the allocation of root-shoot biomass is a key plant-adaptive strategy for terrestrial ecosystems to enhance carbon-sequestration capacity. However, the deep mechanisms of above-/below-ground biomass distribution remain unclear, partly due to the multiple influencing factors. We thus aim to clarify the role of various factors in biomass allocation across diverse terrestrial biomes in the paper. A key indicator named root/shoot ratio (RSR) was established, and 7763 observational data-sets were collected from literature, including root biomass, shoot biomass, plant height, climate information and the geographical coordinates. Results highlighted the differences in RSR across terrestrial plants in biomes with a mean value of approximately 0.90. Grasses and boreal forest captured the highest and lowest mean RSR, respectively, while tree had a lower mean RSR than shrub and grass. Angiosperms and deciduous plants, on the other hand, have a higher mean RSR than gymnosperms and evergreen plants, respectively. Moreover, RSR is negatively correlated with mean annual temperature, precipitation, plant height and shoot biomass, but positively correlated with elevation and latitude. Redundancy analysis reflected that biotic and abiotic factors explained RSR variability similarly with a residual of 0.883. These findings support the optimal partitioning hypothesis that plants adjust their growth strategy according to different environments, and in particular, tend to partition more biomass to root systems under more stressful, low-nutrient and poor climatic conditions. Keywords: Biomass allocation, Root, Shoot ratio, Biomes, Environmental adaptation, Plant strategy
It is commonly assumed in trait‐based studies that plant functional traits are species‐specific, being more variable among species than among different environmental conditions. If the environment affects traits, it is assumed that species react in a similar direction and conserve the functional distances. The rank of species based on the trait values is then unchanged, which justifies the use of species trait averages from database values. Such assumptions of species specificity are, however, increasingly disputed by studies showing overall high intraspecific trait variability.
To test the species specificity and ranking stability of functional traits, we sampled plant individuals of almost all species (66 in total) within each plot of a long‐term (19 years) land use management experiment, which comprised a factorial combination of fertilization, mowing and removal of the dominant species Molinia caerulea in an oligotrophic wet meadow in the Czech Republic. Plant individuals were measured for eight commonly used traits: height, leaf dry matter content (LDMC), specific leaf area (SLA), leaf δ¹³C content, leaf carbon content, leaf δ¹⁵N content and leaf nitrogen content. Height, LDMC and SLA were also extracted from the LEDA trait database for comparison.
Species identity consistently explained the largest portion of trait variability (40%‐68%). Land use managements had a considerably lower effect (0.4%–9% of explained trait variability for individual traits). The species trait averages computed for each land use management regime separately were mutually correlated, showing the stable trait‐based species ranking. Ranking stability of species trait averages was observed despite land use management changing absolute trait values and despite the tremendous intraspecific trait variability (causing substantial overlap of trait values for different species). For all treatments, our measured species averages for LDMC and SLA were also stably ranked with species averages from the LEDA database.
Synthesis. Our results showed that species conserve the functional distances in different environmental conditions from where they were measured. Species trait averages can describe general trends in functional composition, although averaging reduces the ecologically interesting information of the intraspecific trait variability.
A plain language summary is available for this article.
Native and invasive populations might behave differentially due to contrasting genetics and histories of environmental pressures. Here we attempted to understand how climate warming and atmospheric nitrogen (N) deposition influence native and invasive populations, and thus conducted an experiment to address their effects on the nine invasiveness-related traits (leaf dry matter content, specific leaf area, leaf lifespan, ramet height, ramet number, the first inflorescence buds, the first flowering, the first seed-setting, and the first dieback) of Solidago canadensis populations from the USA and China. Solidago canadensis from the USA had shorter leaf lifespan and ramet height, smaller ramet number, and earlier phenology than that from China. Warming and N addition extended leaf lifespan but failed to influence leaf dry matter content and specific leaf area; warming decreased ramet height and delayed the onset of inflorescence and flowering but N addition increased ramet height and advanced the onset of inflorescence and flowering. Six traits were more sensitive to warming or N addition in the native population than in the invasive population, and the other traits were similar; warming and N addition together had stronger effects on six traits of the native population than those of the invasive population, and the opposite was true for ramet height. Our results suggest that climate warming and N deposition might promote S. canadensis invasion, as indicated by enhanced growth, and could influence its native populations to a greater extent than its invasive populations.
Invasive alien plants (IAP) are a threat to biodiversity worldwide. Understanding and anticipating invasions allow for more efficient management. In this regard, predicting potential invasion risks by IAPs is essential to support conservation planning into areas of high conservation value (AHCV) such as sites exhibiting exceptional botanical richness, assemblage of rare, and threatened and/or endemic plant species. Here, we identified AHCV in Georgia, a country showing high plant richness, and assessed the susceptibility of these areas to colonization by IAPs under present and future climatic conditions. We used actual protected areas and areas of high plant endemism (identified using occurrences of 114 Georgian endemic plant species) as proxies for AHCV. Then, we assessed present and future potential distribution of 27 IAPs using species distribution models under four climate change scenarios and stacked single‐species potential distribution into a consensus map representing IAPs richness. We evaluated present and future invasion risks in AHCV using IAPs richness as a metric of susceptibility. We show that the actual protected areas cover only 9.4% of the areas of high plant endemism in Georgia. IAPs are presently located at lower elevations around the large urban centers and in western Georgia. We predict a shift of IAPs toward eastern Georgia and higher altitudes and an increased susceptibility of AHCV to IAPs under future climate change. Our study provides a good baseline for decision makers and stakeholders on where and how resources should be invested in the most efficient way to protect Georgia's high plant richness from IAPs.
Aim
We investigated patterns of species richness and community dissimilarity along elevation gradients using globally replicated, standardized surveys of vascular plants. We asked how these patterns of diversity are influenced by anthropogenic pressures (road construction and non‐native species).
Location
Global.
Time period
2008–2015.
Major taxa studied
Vascular plants.
Methods
Native and non‐native vascular plant species were recorded in 943 plots along 25 elevation gradients, in nine mountain regions, on four continents. Sampling took place in plots along and away from roads. We analysed the effects of elevation and distance from road on species richness patterns and community dissimilarity (beta‐diversity), and assessed how non‐native species modified such elevational diversity patterns.
Results
Globally, native and total species richness showed a unimodal relationship with elevation that peaked at lower‐mid elevations, but these patterns were altered along roads and due to non‐native species. Differences in elevational species richness patterns between regions disappeared along roadsides, and non‐native species changed the patterns’ character in all study regions. Community dissimilarity was reduced along roadsides and through non‐native species. We also found a significant elevational decay of beta‐diversity, which however was not affected by roads or non‐native species.
Main conclusions
Idiosyncratic native species richness patterns in plots away from roads implicate region‐specific mechanisms underlying these patterns. However, along roadsides a clearer elevational signal emerged and species richness mostly peaked at mid‐elevations. We conclude that both roads and non‐native species lead to a homogenization of species richness patterns and plant communities in mountains.
Aim
Much is known about the elevational diversity patterns of native species and about the mechanisms that drive these patterns. A similar level of understanding is needed for non‐native species. Using published data, we examine elevational diversity patterns of non‐native plants and compare the resulting patterns with those observed for native plants.
Location
Global.
Methods
We compiled data from 65 case studies on elevational diversity patterns of non‐native plants around the world (including 32 cases in which both non‐native and native plants were sampled). We compared the elevational distributions (upper and lower limits, and extents) and diversity patterns of non‐native and native species.
Results
Compared to native plant species, the elevational diversity patterns of non‐native plant species were more negative (47% vs. 13%) and less unimodal (44% vs. 84%). That is, non‐native species richness tended to be highest at lower elevations, whereas native species richness peaked at mid‐elevations. In cases where species richness for both non‐native and native species on the same mountains showed unimodal patterns in relation to elevation, maximum values in species richness occurred at lower elevations for non‐native species.
Main conclusions
At present levels of invasion, non‐native and native species show different patterns in both distribution and diversity along elevational gradients worldwide. However, our observations constitute a snapshot of ongoing, long‐term invasion processes. As non‐native species typically show strong associations with human activities, future changes in human population (e.g. growth and migration), land use and climate change may promote upward spread of non‐native species and may thus increase risks of impact on native species and communities.
Our ability to model global carbon fluxes depends on understanding how terrestrial carbon stocks respond to varying environmental conditions. Tropical forests contain the bulk of the biosphere's carbon. However, there is a lack of consensus as to how gradients in environmental conditions affect tropical forest carbon. Papua New Guinea (PNG) lies within one of the largest areas of contiguous tropical forest and is characterized by environmental gradients driven by altitude; yet, the region has been grossly understudied. Here, we present the first field assessment of aboveground biomass (AGB) across three main forest types of PNG using 193 plots stratified across 3,100-m elevation gradient. Unexpectedly, AGB had no direct relationship to rainfall, temperature, soil, or topography. Instead, natural disturbances explained most variation in AGB. While large trees (diameter at breast height > 50 cm) drove altitudinal patterns of AGB, resulting in a major peak in AGB (2,200-3,100 m) and some of the most carbon-rich forests at these altitudes anywhere. Large trees were correlated to a set of climatic variables following a hump-shaped curve. The set of "optimal" climatic conditions found in montane cloud forests is similar to that of maritime temperate areas that harbor the largest trees in the world: high ratio of precipitation to evapotranspiration (2.8), moderate mean annual temperature (13.7°C), and low intra-annual temperature range (7.5°C). At extreme altitudes (2,800-3,100 m), where tree diversity elsewhere is usually low and large trees are generally rare or absent, specimens from 18 families had girths >70 cm diameter and maximum heights 20-41 m. These findings indicate that simple AGB-climate-edaphic models may not be suitable for estimating carbon storage in forests where optimal climate niches exist. Our study, conducted in a very remote area, suggests that tropical montane forests may contain greater AGB than previously thought and the importance of securing their future under a changing climate is therefore enhanced.
The factors determining gradients of biodiversity are a fundamental yet unresolved topic in ecology. While diversity gradients have been analysed for numerous single taxa, progress towards general explanatory models has been hampered by limitations in the phylogenetic coverage of past studies. By parallel sampling of 25 major plant and animal taxa along a 3.7 km elevational gradient on Mt. Kilimanjaro, we quantify cross-taxon consensus in diversity gradients and evaluate predictors of diversity from single taxa to a multi-taxa community level. While single taxa show complex distribution patterns and respond to different environmental factors, scaling up diversity to the community level leads to an unambiguous support for temperature as the main predictor of species richness in both plants and animals. Our findings illuminate the influence of taxonomic coverage for models of diversity gradients and point to the importance of temperature for diversification and species coexistence in plant and animal communities.
Invasive alien plant species threaten native biodiversity, disrupt ecosystem functions, and can cause large economic damage. Plant invasions have been predicted to further increase under ongoing global environmental change. Numerous case studies have compared the performance of invasive and native plant species in response to global environmental change components (i.e. changes in mean levels of precipitation, temperature, atmospheric CO2 concentration or nitrogen deposition). Individually these studies usually involve low numbers of species and therefore the results cannot be generalized. Therefore, we performed a phylogenetically-controlled meta-analysis to assess whether there is a general pattern of differences in invasive and native plant performance under each component of global environmental change. We compiled a database of studies that reported performance measures for 74 invasive alien plant species and 117 native plant species in response to one of four global environmental change components. We found that elevated temperature and CO2 enrichment increased performance of invasive alien plants more strongly than was the case for native plants. Invasive alien plants tended to also have a slightly stronger positive response to increased N deposition and increased precipitation than native plants, but these differences were not significant (N deposition: P = 0.051; increased precipitation: P = 0.679). Invasive alien plants tended to have a slightly stronger negative response to decreased precipitation than native plants, although this difference was also not significant (P = 0.060). So while drought could potentially reduce invasion, increases in the four other components of global environmental change considered, particularly global warming and atmospheric CO2 enrichment, may further increase the spread of invasive plants in the future. This article is protected by copyright. All rights reserved.
Recent years have seen a surge of interest in understanding patterns and processes of plant invasions into mountains. Here, we synthesise current knowledge about the spread of non-native plants along elevation gradients, emphasising the current status and impacts that these species have in alpine ecosystems. Globally, invasions along elevation gradients are influenced by propagule availability, environmental constraints on population growth, evolutionary change and biotic interactions. The highest elevations are so far relatively free from non-native plants. Nonetheless, in total nearly 200 non-native plant species have been recorded from alpine environments around the world. However, we identified only three species as specifically cold-adapted, with the overwhelming majority having their centres of distribution under warmer environments, and few have substantial impacts on native communities. A combination of low propagule availability and low invasibility likely explain why alpine environments host few non-native plants relative to lowland ecosystems. However, experiences in some areas demonstrate that alpine ecosystems are not inherently resistant to invasions. Furthermore, they will face increasing pressure from the introduction of pre-adapted species, climate change, and the range expansion of native species, which are already causing concern in some areas. Nonetheless, because they are still relatively free from non-native plants, preventative action could be an effective way to limit future impacts of invasions in alpine environments.
The introduction and success of non‐native species are both a consequence and a cause of rapid global change. Humans have created novel ecosystems through environmental modification and mass movements of organisms around the planet.
It has been argued that species biogeographic origin cannot explain or predict ecological impacts and the origin of a species should not influence ecosystem management. This rejection of ‘origin’ is overly simplistic. Origin effects can arise through biased sampling of the types of species transported, the environmental and evolutionary context of their source environments and the communities and environments to which they are introduced. Differences in co‐evolutionary histories between source and recipient environments, and adaptation of introduced species to modified environmental conditions, can also shape origin effects.
The high rates and long distances of human‐mediated dispersal have increased the sizes of regional species pools. In addition, human transported, non‐native species can change the function of recipient ecosystems through changes to community composition. We outline how origin effects can cascade through to ecological impact at population, community and ecosystem levels.
Synthesis . Non‐native species can have predictable and preventable effects on recipient communities. We identify multiple sources of origin effects and describe the ecological and evolutionary pathways through which origin effects lead to impacts. This functional understanding of origin effects must include human actions. However, species origin should not, on its own, be used as a shortcut for management decisions; origin effects should instead feed into a process whereby ecologists work together with managers, policymakers and broader society to guide decisions on how to respond to the effects of non‐native species.
This article describes a R package Boruta, implementing a novel feature selection algorithm for finding all relevant variables. The algorithm is designed as a wrapper around a Random Forest classification algorithm. It iteratively removes the features which are proved by a statistical test to be less relevant than random probes. The Boruta package provides a convenient interface to the algorithm. The short description of the algorithm and examples of its application are presented.
Significance
Do forests in cold or dry climate zones distribute more resources in roots to enhance uptake of water and nutrients, which are scarce in such climates? Despite its importance to forest ecology and global carbon cycle modeling, this question is unanswered at present. To answer this question, we compiled and analyzed a large dataset (>6,200 forests, 61 countries) and determined that the proportion of total forest biomass in roots is greater and in foliage is smaller in increasingly cold climates. Surprisingly, allocation to roots or foliage was unrelated to aridity. These findings allow, for the first time to our knowledge, biogeographically explicit mapping of global root carbon pools, which will be useful for assessing climate change impacts on forest carbon dynamics and sequestration.
Nonnative species richness typically declines along environmental gradients such as elevation. It is usually assumed that this is because few invaders possess the necessary adaptations to succeed under extreme environmental conditions. Here, we show that nonnative plants reaching high elevations around the world are not highly specialized stress tolerators but species with broad climatic tolerances capable of growing across a wide elevational range. These results contrast with patterns for native species, and they can be explained by the unidirectional expansion of nonnative species from anthropogenic sources at low elevations and the progressive dropping out of species with narrow elevational amplitudes—a process that we call directional ecological filtering. Independent data confirm that climatic generalists have succeeded in colonizing the more extreme environments at higher elevations. These results suggest that invasion resistance is not conferred by extreme conditions at a particular site but determined by pathways of introduction of nonnative species. In the future, increased direct introduction of nonnative species with specialized ecophysiological adaptations to mountain environments could increase the risk of invasion. As well as providing a general explanation for gradients of nonnative species richness and the importance of traits such as phenotypic plasticity for many invasive species, the concept of directional ecological filtering is useful for understanding the initial assembly of some native floras at high elevations and latitudes.
Mid-domain effect (MDE) models predict that the random placement of species' ranges within a bounded geographical area leads to increased range overlap and species richness in the center of the bounded area. These models are frequently applied to study species-richness patterns of macroorganisms, but the MDE in relation to microorganisms is poorly understood. In this study, we examined the characteristics of the MDE in richness patterns of ectomycorrhizal (EM) fungi, an ecologically important group of soil symbionts. We conducted intensive soil sampling to investigate overlap among species ranges and the applicability of the MDE to EM fungi in four temperate forest stands along an elevation gradient on Mount Fuji, Japan. Molecular analyses using direct sequencing revealed 302 EM fungal species. Of 73 EM fungal species found in multiple stands, 72 inhabited a continuous range along the elevation gradient. The maximum overlap in species range and the highest species richness occurred at elevations in the middle of the gradient. The observed richness pattern also fit within the 95% confidence interval of the mid-domain null model, supporting the role of the MDE in EM fungal richness. Deviation in observed richness from the mean of the mid-domain null estimation was negatively correlated with some environmental factors, including precipitation and soil C/N, indicating that unexplained richness patterns could be driven by these environmental factors. Our results clearly support the existence of microbial species' ranges along environmental gradients and the potential applicability of the MDE to better understand microbial diversity patterns.The ISME Journal advance online publication, 13 March 2014; doi:10.1038/ismej.2014.34.
During the growing seasons of 2002 and 2003, biomass productivity and diversity were examined along an altitudinal transect on the south-western slope of Beishan Mountain, Maqin County (33°43′–35°16′N, 98°48′–100°55′E), Qinghai–Tibetan Plateau. Six altitudes were selected, between 3840 and 4435 m. Soil organic matter, soil available N and P and environmental factors significantly affected plant-species diversity and productivity of the alpine meadows. Aboveground biomass declined significantly with increasing altitude (P < 0.05) and it was positively and linearly related to late summer soil-surface temperature. Belowground biomass (0–10-cm depth) was significantly greater at the lowest and highest altitudes than at intermediate locations, associated with water and nutrient availabilities. At each site, the maximum belowground biomass values occurred at the beginning and the end of the growing seasons (P < 0.05). Soil organic matter content, and available N and P were negatively and closely related to plant diversity (species richness, Shannon–Wiener diversity index, and Pielou evenness index).
It is often claimed that we do not understand the forces driving the global diversity gradient. However, an extensive literature suggests that contemporary climate constrains terrestrial taxonomic richness over broad geographic extents. Here, we review the empirical literature to examine the nature and form of the relationship between climate and richness. Our goals were to document the support for the climatically based energy hypothesis, and within the constraints imposed by correlative analyses, to evaluate two versions of the hypothesis: the productivity and ambient energy hypotheses. Focusing on studies extending over 800 km, we found that measures of energy, water, or water-energy balance explain spatial variation in richness better than other climatic and non-climatic variables in 82 of 85 cases. Even when considered individually and in isolation, water/ energy variables explain on average over 60% of the variation in the richness of a wide range of plant and animal groups. Further, water variables usually represent the strongest predictors in the tropics, subtropics, and warm temperate zones, whereas energy variables (for animals) or water-energy variables (for plants) dominate in high latitudes. We conclude that the interaction between water and energy, either directly or indirectly (via plant pro- ductivity), provides a strong explanation for globally extensive plant and animal diversity gradients, but for animals there also is a latitudinal shift in the relative importance of ambient energy vs. water moving from the poles to the equator. Although contemporary climate is not the only factor influencing species richness and may not explain the diversity pattern for all taxonomic groups, it is clear that understanding water-energy dynamics is critical to future biodiversity research. Analyses that do not include water-energy variables are missing a key component for explaining broad-scale patterns of diversity.
Aim We use data from 13 mountain regions and surrounding lowland areas to identify (1) the origins, traits and cultural uses of alien plant species that establish in mountains, (2) the alien species that are most likely to be a threat and (3) how managers might use this information to prevent further invasions.
Location Australia, Canada, Chile, India, New Zealand, South Africa, Spain, Switzerland, USA.
Methods Lists of alien species were compiled for mountains and their surrounding or nearby lowlands. Principal co-ordinates analysis was performed on a matrix of similarities created using presence/absence data for alien species. The significance of differences between means for (1) similarity metrics of lowland and mountain groups and (2) species traits of lowland and mountain alien floras was determined using t-tests. In seven of the 13 mountain regions, lists of alien species undergoing management were compiled. The significance of differences between proportions of traits for species requiring and not requiring management input was determined with chi-square tests.
Results We found that the proximal lowland alien flora is the main determinant of a mountain region’s alien species composition. The highest similarities between mountain floras were in the Americas/Pacific Region. The majority of alien species commonly found in mountains have agricultural origins and are of little concern to land managers. Woody species and those used for ornamental purposes will often pose the greatest threat.
Main conclusions Given the documented potential threat of alien species invading mountains, we advise natural resource managers to take preventive measures against the risk of alien plant invasion in mountains. A strategy for prevention should extend to the surrounding lowland areas and in particular regulate the introduction of species that are already of management concern in other mountains as well as climatically pre-adapted alien mountain plants. These may well become more problematic than the majority of alien plants currently in mountains.
The timing of flowering is an important driver of species distribution and community assembly patterns. However, we still have much to learn about the factors that shape flowering diversity (i.e., number of species flowering per period) in plant communities. One potential explanation of flowering diversity is the mid-domain effect, which states that geometric constraints on species ranges within a bounded domain (space or time) will yield a mid-domain peak in diversity regardless of ecological factors. Here, we determine whether the mid-domain effect explains peak flowering time (i.e., when most species of communities are flowering) across China. We used phenological data of 16,267 herbaceous and woody species from the provincial Flora in China and species distribution data from the Chinese Vascular Plant Distribution Database to determine relationships between the observed number of species flowering and the number of species flowering as predicted by the mid-domain effect model, as well as between three climatic variables (mean minimum monthly temperature, mean monthly precipitation, and mean monthly sunshine duration). We found that the mid-domain effect explained a significant proportion of the temporal variation in flowering diversity across all species in China. Further, the mid-domain effect explained a greater proportion of variance in flowering diversity at higher latitudes than at lower latitudes. The patterns of flowering diversity for both herbaceous and woody species were related to both the mid-domain effect and environmental variables. Our findings indicate that including geometric constraints in conjunction with abiotic and biotic predictors will improve predictions of flowering diversity patterns.
Plant invasions, a byproduct of globalization, are increasing worldwide. Because of their ecological and economic impacts, considerable efforts have been made to understand and predict the success of non-native plants. Numerous frameworks, hypotheses, and theories have been advanced to conceptualize the interactions of multiple drivers and context dependence of invasion success with the aim of achieving robust explanations with predictive power. We review these efforts from a community-level perspective rather than a biogeographical one, focusing on terrestrial systems, and explore the roles of intrinsic plant properties in determining species invasiveness, as well as the effects of biotic and abiotic conditions in mediating ecosystem invasibility (or resistance) and ecological and evolutionary processes. We also consider the fundamental influences of human-induced changes at scales ranging from local to global in triggering, promoting, and sustaining plant invasions and discuss how these changes could alter future invasion trajectories.
Expected final online publication date for the Annual Review of Plant Biology, Volume 74 is May 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Healthy plants host diverse but taxonomically structured communities of microorganisms, the plant microbiota, that colonize every accessible plant tissue. Plant-associated microbiomes confer fitness advantages to the plant host, including growth promotion, nutrient uptake, stress tolerance and resistance to pathogens. In this Review, we explore how plant microbiome research has unravelled the complex network of genetic, biochemical, physical and metabolic interactions among the plant, the associated microbial communities and the environment. We also discuss how those interactions shape the assembly of plant-associated microbiomes and modulate their beneficial traits, such as nutrient acquisition and plant health, in addition to highlighting knowledge gaps and future directions. In this Review, Trivedi and colleagues explore the interactions between plants, their associated microbial communities and the environment, and also discuss how those interactions shape the assembly of plant-associated microbiomes and modulate their beneficial traits.
Distribution of biodiversity along the elevation gradient has been a subject of curiosity and a much argued topic in macroecology. Despite considerable attention, there is a lack of consensus on the pattern and the causal factors across regions and taxa. We studied amphibian distribution along the elevational gradient in Sikkim, Eastern Himalaya, part of a globally significant biodiversity hotspot. We conducted intensive field studies covering 300-4600 m elevation using Visual Encounter Survey and Night Stream Survey methods. We examined the effects of both spatial factors (area and mid-domain effect) and environmental variables (temperature, precipitation, moisture, potential evapotranspiration and actual evapotranspiration) on the distribution of amphibians along the elevational gradient. We recorded 25 species and 1368 individuals of amphibians after 1236 man-hours of visual encounter survey and 27 km night stream survey. Species richness of total amphibians and their sub groups (endemic, non-endemic, large-range and small-range) followed unimodal pattern showing a peak at middle elevation but with slight shift towards higher elevation for endemic species. Various environmental variables, especially actual evapotranspiration and mean annual precipitation, explained the elevational distribution trend of amphibians in the Eastern Himalaya. Spatial factors played no significant role in shaping the pattern of amphibian distribution (except endemics and large- range species showing fit to mid-domain effect). Local communities of the study area extract amphibians for food and medicine, especially from the diverse mid elevation zone, which should be closely monitored and curbed by the wildlife authorities.
Climate change is expected to trigger an upward expansion of plants in mountain regions and, although there is strong evidence that many native species have already shifted their distributions to higher elevations,, little is known regarding how fast non-native species might respond to climate change. By analysing 131,394 occurrence records of 1,334 plant species collected over 20 years in the European Alps, we found that non-natives are spreading upwards approximately twice as fast as natives. Whereas the spread of natives was enhanced by traits favouring longer dispersal distances, this was not the case for non-natives. This was due to the non-native species pool already being strongly biased towards species that had traits facilitating spread. A large proportion of native and non-native species seemed to be able to spread upwards faster than the current velocity of climate change. In particular, long-distance dispersal events and proximity to roads proved to be key drivers for the observed rapid spread. Our findings highlight that invasions by non-native species into native alpine communities are a potentially significant additional pressure on these vulnerable ecosystems that are already likely to suffer dramatic vegetation changes with ongoing warming and increasing human activity in mountain regions.
Monitoring the elevation limits of non-native species is a potentially sensitive means of detecting effects of environmental change on invasion dynamics and species ranges. The aim of this study was to investigate temporal changes in the distribution of non-native plant species along elevation gradients in the Swiss Alps by repeating, in 2009, a regional survey from 2003 of 230 sites ranging in elevation from 200 to 2400 m a.s.l. We also studied the fine-scale spatiotemporal population structure of two of the non-native species − Erigeron annuus and Solidago canadensis − along an elevation gradient in a heterogeneous landscape.
To understand the spatiotemporal expansion pattern of invasive species is of significance for the control of alien species invasion and spread. The aim of this research is to reconstruct the invasion and expansion processes and to predict the potential spread of Erigeron annuus, one of the threatening invasive plant species in China, and to identify and determine the possible modes of this species early introduction, subsequent expansion route, and potential spread. The reconstruction of the historical invasion processes of E. annuus in China showed that E. annuus first invaded Shanghai in 1886. After a lag phase of 50 years (1880s-1930s), this species expanded its distribution from China eastern coastal area toward inland, and until 2000, invaded 21 provinces. E. annuus would continue its expansion in China. Most areas in China, except Qinghai, Tibet, Inner Mongolia, Guangdong, Guangxi, and Heilongjiang, are likely to be invaded, and their adjacent areas, e. g., southern Hebei, northern Henan, Shanxi, Shaanxi, western-central Liaoning, and western Jilin, are most liable to be invaded, where urgent measures should be adopted to prevent further invasion of this species.
We studied the altitudinal patterns of plant species richness and examined the effects of geometric constraints, area, and climatic factors on the observed richness patterns along the ridge of the Baekdudaegan Mountains, South Korea. Rapoport's altitudinal rule was evaluated by examining the relationship between altitudinal range size and midpoint. We also examined the latitudinal effect on species richness. Plant data were collected from 1,100 plots along a 200-1,900 m altitudinal gradient along the ridge of the Baekdudaegan. A total of 802 plant species from 97 families and 342 genera were found. The altitudinal patterns of plant species richness along the ridge of the Baekdudaegan depicted distinctly hump-shaped patterns, although the absolute altitudes of the richness peaks vary somewhat among plant groups. While the mid-domain effect (MDE) was the most powerful explanatory variable in simple regression models, species richness was also associated with climatic factors, especially mean annual precipitation (MAP) and temperature (MAT) in multiple regression models. The relative importance of the MDE and climatic factors were different among plant groups. The MDE was more important for woody plants and for large-ranged species, whereas climatic factors were better predictors for total and herbaceous plants and for small-ranged species. Rapoport's altitudinal rule and a latitudinal effect on species richness were not supported. Our study suggests that a combined interaction of the MDE and climatic factors influences species richness patterns along the altitudinal gradient of the Baekdudaegan Mountains, South Korea.
Understanding the relationship between photosynthesis, net primary productivity and growth in forest ecosystems is key to understanding how these ecosystems will respond to global anthropogenic change, yet the linkages among these components are rarely explored in detail. We provide the first comprehensive description of the productivity, respiration and carbon allocation of contrasting lowland Amazonian forests spanning gradients in seasonal water deficit and soil fertility. Using the largest dataset assembled to date, ten sites in three countries all studied with a standardized methodology, we find that (i) gross primary productivity (GPP) has a simple relationship with seasonal water deficit, but that (ii) site-to-site variations in GPP have little power in explaining site-to-site spatial variations in net primary productivity (NPP) or growth because of concomitant changes in carbon use efficiency (CUE), and conversely, the woody growth rate of a tropical forest is a very poor proxy for its productivity. Instead, (iii) spatial patterns of biomass are much more driven by patterns of residence times (i.e. tree mortality rates) than by spatial variation in productivity or tree growth. Current theory and models of tropical forest carbon cycling under projected scenarios of global atmospheric change can benefit from advancing beyond a focus on GPP. By improving our understanding of poorly understood processes such as CUE, NPP allocation and biomass turnover times, we can provide more complete and mechanistic approaches to linking climate and tropical forest carbon cycling. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Geographic patterns of species richness are influenced by many factors, but the role of shared physiographical and physiological boundaries in relation to range-size
distributions has been surprisingly neglected, in spite of the fact that such geometric
constraints lead to mid-domain richness peaks even without environmental
gradients (the mid-domain effect). Relying on null models, several recent studies
have begun to quantify this problem using simulated and empirical data. This
approach promises to transform how we perceive geographic variation in diversity,
including the long unresolved latitudinal gradient in species richness. The question is
not whether geometry affects such patterns, but by how much.
Plant roots play diverse roles in the rhizosphere. They function as organs responsible for structural support, for acquisition of mineral and water resources, and for fostering of symbiotic bacteria and fungi. They also sustain a complex food web of pro-karyotes and eukaryotes in, on, and near the root. In addition to these well-known functions, roots have a recently discovered role with potentially profound coevolutionary implications for the rhizosphere food web, as well as for terrestrial ecological communities in general. Roots are both a source and a receptor of molecular signals important for mutualistic bacteria and perhaps other soil organisms. Fluid-borne rhizosphere compounds flow in the opposite direction from airborne signals that emanate from plant shoots. The powerful transpiration stream around roots naturally concentrates molecular data in a cafeteria of information about the surrounding soil. These molecular signals, such as N-acylated homoserine lactones and phenazines produced by bacteria, can be interpreted simultaneously by multiple species as well as by the root. We propose a model of multitrophic molecular signals in the rhi-zosphere that implies multiple roles of roots, as hosts, regulators, and sustainers of terrestrial productivity. We suggest a framework of regulation in the rhizosphere that functions through molecular ''control points.'' We define control points as regulatory elements that are op-erated on by selection processes to confer fitness on individual organisms and thereby have effects that propagate through other trophic levels. Identification of a control point creates a hypothesis that can be tested to assess the quantitative significance of that regulatory element. Some control points may transmit or perceive signals between organisms, but others probably integrate changing environmental conditions or external resources into individual life histories and community functions. The promise of understanding the new molecular signals is that genes must closely underlie these control points. This could offer ecology access to the power of molecular biology and allow a deep understanding of the evolutionary significance of these phenomena. One major strength of rhizospheres for addressing these issues is that realistic ecological interactions can be examined in a restricted microcosm under environmentally controlled conditions with organisms whose genomes have been completely defined and/or partially modified.